JPH11258340A - Radar transmitter/receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a plurality of targets at near and far distances with radar in a radar transmitter/receiver used for preventing the collision of an automobile. SOLUTION: Normally, an FM pulse wave that is oscillated by an SOM (frequency mixer) 2 is transmitted by an antenna 1, a reflection wave from an object is received by the antenna 1 and is taken out as an intermediate frequency signal by the SOM 2, and signal processing is made by a signal processing part 6 for FM pulses, thus detecting the object at a far distance. When a DSP 7 judges that there is a close target, it outputs a switching signal and switches the oscillation of the SOM 2 to an FM-CM wave, transmits the FM-CW wave from the antenna 1, receives a reflection signal from the target by the antenna 1, and takes out a beat signal by the SOM 2. Then, the signal is processed by the signal-processing part 9 for FM-CW to detect the object at a close distance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar transceiver used, for example, for preventing collision of an automobile, and more particularly to a radar type switching type radar transceiver.

[0002]

2. Description of the Related Art Conventionally, pulse radars and FM-CW radars have been used as conventional radars, but these radar systems are independent of each other.

A pulse radar continuously emits radio waves divided into pulse shapes. FIG. 2 shows a transmission pulse and a reflected wave from a target. In the figure, Pw indicates the pulse width of the transmission pulse, and the time until the transmission pulse hits the target and returns is T, the light speed (3.0).
(× 10 ⁸ m / s) as C, the distance R to the target is calculated from the equation R = C · T / 2.

[0004] The speed of the target can be determined by reading the fluctuation of the carrier component of the reflected wave returning from the target due to the Doppler effect.

On the other hand, the FM-CW radar is a continuous wave (CW) radar that transmits a FM-modulated continuous wave and simultaneously receives a reflected wave. For example, the FM-CW radar is a radar technology (pp287-289) published by the Institute of Electronics, Information and Communication Engineers. It is shown. FIGS. 3 and 4 show the relationship between signal frequency and time in the FM-CW radar.

If the above-mentioned FM is performed by repeating triangular waves, the relationship between the frequency and the time of the transmission signal is as shown by the solid line in FIG. The relationship between the frequency of the reflected signal and the time is as shown by the broken line in FIG. Therefore, the beat frequencies of the transmission signal and the reflection signal are as shown in FIG. 3B, and the distance to the target can be determined by measuring this.

If the repetition frequency of the FM is fm and the frequency deviation width of the FM is Δf, the beat frequency fr of the reflected signal from the target at the distance R is fr = (4R · fm · Δf) /
It is represented by the formula of C.

Next, when the target is moving,
Due to the Topler effect, the relationship between the frequency of the transmission signal and the frequency of the reception signal versus time is as shown in FIG. That is, the beat signal frequency fb is obtained by superimposing the topler frequency fd on the beat signal frequency fr in the case of a fixed target as shown in FIG. 4B, and its direction alternates between positive and negative in each modulation cycle. Fb (negative) = fr−fd,
fd (positive) = fr + fd

Thus, for each half cycle of modulation, f
If b (positive) and fb (negative) are measured separately, fr and f
d, that is, the distance and the velocity of the target can be separately obtained.

[0010]

However, the above-mentioned conventional radar transceivers have the following problems because they have independent radar systems.

First, in a pulse radar, it is difficult to detect a short-range target. This is because the short-range performance of the pulse radar is determined by the pulse width, and the shortest detection distance d is C · T / 2 as described above.
It is represented by

Next, in the case of an FM-CW radar, it is difficult to detect a target having a relative speed of zero. This is because the detection is performed based on the frequency difference between the transmission wave and the reception wave. Also, it is difficult to detect a plurality of targets. This is because a corresponding frequency cannot be specified from among a large number of frequencies detected for a large number of targets.

The present invention has been made in view of the above-mentioned problems, and can switch between the FM pulse system and the FM-CW system with the same front end, and can be used for a plurality of short-range and long-range targets. The purpose is to provide a compatible radar transceiver.

[0014]

A radar transceiver according to the present invention generates a transmission frequency for transmitting a frequency-modulated pulse wave and a frequency-modulated continuous wave, respectively. And a frequency control circuit for switching the oscillation frequency of the frequency mixer with a predetermined switching signal. The frequency mixer processes the mixed signal with the frequency mixer to detect radar. Is performed.

[0015]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a transmitting / receiving antenna, and 2 denotes a frequency mixer SOM (Self Oscillat).
An ion mixer) generates a transmission frequency for transmitting a pulse wave to which FM (frequency modulation) has been applied and a CW (continuous wave) to which FM has been applied, respectively, from the antenna 1, and has a reception frequency and a reception local portion. Mix oscillation frequency.

3 is a low-pass filter, 4 is a switch for switching between FM pulse and FM-CW by a radar-type switching signal, 5 is a low-noise intermediate frequency amplifier, 6 is a signal processing unit for FM pulse, and the processing result is as follows. The data is input to a DSP (Digital Signal Processor) 7 and further transmitted to a display / warning system. 8 is a video amplifier, 9 is FM-
The processing result is output to the DSP 7 in the CW signal processing unit.

Numeral 10 denotes an SOM oscillation frequency control circuit which controls the oscillation frequency of SOM 2 by the switching signal. 1
Reference numeral 1 denotes a timing circuit that outputs a timing signal to the DSP 7 and the SOM oscillation frequency control circuit 10, and reference numeral 12 denotes a phase synchronization reference oscillator.

The radar transmitter / receiver having the above configuration can be switched between the FM pulse radar and the FM-CW radar by one radar front end. As described above, the pulse radar and the FM-CW radar each have advantages and disadvantages, and it is useful to use a radar system in practical use to compensate for those disadvantages, and the present embodiment can deal with that. It has become.

That is, for example, when an automobile is running, the FM is usually used for detecting an obstacle and monitoring the movement of another running vehicle.
Used as a pulse radar. The operation of the radar front end unit at this time is as follows: the FM pulse wave oscillated by the SOM 2 is transmitted from the antenna 1, the reflected wave that has returned to hit the target is received by the antenna 1, and the intermediate frequency Take it out as a signal. Then, after amplifying the signal of the intermediate frequency, the signal processing unit 6 for FM pulse performs predetermined signal processing, and sends the signal to the DSP 7 for radar detection.

However, when the DSP 7 determines that a problem such as a collision occurs in running of the car due to a short-distance target in the above state, the DSP 7 outputs the above-mentioned switching signal, and thereby the FM-CW radar system is used. Is switched. At this time, the operation of the radar front end unit is as follows: the FM-CW wave oscillated by the SOM 2 is transmitted from the antenna 1, and the reflected wave that has returned to hit the target is received by the antenna 1.
OM2 detects a beat. Then, the beat signal is amplified, subjected to predetermined processing by the FM-CW signal processing section 9, and sent to the DSP 7 to perform radar detection.

When the short-range target disappears while the FM-CW radar is being used, the FM
Switch to pulse radar and return to normal use.

As described above, the same front end is used for FM.
By switching between the pulse radar and the FM-CW radar, a plurality of short-range and long-range targets can be detected by radar, and can be used for both the short-range sensor and the long-range sensor. When it is determined that a collision has occurred based on the signal from the FM-CW signal processing unit 9, a signal for operating the airbag can be output from the DSP 7, and the DSP 7 can also be used as an airbag sensor.

[0023]

As described above, according to the present invention, it is possible to switch between the FM pulse system and the FM-CW system with the same front end, and to cope with a plurality of short-range and long-range targets. effective.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram showing transmitted and received waves in a pulse radar.

FIG. 3 is an explanatory diagram showing a relationship between frequency and time in the FM-CW radar.

FIG. 4 is an explanatory diagram showing a relationship between frequency and time in the FM-CW radar.

[Explanation of symbols]

 Reference Signs List 1 antenna 2 SOM (frequency mixer) 3 low-pass filter 4 changeover switch 5 low noise intermediate frequency amplifier 6 signal processing unit for FM pulse 7 DSP 8 video amplifier 9 signal processing unit for FM-CW 10 SOM oscillation frequency control circuit 11 timing circuit 12. Oscillator for phase synchronization reference

Claims (1)

[Claims] A frequency mixer for generating respective transmission frequencies for transmitting a frequency-modulated pulse wave and a frequency-modulated continuous wave, and mixing a reception frequency and a reception local oscillation frequency; A frequency control circuit that switches an oscillation frequency of the frequency mixer by a predetermined switching signal, and processes a signal mixed by the frequency mixer to perform radar detection.