JPS63275976A - Radar equipment - Google Patents

Abstract

PURPOSE:To perform highly accurate measurement, by transmitting an upper side band signal, in which increase is repeated at a constant period, and a lower side band signal, in which decrease is repeated, at the same time to an object as a transmitting waves, and obtaining the range and the speed of the object based on the frequency difference between each signal and the signal, which is reflected from the object. CONSTITUTION:A reference frequency f0 is oscillated and the oscillated reference signal S0 is sent from a local oscillator 1. The signal S0 undergoes frequency modulation with a modulating wave S1. Increase is repeated at a constant period in the region higher than the frequency f0 in an upper side band signal S2. Decrease is repeated at a constant period in a lower side band signal S3. The signals S2 and S3 are generated in a modulator 2. The signals S2 and S3 are transmitted to an object from a transmitting antenna 3. Reflected waves S'2 and S'3 from the object are received with a receiving antenna 4. The difference between the reflected upper side band signal S'2 and the upper side band signal S2 and the difference between the reflected lower side band signal S'3 and the lower side band signal S3 are detected. The range and the speed of the object can be computed based on the frequency differences.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a radar device, and particularly to an FM-CW radar device that detects the distance and speed of a target object.

[Prior Art] An FM-CW radar device emits a frequency-modulated continuous wave toward a target, and accurately determines the distance and speed of the target based on the reflected wave reflected from the target and the beat signal of the continuous wave. In recent years, attempts have been made to install it on vehicles and use it for forward monitoring of auto drive devices (for example, 5A
NE82-36, SAE 776267>.

The above-mentioned radar device usually obtains a transmission wave whose frequency repeatedly rises and falls at a constant rate through triangular wave modulation, and fires it at the target to generate a beat signal in the frequency rising part and a beat signal in the frequency falling part. Beat signals are detected and the distance and speed are calculated from these beat signals.

[Pressure point to be solved by the invention] By the way, in the conventional radar device described above, since both beat signals are obtained in the first half and the second half of the modulation period, there is a time lag of half a period, and the object cannot be detected during this period. There was a problem in that measurement errors occurred when the target was moving.

In addition, it is necessary to match the rate of increase and decrease in frequency with high precision, but this requires a complicated circuit to correct the distortion of the voltage-frequency characteristic of the voltage-controlled oscillator in the modulated wave oscillator. (Sho 60-93977)
.

The present invention aims to solve this problem, and it is possible to obtain beat signals of the frequency rising part and the falling part at the same time without any time lag, thereby enabling highly accurate measurement of high-speed targets. It is an object of the present invention to provide a radar device that does not require a complicated correction circuit.

[Means for Solving the Problems] The configuration of the present invention is explained with reference to FIG. 1. It is a radar system! 1 includes an oscillation means 1 that generates a reference oscillation signal that oscillates at a reference frequency, and an upper sideband signal that frequency-modulates the reference oscillation signal with the same modulation wave and whose frequency repeats rising at a constant cycle in a region higher than the reference frequency. , a modulating means 2 for simultaneously emitting a lower sideband signal whose frequency repeats a fall at the constant period in a region lower than the reference frequency, and transmitting each of the upper sideband and lower sideband signals toward the target. A transmitting antenna 3 receives the upper sideband reflected signal and the lower sideband reflected signal reflected from the target object, and detects the frequency difference between the upper sideband signal and the upper sideband reflected signal. It also includes a signal processing means 5 for detecting the frequency difference between the lower sideband signal and the lower sideband reflected signal and calculating the distance and speed of the target object from these frequency differences.

[Operations and Effects] In the radar device of the present invention, the reference oscillation signal is modulated with the same modulation wave to generate an upper sideband signal that repeatedly rises at a constant cycle and a lower sideband signal that repeatedly falls at the same cycle. Simultaneously, these upper sideband signals and lower sideband signals are emitted as transmission waves to the target object, and the distance and speed of the target object are calculated from the frequency difference between each signal and the signal reflected by the target object, that is, the beat frequency. ing.

Thus, according to the present invention, since the transmitted wave contains the rising and falling parts of the frequency at the same time without any time lag, high accuracy can be achieved without error even when the target is moving at high speed. Measurement is possible.

Moreover, since the frequency rising part and the frequency falling part are an upper sideband signal and a lower sideband signal obtained simultaneously by the same modulated wave,
The frequency rise and fall are completely symmetrical and at the same rate,
A complicated correction circuit as in the prior art is not required.

[Example] FIG. 1 shows a block diagram of the radar device.

In the figure, 1 is a local oscillator, which outputs a reference oscillation signal SO having a reference frequency fO in the microwave region. The modulating means 2 includes a modulated wave oscillator 21 and two single sideband up converters 22A and 22B. The modulated wave oscillator 21 emits a modulated signal S1, and the frequency of the modulated signal S1 changes in a sawtooth manner at a constant period tm with the frequency fm as a reference (FIG. 2 (1)). Note that the frequency deviation of the signal S1 is Δf.

Both the reference oscillation signal SO and the modulation signal S1 are input to up converters 22A and 22B, and the up converter 22A generates an upper sideband signal S2 of the sum frequency of both signals 5O1S1. On the other hand, the up converter 22B generates a lower sideband signal S3 with a difference frequency between the two signals 5O1S1. The frequencies of these signals S2 and S3 are shown in Fig. 2 (
As shown in 2>, the frequency rises and falls repeatedly in a sawtooth manner at fixed periods t and m above and below the reference frequency fO, respectively.

The upper sideband and lower sideband signals S2 and S3 are input to the power combiner 6, combined, and emitted as a transmission wave from the transmitting antenna 3 toward a target in the circuit. Note that a portion of each of the signals S2 and S3 is extracted by the directional couplers 7A and 7B on the way.

The above-mentioned emitted wave is reflected by the target object, returns, and is received by the receiving antenna 4. The received reflected wave is input to the power divider 7 and is divided into the mixer 5 which constitutes the signal processing means 5.
Input to 1A and 51B.

Here, the upper sideband reflected signal 32' and lower sideband reflected signal S3- in the reflected waves are shown by broken lines in FIG. 2(2).

As can be seen from the figure, each of the reflected signals 52-5S3- is subjected to a time delay Δt that is proportional to the distance to the target object and a frequency deviation fD that is proportional to the relative speed of the target object.

The mixer 51A inputs the reflected wave and also receives the upper sideband signal S2 from the directional coupler 7A. The signal S2 and the signal 52-5S3- are down-converted by the mixer 51A to become the signal S4.
4, the down-converted components of the signal S2 and the signal S3- have a frequency of (2fm-fD) or more.

By the way, if the frequency fm is set sufficiently larger than the frequency fD, the above-mentioned component can be cut by an appropriate low-pass filter. A filter 52A is provided for this purpose. Thus, the signal S6 that has passed through the filter 52A contains only the down-converted components of the signal S2 and the signal S2-. This is shown in FIG. 2 (3).

As shown in the figure, this down-converted component has a frequency that is the difference between the difference frequency fR due to the time delay Δ and the frequency deviation fD. Note that unnecessary beats indicated by broken lines in the figure are cut by the filter 52A.

Mixer 51B inputs the reflected wave and lower sideband signal S3,
It down converts and outputs a signal S5. Signal S5 is input to filter 52B and output as signal S7.

The process of obtaining signal S7 is similar to the process of obtaining signal S6 described above, and signal S7 includes only down-converted components of signal S3 and signal S3-. This is shown in Figure 2 (4).

As shown in the figure, this down-converted component has a frequency that is the sum of the difference frequency fR and the frequency deviation fD.

Such a signal S6. S7 is input to the signal processing circuit 53.

The configuration of the circuit 53 is shown in FIG. 3, and includes a pair of AD converters 531A, 531B, which input signals S6 and S7, respectively.
Fast Fourier Transform (FFT) processors 532A, 53
2B, and an arithmetic unit 533.

The AD converters 531A and 531B operate at t from time to+Δt.
The above-mentioned signals are converted between o and tm, and then FFT processors 532A and 532B convert the frequencies of these signals fR-
fD and fR+fD are calculated. The arithmetic unit 533 obtains frequencies fR and fD, and from these, the distance and relative speed to the target are obtained, respectively. The obtained distance and relative velocity are displayed on the display 9.

As described above, in the above radar device, the modulation waveform is a sawtooth wave, and the rising slope portion is generated in the upper side wave band and the falling slope portion is generated in the lower side wave band, so that each beat signal is constantly output and at the same time. Signal sampling becomes possible. Furthermore, since the modulated waves input to the two upconverters are the same, the slope symmetry of the modulated output waveforms is extremely good.

FIG. 4 shows an embodiment of the pond of the present invention. In this example, 1
An upper sideband signal S2 and a lower sideband signal S3 are simultaneously generated by the upconverter 22 of the stand, a part of which is taken out by a directional coupler 7 and divided by a power divider 71, and then passed through filters 72A and 72B to the upper sideband signal S3. waveband signal S
2 and a lower sideband signal S3. Each separated signal S2
, S3 are supplied to mixers 51A and 51B.

According to this configuration, only one up-converter is required, making the radar device simple and inexpensive.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention, in which FIG. 1 is a block configuration diagram of a radar device, FIG. 2 is a signal time chart, FIG. 3 is a block configuration diagram of a signal processing circuit, and FIG.
The figure is a block configuration diagram of a radar device showing another embodiment of the present invention. 1...Local oscillator (oscillation means) 2...Modulation means 21...Modulated wave oscillator 22.22A, 22B...Up converter 3...
Transmitting antenna 4...Receiving antenna 5...Signal processing means 51A, 51B...Mixer 52A, 52B...Filter 53...Signal processing circuit Fig. 1 51B 52B S3 Fig. 2

Claims (1)

[Claims] oscillation means for generating a reference oscillation signal that oscillates at a reference frequency; an upper sideband signal that frequency-modulates the reference oscillation signal with the same modulation wave and whose frequency repeats rising at a constant cycle in a region higher than the reference frequency; a modulation means for simultaneously emitting a lower sideband signal whose frequency repeats a fall at the constant cycle in a region lower than the reference frequency; and a transmitting antenna for simultaneously emitting each of the upper sideband and lower sideband signals toward a target. and a receiving antenna that receives the upper sideband reflected signal and the lower sideband reflected signal reflected from the target object, and detects the frequency difference between the upper sideband signal and the upper sideband reflected signal and the lower sideband reflected signal. A radar device comprising signal processing means for detecting a frequency difference between a waveband signal and a lower sideband reflected signal and calculating the distance and speed of the target object from these frequency differences.