Antenna device

Abstract

Antenna apparatus (1, 1A, 1B) mounted in a bumper of a vehicle, the antenna apparatus comprising: a non-conductive substrate (2), a base plate (3) provided on a first surface (2b) of the non-conductive substrate and configured to serve as an antenna bottom surface, an antenna unit (4) provided on a second surface (2a) of the non-conductive substrate and having an antenna pattern configured to serve as an antenna array, and a reflecting unit (5, 5a, 5b) arranged to surround the antenna unit, the reflecting unit including a plurality of conductor patterns serving as a reflector, wherein each of the plurality of conductor patterns (P, Pa, Pb) has a size smaller than an effective wavelength at a preset operating frequency of the antenna unit and is structured to generate resonance in a resonance direction different from a polarization direction of a radio wave transmitted and received by the antenna unit.

Description

Technical area

[0001] The present disclosure relates to an antenna apparatus installed in an environment where radio waves are reflected. State of the art

[0002] A patch antenna formed on a non-conductive substrate is used for a radar or the like mounted on a mobile body such as a vehicle or aircraft to monitor its surroundings. The patch antenna is provided with a radiating element including a patch-like pattern formed on one surface of the non-conductive substrate and a base plate formed on the other surface of the substrate.

[0003] For example, if the patch antenna is used as an antenna for an in-vehicle radar system, the patch antenna may be mounted in the vehicle's bumper. In this case, it is known that a portion of a radio wave emitted by the antenna is reflected off an inner wall of the bumper and further re-reflected off a radiating surface of the antenna. The re-reflected wave interferes with the emitted wave and affects the antenna's radiation characteristics.

[0004] JP 2011-193345 A, listed below, discloses an electromagnetic wave reflecting surface of a planar substrate structure including a substrate having a base plate formed on one surface thereof and a plurality of conductor patches and connecting elements provided on the other surface of the substrate. The conductor patches are arranged at predetermined intervals, and the connecting elements electrically connect the conductor patches to each other. The use of the electromagnetic wave reflecting surface allows a wavefront of a reflected wave reflected at the electromagnetic wave reflecting surface to be inclined.This inclination of the reflected wave is achieved by configuring the connecting elements based on an increase or decrease in storage capacity or inductance, according to the arranged position of the conductor patches along a desired direction. This means that a reflection of an electromagnetic wave can be directed toward or in a desired direction.

[0005] In the patch antenna described above, the electromagnetic wave reflecting surface described above may be formed around the radiating element such that the reflected wave is re-reflected by the bumper in a direction different from the direction in which the radiated wave travels. As a result, potential interference caused by the reflected wave corresponding to a main beam in the radiation direction is suppressed. On the other hand, the inventor's extensive investigation has revealed the formation of a strong beam that is different from the main beam in a reflection direction of the re-reflected wave from the antenna reflecting surface, causing erroneous detection of a target.

[0006] US 2016 / 0 028 161 A1 discloses an antenna device that can both suppress directivity interference caused by surface current and maintain the desired beamwidth. The antenna device comprises a dielectric substrate in which a ground plane is formed on one of two substrate surfaces, a patch antenna, and a plurality of conductive structures formed on the dielectric substrate.

[0007] US 2015 / 0 084 803 A1 provides an antenna for a radar sensor configured to transmit a transmitted signal. A baffle near the antenna reflects a previously reflected portion of the transmitted signal toward the antenna. The antenna comprises a transmitting element, a receiving element, and an anti-reflection element. The transmitting element is configured to direct the transmitted signal along a straight line crossing the baffle, the receiving element is configured to detect a reflected signal reflected by an object located behind the baffle, and the anti-reflection element is configured to reduce the reflection of the previously reflected portion by the antenna.

[0008] According to US 2015 / 0 378 006 A1, a radar device is provided with which the influence of a structure, such as a bumper, arranged on a transmission path on a transmitted signal or a received signal can be reduced. For this purpose, a radar device configured to detect an object comprises a transmitting antenna, a receiving antenna, and a dummy antenna. The transmitting antenna is configured to transmit a radio-frequency signal, the receiving antenna is configured to receive a radio-frequency signal transmitted by the transmitting antenna and reflected by the object, and the dummy antenna is configured to attenuate a radio-frequency signal transmitted by the transmitting antenna and reflected by a structural object, the structural object being located within a transmission path of the radio-frequency signal. Summary of the invention

[0009] The object of the present invention is to provide an antenna apparatus capable of sufficiently suppressing adverse effects of a reflected wave even when the antenna apparatus is installed in an environment where radio waves are reflected.

[0010] This object is solved by the subject matter of patent claim 1. Further developments according to the invention are the subject matter of the dependent claims.

[0011] One aspect of the present disclosure is a bumper-mounted antenna apparatus including a non-conductive substrate, a base plate, an antenna unit, and a reflective unit. The base plate is provided on a first surface of the non-conductive substrate and serves as an antenna bottom surface. The antenna unit is provided on a second surface of the non-conductive substrate and has an antenna pattern configured to serve as an antenna array. The reflective unit is arranged around the antenna unit and includes a plurality of conductor patterns serving as a reflector.Each of the plurality of conductor patterns included in the reflecting unit has a size smaller than an effective wavelength at a preset operating frequency of the antenna unit and is structured to generate resonance in a resonance direction different from a polarization direction of a radio wave transmitted and received by the antenna unit.

[0012] According to one aspect of the present disclosure, the plurality of conductor patterns included in the reflecting unit are structured to resonate in a resonant direction different from the polarization direction of the radio wave transmitted and received by the antenna unit. Consequently, a reflected wave reflected by the reflecting unit corresponds to a polarized wave polarized in a direction different from the polarization direction in the antenna unit.Therefore, if a radiated wave emitted from the non-conductive substrate surface is reflected in the direction of radiation and arrives at the reflecting unit and is re-reflected by it, potential interference between the radiated wave and the re-radiated wave can be suppressed, even if the direction of re-radiation is the same as the direction of radiation. Therefore, even if the antenna device is installed in an environment where radio waves are reflected, the adverse effects of the reflected wave can be sufficiently suppressed.

[0013] Reference numerals placed in parentheses in the claims indicate correspondence relationships to specific means described as an aspect in the embodiments discussed below and are not intended to limit the technical scope of the present disclosure. Short description of the drawings Fig. 1 is a perspective view of an XY plane corresponding to a front surface of an antenna apparatus according to a first embodiment, Fig. 2 is an enlarged view of a part of the XY plane shown in Fig. 1 is shown, Fig. 3 is a cross-sectional view of the antenna apparatus taken along a line III-III, Fig. 4 is a diagram schematically showing a reflection direction from an emitting surface of a normal substrate, Fig. Figure 5 is a diagram schematically illustrating a reflected wave reflected from a bumper, Fig. 6 is a graph illustrating results of a simulation in which a reflection intensity on a normal substrate is used as a reference to determine an X component of a reflection intensity resulting from an incidence of light from a direction corresponding to a reflection azimuth of 0 degrees, Fig. 7 is a plan view of an XY plane corresponding to a front surface of an antenna apparatus according to a first example of a second embodiment, Fig. 8 is a plan view of an XY plane corresponding to the front surface of the antenna apparatus according to a second example of the second embodiment, Fig. 9 is a graph illustrating frequency characteristics indicating a phase of a reflected wave from each conductive patch determined using, as a reference, a phase of a reflected wave from a normal substrate by differently changing its or the size of the conductive patch, Fig. 10 is a table showing the phase of a reflected wave from each block in the first example and a third example of the second embodiment, Fig. 11 is a table showing the phase of a reflected wave from each block and the size of the corresponding conductor patch in the third example of the second embodiment, Fig. Fig. 12 is a diagram schematically illustrating a reflection direction from a radiating surface of a substrate subjected to a constant phase difference of the reflected wave between adjacent conductive patches included in different adjacent blocks, Fig. 13 is a diagram schematically illustrating the reflection direction from the radiating surface of the substrate having a gradually increased reflected wave phase difference between adjacent conductor patches included in different adjacent blocks, Fig. 14 is a graph illustrating results of a simulation in which a reflection intensity obtained from an incidence of light from the direction corresponding to the reflection azimuth of 0 degrees is determined using, as a reference, the reflection intensity on the normal substrate in the first and third examples of the second embodiment, Fig. Figure 15 is a graph showing results of a simulation in which the reflection intensity resulting from the incidence of light from the direction corresponding to the reflection azimuth of 0 degrees was calculated using, as a reference, the reflection intensity on the normal substrate in each example shown in Fig. 11 is shown, Fig. 16 is a plan view of an XY plane corresponding to a front view of the antenna apparatus configured such that a reflected wave reflected by a reflecting unit corresponds to the same polarized wave to which a reflected wave from an antenna unit corresponds, Fig. Figure 17 is a graph showing results of a simulation in which the reflection intensity of a reflection from the normal substrate is used as a reference to calculate the X component of the reflection intensity resulting from the incidence of light from the direction corresponding to the reflection azimuth of 0 degrees for the normal substrate, the substrate with the same polarized wave used in Fig. 16, and to determine the substrate according to the second example of the second embodiment, Fig. 18 is a graph showing the X component and a corresponding Y component in the simulation results according to the second example of the second embodiment shown in Fig. 17 is shown, Fig. Figure 19 is a graph showing the X component and the corresponding Y component in the simulation results according to the substrate with the same polarized wave used in Fig. 17 is shown, Fig. Figure 20 is a graph showing the X component and the corresponding Y component in the simulation results according to the normal substrate used in Fig. 17 is shown, Fig. Figure 21 is a graph illustrating results of a simulation in which an antenna gain resulting from the absence of a bumper is used as a reference to determine the magnitude of a gain variation in the antenna gain resulting from adverse effects of interference based on a reflected wave resulting from the presence of a bumper, Fig. 22 is a plan view of an XY plane showing a part of the front view of the antenna apparatus according to another embodiment, Fig. 23 is a plan view of an XY plane showing a part of the front view of the antenna apparatus according to another embodiment, Fig. 24 is a graph showing results of a simulation in which the reflection intensity of a reflection from the normal substrate is used as a reference to determine the reflection intensity resulting from the incidence of light from the direction corresponding to the reflection azimuth of 0 degrees in a case where an inclination angle at which the conductor patches are arranged is varied, and Fig. 25 is a plan view of an XY plane corresponding to the front surface of the antenna apparatus of another embodiment. Fig. Figure 26 is a diagram of a conductor patch in the antenna apparatus used in Fig. 25 is shown. Description of the embodiments

[0014] Embodiments of the present disclosure will be described below with reference to the drawings. First embodiment1. Configuration

[0015] An antenna device 1 is used for a millimeter-wave radar configured to detect various targets present around a vehicle and is mounted in a bumper of the vehicle. The bumper of the vehicle is formed of a material that transmits radio waves, for example, resin.

[0016] The antenna apparatus 1 is formed of a copper pattern provided on a rectangular non-conductive substrate 2, as shown in Fig. 1 to 3. One surface of the non-conductive substrate 2 is hereinafter referred to as a substrate front surface 2a. The other surface of the non-conductive substrate 2 is hereinafter referred to as a substrate back surface 2b. A direction along one side of the non-conductive substrate 2 is hereinafter referred to as an X-axis direction. A direction along another side of the non-conductive substrate 2, which is perpendicular to the X-axis direction, is hereinafter referred to as a Y-axis direction. A normal direction of the substrate front surface 2a is hereinafter referred to as a Z-axis direction.

[0017] The substrate rear surface 2b has a base plate 3 formed from a copper pattern covering the entire rear surface 2b. An antenna unit 4 is formed near the center of the substrate front surface 2a. A reflecting unit 5 is formed around the antenna unit 4. The substrate rear surface 2b will also be referred to as a radiating surface 2a hereinafter.

[0018] The antenna unit 4 is provided with a plurality of array antennas arranged along the X-axis direction. Each of the array antennas is provided with a plurality of rectangular patch antennas 41 arranged along the Y-axis direction and feed lines 42 through which electricity is supplied to each of the patch antennas 41. The antenna unit 4 is configured such that a polarization direction (hereinafter referred to as a polarization direction Dan) of radio waves transmitted and received by the antenna unit 4 coincides with the X-axis direction.

[0019] As it is in Fig. As shown in Figure 2, the reflective unit 5 is configured by two-dimensionally arranged rectangular conductor patches P containing copper patterns. All of the conductor patches P are arranged such that two adjacent sides of each conductor patch P are inclined by 45 degrees to the polarization direction Dan. In the following description, an α direction refers to the direction of one of the two adjacent sides of the conductor patch P, and a β direction refers to the direction of the other side of the conductor patch P. In the present embodiment, all of the conductor patches P in the reflective unit 5 are formed to have the same shape and the same size, and all intervals between the conductor patches P are formed to have the same length. Each of the conductor patches P is a parasitic element. Each conductor patch P is shaped like a rectangle.The size a1 of each short side of the rectangle and the size b1 of each long side thereof are set smaller than an effective wavelength λo at an operating frequency fo of the antenna unit 4. Specifically, the sizes a1 and b1 are each set to be less than or equal to three-quarters of the effective wavelength λo. For example, the sizes a1 and b1 are set to 2.6 mm and 3.3 mm, respectively, at an operating frequency of fo = 24.15 GHz.

[0020] In the reflecting unit 5, each conductor patch P has an inductance component and the gap between the conductor patches P has a storage capability component. In other words, as shown in Fig. 3, the reflecting unit 5 is represented by an equivalent circuit including a plurality of series circuits LC, each of which includes inductances and storage capabilities, and which are connected to each other in an α-direction and a β-direction. The inductance component and the storage capability component respectively cause a phase lag and a phase advance with respect to a current flowing across the radiating surface 2a.

[0021] Furthermore, in the reflecting unit 5, electrical resonance occurs in the directions along the sides of each conductor patch P. The reflecting unit 5 is configured such that the series circuits LC generate resonance at the operating frequency fo by adjusting the size of at least one of the variables, the conductor patch P and the gap, in one of the α-direction and β-direction. That is, an angle θr between the polarization direction Dan and a resonance direction of the reflecting unit 5 at the operating frequency fo is 45°. The angle θr corresponds to the tilt angle. 2. Operation

[0022] In the present embodiment, in the reflecting unit 5, the inductance components of the conductor patches P are all the same and the storage capability components of the gaps are all the same, resulting in a phase difference of 0 degrees between the conductor patches P. Therefore, in the case of a normal substrate, an incident wave entering the reflecting unit 5 from the Z-axis direction has the same phase, regardless of which part of the reflecting surface 2a the incident wave bounces off, as shown in Fig. 4. As a result, the reflected wave moves toward a direction of arrival of the incident wave. Therefore, if a radiated wave radiated from the radiating surface 2a is reflected by the bumper and arrives at the radiating surface 2a and is reflected again by it, as shown in Fig. 5, the re-reflected wave travels in the same direction as that of the emitted wave emitted from the emitting surface 2a.

[0023] Here, a polarization direction Dp of the reflected wave reflected by the reflecting unit 5 corresponds to the resonance direction of the reflecting unit 5. The angle θr between the resonance direction of the reflecting unit 5 and the polarization direction Dan is 45°. In other words, the incident wave that has penetrated the reflecting unit 5 is radiated with its polarization direction rotated by 45°. The polarization direction Dp of the reflected wave forms an angle of 45° with the polarization direction Dan. This suppresses possible interference of the reflected wave from the reflecting unit 5 with the radiated wave from the radiating surface 2a. 3. Effects

[0024] The first embodiment described above produces the following effects. (1) The polarization direction Dp of the reflected wave reflected by the reflecting unit 5 is different from the polarization direction Dan of radio waves transmitted and received by the antenna unit 4. As a result, even if the antenna apparatus 1 is installed in the bumper of the vehicle, the re-reflected wave based on the reflected wave from the bumper can be prevented from interfering with the radiated wave from the radiating surface 2a. 4. Experiments

[0025] The following description, which is made with reference to Fig. 6 refers to results of simulation for Comparative Example 1 using the normal substrate including only the antenna unit 4 and no conductor patches P, and Example 1 using the non-conductive substrate 2 according to the present embodiment. Fig. 6 represents the X-component of the reflection intensity with respect to a reflection azimuth relative to the normal substrate. Fig. 6 indicates that for the entire reflection azimuth, the X component of the reflection intensity, that is, the component in the same direction as the polarization direction Dan, is smaller than that in Comparative Example 1. Second Embodiment 1. Differences from the First Embodiment

[0026] A second embodiment is similar in basic configuration to the first embodiment. Therefore, descriptions of common components will be omitted, focusing on differences from the first embodiment. The same reference numerals as those in the first embodiment denote the same components described above in the first embodiment.

[0027] An antenna apparatus 1A according to the second embodiment includes a reflecting unit 5a, which is different in configuration from the reflecting unit 5 according to the first embodiment. In the above-described first embodiment, the conductor patches P included in the reflecting surface 5 are all the same in size, and the gaps between the conductor patches P are all the same in size. Consequently, the reflected wave has a same phase regardless of where on the radiating surface 2a the reflection occurs. In contrast, the second embodiment is different from the first embodiment in that the phase of the reflected wave is changed according to a reflection point on the radiating surface 2a by changing the size of each of the conductor patches Pa included in the reflecting unit 5. 2. Configuration

[0028] Fig. 7 and Fig. 8 illustrate plan views of XY planes in a first example and a second example of the reflecting unit 5a according to the second embodiment. In the first example and the second example, the reflecting unit 5a is configured by arranging all the rectangular conductor patches Pa such that two adjacent sides of each of the conductor patches Pa are inclined at an angle of 45° to the polarization direction Dan. 2-1. First example

[0029] Each of the conductor patches Pa is square or rectangular. As shown in Fig. As shown in Figure 7, the conductor patches Pa having the same size are arranged in a line along a β-axis direction to form blocks Bα. Furthermore, the blocks Bα are arrayed along an α-axis direction, and the size of the conductor patches Pa included in each block Bα varies among the blocks Bα. In other words, a block array direction coincides with the α-axis direction. However, the gaps between the adjacent conductor patches Pa in each block Bα and the intervals between the adjacent conductor patches Pa included in the various adjacent blocks Bα are set to have constant sizes, respectively.

[0030] The reflective unit 5a is centrally located at a block Bα0 extending along the β-axis direction and through the center of the reflective unit 5 in the α-axis direction, and is provided with two regions 51α, 52α separated by the central block βα0 serving as a boundary. The blocks Bα included in the two regions 51α, 52α are structured to be line-symmetric with respect to the central block Bα0, and thus, the conductor patches Pa are structured to be line-symmetric with respect to the central block Bα0. The block closest to the block Bα0, which serves as the boundary between the regions 51α, 52α, is labeled Bα1, and the remaining blocks are sequentially labeled Bα2, Bα3,... in order of increasing distance from the block Bα0.

[0031] Using the characteristics of the inductance component of each conductor patch Pa and the storage capability component between the conductor patches Pa, each block Bαi included in the reflecting unit 5 is designed to have a structure that satisfies the conditions (1.1) to (1.4) described below. An integer of 0 or greater is denoted by i. (1.1) The phase characteristics of reflected waves are line-symmetric with respect to the central block Bα0. (1.2) A phase lag in the α-axis direction increases with increasing distance from the central block Bα0, that is, increases with increasing distance from the center of the antenna unit 4. (1.3) At the operating frequency fo, resonance occurs in the α-axis direction. (1.4) Among the blocks Bα, a phase difference Δθα between the adjacent blocks Bα is equal to or increases with the distance from the center of the antenna unit 4. This means that the reflecting unit 5 includes an equal phase difference or an inclined phase difference.

[0032] In this case, the length of one side of each conductor patch Pa included in each block Bαi is changed to adjust the phase of the reflected wave in two directions centrally located at the center of the antenna unit 4, that is, in ±-directions of the α-axis. 2-2. Second example

[0033] Each of the conductor patches Pa is square or rectangular. As shown in Fig. As shown in Figure 8, the conductor patches Pa are arranged in series along the β-axis direction and also arranged in series along the α-axis direction. The conductor patches Pa arranged in series in the β-axis direction form blocks Bα, and the conductor patches Pa arranged in series in the α-axis direction form blocks Bβ. That is, one conductor patch Pa belongs to both block Bα and block Bβ. The blocks Bα are arranged or lined up along the α-axis direction, and the blocks Bβ are arranged or lined up along the β-axis direction.

[0034] Each of some of the blocks Bα and Bβ contains conductor patches Pa of the same size, whereas each of the others contains conductor patches Pa of different sizes. Furthermore, the sizes of the conductor patches Pa included in each block Bα vary among the blocks Bα, and the sizes of the conductor patches Pa included in each block Bβ vary among the blocks Bβ. However, a constant size is set for the intervals between the conductor patches Pa in each of the blocks Bα and Bβ, for the intervals between the adjacent conductor patches Pa included in the different adjacent blocks Bα, and for the intervals between the adjacent conductor patches Pa included in the different adjacent blocks Bβ.

[0035] The reflective unit 5a is provided with two regions 51α, 52α defined by the block Bα0 serving as a boundary. Furthermore, the reflective unit 5a is centrally located at a block Bβ0 extending along the α-axis direction and passing through the center of the reflective unit 5a in the β-axis direction, and is provided with two regions 51β, 52β separated by the central block Bβ0 serving as a boundary. The blocks Bβ included in the two regions 51β, 52β are structured to be line-symmetric with respect to the central block Bβ0, and thus, the conductor patches Pa are structured to be line-symmetric with respect to the central block Bβ0. That is, the reflecting unit 5a is structured to be line-symmetric not only with respect to the block Bα0 but also with respect to the block Bβ0.The block closest to block Bβ0, which serves as the boundary between regions 51β, 52β, is labeled Bβ1 and the remaining blocks are consecutively labeled Bβ2, Bβ3,... in order of increasing distance from block Bβ0.

[0036] As described in the first example, the blocks Bαi, Bβi are designed to have a structure that satisfies the conditions (2.1) to (2.4) described below. (2.1) The phase characteristics of the reflected wave are line-symmetric with respect to the block Bα0 and with respect to the block Bβ0. (2.2) Phase lags in the α-axis direction and the β-axis direction increase with increasing distance from the center of the antenna unit 4. (2.3) At the operating frequency fo, resonance occurs in the α-axis direction and the β-axis direction. (2.4) Among the blocks Bα, a phase difference Δθα between the adjacent blocks Bα is equal to or increases with the increased distance from the center of the antenna unit 4, and among the blocks Bβ, a phase difference Δθβ between the adjacent blocks Bβ is equal to or increases with the increased distance from the center of the antenna unit 4.

[0037] In this case, the lengths of two sides of each conductor patch Pa are changed in the α-direction and the β-direction, respectively, to adjust the phase of the reflected wave in four directions centrally located at the center of the antenna unit 4, that is, in ±-directions of the α-axis and ±-directions of the β-axis. 2-3. Third example

[0038] A third example corresponds to the first example in which the α-axis and the β-axis are interchanged with each other. That is, in the third example, the conductor patches Pa of the same size are arranged in series along the α-axis direction, and the conductor patches Pa arranged in series form the blocks Bβ. The reflective unit 5a is provided with the two regions 51β, 52β separated by the block Bβ0 and has a structure that is line-symmetric with respect to the block Bβ0. The blocks Bβi included in the reflective unit 5a are designed to have such a structure that satisfies the conditions (1.1) to (1.4) in the above-described first example in which α is interchanged with β. 3. Design

[0039] A configuration realizing the phase characteristics in the first to third examples will be described below. Specifically, with respect to the phases of reflected waves from the normal substrate, which is a substrate with only the antenna unit 4 installed thereon, the phase characteristics of reflected waves from the conductor patches Pa (hereinafter referred to as reflection characteristics) in Fig. 9. In this case, the intervals between the conductor patches Pa are fixed at 1 mm, and the size of each side of each of the conductor patches Pa in a direction involving a phase difference is changed between 2.5 mm and 3.3 mm.

[0040] As it is in Fig. As shown in Figure 9, with the conductor patches Pa having a constant size, the phase lag increases with an increased operating frequency fo. Furthermore, with a constant operating frequency fo, the phase lag increases with an increased size of each conductor patch Pa. However, the phase difference ranges from -180 degrees to 180 degrees, and a phase difference of -180 degrees and a phase difference of 180 degrees are equal to each other. In other words, the degree of difference of a phase between the normal substrate and the non-conductive substrate ranges from 0 degrees to 180 degrees. Once the phase difference reaches 180 degrees, the phase difference starts to decrease from 180 degrees. Therefore,When each conductor patch Pa has an excessively large size, the phase difference from the normal substrate becomes excessively small, reducing a suppression effect on the intensity of the reflected wave traveling in the same direction as the radiated wave. Specifically, when the size of the conductor patches Pa is larger than three-quarters of the effective wavelength, the phase difference from the normal substrate becomes excessively small. Therefore, the size of each side of each conductor patch Pa is desirably smaller than or equal to three-quarters of the effective wavelength.

[0041] In the first example and the third example, the size of the conductor patches Pa in the block Bα, Bβ serving as a reference is optionally set. Then, the size of the block Bα, Bβ adjacent to the block Bα, Bβ, whose size is determined, is set to obtain the phase difference Δθα, Δθβ preset for the operating frequency fo using the ratios shown in Fig. 9. The process is continuously repeated to design the size of each of the conductor patches Pa in all the blocks Bα, Bβ.

[0042] In the second example, the sizes in the α-direction and the β-direction of the conductor patch Pa serving as a reference are optionally set. Then, the size in the α-direction of the conductor patch Pa adjacent in the α-direction to the conductor patch Pa whose size is being determined is set to obtain the set phase difference Δθα using the relationships shown in Fig. 9, and the size in the β-direction of the conductor patch Pa adjacent in the β-direction to the conductor patch Pa whose size is being determined is set to obtain the set phase difference Δθβ using the relationships shown in Fig. 9. This process is performed continuously to shape the size of all the conductor patches Pa.

[0043] Fig. 10 shows example settings of the phases of reflected waves from the blocks Bα0, Bβ0 to Bα6, Bβ6 in the first example and the third example. Fig. 10 is a list indicating the phases in blocks Bα, Bβ for Comparative Example 1 using the normal substrate, Example 2 with the phase difference Δθα set to a constant value of 100 degrees, and Example 3 with the phase difference Δθβ set to a constant value of 100 degrees.

[0044] Fig. 11 shows an example design of the conductor patches Pa for the third example. Fig. Figure 11 is a list of the phases of reflected waves in blocks Bβ0 to Bβ5 and the sizes of the conductor patches Pa, resulting in the corresponding phase differences Δθβ for Comparative Example 1 and Examples 4 to 7. Examples 4 to 6 are examples with equal phase differences Δθβ of 30 degrees, 60 degrees, and 90 degrees, respectively. Example 7 is an example with an inclined phase difference Δθβ that increases in 30-degree increments. 4. Operation 4-1. Same phase difference

[0045] With the same phase difference Δθα, Δθβ, an incident wave from the Z-axis direction is reflected by the radiating surface 2a and the reflected wave includes a phase lag which increases steadily with the distance from the block Bα0, Bβ0, as shown in Fig. 12. However, the phase lag is proportional to the distance to the block Bα0, Bβ0. As a result, the reflected wave is reflected in a constant direction at a certain angle to the direction of arrival of the incident wave. In other words, the resulting reflection characteristics correspond to a reflection from a planar refracting substrate curved like a herringbone, chevron, or angle. 4-2. Inclined phase difference

[0046] On the other hand, with the inclined phase differences Δθα, Δθβ, an incident wave from the Z-axis direction is reflected by the reflecting surface 2a and the reflected wave includes a phase lag which increases steadily with the distance from the blocks Bα0, Bβ0, as shown in Fig. 13. However, the phase lag increases in an accelerated manner with increasing distance from the block Bα0, Bβ0. As a result, the reflected wave is reflected in a direction at a certain angle to the direction of arrival of the incident wave, with the angle of reflection steadily increasing with distance from the block Bα0, Bβ0. In other words, the resulting reflection characteristics correspond to a reflection from a curved substrate, with the reflected wave being scattered and traveling in different directions instead of in a constant direction. 5. Effects

[0047] The second embodiment described above in detail produces the following effects in addition to the effect (1) of the first embodiment. (2) Resonance can be caused in two directions different from the polarization direction Dan by shaping each conductor patch Pa like a rectangle and adjusting the lengths of the two adjacent sides of the rectangle. (3) When the phase difference Δθα, Δθβ of the reflected wave between the adjacent blocks Bα, Bβ is constant, a wavefront of a wave that is re-reflected by the reflecting unit 5 after penetrating the reflecting unit 5 is inclined from the center of the non-conductive substrate 2 toward the outside of the non-conductive substrate 2. This makes it possible to suppress the reflection intensity of the reflected wave traveling in the same direction as that of the radiated wave radiated from the antenna unit 4. (4) When the difference in the phase of the reflected wave between the adjacent blocks Bα, Bβ increases with the increased distance from the center of the antenna unit 4, the incident wave that has entered the reflecting unit 5a may be reflected in different directions instead of in a constant direction. That is, the reflected wave that has entered the reflecting unit 5a may be scattered. This makes it possible to suppress the reflection intensity of the reflected wave traveling in the same direction as that of the radiated wave radiated from the antenna unit 4. Furthermore, the reflection can be prevented from forming a strong beam different from the main beam in a specific direction. 6. Experiments

[0048] The results of a simulation for Comparative Example 1 and Examples 2, 3 described above are presented with reference to Fig. 14. In Fig. 14, the X-axis direction is defined as a reflection azimuth of 0 degrees, the α-axis direction is defined as a reflection azimuth of -45 degrees, and the β-axis direction is defined as a reflection azimuth of 45 degrees. Fig. Figure 14 indicates that when the reflection azimuth ranges from -30 degrees to 30 degrees, both Example 2 and Example 3 result in a significant suppression of the reflection intensity compared to Comparative Example 1. However, Example 2 and Example 3 result in the formation of large side bumps at a reflection azimuth of approximately -50 degrees and a reflection azimuth of approximately 50 degrees, respectively.

[0049] The results of a simulation for Comparative Example 1 and Examples 4 to 7 described above are presented with reference to Fig. 15 described. Fig. 15 indicates that, compared with Comparative Example 1, all of Examples 4 to 7 result in a significant suppression of the reflection intensity near the reflection azimuth of 0 degrees. However, Examples 4 to 6 with the same phase difference result in the formation of respective large side bumps within the range from a reflection azimuth of 20 degrees to a reflection azimuth of 60 degrees. On the other hand, Example 7 with the inclined phase difference does not result in the formation of any side bump.

[0050] In addition, the results of a simulation for Comparative Example 1, Comparative Example 2 and Example 8 with reference to Fig. 16 to 21. Comparative Example 2 is an example in which the conductor patches of the same size are arranged in series along the Y-axis direction and the blocks are arranged or lined up along the X-axis direction such that the resonance direction of the conductor patches is the same as the polarization direction Dan, as shown in Fig. 16. In Comparative Example 2, the phase lag or delay of the reflected wave in the polarization direction Dan increases with increasing distance from the antenna unit, and the phase differences between the blocks are equal. Example 8 corresponds to the second example, which includes the same phase difference.

[0051] Fig. 17 indicates that, compared with Comparative Example 1, both Comparative Example 2 and Example 8 result in significant suppression of the reflection intensity near the reflection azimuth of 0 degrees. However, in Comparative Example 2, due to the suppression of the reflection intensity near the reflection azimuth of 0 degrees, the reflection intensity within the range from the reflection azimuth of 30 degrees to the reflection azimuth of 90 degrees is higher than in Comparative Example 1. In contrast, in Example 8, the reflection intensity is suppressed even more significantly over the entire reflection azimuth than in Comparative Example 1.

[0052] A comparison of Fig. 18 to 20 indicate that, in Comparative Example 1 and Comparative Example 2, a Y component, which is a component in a direction 90° to a polarization direction Dan, is very small compared to an X component, which is a component in the polarization direction Dan. On the other hand, compared with Comparative Example 1 and Comparative Example 2, Example 8 results in a very large Y component. This indicates that the polarization direction of the incident wave that has entered the reflecting unit 5a is rotated by 45° with respect to the polarization direction Dan, causing a part of the X component of the incident wave to be converted into a Y component before the incident wave is reflected.

[0053] In addition, as it is in Fig. 21, which compares a case with a bumper with a case without a bumper, a gain variation of up to about 4 dB occurred in Comparative Example 1, whereas the gain variation was reduced to about 3 dB in Comparative Example 2. Furthermore, in Example 8, the gain variation was reduced to about 1.5 dB, which corresponds to an improvement of about 1.5 dB in the gain variation compared to the gain variation in Comparative Example 2. Other embodiments

[0054] The embodiments of the present disclosure have been described. However, the present disclosure is not limited to the above-described embodiments, and many variations can be made to the embodiments. (a) In the above-described embodiments, the angle θr between the resonance direction of the conductor patches P, Pa and the polarization direction Dan is 45°. However, the present disclosure is not limited to this. For example, the angle θr may be 30°, as shown in Fig. 22, or 60° as shown in Fig. 23. As shown in Fig. As shown in Figure 24, in a case where the angle θr is 30° or 60°, the reflection intensity is high within the range from a reflection azimuth of 10 degrees to the reflection azimuth of 60 degrees compared to the case where the angle θr is 45°. However, the reflection intensity near the reflection azimuth of 0 degrees is reduced to a value close to a value to which the reflection intensity has been reduced in the case where the angle θr is 45°. Therefore, an angle θr of 45° enables maximizing the suppression of adverse effects of the reflected wave, but the suppression effect on the adverse effects of the reflected wave can also be exerted by setting the angle θr to a different value, such as 30° or 60°. (b) As in Fig. 25 and Fig. As shown in Figure 26, instead of the rectangular conductor patches P, Pa, cutout-type conductor patches Pb, each shaped like a rectangle with at least one corner thereof cut out, may be used. When a distance between opposite cutout portions of the conductor patch Pb is denoted as a2 and a distance between two vertices adjacent to the cutout portions is denoted as b2, a2 ≠ b2. By having such a cutout shape, the conductor patch Pb exhibits a circular polarization characteristic. Consequently, the incident wave that has entered the reflecting unit 5 can be reflected with the polarization direction rotated therefrom without the need to tilt the polarization direction Dan, all from the sides of each conductor patch Pb except for the cutout portions. Furthermore, the phase lag can be reduced.The phase delay of the reflected wave can be increased with increasing distance from the antenna unit 4 by changing the size of each cutout conductor patch Pb among the blocks formed along the Y-axis direction. Therefore, effects similar to those of the above-described embodiments can be produced. The conductor patch Pb can have any shape, with at least one corner thereof cut out.

[0055] In addition, a plurality of regions may be provided in one reflective unit 5b, and at least either the size of a cutout portion or the positions of the conductor patch Pb where the cutout portion is formed among the conductor patches Pb may be changed. Fig.25, the reflecting unit 5b is provided with four regions centrally located around the antenna unit 4. The conductor patches Pb in an upper right region and a lower left region are each formed like a rectangle, with an upper left corner and a lower right corner cut out therefrom. The conductor patches Pb in an upper left region and a lower right region are each shaped like a corner, with an upper right corner and a lower left corner cut out therefrom. Varying the positions where the cutout portions are formed among the regions enables variation of a rotation direction of a circularly polarized wave, that is, whether the polarized wave is rotated clockwise or counterclockwise, among the regions.Furthermore, varying the size of a section among the regions allows for varying the magnitude of rotation of the polarized wave among the regions. The number of regions is not limited to four, and any number of regions can be formed.

[0056] (c) In the embodiments described above, the lagging phase is adjusted by varying the size of the conductor patch P or the conductor patch Pa, wherein the constant gap is formed between the conductor patches P, or wherein the constant gap is formed between the adjacent conductor patches Pa included in the different adjacent blocks Bα, Bβ. However, the present disclosure is not limited to this. The lagging phase can be adjusted by varying the gap between the conductor patches P or the gap between the adjacent conductor patches Pa included in the different adjacent blocks Bα, Bβ. With a constant operating frequency fo, the phase lag increases with a reduced gap.

[0057] (d) The conductor patches P, Pa do not need to be rectangular. The conductor patches P, Pa can, for example, be shaped like rods. If the conductor patches P, Pa are shaped like rods, the conductor patches P, Pa can be arranged such that a longitudinal direction of each rod-shaped conductor patch is inclined to the polarization direction Dan.

[0058] (e) A plurality of functions provided in a component of each of the above-described embodiments may be performed by a plurality of components, or a function provided in a component may be achieved by a plurality of components. Furthermore, a plurality of functions provided in a plurality of components may be performed by one component, or a function implemented in a plurality of components may be achieved by one component. Alternatively, the configuration of each of the above-described embodiments may be partially omitted. Alternatively, at least a part of the configuration of each of the above-described embodiments may be added to the configuration of another of the above-described embodiments, or may replace a corresponding part thereof.The embodiments of the present disclosure correspond to all aspects contained in technical concepts specified solely by the language in the claims.

[0059] (f) The present disclosure can be implemented in various forms, such as, in addition to the antenna apparatus described above, a system including the antenna apparatus described above as a component, and a method for suppressing possible interference caused by an unwanted reflected wave.

Claims

[1] Antenna apparatus (1, 1A, 1B) mounted in a bumper of a vehicle, the antenna apparatus comprising: a non-conductive substrate (2), a base plate (3) provided on a first surface (2b) of the non-conductive substrate and configured to serve as an antenna bottom surface, an antenna unit (4) provided on a second surface (2a) of the non-conductive substrate and having an antenna pattern configured to serve as an antenna array, and a reflecting unit (5, 5a, 5b) arranged to surround the antenna unit, the reflecting unit including a plurality of conductor patterns serving as a reflector, wherein each of the plurality of conductor patterns (P, Pa, Pb) has a size smaller than an effective wavelength at a preset operating frequency of the antenna unit and is structured to generate resonance in a resonance direction different from a polarization direction of a radio wave transmitted and received by the antenna unit. [2] The antenna apparatus according to claim 1, wherein the plurality of conductor patterns (Pa, Pb) are structured such that a phase lag of a reflected wave increases with an increased distance from a center of the antenna unit in the resonance direction from the center of the antenna unit. [3] The antenna apparatus according to claim 2, wherein each of the plurality of conductor patterns includes a plurality of conductor patches (Pa) each having a rectangular shape, and the plurality of conductor patches are arranged such that one side of the rectangle is inclined at a same inclination angle as the polarization direction, and structured such that, at the operating frequency, the resonance direction of the conductor patches is a direction along at least one side of the rectangle. [4] An antenna apparatus according to claim 3, wherein each of said plurality of conductor patches (Pa) is structured in which, at the operating frequency, two directions along two adjacent sides of the rectangle are given as a resonance direction. [5] The antenna apparatus according to claim 3 or 4, wherein the plurality of conductor patches are formed of a plurality of blocks arranged along the resonance direction and are structured such that, for respective reflected waves from the plurality of blocks, each block has a different phase at the operating frequency, and such that, for each set of adjacent blocks, a difference in the phase of the reflected wave between the adjacent blocks is constant. [6] The antenna apparatus according to claim 3 or 4, wherein the plurality of conductor patches form a plurality of blocks arranged along the resonance direction and are structured such that for respective reflected waves from the plurality of blocks, each block has a different phase at the operating frequency and the difference in the phase of the reflected wave between the adjacent blocks increases with the increased distance from the center of the antenna unit. [7] An antenna apparatus according to claim 2, wherein each of said plurality of conductor patterns (Pb) includes conductor patches each shaped like a rectangle with at least one corner thereof cut out. [8] The antenna apparatus according to claim 7, wherein the plurality of conductor patterns have a circular polarization characteristic based on the cutout shape. [9] The antenna apparatus according to claim 7 or 8, wherein the reflecting unit includes a plurality of regions, and the plurality of conductor patterns are structured such that at least one of the position at which the cutout shape is formed and the size of a cutout is different for each of the plurality of regions. [10] The antenna apparatus according to any one of claims 3 to 9, wherein the plurality of conductor patches have the phase of the reflected wave adjusted by changing the size of the conductor patch along the resonance direction. [11] The antenna apparatus according to claim 10, wherein the plurality of conductor patches has a length of one side of the rectangle, which is changed along directions of two adjacent sides of the rectangle to adjust the phase of the reflected wave in four directions centrally located around the antenna unit. [12] The antenna apparatus according to any one of claims 3 to 11, wherein the plurality of conductor patches has a change interval between the conductor patches in the resonance direction to adjust the phase of the reflected wave. [13] The antenna apparatus according to any one of claims 1 to 12, wherein an angle between the polarization direction of the radio wave and the resonance direction is 45 degrees. [14] An antenna apparatus according to any one of claims 1 to 13, wherein each of the plurality of conductor patterns has a size less than or equal to three-quarters of the effective wavelength at the operating frequency.

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