JP2010118778A - Planar antenna and radar device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems that since a distance between adjacent antennas is narrowed, physical space disappears and the installation of a radio wave absorber between the adjacent antennas is made impossible, isolation is not secured, distortion may be generated in an antenna pattern and necessary gain and phase characteristics corresponding to an azimuth angle are not secured. <P>SOLUTION: A planar antenna includes a plurality of antennas arranged on an antenna substrate and a shield plate arranged in a space between adjacent antennas, wherein the shield plate is arranged separately from the antenna substrate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a planar antenna and a radar apparatus using the planar antenna, and more particularly to a planar antenna and a radar apparatus in which a shield plate is provided between antenna elements.

  The millimeter wave is a frequency band of 30 GHz to 300 GHz (wavelength 10 mm to 1 mm), and since the wavelength is short, there is an advantage that the millimeter wave radar can be miniaturized and is not easily influenced by the weather. Using this, millimeter wave radar is being researched and developed as a radar for automobiles. A planar antenna is mainly used in this millimeter wave radar.

  A schematic diagram of the structure of a conventional planar antenna is shown in FIG. 1 (for example, Patent Document 1). In this planar antenna, an antenna substrate 101 is configured by bonding a dielectric 105 on a grounding conductor plate 106 and bonding a copper foil or the like thereon. The planar antenna includes a reception antenna 102 and a transmission antenna 103 on the same plane of the antenna substrate 101. Further, a radome 104 is provided so as to cover them.

  When there is no obstacle such as a shield plate between the transmission antenna 102 and the reception antenna 103 and there is a space, the radio wave radiated from the transmission antenna 102 propagates through the space and enters the reception antenna 103. . In this way, radio waves are transmitted from one antenna to another antenna, which causes a problem that so-called isolation is lowered.

  Therefore, a radio wave absorber 107 is provided so that the radio wave transmitted by the transmitting antenna 102 is transmitted through the space and does not enter the receiving antenna 103. Of the radio waves radiated from the transmitting antenna 102, when there is no radio wave absorber 107, the radio wave incident on the receiving antenna 103 is absorbed by the radio wave absorber 107, and the magnitude thereof is attenuated. Improved characteristics.

  On the other hand, a schematic diagram of a planar antenna used in a conventional millimeter wave radar is shown in the perspective view of FIG. A plurality of antenna patches 2 are arranged on an antenna substrate 1 made of a dielectric. Each antenna patch is formed so that its shape gradually changes from a rectangle to a square. A plurality of antenna patches 2 arranged in the y-axis direction in FIG. 2 are connected by a conductor to constitute one antenna. As a result, the longitudinal direction of the antenna is substantially the same as the y-axis direction in the figure. In FIG. 2, three antennas 31, 32, and 33 are arranged in the x-axis direction.

  A ground conductor 4 made of copper foil is attached to the lower surface of the antenna substrate 1. The antenna substrate 1 is placed on a holding plate 6 made of aluminum provided with waveguides 51, 52 and 53. The antenna substrate 1 is installed on the holding plate 6 by screwing together the screw holes 71 to 74 provided in the antenna substrate 1 and the screw holes 81 to 83 provided in the holding plate 6 and fixing them. .

JP-A-4-140905

Here, in the conventional planar antenna for millimeter wave radar, when wide-angle detection is required in the horizontal direction, an antenna that does not cause phase folding in the monopulse detection method is effective. For this purpose, it is necessary to narrow the center distance of the receiving antenna to about ½ (about 2 mm) of the receiving wavelength λ. In this case, as shown in the plan view of the conventional planar antenna shown in FIG. 3, the distance d ₁ between the antennas 31 and 32 becomes as narrow as about 2 mm. Even in such a configuration, it is desirable to install a radio wave absorber between adjacent antennas in order to avoid electrical coupling through a space and ensure isolation. However, since the distance between adjacent antennas becomes narrow and there is no physical space, a radio wave absorber cannot be installed between adjacent antennas. As a result, the isolation cannot be secured, the antenna pattern is distorted, and the necessary gain and phase characteristics corresponding to the azimuth angle cannot be secured.

  The planar antenna of the present invention has a plurality of antennas disposed on an antenna substrate and a shield plate disposed between adjacent antennas, and the shield plate is disposed separately from the antenna substrate. It is characterized by that.

  Even when the antennas have such a narrow antenna interval that the shield plates cannot be installed directly on the antenna substrate, the shield plates can be installed and the isolation can be ensured.

  Hereinafter, a planar antenna and a radar apparatus according to the present invention will be described with reference to the drawings. However, it should be noted that the technical scope of the present invention is not limited to these embodiments, but extends to the invention described in the claims and equivalents thereof.

  FIG. 4 is a perspective view of the planar antenna according to the first embodiment of the present invention. The same components as those of the conventional planar antenna shown in FIG. The planar antenna of the present invention includes a holding plate 6, an antenna substrate 1 arranged on the holding plate 6, a plurality of antennas 31 to 34 arranged on the antenna substrate 1, and a plurality of adjacent antennas (FIG. 5). , The shield plate 9 is disposed in the space between the antenna 32 and the antenna 33. The shield plate 9 is held by a plurality of support members 11 to 15 provided on the holding plate 6 and is arranged apart from the antenna substrate 1 as shown in the cross-sectional view of FIG. The shield plate 9 has a strip shape and extends in a substantially vertical direction with respect to the antenna substrate 1. Further, the longitudinal direction of the shield plate 9 is substantially the same as the y-axis direction of FIG. The shield plate 9 is made of a laminate of a dielectric and a metal and can absorb millimeter wave radio waves. By adopting such a configuration, even when the interval between the antennas is narrow and the shield plate cannot be installed directly on the antenna substrate, the shield plate can be floated and arranged. As a result, it is possible to ensure isolation between adjacent antennas.

  Next, the manufacturing method of the planar antenna of this invention is demonstrated in detail. First, a plurality of antenna patches 2 are patterned on a dielectric antenna substrate 1 using a copper foil or the like. The antenna patch is arranged so as to gradually change from a rectangle to a square. Further, the plurality of antenna patches 2 arranged in the y-axis direction in FIG. 4 are connected by a conductor to constitute one antenna. In FIG. 4, four antennas 31 to 34 are arranged in the x-axis direction.

  Next, a ground conductor 4 made of copper foil is attached to the lower surface of the antenna substrate 1. Thereafter, a plurality of holes 21 to 25 are provided so that the support member for holding the shield plate penetrates the antenna substrate 1. The holes 21 to 25 are preferably formed so as not to be in contact with the antenna patch 2 and are formed in the gap between the antenna patches 2. By providing a hole for penetrating the support member in the gap between the antenna patches 2, the support member for holding the shield plate is not in contact with the antenna patch even when the distance between adjacent antennas is narrow. Can be arranged. Furthermore, screw holes 71 to 74 for fixing the antenna substrate 1 to the holding plate 6 by screws are provided.

  Next, the holding plate 6 made of aluminum provided with the waveguides 51 to 54 is prepared. A plurality of support members 11 to 15 for holding the shield plate 9 are arranged on the holding plate 6. The support member may be integrally formed with the holding plate 6 by cutting out the holding plate 6 or the support member may be retrofitted to the holding plate 6. The shape of the support member is not particularly limited as long as the shield plate 9 can be held, but it is desirable that the support member is as thin as possible so as not to affect the characteristics of the antenna. Here, an example in which an elongated cylindrical shape such as a pin is employed is shown.

  Furthermore, screw holes 81 to 84 for fixing the antenna substrate 1 to the holding plate 6 by screwing are formed. Next, the antenna substrate 1 is disposed on the holding plate 6 so that the support member penetrates the holes 21 to 25 for penetrating the support member of the antenna substrate 1. At this time, the cross-sectional shape of the support member and the cross-sectional shape of the hole are substantially equal, and the position of the support member of the holding plate 6 and the position of the hole of the antenna substrate 1 are set to a desired positional relationship, whereby the antenna substrate Accurate positioning to one holding plate 6 can be easily performed. As a result, the alignment process that has been performed when there is no support member can be omitted. Next, the antenna substrate 1 is fixed to the holding plate 6 by screwing together the screw holes 71 to 74 provided in the antenna substrate 1 and the screw holes 81 to 84 provided in the holding plate 6.

Thereafter, the shield plate 9 provided with holes into which the support members 11 to 15 are inserted is installed so that the support members 11 to 15 are inserted. FIG. 5 shows a cross-sectional view taken along the center line (II in FIG. 4) in the longitudinal direction of the shield plate 9 as viewed from the positive direction of the x-axis with the shield plate 9 installed. On the holding plate 6, the ground conductor 4, the antenna substrate 1, and the antenna 33 are arranged. Further, as shown in FIG. 5, support members 11 to 15 are provided on the holding plate 6, and the support members 11 to 15 and a plurality of holes provided in the shield plate 9 are fitted to each other to form a shield plate. 9 is held. At this time, the shield plate 9 is held so as to be separated from the surface of the antenna 2 on the antenna substrate 1 by a predetermined distance d ₂ . Here, when the antenna 33 and the shield plate 9 are in contact with each other, the reception characteristics are deteriorated. However, if the antenna 33 is too far from the upper surface of the antenna 33, the function as a shield cannot be sufficiently performed. Therefore, in order to maximize the function as a shield between antennas, it is preferable to set the distance d ₂ to a predetermined distance according to the wavelength received by the antenna. For example, it is preferable to set the distance d ₂ to ¼ or less of the minimum value of the wavelength λ received by the antenna.

  Thus, by arranging the shield plate 9 away from the antenna substrate 1, even when the antenna interval is narrow and the shield plate cannot be directly installed on the antenna substrate, the shield plate can be installed between adjacent antennas. Isolation characteristics can be improved.

  Next, a planar antenna according to a second embodiment of the present invention is described. FIG. 6 is a cross-sectional view taken along the plane passing through the center of the shield plate as in FIG. The difference from the first embodiment is that support members for holding the shield plate 9 are provided only at two locations on both ends of the shield plate 9. With such a configuration, even if the support member is formed of a conductor such as aluminum, the distance between the antenna patch and the support member can be increased, so that interference with the antenna patch 33 is minimized. be able to.

  Next, a radar apparatus using the planar antenna described in the first embodiment will be described. FIG. 7 is a perspective view showing the configuration of the radar apparatus. As shown in FIG. 7, after the antenna substrate 1 is screwed to the holding plate 6 and the shield plate 9 is installed, a resin radome 10 is arranged so as to cover them. The radome 10 is screwed to the antenna substrate 1 and the holding plate 6 using screw holes 91 to 93 provided at four corners.

  FIG. 8 shows a cross-sectional view of a plane passing through the center line (II-II) of the shield plate 9 when the radome 10 is screwed to the antenna substrate 1 and the holding plate 6. As shown in FIG. 8, the radome 10 is preferably arranged so as to be in contact with the shield plate 9 provided on the antenna substrate 1. With such a configuration, it is possible to increase the shielding efficiency of radio waves between adjacent antennas, and it is possible to prevent the shield plate from being displaced due to vibration received when the radar apparatus is mounted on a vehicle.

  Finally, as shown in FIG. 7, the circuit board 20 is connected to the antenna board 1 via the holding plate 6, and then the whole is mounted on the housing 30 to complete the radar apparatus.

  As described above, in the above-described embodiments, only one shield plate 9 is disposed between adjacent antennas. However, a plurality of shield plates may be disposed.

It is a perspective view explaining the internal structure of the conventional planar antenna. It is a perspective view of the conventional planar antenna. It is a top view of the conventional planar antenna. It is a perspective view of the planar antenna of Example 1 of this invention. It is sectional drawing of the planar antenna of Example 1 of this invention. It is sectional drawing of the planar antenna of Example 2 of this invention. It is a perspective view of the radar apparatus of this invention. It is sectional drawing of the planar antenna of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna board 2 Antenna patch 31-34 Antenna 4 Ground conductor 51-54 Waveguide 6 Holding plate 9 Shield plate 10 Radome 11-15 Support member

Claims (5)

A plurality of antennas arranged on an antenna substrate;
A shield plate disposed between the plurality of adjacent antennas,
The planar antenna according to claim 1, wherein the shield plate is spaced apart from the antenna substrate.   The planar antenna according to claim 1, wherein the shield plate is separated from the antenna substrate by a predetermined distance according to a minimum wavelength of radio waves received by the plurality of antennas. The planar antenna further includes a holding plate that holds the antenna substrate,
The planar antenna according to claim 1, wherein the shield plate is held by a plurality of support members provided on the holding plate. The antenna substrate has a hole for penetrating the support member;
The planar antenna according to claim 1, wherein the support member determines a positional relationship between the holding plate and the antenna substrate. A holding plate;
An antenna substrate disposed on the holding plate;
A plurality of antennas disposed on the antenna substrate;
A shield plate disposed in a space between the plurality of adjacent antennas;
A radome disposed so as to contact the shield plate,
The radar apparatus according to claim 1, wherein the shield plate is disposed apart from the antenna substrate.

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