JP2000137068A - Antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance azimuth detection performance by reducing the amount of coupling between sending and receiving sides by means of simple constitution. SOLUTION: Two opposed shield plates 13, 14 are provided between a sending antenna 11 and a receiving antenna 12 while being spaced apart from each other by, e.g. a wavelength of 0.75 or more, preferably a wavelength of 1.25 to 2.5. Thus the amount of coupling between the sending and receiving sides is reduced to reduce the amount by which electric waves radiated from the sending antenna go around the receiving antenna.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna apparatus for improving the distance detecting performance without reducing the azimuth detecting ability by reducing transmission / reception coupling between a transmitting antenna and a receiving antenna.

[0002]

2. Related Background Art Conventionally, in an antenna device, coupling between transmission and reception between a transmission antenna and a reception antenna, that is, sneaking of a radio wave transmitted from the transmission antenna to the reception antenna is a serious problem. Therefore, as a conventional device, for example, as in the invention described in Japanese Patent Publication No. 5-4036 or Japanese Patent Application Laid-Open No. 7-5243, one shield plate is arranged between a transmitting antenna and a receiving antenna to wrap around. Was being prevented.

[0003]

However, if priority is given to the angle detection accuracy and the antenna dimensions, the reduction in the amount of coupling by the above-mentioned shield plate is reduced, and the wraparound is not sufficiently removed, and the azimuth detection capability is reduced. There was a problem.
Therefore, as in the invention described in, for example, Japanese Patent Application Laid-Open No. 8-293807, a removing device in which a pilot signal for identification is superimposed on a transmission wave using an electric circuit to enable identification of an interference wave at the time of reception. was there. However, since this removal device needs to be configured by an electric circuit,
There was a problem that the structure became complicated and the manufacturing cost became expensive.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an antenna device capable of reducing directional coupling with a simple configuration and improving azimuth detection performance.

[0005]

In order to achieve the above object, the present invention provides a transmitting antenna for transmitting a radio wave, and a receiving antenna for receiving a reflected wave of the radio wave from an object, wherein the transmitting antenna and the receiving antenna are provided. There is provided an antenna device in which a plurality of shielding plates disposed to face each other are separated by a predetermined distance. In particular, it is preferable that the shield plate is provided between the reception antennas and the transmission antennas separated by, for example, 0.75 wavelength or more.

That is, by providing a shielding plate between a transmitting antenna and a receiving antenna at a predetermined interval, the amount of coupling between the transmitting and receiving antennas is reduced, thereby reducing the amount of radio waves radiated from the transmitting antenna to the receiving antenna. . It is also preferable to provide radio wave absorbers on the upper and lower surfaces of the antenna device to absorb unnecessary reflected waves, thereby reducing the amount of coupling between antenna transmission and reception without lowering the azimuth detection performance.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of an antenna device according to the present invention will be described with reference to FIGS. FIG.
FIG. 2 is a front view showing a schematic configuration for explaining the principle of the antenna device according to the present invention, and FIG. 2 is a side view thereof.
This antenna device is used, for example, in a millimeter-wave band radar device.
And two shielding plates 13 and 14 provided so that the transmitting and receiving antennas 11 and 12 are separated from each other by a predetermined distance d.
Jig 1 in which an electronic circuit or the like for driving drive 12 is stored
And 5. Although a radome for protecting the antenna device is originally provided so as to cover the entire antenna, the radome is omitted here for convenience of explanation. In the present embodiment, the distance is the distance d, which is the distance between both antenna edges.

The transmitting antenna 11 is, for example, about 14
mm, about 69mm in height, about 9mm in height,
The receiving antenna 12 has a length of about 22 mm and a width of about 6 mm, for example.
It has an outer dimension of 3 mm and a height of about 9 mm.
Are horizontally arranged. The shielding plates 13 and 14
The transmission antenna 11 and the reception antenna 12 are separately arranged to face each other, and are made of, for example, an aluminum material. (About 17 mm).

[0009] Here, the present inventors have proposed a transmitting / receiving antenna 1.
In order to investigate the relationship between the amount of coupling between 1 and 12 and the distance d,
The distance d between the transmitting and receiving antennas was increased in the direction of the arrow shown in FIG. 1, and the amount of coupling at that time was measured. At the time of the measurement, the measurement was performed for one shield plate, that is, only the shield plate 14 on the receiving antenna 12 side and the two shield plates described above.
The purpose of this measurement was to observe the tendency of the amount of coupling between one and two shielding plates, and the distance d was 2 mm.
10 mm to 22 mm at 1 mm intervals between 10 mm and 10 mm
It is assumed that the measurement is performed at 2 mm in between. The measurement results are shown in FIGS.

FIG. 3 and FIG. 4 are relationship diagrams showing the relationship between the coupling amount in the above-mentioned frequency band and the distance (interval) d between the antenna edges when one and two shielding plates are used. As is apparent from these figures, the coupling amount can be further reduced when one shielding plate is attached to each of the transmitting antenna and the receiving antenna side than when one shielding plate is attached to the receiving antenna side. confirmed.

Next, the inventors of the present invention consider each of the measurement results when the center frequency is 76.5 GHz as a representative example in FIG. That is, referring to FIG. 5, in the case of one shield plate, the coupling amount increases as the distance d between the transmitting and receiving antennas increases from 2 mm, and gradually decreases after the distance d exceeds 10 mm. On the other hand, when the number of shielding plates is two, the amount of coupling decreases as the distance d between the transmitting and receiving antennas increases from 2 mm, and becomes smaller as the distance d exceeds 3 mm than when the distance d exceeds 3 mm. 7mm
From around the point where it exceeds -80 dB. And
It can be seen that when the distance d is 7 mm to 18 mm, the coupling amount is reduced by about 15 dB or more compared to the case of one sheet.

Therefore, when two shielding plates are attached between the transmitting and receiving antennas, the amount of coupling between the transmitting and receiving antennas can be reduced as compared with the case where one shielding plate is used, and the distance d between the transmitting and receiving antennas
Is greater than 3 mm, it has been recognized that the effect is greater. That is, it has been confirmed that, where λ is the wavelength corresponding to the center frequency of the used band, it is preferable that the interval d be 0.75λ or more.

From these measurement results, when, for example, the distance between the transmitting and receiving antennas is reduced and the radar front end is reduced, two shielding plates are attached between the transmitting and receiving antennas, compared with a case where only one is attached. It can be seen that the amount of coupling between the transmitting and receiving antennas can be significantly reduced. Therefore, the present inventors have found that the distance d between the transmitting and receiving antennas is 0.75λ or more, preferably 1.2
It was confirmed that the antenna device of the present invention could be used under the optimum conditions for a millimeter wave band radar device by attaching two shielding plates so as to be in the range of 5λ to 5λ.

By the way, the above-mentioned antenna device may be used for a radar device mounted on an automobile. In such a radar device, since a target area for detecting an object such as a moving object or an obstacle on a road is generally in a range of about 50 to 200 m in front of the vehicle, a radio wave in a millimeter wave band having a frequency of 30 GHz to 300 GHz is generated. Used. Further, as an antenna device used in this radar device, a multi-beam system exclusively using a plurality of antennas is often adopted because a plurality of objects are simultaneously detected.

Such a multi-beam type antenna device is set in accordance with one transmitting antenna for obtaining a transmitting beam having a beam width covering a wide scanning target range for object detection, and azimuth detection accuracy in the scanning target range. And a plurality of receiving antennas for obtaining a plurality of receiving beams having different beam widths. FIGS. 6 and 7 are a front view and a side view, respectively, showing a configuration of an embodiment in which the multi-beam antenna device is configured using the antenna device according to the present invention. Referring to FIGS. 6 and 7, the antenna apparatus of the present embodiment is configured to set one transmission antenna 21 including a planar antenna having a wide-angle beam covering a scanning target range and a transmission area of a beam of the transmission antenna 21 horizontally. Receiving antennas 22 to 2 for obtaining a narrow-width beam divided into five directions
6 are provided. The two shielding plates 27 and 28 are provided on the transmitting side and the receiving side, and are arranged to face the transmitting antenna 21 and the receiving antennas 22 to 26 at a predetermined distance d. These components are mounted on a jig 29 similar to the jig 15 shown in FIGS. 1 and 2, and are also covered with a protective radome 30 and mounted on, for example, a bumper of an automobile. In FIG. 6,
The radome 30 is omitted to show the arrangement of each antenna.

The transmitting antenna 21 and the receiving antenna 22 at the center have the same dimensions as the respective antennas shown in FIG.
It has outer dimensions of 5λ, about 11λ in width, and about 2.5λ in height. Also in this embodiment, the transmission antenna 21 is arranged vertically and the reception antennas 22 to 26 are arranged horizontally. As described above, the receiving antennas 22 to 26 are arranged at different angles in order to divide the transmission area of the transmission antenna 21 into five parts in the horizontal direction. That is, the receiving antenna 22 is arranged so as to receive a reflected beam from the central area of the transmission area at an inclination angle of 0 degree. The receiving antennas 23 and 24 are arranged so as to receive reflected beams from a predetermined area adjacent to the left and right of the central area monitored by the receiving antenna 22 at an inclination angle of 5 degrees to the right and left, respectively. The receiving antennas 25 and 26 have a tilt angle of 9 degrees to the right and left, respectively, and are arranged so as to receive reflected beams from left and right adjacent areas of the predetermined area monitored by the receiving antennas 23 and 24.

The shielding plate 27 has a thickness of about 0.125λ, the shielding plate 28 has a thickness of about 0.25λ, and both have a length of about 19
λ and the mounting height D have an outer dimension of about 2λ from the antenna. The mounting height D is set to about 2λ because it depends on the height of the radome. The distance d between the transmitting and receiving antennas is preferably set in the range of 1.25λ to 5λ as described above. Since the installation space of the antenna device is limited, it is preferable to set the antenna device in the range of 1.25λ to 2.5λ. Furthermore, in such an antenna device, the present inventors set the target value of the coupling amount between the transmitting and receiving antennas to -78 dB or less.

Therefore, the present inventors set the wavelength λ to 4 mm, set the interval d between the transmitting and receiving antennas to 2λ = 8 mm, and set the center frequency from 76.25 GHz to 7
The coupling amount between the transmitting and receiving antennas when the frequency was changed to 6.75 GHz was measured. As a result, the coupling amount is -86 dB or less for the receiving antennas 22 and 24, -84 dB or less for the receiving antenna 23, and -83 dB for the receiving antenna 25.
It is less than dB and less than -87 dB with the receiving antenna 26, and all of them have resulted in clearing the target coupling amount of -78 dB.

As described above, in this embodiment, the coupling between transmission and reception is reduced without deteriorating the azimuth detection performance, and the transmission side is reduced from the transmission side to the reception side by a simple configuration in which the shielding plate is provided at a predetermined distance between the transmitting and receiving antennas. Was able to reduce the wraparound of radio waves to In addition to the above-described embodiment, the present inventors also have, for example, as shown in FIG.
It is also possible to arrange the absorbers 31 and 32 for absorbing unnecessary radio waves in the gap between the lower and upper portions 26 and a radome (not shown). Also in the measurement result in this case, the coupling amount is equal to the receiving antennas 22 to 26.
Respectively, -79 dB or less, -82 dB or less, -89
dB or less, -83 dB or less, -91 dB or less. Also in this case, the target coupling amount can be cleared, coupling between transmission and reception is reduced, and unnecessary radio wave from the transmission side to the reception side is reduced. I was able to.

As described above, in the antenna device according to the present invention, the amount of coupling between transmission and reception can be reduced without increasing the size of the antenna, so that the azimuth detection accuracy can be improved. A high-performance antenna device suitable for a vehicle-mounted radar device can be realized in a compact manner. Further, the present invention is not limited to these embodiments. For example, in addition to the configuration of the embodiment, the coupling amount between the transmitting and receiving antennas can be suppressed by covering the receiving antenna with a metal plate or a metal tape. Becomes Also, the antenna device according to the present invention can be used for a multi-beam type antenna device in which various numbers of receiving antennas are arranged.

[0021]

As described above, according to the present invention, since a plurality of shielding plates are provided opposite to each other between the transmitting antenna and the receiving antenna and are separated from each other by at least 0.75 wavelength, a simple structure is provided. Reduce the coupling between the sending and receiving by the configuration,
The azimuth detection performance can be improved, and for example, a great effect is obtained as an antenna device in a vehicle-mounted radar device.

In the antenna device, since an absorber for absorbing unnecessary radio waves is arranged at least above and below the receiving antenna, the amount of coupling between antenna transmission and reception can be reduced without lowering the azimuth detection performance.

[Brief description of the drawings]

FIG. 1 is a front view showing a schematic configuration for explaining the principle of an antenna device according to the present invention.

FIG. 2 is a side view of the same.

FIG. 3 is a relationship diagram showing a relationship between a coupling amount in a millimeter wave band and a distance between antenna edges in the case of one shielding plate.

FIG. 4 is a relationship diagram showing a relationship between a coupling amount and a distance between antenna edges in a millimeter wave band when two shielding plates are used.

5 is a relationship diagram showing a relationship between a coupling amount in a predetermined millimeter wave band and a distance between antenna edges when one and two shielding plates shown in FIGS. 3 and 4 are used;

FIG. 6 is a front view showing a configuration of an embodiment when the antenna device of the multi-beam system is configured using the antenna device according to the present invention.

FIG. 7 is a side view of the same.

FIG. 8 is a front view showing the configuration of another embodiment when a multi-beam type antenna device is similarly configured.

[Explanation of symbols]

 11, 21 Transmitting antenna 12, 22 to 26 Receiving antenna 13, 14, 27, 28 Shielding plate 15, 29 Jig 30 Radome 31, 32 Absorber d Distance between transmitting and receiving antennas

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Dai Kojima 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. F-term (reference) 5J020 BD01 BD02 EA01 EA06 EA09 5J046 AA04 AA12 AA19 RA03 UA02 UA03 UA04 5J070 AD06 AE01 AF03 AK40

Claims (3)

[Claims] 1. An antenna device having a transmitting antenna for transmitting a radio wave and a receiving antenna for receiving a reflected wave of the radio wave from an object, wherein the antenna device is opposed to the transmitting antenna and the receiving antenna and is separated from each other by a predetermined distance. An antenna device comprising a plurality of shield plates provided. 2. The antenna device according to claim 1, wherein the shielding plates are arranged so as to be separated by at least 0.75 wavelength or more. 3. The antenna device according to claim 1, wherein the antenna device has absorbers at least above and below the receiving antenna.