JPS62229085A - Frequency agility radar - Google Patents

Abstract

PURPOSE:To enable a least jamming frequency (LJF) to be detected by mixing local signals with received signals with regard to jamming waves, applying the IF signals of a desired band to the elastic surface wave electrode of an RF spectrum analyzer and analyzing stored optical data. CONSTITUTION:When the quantity of received and stored light of each CCD, namely, the quantity of signals of each frequency of jamming waves FJ (F1-F9) during every radar receiving period is as shown in the accompanying Fig. (d), referring to the temporally first radar receiving period T1, the quantity of the signals of each frequency of the jamming wave F1 shown in Fig. 2, (d) is relatively large corresponding to the frequencies F1-F9 (CCD positions A1-A9) and minimum corresponding to the frequency F2 (CCD position A2). That is, the frequency F2 is an LJF. When digital signals with regard to the frequency analysis content of the jamming waves FJ are obtained, by temporarily storing the digital signals at required and comparing the level contents thereof, the LJF for every radar receiving period can be detected.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) This invention is aimed at counteracting the act of disabling the radar function due to interference waves from the other party when performing, for example, searching, monitoring, and tracking using a radar device. The minimum interference frequency (L
JF: Least Jamming Freque
This invention relates to a frequency agility radar that rapidly and variably controls the RF frequency of a Todoroki radar device to follow this LJF while sequentially detecting the LJF.

(Prior Art) Radars used for searching, monitoring, tracking, etc. are generally used with their RF frequencies fixed. However, if the target targeted by the radar is a partner that has active means such as electronic devices or reflective devices, and the target partner feels inconvenient for its own position to be detected. Normally, the other party uses a so-called electronic counterdetection device (E (+M: Electr
onicCounterMeasures) to disable the radar function, the radar device in question performs the above-mentioned RF frequency switching in order to counteract this and avoid the influence of the interference waves. However, if the same RF frequency is switched slowly, the other side can easily detect the same frequency and easily interfere with it. Therefore, in order to make this switch effective, it is necessary to There is a fee to counter this with frequency agility, which allows this RF frequency to change quickly at or slightly lower frequencies. This is also called electronic countermeasure (ECCM).
This is a well-known technique known as ter Counter Measures.

Now, this frequency agility usually means several to dozens of RF waves.
The frequency is changed by the same frequency, and there are two methods as follows.

1) Random agility method 2) LJF (least jamming frequency) agility method Below, these two frequency agility methods are shown in Figures 3 to 6.
This will be briefly explained with reference to the drawings.

1) Random agility method This method is based on the rule that it is difficult for the other side to detect regardless of the same frequency of RF waves that the radar has, or the same frequency of the RF interference waves. It is a method of using and agility. This-
Examples are shown in FIGS. 3 and 4.

That is, as shown in FIG. A transmitting circuit 120 transmits these RF frequency signals Fx (which performs necessary modulation), and supplies power to an antenna 140 in response to the transmitted signals, and
When a reflected signal from a target is received at 40, a feeding circuit 130 extracts the power of the received signal through the antenna 140, and a receiving circuit demodulates the extracted power (received signal) based on the local signal. 1501 and an indicator 160 that visually displays information regarding the position of the target based on the demodulated signal, and the other party 200 serving as the target A radar wave detection circuit 230 detects the RF frequency x of the transmission signal transmitted from the radar side 100, and based on the detected RF frequency x, an interference wave F having a frequency that becomes this noise wave
, which is transmitted to the same feeding circuit 220 and the antenna 21
In this agility method, as shown in the figure, x of F, ~Fx is provided on the radar side 100 as shown in the figure.
Random agility data generation circuit 17 that generates data to randomly select the same frequency of the 4 RFs.
0 is provided, and the local signal frequency is determined at any time based on the random agility data generated from the generation circuit 170. As a result, as shown in FIG. 4, the RF frequency F of the radar signal transmitted from the radar side 100 is
Agility is randomly applied in the range of 1 to Fx.

However, this method is simple as it does not require a circuit to detect the same RF frequency of the above-mentioned interference waves, but in practice, it is necessary to detect the same RF frequency of the above-mentioned several to several tens of RF waves, ~F
Any one wave of X will match the RF same frequency of the above-mentioned interference wave, and there is a drawback that it will be interfered with by the reciprocal of the probabilistically variable RF same frequency number. To overcome this drawback, it would be better to increase the variable RF frequency, but
On the contrary, this results in the disadvantage that the device becomes larger and more complicated.

2) LJF agility method This method detects the aforementioned LJF by constantly measuring the signal level of the RF same frequency of interference waves that have the same frequency of several to dozens of RF waves possessed by the radar, This method uses data regarding the detected LJF to agility the RF frequency of the relevant transmission signal. An example of this is shown in FIGS. 5 and 6.

That is, assuming that the radar side and the other side are basically configured as shown in Figure 5 (these basic configurations are the same as those shown in Figure 3 above, and the same circuit is used for each circuit). In this agility method, as shown in FIG. 5, the radar side 10
0, interference wave F.

An LJF detection circuit 1 having an antenna 1 for receiving the signal and detecting the LJF described above in the above manner from the received signal.
80 is provided, and the local signal frequency is determined at any time based on the data related to LJF detected by the detection circuit 180 so as to follow this. FIG. 6 shows the interference wave F1 in this case. and LJF.

As described above, this LJF agility method has the drawback that the device becomes larger and more complicated due to the need for the LJF detection circuit 180, but in terms of its function,
In principle, the RF frequency of the interference wave and the RF frequency of the transmission signal do not match, so there is an advantage that the variable RF frequency is at least less susceptible to the influence of the interference wave.

Of course, if this variable RF frequency is too small, LJF
Detection becomes meaningless. For example, if there are only about three waves at the same RF frequency, if multiple interference waves are emitted (usually more than one is emitted), it will be impossible to detect the frequency corresponding to LJF. .

Figure 7 shows the L used in this LJF agility method.
A general configuration of a JF detection circuit is shown. Here, as an example, a case is shown in which nine RF frequencies are used.

As shown in FIG. 7, this LJF detection circuit 180a uses an antenna 1 for receiving interference waves, which normally uses an omnidirectional antenna to receive the above-mentioned interference wave F, and a signal received by the antenna 1. The RF switch 2 is turned on and off by the radar transmission blanking gate signal to prevent saturation and destruction of the reception section due to the wraparound of radar transmission waves. R that automatically controls (automatically suppresses) the acceptance level of
An F attenuator 3, an RF amplifier 4 that amplifies the level-suppressed received signal to a required level, and an IF that mixes the level-suppressed received signal (including interference waves) with a local signal LCL, which will be described later. (intermediate frequency) mixer 5, which removes unnecessary harmonic components during signal mixing by the mixer 5 and extracts only the IF multiplied signal of the desired frequency band; I was
A LOG amplifier 7 that logarithmically compresses the F-fold signal, a detector 8 that converts the logarithmically compressed IF-fold signal into a video signal vDa, and A that converts the converted video signal ■Da into a digital signal.
/D (analog/digital) converter 9, a level memory 10 that sequentially temporarily stores the A/D converted video data D1a, and sequentially reads the stored data from the memory 10 at each pulse repetition period of the transmission signal. , the level information indicated by this read data D2al is compared, and the frequency information corresponding to the data indicating the minimum level value among them is set as LJF data and the local signal generating circuit 11
0 (FIG. 5); local oscillators 21 to 29 that oscillate local signals LCL of frequencies f1 to f, respectively, corresponding to the RF frequencies tomoe to F9 transmitted and received from the radar; A switch circuit (9) that sequentially switches and outputs these local signals LCL, and an RF amplifier that amplifies the switched and output local signals LCL to a level matching the level of the amplified signal by the RF amplifier 4 and supplies this to the mixer 5. and each local signal LCL consisting of the above-mentioned frequencies f, ~f, corresponding to the radar reception period of the radar concerned.
a local signal switching signal CG for sequentially switching and controlling the
and the A/D converter 9 in accordance with the switching timing.
An A/D conversion command signal C1a for controlling sampling timing during A/D conversion in , and the level storage 1 corresponding to the sampling timing.
Storage command signal C2a for controlling data write timing of 0.

and a comparison command signal C3a for controlling the comparison start timing of the level comparator 11 corresponding to the radar reception period of the radar.
The circuit includes a D converter 9, a level storage device 10, and an LJF detection control circuit 40a for outputting to a level comparison ill.

FIG. 8 shows the LJF detection circuit 180a shown in FIG.
This is a timing chart showing an example of the operation of the LJF detection circuit 180.
An overview of the operation of a will be explained.

Now, in response to a radar master trigger signal having a pulse repetition period as shown in FIG. 8(a), the RF frequency F is
The radar signal set to any one of 1 to F is the 8th radar signal.
If it is transmitted at the timing shown in Figure (b), the radar transmission blanking gate signal mentioned above will be as shown in Figure 8 (C).
The radar device and the LJF are formed in the manner shown in
The radar reception period of the detection circuit 180a is determined. At this time, it is assumed that the LJF detection control circuit 40a generates the local signal switching signal CG in a manner as shown in FIG. 8(d) corresponding to the radar reception period. As a result, the frequency of the local signal LCL mentioned above is sequentially switched to fS-f in the manner shown in FIG. 8(e).

Now, in response to the transmission of such a radar signal, interference [F] is emitted from the aforementioned partner side 200 (@ Figure 5) in the manner shown in Figure 8(f) 4, and this is received by the interference wave receiving antenna 1. Then, the received signal of the interference wave F, and the local signal LCL of the frequencies f and -f are sequentially mixed in the mixer 5, and the IF multiplied signal of the level corresponding to each of these mixing amounts is generated. The signals are taken out from the mixer 5 in accordance with the frequency switching mode. It is assumed that the video signal VDa detected by the IF multiplied signal detector 8 is as shown in FIG. 8(g). here this 8th
The video signal VDa shown in FIG. 3(g) has local frequencies aft, fS-f4. fS, f? , fS, fll(R
F frequency F, r Fs + Fa + Fa + Fy
r Fs +″F, ), the interference is more than a certain level, while the local frequency f, (RF frequency F, ) is relatively little interference, and the local frequency f, (RF
Corresponding to frequency F,), the state in which the least amount of interference is received is shown.

The A/D converter 9 sequentially A/D converts the video signal VDa based on the A/D conversion command signal C1a applied from the LJF detection control circuit 40a at the timing shown in FIG. The number direct data Dla as shown in the figure (t+) is output, and the level storage device 10 further stores
The A/D converted data Dla by this A/D converter 9 is based on the storage command signal C2a applied from the same<LJF detection control circuit 40a at the timing shown in FIG. 8(j).
are sequentially stored in the manner shown in FIG. 8(k).

In the level comparator 11, the LJF detection control circuit 40
A comparison command signal C3 is added at the timing shown in FIG. 8(1) corresponding to the radar reception period from a.
Start sequential reading of data D2a stored in the storage device 10 based on step a and comparison of the level contents thereof,
When data with minimum level content is detected,
LJF data as shown in FIG. 4(E) is output to the local signal generation circuit 110. For example, the above-mentioned time 2
Corresponding to the th radar reception period T, the local frequency fs (Rp
The LJF data is output in synchronization with the reception timing of data regarding the frequency F.

Therefore, on the radar side 100, the LJF at that point in time can be detected based on the generation timing of this LJF data, and the next radar transmission signal based on the pulse repetition period is transmitted at an RF frequency that matches this LJF. That will happen. By repeatedly performing these operations, the other party 20 as described above
It becomes possible to realize transmission and reception of radar signals that are hardly affected by interference waves from zero.

However, in such an LJF detection circuit 180a, since the observation time for each frequency f, ~f of the local signal LCL is limited corresponding to the timing of the local signal switching signal CG, the frequency of the interference wave is limited. If the LJF signal level does not change or if the rate of change is slow, LJF can still be detected effectively by the time-sharing method described above. In the case where the frequency or signal level of Since the detection period of the frequency signal is extremely limited, there is a problem that accurate detection of LJF becomes unstable.

(Problems to be solved by the invention) This invention solves the above-mentioned LJF agility method.
This is intended to solve the disadvantage of the JF detection circuit, that is, the inconvenience that the LJF cannot be detected when the frequency of the interference wave or its signal level changes during the radar reception period.

[Structure of the invention]

(Means for Solving the Problems) In the present invention, a local signal is mixed with the received signal regarding the interference wave, and this mixed IF multiplied signal of the desired band is an RF spectrum that is updated and driven at each pulse repetition period. By sequentially applying light to the surface acoustic wave electrode of the analyzer and analyzing the accumulated optical data, LJF can be detected at any time.
to be detected.

(Function) If the frequency of the above-mentioned interference wave changes, the frequency of the above-mentioned IF multiplied signal follows the frequency change of the above-mentioned interference wave and is continuous in time due to the mixing of the received signal and the local signal regarding the interference wave. It starts to change. An RF spectrum analyzer has a well-known frequency analysis function, and when an IF multiplied signal whose frequency changes continuously is applied to its surface acoustic wave electrode, it analyzes the signal level corresponding to each of these various frequency components. The light amount data is stored in each element of the light amount converting means.

Therefore, by reading out the accumulated data for each pulse repetition period and comparing the signal levels indicated by the light amount data, it is possible to accurately know the LJF at that point in time based on the frequency value corresponding to the minimum level signal. I can do it. Moreover, the detected LJF is a value obtained by observing virtually all radar frequencies over the entire period of one pulse repetition period, and has high reliability as data.

(Embodiment) FIG. 1 shows an embodiment of the frequency agility radar according to the present invention. However, although the general structure of this embodiment is the same as that shown in FIG. 5, FIG. 1 only shows the specific structure of the LJF detection circuit l, which is the main part. Furthermore, in FIG. 1, the same elements as those used in the conventional LJF detection circuit shown in FIG. 7 are designated by the same reference numerals, and redundant explanation will be omitted. Again, as an example, a case will be shown in which nine RF frequencies are used.

Now, the LJF detection circuit 18 used in this example radar
0b is the interference wave receiving antenna 1 as shown in FIG.
, RF switch 2, RF attenuator 3, RF amplifier 4
, mixer 5, B P F 6 , A/D converter 9, level memory 10 . In addition to the level comparator 1, the above BPF6
The extracted IF multiplied signal by this frequency is the RF frequency F,
~F) is received in the surface acoustic wave electrode 51, and the diffracted light based on the received IF multiplied signal of the laser light emitted from the semiconductor laser 52 is transmitted to a CCD array (nine CCDs are connected to the IF multiplied signal of the laser light). 55, which are arranged in an array in one-to-one correspondence to each Bragg diffraction angle, and the photoelectric conversion signals corresponding to the respective amounts of received light are sequentially sent to the A/D converter 9 as a video signal VDb. The IP multiplied signal frequency band obtained by mixing the output RF spectrum with the analyzer signal and the signal by the mixer 5 is the operating band frequency of this RF spectrum analyzer (the laser beam is reliably received by the CCD array 55). The interference wave FJ is
A local signal with a frequency fo that can shift the frequency band of the received signal (output of the RF amplifier 4) by the necessary amount.
A local excavator 60.6 for oscillating the LCL; an RF amplifier 70 that amplifies the local signal LCL to a level matching the level of the amplified signal by the RF amplifier 4 and supplies it to the mixer 5; and a radar reception period of the radar. A readout command signal CO1 for controlling the readout timing of the photoelectric conversion signal from the CCD array 5 and the like and a readout command signal CO1 for controlling the readout timing of the photoelectric conversion signal from the CCD array 5 in response to an A/D conversion command signal C1b for controlling the sampling timing; and a storage command signal C2b for controlling the data writing timing of the A/D conversion data Dlb to the level storage device 10 in accordance with the sampling timing; and a comparison command signal C3b for controlling the comparison start timing of the level comparator 11 corresponding to the radar reception period of the radar, respectively, to the RF spectrum analyzer 50 (CCD array 55), A/D converter 9, level storage. 10 and an LJF detection control circuit 40b that outputs output to the level comparator 11. Furthermore, this L.J.
The BPF 6 in the F detection circuit 180b has a frequency F
Since it is necessary to pass all the above-mentioned IF multiplied signals corresponding to 1 to F, the pass band is also set to a relatively wide band. In addition, the above RF spectrum analyzer (equipment) is
After the laser light emitted from the semiconductor laser 52 is parallelized by the &-IJmation lens 53, a surface acoustic wave is applied to it, and the diffracted light by the surface acoustic wave is transmitted to the CCD array 55 via the Fourier transform lens 54.
The well-known principle is that when an image is formed on a surface acoustic wave, there is a one-to-one correspondence between the image formation position and the Bragg diffraction angle of the parallel laser beam, which changes depending on the frequency of the surface acoustic wave. For details of this structure, please refer to ``Integrated optical RF
“Prototype of Spectrum Analyzer” by Mamoru Kanazawa et al.”
IEEE Spectrum DECEIVIBER
1978, pp. n-29, title: “integrated
optical spectrum analyzer
An 1mm1nent'chip'J J etc. will be referred to, and a detailed explanation will be omitted here. By the way,
The light serving as this medium is not limited to the above-mentioned laser light but can be any light having high straightness, and the light emitting means is not limited to the above-mentioned semiconductor laser 52.

FIG. 2 is a timing chart showing an example of the operation of this LJF detection circuit 180b, and below, with reference to the timing chart, an example of the operation of the radar of this embodiment will be described in detail, centering on the operation of this LJF detection circuit 180b. .

Similarly to the above, a radar signal set to one of the RF frequencies F1 to F9 corresponding to a radar master trigger signal having a pulse repetition period as shown in FIG. 2(a) is activated at the timing shown in FIG. If it is sent with
The radar transmission blanking gate signal is formatted in the manner shown in FIG. 2 fc) to determine the radar reception period of the radar device and the LJF detection circuit 180b.

Now, in response to the transmission of such a radar signal, an interference wave F is emitted from the other party, whose frequency changes at high speed over time in the range Fl to F, and this is received by the interference wave receiving antenna 1. If so, this interference wave F
The received signal of , and the local signal LCL of the frequency f0 are mixed in a mixer 5, and an IP multiplied signal whose frequency changes in accordance with the operating band frequency of the RF spectrum analyzer is extracted from the mixer 5. It will be done.

For example, the frequency of the interference wave F is 9000MH2 to 9400MH2, corresponding to the radar RF frequency F, -F.
, and the operating band frequency of the RF spectrum analyzer is centered around 600 MB2.
If it is set to zooyxH gate, that is, 400MH2 to 800MH, the above local frequency f0 is 860MHz.
0MH, and the difference from the frequency of this interference wave F is 40
An IF multiplied signal whose frequency changes in accordance with the frequency change of the interference wave F in the range from 0 MH to 800 MH is extracted from the mixer 5. The frequency of the IF multiplied signal thus extracted is analyzed by the RF spectrum analyzer I described above.

That is, each CCD arrangement position (image formation position of the laser beam) of the above-mentioned CCD array 55 A, -A.

is determined in one-to-one correspondence to nine types of IF multiplied signal frequencies (hereinafter, for convenience, these nine types of frequencies will also be referred to as F and ~F) that change in response to the above-mentioned RF frequencies F and ~F. If the IF multiplied signal is applied to the surface acoustic wave electrode 51, the signal amount by frequency during the router reception period of the same IF signal, and therefore the interference wave F by frequency during the router reception period. The signal amount is 1 compared to the amount of accumulated light received by each CCD during the router reception period of this CCD array 55.
It will be taken out in a form corresponding to 1. Now, assume that the amount of light received by CCDC number in each radar reception period, and therefore the signal amount by frequency of the interference wave FJ (Fl to FO), is as shown in FIG. 2(d). For example, regarding the first radar reception period T in terms of time, this second
The signal amount by frequency of the interference wave F shown in figure (d) is as follows: frequency rl+FB+Fa, Fs, FT, Fs, Fo
(CCD position A,,A3゜A4,Aa,Ay
, A, s, Ao), there are relatively many bonds corresponding to frequency Fa (CCD position A6) and frequency F2 (CCD position
Only a small amount exists corresponding to the OD position At), and in particular, the amount corresponding to the frequency F2 (COD position At) is extremely small. This means that during the radar reception period T, the frequency F is the LJFj to be detected here.
It means that it is being done. In order to actually detect this LJF, the LJF detection circuit 180b roughly proceeds with the following processing.

When the accumulation of frequency analysis information regarding the interference wave F to the CCD array 55 described above for each router reception period is completed, L
The JF detection control circuit 40b outputs the above-mentioned read command signal CO for reading out the stored information to the CCD array 55 at an appropriate timing, and outputs the stored information (photoelectric conversion signal) as a video signal VDb, for example, to the second The data are sequentially read out in the manner shown in FIG. This read video signal vDb is further applied to the A/D converter 9.

The A/D converter 9 sequentially A/Di-converts the video signal vDb thus applied based on the A/D conversion command signal C1b applied from the LJF detection control circuit 40b at the timing shown in FIG. 2(f). Numerical data D1b as shown in FIG. 2(g) is output.

The operation mode of the level storage device 10 and the level comparator 11 from this point onwards is similar to the operation mode of FIGS. 8(j) to (e) using the same elements of the LJF detection circuit 180a shown in FIG. 7 above. And thus the interference wave F.

If a digital signal related to the frequency analysis content is obtained, it is possible to detect the LJF for each radar reception period as described above by temporarily storing the digital signal and comparing the level content. Moreover, the LJF detected by this LJF detection circuit 180b converts all radar frequencies F, ~F, into 1
It is obtained by observing over the entire period of the pulse repetition period (more precisely, the router reception period), and its reliability as detection data is high. Of course, if LJF is detected by such a method, the above-mentioned interference wave F can be detected.

Even if the frequency or signal level of the radar changes, it will not be affected by this, and this frequency analysis can be performed accurately for each radar reception period. The data regarding the LJF thus detected is then sent to the local signal generation circuit 110 (see FIG. 5) of the radar device main body.

The radar device main body, that is, the radar side 100 described above
(See FIG. 5), the RF frequency is adjusted to a frequency that matches the detected LJF at any time, and transmission is performed each time. Therefore, the radar side 100 can effectively avoid the influence of any interference waves emitted from the other side 200 (see FIG. 5) and perform the required radar function.

In the above-described embodiment, as shown in FIG. 2, the CCD is
Interference wave F collected and accumulated in array 55.

frequency analysis information for the next radar reception period (e.g., T)
However, once the same information is accumulated in this way, the readout timing and readout speed can be set arbitrarily. The same information may be read out at a high speed within the radar reception period. According to this, the LJF is also detected more quickly, and the agility response of the transmission frequency to interference waves is also improved.

In addition, although the case where nine RF frequencies are used in the same embodiment has been described, the RF spectrum analyzer itself can be arbitrarily set for its operation center frequency, frequency bandwidth, frequency resolution, etc. Of course, any number of RF frequencies other than nine waves can be used depending on the specifications of the analyzer. Incidentally, this RF spectrum analyzer is extremely compact and lightweight, and by using the same RF spectrum analyzer, the number of local oscillators can be greatly reduced, which reduces the size of the radar equipment itself. This invention is also of great significance in terms of weight reduction.

〔Effect of the invention〕

As explained above, according to the frequency agility radar according to the present invention, accurate LJF can be detected with high reliability even in the case of interference in which the frequency of the interference wave or its signal level changes. This makes it possible to achieve the required functions as a radar under any circumstances.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing in particular the configuration of the LJF detection circuit of an embodiment of the frequency agility radar according to the present invention, FIG. 2 is a timing chart showing an example of the operation of the LJF detection circuit, and FIG. 3 is a random agility radar. 4 is a diagram showing the concept of the random agility method, and FIG. 5 is a block diagram showing the general structure of a frequency agility radar that uses the LJF agility method. , 6th
The figure is a diagram showing the concept of the LJF agility method, FIG. 7 is a block diagram showing an example of the configuration of the LJF detection circuit of a conventional frequency agility radar adopting the LJF agility method, and FIG. 3 is a timing chart showing an example of the operation of the LJF detection circuit shown in FIG. DESCRIPTION OF SYMBOLS 1... Interfering wave receiving antenna, 2... RF switch, 3... RF attenuator, 4.70... RF amplifier, 5... Mixer, 6... BPF, 9... A /D
Converter, 10... Level We memory 5.11... Level comparison 5.40b... LJF detection control circuit, ■...R
F spectrum analyzer, 60...local oscillator. Representative Patent Attorney Takahisa Kimura□,゛f-4

Claims (2)

[Claims] (1) In a frequency agility radar that detects the minimum interference frequency of interference waves emitted from the outside and variably controls the transmission frequency of the radar signal emitted from the radar device to follow the detected minimum interference frequency, a local oscillation signal is output. a mixer that mixes the local oscillation signal and a received signal regarding the interference wave; and a mixer that receives the mixed signal into a surface acoustic wave electrode and uses diffraction of light caused by the signal to generate the self-interference signal. an RF spectrum analyzer that collectively stores optical data corresponding to the frequency-specific signal level of the same signal for each pulse repetition period of the radar device, and detects the minimum interfering frequency based on the stored optical data. A frequency agility radar that is characterized by: (2) A patent in which the frequency of the local oscillation signal output from the local oscillator is set to a frequency that causes the frequency band of the received signal for the interference wave to shift to the operating band frequency of the RF spectrum analyzer through mixing by the mixer. A frequency agility radar according to claim (1).