JPH0471473B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention irradiates radio waves to a target such as an aircraft, a flying object, or a vehicle, and uses the reflected waves reflected from the target as a medium to generate radio waves relative to the target. In pulse modulation type tracking radar that tracks distance and relative speed, it enables narrow band reception of reflected waves from the target.
This invention relates to the improvement of a tracking radar that automatically tracks the relative distance and velocity to a target.

(Summary of the Invention) The present invention is a pulse modulation method that irradiates radio waves to a target such as an aircraft, a flying object, or a vehicle, and uses the reflected waves reflected from the target as a medium to track the relative distance and relative speed to the target. In this type of tracking radar, the video signals of the distance tracking system and Doppler frequency tracking system of the tracking radar are converted into digital signals, and then fast Fourier transformed, and the output is used to
By simultaneously performing distance signal discrimination and Doppler frequency signal discrimination processing, the ability to discriminate between unwanted waves and target signals is improved, thereby improving the ability of tracking radar in environments with high electronic interference.

(Prior Art) A conventional example of a tracking radar will be described using the conventional example shown in FIGS. 2 and 3.

The transmission source output of the output of the transmission source 13 is phase modulated in the third phase modulator 14 and becomes the third phase modulator output. The third phase modulator output is pulse-modulated by the third pulse modulator 15 and becomes the third pulse modulator output. The output of the third pulse modulator is the power amplifier 1
6, the signal is amplified by the transmitter/receiver switch 2, and is irradiated as a transmission wave toward the target by the antenna 1.

The reflected wave from the target is received by the antenna 1 and branched to the first mixer 3 and the second mixer 4, respectively, and the first pulse modulator output and the second pulse modulation obtained from the first pulse modulator 22 are transmitted. The outputs of the second pulse modulator obtained from the device 21 are frequency-converted into the outputs of the first mixer and the outputs of the second mixer, respectively. In FIG. 3, 27 is a modulation code of the first phase modulator 20, and 28 is a modulation code of the second phase modulator 19.
is the modulation code of the second phase modulator, and the code 2 of the second phase modulator is
8 is configured such that the code 27 of the first phase modulator 19 is switched between 0 and π with a width of 1/2 by the inversion bit generator 17 and the first switch 18. The code 27 is the same as the code of the third phase modulator 14, and is generated at a distance relative to the target. First phase modulator 2
Since the outputs of the zero and second phase modulators 19 are as described above, the amplitudes of the outputs of the first mixer 3 and second mixer 4, which mix these signals and the reflected signal from the target, are the same as the target. 29, respectively, depending on the relative distance from
It will be like 30.

The output of the first mixer 3 is amplified by the first intermediate frequency amplifier 23 and becomes the first intermediate frequency amplifier output, which becomes a reference signal for the synchronous detector 25.

The output of the second mixer 4 is amplified by the second intermediate frequency amplifier 24 to become the second intermediate frequency amplifier output, and is synchronously detected by the synchronous detector 25 and output from the synchronous detector 25 to detect the relative distance between the target and the target. A distance signal containing information is obtained.

The distance signal output from the synchronous detector is input to the delay oscillator 12. The delay oscillator 12 outputs a delay pulse with a delay amount proportional to the distance signal. This delayed oscillator output is transmitted to the first phase modulator 20 and the first switch 1.
8 and an inversion bit generator 17, respectively. The delay oscillator output becomes the inverted bit generator output, and the first switch 18 selects the first half of each bit as the delayed oscillator output and the second half as the inverted bit generator output, and becomes the first switch output.

The first intermediate frequency amplifier output, which is the output of the first intermediate frequency amplifier 23, is subjected to frequency discrimination by the Doppler discriminator 26, and becomes a Doppler frequency signal containing relative velocity information with respect to the target. The Doppler shift mixing corrector 11 uses the Doppler frequency signal that is the output of the Doppler discriminator 26 to
The output of the transmitting source, which is the output of

The first phase modulator 20 phase-modulates the delayed oscillator output with the Doppler shift mixing corrector output to create a first phase modulator output. The first phase modulator output is pulse modulated by the first pulse modulator 22 and becomes the first pulse modulator output. The output of the first switch is phase modulated by the second phase modulator 19 based on the output of the Doppler shift mixing corrector. The second phase modulator output is pulse modulated by the second pulse modulator 21 and becomes the second pulse modulator output.

(Problem to be solved by the invention) By the way, the conventional tracking radar is configured as described above, and distance tracking and Doppler frequency tracking are performed using separate circuits (distance tracking includes a synchronous detector, a delay oscillator, etc.) Tracking of the Doppler frequency is performed by the circuit section (including the Doppler discriminator, Doppler shift mixture corrector, etc.), so if there is interference with each tracking, one of the tracking will be lost and the received signal cannot be tracked, resulting in interference. There was a problem with being weak.

The present invention has been made in order to solve the above-mentioned problems, and is resistant to interference by simultaneously tracking distance and Doppler frequency, and is capable of narrowband reception using fast Fourier transform. The purpose is to obtain radar.

(Means for solving the problem) The tracking radar according to the present invention samples a signal obtained by phase demodulating a received input, converts it into a digital signal, performs fast Fourier transform, and outputs the fast Fourier transform output. The above-mentioned problems are solved by using the above-described method to discriminate between distance signals and Doppler frequencies.

(Function) In the present invention, distance signal discrimination and Doppler frequency discrimination can be performed simultaneously by using fast Fourier transform. Therefore, even if one discrimination is disturbed by interference, if the other discrimination is normal, tracking can be continued and narrowband reception is also possible.

(Example) An example of the present invention will be described below with reference to FIG.

The transmission source output, which is the output of the transmission source 13, is phase modulated by the third phase modulator 14 and becomes a third phase modulated wave output. The third phase modulated wave output is pulse modulated by the third pulse modulator 15, the third modulator output is amplified by the power amplifier 16, and is irradiated to the target as a transmission wave from the antenna 1 through the transmitter/receiver switcher 2. be done.

The reception input, which is a reflected wave from the target, passes through the transmitter/receiver switch 2 and is branched to a first mixer 3 and a second mixer 4, respectively, and outputs a first pulse modulator output and a second pulse modulator output. They are used as the first mixer output and the second mixer output, respectively.

The first mixer output and the second mixer output are each sampled by a sampler 5 and converted into a digital signal by an A/D converter 6. A predetermined number of the respective signals converted into digital signals are collected, fast Fourier transformed by a Fourier transformer 7, and converted into data on the frequency axis. The Fourier transformer 7 receives a signal corresponding to the frequency difference between the target and the output of the Doppler shift mixing corrector 11, and converts the input signal into data on the frequency axis obtained by Fourier transform.

The discriminator 8 uses the output of this fast Fourier transform to search, detect, capture, and track the distance and Doppler frequency of the received signal, and outputs a distance signal containing relative distance information between the target and the target. Obtain a Doppler signal output containing relative velocity information between. Regarding the distance of the received signal, the distance of the received signal is controlled by changing the delay amount of the delay oscillator 12 using the relationship between the relative distance of the output 29 of the first mixer 3 and the output amplitude. Performs detection and capture. Regarding distance tracking, the relationship between the relative distance and output amplitude of the output 30 of the second mixer 4 is used to
The amount of delay of the delay oscillator 12 is controlled so that the amplitude of the output 30 of the second mixer 4 becomes 0 when the amplitude of the output 29 of the mixer 3 is equal to or higher than a predetermined level.

Regarding the Doppler frequency, the output 29 of the first mixer 3 is Fourier-transformed and converted into data on the frequency axis, and the reflected wave from the target that has received a Doppler shift and the output of the Doppler shift mixing corrector 11 are calculated. The oscillation frequency of the Doppler shift mixing corrector 11 is controlled so that the frequency difference becomes a predetermined frequency. In addition, to search for, detect, and capture the Doppler frequency, the oscillation frequency of the Doppler shift mixing corrector 11 is changed in a predetermined pattern, and the output of the first mixer 3 is Fourier-transformed to obtain a signal that exceeds a predetermined threshold. It has become capable of detecting and capturing objects.

In this way, the Fourier transformer 7 and the discriminator 8 simultaneously track the distance and the Doppler frequency, so even if there is interference in the distance information, the Doppler frequency will not deviate from the output of the Fourier transformer 7. If it can be detected, the received signal can be tracked, and conversely, even if there is interference at the Doppler frequency, if the amplitude levels of the output of the first mixer 3 and the output of the second mixer 4 can be detected, the received signal can be tracked. It is possible.

The distance signal output (signal for timing control) obtained by the discriminator 8 is converted into an analog signal by the first D/A converter, and the Doppler signal output is converted into an analog signal by the first D/A converter.
The signal is converted into an analog signal by the 2D/A converter 10.

The delay oscillator 12 uses the distance signal, which is the output of the first D/A converter, as a control signal and changes the amount of delay to create a delay oscillator output. This delay oscillator output is transmitted to the first phase modulator 20 and the first switch 1.
8 and an inversion bit generator 17, respectively. The delayed oscillator output is bit-inverted by the inverting bit generator 17 to become the inverted bit generator output,
In the first switch 18, the first half of each bit is selected as the delayed oscillator output, and the second half is selected as the inverted bit generator output, and becomes the first switch output.

The Doppler shift mixing corrector 11 is a second D/A
Using the Doppler signal output from the converter as a control signal, the transmitting source output is modulated to create the Doppler shift mixing corrector output.

The first phase modulator 20 phase-modulates the delayed oscillator output with the Doppler shift mixing corrector output to create a first phase modulator output. The first phase modulator output is pulse modulated by the first pulse modulator 22 and becomes the first pulse modulator output.

The output of the first switch is phase-modulated by the second phase modulator 19 using the output of the Doppler shift mixing corrector, and the output of the second phase modulator is pulse-modulated by the second pulse modulator 21 to become the output of the second pulse modulator.

(Effects of the Invention) As explained above, according to the tracking radar of the present invention, by using fast Fourier transform, distance tracking and speed tracking can be performed simultaneously. It is possible to perform narrow band reception determined by , and it is possible to lower the minimum reception sensitivity. It also has the effect of being able to continue tracking the received signal even if there is interference in either the distance or the Doppler frequency.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a tracking radar according to the present invention, FIG. 2 is a block diagram showing a conventional tracking radar, and FIG. 3 is an explanatory diagram of the operation of the conventional tracking radar. 1... Antenna, 2... Transmission/reception switch, 3... First mixer, 4... Second mixer, 5... Sampler, 6... A/D
Converter, 7... Fourier transformer, 8... Discriminator, 9...
1st D/A converter, 10... 2nd D/A converter, 11
... Doppler shift mixing corrector, 12... Delay oscillator, 13... Transmission source, 14... Third phase modulator, 15
...Third pulse modulator, 16...Power amplifier, 17...
Inversion bit generator, 18...first switch, 19...second phase modulator, 20...first phase modulator, 21...second pulse modulator, 22...first pulse modulator, 23
...first intermediate frequency amplifier, 24...second intermediate frequency amplifier, 25...synchronous detector, 26...Doppler discriminator.

Claims (1)

[Claims] 1 a transmission source, a first phase modulator for phase modulating the output of this transmission source, a first pulse modulator for further pulse modulation, and power for amplifying the output of this first pulse modulator An amplifier, a transmission/reception switch, an antenna that receives the output of the power amplifier via the transmission/reception switch and irradiates a transmission wave, a delay oscillator, an inversion bit generator that inverts bits of the output of the delay oscillator, and the front half of the bit. a switch for making the output of the delay oscillator and the latter half the output of the bit inverter, and second and third phase modulation for respectively phase modulating the switch and the output of the delay oscillator. a Doppler shift mixing corrector that performs Doppler shift correction on the second and third phase modulators;
second and third pulse modulators for pulse modulating the outputs of the phase modulators, respectively;
first and second mixers for mixing the output of the third pulse modulator and the received signal received by the antenna and passed through the transmitter/receiver; a sampler for sampling the output of the mixer; An A/D converter that converts the output into a digital signal, this A/D
A Fourier transformer that performs fast Fourier transform on the output of the converter, a discriminator that uses the output of this Fourier transformer to discriminate between distance and Doppler frequency, and a distance signal that is output from this discriminator and includes information on the relative distance to the target. a first D/A converter that converts the signal into an analog signal and outputs the analog signal to the delay oscillator, and converts a Doppler signal containing relative speed information between the target and the target output from the discriminator into an analog signal. , a second D/A converter that outputs the analog signal to the Doppler shift mixing corrector, demodulates the received signal using fast Fourier transform, and uses the output of the first D/A converter to demodulate the received signal. , having a function of simultaneously performing distance tracking and Doppler tracking by controlling the delay amount of the delay oscillator and controlling the output of the Doppler mixing corrector using the output of the second D/A converter. Features tracking radar.