Dual band antenna with increased sensitivity in a horizontal direction

Dual-band antenna with good horizontal sensitivity

Technical field

The present invention relates to a small dual-band antenna that can transmit and receive signal waves in two frequency bands (wavebands), and is suitable for installation in a vehicle-mounted communication device or the like.

Background technique

In the past, as a dual-band antenna suitable for miniaturization, an inverted-F antenna capable of resonating at two frequencies, high and low, has been proposed by providing a cutout on the transmitting conductor plate (for example, refer to Patent Document 1).

Fig. 5 is an explanatory diagram showing the past example. The inverted F-shaped dual-band antenna 1 shown in the figure has a rectangular cutout 4 formed on the radiating conductor plate 2 and includes: an L-shaped conductor plate 2a that resonates with the first frequency f1, and a frequency higher than the first frequency f1. The rectangular conductor plate 2b that resonates at the second frequency f2. One end of the radiating conductor plate 2 is connected to the connecting conductor plate 3, and the connecting conductor plate 3 is erected on the grounding conductor plate 5, so that the radiating conductor plate 2 and the grounding conductor plate 5 are short-circuited. The entire surface of the radiating conductor plate 2 is opposed to the ground conductor plate 5 at a predetermined interval (the height dimension of the connecting conductor plate 3), and the power supply pin 6 is welded to a predetermined position of the radiating conductor plate 2. The power supply pin 6 is not in contact with the ground conductor plate 5, but is connected to an antenna circuit not shown.

In the conventional dual-band antenna 1 constructed roughly with this structure, the length along the extending direction of the L-shaped conductor piece 2a is set to approximately one-quarter of the harmonic length λ1 corresponding to the first frequency f1 First, the length dimension of the rectangular conductor plate 2b with a short extension is set to approximately one quarter of the resonance wavelength λ2 (but λ2<λ1) corresponding to the second frequency f2. Therefore, by supplying predetermined high-frequency power to the transmitting conductor plate 2 through the power supply pin 6, the conductor plates 2a and 2b can be made to resonate at different frequencies, and signal waves of two frequency bands with different levels can be received.

Patent Document 1: Japanese Patent Laid-Open No. 10-93332 (pages 2-3, Fig. 1).

In the conventional dual-band antenna 1 shown in FIG. 5, when resonating with the first frequency f1, the directivity of the radio wave emitted from the L-shaped conductor plate 2a becomes as shown in FIG. High gain can also be obtained in the horizontal direction. When resonating with the higher second frequency f2, the directivity of the radio waves emitted from the rectangular conductor plate 2b, as shown in Fig. 6B, is shifted upward, and the gain in the horizontal direction is low. . However, in-vehicle communication devices have many opportunities to transmit and receive signal waves propagating in the horizontal direction. Therefore, if the conventional dual-band antenna 1 is used as an in-vehicle communication antenna, the radio waves of the second frequency f2 may not be fully utilized. In particular, when the resonance frequency of the rectangular conductive plate 2b deviates from the second frequency f2 set in advance, the sensitivity is significantly reduced. However, in fact, sometimes the resonance frequency may deviate from the set value due to the influence of the bracket used for antenna installation. It is difficult to correct this deviation with the conventional dual-band antenna 1.

Summary of the invention

The present invention is a solution proposed in view of the actual situation of the above prior art, and its purpose is to provide a dual-band antenna that can obtain good sensitivity in the horizontal direction even in two wavebands with different heights.

In order to achieve the above-mentioned object, the dual-band antenna of the present invention includes: a support substrate having a ground conductor, a first radiating conductor plate arranged substantially in parallel with the ground conductor, and a lower end portion extending downward from the first radiating conductor plate A conductor plate for supplying high-frequency power at the first frequency, a connecting conductor plate that short-circuits the first radiating conductor plate and the ground conductor, and a second radiating conductor plate, the second radiating conductor plate being perpendicular to the ground conductor Stand up, the upper end is opposed to the lower surface of the first radiating conductor plate, and the lower end is supplied with high-frequency power at a second frequency higher than the first frequency, and the upper end of the second radiating conductor plate can be changed. The structure of the distance between the section and the first radiating conductor plate.

In the dual-band antenna of this structure, by supplying high-frequency power at the first frequency to the lower end of the power supply conductor plate, the first radiating conductor plate can be resonated as an inverted F antenna, so it is possible to obtain good horizontal gain The emission pattern. In addition, by supplying high-frequency power at the second frequency to the lower end of the second radiating conductor plate, the second radiating conductor plate can be resonated as a monopole antenna. Therefore, even if it resonates at either high or low frequency , Can also achieve good sensitivity in the horizontal direction. Furthermore, when the second radiating conductor plate resonates, the first radiating conductor plate facing the upper end has a capacitive load function. Therefore, the height of the second radiating conductor plate can be reduced, and the overall height of the antenna can be easily reduced. In addition, by changing the distance between the end of the second radiating conductor plate and the first radiating conductor plate, the degree of capacitive coupling between the two conductor plates can be changed. Therefore, the resonance frequency of the second radiating conductor plate can be easily and accurately adjusted.

Moreover, the structure in which the distance between the end of the second radiating conductor plate and the first radiating conductor plate can be changed can be equipped with synthetic resin adjusting screws. For example, a part of the second radiating conductor plate is provided with an elastic deformable portion and a composite The adjustment screw made of resin is tightened to the first radiating conductor plate, and the upper end of the second radiating conductor plate is pressed down. In this case, if the adjusting screw is tightened, the second radiating conductor plate will be separated from the first radiating conductor plate, and the resonance frequency will decrease. On the contrary, if the adjusting screw is loosened, the second radiating conductor plate will approach the first radiating conductor plate and resonate. The frequency becomes higher. In addition, the first and second radiating conductor plates are connected by adjusting screws to improve the mechanical strength. Therefore, it is not easily deformed even if it is subjected to external vibration and impact.

In addition, in order to be able to change the distance between the upper end of the second radiating conductor plate and the first radiating conductor plate, a structure may also be adopted in which the second radiating conductor plate is erected from a standing conductor portion that is erected on the support substrate, and The vertical conductor portion is configured by a sliding conductor portion that can slide in the vertical direction with respect to the vertical conductor portion, and has fixing means such as screws and nuts that connect the vertical conductor portion and the sliding conductor portion as a whole. In this case, by moving the sliding conductor part up and down with respect to the mounting position of the rising conductor part, the distance between the sliding conductor part and the first radiating conductor plate is changed, so that the resonance frequency of the second radiating conductor plate can be easily adjusted.

In a dual-band antenna in which the upper end of the second radiating conductor plate is bent in a direction substantially parallel to the first radiating conductor plate, it is preferable to increase the capacitance value between the upper end and the first radiating conductor plate.

Description of the drawings

Fig. 1 is a perspective view of a dual-band antenna according to an embodiment of the present invention.

Fig. 2 is a side view of the dual-band antenna.

Fig. 3 is a characteristic diagram showing the radiation pattern of the dual-band antenna.

Fig. 4 is a side view of a dual-band antenna according to another embodiment of the present invention.

Fig. 5 is a perspective view of a conventional dual-band antenna.

Fig. 6 is a characteristic diagram showing the radiation pattern of the dual-band antenna.

detailed description

Hereinafter, embodiments of the invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of a dual-band antenna according to an embodiment of the present invention, FIG. 2 is a side view of the dual-band antenna, and FIG. 3 is a characteristic diagram showing a radiation pattern of the dual-band antenna.

The dual-band antenna 10 shown in Figures 1 and 2 is a small antenna. Its structure is: a metal conductor plate (such as a copper plate) is stamped into a predetermined shape and then placed on the ground conductor 11, which is supporting A conductor layer such as copper foil is provided on almost the entire surface of the substrate 30, and this antenna is used as an inverted F antenna and a monopole antenna. The dual-band antenna 10 has: a first radiating conductor plate 12 arranged in parallel with the ground conductor 11, an elongated power-supply conductor plate 13 extending downward from two appropriate locations of the first radiating conductor plate 12, and connections Conductor plate 14, a second radiating conductor plate 15 having an elastic deformable portion 15a bent into a "U" shape and erected under the first radiating conductor plate 12, and an adjusting screw 16 made of synthetic resin, which is tightened Go to the approximate center of the first radiating conductor plate 12 and press the upper end of the second radiating conductor plate 15 downward.

The lower end of the power supply conductor plate 13 and the lower end of the second radiating conductor plate 15 are respectively connected to feeders not shown such as coaxial cables, and the high-frequency power of the first frequency f1 can pass through the power supply conductor plate 13 The high-frequency power of the second frequency f2 that is supplied to the first radiating conductor plate 12 and the frequency f1 is higher than the first frequency f1 can be supplied to the second radiating conductor plate 15. In addition, the size and shape of the first radiating conductor plate 12 are set so as to resonate with the first frequency f. Similarly, the size and shape of the second radiating conductor plate 15 are set to resonate with the second frequency f2. The upper end of the second radiating conductor plate 15 is provided with a receiving portion 15b bent in a direction substantially parallel to the first radiating conductor plate 12, and the receiving portion 15b is capacitively coupled with the first radiating conductor plate 12. When the radiating conductor plate 15 resonates, the first radiating conductor plate 12 becomes a capacitive load and has the same function as a shortening capacitor.

Furthermore, the power supply conductor plate 13 and the second radiating conductor plate 15 are provided in an area not in contact with the ground conductor 11, and the lower end of the connecting conductor plate 14 is welded to the ground conductor 11. Therefore, the first radiating conductor plate 12 is connected The conductor plate 14 and the ground conductor 11 are short-circuited. The connecting conductor plate 14 is formed by selecting an optimal position that can avoid impedance mismatch.

The dual-band antenna 10 configured in this way can resonate the first radiating conductor plate 12 as an inverted F-shaped antenna by supplying the high-frequency power of the first frequency f1 to the power feeding conductor plate 13. At this time, the directivity of the radio wave emitted by the first transmitting conductor plate 12 that resonates with the frequency f1 becomes the radiation pattern shown in FIG. 3A, and a high gain can be obtained in the horizontal direction. Furthermore, by supplying high-frequency power at the second frequency f2, the second radiating conductor plate 15 can be resonated as a monopole antenna. At this time, the directivity of the radio waves radiated by the second radiating conductor plate 15 that resonates with the frequency f2 becomes With the emission pattern shown in Fig. 3B, high gain can also be obtained in the horizontal direction.

Furthermore, when the second radiating conductor plate 15 resonates, the first radiating conductor plate 12 facing the upper end portion (receiving portion 15b) has a capacitive load function, so the height dimension of the second radiating conductor plate 15 can be reduced. It is easy to reduce the overall height of the antenna, and by tightening or loosening the adjustment screw 16, the distance between the receiving portion 15b and the first transmitting conductor plate 12 is changed to change the degree of capacitive coupling. Therefore, the second transmitting can be adjusted simply and accurately. The resonant frequency of the conductor plate 15. Specifically, when the adjusting screw 16 is tightened, the slightly "U"-shaped elastic deformation portion 15a is bent, and the receiving portion 15b is lowered. Therefore, the second radiating conductor plate 15 is separated from the first radiating conductor plate 12 and the capacitor The degree of coupling is weakened, and the resonance frequency is reduced accordingly. In contrast, if the adjusting screw 16 is loosened in the reverse direction, the receiving portion 15b rises due to the elastic force of the elastic deformation portion 15a, so that the second transmitting conductor plate 15 approaches the first transmitting conductor plate 12, which increases the degree of capacitive coupling and resonates The frequency increases accordingly.

Furthermore, the first and second radiating conductor plates 12 and 15 are in a connected state by the adjusting screw 16. Therefore, the mechanical strength of both the radiating conductor plates 12 and 15 is improved, and they are not easily deformed even if they are subjected to external vibration and impact. Therefore, the dual-band antenna 10 can achieve good horizontal sensitivity even when resonating at any of two frequencies with different heights, and is also highly resistant to vibration and shock, and can be applied to in-vehicle communication devices. Antenna performance.

Furthermore, as shown in this embodiment, if the upper end portion (receiving portion 15b) of the second radiating conductor plate 15 is opposed to the approximate center of the first radiating conductor plate 12, the second radiating conductor plate 15 will move upward when resonating. The directivity is weakened and the directivity in the horizontal direction is enhanced, so it is helpful to improve the sensitivity in the horizontal direction.

Fig. 4 is a side view of a dual-band antenna according to another embodiment of the present invention. Parts corresponding to Figs. 1 and 2 are denoted by the same reference numerals, and the description thereof is omitted.

The dual-band antenna 20 shown in FIG. 4 has a structure of the second radiating conductor plate 21 that resonates as a monopole antenna, which is very different from the above-mentioned embodiment. That is, in this embodiment, the second radiating conductor plate 21 is composed of a rising conductor portion 21a that is erected on the support substrate 30 and a slightly L that can slide in the vertical direction with respect to the rising conductor portion 21a. A zigzag-shaped sliding conductor portion 21b is formed, and these rising conductor portions 21a and sliding conductor portions 21b are integrally connected by a fixing device constituted by a bolt 22 and a nut 23. In addition, any through holes for bolts 22 that are not shown in the figures and penetrated through the standing conductor portion 21a and the sliding conductor portion 21b are long holes extending in the up-down direction. Therefore, by moving the sliding conductor portion 21b up and down with respect to the mounting position of the rising conductor portion 21a, the degree of capacitive coupling depending on the distance between the sliding conductor portion 21b and the first radiating conductor plate 12 can be changed, which is as easy as the above-mentioned embodiment. The resonant frequency of the second radiating conductor plate 21 is adjusted.

Moreover, in the case of the dual-band antenna 20, it is also possible to increase the first by installing synthetic resin screw parts, screwing it to the first radiating conductor plate 12, and pressing down the upper end of the sliding conductor part 21b. And the mechanical strength of the second radiating conductor plates 12, 21.

In addition, in each of the above-mentioned embodiments, the upper ends of the second radiating conductor plates 15 and 21 are bent in a direction substantially parallel to the first radiating conductor plate 12. However, the upper ends of the second radiating conductor plates 15 can be bent without bending. , 21 is used as a monopole antenna. However, if the upper end portion is bent, the capacitance value with the first radiating conductor plate 12 increases, the resonance frequency is easily adjusted, and the antenna height can be easily reduced.

Effects of the Invention The present invention is implemented in the manner described above, and the following effects can be obtained.

Because the dual-band antenna can resonate the first radiating conductor plate as an inverted F antenna, and at the same time, it can resonate the second radiating conductor plate as a monopole antenna, so when resonating at one of two different frequencies, high and low , Can also achieve good sensitivity in the horizontal direction. Furthermore, when the second radiating conductive plate resonates, the first radiating conductive plate facing the upper end has a capacitive load function. Therefore, the height of the second radiating conductive plate can be reduced, and the overall height of the antenna can be easily reduced. In addition, by changing the distance between the end of the second radiating conductor plate and the first radiating conductor plate, the degree of capacitive coupling between the two conductor plates can be changed. Therefore, the resonance frequency of the second radiating conductor plate can be easily and accurately adjusted.