JPH11261332A - Radar device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the degree of freedom on the array of a plurality of element antennas by installing a transmission line layer where a transmission line connecting a plane array antenna and a circuit part on a circuit layer is provided on an intermediate layer sandwiched by an antenna layer and the circuit layer. SOLUTION: A radar device 1 is constituted of an antenna layer 2 having a plane array antenna 20, a transmission line layer 3 where a transmission line is installed, a high frequency circuit layer 4 loading a high frequency circuit executing the signal processing of a high frequency signal and a signal processing circuit layer 5 loading a signal processing circuit executing a digital beam foaming processing on a digital outputted from the high frequency circuit. The transmission line layer 3 is provided between the antenna layer 2 and the high frequency circuit layer 4. The transmission line layer 3 is constituted of a waveguide connected to the micro strip line of the antenna layer 3 positioned above, the high frequency circuit layer 4 positioned below and a waveguide connected to the upper transmission line. The respective waveguides are connected so that line lengths become equal to the two waveguides through the transmission line 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar apparatus, and more particularly to a radar apparatus having a planar array antenna in which a plurality of element antennas are arranged on a plane.

[0002]

2. Description of the Related Art A planar array antenna in which a large number of patch antennas are arranged in a row direction and a column direction is disclosed in
There is a microwave antenna disclosed in JP-A-181537. In this microwave antenna, a feed line of a microstrip line on a substrate on which a patch antenna is arranged is devised for the purpose of high gain and high efficiency.

[0003]

On the other hand, the arrangement of the patch antennas, particularly the distance between the patch antennas, depends on the angle of the grating lobe with respect to the main beam, the beam width, and the like.
Since it greatly affects the antenna gain and the like, it is necessary to set it appropriately according to the application.

However, when the configuration of the feeder line is made special for the purpose of high gain and high efficiency as in the above-mentioned prior art, it is difficult to arrange the patch antennas at desired intervals, and the combined beam However, there has been a problem that it is difficult to obtain a sufficient gain, or it is difficult to keep the grating lobe away from the main beam by narrowing the interval between the patch antennas.

[0005]

The radar apparatus according to the present invention comprises:
In order to solve such a problem, an antenna layer provided with a planar array antenna, a circuit layer on which at least a part of a circuit unit of a radar device is mounted, and an intermediate layer sandwiched between the antenna layer and the circuit layer And a transmission line layer provided with a transmission line connecting the planar array antenna and a circuit portion on the circuit layer.

[0006] According to this radar device, since the transmission line layer is provided between the antenna layer and the circuit layer, a part of the transmission line between the antenna and the circuit section is formed on the transmission line layer on the transmission line layer. And transmission lines on the antenna layer can be minimized. This increases the degree of freedom in the arrangement of a plurality of element antennas constituting the planar array antenna.

[0007] Further, by using a triplate line or a suspended line having much smaller power loss than a microstrip line as the transmission line on the transmission line layer, the entire transmission line from the antenna to the circuit section is supplied. Loss can be reduced.

[0008]

FIG. 1 is a perspective view showing an embodiment of a radar apparatus according to the present invention, and FIG. 2 is a block diagram showing a circuit configuration thereof. The radar apparatus 1 includes an antenna layer 2 having a planar array antenna 20, a transmission line layer 3 provided with a transmission line 30, a high frequency circuit layer 4 having a high frequency circuit 40 for performing signal processing of a high frequency signal of several tens of GHz, and A signal processing circuit layer 5 having a signal processing circuit 50 for performing digital beam forming processing or the like on a digital signal output from the high frequency circuit 40 is provided.

The radar apparatus 1 has a laminated structure having a transmission line layer 3 between an antenna layer 2 and a high-frequency circuit layer 4 as shown in FIG. Before describing this, the overall configuration and operation of the radar apparatus 1 will be described with reference to FIG.

This radar apparatus 1 is an FM-CW using a transmission signal obtained by applying frequency modulation (FM) to a continuous wave (CW).
This is a radar device and a DBF radar device that performs digital beam forming processing at a receiving antenna. The radar device 1 is a so-called on-vehicle radar device mounted on an automobile, and detects a distance to a vehicle traveling ahead and a relative speed thereof. The detection result of the radar device is used for control information of vehicle running and the like. Microwaves are used for transmission radio waves.

In a conventional general DBF radar apparatus, an RF amplifier and a mixer are provided for each element antenna. In this radar apparatus, analog switches such as an RF amplifier and a mixer are provided by using a changeover switch. The configuration is such that one device is provided as a whole.

The high frequency circuit section 40 has a center frequency f0.
The transmission unit includes a voltage-controlled oscillator 11 (for example, 76 GHz), a buffer amplifier 12, and an RF amplifier 14. The oscillator 11 is a signal obtained by applying a triangular wave modulation having a frequency modulation width ΔF to a carrier having a frequency f0 by a control voltage output from a DC power supply for modulation not shown, that is, a modulated wave having a frequency f0 ± ΔF / 2. (Transmission signal). The modulated wave is amplified by the buffer amplifier 12 and radiated from the transmission antenna 60 as an electromagnetic wave.
A part of the transmission signal is amplified by the RF amplifier 14 and output to the reception unit in the high-frequency circuit unit 40 as a local signal for reception detection.

In this embodiment, the transmitting antenna 6
1 is separate from the receiving planar array antenna 20 and is not shown in FIG. 1, but may be formed by a patch antenna or the like on the same substrate as the planar array antenna 20.

The receiving planar array antenna 20 includes a first channel (CH1), a second channel (CH2), and a third channel (CH2).
It is composed of three channels including a channel (CH3). Here, an example of three channels is shown for the sake of simplicity. However, in consideration of detection capability, size, and the like, an on-vehicle radar device preferably has about ten channels.

The receiving section of the high-frequency circuit section 40 includes an RF amplifier 41, a mixer 42, an amplifier 43, a filter 44, an A / D
A converter 45, an oscillator 46 for generating a switching signal, and a switch 47 are provided.

The changeover switch 47 has three input terminals and one
, And a transmission line connected to each channel of the array antenna 20 is connected to each input terminal. The output terminal is connected to any one of the input terminals, and is switched by a switching signal (clock signal).
The connection is switched periodically. Connection switching is performed electrically on a circuit.

The signal output from the output terminal of the changeover switch 47, that is, the signal received on any channel of the array antenna 2 is amplified by the RF amplifier 41, and the mixer 42 extracts one of the transmission signals from the RF amplifier 14. Mixed with the department. The received signal is down-converted by this mixing, and a beat signal which is a difference signal between the transmitted signal and the received signal is generated.

In the triangular wave modulation FM-CW method, the beat frequency when the relative speed is zero is fr, the Doppler frequency based on the relative speed is fd, the beat frequency in the section where the frequency increases (up section) is fb1, and the frequency decreases. Assuming that the beat frequency of the section (down section) is fb2, fb1 = fr-fd (1) fb2 = fr + fd (2) holds.

Therefore, if the beat frequencies fb1 and fb2 in the up and down sections of the modulation cycle are separately measured, fr and fd can be obtained from the following equations (3) and (4).

Fr = (fb1 + fb2) / 2 (3) fd = (fb2-fb1) / 2 (4) If fr and fd are obtained, the distance R and the velocity V of the target are calculated by the following (5) ( It can be obtained by equation (6).

R = (C / (4 · ΔF · fm)) · fr (5) V = (C / (2 · f0)) · fd (6) where C is the speed of light, and fm is FM modulation frequency.

The beat signal is input to an A / D converter 45 via an amplifier 43 and a low-pass filter 44, and is output as a digital signal at the timing of an output signal of an oscillator 46, that is, a clock signal for switching connection by the changeover switch 3. Is converted to

The digital signal processing unit 50 performs digital beam forming (DBF) on the digital beat signal from the A / D converter 45. That is,
The digital signal processing unit 50 performs phase and amplitude conversion of the digital reception signal of each channel according to a certain rule to synthesize all the channels. Thereby, the directivity pattern of the receiving antenna 20 can be formed in an arbitrary direction and an arbitrary shape. A major feature of the DBF is that once signals of all reception channels are captured as digital signals, beam combining can be performed in any direction based on the signals. What you can do.

The overall configuration and operation of the radar device 1 have been described above. Next, the structural features will be described. FIG.
4 is a plan view showing the antenna layer 2, FIG. 4 is a plan view showing the transmission line layer 3, and FIG. 5 is a plan view showing the high-frequency circuit layer 4.

The antenna layer 2 includes a planar array antenna 20 in which a large number of patch antennas 21 as element antennas are arranged on a substrate in a matrix. Each channel is 1
It is composed of six patch antennas 21 and two waveguides 23. Eight patch antennas 21 are connected to one waveguide 23 by microstrip lines 22, respectively, and the line lengths from the waveguide 23 to each patch antenna 21 are adjusted to be substantially equal. . The waveguide 23 is a transmission line for connecting the transmission line 30 on the transmission line layer 3 and the microstrip line 22 on the antenna layer 2, and penetrates through the substrate of the antenna layer 2 to form the transmission line layer 3. It has a structure that reaches the surface.

As shown in FIG. 4, the transmission line layer 3 includes six waveguides 23 connected to the microstrip line 22 of the antenna layer 2 located above and the high frequency circuit layer 4 located below. And three waveguides 31 connected to the transmission line. Each of the waveguides 31 is connected to the two waveguides 23 via the transmission line 30 so as to have the same line length as each other.

The transmission line 30 is desirably formed of a triplate line or a suspended line having a lower feed loss than the microstrip line. Incidentally, when a microstrip line was used for the transmission line 30, the power supply loss was 57 dB / m, but when a triplate line was used, it was 7 dB / m, and when a suspended line was used, it was 3 dB. / M.

FIG. 6 is a sectional view showing the structure of the suspended line. Two planar conductor plates 61 and 62 are arranged facing each other, and a dielectric film 63 is supported by a conductor wall 65 therebetween. On the dielectric film 63, a conductor strip line 64 is formed. The electromagnetic wave propagates between the stripline 64 and the plane conductors 61, 62 and the conductor wall 65.

The triplate line has two plane conductor plates like the suspended line, and a conductor strip line is provided between the two plane conductor plates. A dielectric layer is interposed between the strip line and the two plane conductor plates, and the electromagnetic wave propagates between the strip line and the upper and lower plane conductor plates.

As shown in FIG. 5, the high-frequency circuit layer 4 has a high-frequency circuit section 40 mounted thereon. Three waveguides 31 extending from the transmission line layer 3 are connected to three input terminals of the high-frequency circuit section 40, respectively. I have. The three input terminals of the high-frequency circuit section 40 correspond to the input terminals of the changeover switch 47 shown in FIG.

The output terminal of the high-frequency circuit section 40 is connected to a digital signal processing section provided in a further lower layer, but the connection structure is not shown.

In the radar device of the present embodiment thus configured, the electromagnetic wave that has reached the patch antenna 21 reaches the waveguide 23 via the microstrip line 22 on the antenna layer 2 and from there the transmission line layer. Transmission line 3 on 3
Then, the light reaches the waveguide 31 through 0, and further propagates to the high-frequency circuit section 40 on the high-frequency circuit layer 4.

According to the radar device of this embodiment, since the transmission line layer 4 is provided between the antenna layer 2 and the high-frequency circuit layer 4, the transmission line on the antenna layer 2 can be shortened. This makes it possible to omit transmission lines that have been routed between channels on the surface of the antenna layer 2 and to reduce the distance between channels. As a result, the gain of the entire antenna synthesized by the signal processing is improved, and when the distance between the channels is reduced, the direction in which the grating lobe appears, that is, the angle with respect to the main beam, is increased, and the detectable range of the radar device is expanded.

Further, since it is no longer necessary to route the transmission line between the channels on the antenna layer 2, a space for arranging a conductive wall for preventing inter-channel interference between channels on the surface of the antenna layer 2 is secured. It became easy to do.

Further, since only the transmission line is formed on the transmission line layer 4 except for the waveguides for connecting the upper and lower layers, a suspended line or a triplate line having a small feed loss should be used as the transmission line. Can be. Incidentally, since the suspended line and the triplate line require two flat conductor plates facing each other, it is extremely difficult to form the patch antenna on the surface of the antenna layer formed on the surface.

In this embodiment, since the single mixer 42 performs high-frequency signal processing by using the changeover switch 47, it is necessary to collect signals of each channel at one place, that is, the changeover switch 47. For this reason, the transmission line becomes longer as compared with the case where a high-frequency circuit is provided for each channel. However, since a transmission line with a small feeding loss can be used as the transmission line on the transmission line layer 4, the overall transmission line can be used. Feeding loss can be reduced.

In this embodiment, the digital signal processing unit 5
Although 0 and the high-frequency circuit section 40 are formed on the signal processing circuit layer 5 and the high-frequency circuit layer 4, respectively, they may be formed on the same layer.

[0038]

As described above, according to the radar apparatus of the present invention, since the number of transmission lines on the antenna layer can be minimized, the arrangement of a plurality of element antennas constituting the planar array antenna is free. The degree increases. Therefore, for example, when a multi-channel antenna is formed on a planar array antenna, the distance between channels can be shortened, the antenna gain can be improved by signal processing, and the main gain of the grating lobe can be improved. The angle to the beam can be widened.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a radar device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the circuit configuration.

FIG. 3 is a plan view showing an antenna layer 2.

FIG. 4 is a plan view showing a transmission line layer 3;

FIG. 5 is a plan view showing the high-frequency circuit layer 4;

FIG. 6 is a sectional view showing a configuration of a suspended line.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Radar apparatus, 2 ... Antenna layer, 3 ... Transmission line layer, 4
... High frequency circuit layer, 5 ... Signal processing circuit layer, 21 ... Patch antenna, 22 ... Microstrip line, 23, 31 ...
Waveguide, 30 transmission line, 40 high frequency circuit section, 50
Signal processing unit.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // G01S 13/34 G01S 13/34

Claims (2)

[Claims] 1. A radar device provided with a planar array antenna in which a plurality of element antennas are arranged on a plane, wherein an antenna layer provided with the planar array antenna and at least a part of a circuit unit of the radar device are mounted. Circuit layer, a transmission line layer provided with a transmission line that is an intermediate layer sandwiched between the antenna layer and the circuit layer and that connects the planar array antenna and the circuit unit on the circuit layer. A radar device comprising: 2. The radar apparatus according to claim 1, wherein said transmission line is formed of a triplate line or a suspended line.