JP6510394B2 - Antenna device - Google Patents

Description

  The present invention relates to an antenna device installed in an environment that reflects radio waves.

  A patch antenna formed on a dielectric substrate is used, for example, in a radar for monitoring the periphery of a mobile object such as a vehicle or an aircraft. The patch antenna includes a radiating element having a patch-like pattern formed on one surface of a dielectric substrate, and a ground plane formed on the other surface of the substrate.

  By the way, when using a patch antenna as an antenna of a radar installation for vehicles, mounting in a bumper of vehicles is considered, for example. In this case, a part of the radio wave emitted from the antenna is reflected by the inner wall of the bumper and then re-reflected by the radiation surface of the antenna, and the re-reflected wave interferes with the radiation wave to adversely affect the radiation characteristic of the antenna. It is known to give

  On the other hand, in the cited reference 1, a plurality of conductor patches arranged at a predetermined interval and a connection element for electrically connecting the conductor patches to each other are formed on the other surface of the substrate having the ground plate formed on one surface. An electromagnetic wave reflecting surface of a flat substrate structure is disclosed. By using this electromagnetic reflecting surface, it is possible to tilt the wave front of the reflected wave reflected by the electromagnetic reflecting surface by configuring the connection element with a capacitance or inductance that increases or decreases according to the arrangement position along one desired direction. That is, the reflection direction of the electromagnetic wave can be directed to a desired direction.

  And, in the above patch antenna, by forming such an electromagnetic reflection surface around the radiation element, interference is suppressed by re-reflecting the reflected wave from the bumper in a direction different from the radiation wave. Conceivable.

JP, 2011-193345, A

  However, although the interference by the reflected wave is suppressed in the main radiation direction by utilizing such an electromagnetic reflection surface, a strong beam different from the main beam is reflected in the reflection direction of the re-reflected wave from the antenna radiation surface. There is a problem that it may be formed and cause false detection of the target.

  The present invention has been made in view of these problems, and an object of the present invention is to provide a technology for sufficiently suppressing the influence of a reflected wave even when installed in an environment that reflects radio waves.

  The antenna device (1) of the present invention comprises a dielectric substrate (2), a ground plate (3), an antenna portion (4), and a reflecting portion (5). The ground plane is formed on one side of the dielectric substrate and acts as an antenna ground plane. The antenna unit is formed on the other surface of the dielectric substrate, and has an antenna pattern that acts as an array antenna. The reflective portion is disposed around the antenna portion, and has a plurality of conductive patches having dimensions smaller than the wavelength at a preset operation frequency and acting as a reflective plate. Further, the plurality of conductor patches constituting the reflection portion form a plurality of blocks arranged along a preset block arrangement direction, and have a structure in which the phase of the reflected wave at the operating frequency is unevenly different for each block .

  According to such a configuration, the reflection wave incident on the radiation surface is reflected not in a fixed direction but in various directions with the surface of the dielectric substrate on which the antenna portion and the reflection portion are formed as the radiation surface, ie, , Can scatter the reflection. As a result, when the reflected wave coming from the radiation direction of the radiation wave is re-reflected by the radiation surface, the reflection intensity of the re-reflected wave heading in the same direction as the radiation wave can be reduced, and the power by the re-reflected wave in a specific direction Interference due to the re-reflected wave can be suppressed without forming a complex beam.

  In addition, the reference numerals in the parentheses described in this column and the claims indicate the correspondence with specific means described in the embodiment described later as one aspect, and the technical scope of the present invention It is not limited.

It is a xy top view used as the front view of an antenna apparatus. It is a xz top view used as the side view of an antenna apparatus. It is the graph which varied the dimension of the conductive patch about the frequency characteristic which calculated | required the phase of the reflected wave in the conductive patch on the basis of the phase of the reflected wave in a board | substrate normally, and was shown. It is explanatory drawing which shows typically the reflective direction in the radiation | emission surface of the normal board | substrate without a conductive patch. It is explanatory drawing which shows typically the reflective direction in the radiation | emission surface of the board | substrate with which the phase difference of the reflected wave which arises between the conductive patches which straddle a block is constant. It is explanatory drawing which shows typically the reflective direction in the radiation | emission surface of the board | substrate which enlarged the phase difference of the reflected wave which arises between the conductive patches which straddle a block gradually. It is a list which shows the phase difference of the reflected wave which arises between the blocks of Example 1, 2 and Comparative Example 1, 2. It is a graph which shows the simulation result which asked for the reflective intensity when light enters from the front of an antenna device, ie, the direction which becomes 0 azimuth of reflective azimuth, on the basis of the reflective intensity in a substrate in general. It is a graph which shows the simulation result which calculated the gain variation of antenna gain as a result of having received the influence of interference based on a reflected wave by the existence of a bumper on the basis of the antenna gain when a bumper does not exist. It is explanatory drawing which showed typically the reflected wave which arises by a bumper. It is a graph which shows the simulation result which asked for reflective intensity, when it was set up so that phase lag might increase monotonously from one end to the other end of the block sequence direction of a dielectric substrate. It is the graph which changed the size of the gap between patches variously about the frequency characteristic which asked for the phase of the reflected wave in a conductive patch on the basis of the phase of the reflected wave in a substrate normally.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[1. Constitution]
The antenna device 1 is used for a millimeter wave radar for detecting various objects present around the vehicle, and is mounted in a bumper of the vehicle.

  The antenna device 1 is formed of a copper pattern formed on a rectangular dielectric substrate 2 as shown in FIGS. 1 and 2. Hereinafter, one surface of the dielectric substrate 2 is referred to as a substrate surface 2a, and the other surface is referred to as a substrate back surface 2b. The direction along one side of the dielectric substrate 2 is referred to as the x-axis direction, the direction along the other side orthogonal to the x-axis direction is referred to as the y-axis direction, and the normal direction of the substrate surface 2a is referred to as the z-axis direction.

  A ground plate 3 made of a copper pattern is formed on the back surface 2b of the substrate to cover the entire surface. An antenna unit 4 is formed on the substrate surface 2 a near the center of the substrate surface 2 a, and a reflecting unit 5 is formed around the antenna unit 4. Hereinafter, the substrate surface 2a is also referred to as a radiation surface.

  The antenna unit 4 includes a plurality of array antennas arranged along the x-axis direction. Each array antenna includes a plurality of rectangular patch antennas 41 arranged along the y-axis direction, and a feed line 42 for feeding each patch antenna 41. The polarization direction of the radio wave radiated from the antenna unit 4 is configured to coincide with the x-axis direction.

  The reflection part 5 is comprised by arrange | positioning the rectangular-shaped conductor patch P which consists of copper patterns two-dimensionally. The conductor patch P is formed in a square shape, and the size of one side thereof is set smaller than the wavelength λ at the operating frequency of the antenna device 1. More specifically, the size of one side of the conductor patch P is preferably 3/4 wavelength or less, and here, a size of about 1⁄5 to 1⁄3 wavelength is used.

  The conductor patches P constituting the reflecting portion 5 are arranged in a line in the same size along the y-axis direction, and the conductor patches P of the same size arranged in the line form a block B. Also, the blocks B are arranged along the x-axis direction, and the sizes of the conductor patches P constituting each block B are different from one another. That is, the block arrangement direction coincides with the x-axis direction. However, the gap between the conductor patches P in the block B and the gap between the conductor patches P across the block B are both set to fixed sizes.

  The reflection part 5 has a line along the y-axis direction passing through the center position in the x-axis direction as a block center, and is constituted by two portions 51 and 52 having the block center as a boundary. Each of the blocks B constituting the two portions 51 and 52, and hence the conductor patch P, has a structure which is axisymmetrical to the center of the block. In the following, among the portions 51 and 52, the block closest to the block center is represented by B1, and hereinafter, each block is represented by B2, B3,... As the blocks are sequentially separated from the block center.

  In the reflective portion 5, the conductor patch P has an inductance component, and the gap between the conductor patches P has a capacitance component. That is, as shown in FIG. 2, in the reflection unit 5, as shown in FIG. 2, the series circuit including the inductance and the capacitance is connected in series by the number of blocks. Then, with respect to the current flowing through the radiation surface 2a, the inductance component causes a phase delay and the capacitance component causes a phase lead.

  Each block Bi which comprises the reflection part 5 is designed by the structure which satisfy | fills the conditions of the following (1)-(3) using this property. That is, (1) the phase characteristics of the reflected wave are line symmetrical about the block center. (2) The phase delay increases as the distance from the block center increases. (3) The greater the distance from the block center, the larger the phase difference between adjacent blocks. That is, the phase difference is inclined.

Here, it is designed by adjusting the size of the conductor patch P which comprises each block Bi.
[2. design]
The phase characteristic (hereinafter, reflection characteristic) of the reflected wave at the conductor patch P is specifically shown in FIG. 3 based on the phase of the reflected wave at the normal substrate which is a substrate not having the reflection part 5. It becomes a thing. However, the gap between the conductor patches P is fixed at 1 mm, and the size of one side of the conductor patch P is changed between 2.5 mm and 3.3 mm. That is, when the size of the conductor patch P is constant, the phase delay becomes larger as the operating frequency becomes higher. Further, when the operating frequency is fixed, the phase delay increases as the size of the conductor patch P increases. However, in FIG. 3, since the phase difference is shown in the range of -180 deg to 180 deg, the phase differences -180 deg and 180 deg are regarded as identical.

  Then, the size of the conductor patch P of the block Bi serving as the reference is arbitrarily determined, and the size of the conductor patch of the block adjacent to the block whose size is determined is determined using the relationship shown in FIG. Setting so as to obtain a preset phase difference. The size of the conductor patches P of all the blocks Bi is designed by repeating this sequentially.

[3. Action]
In the case of a normal substrate without the conductor patch P or when the phase difference of the reflected wave is designed to be 0 deg between the blocks B, as shown in FIG. The part bounces in the same phase. As a result, the reflected light is directed to the incoming direction of the incident light.

  When the phase difference between the blocks B is constant, that is, in the case of the configuration corresponding to the prior art not satisfying the above condition (3), as shown in FIG. The reflected light is delayed in phase as it goes away from the block center. However, the phase delay is proportional to the distance from the block center. As a result, the reflected light is reflected in a certain direction at an angle to the incoming direction of the incident light. That is, the reflection characteristic equivalent to the reflection on the plane refracting substrate bent in a mountain shape can be obtained.

  In the case of the present embodiment in which the phase difference between the blocks B is inclined, as shown in FIG. 6, the incident light from the z-axis direction is reflected by the radiation surface 2a, and the reflected light has a phase Will be delayed. However, the phase delay is accelerated as the distance from the block center increases. As a result, the reflected light is reflected in a direction having an angle with respect to the incoming direction of the incident light, and the reflection angle becomes larger the further from the block center. That is, the reflection characteristic corresponding to the reflection on the curved substrate is obtained, and the reflected light is scattered and directed in various directions, not in a fixed direction.

[4. effect]
According to the first embodiment described above, the following effects can be obtained.
(A) According to the antenna device 1, the reflection direction of the reflected wave reflected by the radiation surface 2a is not the front or a predetermined constant direction but the surrounding, although it is configured using the planar dielectric substrate 2 Can be scattered in various directions. As a result, even if it is installed in the bumper of a vehicle, the influence of the interference based on the reflected wave from a bumper can be suppressed.

  (B) In the antenna device 1, since the inductance component of the conductor patch P and the capacitance component due to the gap between the conductor patches P are used, it is not necessary to arrange the connection element between the conductor patches P unlike the prior art. As a result, even in the millimeter wave band where the gap between the conductor patches is extremely narrow, it can be applied without any problem.

[5. Experiment]
As shown in FIG. 7, Example 1 in which the increase width of the phase difference between adjacent blocks B is set to 30 deg, Example 2 in which the increase width of the phase difference is set to 50 deg, and a normal substrate without the reflective portion 5 The simulation results of the comparative example 1 and the comparative example 2 in which the phase difference between the blocks B is set to a constant value of 100 deg will be described. However, the operating frequency was 24.15 GHz.

  As shown in FIG. 8, in Comparative Example 2, although the reflection to the vicinity of the reflection azimuth of 0 deg is suppressed as compared with Comparative Example 1, large reflection occurs in the vicinity of ± 50 degrees. On the other hand, in the first embodiment, it is understood that the reflection is suppressed over the entire reflection direction without causing strong reflection in the specific direction.

  As shown in FIG. 9, the presence of the bumper causes a gain fluctuation of at most 5 dB in Comparative Example 1 and at most 2 dB in Comparative Example 2 as compared to the case where no bumper is present, but in Example 1 is at most 1.5 dB. It can be seen that the gain fluctuation is suppressed. When a bumper is present, as shown in FIG. 10, the direct wave emitted from the antenna device 1 is reflected by the bumper, the reflected wave is re-reflected by the radiation surface 2 a of the antenna device 1, and the re-reflected wave The result of interference with the direct wave is radiated to the outside through the bumper. Here, the distance from the radiation surface 2a to the bumper is 28 mm.

  FIG. 11 shows the case where the reflection characteristic of the reflection portion 5 is not line symmetrical with respect to the block center but is continuously changed in phase from one end to the other end in the x-axis direction, ie, It is the result of calculating | requiring the reflective intensity similar to FIG. 8 by simulation which comprises the reflection part 5 only by the structure of one of the site | parts 51 and 52. FIG. FIG. 8 shows the result of the addition synthesis of the graph of FIG. 11 and a graph obtained by horizontally reversing this graph.

[6. Other embodiments]
As mentioned above, although the form for implementing this invention was demonstrated, this invention can be variously deformed and implemented, without being limited to the above-mentioned embodiment.

  (A) In the above embodiment, the delay phase is adjusted by making the gap between the conductor patches P across the block B constant and changing the size of the conductor patches P. However, the present invention is not limited to this. For example, the size of the conductor patch P may be the same in all the blocks B, and the delay phase may be adjusted by changing the gap between the conductor patches P across the block B. In this case, instead of the graph shown in FIG. 3, the reflector 5 may be designed using the graph shown in FIG. In FIG. 12, the size of the conductor patch P is fixed to 2.9 mm × 2.9 mm, and the gap between the conductor patches is changed in the range of 0.16 mm to 0.2 mm for each normal substrate. The frequency characteristic of the phase difference is obtained. As shown in the figure, it can be seen that the phase delay increases as the gap is increased if the operating frequency is constant, and as the operating frequency is increased if the gap is constant.

  (B) In the above embodiment, the reflecting portion 5 is designed to satisfy the conditions (1) to (3), but if the reflected wave can be scattered almost equally in various directions, the condition ((1) 1) It is not necessary to satisfy all of (3).

  (B) The multiple functions of one component in the above embodiment may be realized by multiple components, or one function of one component may be realized by multiple components. . Also, a plurality of functions possessed by a plurality of components may be realized by one component, or one function realized by a plurality of components may be realized by one component. In addition, part of the configuration of the above embodiment may be omitted. In addition, at least a part of the configuration of the above-described embodiment may be added to or replaced with the configuration of the other above-described embodiment. In addition, all the aspects contained in the technical thought specified only by the words described in the claim are an embodiment of the present invention.

  (C) In addition to the above-described antenna device, the present invention can also be realized in various forms, such as a system including the antenna device as a component and a method of suppressing interference due to an unwanted reflected wave.

  DESCRIPTION OF SYMBOLS 1 ... Antenna apparatus, 2 ... Dielectric substrate, 2a ... Substrate surface / radiation surface, 2b ... Substrate back surface, 3 ... Ground plate, 4 ... Antenna part, 5 ... Reflection part, 41 ... Patch antenna, 42 ... Feeding line, 51, 52 ... site, B ... block, P ... conductor patch.

Claims (8)

An antenna device (1) mounted in a bumper of a vehicle.
A dielectric substrate (2),
A ground plane (3) formed on one side of the dielectric substrate and acting as an antenna ground plane;
An antenna portion (4) formed on the other surface of the dielectric substrate and having an antenna pattern acting as an array antenna;
A reflective portion (5) disposed around the antenna portion, having a size smaller than a wavelength at a preset operating frequency, and having a plurality of conductive patches acting as a reflective plate;
Equipped with
The plurality of conductor patches constituting the reflection portion are formed on the same surface as the surface of the dielectric substrate on which the antenna pattern is formed, and form a plurality of blocks aligned along a block arrangement direction set in advance. ,
The conductor patch has the conductor patch such that the phase of the reflected wave at the operating frequency is different for each block, and the phase difference of the reflected wave between the adjacent blocks is unevenly different for each adjacent block. The antenna apparatus in which the inductance component which has and the capacitance component which between the said conductor patches have were set . In the antenna device according to claim 1,
An antenna device in which the phase of the reflected wave is delayed as the block is farther from the block center which is the center of the dielectric substrate in the block arrangement direction. In the antenna device according to claim 2,
The antenna apparatus with which the phase difference of the said reflected wave between the said adjacent blocks becomes large, so that it distances from the said block center. The antenna device according to any one of claims 1 to 3.
An antenna device in which the phase of the reflected wave is adjusted by making the dimensions of the conductor patch different for each block. The antenna device according to any one of claims 1 to 4.
An antenna device in which the phase of the reflected wave is adjusted by making the intervals between the conductor patches adjacent to each other different across the blocks. The antenna device according to any one of claims 1 to 5.
The said block is set so that the phase characteristic of the said reflected wave may become symmetrical on both sides of the said block center. Antenna apparatus. In the antenna device according to claim 6,
An antenna device in which the block arrangement direction matches the polarization direction of the array antenna. The antenna device according to any one of claims 1 to 7.
The dimension of the said conductor patch is 3/4 wavelength or less. Antenna apparatus.