JPH10150317A - Antenna system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve distance detection performance without degrading angle detection accuracy by placing a shield plate that prevents a sneak path of a radio wave sent from a transmission antenna to a reception antenna tilted toward the transmission antenna. SOLUTION: A shield plate 16 consisting of a truncated quadrangular pyramid is fitted to a rear side of a quadrangular throughhole of an antenna mount base 15. The shield plate 16 is inversely tapered to a horn 11a of a horn antenna 11 and forms a frame while its tip is tilted inward and is mounted on the antenna mount base 15 by fixing its base to a ridge of the throughhole from its rear side. In the, antenna system where the shield plate 16 is provided around the transmission horn antenna 11, a diffracting angle of a radio wave emitted from the horn 11a at a tip edge of the shield plate 16 for the radio wave is decreased to reduce leakage of the radio wave onto a plane antenna through diffraction. This antenna system acts like a radar by reducing the coupling between transmission and reception radio waves.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna device in which the coupling between a transmitting antenna and a receiving antenna is reduced to improve the distance detecting performance without reducing the azimuth detecting ability.

[0002]

2. Description of the Related Art A radar device mounted on an automobile for detecting a moving object or an obstacle on a road, and for detecting an azimuth and a distance of a preceding vehicle, and furthermore, a relative speed is generally an object to be detected by the object. Since the area is in the range of about 50 to 200 m in front of the own vehicle, radio waves in the millimeter wave band having a wavelength of 30 to 300 GHz are exclusively used. As an antenna device used for this type of radar device, a mechanism for mechanically scanning a radio wave beam is complicated, and an electronic device for electrically scanning is extremely expensive, In many cases, a multi-beam system exclusively using a plurality of antennas is employed.

A multi-beam type antenna device is
For example, as shown in FIG. 3, one transmitting antenna for obtaining a transmitting beam T having a beam width covering the scanning target range, and receiving beams in a plurality of azimuths having a beam width set according to the azimuth detection accuracy in the scanning target range. And a plurality of receiving antennas for obtaining R. For example, as shown in FIG. 3, three reception antennas are used so as to obtain reception beams R1, R2, and R3 obtained by dividing the transmission area of the transmission beam T into three in the horizontal direction. Incidentally, a horn antenna or a planar antenna is exclusively used as a transmitting antenna because a wide-angle beam covering the scanning target range is required. As a receiving antenna, a planar antenna is often used because it has small side lobes and beam forming is relatively easy.

FIG. 4 shows a schematic configuration of an antenna device using a horn antenna 1 for transmission and three planar antennas 2, 3, and 4 for reception. As described above, in the antenna device in which the transmission antenna and the reception antenna are formed separately, coupling between transmission and reception between the transmission antenna and the reception antenna, that is, the wraparound of the radio wave becomes a serious problem. By the way, in order to prevent the coupling between transmission and reception, it is sufficient to sufficiently separate the transmission antenna and the reception antenna, but there is a problem that the antenna size increases. In particular, in the above-described radar device for mounting on a vehicle, since the antenna device is generally mounted on the front grill of the vehicle, the antenna dimensions are naturally limited. For this reason, in the radar device shown in FIG. 4, a shielding plate 5 for preventing coupling between transmission and reception is provided between the horn antenna 1 and the planar antennas 2, 3, and 4.

[0005]

The shielding plate 5
In order to enhance the effect of preventing the coupling between transmission and reception due to the above, if the shielding plate 5 provided vertically to the antenna opening surface is extended high in front of the antenna opening surface, the pattern of the transmission beam T is affected by the shielding plate 5. There is a problem that the angle detection (orientation detection accuracy) is adversely affected. In addition, there is a problem that the depth dimension of the antenna device increases due to the extension of the shielding plate 5. Therefore, if priority is given to the angle detection accuracy and the antenna size, the removal of the coupling between the transmission and reception by the shielding plate 5 becomes insufficient, resulting in a problem that the distance detection performance is reduced.

The present invention has been made in view of such circumstances, and has as its object to reduce the coupling between transmission and reception without increasing the size of the antenna, and thereby to reduce the distance without sacrificing the angle detection accuracy. An object of the present invention is to provide an antenna device with improved detection performance.

[0007]

To achieve the above object, an antenna device according to the present invention comprises a transmitting antenna for transmitting a radio wave, and a receiving antenna for receiving a reflected wave of the radio wave by an object. A shielding plate provided between the transmitting antenna and the receiving antenna to prevent a radio wave transmitted from the transmitting antenna from sneaking into the receiving antenna is inclined toward the transmitting antenna.

[0008] In particular, the shield plate is provided so as to surround the opening end of the horn antenna constituting the transmitting antenna and to taper in a direction opposite to that of the horn of the horn antenna. A radio wave absorber is provided behind the antenna opening surface. That is, by providing the shielding plate at an angle to the transmitting antenna side, the amount of radio waves radiated from the opening surface of the transmitting antenna and diffracted at the shielding plate edge to the receiving antenna side can be reduced with respect to the antenna opening surface. And reduce unnecessary radio waves (reflected waves) with the radio wave absorber provided behind the antenna aperture, thereby changing the antenna dimensions and improving the azimuth detection capability. It is characterized in that the amount of coupling between antenna transmission and reception is reduced without lowering, thereby improving the distance detection performance.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the antenna device according to the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing a schematic configuration of the antenna device, and FIG. 2 is a cross-sectional view showing a configuration of the transmission antenna unit in FIG. This antenna device has a spread spectrum (SS; s) in a millimeter wave band.
pread specrrum) radar, for example, one horn antenna 11 as a transmitting antenna,
Three planar antennas 12, 13, 14 as receiving antennas
It has. The horn antenna 11 is, for example, a pyramidal horn having a horn (opening surface) of about 20 mm in length and about 10 mm in width. Planar antennas 11, 12, 13, 14
Has an outer dimension of, for example, about 53 mm long and about 77 mm wide,
It consists of a planar array antenna with different beam directions. And these antennas 11, 12, 13, 14
Are mounted on an antenna fixing body 15 having a length of 145 mm, a width of 180 mm, and a thickness of 3 mm, for example, so as to be located about 10 mm inward from the periphery thereof and have the same antenna surface.

However, around the horn antenna 11,
A truncated quadrangular pyramid-shaped shielding plate 16 surrounding the open end (opening surface) of the horn antenna 11 and inclined to the open end side of the horn antenna 11 is provided. The shielding plate 16 is made of a metal plate protruding from the surface of the antenna fixing body 15 by about 10 mm in length, and forms a taper in a direction opposite to the horn of the horn antenna 11 so as to surround the opening end of the horn antenna 11. Provided. The front end of the shielding plate 16 is positioned so as to be substantially flush with the front end surface (open end) of the horn antenna 11.

The configuration of the transmitting antenna section including the horn antenna 11 and the shielding plate 16 provided therearound will be described in more detail with reference to FIG. 11), a rectangular through hole 15a is formed. Horn antenna 11 having quadrangular pyramid horn 11a
Are positioned at the center of the through hole 15a, and the horn tip (antenna opening surface) projects from the surface of the antenna fixing body 15 by a predetermined amount.
13 and 14 are provided so as to be substantially flush with the antenna aperture surfaces.

Specifically, the horn antenna 11 is attached to the antenna fixing body 15 by fixing the flange 11b of the horn base to the antenna support 21 having legs fixed to the back surface of the antenna fixing body 15. . The horn antenna 11 is provided on the leg of the antenna support 21.
A stay 22 is provided on the back side of the horn antenna 11, and a radio wave absorber 23 is attached so as to cover the back side of the antenna opening surface of the horn antenna 11 using the stay 22.

On the other hand, a shielding plate 16 made of a truncated quadrangular pyramid frame is attached to the rectangular through hole 15a of the antenna fixing body 15 from the back side. This shielding plate 1
Reference numeral 6 designates a frame having a tapered direction opposite to that of the horn 11a of the horn antenna 11 and having a tip inclined inward.
It is attached to the antenna fixed body 15 by being fixed from the back side to the edge of a. In this state, the distal end of the shielding plate 16 surrounds the distal end of the horn 11a and is positioned substantially on the same plane as the distal end of the horn 11a.

In FIG. 1, reference numeral 17 denotes a waveguide connected to the flange 11b of the horn antenna 11. Further, the antenna support 21 and the stay 22 are realized as a two-part structure in which, for example, the horn antenna 11 is sandwiched from its side. These connections are made by screwing or the like. Thus, according to the antenna device having the structure in which the shielding plate 16 is provided around the transmitting horn antenna 11 as described above, since the shielding plate 16 itself is inclined toward the horn 11a, the radio wave radiated from the horn 11a Shield plate 16
, The diffraction angle at the leading edge can be reduced, and the leakage of radio waves to the planar antennas 12, 13, and 14 due to diffraction can be reduced accordingly. By the way, when the shielding plate is provided perpendicular to the opening surface of the horn antenna 11, the isolation from the planar antennas 12, 13, and 14 for reception can be secured at most only about 75 to 80 dB. An isolation of about 90 dB could be secured.

If the coupling between transmission and reception is -90 dB or more, the received signal is saturated in the IF circuit, making it almost impossible to amplify the reflected wave from the original object.
In this regard, if the transmission power itself from the horn antenna 11 is reduced, the absolute value of the coupling amount between transmission and reception is reduced.
Although the saturation in the F-circuit is eliminated, the intensity itself of the reflected wave by the object naturally decreases, so that the maximum detection distance as a radar decreases. In this regard, according to the antenna apparatus having the above-described configuration, the coupling amount between transmission and reception can be secured as much as -90 dB, so that the function as a radar can be exhibited without reducing the maximum detection distance.

Further, since the radio wave absorber 23 is provided on the back side of the horn antenna 11, unnecessary radio waves wrapping around the back side of the horn antenna 11 can be efficiently absorbed and removed. Accordingly, also in this regard, undesired coupling between transmission and reception can be prevented, and deterioration of the azimuth detection performance of the planar antennas 12, 13, and 14 for reception can be prevented.

Therefore, according to the antenna device having the above-described structure, the coupling amount between transmission and reception can be reduced without increasing the size of the antenna, so that the distance detection accuracy can be sufficiently improved. A high-performance antenna device suitable for a radar device can be realized compactly. Note that the present invention is not limited to the above-described embodiment. For example, the number of receiving antennas incorporated in the antenna device and the arrangement structure of the transmitting horn antenna 11 may be determined according to specifications. Shield plate 1
6 can be provided only between the horn antenna 11 and the receiving antenna without being provided. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0018]

As described above, according to the present invention, a shielding plate provided between a transmitting antenna for transmitting a radio wave and a receiving antenna for receiving a reflected wave of the radio wave by an object is provided on the transmitting antenna side. So that the amount of radio wave radiated from the aperture of the transmitting antenna and diffracted at the edge of the shielding plate to the receiving antenna is smaller than that in the case where the shielding plate is provided perpendicular to the antenna opening surface. It can be significantly reduced. Therefore, it is possible to reduce the amount of coupling between the transmitting and receiving antennas without changing the antenna dimensions and without lowering the azimuth detecting ability, thereby improving the distance detecting performance. It works.

[Brief description of the drawings]

FIG. 1 is a plan view showing a schematic configuration of an antenna device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a transmission antenna unit in the antenna device shown in FIG.

FIG. 3 is a diagram showing a relationship between a transmission beam and a reception beam in a multi-beam antenna.

FIG. 4 is a diagram showing a general structure of a conventional antenna device.

[Explanation of symbols]

 11 Horn Antenna (Transmit Antenna) 11a Horn 11b Flange 12,13,14 Planar Antenna (Receive Antenna) 15 Antenna Fixed Body 16 Shielding Plate 21 Antenna Support 22 Stay 23 Radio Wave Absorber

Claims (3)

[Claims] 1. An antenna device comprising: 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 is disposed between the transmitting antenna and the receiving antenna. An antenna device, wherein a shielding plate for preventing a transmitted radio wave from wrapping around to the receiving antenna is provided to be inclined toward the transmitting antenna. 2. The horn antenna according to claim 1, wherein the transmitting antenna comprises a horn antenna, and the shield plate surrounds an open end of the horn antenna and is provided with a taper opposite to the horn of the horn antenna. 2. The antenna device according to 1. 3. The antenna device according to claim 2, wherein the horn antenna includes a radio wave absorber on a back surface thereof.