Received-signal processing method and received-signal processing apparatus for electromagnetic wave probe

Technical Field The present invention relates to a received signal processing method and a received signal processing device of an electromagnetic wave probe, and is particularly characterized by compensating for distance fluctuations between an antenna and an exploration target such as the ground surface during measurement of a portable electromagnetic wave probe. Regarding those who have. Background Technology Conventionally, electromagnetic wave probes have been developed in which electromagnetic waves are radiated from an antenna and reflected waves from an object are received and analyzed for exploration. This spacecraft is used for the purpose of exploring buried objects such as land mines. This electromagnetic wave probe finds the distance to an object based on the time required from radiating an electromagnetic wave to receiving a reflected wave. Recently, the development of portable and portable electromagnetic wave probes has been promoted, and these small electromagnetic wave probes are widely used for various purposes regardless of whether they are for industrial use or consumer use. Portable and portable spacecraft are lightweight and easy to handle. However, it was difficult to keep the distance between the antenna of the spacecraft and the ground surface constant, and due to this distance fluctuation, extremely complicated exploration images were generated, and it was difficult to analyze the exploration results. FIG. 26 shows the received signal E captured by the antenna 201 when the distance between the antenna 201 (integrated transmission / reception type) of the spacecraft 200 and the ground surface G fluctuates.₀, E₁The change of is shown using the amplitude axis (horizontal axis) and the time axis (vertical axis), and the depth direction of the ground is superimposed on the time axis and displayed schematically. As shown in FIG. 26, when the distance between the antenna 201 and the ground surface G fluctuates from d1 on the left side of the figure to d2 on the right side of the figure due to the fluctuation of the holding height of the spacecraft 200 by the operator, the antenna 201 starts to move. The inrush phase of the radiated electromagnetic wave into the ground surface G fluctuates. Relative permittivity ε_rWhen propagating in the medium of the atmosphere (ε)_rIt is known as a basic characteristic of electromagnetic waves that the propagation speed is lowered and the wavelength is shortened as compared with the case of propagating = 1). The attenuation rate of electromagnetic waves is the relative permittivity ε of the propagation medium._rAnd the higher the resistivity ρ, the larger it becomes. Therefore, the reflected waves of the electromagnetic waves before and after the above distance fluctuation are captured by the antenna 201, and these received signals E₀When, E are superimposed, the received signal E is shown in FIG. 27.₀Phase difference φ between and E₀And the amplitude difference, and the reflected wave RT by the object Q₀There was also a phase difference between RT. Such a phase difference and an amplitude difference can be substantially ignored when one waveform of the sequentially received received signals is updated and displayed each time the reception signal is received. That is, the time required for an electromagnetic wave to propagate in the air by 10 cm is about 0.33 nsec. Therefore, a screen (embedded in a medium with a relative permittivity of 12) in which the received waveform is used as a frequency variable and the maximum display depth when the maximum value on the time axis is 5 msec and the relative permittivity of the medium is 12 is set to 1.5 m. When the reflected wave of an object with a depth of 1.5 m is displayed at (5 msec), the time corresponding to the distance fluctuation of 10 cm is only 0.33 msec (ratio to the entire time axis: 6. 6%), and the distortion of the received waveform due to distance fluctuation is slight. However, as shown in FIG. 28, when a cross-sectional image showing the depth on the vertical axis and the number of scans (scanning distance) on the horizontal axis is displayed, a phase shift is accumulated for each received waveform as the distance fluctuates. Although it is originally a linear buried object Q, a complicated cross-sectional image deformed up and down is displayed. Therefore, in order to accurately measure the shape and depth of the buried object, it is necessary to carry out the exploration while keeping the distance between the antenna and the exploration target as constant as possible, and the skill of the explorer hinders the accuracy of the exploration. It was a big factor to do. The permittivity (relative permittivity) of the medium in the ground is larger than that of the atmosphere, and the attenuation rate of electromagnetic waves in the ground is also much larger than that in the atmosphere. Therefore, compared to the case where the electromagnetic wave propagates in the atmosphere, the electromagnetic wave propagating in the ground is strongly attenuated and the propagation speed is also lowered. That is, when an electromagnetic wave having the same radiant power enters the ground from the atmosphere, a phase shift or an amplitude difference occurs between the electromagnetic wave having a long atmospheric passage distance and the electromagnetic wave having a short atmospheric passage distance. This also applies to electromagnetic wave probes that radiate electromagnetic waves for exploration. If the distance between the antenna and the ground surface fluctuates during exploration, the electromagnetic waves radiated at regular intervals may shift in phase. Amplitude difference will occur, which is a factor that hinders accurate measurement. The present inventors measured and analyzed the occurrence of phase shift and amplitude difference of electromagnetic waves caused by distance fluctuation, and found that the phase shift and amplitude difference of electromagnetic waves that rushed into the ground with distance fluctuation were found. Although it occurs, it was found that it propagates inside the ground while showing almost the same attenuation rate at almost the same frequency (period). In addition, the present inventors have found by measurement that the received signal of the reflected wave of this electromagnetic wave also has the same property. Therefore, a method of correcting the phase shift between the received signals described above, a method of correcting the amplitude difference between the phase-corrected received signals, and a method of extracting the difference signal component between the amplitude-corrected received signals are examined. , It was confirmed that stable measurement can be performed by compensating for the distance fluctuation by using these methods alone or in combination as appropriate. Made based on this finding An object of the present invention is to enable stable and precise exploration measurement even when the distance between the antenna of the spacecraft and the exploration target fluctuates. Disclosure of the Invention The present invention is an electromagnetic wave probe that holds a plurality of received signals having different exploration positions and analyzes the plurality of received signals to perform non-destructive exploration of the exploration target. In a reception signal processing method of an electromagnetic wave probe including a reception antenna that receives a reflected wave of an electromagnetic wave radiated from the antenna and a reception unit that generates the reception signal based on the detection signal of the reception antenna, each received signal It is characterized by having a step of performing phase correction for each received signal starting from a predetermined peak point. According to this, it is possible to remove the phase shift between a plurality of received signals caused by the fluctuation of the distance between the antenna and the search target, and even a portable electromagnetic wave probe can be accurate without requiring skill. It is possible to perform various exploration measurements. The received signal processing method of the present invention further compares the amplitudes of a plurality of received signals at the starting point of phase correction, and sets a first amplitude correction coefficient given as a constant according to the ratio of the amplitudes to a predetermined received signal. It can have a step of calculation. According to this, even if there is an amplitude difference in each received signal due to the change in the inrush phase of the radiated electromagnetic wave into the search target due to the change in the distance between the antenna and the search target, the amplitude difference is caused by the above-mentioned amplitude correction step. Can be compensated. Further, the method of the present invention can include a step of calculating a second amplitude correction coefficient given as a function of time with respect to the predetermined received signal to which the phase correction has been performed. According to this, the optimum amplitude correction can be performed for each phase (time) of the received signal. For example, the phase of the received signal corresponds to the depth of the exploration target, and the attenuation rate of the electromagnetic wave propagating in the exploration target is almost constant regardless of the amplitude when the electromagnetic wave enters the exploration target surface. By assigning a function corresponding to the inverse of the attenuation rate as the second coefficient, the signal level at a deep location can be amplified to facilitate discrimination and analysis. Preferably, In the method of the present invention, a first amplitude correction coefficient given as a constant corresponding to the ratio of the amplitudes of a plurality of received signals at the starting point of phase correction and a second amplitude correction coefficient given as a function of time are predetermined. It can have a step of calculating the received signal. The calculation with the second amplitude correction coefficient is preferably performed after a predetermined phase of the received signal, and more preferably after the starting point of the phase correction. According to this, before the predetermined phase (starting point of phase correction), the amplitude correction by the second amplitude correction coefficient is not performed, and the amplitude fluctuation is intentionally left, so that the lift amount of the electromagnetic wave probe is increased. The change in the above-mentioned amplitude can be made to be recognized by the operator, and the fluctuation of the amplitude can be used as a guideline for the exploration operator to stabilize the fluctuation of the lift amount. Further, the method of the present invention can further include a step of extracting a difference signal component between the received signals to which the amplitude correction has been performed. According to this, even when the difference processing between the received signals before and after the change in the lift amount of the spacecraft is performed, the phase compensation and the amplitude compensation are performed before the difference processing. Changes in the structure in the target can be extracted as a difference signal component with a high SN ratio, and by using a plurality of difference signals for each exploration position, non-destructive exploration can be easily performed even by non-skilled engineers. .. Further, the present invention is an electromagnetic wave probe that holds a plurality of received signals having different exploration positions and analyzes the plurality of received signals to perform non-destructive exploration of the exploration target, the transmitting antenna and the transmitting antenna. In the reception signal processing device of the electromagnetic wave probe including the reception antenna that receives the reflected wave of the electromagnetic wave radiated from the electromagnetic wave and the reception unit that generates the reception signal based on the detection signal of the reception antenna, a predetermined value of each reception signal is provided. It is characterized by providing a phase correction means for performing phase correction on each received signal starting from the peak point of. The received signal processing device of the present invention may further include a predetermined amplitude correction means. This amplitude correction means compares the amplitudes of a plurality of received signals at the starting point of phase correction, and the ratio of the amplitudes. It can be configured to calculate a first amplitude correction coefficient given as a constant according to a predetermined received signal. Further, the amplitude correction means can be configured to calculate a second amplitude correction coefficient given as a function of time for the predetermined received signal to which the phase correction has been performed. Preferably, the amplitude correction means has a first amplitude correction coefficient given as a constant corresponding to the ratio of the amplitudes of the plurality of received signals at the starting point of the phase correction and a second amplitude correction coefficient given as a function of time. , It is better to configure so as to calculate to a predetermined received signal. The calculation with the second amplitude correction coefficient can be configured to be performed for a predetermined phase or later of the received signal, and more preferably, the calculation with the second amplitude correction coefficient is the phase correction. It is better to configure it so that it is performed after the starting point. Further, the apparatus of the present invention may include a difference signal extraction means for extracting a difference signal component between received signals to which the amplitude correction has been performed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a received waveform diagram of a reflected wave generated by a distance variation. FIG. 2 is a waveform diagram in which the received waveforms shown in FIG. 1 are superimposed by matching the reception starting points. FIG. 3 is a waveform diagram showing a state in which the received waveform shown in FIG. 2 is phase-corrected. FIG. 4 is a waveform diagram showing a state in which the received waveform shown in FIG. 3 is subjected to amplitude correction. FIG. 5 is a waveform diagram showing the difference signal component of the received waveform shown in FIG. FIG. 6 is a graph showing amplitude correction data when amplitude correction is performed. FIG. 7 is a graph showing the depth error and the decrease in sensitivity that occur in response to distance fluctuations. FIG. 8 shows the electromagnetic wave probe of the present invention, (a) is a plan view, and (b) is a front view. FIG. 9 is an explanatory view of the display unit of the spacecraft, in which (a) is an overall front view of the display unit, (b) is an A scope mode display screen, and (c) is a B scope mode display screen. is there. FIG. 10 is a block diagram showing the basic configuration of the spacecraft shown in FIG. FIG. 11 is an explanatory diagram showing a method of configuring the relative permittivity of the spacecraft. FIG. 12 is an explanatory diagram of a calibration operation unit that calibrates the relative permittivity. FIG. 13 is a flowchart showing the received signal processing method of the present invention. FIG. 14 is an explanatory diagram of a state in which scanning with distance variation is performed. FIG. 15 is a display example when the depth is displayed using the difference signal component of the received signal. FIG. 16 is a display example when the depth is displayed using the received signal with the amplitude correction. FIG. 17 is a front view of the antenna substrate of the antenna unit used in the spacecraft of the present invention. FIG. 18 shows a shield case to which the antenna board is attached, (a) is a plan view thereof, (b) is a front view thereof, and (c) is a side view thereof. FIG. 19 shows an antenna unit used in the spacecraft of the present invention, (a) is a plan view thereof, (b) is a front view thereof, and (c) is a side view thereof. FIG. 20 is an exploded perspective view showing the internal configuration of the antenna unit. FIG. 21 is a waveform diagram of a feeding signal fed to the transmitting antenna. FIG. 22 is an explanatory diagram of the action of the electromagnetic wave absorbing material to absorb electromagnetic waves having a specific polarization component. Figure 23 shows the electromagnetic waves radiated from the antenna unit. It is a frequency spectrum diagram. FIG. 24 is an explanatory diagram showing a received waveform of the reflected wave. FIG. 25 is an explanatory diagram showing a received waveform of a reflected wave including reflection in an object. FIG. 26 is an explanatory diagram showing fluctuations in the received waveform when distance fluctuations occur. FIG. 27 is a waveform diagram in which the received waveforms shown in FIG. 26 are superimposed and displayed so that the reception starting points match. FIG. 28 is an example of a cross-sectional image when exploration with distance fluctuation is performed. Best Embodiment for Implementing the Invention In a preferred embodiment of the present invention, the received signal processing method analyzes and searches the received signal of the reflected wave by the object of the electromagnetic wave radiated from the antenna at predetermined intervals. Therefore, it is possible to have a step of performing phase correction on the received signal so as to remove the phase shift that occurs according to the distance fluctuation between the antenna and the search target. Further, the received signal processing method performs a first amplitude correction by calculating the first amplitude correction coefficient for a plurality of received signals that have undergone phase correction so as to reduce the amplitude difference between the received signals. Can have steps. Further, the received signal processing method is a second amplitude correction in which the amplitude correction data (second amplitude correction coefficient) indicated by the time axis and the predetermined amplification degree is used as weight data for the received signal to which the phase correction has been performed. Can have a step of doing. Further, the above method may include a step of extracting a difference signal component between received signals that have been subjected to amplitude correction. The exploration target in the present invention refers to a medium such as the ground or a wall in which buried objects such as land mines and clay pipes to be explored are buried, and the distance between the antenna and the exploration target is the antenna surface and the ground. It means the distance to the surface or wall surface, so to speak, the amount of lift. Further, the received signal exhibits an alternating waveform that can be expressed in the form of a function of time and signal strength, the time axis corresponds to the phase, and the signal strength corresponds to the amplitude. In order to perform phase correction on the received signal, a starting point for matching the phases in the received signal is specified. As this starting point, there is little distortion (harmonics and low harmonic components) of the received signal, and the positions of the received signals are different from each other. It is preferable to use a predetermined peak point at which the phase difference can be clearly grasped. As this peak point, a phase point at which the signal strength of the received signal becomes the maximum value may be used, or a phase point at which the signal strength of the received signal becomes the minimum value may be used, and the absolute value of the signal strength of the received signal may be used. You may use the phase point where is the minimum value (that is, the signal strength is 0). In addition, it is possible to specify the peak point by setting an appropriate extreme value condition. As the antenna of the electromagnetic wave probe in the present invention, it is preferable to use an antenna having extremely few harmonics and low harmonic components with respect to the electromagnetic wave of the target frequency to be radiated. According to this, there is little distortion in the received signal, and it is easy to identify the starting point for matching the phases. Here, assuming that the distance from the antenna to the ground surface is 10 cm and the frequency of the electromagnetic wave is 1.5 GHz (wavelength 20 cm), the phase is adjusted starting from the first maximum point (first peak point) of the received signal. Considering that the starting point corresponds to the antenna surface position, the minimum point (second peak point) of the received signal next to the maximum point coincides with the position on the substantially ground surface. In other words, the frequency of electromagnetic waves is 1. If the value is set lower than 5 GHz and the distance variation from the antenna to the ground surface is within 10 cm, it can be seen that the second peak point of the amplitude of the received signal is always located inside the ground. As described above, both electromagnetic waves before and after the change in the lift amount propagate while showing substantially the same attenuation rate at substantially the same frequency (period), although there is a phase shift and an amplitude difference after entering the ground. .. Therefore, it can be considered that the fluctuation of the received signal due to the distance fluctuation can be effectively compensated by performing the phase correction and the amplitude correction focusing on the second peak point of the amplitude of the received signal. That is, by comparing the phases of the second peak points of the amplitudes of the two received signals to be contrasted with each other to detect the phase difference, and performing a phase shift on one of the received signals by the detected phase difference, these are performed. It is possible to perform phase compensation for two received signals. In order to perform such phase correction, it is necessary to store and retain at least one waveform of the previously received received signal, and perform A / D conversion (analog-to-digital conversion) processing on the received signal. A configuration that can be stored as digital data can be adopted. Conventionally used configurations can be applied to the A / D conversion. For example, a predetermined time including the entire received waveform is sampled at 512 equal time intervals, and the sampled analog amplitude signal has a resolution of 12 bits. It is possible to perform processing such as conversion to the digital amplitude data to be possessed. In the present embodiment, since the fundamental frequency of the amplitude electromagnetic wave is extremely high (approximately 1 GHz), it is preferable to convert the received signal into a frequency-reduced received signal and perform sampling on the received signal. In this way, by performing phase correction that matches the phase of the second peak point of the amplitude in the received signal, even if the antenna causes some distance fluctuation with respect to the ground surface, the phase shift between the received signals is compensated. Therefore, it is possible to prevent the cross-sectional image generated from a large number of received signals from becoming a complicated image. Even if the received signal is phase-corrected, the compensation effect for the distance fluctuation is exhibited. However, as mentioned above, the attenuation rates in the atmosphere and in the ground are very different. Therefore, there is an amplitude difference between the received signals due to the fluctuation of the inrush phase to the ground surface. Therefore, by performing the amplitude correction so as to reduce the amplitude difference with respect to the phase-corrected received signal, the compensation effect for the distance variation is further increased. As a method of performing amplitude correction, the first amplitude correction is performed by comparing the second peak points of the amplitudes in the received signal and calculating the weighting coefficient (first amplitude correction coefficient) according to the amplitude ratio in the entire received signal. Can be taken. When the first amplitude correction is performed, the weighting coefficient can be calculated on the received signal having a large amplitude to match the received signal having a small amplitude. On the contrary, it is also possible to calculate the weighting coefficient for the received signal having a small amplitude and match it with the received signal having a large amplitude. In this case, it is possible to increase the amplitude of the entire waveform. It is also possible to fix the previous received signal as a reference and perform amplitude correction on the entire received signal so that the amplitudes of the second peak points match. By performing signal processing using the received signal subjected to the phase correction and the first amplitude correction in this way, it is possible to obtain a clear underground cross-sectional image in which the distance variation is effectively compensated. The first amplitude correction described above calculates and processes a uniform weighting coefficient for the received signal. However, since the attenuation rate of the received signal fluctuates with the passage of the reception time, more accurate correction can be performed by performing the amplitude correction according to the passage of time. That is, by performing the second amplitude correction on the received signal with the amplitude correction data (second amplitude correction coefficient) indicated by the time axis and the predetermined amplification degree as the weight data, the received signals accompanying the phase correction are subjected to each other. The amplitude difference of can be further suppressed. The second amplitude correction described above may be performed using one type of amplitude correction data, but one of a plurality of amplitude correction data having characteristics having different amplification degrees with respect to the time axis is appropriately selected. It is also possible to appropriately select the amplitude correction data according to the magnitude of the amplitude of the received signal and perform the optimum amplitude correction. The first amplitude correction and the second amplitude correction can be applied independently to the received signal with phase correction, but both are combined. It is also possible to apply it. Further, the first and second amplitude corrections described above can be performed on the entire waveform of the received signal to which the phase correction has been performed, but can also be performed on all signal components after a predetermined phase of the received signal. It is possible. For example, the amplitude correction may be performed on all the signal components after the second peak point of the amplitude of the received waveform to which the phase correction has been performed. According to this amplitude correction, the processing is simplified because the amplitude correction for the signal component before the second peak point is unnecessary. In the portion of the received signal before the second peak point of the amplitude where the amplitude correction is not performed, an amplitude difference occurs between the received signals and an unclear fluctuation occurs in the depth image. However, when scanning the spacecraft, if the antenna surface is set to the first peak point of the amplitude of the received signal, the second peak point corresponds to the vicinity of the substantially ground surface in the ground and does not cause any particular hindrance to the exploration of buried objects. .. Rather, fluctuations in the depth image occur in response to fluctuations in the distance between the antenna and the ground surface, so this is a guide for holding and scanning the spacecraft so that fluctuations do not occur. By the way, it is also possible to extract the difference signal component between the received signals subjected to the amplitude correction and display the cross-sectional image based on the extracted difference signal component. By extracting the difference signal component of the received signal subjected to the above-mentioned phase correction and amplitude correction, only the difference signal component in the state where the fluctuation between the received signals due to the distance fluctuation is corrected is extracted. That is, the difference signal component corresponds only to changes in physical properties (changes in relative permittivity) such as underground buried objects. In particular, by extracting the difference signal component, the noise of the in-phase component can be effectively removed and the minute signal can be detected, so that the minute difference in the buried object can be detected. By displaying the depth image using the extracted difference signal component, it is possible to display an easy-to-understand depth image displaying only the boundaries having different physical characteristics. As a result, it is possible to suitably perform boundary exploration of objects having similar relative permittivity, exploration when the buried object is limited to some extent, and the like. In this case as well, if the difference signal component is extracted without performing the amplitude correction before the second peak point of the amplitude of the received signal, the depth image will fluctuate, but it will be measured as a guideline for distance fluctuation. There is no hindrance to. When conducting ground penetrating radar, the signal processing method of the present invention can compensate for distance fluctuations in a range of 5 cm above and below at a position approximately 5 cm from the ground surface. That is, the depth error and the decrease in sensitivity due to the distance fluctuation tend to worsen after the distance fluctuation of about 5 cm. Therefore, it is preferable to use the above range, but the specifications are sufficient for practical use, and precise measurement is possible regardless of the skill of scanning the spacecraft. Further, the present invention can be implemented as a received signal processing device equipped in an electromagnetic wave probe that radiates electromagnetic waves at predetermined intervals and analyzes received signals due to reflected waves of an object for exploration. The received signal processing device of the present invention can be configured to include a phase correction means that corrects the phase of the received signal so as to remove the phase shift that occurs according to the distance fluctuation between the antenna and the search target. .. The received signal processing device of the present invention can be configured by using an analog processing circuit, but can also be configured by a digital processing circuit including a CPU and RAM and ROM necessary for its processing operation, and is a CPU. It is possible to realize the above method by the program processing of. For example, the received signal processing device samples the amplitude of a predetermined time including the entire received waveform at 512 equal time intervals by the A / D conversion operation processed by the CPU, and stores and holds it as digital data having a resolution of 12 bits. As a result, one received signal data is stored as 512 amplitude data arranged in order. In this embodiment, since the frequency of the radiated electromagnetic wave is extremely high (approximately 1 GHz), it is difficult to directly A / D convert the detection signal of the antenna. Therefore, a low-frequency reception signal can be generated by the reception unit based on the detection signal of the antenna, and the reception signal whose frequency has been reduced can be A / D-converted. The phase correction by the phase correction means can be configured to perform phase correction starting from a predetermined peak point between the received signals. This phase correction can be executed by digitally processing the received signal data stored in the received signal processing device. For example, to perform phase correction The amplitude data arranged in the received signal data is sequentially searched, and the amplitude data whose absolute value is, for example, the second peak point and the data number thereof are determined. Next, the received signal data is associated with the reference received signal by matching the data number of the second peak point in the received signal whose phase is shifted with the data number of the second peak point in the reference received signal. Then, the amplitude data of the received signal deviating from the front end or the rear end of the data number of the reference received signal is erased, and the data having no amplitude data within the range of the front end and the rear end of the data number of the reference received signal. Add empty amplitude data to the number. As a result, the received signal data is made up of 512 new amplitude data. By the above data processing, it is possible to match the phases of the second peak points of the amplitudes of the received signals. Further, the received signal processing device is configured to include a first amplitude correction means for performing amplitude correction on a plurality of received signals to which phase correction has been performed so as to reduce the amplitude difference between the received signals. ing. The first amplitude correction means can also be executed by digitally processing the received signal data stored in the received signal processing device in the same manner as the phase correction means. That is, in the received signal data composed of the amplitude data arranged in order, the amplitude of the received signal can be corrected by performing a predetermined arithmetic process on the amplitude data for each data number by the program processing by the CPU. For example, the amplitude of the second peak point in the received signal for which the amplitude correction is to be performed and the reference received signal are compared, and the weighting coefficient (first amplitude correction coefficient) corresponding to the amplitude ratio is applied to all the amplitude data. The first amplitude correction can be performed by calculation. In the amplitude correction by the first amplitude correction means, the weight coefficient is calculated for the received signal having a large amplitude to match the received signal with a small amplitude, and conversely, the weight coefficient is calculated for the received signal with a small amplitude to calculate the amplitude. It is also possible to match a large received signal. Further, the received signal processing device is indicated by a time axis and a predetermined amplification degree with respect to the received signal subjected to phase correction (that is, time). The configuration is provided with a second amplitude correction means for performing amplitude correction using the second amplitude correction coefficient (given as a function between) as weight data. The second amplitude correction means can also be executed by digitally processing the received signal data stored in the received signal processing device in the same manner as the first amplitude correction means. That is, while comparing the amplitude data and the amplitude correction data arranged in the order of the data numbers with the data numbers and the time data, the amplification degree of the second amplitude correction coefficient is added to the amplitude data for each data number by the program processing by the CPU. A second amplitude correction can be applied to the received signal by performing arithmetic processing. The first and second amplitude correction means can be configured to perform amplitude correction for all signal components after a predetermined phase in the first cycle of the received signal. For example, it is also possible to perform amplitude correction only on the signal components after the second peak point of the amplitude of the received signal as a reference for performing phase correction. Further, the received signal processing device can be provided with a difference signal extraction means for extracting a difference signal component between the received signals that have been subjected to amplitude correction. This difference signal extraction means can be executed by digitally processing the received signal data stored in the received signal processing device, similarly to the amplitude correction means. That is, the difference signal component can be extracted by arithmetically processing the difference of the amplitude data for each of the same data numbers in the received signal data that has already undergone the phase correction and the amplitude correction. Next, an electromagnetic wave radar antenna that can be suitably used for the electromagnetic wave probe of the present invention will be described. This antenna has a configuration in which a transmitting antenna element that receives an impulse output from a transmitting unit and radiates an electromagnetic wave is attached to a shield case so that the frequency of the electromagnetic wave radiated from the transmitting antenna element matches the target frequency. The dimensions of the transmitting antenna element and the shield case are related to each other according to the wavelength of the target frequency. Here, the target frequency is a frequency that is predetermined when designing an electromagnetic wave radar antenna, and the dimensional relationship of the antenna is determined in order to radiate this target frequency. To. In an electromagnetic wave radar antenna, an impulse is supplied to a transmitting antenna element to intermittently radiate an electromagnetic wave having a target frequency within a band of approximately 300 MHz to 3 GHz. In analyzing the radiation frequency component in such an ultra-high frequency band, it is not possible to discuss the transmitting antenna element alone, and a distributed constant circuit is an integrated structure consisting of a shield case including the transmitting antenna element, a feeding line, etc. It is necessary to analyze as equivalently. However, the inductance component and capacitance component of such a distributed constant circuit fluctuate due to slight differences in the shape and material of the antenna element, shield case, etc., and the fluctuating factor increases due to the addition of stray capacity due to the feeder line, etc. .. Moreover, it is difficult to analyze an equivalent distributed constant circuit because the electromagnetic wave itself is a transient phenomenon that is excited by an impulse rather than a repetitive signal. Therefore, the present inventors have made various studies on the shape of the antenna element and the shape of the shield case in order to match the frequency component of the electromagnetic wave radiated from the transmitting antenna with the target frequency and reduce the frequency component other than the target as much as possible. added. As a result, it was found that unnecessary radiation is reduced while increasing the output level of the target frequency by giving a predetermined relationship to the shape and dimensions of the transmitting antenna element and the shield case. In other words, we have succeeded in forming a distributed constant circuit having an integrated structure capable of amplifying the electromagnetic wave component of the target frequency and dampening the electromagnetic wave component of a frequency other than the target frequency by giving a predetermined relationship to the dimensional shape. When applying a transmission antenna impulse, a stable high output can be obtained by applying a DC bias to the transmission antenna element in advance, but the impulse is applied without applying a bias. It is also possible to do. According to this electromagnetic wave radar antenna, the unnecessary radiation component is extremely low, so that unnecessary radiation countermeasures for complying with the regulations of the Radio Law may be minor. That is, the thickness of the shield case is increased, or the outside of the shield case is covered with a thicker housing. There is no need to take measures against unnecessary radiation. As a result, the cost can be reduced and the weight of the antenna itself can be reduced to about 1/10 as compared with the conventional one, and it can be suitably used for a spacecraft that requires portability and portability. Moreover, since the unnecessary radiation component is small, the signal-to-noise ratio (S / N ratio) of the received signal is improved. As a result, it is not necessary to use a high-gain logarithmic amplifier or the like to separate and extract signal components close to the noise level, and sufficient signal level and S / N ratio can be secured just by using a normal linear amplifier, and the circuit configuration can be configured. It will be simple and stable. Further, since the S / N ratio of the received signal is high and the distortion of the received signal is reduced, it is possible to accurately calibrate the receiving base point using the first peak point of the received waveform or the like. In addition, since the S / N ratio of the received signal is high and the minute signal is not buried in the noise component and lost, the frequency (period) change according to the passage of time of the entire received wave including the reflected wave can be easily processed and output. , It is possible to precisely determine the physical properties of an object through which electromagnetic waves pass. As a result, accurate measurement can be performed regardless of the user, and exploration such as discrimination of objects and strata and discrimination of water leakage, which could not be performed in the past, becomes possible, expanding the purpose of use regardless of industrial or consumer use. Will be done. To briefly describe the principle of determining physical properties, the relative permittivity of an object through which an electromagnetic wave passes is proportional to the square of (speed of light / electromagnetic wave propagation velocity). As a result, the velocity of the electromagnetic wave passing through the object (period of the electromagnetic wave) is calculated from the received wave to obtain the relative permittivity of the passing object, and the physical properties are discriminated and the object is specified based on the obtained relative permittivity. It becomes possible. According to this electromagnetic wave radar antenna, among the impulse components fed to the transmitting antenna element, the electromagnetic wave component of the target frequency is enhanced and the electromagnetic wave component of the frequency other than the target frequency is attenuated. In this case, due to the resonance of the distributed constant circuit corresponding to the transmitting antenna element and the shield case, the output levels of low-tuning components and harmonic components such as 1/2 or 2 times the target frequency increase in addition to the target frequency. To do. Therefore, the receiver should selectively receive only one of these frequencies. It is also possible to adopt a configuration in which the frequency bandwidth is set and signal processing is performed. For the transmitting antenna element, the ground conductor, and the shield case, it is desirable to use a conductive material, that is, a material intended to guide a current with a small power loss. As such a conductive material, copper, aluminum, an aluminum alloy or the like is suitable in consideration of conductivity, mechanical strength, processability, economy and the like. It is also possible to use a conductor formed by applying a conductive paint or the like on the surface of a non-conductive material for a shield case or a transmitting antenna element. The transmitting antenna element is preferably formed by providing a conductor foil on a substrate such as phenol resin or epoxy resin. For example, a transmitting antenna element made of a copper plate or the like is provided with an insulator near the opening side of the shield case. It is possible to adopt various aspects such as a structure that supports the space by using it. This electromagnetic wave radar antenna has an antenna substrate having a transmitting antenna element that receives an impulse output from a transmitting unit and radiates an electromagnetic wave, and a hollow square shield case that covers the surface of the substrate on the side where the transmitting antenna element is provided. It is rational to have a configuration with and. The transmitting antenna element is formed on an antenna substrate by facing a pair of isosceles triangular conductive foils in a butterfly tie shape, and the substrate is a square ground conductor foil made of a conductive foil having a predetermined width so as to surround the transmitting antenna element. It can be arranged in a loop and formed so as to be symmetrical in the front-back and left-right directions. Further, the length of the base or side of the isosceles triangle of the transmitting antenna element can be set to approximately 1/2 wavelength of the target frequency. Here, the isosceles triangle includes an equilateral triangle, and particularly preferably, the transmitting antenna element is formed of a pair of equilateral triangle conductive foils, and the side length of the equilateral triangle is approximately 1/2 wavelength of the target frequency. It is better to set it to. On the other hand, the dimension of the shield case in the direction orthogonal to the direction in which the opposite isosceles triangle (equilateral triangle) elements of the transmitting antenna element are arranged is set to substantially the same length as the wavelength of the target frequency, and the depth of the shield case is set. The dimensions are set to a length that is approximately 1/4 of the target frequency and an integral multiple of the wavelength. These dimensions It was found that the output level of the target frequency had a peak in the vicinity of a specific depth dimension when the wavelength was changed to 4/4 wavelength. This is because the stored energy (resonant energy) by the distributed constant circuit consisting of the integrated structure of the shape of the transmitting antenna element, the shape of the shield case, and the shape of the ground conductor with respect to the wavelength of the target frequency is the target frequency at a predetermined depth dimension. It is thought that this is because it is the maximum. As a result, the optimum radiation level can be obtained by appropriately changing the depth dimension. When a plurality of transmitting antennas having the same target frequency were prototyped according to the above-mentioned dimensional relationship, the present inventors made a difference in the target frequencies of electromagnetic waves radiated from each antenna despite variations in wiring such as feeder lines. It was also found that the frequency was hardly generated and the reproducibility was excellent. As a result, there is no variation in the target frequency for each device, so that the circuit configuration that does not require the trouble of adjusting the receiving unit (reception unit) for each device is simplified, stable, and easy to manufacture. As described above, the frequency of the electromagnetic wave radiated from the transmitting antenna of the present invention is a specific frequency (target frequency) between approximately 300 MHz and 3 GHz and belongs to the microwave band. Therefore, for example, when aluminum or the like is used as the shield case, the thickness of the material affects the distribution constant. The inductance component when electromagnetic waves are distributed in the shield case increases as the material thickness becomes thinner and decreases as the material thickness increases. Therefore, it is desirable that the antenna shape of the present invention is dimensionally corrected according to the material thickness of the shield case or the thickness of the conductor foil of the transmitting antenna element. That is, when a shield case having a thin material thickness is used, it is possible to easily adjust to the target frequency by increasing the correction value as compared with the case where a thick shield case is used. It is desirable to provide a suppression resistor between the transmitting antenna element of the antenna substrate and the ground conductor that suppresses parasitic radiation of electromagnetic wave components other than the target frequency. By appropriately setting the value of the suppression resistor, it is possible to effectively reduce the output level in the frequency band other than the target while suppressing the decrease in the output level of the target frequency. As a result, the S / N ratio in the received wave is further improved. Further, the electromagnetic wave absorbing material may be arranged inside the shield case so as to absorb and attenuate the electromagnetic wave component having a specific plane of polarization among the electromagnetic wave components excited inside the shield case including the transmitting antenna element. Among the electromagnetic waves radiated from the transmitting antenna element, the present inventors have unintended frequency components in the electromagnetic waves having an electric field component (polarization plane) in the direction in which the opposite isosceles triangle (equilateral triangle) elements are arranged. Was found to be contained in a relatively large amount. Therefore, by attenuating the electromagnetic wave component having the polarization plane with the electromagnetic wave absorber, the electromagnetic wave of the unintended frequency component radiated can be further reduced, and the S / N ratio in the received wave can be further improved. Can be done. As the electromagnetic wave absorbing material, a general-purpose material in which a conductive radio wave reflecting material is attached to a foam material or the like can be used, and it is possible to effectively attenuate and absorb the electromagnetic wave by utilizing the attenuation at the time of reflection. The electromagnetic wave radar antenna may be formed by separately forming the transmitting antenna element and the receiving antenna element, but it can also be formed integrally. That is, the transmitting antenna element and the receiving antenna element having the same shape as the element are formed symmetrically on the antenna substrate including the ground conductor, and the shield case is an electromagnetic coupling between the transmitting antenna element and the receiving antenna element. It can be configured to include a shield partition wall for shielding the antenna. According to the transmission / reception integrated electromagnetic wave radar antenna, the electromagnetic coupling between the transmission antenna side and the reception antenna side is reduced by the shield partition wall provided in the shield case, so that the transmission / reception antenna can be made compact and lightweight while maintaining the above-mentioned characteristics. It is suitable for equipment that can be made into a product, is easy to manufacture, and requires portability. Next, a specific example of the embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the time axis (horizontal axis) of the received signal generated by the receiving unit 50 based on the detected signal of the reflected wave received by the receiving antenna R of the electromagnetic wave radar antenna AT of the spacecraft 70 shown in FIGS. 8 to 10. It is shown as a received waveform using and the amplitude axis (vertical axis), and is it the ground surface G? It is shown schematically corresponding to these depths. The electromagnetic wave radar antenna AT has a transmitting antenna T and a receiving antenna R adjacent to each other and integrally incorporated, and the detailed structure will be described later. In Fig. 1, the distance between the antenna AT and the ground surface G is d.₀It shows a state that fluctuates from to d. When the surface of the antenna AT is the point where the amplitude of the received signal is maximum (first peak point) when the electromagnetic wave is radiated toward the air, the antenna AT is brought close to the ground surface G and the electromagnetic wave is radiated. As shown in the received waveform shown in 1, the first peak point P of the amplitude is affected by the ground G.₀', P'causes a slight phase shift on the ground surface G side. Also, the second peak point P₀, P are both relative permittivity ε_rIs located in a substantially constant underground, so that the received signals after the second peak point are attenuated at substantially the same period and at substantially the same attenuation rate. Figure 2 shows the distance d between the antenna AT and the ground surface.₀Received signal E in₀And the received signal E at the distance d, respectively, the starting point R of the received signal₀Are shown in a matching and superposed manner. As can be seen from the figure, the received signal E is caused by the change in the distance between the antenna AT and the ground surface G.₀And the received signal E is the second peak point P of each amplitude.₀And φ at P₀Is out of phase. (Phase correction) In this embodiment, first, this phase shift φ₀Received signal E to eliminate₀The received signal E is phase-corrected. That is, as shown in FIG. 3, the second peak point P₀The entire received signal E is phase-shifted in the time axis direction so as to match the phase of the second peak point P. As a result, the received signal E after the second peak point₀And the received signal E have substantially the same phase and have an attenuated waveform with a slight amplitude difference. On the other hand, before the second peak point, the received signal E₀Since the atmospheric passage time of the received signal E is short and the atmospheric passage time of the received signal E is long, the period of the received signal E is relatively long. In this way, the received signal E can be obtained simply by matching the phases of the second peak points of the amplitude.₀The signal fluctuation due to the distance fluctuation of the received signal E can be significantly suppressed. Therefore, a stable cross-sectional image can be displayed even if the received signal E that has been subjected to only phase correction is signal-processed. By further performing amplitude correction on the phase-corrected received signal, it is possible to perform compensation that further suppresses signal fluctuation due to distance fluctuation. (Amplitude correction) As shown in Fig. 3, received signal E₀2nd peak point P in₀Is the amplitude L₀, The amplitude of the second peak point P in the received signal E with phase correction is L, and the amplitude L is the amplitude L because the inrush phase into the ground with a large attenuation factor is delayed.₀Greater than The first amplitude correction in this embodiment is this small amplitude L.₀Received signal E to match the large amplitude L₀It is intended to increase and correct the amplitude of. That is, the amplitude ratio (L / L)₀) As weight data (first amplitude correction coefficient), received signal E₀2nd peak point P₀Received signal E by performing arithmetic processing on all subsequent signal components₀Increases the amplitude of. As a result, as shown in FIG. 4, the second peak point P₀Received signal after P, E₀And the amplitude difference of E is extremely reduced. That is, the second peak point P₀The amplitude difference of the received signal after P, P is the reflected wave E caused by the change of the buried object.₀Only the 1 and E1 parts are used, and the harmful amplitude difference due to distance fluctuation is effectively suppressed. In this way, the received signal E due to the distance fluctuation₀And the second peak point P of E₀Since unnecessary amplitude differences after P and P are removed, it is possible to display a clear depth image. The second peak point P of the amplitude in the received signal₀In the received waveform before P, the phase shift remains even at the stage where the phase correction is applied, and the effect of the amplitude correction is low. For this reason, unclear fluctuations occur in the generated image, but these fluctuations decrease as the distance fluctuation is reduced. Therefore, the spacecraft 70 can be scanned with the occurrence of fluctuations as a guideline for the occurrence of distance fluctuations. In this first amplitude correction, the second peak point P₀, P amplitude ratio (L / L₀) Was used as the weighting function, but it is also possible to perform more accurate amplitude correction in consideration of the attenuation factor according to the passage of time of the received signal. That is, the received wave exhibits a peculiar attenuation according to the passage of propagation time in the medium except for the reflected wave portion due to the buried object. Therefore, it is preferable to perform amplitude correction according to the propagation time. In this embodiment, as shown in FIG. 6, a plurality of second amplitude correction coefficients given as a function of time are prepared in advance, and each coefficient corresponds to a function expression or a time and a predetermined amplification degree. It is stored in a storage medium such as a memory in the form of a reference table, and one of these plurality of second amplitude correction coefficients is appropriately selected, and the selected second amplitude correction coefficient is weighted. The second amplitude correction is included together with the first amplitude correction. That is, the received signal E₀And the second peak P of the received signal E₀, P amplitude ratio (L / L)₀). And the received signal E₀The time axis of is associated with the time axis of the normal amplitude correction data, the predetermined amplification degree corresponding to each time axis is derived from the second amplitude correction coefficient, and the amplitude ratio (L / L) at the second peak point is derived.₀) Is derived, and these predetermined amplification degrees and amplitude ratios are set to the received signal E after the second peak point.₀Amplitude correction is performed by arithmetic processing. This makes it possible to perform more accurate amplitude correction in consideration of the attenuation factor on the time axis. As shown in FIG. 6, when the amplitude of the received signal is further lower, it is possible to apply appropriate high amplitude correction data to perform amplitude correction suitable for signal processing. (Difference signal component extraction) As shown in Fig. 4, received signals E and E with amplitude correction₀The difference signal component is extracted. That is, from the received signal E to the received signal E₀By performing a negative operation on, the received signal E as shown in Fig. 5₀Only the difference signal component E'of the received signal E with respect to is extracted. This difference signal component E'is the received signal E₀It is only the signal component generated between E and E in response to the change in the buried object (change in the relative permittivity). By displaying the depth image using this difference signal component E', it is possible to perform a clear display corresponding only to the change point of the physical properties of the buried object. Further, the difference signal component E'is stored in memory for each of a plurality of exploration positions at predetermined horizontal intervals, and a cross-sectional image is generated and displayed using the plurality of difference signal components E'. This makes it possible to efficiently search for objects with close relative permittivity, which was difficult in the past. FIG. 7 is a graph showing the results of measuring the depth error and the sensitivity change caused by the distance change between the antenna AT and the ground surface G. As can be seen from the figure, when the distance fluctuation exceeds approximately 5 cm, the distance ratio between the atmosphere and the ground through which electromagnetic waves pass increases, and the depth error of the received waveform when phase correction or amplitude correction is applied increases sharply. .. In addition, as the distance fluctuation approaches 5 cm, the sensitivity difference in the ground increases, making compensation difficult. Therefore, the received signal processing method of this embodiment corresponds to a distance variation within a range of approximately 5 cm above and below, and is preferably used within a range of 5 cm above and below the ground surface 5 cm. Next, an example of the electromagnetic wave probe 70 of the present invention will be described. The electromagnetic wave probe 70 shown in FIG. 8 is based on one-handed portable exploration, and an electromagnetic wave radar antenna AT is provided at the lower end of the pipe shaft 71 formed in a substantially "he" shape, and is provided at the upper end side. The shape is such that the arm is passed through the arm holder 76, the grip 75 is gripped, and the grip 75 is held with one hand. A signal processing unit 73 is provided on the shaft 71 above the electromagnetic wave radar antenna AT, and a central processing unit 72 equipped with a CPU is provided on the upper end of the shaft 71. In addition, a display unit 74 using a color liquid crystal display is provided at the tip of the grip 75, and the shape is such that the settings for exploration and the measurement results can be easily seen. A counterweight 77 for weight balance is attached to the end of the central processing unit 72, making it easy to hold the spacecraft 70 with one hand. Also, the pipe shaft 71 is shuffled. The length can be variably set by the adjusting unit 78, and can be optimally set according to the height of the explorer. FIG. 9 (a) shows the display 74 of the spacecraft 70. The display unit 74 includes a liquid crystal display 74a made of a color liquid crystal equipped with a touch panel 74b, and an operation switch 74c for performing operations such as power on (start) and power off (stop). On the liquid crystal display 74a, the search results can be switched and displayed in various modes and various settings can be made by operating the touch panel 74b according to the display. The spacecraft 70 of the present embodiment has various display modes based on the received waveform, and examples of the display modes particularly related to the present invention include the A scope mode and the B scope mode. In the A scope mode, as shown in FIG. 9B, a single received signal is displayed as a received waveform having a time axis and an amplitude axis. In the B scope mode, as shown in FIG. 9 (c), a plurality of received signals are signal-processed, the relative permittivity for each depth is obtained based on the period of each received signal, and the horizontal axis is the number of scans (scanning distance). , It is displayed as a color cross-sectional image according to the relative permittivity on the screen with the vertical axis as the depth. FIG. 10 is a block diagram showing the basic configuration of the spacecraft 70 of this embodiment, and the parts corresponding to FIG. 8 are designated by the corresponding reference numerals. The antenna AT has a configuration in which a transmitting unit 40 and a receiving unit 50 and a transmitting antenna T and a receiving antenna R formed on the same substrate are built in a shield case (not shown). The transmitting unit 40 supplies impulses and biases to the transmitting antenna T, and the receiving unit 50 uses the reception synchronization signal transmitted from the signal processing unit 73 to detect the reflected wave captured by the receiving antenna R. It performs an operation of amplifying and outputting as a frequency-converted low-frequency reception signal. The details of the antenna AT will be described later. The signal processing unit 73 has an analog circuit unit 73a that is connected to the antenna AT and performs analog signal processing. The analog circuit unit 73a receives the control signal transmitted from the central processing unit 72 and generates an impulse to the transmission unit 40 of the antenna AT. It sends out the pulse signal of. Further, the analog circuit unit 73a receives the control signal transmitted from the central processing unit 72 and sends a reception synchronization signal to the receiving unit 50 of the antenna AT, and preprocesses the received signal transmitted from the receiving unit 50. It is transmitted to the central processing unit 72. In this embodiment, one received signal radiates an impulse-shaped electromagnetic wave from the transmitting antenna 1024 times, samples the detection signal of the receiving antenna 1024 times in synchronization with the radiation timing and gradually delays, and these sampling signals. Can be generated by detecting the enveloping value. Even if the center frequency of one impulse-like electromagnetic wave is, for example, 1 GHz, the received signal is frequency-converted into an AC waveform having a center frequency of about several MHz to several tens of MHz by the above sampling process. Such sampling processing is performed by the receiving unit 50, and the processed reception signal is output from the receiving unit 50 to the signal processing unit 73. The central processing unit 72 includes a digital circuit unit 72a that performs digital processing using a CPU, and an I / F circuit 72b that transmits and receives data between the IC card 79 for storing data such as received signals. There is. The digital circuit unit 72a performs A / D conversion (analog-to-digital conversion) of the received signal transmitted from the signal processing unit 73 and stores it as digital data. Then, necessary signal processing is performed by executing digital processing on the stored received signal data, and the signal-processed data is transmitted to the display unit 74 for display. Further, the digital circuit unit 72a stores necessary sample data and the like in the IC card 79, which is an external storage medium, via the I / F circuit 72b, and reads the stored data from the IC card to perform signal processing. The IC card 79 is configured by using RAM that holds data with a button battery, EEPROM that does not require a backup power supply, etc., and 2MB, 4MB, 8MB, depending on the amount of data to be stored. The one with a memory capacity of 16MB is available. Here, the received signal processing device of this embodiment is configured around the central processing unit 72, and the phase correction means, the amplitude correction means, and the difference signal extraction means are executed by the digital circuit unit 72a of the central processing unit 72. It is realized by digital processing by the program to be performed. Therefore, the received signal processing device has the same reference numerals as those included in the digital circuit unit 72a. Amplitude is sampled at 512 equal time intervals for a predetermined time including the entire received signal waveform by the A / D conversion operation digitally processed by the digital circuit unit (received signal processing device) 72a, and stored as digital data with a resolution of 12 bits. Hold. As a result, one received signal data is stored as 512 amplitude data arranged in order. In this embodiment, since the frequency of the detection signal of the receiving antenna is extremely high (approximately 1 GHz), it is difficult to directly sample the detection signal for the above A / D conversion. In the above, a received signal whose frequency is reduced by a receiving unit is used, and the received signal is sampled. The phase correction by the phase correction means is performed by digitally processing the received signal data stored in the digital circuit 72a by the CPU. That is, the amplitude data arranged in order among the received signal data for which the phase correction is to be performed are sequentially searched, and the amplitude data whose absolute value is the second peak point and its data number are determined respectively. Next, the received signal data is associated with the reference received signal by matching the data number of the second peak point in the received signal whose phase is shifted with the data number of the second peak point in the reference received signal. Then, the amplitude data of the received signal deviating from the front end or the rear end of the data signal of the reference received signal is erased, and the data having no amplitude data within the range of the front end and the rear end of the data number of the reference received signal. Add empty amplitude data to the number. As a result, the received signal data is made up of 512 new amplitude data. Received by the above data processing It is possible to match the phases of the second peak points of the amplitudes of the signals. Similar to the phase correction means, the first and second amplitude correction means are also executed by digitally processing the received signal data stored in the digital circuit unit 72a by the CPU. In this embodiment, the received signal E for which the amplitude correction is to be performed and the reference received signal E₀The first amplitude correction is executed by comparing the amplitudes of the second peak points in and the above and calculating the weighting coefficient (first amplitude correction coefficient) according to the amplitude ratio in the amplitude data after the second peak point. .. Further, in the digital circuit unit 72a, the time axis and the amplitude correction data (second amplitude correction coefficient) indicated by the predetermined amplification degree are stored in advance, and the time axis of the amplitude correction data and the data number are associated with each other. The second amplitude correction is performed by performing a predetermined amplitude calculation on the amplitude data after the second peak point. The difference signal extraction means is also executed by programming the received signal data stored in the digital circuit unit 72a in the same manner as the phase correction means. In this embodiment, the difference signal component is extracted by arithmetically processing the difference of the amplitude data for each of the same data numbers in the received signal data that has already undergone the phase correction and the amplitude correction. The display unit 74 includes a liquid crystal controller 74c that drives the liquid crystal display 74a by receiving control signals of the liquid crystal display 74a and the digital circuit unit 73b, and a touch panel 74b and an operation switch 74d provided on the surface of the liquid crystal display 74a. It has. The power supply that drives each circuit uses a battery (not shown) in order to take advantage of portability and portability. (Relative Permittivity Calibration Method) Next, the received signal processing of this embodiment in the spacecraft 70 will be described, and the relative permittivity calibration method required prior to the measurement will be described. When measuring with the spacecraft 70, it is necessary to calibrate the relative permittivity in advance. In the A scope mode of the spacecraft 70, the maximum value on the time axis is set to 5 msec, and the relative permittivity ε at a time of 5 msec._rThe screen is displayed so that the depth at = 12 is 1.5 m. Therefore, the reference relative permittivity (ε)_rMeasure the reflected wave in the reference dielectric with = 12) and the calibration distance (50 cm), and adjust the depth from the starting point to the reception of the reflected wave at the calibration distance in the received waveform to the position of 50 cm in A scope mode. Surface wave W at this time₀The period of is calculated as the calibration value. In this embodiment, the surface wave W₀The calibration value of is set to 0.75 msec. In other words, the surface wave W when electromagnetic waves are radiated toward the air.₀By adjusting the period of to the calibration value of 0.75 msec, the reference permittivity in the A scope mode and the internal processing of the spacecraft 70 can be calibrated to 12. As shown in FIG. 12, the adjusting unit 72d for calibrating the relative permittivity and the like includes a synchronous phase adjusting device 72e including a semi-fixed resistor and a signal cycle adjusting device 72f. The adjusting unit 72d is provided inside the central processing unit 72, and can be easily adjusted using a tool such as a screwdriver. The relative permittivity calibration of the spacecraft 70 during exploration is performed by the following procedure. (1) Electromagnetic waves are radiated to the air by the spacecraft 70, and the received signal of the reflected wave is displayed in A scope mode. In the received waveform, the surface wave W as shown in FIG.₀Adjust with the signal cycle adjuster 72f so that the cycle of is 0.75 msec. (2) Furthermore, the surface wave W is caused by the synchronous phase adjustment period 72e.₀Adjust the display so that the first peak point P'of is the base point of the time axis (the left end of the vertical axis). This allows the display of received signals and internal signal processing to have a relative permittivity of ε._rIt is calibrated equivalently so that it is performed with reference to the reference permittivity of = 12, and the starting point of the received signal is set to the first peak point. (Operation of the spacecraft and operation of receiving signal processing) Next, the operation of receiving signal processing in the spacecraft 70 will be described with reference to the waveform diagrams of FIGS. 1 to 5, the block diagram of FIG. 10, and the flowchart of FIG. As shown in FIG. 14, the distance between the antenna AT of the spacecraft 70 and the ground surface G is sequentially changed according to the scanning, for example, 5 cm 8 cm 2 cm. (1) As shown in Fig. 14, scanning is started by the spacecraft 70 at a distance of about 5 cm from the ground surface. (2) An electromagnetic wave is transmitted from the transmitting antenna T, and the received signal captured by the receiving antenna R and frequency-converted by the receiving unit 50 is transmitted to the analog circuit unit 73a of the signal processing unit 73. The analog circuit unit 73a transmits a received signal or the like to the central processing unit 72 after performing pre-processing for digital processing. In the digital circuit unit 72a of the central processing unit 72, the amplitude of the received signal is sampled at 512 equal time intervals within a predetermined time, and the digital data obtained by A / D converting the sampled amplitude with 12-bit resolution is used as the initial reception signal E.₀Memorize as. (See Step 100 in Figure 13). (3) In the digital circuit section 73b, the initial received signal E stored so far.₀Or, use one of the received signals E as the reference signal E.₀Set as. The initial reception signal E at the start of exploration, etc.₀In the state where only is stored, the initial received signal E₀The reference signal E₀(See step 102 in Figure 13). (4) The reflected wave of the electromagnetic wave that is subsequently output is read as the received signal E and stored in the digital circuit unit 72a (see step 103 in FIG. 13). (5) In the digital circuit unit 72a, if the amplitude is less than the predetermined level according to the amplitude of the received signal E, the high amplitude correction is selected, and if the amplitude is the predetermined level or more, the normal amplitude correction is selected (Fig. 13 step). See 105 ~ 107). (6) Reference signal E in the digital circuit section 72a₀2nd peak point P₀And the phase difference φ between the received signal E and the second peak point P₀Is detected, and the phase of the received signal E is adjusted so that the phases of the second peak points match each other (see step 108 in FIG. 13). (7) Then, the reference signal E₀And the amplitude L at the second peak point of the received signal E₀And L are obtained, and the amplitude correction including the normal amplitude correction or the high amplitude correction selected in steps 106 and 107 is performed on the received signal E. That is, (received signal E) × (L)₀Performs arithmetic processing of / L) × (normal or high amplitude correction) (see step 109 in Fig. 13). (8) The reference signal E of the received signal E with amplitude correction in the digital circuit section 72a.₀The difference signal component with respect to is extracted, B-scope image data is generated based on the extracted difference signal component, and is displayed on the display unit 74 (see steps 110 and 111 in FIG. 13). When the exploration process is subsequently performed in step 112, the process returns to step 102 and the same process is repeated. The reference signal E in step 102₀The setting of can be changed according to the scanning speed of the spacecraft 70. That is, when the scanning speed is slow, the immediately preceding received signal is used as the reference signal E.₀If the scanning speed is high, the received signal that goes back a predetermined number of times is used as the reference signal E.₀It is also possible to perform signal processing by setting to, and it is possible to display an optimum exploration image according to the scanning distance. FIG. 15 shows an example of the B-scope image obtained by the above exploration. In this cross-sectional image, complicated image development in the vertical direction due to distance fluctuation is eliminated, and only the outlines of buried objects Q1 to Q3 with different relative permittivity are displayed so as to stand out, so it is easy to analyze by visual inspection of the cross-sectional image. Is. On the other hand, FIG. 16 shows an example in which an image is displayed using the received signal E in a state where the difference signal is not extracted and the amplitude is corrected. Even in this underground cross-sectional image, a stable image is displayed without the image of the buried object fluctuating up and down due to the change in distance. (Structure of Antenna Unit) Next, an example of the antenna unit AT used in the electromagnetic wave probe of the present invention will be described in more detail with reference to the drawings. The antenna unit AT of the present invention has a square box shape, but has a configuration in which a disk-shaped housing is placed around the antenna unit AT. Further, the target frequency of the electromagnetic wave to be radiated from the antenna unit AT is fo, and the wavelength is λo. As shown in FIG. 17, the antenna substrate 1 has a vertically long H and a horizontal width of 2 W (= 2λ).₀), And has a structure in which the transmitting antenna T and the receiving antenna R having the same shape are integrally and symmetrically arranged on the same substrate. Therefore, in explaining the antenna substrate 1, the transmitting antenna T, which is half the size, will be described. The antenna substrate 1 is formed by removing unnecessary parts of the copper foil on the surface of the substrate 12 made of glass epoxy resin, excluding the transmitting antenna element 11 and the ground conductor 13, by etching. The transmitting antenna T has a vertical length H and a horizontal width W (= λ).₀In the center of the substrate 12 of), antenna elements 10 and 10 made of equilateral triangular copper foil having a side length of L are formed in a bow tie shape with the tops 10a and 10a facing each other to form the transmitting antenna element 11. A ground conductor (copper foil) 13 having a width F is provided in a square loop shape along the side edge of the substrate 12 so as to surround the transmitting antenna element 11 to form a symmetrical shape in the front-back and left-right directions. It should be noted that a slight gap is provided between the tops 10a and 10a of the antenna elements 10 and 10 to insulate them, and a feeder wire described later is soldered to the tops 10a and 10a. The length L of one side of the antenna element 10 is 1/2 of the width W of the substrate 12, that is, the wavelength λ.₀The length of the antenna element 10 is halved, and a suppression resistor 14 for suppressing parasitic vibration is soldered to the tops 10b, 10b and tops 10c, 10c of the antenna element 10 between the antenna element 10 and the ground conductor 13. The width F of the ground conductor 12 is not particularly limited as long as the targetness of arrangement on the substrate 12 is maintained, but the width F is wider than the mounting curved surface of the shield case in consideration of conductivity when mounted on the shield case described later. Is trying to be wide. The vertically long H of the transmitting antenna T is not particularly limited, but is set longer than the total length of the transmitting antenna element 11 in the vertical direction plus a width twice the width F of the ground conductor 13. The opening 15 provided on the ground conductor 13 is an insertion port for screws for mounting and fixing the antenna board 1 to the shield case 2 as described later. As shown in FIG. 18, the shield case 2 is made of aluminum having a thickness t of 1.2 mm, and is vertically long H and horizontally 2 W (= 2λ).₀), It is formed in the shape of a square box having a depth D, and the upper opening is provided with a bent portion 20 having a width F'over the entire circumference of the opening side edge. The ground conductor 13 of the antenna board 1 is attached and fixed to the bent portion 20 in a conductive contact state, and the width F'of the bent portion 20 is set to be smaller than the width F of the ground conductor 13. There is. Depth D is the target frequency f₀Wavelength λ₀On the other hand, λ₀Integer multiple of / 4, that is, λ₀/ 4, 2λ₀/ 4, 3λ₀/ 4, 4λ₀/ 4, ..., nλ₀It is set to any length of / 4, and the target frequency f₀The dimension of depth D can be set to any length so that the output level of is maximized. Further, in the center of the shield case 2, a shield plate (shield partition wall) 21 using aluminum for reducing the electromagnetic coupling between the transmitting antenna T and the receiving antenna R is provided in the vertical direction over the entire depth. The shield case 2 is divided into a transmitting side T1 and a receiving side R1 by the shield plate 21. In this embodiment, the shield plate 21 has a thickness t1 of 2 mm. Further, the screw hole 22 is for inserting a screw for mounting and fixing the antenna board 1. FIG. 19 (a) is a top view showing a state in which the electromagnetic wave radar antenna AT, that is, the antenna substrate 1 is attached to the shield case 2, and FIG. 19 (b) is a sectional view taken along the line AA of FIG. 19 (a). c) shows the cross-sectional view taken along the line BB in (a). The antenna board 1 is attached and fixed to the screw holes 22 of the shield case 2 using three screws 23 so that the surface on which the transmitting antenna element 11 and the ground conductor 13 are provided faces downward. As a result, the ground conductor 13 of the antenna substrate 1 is fixed in conductive contact with the bent portion 20 and the shield plate 21. When attached in this way, the transmitting antenna T of the antenna board 1 is located so as to cover the opening portion of the transmitting side T1 of the shield case 2, and the receiving antenna R of the antenna board 1 is located at the opening portion of the receiving side R1 of the shield case 2. It is located so as to cover. That is, in this antenna AT, the electromagnetic wave excited by the antenna substrate 1 including the shield case 2 is transmitted through the antenna substrate 1 itself and radiated forward. In this embodiment, the transmission / reception unit, the electromagnetic wave absorber, the feeding line, and the like are simultaneously incorporated before the antenna substrate 1 is attached and fixed to the shield case 2. The procedure for assembling these members will be described below with reference to the exploded perspective view of FIG. As shown in FIG. 20, in the shield case 2, the transmitting unit T1 and the receiving side R1 shielded by the shield plate 21, the transmitting unit 40, the receiving unit 50, and the electromagnetic wave absorber 30, 30 and 30 are stored, and the antenna board 1 is attached and fixed so as to cover it. A feeder line 16 and a feeder line 17 are connected to the top portions 10a and 10a of the antenna element 10 to the transmitting antenna T and the receiving antenna R of the antenna substrate 1. That is, a coaxial cable is used for the feeder line 16, the core wire is soldered to the top portion 10a of one antenna element 10, and the shielded wire is soldered to the top portion 10a of the antenna element 10 facing the other. A pin connector 16a for high frequency is provided at the other end of the feeder line 16, and by connecting this pin connector 16a to the connector 40a on the transmission unit 40 side, DC bias and impulse can be transmitted from the transmission unit 40 to the transmission antenna element 11. Power is supplied. The transmission unit 40 is provided with a connector 40b, and by connecting the connector 41, a power source and a control signal are supplied from a separately installed signal processing unit (not shown). Similarly, a coaxial cable is also used for the feeder line 17, and the core wire is soldered to the top portion 10a of one antenna element 10 and the shielded wire is soldered to the top portion 10a of the antenna element 10 facing the other. Further, a pin connector 17a for high frequency is also provided at the other end of the feeder line 17, and by connecting this pin connector 17a to the connector 50a on the receiving unit 50 side, the received signal captured by the receiving antenna R is received by the receiving unit 50. Transmit to the side. The receiving unit 50 is provided with a connector 50b, and by connecting the connector 51, a reception synchronization signal and power are supplied from a separately installed signal processing unit (not shown), and a frequency-variated reception signal is received. Send out. The shield case 2 has an opening 2a, 2b is provided and is connected to the control unit side through the wiring derived from the transmission unit 40 and the reception unit 50. As described above, the electromagnetic wave radar antenna AT of the present invention has a lightweight structure in which the antenna substrate 1 is attached to the shield case 2 made of thin aluminum and the transmitting unit 40 and the receiving unit 50 are housed inside. It is extremely lightweight compared to conventional antennas that prioritize measures against unnecessary radiation. Further, the structure having resonance of the antenna substrate 1 and the shield case 2 eliminates signal coupling failure (natural wave detection failure), and stable transmission / reception can be performed. FIG. 21 shows a signal transmitted from the transmission unit 40 to the transmission antenna element 11 via the feeder line 16 with time on the horizontal axis and voltage level on the vertical axis. In this embodiment, a DC bias is applied so that the core wire of the feeder line 16 has a voltage Vd with respect to the shielded wire. That is, a DC bias current is applied through the opposing antenna element 10, the suppression resistor 14, and the ground conductor 13. In this state, an impulse S is transmitted between the antenna elements 10 via the feeder line 16 and has a predetermined period T.₀By applying each time, electromagnetic waves are radiated from the antenna substrate 1 including the shield case 2. By applying the DC bias, the transmission unit 40 can control and drive the DC bias voltage in an impulse shape to apply an impulse to the transmitting antenna element 11, which simplifies the circuit configuration. FIG. 22 schematically shows a state in which the electromagnetic wave absorber 30 absorbs a specific electromagnetic wave component radiated from the transmitting antenna T. The electromagnetic wave absorber 30 is a general-purpose material in which a conductive radio wave reflecting material is attached to a foam material, and is effectively attenuated by utilizing the attenuation at the time of reflection in the reflecting material. Correspondingly, it exhibits a large attenuation characteristic for electromagnetic waves on a specific polarization plane. In this embodiment, as shown in FIG. 22A, the polarization component E having an electric field in the width W direction of the shield case 2₀Does not absorb the electromagnetic wave absorber 30 so as to attenuate the polarization component E1 having an electric field in the vertical H direction of the shield case 2 to the polarization component E1'shown by the solid line as shown by the broken line in FIG. 22 (b). I'm arranging. That is, the target frequency f is applied to the electromagnetic wave having the polarization component E1 in the vertical H direction of the shield case 2.₀Since an unnecessary frequency component different from the above is contained to some extent, the unnecessary radiation is further reduced by absorbing and removing the unnecessary frequency component. FIG. 23 shows the results of measuring the electromagnetic waves radiated from the transmitting antenna T of the electromagnetic wave radar antenna AT of this embodiment and captured by the receiving antenna R with a frequency spectrum analyzer, and the target frequency f.₀It can be seen that the component of is projected and the other unnecessary frequency components are effectively attenuated. Further, since the frequency components radiated at a high level are discrete, the target frequency f can be, for example, by appropriately selecting the reception bandwidth on the receiving unit side.₀Different from f₀/ 2 frequency or 2f₀It is also possible to receive the frequency of and perform the necessary measurement processing. FIG. 24 is a waveform diagram obtained by receiving and amplifying the reflected wave of the electromagnetic wave radiated from the electromagnetic wave radar antenna AT of this embodiment in the antenna substrate 1 by the receiving unit 50. As can be seen from the figure, the target frequency f is extremely reduced because unnecessary frequency components are extremely reduced.₀It exhibits a substantially sinusoidal distortion-free attenuation waveform based on the above, and is accurately demodulated down to a minute amplitude. FIG. 25 shows the received waveform of the reflected wave by the electromagnetic wave object radiated from the electromagnetic wave radar antenna AT of this embodiment. As can be seen from the figure, since it is a received signal in which unnecessary frequency components are not superimposed, it has an excellent S / N ratio, and the base point, end point, and periodic fluctuation of the reflected wave RT can be clearly discriminated, and the peak point of the received waveform. (1st peak point, 2nd peak point, etc.) P can be easily identified, and accurate calibration and measurement can be performed. As described above, according to the received signal processing method of the electromagnetic wave probe of the present invention, it is possible to compensate for the distance fluctuation between the antenna and the ground surface, which is inevitable for the portable and portable spacecraft, by simple signal processing. Therefore, a stable depth image can be displayed regardless of the skill of the explorer, and precise measurement becomes possible.