JPH0980148A - Fm-cw radar apparatus and noise component judging method in fm-cw radar method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an FM-CW radar with alternated FM-AM noises. SOLUTION: A modulation signal generation means 11 is provided to generate a chopping wave-like modulation signal, an oscillator 12 to output a frequency- modulated high frequency signal according to the modulation signal and a transmitting antenna 14 to transmit the high frequency signal. In addition, a receiving antenna 15 is provided to receive a reflected signal on a target object and a directive coupler 13 to separate a part of the high frequency signal outputted to the transmitting antenna 14 from the oscillator. Moreover, a mixer 16 is provided to output a beat signal by mixing the high frequency signal separated and the reflected signal received and a frequency analysis means 17 to analyze a frequency component of the beat signal. In an FM-CW radar apparatus thus arranged, a distance to the target object is calculated from the frequency of the beat signal and changes in the frequency. A phase changing means 18 is provided to change the phase of the signal and a noise judging means 20 to judge a noise component by detecting a level change in frequency components corresponding to a phase change in the phase changing means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention transmits a high frequency signal FM-modulated so that the frequency changes in a triangular wave form,
The present invention relates to an FM-CW radar device that calculates the distance to a target object from changes in the frequencies of the beat signal of the transmitted wave and the reflected wave and the frequency synchronized with the modulation signal, and particularly, a determination for reducing noise in the FM-CW radar device. Regarding the technique.

[0002]

2. Description of the Related Art An FM-CW radar system is a radar system capable of simultaneously measuring a relative velocity and a distance to a target object.
It is used as a device for monitoring the distance between vehicles.
FIG. 18 is a diagram showing the basic configuration of the FM-CW radar device. In FIG. 18, reference numeral 11 is a modulation signal generation circuit for generating a triangular wave modulation signal, and 12 is a high frequency oscillator whose frequency changes according to the triangular wave modulation signal output from the modulation signal generation circuit 11. Yes, 14
Is a transmitting antenna for transmitting the output of the oscillator 12, and
Reference numeral 5 is a receiving antenna for receiving the signal output from the transmitting antenna 14 and reflected by the target object and returning.
Is a directional coupler that branches a part of the power output from the oscillator 12 to the transmitting antenna 14, and 16 mixes the high-frequency signal branched by the directional coupler 13 with the received signal from the receiving antenna 15. This is a mixer that outputs a beat signal.

FIG. 19 is a diagram showing a received signal when the relative velocity of the target object is zero. (1) shows changes in the frequencies of the transmitted signal and the received signal, and (2) shows the frequency of the beat signal. Show changes. The frequency of the transmission signal changes in a triangular wave shape as shown in (1) of FIG. f ₀ indicates the center frequency of the transmission signal, Δf indicates the frequency change width, and fm is 3
Indicates the frequency of the square wave. If the relative velocity of the target object is zero, the frequency of the signal reflected by the target object does not change, and the received signal is delayed by the round-trip time traveling back and forth from the transmission antenna to the target object. As shown in 1), the frequency of the received signal changes with a delay of the round trip time from the transmitted signal. Therefore, when the beat signal of the transmission signal and the reception signal is taken, its frequency changes as shown in (2) of FIG. That is, the frequency of the beat signal becomes the constant value fr for the predetermined period. This fr corresponds to the delay of the received signal with respect to the transmitted signal, and is proportional to the round-trip time, that is, twice the distance from the antenna to the target object. If the distance to the target object is R, then R = fr · c / (fm · Δf)
(C is the speed of light). Therefore, if fr is detected, the distance from the antenna to the target object is known.

When the relative velocity of the target object is not zero,
A change in the frequency of the received signal due to the Doppler effect is superimposed on the delay of the received signal due to the distance to the target object.
FIG. 20 is a diagram showing a received signal when the relative velocity of the target object is not zero, (1) shows changes in frequency of the transmission signal and the received signal, and (2) shows changes in frequency of the beat signal. . When the relative speed is not zero, the frequency of the received signal changes due to the Doppler effect. When moving away, the frequency of the received signal decreases, and when approaching, the frequency of the received signal increases. For example, in the portion where the frequency of the transmission signal increases, the frequency of the reception signal increases with a delay, but when the target object approaches, the frequency of the reception signal increases due to the Doppler effect. As shown, the frequency difference becomes smaller by the frequency change fd due to the Doppler effect than when the relative velocity is zero. Further, in the portion where the frequency of the transmission signal decreases, the frequency of the reception signal decreases with a delay. However, when the target object approaches, the frequency of the reception signal decreases due to the Doppler effect. As shown, the difference in frequency is larger by fd than when the relative speed is zero. Therefore, the frequency of the beat signal is
As shown in (2) of FIG. 20, with respect to the frequency fr of the beat signal determined by the distance to the target object, the frequency of the transmission signal increases and decreases, and the frequency increases and decreases by fd due to the Doppler effect, respectively. It becomes the frequency. Therefore, by detecting fr and fd, the distance to the target object and the relative speed can be calculated. When the relative velocity of the target object is v, there is a relationship of v = (c / 2f ₀ ) × fd.

The oscillator 2 needs to change the oscillation frequency according to the applied triangular wave modulation signal, and a voltage controlled oscillator (VCO) is used. In an FM-CW radar device used as a device for monitoring the distance between vehicles such as automobiles, the distance to a target object in front is 100 m at most and the relative speed is 1
Since it is 00 km / h, the maximum frequency shift amount is about 100 MHz in order to ensure sufficient distance measurement accuracy, and the millimeter wave band is used as the transmission frequency band in order to ensure sufficient relative speed measurement accuracy. Must be used.

[0006]

By the way, in the conventional millimeter wave FM-CW radar, the F with a very large frequency deviation is used.
In order to perform M modulation, an AM component having almost the same frequency component as the modulation signal is superimposed on the VCO output due to the slope of the oscillation frequency vs. output power characteristic of the voltage controlled oscillator. The generation of this AM component will be described below.

FIG. 21 is a diagram showing the relationship between the VCO applied voltage and the output power. As shown, the output power changes with the applied voltage. Now, as shown in (1) of FIG. 22, when a modulation signal that changes in a triangular wave shape between Vb and Va centering on the voltage Vc is applied to the VCO, the frequency of the signal output from the VCO is similar to the modulation signal. Changes to
As described above, since the output power changes depending on the applied voltage, the power of the output signal also changes at the same time as the signal shown in (1) of FIG.

The output signal from the VCO is frequency-converted by the mixer 16, but since the voltage generated by the AM detection in the mixer 16 is proportional to the local power, the power is reduced as shown in FIG.
If it changes like (1) of 2, AM noise as shown in (2) will be detected. FIG. 23 shows FM-
It is a figure which shows the result of the frequency analysis when the above noise exists in a CW radar. As shown in the figure, a peak occurs at a frequency value corresponding to the distance to the target object, and a peak occurs at a frequency that is an integral multiple of the modulation frequency. Although the case where the number of target objects is one is shown here, when the radar captures a plurality of objects, a plurality of peaks corresponding to the plurality of objects occur.

Actually, since the frequency of the triangular wave for FM modulation, that is, the frequency of AM noise and the frequency value of the reflected signal obtained by FM detecting the wave reflected from the target object are close to each other, the reception S / N is deteriorated. There is a problem of doing. Especially,
When the distance to the target object is short, fr becomes small and becomes close to the frequency of the AM noise, as described in FIG. 18, so that the S / N is further deteriorated. Therefore, there is a problem that the required detection range cannot be secured unless the transmission output is increased. Therefore, at present, expensive oscillators such as impat diode and gun diode are used for the oscillator.

In order to solve such a problem, Japanese Unexamined Patent Publication No.
No. 40169 discloses an FM-CW radar in which a second modulator is provided only on one path, and the output of the mixer 16 is frequency-converted by the frequency of the second modulator. Further, in this document, as shown in FIG. 24, a switching means is provided on the other path, and the switching means is operated by the same modulation signal as the second modulation means, thereby further reducing the noise. It is disclosed.

The present invention can reduce noise in an FM-CW radar with a simpler configuration different from the noise reduction technique disclosed in Japanese Patent Laid-Open No. 5-40169, and in Japanese Patent Laid-Open No. 5-40169. An object of the present invention is to provide a noise reduction technique capable of further noise reduction by combining with the disclosed noise reduction technique.

[0012]

FIG. 1 is a block diagram of the FM-type of the present invention.
It is a figure which shows the basic composition of a CW radar. As shown in FIG. 1, the FM-CW radar of the present invention is a high frequency signal frequency-modulated according to a modulation signal generating means 11 for generating a triangular wave modulation signal and a modulation signal output from the modulation signal generating means 11. Oscillator 12, a transmitting antenna 14 for transmitting a high frequency signal output from the oscillator 12, a receiving antenna 15 for receiving a reflected signal of a high frequency signal radiated from the transmitting antenna 14 at a target object, and a transmitter 12 for transmitting from the oscillator 12. Directional coupler 13 that separates a part of the high-frequency signal output to antenna 14, and a mixer that mixes the high-frequency signal separated by directional coupler 13 and the reflected signal received by receiving antenna 15 and outputs a beat signal. 16 and a frequency analysis means 17 for analyzing the frequency component of the beat signal output from the mixer 16, which is the same as the frequency of the beat signal and the modulated signal. In the FM-CW radar device that calculates the distance to the target object from the change in the frequency, the phase is changed by changing the phase of the input signal provided in the path from the receiving antenna 15 to the mixer 16 in order to achieve the above object. The phase changing means 18 and the noise judging means 20 for judging the noise component by detecting the level change corresponding to the phase change in the phase changing means 18 in the frequency component output from the frequency analyzing means 17 are provided. Characterize.

The phase changing means 18 may be provided in the path from the directional coupler 13 to the transmitting antenna 14 or the path from the directional coupler 13 to the mixer 16, or may be provided at a plurality of locations. Further, the noise component determination method in the FM-CW radar method of the present invention transmits a high frequency signal frequency-modulated according to a triangular wave modulation signal, receives a high frequency signal reflected by a target object, and outputs the high frequency signal as a high frequency signal. Noise component determination in FM-CW radar method that mixes reflected signals to generate beat signals, analyzes the frequency components of beat signals, and calculates the distance to the target object from changes in the frequencies and frequencies synchronized with the modulation signals Method, and from the analysis results,
A first storing step of storing the level of each beat signal for each frequency; a phase changing step of changing a phase of at least one of a high frequency signal to be transmitted, a received reflection signal and a high frequency signal to be mixed by a predetermined amount; From the subsequent analysis result, the level difference of each frequency stored in the first storage step and the second storage step is compared with the second storage step of storing the level of each frequency of the beat signal, and the level difference of a predetermined level or more is compared. And a comparison step of determining the frequency of 1 as noise.

In FIG. 1, a low-frequency oscillator 19 for generating a signal having a frequency lower than that of the oscillator 12 is provided, and the amount of phase change in the phase changing means 18 changes according to the signal output from the low-frequency oscillator 19. However, the phase changing means 18 is not limited to this, and the phase changing means 18 may change the phase changing amount continuously or stepwise. In the microwave circuit, in addition to the AM noise described with reference to FIGS. 20 to 22, AM noise is generated due to unnecessary reflection in the circuit. FIG. 2 is a diagram showing an example of a route of noise in the FM-CW radar device. For example, the transmitting antenna 14
Transmits a high frequency signal, but reflection also occurs than VSWR. Although the isolation means prevents the reflected signal from becoming noise, since leakage cannot be completely prevented, noise is generated. This noise mixes into the mixer 16 via the directional coupler 13 and causes noise in the beat signal. Further, the high-frequency signal leaked from the mixer 16 to the receiving antenna 15 is reflected by the receiving antenna 15 and is mixed into the mixer 16 in the same manner to generate noise in the beat signal.

Since such noise is mixed in the mixer 16 and mixed in the beat signal, when the frequency of the beat signal is analyzed, an unnecessary peak is generated in addition to the peak corresponding to the target object. When the phases of the noises in the mixer 16 match, the noises interfere with each other to generate a large peak, but conversely the phase is 180 °.
When they are different, they cancel each other and the peak becomes smaller. In the present invention, the phase changing means is arranged in the middle of the path,
Since the phase of the signal is changed, the peak value of the portion of the frequency component of the beat signal corresponding to the noise varies with the phase change by the phase changing means. FIG.
FIG. 4 is a diagram showing an example of changes in peak value in a beat signal due to a phase change. As shown in the figure, the peak value of the frequency corresponding to the target object does not change, but the peak value of the noise component changes. In other words, it can be said that the peak value changes when the phase is changed.

In the FM-CW radar device of the first aspect of the present invention, the phase changing means 18 changes the phase, and the noise determining means 20 detects the level change in the frequency component of the beat signal, so that the noise component is detected. It is determined that there is. If it is found to be a noise component, it can be removed. Further, the present invention can be combined with a conventional example in which switching means is provided for removing noise as shown in FIG.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 4 is a diagram showing the configuration of a first embodiment of the present invention. In FIG. 4, reference numeral 11 is a modulation signal generation circuit for generating a triangular wave modulation signal.
Reference numeral 2 is an oscillator such as a VCO that outputs a high frequency signal frequency-modulated according to the modulation signal output from the modulation signal generation circuit 11, 14 is a transmission antenna that transmits the high frequency signal output from the oscillator 12, and 15 is a transmission antenna. Antenna 1
Reference numeral 13 is a receiving antenna for receiving a reflected signal of a high frequency signal radiated from 4 on a target object, 13 is a directional coupler for separating a part of the high frequency signal output from the oscillator 12 to the transmitting antenna 14, 16 Is a mixer that mixes the high-frequency signal separated by the directional coupler 13 and the reflected signal received by the receiving antenna 15 to output a beat signal, and 17 is an FFT (analyzes the frequency component of the beat signal output by the mixer 16). Fast Fourier Transfer) and corresponds to the frequency analysis means in FIG. Reference numeral 20 denotes a computer, which performs processing such as calculation of the distance from the output of the FFT 17 to the target object and relative speed. The above parts are the same as those of the conventional FM-CW radar device, and detailed description thereof is omitted here. The oscillator 12, the directional coupler 13, the mixer 16, and the phase variable circuit 18 are formed as the high frequency circuit 2, and the modulation signal generation circuit 11, the FFT 17, and the computer 20 are formed as the signal processing circuit 1.

In FIG. 4, reference numeral 18 is a phase variable circuit, which delays and changes the phase of the signal received by the receiving antenna 15. The delay amount changes according to the input signal from the computer 20. The computer 20 is an FF
The peak value is detected from the frequency analysis result of the beat signal output from T17. If there are multiple target objects, there will be multiple peak values, but if noise is mixed in the beat signal, a peak will also occur in the noise frequency, making it impossible to determine whether the target object or noise. . In the present embodiment, the computer 20 temporarily stores the frequency of the peak value and its level from the frequency analysis result of the beat signal output from the FFT 17, and then changes the signal output from the computer 20 to the phase variable circuit 18 to change the phase variable circuit. The delay amount at 18 is changed. It is desirable that the delay amount can be changed, for example, within a fraction to several times the period of the FM-AM noise.
After changing the delay amount in the phase variable circuit 18, the peak value frequency and its level are stored from the frequency analysis result of the beat signal and compared with the level before changing the phase. When the amount of delay in the phase variable circuit 18 changes, the level of the peak corresponding to the target object does not change in the frequency analysis result of the beat signal, but the amount of noise changes. Judge as noise. According to this determination result, the peak determined to be noise is removed. Therefore, the computer 20 corresponds to the noise determining means in FIG.

Next, the phase variable circuit will be described. Various circuits for changing the phase have been proposed in the past, and it is possible to use them. FIG. 5 shows a phase shifter in which metal or dielectric plates 52 and 54 can be inserted in the middle of the waveguides 51 and 53, and the delay amount changes according to the insertion amount. And (2) shows an L-type phase shifter.

FIG. 6 shows a circuit in which two lines 57 and 58 having different lengths are provided between the input line 55 and the output line 56. Each line is connected by a PIN diode 59.
By switching the level of the switching signal, one of the lines 57 and 58 is selected and the delay amount changes. In FIG. 7, between the input line 60 and the output line 61,
This is a circuit in which one side is provided with an open line 62, the middle of which is grounded via a PIN diode and a switching signal is applied. By switching the level of the switching signal, the path of the signal passing through the line 62 changes, and the line length changes. This changes the delay amount. Such a circuit is realized by a hybrid circuit.

In FIG. 8, a circulator 66 is provided between an input line 64 and an output line 65, a line 62 whose one end is opened from the circulator 66 is extended, and a PIN is provided in the middle thereof.
It is a circuit which is grounded via a diode and to which a switching signal is applied. FIG. 9 is a circuit in which a line similar to the circuit in FIG. 7 is configured by a hybrid circuit and one end is grounded via a varactor diode 72.

FIG. 10 shows a circuit in which one of the lines 76 of the circuit of FIG. 8 is grounded via a varactor diode 77.
As described above, any of the phase shifters shown in FIGS. 5 to 10 can be used as the phase variable circuit 18. As in the present embodiment, the VCO used as the oscillator 12 is relatively resistant to fluctuations in the oscillation frequency by changing the phase and determining the change in the frequency component of the beat signal as noise and making it removable. It becomes possible to use a circuit having a large output fluctuation as shown in FIG.

Next, regarding the processing of the beat signal, FIG.
This will be described with reference to FIG. The beat signal output from the mixer 16 is subjected to fast Fourier transform processing by the FFT 17, and its frequency component is analyzed. The computer 20 extracts a peak from the frequency analysis result of the beat signal and stores the frequency and level. Next, the phase of the phase variable circuit 18 is changed and the same processing as above is performed. Then, the peaks before and after the phase change are compared, and the frequency at which the level changes greatly is detected. Since the frequency whose level changes greatly is noise, such peaks are removed, and the distance to the target object is calculated from the remaining peaks and output. After such processing, the phase is further changed and the same processing is repeated.

In the embodiment of FIG. 4, the phase variable circuit 18 is
Although it is arranged between the receiving antenna 15 and the mixer 16, as shown in FIGS. 13 and 14, the path from the directional coupler 13 to the transmitting antenna 14 or the path from the directional coupler 13 to the mixer 16 is arranged. It can also be provided. The operation is the same. FIG. 15 is a diagram showing the configuration of the FM-CW radar device of the second embodiment in which the present invention is applied to the FM-CW radar device in the case of using an antenna for both transmission and reception in which an antenna for both transmission and reception is used.

As can be seen by comparing FIG. 15 with FIG.
The difference from the first embodiment is that a transmitting / receiving antenna 22 is provided in place of the transmitting antenna 14 and the receiving antenna 15,
Circulator 2 for separating transmission signal and reception signal
1 is provided. As the circulator 21, a conventional circulator having a magic T circuit or the like can be used. Also in this case, the position where the phase variable circuit 18 is provided can be changed as in FIGS. 13 and 14.

FIG. 16 is a diagram showing the configuration of a third embodiment in which the switching circuit shown in FIG. 24 is added to the first embodiment of FIG. As is clear from comparison with FIG. 4, in the FM-CW radar device of the third embodiment, the low-frequency oscillator 19 that outputs a signal having a frequency smaller than the frequency of the signal output by the oscillator 12, and the phase variable circuit 18 Circuit 23 for AM-modulating the output of the oscillator according to the signal of the oscillator 19.
And a mixer 24 for demodulating the output of the mixer 16 to the baseband, and the other parts are the same as those in the first embodiment.

FIG. 17 is a diagram showing a configuration example of the switching circuit 23 realized by using a PIN diode. The phase variable circuit 18 changes the delay amount according to the signal output from the low frequency oscillator 19. The computer 20 receives the signal output from the low frequency oscillator 19 and receives the signal from the phase variable circuit 18
The FFT processing result of the beat signal according to the change in the phase at is analyzed.

The effect of providing the switching circuit 23 and the mixer 24 is disclosed in Japanese Patent Application Laid-Open No. 5-40169, and therefore its explanation is omitted here. In any case, the present invention can be applied in combination with the configuration disclosed in Japanese Patent Laid-Open No. 5-40169, whereby noise can be further reduced and the detection accuracy of the target object can be improved. It is possible.

[0029]

As described above, according to the present invention,
An FM-CW radar device with reduced FM-AM noise can be realized with a simple configuration, and the detection accuracy of a target object can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of an FM-CW radar device of the present invention.

FIG. 2 is a diagram illustrating a noise path in an FM-CW radar device.

FIG. 3 is a diagram for explaining a level change of frequency according to a phase change in the present invention.

FIG. 4 is a diagram showing a configuration of an FM-CW radar device according to a first embodiment.

FIG. 5 is a diagram showing an example (No. 1) of a phase variable circuit.

FIG. 6 is a diagram showing an example (No. 2) of a phase variable circuit.

FIG. 7 is a diagram showing an example (No. 3) of a phase variable circuit.

FIG. 8 is a diagram showing an example (No. 4) of a phase variable circuit.

FIG. 9 is a diagram showing an example (No. 5) of a phase variable circuit.

FIG. 10 is a diagram showing an example (6) of a phase variable circuit.

FIG. 11 is a diagram showing a configuration example of a VCO used in the first embodiment.

FIG. 12 is a diagram showing a process of determining noise by changing the phase in the first embodiment.

FIG. 13 is a diagram showing a modified example (1) of the arrangement of the phase variable circuit.

FIG. 14 is a diagram showing a modified example (part 2) of the arrangement of the phase variable circuits.

FIG. 15 is an FM-C having an antenna for both transmission and reception of the present invention.
It is a figure which shows the structure of 2nd Example applied to the W radar apparatus.

FIG. 16 shows an FM-C having a switching circuit according to the present invention.
It is a figure which shows the structure of 2nd Example applied to the W radar apparatus.

FIG. 17 is a diagram showing a configuration example of a switching circuit used in the second embodiment.

FIG. 18 is a diagram showing a configuration of an FM-CW radar.

FIG. 19 is a diagram showing a received signal from an object having a relative velocity of zero in the FM-CW radar.

FIG. 20 is a diagram showing a signal received by an object having a relative velocity in the FM-CW radar.

FIG. 21 is a diagram showing applied voltage-output power characteristics of a VCO.

FIG. 22 is a diagram illustrating generation of FM-AM noise.

FIG. 23 is a diagram showing the influence of noise on the frequency analysis result.

FIG. 24 is a diagram showing a configuration of a conventional example for removing noise.

[Explanation of symbols]

 11 ... Modulation signal generating means 12 ... VCO 13 ... Directional coupler 14 ... Transmitting antenna 15 ... Receiving antenna 16 ... Mixer 17 ... FFT circuit 18 ... Phase changing means 20 ... Noise judging means

Claims (13)

[Claims] 1. A modulation signal generating means (11) for generating a triangular wave modulation signal, and an oscillator (which outputs a high frequency signal frequency-modulated according to the modulation signal output by the modulation signal generating means (11)). 12), a transmitting antenna (14) for transmitting a high frequency signal output from the oscillator (12), and a receiving antenna (15) for receiving a high frequency signal radiated from the transmitting antenna (14) reflected by a target object. )
A directional coupler (13) for separating a part of the high frequency signal output from the oscillator (12) to the transmitting antenna (14), and the high frequency signal separated by the directional coupler (13) And a mixer (16) for mixing the reflected signals received by the receiving antenna (15) to output a beat signal, and a frequency analysis means (17) for analyzing the frequency component of the beat signal output by the mixer (16). In the FM-CW radar device, comprising: a frequency of the beat signal and a change in frequency synchronized with the oscillation signal to calculate a distance to a target object, the directional coupler (13) to the transmitting antenna (1
4), the path from the receiving antenna (15) to the mixer (16), and the directional coupler (13)
To the mixer (16) in at least one place for changing the phase of the input signal, and in the frequency component output from the frequency analysis means (17), A noise judging means (20) for judging a noise component by detecting a level change corresponding to the phase change in the phase changing means (18).
M-CW radar device. 2. A low frequency oscillator (19) for generating a signal of a frequency lower than that of the oscillator (12), wherein the phase change amount in the phase changing means (18) is output from the low frequency oscillator (19). The FM-CW radar device according to claim 1, which changes according to a signal. 3. Switching means (2) for connecting and disconnecting at least one of a signal transmitted from the transmitting antenna (14) and a signal received by the receiving antenna (15).
The FM-CW radar device according to claim 1, comprising 1) and a second mixer (22) for mixing the intermittent signal of the switching means (21) with the output of the mixer (16). 4. Switching means (2) for connecting and disconnecting at least one of a signal transmitted from the transmitting antenna (14) and a signal received by the receiving antenna (15).
1) and a second mixer (22) for mixing the intermittent signal of the switching means (21) with the output of the mixer (16), the switching means (21) including the low frequency oscillator (19). According to the signal of or the signal generated from it,
The FM-CW radar device according to claim 2, which performs an intermittent operation. 5. The FM-CW radar device according to claim 2, wherein the phase changing means (18) is capable of continuously changing the amount of phase change. 6. The FM-CW radar device according to claim 2, wherein the phase changing means (18) changes the amount of phase change stepwise. 7. The phase change means (18) is a waveguide type phase shifter in which the amount of phase change changes according to the amount of metal or dielectric inserted in the waveguide. The FM-CW radar device according to item 1. 8. The FM-CW according to claim 1, wherein the phase changing means (18) is a phase shifter that switches two or more lines having different path lengths by a PIN diode. Radar equipment. 9. The phase change means (18) is a reflection type phase shifter for changing the line length of the hybrid line by driving a diode connected to the line. The FM-CW radar device according to item 1. 10. The phase changing means (18) is a reflection type phase shifter for changing the line length by driving a circulator and a diode connected to a line extending from the circulator. The FM-CW radar device according to any one of 1. 11. The FM-CW radar device according to claim 9, wherein the diode is a PIN diode. 12. The FM-CW radar device according to claim 9, wherein the diode is a varactor diode. 13. A beat signal is generated by transmitting a high frequency signal frequency-modulated according to a triangular wave modulation signal, receiving a reflection signal of the high frequency signal at a target object, and mixing the high frequency signal and the reflection signal. FM for generating, analyzing the frequency component of the beat signal, and calculating the distance to the target object from the change in the frequency and the frequency synchronized with the modulation signal
A method of determining a noise component in a CW radar method, wherein a first storage step of storing a level of each frequency of the beat signal from the analysis result, the high frequency signal to be transmitted, the received reflection signal are mixed. A phase changing step of changing at least one phase of the high frequency signal by a predetermined amount; a second storing step of storing a level for each frequency of the beat signal from the analysis result after the phase change; A noise component in the FM-CW radar device, comprising: a step of comparing the level difference between the frequencies stored in the second storage step, and determining a frequency having a level difference of a predetermined value or more as noise. Judgment method.