JPH08338868A - Intermediate frequency stabilizing circuit for radar device - Google Patents

Abstract

PURPOSE: To provide IF (intermediate frequency) output satisfying high frequency stability required for a S3 (spectrum scattering) method and a pulse method. CONSTITUTION: A receiver 12 for a millimeter wave radar is provided with a PLL circuit 30 for stabilizing IF output in frequency. At the PLL circuit 30, the difference frequency signal between the local generation signal generated by a local gun oscillator 24 and the transmitting carrier wave supplied by a transmitting gun oscillator 14 is phase-compared with the reference signal generated by a TCXO(temperature compensated crystal oscillator) 32 with high stability, and based on the result, the local gun oscillator 24 is phase-locked. The oscillation output of the local gun oscillator 24 is used for frequency conversion of the reception input, so that the IF output of high frequency stability is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar system using a pulse system, SS (spread spectrum) system, etc.
In particular, it relates to an intermediate frequency stabilizing circuit for stabilizing the intermediate frequency.

[0002]

2. Description of the Related Art Conventionally, millimeter wave vehicle-mounted radar devices have been developed. The millimeter wave vehicle-mounted radar device transmits, for example, a millimeter wave signal in front of the vehicle, receives an echo from an object (target) existing in front of the vehicle, and based on the received echo, the distance and relative velocity to this target. Is a device for measuring.
Further, in a millimeter wave vehicle-mounted radar device, an FM-CW (frequency modulation-continuous wave) system is mainly used as a modulation system, but in recent years, it is based on a pulse system, an SS system, a two-frequency CW system or the like. Millimeter-wave vehicle-mounted radar devices have been developed.

[0003]

In the FM-CW method among these modulation methods, a frequency-modulated continuous wave is used as a transmission signal, and based on the beat frequencies of the transmission signal and the received echo. The above detection is performed. Therefore, when the FM-CW method is used, the frequency stability required for the carrier (here, the frequency-modulated continuous wave) is not so high. But,
In the SS system and the pulse system, a predetermined frequency stability is required for the carrier wave. Particularly, in the SS system, since it is necessary to demodulate the spread spectrum modulation applied to the carrier at the time of transmission, high frequency stability is required for the intermediate frequency (IF) signal obtained by frequency conversion at the time of reception. On the other hand, even if an oscillator that can be used in a band such as a millimeter wave, for example, a Gunn oscillator is free-run alone, it is not possible to obtain so high frequency stability. Therefore, conventionally, a frequency multiplication method or the like has been used.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the frequency of the IF signal output in a radar receiver can be stabilized by a simpler means so that frequency multiplication or the like can be performed. It is an object of the present invention to make it possible to satisfy the frequency stability required by the SS system and the pulse system without using the above means.

[0005]

In order to achieve such an object, an IF stabilizing circuit for a radar device according to the present invention comprises a reference oscillator for generating a reference signal of a predetermined frequency with a predetermined stability, A PLL for generating a control IF signal by mixing a transmission carrier wave input from a radar transmitter and a local oscillation signal input from a local oscillator, and phase-locking the local oscillator based on the phase comparison result of the control IF signal and a reference signal. And a circuit for transmitting a modulated carrier wave for transmission and receiving an echo thereof to mix the received input with the local oscillation signal to convert the received input into an IF signal. It is characterized in that the frequency difference of the local oscillation signal is stabilized by the phase lock with the stability according to the stability of the reference oscillator.

Further, the radar receiver according to the present invention comprises a local oscillator for generating a local oscillation signal and a mixer for mixing a reception input with the local oscillation signal, and transmits a modulated transmission carrier wave and receives an echo thereof. A radar receiver for converting a received input obtained by the above into an IF signal by the mixing is characterized by including an IF stabilizing circuit for a radar device according to the present invention.

The radar apparatus according to the present invention has a transmission oscillator for generating a transmission carrier wave and a modulator for generating a transmission output by modulating the transmission carrier wave. And a radar receiver according to the present invention.

[0008]

According to the present invention, the local oscillation signal input from the local oscillator is mixed with the transmission carrier wave input from the radar transmitter. As a result, a control IF signal having a difference frequency between the transmission carrier wave and the local oscillation signal is generated.
The control IF signal is phase-compared with a reference signal having a predetermined frequency and stability. Since the local oscillator is phase locked based on this result, the frequency of the local oscillation signal is always a signal having a predetermined frequency difference with respect to the carrier wave for transmission. More precisely, the frequency of the local oscillation signal is stabilized with respect to the frequency of the carrier wave for transmission with the stability according to the stability of the reference oscillator. Since the reception input of the radar device basically has the same frequency as the above-mentioned transmission carrier wave, the local oscillation signal thus obtained is converted into the IF signal of the reception input of the radar device. When used for the processing, the frequency of the IF signal obtained as a result of this frequency conversion is also stabilized according to the stability of the reference oscillator. In that case, means such as frequency multiplication is not necessary.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a millimeter-wave vehicle-mounted radar according to an embodiment of the present invention, in particular, its transceiver.
The transceiver shown in this figure is roughly equivalent to the transmitter 10
And a receiver 12.

The transmitter 10 has a transmitting Gunn oscillator 14 and a modulator 16. The transmission gun oscillator 14 generates a transmission carrier wave of a predetermined frequency belonging to the millimeter wave band,
This is supplied to the modulator 16. The modulator 16 modulates the transmission carrier wave supplied from the transmission Gunn oscillator 14 with a modulation input given from the outside, and supplies this to the subsequent stage as a transmission output. As shown in FIG. 2, an antenna 20 is connected to the subsequent stage of the transmitter 10 via an antenna duplexer 18. The antenna 20 wirelessly transmits the transmission output supplied from the transmitter 10. When this signal, that is, the transmission signal wirelessly transmitted is reflected by the target, the echo related to this reflection is received by the antenna 20.
The reception input obtained by the antenna 20 is input to the receiver 12 via the antenna duplexer 18.

As shown in FIG. 1, the receiver 12 has a millimeter wave mixer 22 and a local oscillator Gun oscillator 24. The local oscillator Gun oscillator 24 generates a local oscillation signal of a predetermined frequency, and the generated local oscillation signal is used for the directional coupler 2.
6 to the LO port of the millimeter wave mixer 22. The above-mentioned reception input is supplied to the RF port of the millimeter wave mixer 22, so that a signal obtained by mixing the reception input and the local oscillation signal from the IF port of the millimeter wave mixer 22,
That is, an IF signal obtained by down-converting the reception input with the local oscillation signal is obtained. This IF signal is band-limited by the BPF provided in the subsequent stage, that is, the IF filter 28, and then supplied to the circuit in the subsequent stage as an IF output.

A feature of the present invention is that the IF frequency is stabilized without using any means such as frequency multiplication by using the local oscillator Gun oscillator 24 and the PLL circuit. Therefore, in this embodiment, a PLL circuit 30 and a TCXO (temperature compensated crystal oscillator) 32 are provided inside the receiver 12. PLL circuit 3
0 has a local oscillator Gun oscillator 24, a directional coupler 26, and a millimeter wave mixer 34. Millimeter wave mixer 34
A local oscillation signal is input to the LO port and a transmission carrier wave is input to the RF port via the directional coupler 36. Therefore, a signal having a difference frequency between the local oscillation signal and the carrier wave for transmission appears at the IF port of the millimeter wave mixer 34. This signal, that is, the control IF signal, is band-limited by the BPF provided in the subsequent stage, that is, the IF filter 38, and then supplied to the frequency divider 40, and is frequency-divided at a predetermined frequency division ratio. The output of the frequency divider 40 is TCXO3
It is input to the phase comparator 42 together with the oscillation output of 2. The phase comparator 42 compares the phase of the control IF signal divided by the frequency divider 40 with the reference signal generated by the TCXO 32 and having extremely high stability. The result of the phase comparison by the phase comparator 42 is the gun oscillator 24 for local oscillation.
It is fed back to the local oscillator Gun oscillator 24 via an LPF for supplying a control voltage to the signal, that is, a loop filter 44. The local gun oscillator 24 is a VCO type, that is, an LPF
It has a function of oscillating at a frequency according to the result (control voltage) of the phase comparison supplied from the phase comparator 42 via 44. Therefore, the oscillation frequency of the local oscillator Gun oscillator 24 is
The phase is locked so that the difference frequency from the carrier wave for transmission is always constant (strictly, it is stabilized with the stability according to the stability of the TCXO 32).

Therefore, according to the present embodiment, the IF output of the receiver 12 is supplied to the TCXO 32 by supplying the thus-stabilized local oscillation signal to the millimeter wave mixer 22.
The frequency can be stabilized at a degree of stability corresponding to the degree of stability. At that time, since it is not necessary to use a means such as frequency multiplication and a Gunn oscillator having a relatively low stability may be used as an oscillator, by adding a relatively simple and inexpensive circuit, an SS system or a pulse system can be used. It is possible to satisfy the frequency stability required in the above.

[0015]

As described above, according to the present invention,
Since the frequency difference between the transmission carrier wave and the local oscillation signal is stabilized by the PLL circuit, for example, the high frequency stability required by the SS system or the pulse system can be achieved only by adding a relatively simple and inexpensive circuit configuration. Can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a transceiver according to an embodiment of the present invention.

FIG. 2 is a diagram showing a use environment of this embodiment.

[Explanation of symbols]

10 transmitter, 12 receiver, 14 transmission gun oscillator, 16 modulator, 22, 34 millimeter wave mixer, 24
Local oscillator Gun oscillator, 26, 36 Directional coupler, 30
PLL circuit, 32 TCXO, 40 frequency divider, 42 phase comparator, 44 loop filter.

Claims (3)

[Claims] 1. An intermediate frequency signal for control by mixing a reference oscillator for generating a reference signal of a predetermined frequency with a predetermined stability and a carrier wave for transmission input from a radar transmitter and a local oscillation signal input from a local oscillator. PL for phase-locking the local oscillator based on the phase comparison result of the control intermediate frequency signal and the reference signal.
An L circuit, which is used for transmitting the modulated carrier wave for transmission and receiving the echo thereof and the local oscillation signal for mixing the received input to convert the received input to an intermediate frequency signal. An intermediate frequency stabilizing circuit for a radar device, characterized in that the frequency difference between a carrier wave and a local oscillation signal is stabilized by the phase lock with a stability according to that of a reference oscillator. 2. A local oscillator for generating a local oscillation signal and a mixer for mixing the reception input with the local oscillation signal, the reception input obtained by transmitting a modulated transmission carrier wave and receiving an echo thereof. A radar receiver for converting into an intermediate frequency signal by means of the intermediate frequency stabilizing circuit for a radar device according to claim 1. 3. A radar transmitter having a transmission oscillator for generating a transmission carrier and a modulator for generating a transmission output by modulating the transmission carrier, and a radar transmitter for wirelessly transmitting the transmission output. A radar device comprising: a radar receiver.