JP6268512B2 - Antenna device - Google Patents

Description

  The present invention relates to an antenna device, and more particularly to an antenna device applicable to a monopulse radar device or the like.

  2. Description of the Related Art Conventionally, there is a monopulse radar device for the purpose of azimuth detection (see, for example, Patent Document 1). According to the monopulse radar device, a reflected wave from a detection target is received by a plurality of antenna elements arranged on a substrate at a predetermined interval, and the phase difference or amplitude of the received signal received by each antenna element. The azimuth angle of the detection target is specified from the difference. In general, a planar antenna is used in this type of radar apparatus.

  FIG. 13 is a diagram for explaining a conventional antenna device (planar antenna) 100 used in a monopulse radar device. FIG. 13A shows a configuration of the conventional antenna device 100, and FIG. Indicates the antenna characteristics (relationship between azimuth angle θ and phase difference θd). As shown in FIG. 13A, the antenna device 100 includes a substrate 110, antenna elements 120 and 130 formed on the main surface of the substrate 110, and a ground plate 160 formed on the back surface of the substrate 110. Yes.

  According to the antenna device 100, ideally, as indicated by a solid line in FIG. 13B, the relationship between the phase difference θd between the received signals received by the antenna elements 120 and 130 and the azimuth angle θ of the detection target. The antenna characteristic indicating is represented by a curve without fluctuation. Based on this antenna characteristic, the azimuth angle θ of the detection target can be specified from the phase difference θd between the received signals.

JP 2006-145444 A

  However, according to the conventional antenna device 100 described above, there is a problem that the antenna characteristics are deteriorated by the diffracted wave WD generated at the end of the substrate 110 on which the antenna elements 120 and 130 are formed.

  Specifically, the radio waves transmitted from the antenna elements 120 and 130 are reflected by the detection target, and the reflected waves are received by the antenna elements 120 and 130. At this time, a part of the reflected wave enters the end portion of the substrate 110 of the antenna device 100 and is diffracted at this end portion. When the reflected wave diffracted at the end of the substrate 110 is received as the diffracted wave WD by the antenna elements 120 and 130, the antenna characteristics deteriorate. Specifically, as indicated by a dotted line in FIG. 13B, the relationship between the phase difference θd between the received signals received by the antenna elements 120 and 130 and the azimuth angle θ of the detection target is shown. The characteristic line of the antenna characteristic fluctuates, and the characteristic line has a maximum value, a minimum value, or a flat portion.

  When fluctuation occurs in the characteristic line of the antenna characteristic in this way, a region corresponding to a plurality of azimuth angles θ with respect to the phase difference θd between the received signals received by the antenna elements 120 and 130 is generated, and the phase difference θd and The azimuth angle θ does not correspond one to one. For this reason, the receiving accuracy of the antenna device 100 is lowered, and it is difficult to specify the azimuth angle θ of the detection target from the phase difference θd between the received signals.

  As a conventional technique for solving the above problem, there is a technique disclosed in, for example, Japanese Patent Application Laid-Open No. 2006-145444 (Patent Document 1). In this prior art, the diffracted wave received by each patch antenna is canceled by setting the patch antenna arrangement interval to an odd multiple ± 1/4 wavelength which is half the wavelength of the radar transmission frequency. However, according to this prior art, there is a problem that the degree of freedom of the arrangement interval of the patch antennas is restricted.

  As another method, there is a method of enlarging the distance between the antenna element and the end portion of the substrate. According to this method, since the amplitude of the diffracted wave received by the antenna element is attenuated, deterioration of the antenna characteristics can be reduced. However, according to this method, there is a problem that it is difficult to reduce the size of the antenna device because the substrate is enlarged.

  Accordingly, one of the objects of the present invention is to provide an antenna device that can suppress deterioration of antenna characteristics caused by a diffracted wave generated at an end portion of a substrate on which an antenna element is formed.

An antenna device according to an aspect of the present invention includes a substrate, at least a pair of antenna elements disposed on the substrate, and an end portion of the substrate in the arrangement direction of the pair of antenna elements and the pair of antenna elements. And a choke portion formed to be a diffraction point of a reflected wave from the detection target .
According to this configuration, the choke portion functions as a diffraction point of radio waves and generates a diffracted wave. When the diffracted wave generated at the substrate end is received by the antenna element as a result of interference between the diffracted wave generated by the choke portion and the diffracted wave generated at the substrate end in the vicinity of the antenna element, It is attenuated by the diffracted wave generated in the part. As a result, a characteristic in which the phase difference between the radio waves respectively received by the pair of antenna elements and the azimuth angle (radio wave incident angle) of the detection target corresponds to the antenna characteristics on a one-to-one basis. For this reason, it becomes possible to identify the azimuth angle of the detection target from the phase difference between the reception signals received by each of the pair of antenna elements. Therefore, it is possible to suppress the deterioration of the antenna characteristics due to the diffracted wave generated at the end of the substrate on which the antenna element is formed, and to improve the reception accuracy.

  In the antenna device, for example, the choke portion includes a recess formed so as to extend in a direction substantially orthogonal to the arrangement direction of the pair of antenna elements. According to this configuration, the propagation wave between the end portion of the substrate and the antenna element is blocked by the choke portion. At this time, the choke portion generates a part of the propagation wave as a diffracted wave and functions as a diffraction point.

  In the antenna device, for example, the opening direction of the concave portion of the choke portion is set to be substantially parallel to the main surface of the substrate on which the antenna element is disposed. According to this configuration, a propagation wave between the end portion of the substrate and the pair of antenna elements enters the concave portion of the choke portion and is reflected. In this case, since the choke portion blocks the propagation wave between the end portion of the substrate and the antenna element, unnecessary waves incident on the antenna element can be suppressed. Further, since the choke portion functions as a diffraction point, the diffracted wave generated at the substrate end can be attenuated.

  In the antenna device, for example, the opening direction of the concave portion of the choke portion is set to be substantially perpendicular to the main surface of the substrate on which the antenna element is disposed. According to this configuration, a propagation wave between the end portion of the substrate and the pair of antenna elements enters the concave portion of the choke portion and is reflected. In this case, since the choke portion blocks the propagation wave between the end portion of the substrate and the antenna element, unnecessary waves incident on the antenna element can be suppressed. Further, since the choke portion functions as a diffraction point, the diffracted wave generated at the substrate end can be attenuated.

  In the antenna device, for example, an inclined surface is formed at an end portion of the substrate. For example, the inclined surface is a curved surface formed in a convex shape toward the outside of the substrate. According to this configuration, diffraction at the end portion of the substrate is relaxed. Thereby, the diffracted wave received by the antenna element is reduced.

  According to one embodiment of the present invention, deterioration of antenna characteristics due to diffracted waves generated at an end portion of a substrate over which an antenna element is formed can be suppressed.

It is a figure which shows the structural example of the antenna apparatus by 1st Embodiment of this invention. It is a 2nd page figure of the antenna device by a 1st embodiment of the present invention. It is the elements on larger scale of the antenna apparatus by 1st Embodiment of this invention, (A) shows the 1st example of a choke part, (B) is a figure which shows the 2nd example of a choke part. It is a figure for demonstrating the technical significance of the choke part with which the antenna apparatus by 1st Embodiment of this invention is provided, Comprising: It is a figure which shows an example of the relationship between the board | substrate width | variety of an antenna apparatus, and an antenna characteristic, (A) Shows the relationship between the azimuth angle and the phase difference when the substrate width is 15 mm, (B) shows the relationship between the azimuth angle and the phase difference when the substrate width is 50 mm, and (C) shows the substrate width. It is a figure which shows the relationship between an azimuth and a phase difference when is 100 mm. It is a figure which shows the example of a characteristic of the antenna apparatus by 1st Embodiment of this invention. It is a figure for demonstrating operation | movement of the choke part with which the antenna apparatus by 1st Embodiment of this invention is provided, (A) is a figure which shows the relationship between a choke part and an electric field, (B)-(D) These are figures which show the behavior of the electric field in a choke part. It is a figure which shows the structural example of the antenna device by 2nd Embodiment of this invention. It is a 2nd page figure of the antenna apparatus by 2nd Embodiment of this invention. It is the elements on larger scale of the antenna device by 2nd Embodiment of this invention, (A) shows the 1st example of the edge part of a board | substrate, (B) is a figure which shows the 2nd example of the edge part of a board | substrate. is there. It is a figure which shows the example of a characteristic of the antenna device by 2nd Embodiment of this invention. It is a figure which shows the structural example of the antenna apparatus by 3rd Embodiment of this invention. It is a figure which shows the example of a characteristic of the antenna device by 3rd Embodiment of this invention. It is a figure for demonstrating the conventional antenna apparatus, (A) shows the structure of the conventional antenna apparatus, (B) is a figure which shows the antenna characteristic.

Embodiments of the present invention will be described below with reference to the drawings.
<First Embodiment>
(Description of configuration)
FIG. 1 is a diagram illustrating a configuration example of the antenna device 10 according to the first embodiment of the present invention, and FIG. 2 is a two-view diagram (top view, side view) of the antenna device 10.

  The antenna device 10 includes a substrate 11, a plurality of pairs of antenna elements 12 and 13, and choke portions 14 and 15. On the main surface of the substrate 11, an antenna element array including a plurality of antenna elements 12 and an antenna element array including a plurality of antenna elements 13 are arranged in parallel. The plurality of antenna elements 12 and the plurality of antenna elements 13 form a pair. In the example of FIGS. 1 and 2, five pairs of antenna elements 12 and 13 are arranged on the substrate 11. However, the present invention is not limited to this example, and the antenna device 10 may include only a pair of antenna elements 12 and 13. For example, the number of antenna elements can be arbitrarily set according to the specifications of the radar apparatus. The plurality of antenna elements 12 are connected to a feeding point through a microstrip line. Similarly, the plurality of antenna elements 13 are also connected to the feed point through the microstrip line.

  In the present embodiment, the length of the substrate 11 in the arrangement direction of the antenna element 12 and the antenna element 13 that form a pair is defined as a substrate width WS (see FIG. 1). When a transmission / reception circuit unit (not shown) connected to the antenna device 10 is integrated with the antenna device 10, for example, the substrate width WS is set according to the size of the transmission / reception circuit unit.

The distance between the antenna element 12 and the antenna element 13 forming a pair, for example, is set to a distance corresponding to 1 (= λ _0/2) of the half-wave lambda ₀ in the free space. In this case, with respect to the azimuth angle of the detection target in the range of −90 ° to + 90 °, a phase difference in the range of −180 ° to + 180 ° is obtained as the phase difference between the reception signals received by the antenna elements 12 and 13. Can be obtained. Thereby, it is possible to know the azimuth angle of the detection target from the phase difference (or amplitude difference) of the received signals respectively received by the antenna elements 12 and 13.

  Choke portions 14 and 15 made of a conductive member are formed between the end portions EG1 and EG2 of the substrate 11 and the antenna elements 12 and 13 in the arrangement direction of the antenna element 12 and the antenna element 13 that form a pair. In the example of FIG. 1, a plurality of choke portions 14 are formed between the end portion EG1 of the substrate 11 and the antenna element 12, and a plurality of choke portions 15 are also formed between the end portion EG2 of the substrate 11 and the antenna element 13. Is formed. Details thereof will be described later. A ground plate 16 is formed on the back surface of the substrate 11 as necessary.

  3A and 3B are partial enlarged views of the antenna device 10 according to the first embodiment of the present invention. FIG. 3A shows a choke portion 15A according to a first example of the choke portion 15, and FIG. The choke part 15B which concerns on the 2nd example of this is shown. FIG. 3 shows only the configuration of the region on the antenna element 13 side from the midpoint between the antenna element 12 and the antenna element 13 among the components of the antenna device 10 shown in FIGS. 1 and 2. The structure of the area | region of the opposite side containing 12 and the choke part 14 is abbreviate | omitted.

In the following description, the choke unit 15 will be described. However, the choke unit 14 will be described in the same manner as the choke unit 15. It is the same as the arrangement relationship between the two.
As shown in FIGS. 1 to 3, the choke portion 15 (15A, 15B) has a recess (groove) formed so as to extend in a direction substantially perpendicular to the arrangement direction of the antenna elements 12, 13 forming a pair. Have.

  In the present embodiment, the opening direction of the concave portion of the choke portion 15A according to the first example illustrated in FIG. 3A is set so as to be substantially parallel to the main surface of the substrate 11 on which the antenna elements 12 and 13 are arranged. The Specifically, the choke portion 15 </ b> A is disposed on the substrate 11 so that the opening portion faces the antenna elements 12 and 13 of the substrate 11. Therefore, the choke portion 15A has a configuration in which a general choke structure is disposed on the substrate 11 sideways. In the case of the example shown in FIG. 3A, the attitude of the antenna device 10 is set so that the planes of polarization of radio waves transmitted and received by the antenna elements 12 and 13 are parallel to the paper surface of FIG. That is, the attitude of the antenna device 10 is set so that the planes of polarization of radio waves transmitted and received by the antenna elements 12 and 13 are substantially orthogonal to the main surface of the substrate 11 and substantially orthogonal to the longitudinal direction of the choke portion 15A. The Further, the attitude of the antenna device 10 is set so that the electric field direction of the radio wave transmitted and received by the antenna elements 12 and 13 is parallel to the depth direction of the groove of the choke portion 15A.

The arrangement position of the choke portion 15A is such that the end portion EG2 of the substrate 11 and the antenna element 13 are limited to the extent that the antenna characteristics are improved by receiving the diffracted wave generated in the choke portion 15A by the antenna elements 12 and 13. It is optional if it is between. Preferably, the choke portion 15 </ b> A is disposed at a position close to the antenna element 13.
The depth of the concave portion of the choke portion 15A h (length of the choke) is set to a quarter of a wavelength lambda ₀ of the radio wave (= lambda _0/4) propagating on the substrate 11, the recess bottom surface of the width w (chalk width) is set to less than one-half of one wavelength lambda _0. Thereby, the choke part 15A functions as a choke.

Further, the opening direction of the concave portion of the choke portion 15B according to the second example illustrated in FIG. 3B is set so as to be substantially perpendicular to the main surface of the substrate 11 on which the antenna element 13 is disposed. Similar to the first example of FIG. 3A, the arrangement position of the choke portion 15B is limited to the fact that the antenna characteristics are improved by receiving the diffracted waves generated in the choke portion 15B by the antenna elements 12 and 13. As long as it is between the edge part EG2 of the board | substrate 11 and the antenna element 13, it is arbitrary. Preferably, the choke portion 15B is disposed at a position close to the antenna element 13. The depth of the concave portion of the choke portion 15B h (length of the choke) is set to a quarter of a wavelength lambda ₀ of the radio wave (lambda _0/4) propagating, the width w of the bottom surface of the recess (chalk width) is set to less than one-half of one wavelength lambda _0. As a result, the choke portion 15B has a plane of polarization of radio waves transmitted and received by the antenna elements 12 and 13 in parallel with the paper surface of FIG. 3B in the same manner as the choke portion 15A, and the electric field direction is the groove of the choke portion 15B. Acts as a choke under conditions that are parallel to the depth direction.

Next, the technical significance of the choke unit 15 included in the antenna device 10 in the first embodiment will be described.
FIG. 4 is a diagram for explaining the technical significance of the choke portion 15 included in the antenna device 10 according to the first embodiment of the present invention, and an example of the relationship between the substrate width WS of the antenna device 10 and the antenna characteristics. FIG. FIG. 4A shows the relationship between the azimuth angle θ and the phase difference θd when the substrate width WS is 15 mm, and FIG. 4B shows the azimuth angle θ and the phase difference θd when the substrate width WS is 50 mm. FIG. 4C shows the relationship between the azimuth angle θ and the phase difference θd when the substrate width WS is 100 mm. Here, in FIG. 4, the characteristic indicated by the solid line indicates the characteristic when there is no influence of the diffracted wave, and the characteristic indicated by the dotted line indicates the experimental result. The azimuth angle θ is an angle indicating the direction in which the detection target exists. In the present embodiment, the azimuth angle θ is an angle that is based on an axis that is orthogonal to the main surface of the substrate 11 and passes through an intermediate point between the antenna element 12 and the antenna element 13 that make a pair. Further, the phase angle θd is a phase difference between reception signals received by the antenna element 12 and the antenna element 13 that form a pair.

  As illustrated in FIG. 4, the present inventor has a case where the antenna elements 12 and 13 and the end portions EG <b> 1 and EG <b> 2 of the substrate 11 are close to each other in the planar antenna (FIG. 4A). 13 and the end portions EG1 and EG2 of the substrate 11 are sufficiently separated (FIG. 4C), the fluctuation of the characteristic line of the antenna characteristic is reduced, and the azimuth angle θ and the phase difference θd are reduced. The experimental result that the relationship with the one-to-one relationship was obtained.

  In the example shown in FIG. 4, when the substrate width WS in which the antenna elements 12 and 13 and the end portions EG1 and EG2 of the substrate 11 are close is 15 mm, and between the antenna elements 12 and 13 and the end portions EG1 and EG2 of the substrate 11 The amplitude of the fluctuation of the phase difference θd with respect to the azimuth angle θ becomes the largest when the substrate width WS is 50 mm (FIG. 4B), compared with the case where the substrate width WS is sufficiently long. Yes.

  On the other hand, when the substrate width WS is 15 mm (FIG. 4A), that is, when the antenna elements 12 and 13 and the end portions EG1 and EG2 of the substrate 11 are close to each other, the phase difference θd that causes an error. The interval of fluctuations appearing in is wider than the range of the azimuth angle θ, and the number of fluctuations decreases. Thereby, the relationship between the azimuth angle θ and the phase difference θd becomes a one-to-one relationship, and the azimuth angle θ can be specified from the phase difference θd. When the substrate width WS is 100 mm (FIG. 4C), that is, when the distance between the antenna elements 12 and 13 and the end portions EG1 and EG2 of the substrate 11 is sufficiently large, Since the amplitude of the wave propagating to the parts EG1 and EG2 is attenuated, the amplitude of the diffracted wave is reduced. As a result, the number of fluctuations of the phase difference θd in the antenna characteristics increases, but the inclination of the fluctuations tends to decrease. Therefore, as in the case where the substrate width WS is 15 mm, the relationship between the azimuth angle θ and the phase difference θd becomes a one-to-one relationship, and the azimuth angle θ can be specified from the phase difference θd.

  As understood from the above experimental results, when the antenna elements 12 and 13 and the end portions EG1 and EG2 of the substrate are close to each other (FIG. 4A), or the antenna elements 12 and 13 and the end of the substrate When the distance between the parts EG1 and EG2 is sufficiently large (FIG. 4C), the influence of fluctuations appearing in the phase difference θd between the received signals in the antenna characteristics is reduced, and the azimuth angle θ from the phase difference θd. Can be specified. Therefore, it is possible to improve the antenna characteristics by adjusting the substrate width WS.

  However, there are circumstances in which it is not always possible to set the substrate width WS by giving priority to antenna characteristics. For example, when the antenna device 10 and a circuit unit (not shown) are integrated, the substrate width WS cannot be made smaller than the size of the circuit unit. Therefore, in this case, there is a possibility that the antenna elements 12 and 13 and the end portions EG1 and EG2 of the substrate 11 cannot be effectively brought close to each other in order to obtain the experimental result illustrated in FIG. On the contrary, if the distance between the antenna elements 12 and 13 and the end portions EG1 and EG2 of the substrate 11 is sufficiently separated in order to obtain the experimental results illustrated in FIG. The antenna device 10 is increased in size. Therefore, in this case, there is a possibility that the antenna elements 12 and 13 and the end portions EG1 and EG2 of the substrate 11 cannot be effectively separated.

  Therefore, the present inventor has found that the choke portions 14 and 15 are formed in a region between the antenna elements 12 and 13 and the end portions EG1 and EG2, and the choke portions 14 and 15 function as diffraction points. As a result, as in the case where the antenna elements 12 and 13 and the end portions EG1 and EG2 of the substrate 11 are brought close to each other (FIG. 4A), the phase difference θd between the received signals and the azimuth angle θ of the detection target Antenna characteristics having a one-to-one correspondence relationship. Therefore, the antenna characteristics can be improved without adjusting the substrate width WS of the substrate 11, and the azimuth angle θ of the detection target can be determined from the phase difference θd between the reception signals received by the pair of antenna elements 12 and 13. It becomes possible to specify.

(Description of operation)
Next, the operation of the antenna device 10 according to the first embodiment will be described.
Here, paying attention to the choke portion 15 shown in FIGS. 1 to 3, assuming that the choke portion 15 is the choke portion 15A shown in FIG. 3A, the operation when receiving the radio wave reflected from the detection target Will be explained.

  Reflected waves (radio waves) from the detection target are received at substantially the same incident angle with respect to the antenna element 12 and the antenna element 13. The reflected wave incident on the choke portion 15A disposed closer to the antenna elements 12 and 13 than the end portions EG1 and EG2 of the substrate 11 is diffracted by the choke portion 15A. That is, the choke unit 15A functions as a diffraction point of the reflected wave from the detection target and generates a diffracted wave. Then, when the reflected wave diffracted by the end portion EG2 of the substrate 11 is received by the antenna elements 12 and 13, the reflected wave diffracted by the end portion EG2 receives the interference of the reflected wave diffracted by the choke portion 15A. Is attenuated. As a result, the antenna characteristics of the antenna device 10 are the same as when the antenna elements 12 and 13 and the end portion EG2 of the substrate 11 are brought close to each other (FIG. 4A) and the phase difference θd between the received signals and the detection target. The azimuth angle θ has a one-to-one correspondence relationship.

FIG. 5 is a diagram illustrating a characteristic example of the antenna device 10 according to the first embodiment of the present invention.
In FIG. 5, the solid line indicates the conventional antenna characteristics without the choke portion 15A, and the dotted line and the alternate long and short dash line indicate the antenna characteristics when the choke portion 15A is provided. Among these, the dotted line indicates the antenna characteristics when the bottom surface width w of the recess of the choke portion 15A is 0.4 mm, and the alternate long and short dash line indicates the antenna when the bottom surface width w of the recess of the choke portion 15A is 0.8 mm. The characteristics are shown.

  As can be understood from the antenna characteristics illustrated in FIG. 5, the fluctuation of the phase difference θd in the antenna characteristics is improved by providing the choke portion 15A. In the example of FIG. 5, except for the case where the azimuth angle θ is around 0 °, the phase difference θd and the azimuth angle θ are in a one-to-one relationship. However, the characteristic in which the azimuth angle θ in the example of FIG. 5 is around 0 ° can also be improved by adjusting the choke portion 15A. Therefore, the azimuth angle θ of the detection target is specified from the phase difference θd between the received signals received by the antenna elements 12 and 13, and the antenna characteristics are deteriorated due to the diffracted waves generated at the end portions EG1 and EG2 of the substrate 11. It becomes possible to suppress.

  In the present embodiment, the choke portion 15A functions as an original choke, thereby blocking radio waves propagating on the substrate surface between the antenna elements 12, 13 and the end portions EG1, EG2 of the substrate 11. As a result, unnecessary waves received by the antenna elements 12 and 13 can be reduced, and the antenna characteristics can be further improved.

For reference, the choke operation will be supplementarily described using the choke portion 15B shown in FIG. 3B as an example.
FIG. 6 is a diagram for supplementarily explaining the operation of the choke unit 15B included in the antenna device 10 according to the first embodiment of the present invention. Here, FIG. 6A is a diagram showing the relationship between the choke portion 15B and the electric field E, and FIGS. 6B to 6D are diagrams showing the behavior of the electric field E in the choke portion 15B.

  In order for the choke portion 15B to function as an original choke, as shown in FIG. 6A, the direction of the electric field E relative to the choke portion 15B (that is, the direction of the polarization plane of the radio wave) is such that the depression ( It is necessary to be perpendicular to the extending direction of the groove) and parallel to the depth direction of the recess. In the choke portion 15B, as shown in FIG. 6B, the electric field of the propagating wave (solid line) that does not enter the concave portion of the choke portion 15B and the concave portion of the choke portion 15B are incident on the concave portion of the choke portion 15B. There is an electric field of a propagating wave (dotted line) reflected back from the bottom surface.

  Here, as shown in FIG. 6C, the phase of the electric field E of the propagating wave that has traveled straight without entering the recess of the choke portion 15B is maintained. On the other hand, as shown in FIG. 6D, the phase of the electric field E incident on the concave portion of the choke portion 15B rotates 180 ° at the short-circuit end of the concave portion of the choke portion 15B. For this reason, as shown in FIG. 6B, the electric field of the propagating wave that has traveled straight without entering the concave portion of the choke portion 15B and the electric field of the propagating wave that has entered and returned to the concave portion of the choke portion 15B cancel each other. Fit. Thereby, the electric field on the board | substrate 11 is reduced and the electromagnetic wave which propagates the board | substrate surface by the choke part 15B is interrupted | blocked. The operation of the choke portion 15A shown in FIG. However, in the present embodiment, in the course of the operation as such a choke, the diffraction generated by the choke portion 15 (15A, 15B) when the reflected wave from the detection target enters the choke portion 15 (15A, 15B). The antenna characteristics are improved by suppressing the diffracted waves generated at the end portions EG1 and EG2 of the substrate 11 using the waves.

  Although the first embodiment has been described above, according to the present embodiment, the choke portions 14 and 15 functioning as diffraction points are provided between the antenna elements 12 and 13 and the end portions EG1 and EG2 of the substrate 11. An effect similar to that obtained when the distance between the antenna elements 12, 13 and the end portions EG1, EG2 of the substrate 11 is shortened can be obtained. As a result, antenna characteristics are obtained in which the phase difference θd between the received signals respectively received by the antenna elements 12 and 13 and the azimuth angle θ of the detection target have a one-to-one correspondence. Therefore, it is possible to suppress the deterioration of the antenna characteristics due to the diffracted waves generated at the end portions EG1 and EG2 of the substrate 11 without affecting the dimensions (size) and arrangement form of the antenna device, and to improve the reception accuracy. Can be improved.

Second Embodiment
Next, a second embodiment of the present invention will be described.
FIG. 7 is a diagram illustrating a configuration example of the antenna device 20 according to the second embodiment of the present invention, and FIG. 8 is a two-view diagram of the antenna device 20 according to the second embodiment of the present invention.

  The antenna device 20 according to the second embodiment includes a substrate 21 instead of the substrate 11 in the configuration of the antenna device 10 according to the first embodiment described above. The end portions EG1 and EG2 of the substrate 21 are formed with inclined surfaces for relaxing diffraction of radio waves incident on the end portions EG1 and EG2 of the substrate 21. In the second embodiment, the inclined surfaces formed on the end portions EG <b> 1 and EG <b> 2 of the substrate 21 are curved surfaces formed in a convex shape toward the outside of the substrate 21. However, it is not limited to this example, For example, the inclined surface formed in edge part EG1, EG2 of the board | substrate 21 may have a polygonal shape.

  FIG. 9 is a partially enlarged view of the antenna device 20 according to the second embodiment of the present invention. FIG. 9A shows a first example of the end portion EG2 of the substrate 21, and FIG. 9B shows the end portion of the substrate 21. It is a figure which shows the 2nd example of EG2. 9 shows a region on the antenna element 13 side from an intermediate point between the antenna element 12 and the antenna element 13 in the configuration of the antenna device 20 of FIGS. 7 and 8. The area on the opposite side is omitted.

  The end portion EG2 of the substrate 21 according to the first example shown in FIG. 9A has a substantially fan-shaped cross section and a curved surface having a constant turning radius. That is, a continuous surface is formed from the upper surface to the side surface of the substrate 11, and there is no corner on the upper surface side of the end portion EG2 of the substrate 21. For this reason, when the reflected wave is diffracted by the end portion EG2 of the substrate 21, the radiation direction of the reflected wave due to the diffraction is dispersed, and the diffraction is relaxed.

  In the second example shown in FIG. 9B, in the configuration of the first example shown in FIG. 9A described above, the back surface of the end portion EG2 of the substrate 21 is continuous with the curved surface formed in the end portion EG2. And further includes a substrate extension 210. In the second example, since the board extension 210 is provided, the ground plate 16 is formed to avoid the board extension 210.

  According to the first example shown in FIG. 9A described above, diffraction may occur at the corner on the back surface side of the end portion EG2 of the substrate 21, and the antenna characteristics may deteriorate due to this diffraction. On the other hand, according to the second example shown in FIG. 9B, by providing the substrate extension part 210, the angle between the back surface side of the end portion EG2 of the substrate 21 (diffraction generation site) and the antenna element 13 is increased. The propagation distance between them is extended. Thereby, the influence by the diffraction which generate | occur | produces in the back surface side of edge part EG2 can be relieve | moderated.

FIG. 10 is a diagram illustrating a characteristic example of the antenna device 20 according to the second embodiment of the present invention.
In FIG. 10, a solid line indicates a conventional antenna characteristic that does not include a choke portion and does not form a curved surface at the end of the substrate, and a dotted line indicates the antenna characteristic of the antenna device 20 according to the first example described above. . As understood from the characteristics shown in the figure, according to the antenna device 20, the fluctuation of the phase difference θd in the antenna characteristics can be mitigated, and the phase difference θd of the received signals received by the antenna elements 12 and 13, respectively. Antenna characteristics in which the azimuth angle θ of the detection target has a one-to-one correspondence. Therefore, it is possible to suppress the deterioration of the antenna characteristics due to the diffracted wave generated at the end portion EG2 of the substrate 21, and it is possible to improve the reception accuracy.

<Third Embodiment>
Next, a third embodiment of the present invention will be described.
FIG. 11 is a diagram illustrating a configuration example of the antenna device 30 according to the third embodiment of the present invention.
The antenna device 30 has a configuration in which the antenna device 10 according to the first embodiment described above and the antenna device 20 according to the second embodiment are combined. That is, the antenna device 30 includes the substrate 21 provided in the antenna device 20 according to the second embodiment, instead of the substrate 11 in the configuration of the antenna device 10 according to the first embodiment. Other configurations are the same as those of the first embodiment.

  According to the antenna device 30 according to the third embodiment, the choke portions 14 and 15 functioning as diffraction points are provided between the antenna elements 12 and 13 and the end portions EG1 and EG2 of the substrate 21 as in the first embodiment. Therefore, similar to the first embodiment, an effect similar to that obtained when the distance between the antenna elements 12 and 13 and the end portions EG1 and EG2 of the substrate 21 is shortened can be obtained. In addition, according to the antenna device 30, since the curved surfaces are formed at the end portions EG1 and EG2 of the substrate 21 as in the second embodiment, the diffraction at the end portions EG1 and EG2 can be reduced.

FIG. 12 is a diagram illustrating a characteristic example of the antenna device 30 according to the third embodiment of the present invention.
In FIG. 12, the solid line indicates the conventional antenna characteristic that does not include the choke portion 15 and does not form a curved surface at the end of the substrate, and the dotted line indicates the antenna characteristic of the antenna device 30 according to the third embodiment. . As understood from the characteristics shown in the figure, the antenna characteristics of the antenna device 30 are extreme values when the azimuth angle θ is around 0 ° compared to the characteristics of the antenna device 10 according to the first embodiment shown in FIG. Has been resolved. Further, in the antenna characteristic of the antenna device 30, the flatness in the vicinity of the azimuth angle θ of 0 ° is eliminated as compared with the characteristic of the antenna device 20 according to the first embodiment shown in FIG. Therefore, according to the antenna device 30, the phase difference θd and the azimuth angle θ have a one-to-one correspondence relationship over the entire region, and the azimuth angle θ can be specified from the phase angle θd. Therefore, according to the third embodiment, it is possible to more effectively suppress the deterioration of the antenna characteristics and improve the reception accuracy as compared with the first and second embodiments described above. Become.

As mentioned above, although embodiment and modification of this invention were described, this invention is not limited to embodiment and modification which were mentioned above, In the range which does not deviate from the main point of this invention, various deformation | transformation, correction, Substitution, addition, etc. are possible.
For example, in the above-described embodiment, the choke portion 15 (15A, 15B) is formed in the region between the antenna elements 12, 13 and the end portions EG1, EG2 of the substrates 11, 21, but the end portions EG1, As long as the diffracted wave generated by the EG 2 can be attenuated, a conductive member in which the groove is omitted can be used instead of the choke portion 15.

10, 20, 30 Antenna devices 11, 21 Substrate 12, 13 Antenna elements 14, 15, 15A, 15B Choke portion 16 Ground plate 210 Substrate extension EG1, EG2 Substrate end WS Substrate width

Claims (6)

A substrate,
At least a pair of antenna elements disposed on the substrate;
A choke portion formed between the end of the substrate in the arrangement direction of the pair of antenna elements and the pair of antenna elements so as to be a diffraction point of a reflected wave from a detection target ;
An antenna device comprising: The choke portion is
The antenna device according to claim 1, further comprising a recess formed to extend in a direction substantially orthogonal to an arrangement direction of the pair of antenna elements.   The antenna device according to claim 2, wherein an opening direction of the concave portion of the choke portion is set to be substantially parallel to a main surface of the substrate on which the antenna element is disposed.   The antenna device according to claim 2, wherein an opening direction of the concave portion of the choke portion is set so as to be substantially perpendicular to a main surface of the substrate on which the antenna element is disposed.   The antenna device according to any one of claims 1 to 4, wherein an inclined surface is formed at an end of the substrate.   The antenna device according to claim 5, wherein the inclined surface is a curved surface formed in a convex shape toward the outside of the substrate.

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