Radar

The present invention relates to an in-vehicle radar device using millimeter waves, particularly a radar device that scans the beam direction within a predetermined angle range and detects a target from a received signal.

Conventionally, various in-vehicle radar devices using millimeter waves have been devised, and among these radar devices, a transmission beam is transmitted while scanning an antenna within a predetermined scanning angle range, and a reception signal reflected by a target is transmitted. There is an angle scanning radar device that detects the target with.

However, in the angle scanning radar device, since the transmission range of the transmission beam is fan-shaped, the detection range becomes wider as the distance from the own vehicle increases, and the detection range becomes narrower in the vicinity of the own vehicle.

As an angle scanning radar device that solves this problem, Patent Document 1 disposes of a plurality of antennas having slightly different directivity directions, and by changing the combination of antennas used for transmission and reception, a long distance and a short distance can be obtained. What sets the distance, is disclosed. Specifically, this radar device improves the azimuth resolution at a long distance by narrowing the transmission beam width by using a plurality of adjacent antennas, and the number of antennas is smaller than that of the antenna used for such a long distance detection. By widening the transmission beam width, the detection range at a short distance is widened.

<p><patcit num="1"><text>Japanese Unexamined Patent Publication No. 8-334557</text></patcit></p>

<p> However, the conventional general angle scanning radar device cannot detect a target outside the scanning angle range. For example, identifying whether the peak of the received signal detected at the outermost angle (the end of the scanning angle range) is due to a target existing in the angle direction or a target existing outside the range. Was difficult.</p><p> Further, the radar device described in Patent Document 1 must use a plurality of antennas, and when transmitting beam control is performed using these antennas, a switch group for control and a complicated control for controlling these switch groups. Processing must be done. Furthermore, since the antennas used for long-distance detection and short-distance detection are different, different operation controls must be performed for each.</p><p> Therefore, an object of the present invention is to provide a radar device that realizes long-distance detection and short-distance wide-angle detection with one antenna.</p>

<p> The present invention comprises a transmission beam forming means for forming a transmission beam to be transmitted from an antenna to the outside, a beam scanning means for scanning the transmission beam within a predetermined scanning angle range, and a reception obtained by reflecting the transmission beam on a target. In a radar device equipped with a reception detection means for detecting a target from a signal, the scanning angle range<u style="single">Central direction</u>For a target at X ° azimuth from to at least one end, the received signal strength for the transmitted beam transmitted at X ° azimuth is greater than the X ° azimuth.<u style="single">Central direction of scan angle range</u>Set to be lower than the received signal strength for at least one transmit beam on the side<u style="single">, The reception signal intensity by the transmission beam that catches the target at the center of the transmission beam for the plurality of transmission beams is set to the state where a plurality of transmission beams are duplicated with respect to the target. Is set to be weaker than the received signal strength of the transmitted beam that captures the target by shifting toward the center of the scanning angle range.</u>It is characterized by being.</p><p> In this configuration, the intensity of the received signal by the transmission beam in the scanning angle X ° direction for a target existing in a certain scanning angle (azimuth) X ° direction is higher than the intensity of the received signal.<u style="single">Central direction of scan angle range</u>A setting is made for each scanning angle to increase the intensity of the received signal by the transmitting beam in at least one scanning angle direction on the side. As a result, the scanning angle at which the peak of the received signal strength appears is larger than the scanning angle (azimuth) of the target.<u style="single">Central direction of scan angle range</u>Be on the side.</p><p> Further, the radar device of the present invention sets the intensity of the received signal with respect to the transmitted beam transmitted at the azimuth angle of X ° from the azimuth angle of X °.<u style="single">Central direction of scan angle range</u>It is characterized in that it is set to be lower than the received signal intensity for the transmitted beam adjacent to the transmitted beam transmitted at the azimuth angle of X ° on the side.</p><p> In this configuration, the intensity of the received signal by the transmission beam in the scanning angle X ° direction for a target existing in a certain scanning angle (azimuth) X ° direction is higher than the intensity of the received signal.<u style="single">Central direction of scan angle range</u>The intensity of the received signal from the transmission beam in the scanning angle direction adjacent to the side is set to be high for each scanning angle. As a result, with respect to the scanning angle (azimuth) of the target<u style="single">Central direction of scan angle range</u>The peak of the received signal strength appears at the azimuth angle adjacent to the side.</p><p> Further, the radar device of the present invention is a transmission beam forming means and has a scanning angle range.<u style="single">To the center of</u>It is characterized in that the antenna gain in each scanning angle direction is gradually lowered toward one end with respect to the antenna gain of.</p><p> In this configuration, when the target exists in a certain scanning angle direction, the target is more than the scanning angle direction.<u style="single">Central direction of scan angle range</u>The reception signal by the transmission beam transmitted in the scanning angle direction on the side is larger than the reception signal by the transmission beam transmitted in the scanning angle direction in which the target exists.</p><p> Further, the radar device of the present invention is a transmission beam forming means and has a scanning angle range.<u style="single">Central direction</u>It is characterized in that the width of the transmission beam in each scanning angle direction is gradually widened from the to one end.</p><p> In this configuration, the intensity of the transmitted wave in the beam direction can be distributed by the characteristics of only the antenna without weakening the intensity of the transmitted beam toward one end. Further, the farther the beam is, the wider the received signal can be obtained. As a result, the scanning angle at which the peak of the received signal appears is greater than the scanning angle (azimuth) of the target.<u style="single">Central direction of scan angle range</u>Be on the side.</p><p> Further, the radar device of the present invention is a reception detection means and has a scanning angle range.<u style="single">Central direction</u>It is characterized in that the received signal strength in each scanning angle direction is corrected so that the received signal strength gradually decreases toward one end with respect to the received signal strength of.</p><p> In this configuration, the received signal is controlled instead of controlling the transmitting beam as in each of the above configurations. As a result, the same result as in the case of controlling the transmission beam described above can be obtained. It is also possible to control the received signal in addition to controlling the transmitted beam, and by doing so, the difference in each scanning angle direction can be further clarified.</p><p> Further, the radar device of the present invention includes a storage means for storing a correspondence table or a relational expression between the azimuth angle of the target and the received signal strength, and the reception detecting means detects the scanning angle at which the received signal strength is maximized. It is characterized in that the detected scanning angle is applied to a correspondence table or a relational expression to detect the azimuth angle of the target.</p><p> In this configuration, the scanning angle of the maximum (peak) of the received signal strength and the azimuth angle of the target in that case are associated in advance, and the peak of the received signal strength is obtained from the scanning angle distribution of the obtained received signal strength. If detected, the azimuth of the target is detected.</p><p> Further, the radar device of the present invention is characterized in that the reception detection means interpolates the reception signal strength of each transmission beam to detect the maximum of the reception signal strength.</p><p> In this configuration, a more accurate peak position can be obtained by interpolating the received signals in each scanning angle direction that appear discretely due to the scanning angle resolution (for example, replacing them with a predetermined continuous function) and detecting the peaks. Be done.</p>

<p> According to the present invention, the peak of the received signal intensity appears on the center side of the scanning angle range rather than the actual scanning angle (azimuth) in which the target exists, so that the peak of the received signal strength appears at the end and near the end of the scanning angle range. The peak of the received signal strength by the target existing outside the scanning angle range appears within the scanning angle range. As a result, it is possible to detect a target outside the scanning angle range in which the transmitted beam is actually transmitted.</p><p> Further, according to the present invention, by making the transmission beam wider toward the end of the scanning angle range, it is possible to detect a target at a position farther outward from the end of the scanning angle range.</p><p> Further, according to the present invention, even by controlling the received signal intensity, the peak of the received signal by the target existing outside the scanning angle range is within the scanning angle range at the end and the vicinity of the scanning angle range. appear. As a result, it is possible to detect a target outside the scanning angle range in which the transmitted beam is actually transmitted.</p><p> Further, according to the present invention, by associating the scanning angle of the target with the scanning angle of the peak of the received signal strength regardless of whether it is inside or outside the scanning angle range, the target can be easily scanned from the peak of the received signal strength. The angle, that is, the orientation, can be detected.</p><p> Further, according to the present invention, by interpolating the received signal intensities of each scanning angle, the received signal intensities appearing discretely become continuous, and the scanning angle distribution of the received signal intensities becomes more precise. When the peak is detected by the scanning angle distribution of the received signal intensity, the orientation of the target can be detected more accurately.</p>

<figref num="1">It is a schematic block diagram which shows the structure of the radar apparatus of 1st Embodiment.</figref><figref num="2">It is a schematic diagram which shows the distribution of the received signal intensity by the transmission beam in each scanning angle direction.</figref><figref num="3">It is an antenna gain pattern figure which shows the relationship between an azimuth angle (scanning angle) and a relative antenna gain.</figref><figref num="4">It is a relationship diagram between the peak azimuth and the target azimuth of the received signal intensity when the transmission beam has the distribution shown in FIG.</figref><figref num="5">It is a figure which showed the relationship between the transmission beam azimuth and the received signal intensity corresponding to this when the target exists in the 0 ° direction.</figref><figref num="6">It is a figure which showed the relationship between the transmission beam azimuth and the received signal intensity corresponding to this when the target exists in the 5 ° direction.</figref><figref num="7">It is a figure which showed the relationship between the transmission beam azimuth and the received signal intensity corresponding to this when the target exists in the direction of 10 °.</figref><figref num="8">It is a figure which showed the relationship between the transmission beam azimuth and the received signal intensity corresponding to this when the target exists in the direction of 15 °.</figref><figref num="9">It is an antenna gain pattern figure which shows the relationship between the azimuth angle and the relative antenna gain in the 2nd Embodiment.</figref><figref num="10">It is a relationship diagram between the peak azimuth angle and the target azimuth angle of the received signal intensity when the transmission beam has the distribution shown in FIG.</figref><figref num="11">It is a figure which showed the relationship between the transmission beam azimuth and the received signal intensity corresponding to this when the target exists in the 0 ° direction.</figref><figref num="12">It is a figure which showed the relationship between the transmission beam azimuth and the received signal intensity corresponding to this when the target exists in the 5 ° direction.</figref><figref num="13">It is a figure which showed the relationship between the transmission beam azimuth and the received signal intensity corresponding to this when the target exists in the direction of 10 °.</figref><figref num="14">It is a figure which showed the relationship between the transmission beam azimuth and the received signal intensity corresponding to this when the target exists in the direction of 15 °.</figref><figref num="15">It is a figure which showed the relationship between the transmission beam azimuth and the received signal intensity corresponding to this when the target exists in the direction of 20 °.</figref><figref num="16">It is a schematic block diagram of the radar apparatus of 3rd Embodiment.</figref><figref num="17">It is a schematic block diagram which shows the other configuration of the radar apparatus of 3rd Embodiment.</figref><figref num="18">It is a conceptual diagram when the received signal strength is approximated by a quadratic function and interpolated.</figref>

The radar device according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 8. In this embodiment, an FM-CW radar device mounted on an automobile as a radar device will be described as an example. FIG. 1 is a schematic configuration diagram showing the configuration of the radar device of the present embodiment. The radar device of this embodiment includes a control unit 1, a VCO2, a coupler 3, a circulator 4, an antenna 5, a mixer 6, a low-pass filter (LPF) 7, an A / D converter 8, an antenna scanning mechanism 9, and a data processing unit 10. Be prepared. The data processing unit 10 includes an FFT processing unit 11, a peak detection unit 12, and a target detection unit 13.

The control unit 1 sequentially generates digital data of a modulated signal that modulates the transmission signal, and outputs a control voltage based on this digital data to VCO2. VCO2 changes the oscillation frequency according to the control voltage input from the control unit 1. As a result, the oscillation frequency of VCO2 is continuously FM-modulated, for example, in a triangular wave shape. The coupler 3 transmits the FM-modulated transmission signal to the circulator 4 side, and supplies a part of the transmission signal as a local signal to the mixer 6 at a predetermined distribution ratio. The circulator 4 transmits a transmission signal to the antenna 5 side, and also gives a reception signal from the antenna 5 to the mixer 6. The antenna 5 transmits the FM-modulated continuous wave transmission signal of VCO2 as a transmission beam having a predetermined spread. Further, the antenna 5 scans the transmitted beam by periodically changing the direction of the transmitted beam over a predetermined scanning angle range by the antenna scanning mechanism 9. In the following description, an example in which beam scanning is performed along the horizontal direction from the own vehicle is shown, and the scanning angle corresponds to an azimuth angle. At this time, the angular pitch at the center of the radiation direction of each transmission beam, that is, the resolution of the scanning angle is preset, and the distribution of the transmission beam intensity for each scanning angle is also preset.

2A and 2B are schematic views showing the distribution of the received signal intensity by the transmitted beam in each scanning angle direction, in which FIG. 2A is an overall view and FIG. 2B is a partially enlarged view. In FIG. 2, 501,502R to 505R, 502L to 505L show the shape of the transmission beam and the shape of the received signal intensity distribution obtained from the transmission beam. Here, the received signal intensity by the transmitted beam indicates the received signal intensity obtained by transmitting the transmitted beam to a target at the same distance from the own vehicle in the azimuth direction (scanning angle direction), respectively.

FIG. 3 is an antenna gain pattern diagram showing the relationship between the azimuth angle (scanning angle) and the relative antenna gain. Here, the azimuth angle indicates the angle formed by the central direction of the scanning angle range of the antenna 5 in the 0 ° direction and the 0 ° direction. The azimuth is such that the right side when viewed from the own vehicle in the radial direction is the direction in which the angle is +, and the left side is the direction in which the angle is-.

The transmitted beam is set so that the received signal intensity of the transmitted beam in the central direction of the scanning angle range is stronger than the received signal intensity of the transmitted beam in the other scanning angle direction, and the edge from the central direction of the scanning angle range. It is set so that the intensity of the received signal by the transmitted beam gradually weakens toward the part. For example, as shown in FIG. 2, in the region on the right side in the radial direction, the reception intensity of the transmitted beam in the central direction is 501, and the reception intensity in each scanning angle direction from the center direction to the end is 502R, 503R, 504R. , 505R is set to become weaker in order. Further, in the region on the left side in the radiation direction, the reception intensities 502L, 503L, 504L, and 505L in each scanning angle direction are set to be weaker in order from the center direction to the end with respect to the reception intensity 501 of the transmission beam in the center direction. Has been made.

Then, between adjacent transmission beams, for example, when a target exists in the X ° direction and the scanning angle pitch is y °, the intensity of the received signal in the X ° direction by the transmission beam transmitted in the X ° direction is higher. , The intensity of the received signal in the X ° direction by the transmitted beam transmitted in the X ° -y ° direction adjacent to the center side is set to be stronger. For example, as shown in FIG. 2, when there is another target vehicle 100 in the central direction of the transmission beam 505R, the transmission beam by the transmission beam 504R is higher than the reception intensity 551R in the center direction of this transmission beam by the transmission beam 505R. The received signal strength 542R in the center direction of the 505R is set to be stronger.

This is specifically shown in FIG. 3, and in the case of FIG. 3, the scanning angle resolution is 1 °. In the setting shown in Fig. 3, the received signal intensity by the transmitted beam centered in the 0 ° direction is higher than the received signal intensity by the transmitted beam centered in the + 1 ° direction with respect to the target in the + 1 ° direction. It is set high. This relationship (distribution) is set to be the same even if the scanning angle increases from the center (0 ° direction) of the scanning angle range to the + 15 ° direction at the end. Then, for the target in the + 15 ° direction, which is one end of the scanning angle range, the reception signal is received by the transmission signal centered in the + 14 ° direction rather than the received signal intensity by the transmission beam centered in the + 15 ° direction. The signal strength is set higher. In the setting of FIG. 3, the distribution for the scanning angle in the + angular direction (right side direction) is shown, but the distribution for the scanning angle in the-angle direction (left side direction) is also the same. Then, the distribution in the + angular direction and the distribution in the-angular direction do not have to be exactly the same, and may be only in one direction (+ angular direction or-angular direction).

By using such a setting, the relationship between the peak scanning angle of the received signal strength and the target azimuth as shown in FIG. 4 can be obtained. FIG. 4 is a diagram showing the relationship between the peak scanning angle of the received signal strength and the target azimuth. As a result, the peak scanning angle of the received signal strength is deviated by 1 ° from the target azimuth to the center direction (0 ° direction) except for the center direction (0 ° direction).

The transmitted beam set in this way is reflected by the target and received by the antenna 5 as a reflected signal from the same direction. The antenna 5 outputs the received signal to the circulator 4, and the circulator 4 transmits the received signal to the mixer 6.

The mixer 6 mixes the local signal from the coupler 3 and the received signal from the circulator 4 to output an IF beat signal. The LPF 7 removes unnecessary high-frequency components from the IF beat signal, and the A / D conversion unit 8 converts the signal into a sampling data string and gives it to the FFT processing unit 11 of the data processing unit 10.

The FFT processing unit 11 performs FFT processing on the sampling data string converted by the A / D conversion unit 8 and gives it to the peak detection unit 12. The peak detection unit 12 detects the received signal intensity in each scanning angle direction by performing threshold processing on the FFT-processed data, and gives it to the target detection unit 13. The target detection unit 13 detects the azimuth angle of the target from the distribution of the received signal intensity in each scanning angle direction by the following method. At this time, the target detection unit 13 detects the relative distance and the relative speed from the own vehicle to the target by a known FM-CW method.

5 to 8 are diagrams showing the relationship between the transmission beam scanning angle and the corresponding received signal intensity when the target exists in each azimuth direction. The results of FIGS. 5 to 8 show the case where the transmission beam pattern shown in FIG. 3 is used for both transmission and reception. Here, FIG. 5 shows the case where the target exists in the 0 ° direction (the central direction of the scanning angle range), and FIG. 6 shows the case where the target exists in the + 5 ° direction. FIG. 7 shows the case where the target exists in the + 10 ° direction, and FIG. 8 shows the case where the target exists in the + 15 ° direction.

When the result of at least one scan of the transmitted beam is obtained, the target detection unit 13 detects the scanning angle distribution of the received signal intensity by using the received signal intensity detected by the peak detection unit 12. The data processing unit 10 stores in advance the azimuth angle of the target and the scanning angle distribution of the received signal strength corresponding thereto as shown in FIGS. 5 to 8 or is stored in advance as shown in FIG. The relationship between the target azimuth and the scanning angle of the maximum value of the received signal strength is stored in advance. Then, the target detection unit 13 detects the scanning angle direction in which the maximum received signal strength is taken from the scanning angle distribution of the received signal strength obtained by this scan, and the scanning angle at which the stored received signal strength becomes the maximum value. Read the relationship between the target and the azimuth of the target (Fig. 4), and compare these detection results with the stored information. Then, the target detection unit 13 detects the target azimuth based on the comparison result. For example, if a received signal intensity distribution having a maximum is obtained when the transmission beam azimuth angle as shown in FIG. 7 is 9 °, it is detected that a target exists in the 10 ° direction , and the transmission beam azimuth as shown in FIG. 8 is detected. If the received signal intensity distribution with the maximum is obtained when the angle is 14 °, it is detected that the target exists in the 15 ° direction.

As described above, in the present embodiment, the azimuth angle at which the target exists is the azimuth angle (scanning angle) on the side away from the center by 1 ° with respect to the scanning angle indicating the maximum of the received signal intensity distribution. By utilizing this relationship, a target existing at a position with an azimuth angle of 16 ° outside the scanning angle range can be detected when the maximum of the received signal strength appears at 15 °. Therefore, it is possible to detect a target outside the angle range in which the transmitted beam is actually scanned. That is, by using the above-described configuration of the present embodiment, it is possible to take a wide range of directions that can be detected at a short distance.

At this time, as described above, the received signal intensity of the transmission beam is set lower toward the end of the scanning angle range, so that it is not possible to detect a target existing at a long distance from the own vehicle in the end direction. , It is possible to detect a target that exists at a short distance.

On the other hand, in the central portion of the scanning angle range, substantially the same received signal strength as in the conventional case can be set, so that in the central portion, a target existing at a long distance from the own vehicle can be detected as in the conventional manner.

As a result, other vehicles existing near the center of the scanning angle range can be accurately detected up to a long distance, and other vehicles can be detected in a wide range in the vicinity of the own vehicle. Can be detected reliably and early.

In the above description, the azimuth angle of the target is detected from the maximum of the received signal strength in the scanning angle direction. However, by associating and storing the azimuth angle of the target and the distribution pattern of the received signal strength as shown in FIGS. 5 to 8, the detected reception signal strength distribution pattern and the stored reception It is also possible to detect the azimuth angle of the target by comparing it with the distribution pattern of the signal strength. In the method using such a distribution pattern, a different distribution pattern can be obtained for each azimuth angle of the target, so that the azimuth angle of the target can be uniquely determined.

Next, the radar device according to the second embodiment will be described with reference to FIGS. 9 to 15. The radar device of the present embodiment has the same configuration as the radar device shown in the first embodiment, and the transmission beam control method and the peak detection method associated therewith are different. Therefore, the description of each component is omitted, and only the transmission beam control method and the peak detection method will be described below.

FIG. 9 is an antenna gain pattern diagram showing the relationship between the azimuth angle and the relative antenna gain in the present embodiment. Here, the azimuth angle and the scanning angle indicate the angle formed by the central direction of the scanning angle range of the antenna 5 in the 0 ° direction and the 0 ° direction. The azimuth is such that the right-hand direction when viewed from the own vehicle in the radial direction is the direction in which the angle is +, and the left-hand direction is the direction in which the angle is-. The scanning angle resolution is 1 °.

The transmission beam is set so that the reception intensity of the transmission beam in the central direction of the scanning angle range is stronger than the reception intensity of the transmission beam in the other scanning angle directions, and the reception intensity is from the center direction to the end direction of the scanning angle range. It is set so that the intensity of the received signal by the transmission beam gradually weakens toward the end. Further, the transmission beam is set so that the transmission beam width gradually increases from the center direction to the end direction of the scanning angle range.

For example, in the example of FIG. 9, the beam width of the transmission beam in the 0 ° direction is about ± 3 °, which is about 6 °, but the larger the scanning angle, the wider the beam width, which is the edge of the scanning angle range. The beam width of the transmitted beam in the 15 ° direction extends to 20 ° or more. As a result, the transmitted beam in the + 15 ° direction is reflected even by the target having an azimuth angle of + 25 °, and the received signal is obtained.

By using such a setting, the relationship between the peak scanning angle of the received signal strength and the target azimuth as shown in FIG. 10 can be obtained. FIG. 10 is a diagram showing the relationship between the peak scanning angle of the received signal intensity and the target azimuth when the transmitted beam has the distribution shown in FIG. As shown in FIG. 10, the peak scanning angle of the received signal intensity is substantially deviated from the target azimuth toward the center (0 ° direction) except for the 0 ° direction. For example, when the target azimuth angle is 5 °, the peak scanning angle of the received signal strength is 4 °, and when the target azimuth angle is 20 °, the peak scanning angle of the received signal strength is 13 °. If the peak scanning angle of the received signal strength is 15 °, the target azimuth is 22 °. In this way, by using the transmission beam control method of the present embodiment, it is possible to detect the orientation of a target existing in a range of approximately ± 22 ° simply by actually scanning the transmission beam at ± 15 °. Is.

On the other hand, FIGS. 11 to 15 are diagrams showing the relationship between the transmission beam scanning angle and the corresponding received signal intensity when the target exists in each azimuth direction. The results of FIGS. 11 to 15 show the case where the transmission beam pattern shown in FIG. 9 is used for both transmission and reception. Here, FIG. 11 shows the case where the target exists in the 0 ° direction (the central direction of the scanning angle range), and FIG. 12 shows the case where the target exists in the + 5 ° direction. FIG. 13 shows the case where the target exists in the + 10 ° direction, and FIG. 14 shows the case where the target exists in the + 15 ° direction. In addition, FIG. 15 shows the case where the target exists in the + 20 ° direction.

In the radar device of the present embodiment, the data processing unit 10 stores in advance whether the azimuth angle of the target as shown in FIGS. 11 to 15 and the scanning angle distribution of the received signal intensity corresponding thereto are associated and stored in advance. The relationship between the target azimuth as shown in FIG. 10 and the scanning angle of the maximum value of the received signal strength is stored in advance. Then, the target detection unit 13 detects the scanning angle direction in which the maximum received signal strength is taken from the scanning angle distribution of the received signal strength obtained by this scan, and the scanning angle at which the stored received signal strength becomes the maximum value. The relationship between and the target azimuth (Fig. 4) is read out, and these detection results are compared with the stored information. Then, the target detection unit 13 detects the target azimuth based on the comparison result. For example, if a received signal intensity distribution having a maximum is obtained when the transmission beam scanning angle is 8 ° as shown in FIG. 13, it is detected that a target exists in the 10 ° direction, and the transmission beam scanning as shown in FIG. 14 is detected. If the received signal intensity distribution with the maximum is obtained when the angle is 11 °, it is detected that the target exists in the 15 ° direction. Furthermore, if a received signal intensity distribution having a maximum is obtained when the transmission beam scanning angle is 13 ° as shown in FIG. 15, it is detected that the target exists in the 20 ° direction.

As described above, in the present embodiment, the azimuth angle in which the target exists is on the side away from the center with respect to the azimuth angle indicating the maximum of the received signal intensity distribution. As a result, as in the case of FIG. 15, it is possible to detect a target outside the angle range in which the transmitted beam is actually scanned. That is, by using the above-described configuration of the present embodiment, it is possible to take a wide range of detectable directions at a short distance. Then, in the present embodiment, by setting the transmission beam width toward the end of the scanning angle range, it is possible to detect a wider range than the method shown in the first embodiment.

On the other hand, in the central portion of the scanning angle range, by setting substantially the same transmission beam width as in the conventional and first embodiments, it is possible to detect a target existing at a long distance from the own vehicle in the central portion as before. it can.

As a result, other vehicles existing near the center of the scanning angle range can be accurately detected up to a long distance, and other vehicles can be detected in a wider range in the vicinity of the own vehicle, resulting in a sudden interruption. Other vehicles and the like can be detected reliably and even earlier.

In the above description, the azimuth angle of the target is detected from the scanning angle at which the received signal strength is maximized. However, by associating and storing the target azimuth and the scanning angle distribution pattern of the received signal strength as shown in FIGS. 11 to 15, the scanning angle distribution pattern of the detected received signal strength and the scanning angle distribution pattern are stored. The azimuth angle of the target can be detected by comparing it with the distribution pattern of the received signal strength. In the method using such a distribution pattern, a different distribution pattern can be obtained for each azimuth angle of the target, so that the azimuth angle of the target can be uniquely determined.

Next, the radar device according to the third embodiment will be described with reference to FIGS. 16 and 17. FIG. 16 is a schematic configuration diagram of the radar device of this embodiment. The radar device of the present embodiment has a VGA (Variable Gain Amplifier) 15 installed between the mixer 6 and the LPF 7 with respect to the radar device shown in FIG. 1 of the first embodiment. The configuration is the same.

VGA15 is an amplifier that can control the gain. The scanning angle information of the transmission beam is given to the VGA 15 from the antenna scanning mechanism 9, and the VGA 15 changes the amplification factor of the IF beat signal output from the mixer 6 based on this scanning angle information. As a result, it is possible to control the relative antenna gain with respect to the azimuth angle as shown in FIG. 3 without controlling the intensity of the transmitted beam. The IF beat signal whose gain has been adjusted in this way is digitally converted by the A / D conversion unit 8 via the LPF 7 and given to the data processing unit 10 as in the first embodiment. The data processing unit 10 processes the input data to detect the target as shown in the first embodiment.

With such a configuration, other vehicles existing near the center of the scanning angle range can be accurately detected up to a long distance without controlling the intensity by the scanning angle of the transmission beam, and the area near the own vehicle is wide. Other vehicles can be detected within the range.

Although FIG. 16 shows a configuration in which the VGA 15 is installed between the mixer 6 and the LPF 7, as shown in FIG. 17, the FFT processing unit 11 and the peak detection unit 12 of the data processing unit 10 do not use the VGA 15. A level correction unit 14 may be installed between the two.

FIG. 17 is a schematic configuration diagram showing another configuration of the radar device of the present embodiment. In the case of this configuration, the IF beat signal from the transmission beam whose intensity is not controlled in the scanning angle direction is obtained and FFT processing is performed. The level correction unit 14 corrects the level of the FFT-processed data based on the scanning angle information of the transmission beam input from the control unit 1. As a result, it is possible to control the relative antenna gain with respect to the azimuth angle as shown in FIG. 3 without controlling the intensity of the transmitted beam.

In this way, it is not limited to controlling the transmission beam intensity by the scanning angle, but by adjusting and correcting the intensity of the received signal and received data in each circuit element of the receiving system, it exists near the center direction of the scanning angle range. In addition to accurately detecting a vehicle over a long distance, it can detect other vehicles in a wide range in the vicinity of the own vehicle.

In the above description of the present embodiment, the case where the scanning angle of the transmitted beam intensity is not controlled is shown, but the reception signal and the received data are adjusted / corrected while the scanning angle of the transmitted beam intensity is controlled. You may go.

Further, in each of the above-described embodiments, an example in which the azimuth angle having the highest reception intensity is arranged so as to be the center of the scanning angle range is shown, but the scanning angle range corresponds to the installation position and the number of installations of the radar device. It may be set so that the received signal strength in the direction other than the center of is maximized. For example, when two radars are installed on both sides of the front of the vehicle, the left radar is set so that the received signal strength in the direction to the right of the center of the scanning angle range is maximized, and the right radar is set to maximize the scanning angle range. Set so that the received signal strength in the direction to the left of the center is maximized. Further, in the method shown in the third embodiment, the received signal intensity distribution of the radar can be corrected by the level correction unit 14, and this correction can be made different depending on the conditions. Therefore, for example, the maximum reception intensity point in the scanning angle range can be switched according to the steering angle of the vehicle, and the detectable range of the target can be changed at any time.

Further, in each of the above-described embodiments, the peak scanning angle is detected from the measured values of the discrete received signal intensities based on the scanning angle pitch, but the peak scanning angle is interpolated by interpolating the distribution of the obtained received signal intensities. May be detected. For example, FIG. 18 is a conceptual diagram in which the received signal strength is approximated by a quadratic function and interpolated. In this case, the scanning angle of the peak is detected from the received signal strength curve represented by the approximate expression. Here, as the scanning angle of the detected peak, the scanning angle closest to the peak angle obtained from the curve represented by the approximate expression is adopted. Then, using the scanning angle detected in this way, the azimuth angle of the target is detected by the method shown in the first embodiment described above. By using such a method, it is possible to correct the variation in the received signal intensity for each scanning angle, and it is possible to detect a more appropriate peak scanning angle. As an interpolation method, in addition to the above-mentioned approximation by the quadratic function, approximation by another function, smoothing (moving average), and a plurality of points by the received signal strength and the corresponding scanning angle are acquired. A method of finding the center of gravity or the like can also be used.

1-Control unit 2-VCO 3-Coupler 4-Circulator 5-antenna 6-mixer 7-LPF 8-A / D converter 9-Antenna scanning mechanism 10-Data processing unit 11-FFT processing unit 12-Peak detector 13-Target detector 14-Data correction section 15-VGA