JPH11211813A - Radar equipment - Google Patents

Abstract

(57) [Problem] To provide a radar device capable of avoiding a loss when a reflected reception signal from a high-speed moving target passes through a band-pass filter by predicting and setting a moving speed of the target in advance. It is an object. A speed setting device and a voltage controlled oscillator are provided.
And a mixer 20 for generating a Doppler signal corresponding to the target predicted speed, and performing a frequency subtraction conversion on the received signal with the Doppler signal to shift the received signal outside the band of the band-pass filter 15 into the band. However, the loss caused by the band-pass filter 15 can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar device used for detecting a target such as a ship, an aircraft, and a missile.

[0002]

2. Description of the Related Art FIG. 7 shows the basic principle of a conventional radar device. In FIG. 7, 1 is a transmitter for generating a transmission signal, 2 is a transmission / reception switch for switching the path between a transmission signal and a reception signal, and 3 is a transmission / reception switch. An antenna for transmitting a transmission signal toward a target and receiving a reflected signal from the target, 4 is a target to be detected by a radar device, 5 is a receiver for amplifying and frequency-converting a received signal, 6 is a target distance. A signal processor 7 detects the azimuth and speed, and 7 is an indicator for displaying the target distance, azimuth and speed.

In FIG. 7, a pulse-like transmission signal generated by a transmitter 1 is input to an antenna 3 via a transmission / reception switch 2 and transmitted as a radio wave from the antenna 3 toward a target 4. The pulse signal transmitted from the antenna 3 is
The light is reflected by the target 4 and received by the antenna 3 again. The received signal received by the antenna 3 is input to the receiver 5 via the transmission / reception switch 2. The received signal input to the receiver 5 is detected and turned into a video signal, which is output to the signal processor 6. The signal processor 6 detects a target distance, an azimuth, and a moving speed based on the video signal input from the receiver 5 and outputs the detected distance, direction, and moving speed to the indicator 7. The indicator 7 displays the distance, the azimuth, and the moving speed input from the signal processor 6 so that the radar operator can recognize it.

FIG. 8 shows a configuration of a conventional radar apparatus, in which 8 is a coherent oscillator for generating a source oscillation signal,
Is a modulator that performs pulse modulation, 10 is a stabilized local oscillator that generates a local oscillation signal, 11 is a mixer that performs frequency addition conversion, 12 is a power amplifier that amplifies the power of a transmission signal, 1
3 is a low-noise amplifier that amplifies the power of the received signal, 14 is a mixer that performs frequency subtraction conversion, 15 is a band-pass filter that removes signals of unnecessary frequency components, 16 is an intermediate frequency band amplifier that amplifies the power of the received signal, Reference numeral 17 denotes a phase detector for phase-detecting the received signal and converting it into a video signal.

In FIG. 8, a coherent oscillator 8 generates a source oscillation signal having a frequency equal to the intermediate frequency, and
Output to The source oscillation signal input to the modulator 9 is pulse-modulated and input to the mixer 11 as an intermediate frequency transmission signal. The stabilized local oscillator 10 generates a local oscillation signal having a frequency corresponding to the difference between the transmission frequency and the intermediate frequency, and
Output to The mixer 11 performs frequency addition conversion of the intermediate frequency transmission signal input from the modulator 8 with a local oscillation signal input from the stabilized local oscillator 10, generates a transmission signal, and outputs the transmission signal to the power amplifier 12. The transmission signal input to the power amplifier 12 is power-amplified by a preset amplification factor, and then transmitted from the antenna 3 via the transmission / reception switch 2. On the other hand, a received signal received by the antenna 3 and passed through the transmission / reception switch 2 is input to the low-noise amplifier 13 and power-amplified by a preset amplification factor.
4 is output. The mixer 14 performs frequency subtraction conversion of the received signal input from the low noise amplifier 13 with the local oscillation signal input from the stabilized local oscillator 10 to generate an intermediate frequency reception signal, and outputs the intermediate frequency reception signal to the bandpass filter 15. The intermediate frequency reception signal input to the band pass filter 15 is output to the intermediate frequency band amplifier 16 after removing unnecessary frequency component signals. The intermediate frequency reception signal input to the intermediate frequency band amplifier 16 is power-amplified by a preset amplification factor and output to the phase detector 17. Phase detector 17
Represents the signal input from the intermediate frequency band amplifier 16 as a source oscillation signal input from the coherent oscillator 8 by I (In
-Phase) video signal and Q (Quadratur)
e) The video signal is phase-detected and output to the signal processor 6.
The signal processor 6 detects a target distance, an azimuth, and a moving speed based on the I video signal and the Q video signal input from the phase detector 17 and outputs them to the indicator 7. The indicator 7 displays the target distance, azimuth, and moving speed input from the signal processor 6 so that the radar operator can recognize it.

Here, the pass band width B of the band pass filter is uniquely determined if a pulse width τ is given at the stage of designing the radar apparatus. In a general radar device, the pass bandwidth B is determined by the equation given by Equation 1 so that the signal-to-noise ratio is maximized.

[0007]

(Equation 1)

[0008]

By the way, in the conventional radar apparatus constructed and operated as described above, FIG.
As shown in the figure, when the target is moving at high speed and the Doppler frequency added to the received signal is out of the pass band of the band-pass filter, the received signal is suppressed by the frequency characteristic of the band-pass filter. This causes a problem that the distance, direction and moving speed of the target cannot be detected.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a signal of a voltage proportional to a set value is generated by an operator of a radar apparatus arbitrarily setting a target speed. A speed setting device, a voltage-controlled oscillator that generates a Doppler signal at a frequency proportional to the voltage of the output signal of the speed setting device, and a mixer that frequency-subtracts and converts the received signal with the Doppler signal. By setting the predicted target speed and subtracting the Doppler frequency corresponding to the set speed from the received signal,
By shifting the reception signal frequency into the pass band of the band-pass filter, it is intended to avoid a loss when the reception signal passes through the band-pass filter.

[0010]

A radar device according to a first aspect of the present invention is a speed setting device capable of generating a voltage signal proportional to a set value by an operator of the radar device arbitrarily setting a target speed. A voltage-controlled oscillator that generates a Doppler signal at a frequency proportional to the voltage of the output signal of the speed setting device, and generates an intermediate frequency reception signal shifted by the Doppler frequency by performing frequency subtraction conversion on the intermediate frequency reception signal with the Doppler signal. An operator sets a target speed predicted in advance in a speed setting device, generates a signal of a Doppler frequency corresponding to the set speed by a voltage controlled oscillator, and generates an intermediate frequency reception signal with the Doppler signal. By performing frequency subtraction conversion, the frequency of the received signal is shifted into the pass band of the band-pass filter, and the received signal passes through the band-pass filter. It is an attempt to obtain the ability to avoid the loss of time that.

A radar apparatus according to a second aspect of the present invention provides a speed setting device capable of generating a voltage signal proportional to a set value by an operator of the radar apparatus arbitrarily setting a target speed; A voltage-controlled oscillator that generates a Doppler signal at a frequency proportional to the voltage of the output signal of the setting device; and a mixer that generates a local signal shifted by the Doppler frequency by performing frequency subtraction conversion of the local signal with the Doppler signal. By setting a target speed predicted in advance to a speed setting device, a signal of a Doppler frequency corresponding to the set speed is generated by a voltage controlled oscillator, and a local subtraction signal is subjected to frequency subtraction conversion by the Doppler signal, It is intended to obtain a function of shifting the reception signal frequency into a pass band of the band-pass filter and avoiding a loss when the reception signal passes through the band-pass filter. It is.

A radar apparatus according to a third aspect of the present invention is a speed setting device capable of generating a voltage signal in proportion to a set value by an operator of the radar apparatus arbitrarily setting a target speed; A voltage-controlled oscillator that generates a Doppler signal at a frequency proportional to the voltage of the output signal of the setting device; a mixer that generates a reception signal shifted by a Doppler frequency by performing frequency subtraction conversion on an intermediate frequency reception signal with the Doppler signal; The signal is provided with a mixer that performs frequency addition conversion of the intermediate frequency reception signal after passing through the band-pass filter, and the operator sets a target speed predicted in advance to the speed setting device, and outputs a signal of the Doppler frequency according to the set speed. The frequency of the received signal is reduced by performing a frequency subtraction conversion of the intermediate frequency received signal generated by the voltage controlled oscillator with the Doppler signal. After being shifted into the pass band of the over-filter and passing through the band-pass filter, the intermediate frequency reception signal is frequency-added again with the Doppler signal to avoid a loss when the reception signal passes through the band-pass filter, It is intended to obtain a function of restoring the Doppler frequency added to the received signal by moving the target.

A radar apparatus according to a fourth aspect of the present invention is a radar setter capable of generating a voltage signal proportional to a set value by an operator of the radar apparatus arbitrarily setting a target speed; A voltage-controlled oscillator that generates a Doppler signal at a frequency proportional to the voltage of the output signal of the setting device; a mixer that generates a local oscillation signal shifted by the Doppler frequency by performing frequency subtraction conversion of the local oscillation signal with the Doppler signal; The signal is provided with a mixer that performs frequency addition conversion of the source oscillation signal, an operator sets a predicted target speed in a speed setting device, and generates a signal of a Doppler frequency according to the set speed by a voltage controlled oscillator, By performing frequency subtraction conversion of the local oscillation signal with the Doppler signal, the reception signal frequency is shifted into the pass band of the band-pass filter,
After passing through the band-pass filter, phase detection is performed with the source oscillation signal frequency-added and converted by the Doppler signal to avoid loss when the received signal passes through the band-pass filter and to move the target signal so that the target moves. The purpose of the present invention is to obtain a function of restoring the Doppler frequency added to.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a block diagram showing a first embodiment of the present invention.
7 is the same as the prior art, 18 is a speed setting device for setting a target speed by a radar operator, 19 is a voltage controlled oscillator that generates a signal having a frequency proportional to the input voltage, and 20 is a mixer that performs frequency subtraction conversion. is there.

In the configuration as shown in FIG. 1, when the Doppler frequency added to the reflected reception signal from the target is out of the band of the band-pass filter 8, the radar operator changes the target speed predicted in advance to the speed. Set in the setting device 18. The speed setter 18 generates a signal of a voltage proportional to the set value and outputs the signal to the voltage controlled oscillator 19. The voltage controlled oscillator 19 generates a Doppler signal having a frequency proportional to the input signal voltage and outputs the signal to the mixer 20. The mixer 20 performs frequency subtraction conversion on the received signal input from the low noise amplifier 13 with the Doppler signal input from the voltage controlled oscillator 19 and outputs the signal to the bandpass filter 15.

FIG. 2 shows a frequency characteristic of a received signal in the radar apparatus according to the first embodiment. According to FIG. 2, the received signal outside the band of the band-pass filter 15 is shifted into the band by the frequency subtraction conversion of the Doppler frequency corresponding to the speed set by the operator by the mixer 20, and is shifted into the band. The signal can pass through the band-pass filter 15 without loss due to the pass band characteristics.

Embodiment 2 FIG. FIG. 3 is a block diagram showing a second embodiment of the present invention. In FIG. 3, reference numerals 1 to 17 denote the same components as those in the conventional technique, reference numeral 18 denotes a speed setting device by which a radar operator sets a target speed, and reference numeral 19 denotes an input. A voltage controlled oscillator 21 generates a signal having a frequency proportional to the voltage, and a mixer 21 performs frequency subtraction conversion.

In the configuration as shown in FIG. 3, when the Doppler frequency added to the reflected signal received from the target is out of the band of the band-pass filter 15, the radar operator changes the target speed predicted in advance to the speed. Set in the setting device 18. The speed setter 18 generates a signal of a voltage proportional to the set value and outputs the signal to the voltage controlled oscillator 19. The voltage controlled oscillator 19 generates a Doppler signal having a frequency proportional to the input signal voltage and outputs the signal to the mixer 21. The mixer 21 performs frequency subtraction conversion on the local oscillation signal input from the stabilized local oscillator 21 based on the Doppler signal input from the voltage controlled oscillator 19 and outputs the signal to the mixer 14. The mixer 14 performs frequency subtraction conversion of the received signal into an intermediate frequency received signal shifted by the Doppler frequency based on the local oscillation signal input from the mixer 21.

The frequency characteristics of the received signal are the same as in FIG. 2 in the first embodiment. According to FIG. 2, the reception signal outside the band of the band-pass filter 15 is shifted by the mixer 14 by the Doppler frequency corresponding to the speed set by the operator and is shifted into the band by frequency subtraction conversion to the intermediate frequency. , Can pass through the band-pass filter 15 without loss due to the pass-band characteristics of the band-pass filter 15.

Embodiment 3 FIG. 4 is a block diagram showing a third embodiment of the present invention. In FIG. 4, 1 to 17 are the same as those in the conventional art, 18 is a speed setting device for setting a target speed by a radar operator, and 19 is an input. A voltage-controlled oscillator that generates a signal having a frequency proportional to the voltage, a mixer 20 that performs frequency subtraction conversion, and a mixer 22 that performs frequency addition conversion.

In the configuration shown in FIG. 4, when the Doppler frequency added to the reflected reception signal from the target is out of the band of the band-pass filter 15, the radar operator
A target speed predicted in advance is set in the speed setting device 18. The speed setter 18 generates a signal of a voltage proportional to the set value and outputs the signal to the voltage controlled oscillator 19. The voltage controlled oscillator 19 generates a Doppler signal having a frequency proportional to the input signal voltage, and outputs it to the mixer 20 and the mixer 22. The mixer 20 performs frequency subtraction conversion on the received signal input from the low noise amplifier 13 with the Doppler signal input from the voltage controlled oscillator 19 and outputs the signal to the bandpass filter 15. The reception signal from which the unnecessary frequency signal has been removed by the band-pass filter 15 is output to the mixer 22 and the voltage-controlled oscillator 1
9 is frequency-added and converted by the Doppler signal input from.

FIG. 5 shows a frequency characteristic of a received signal in the radar apparatus according to the third embodiment. According to FIG. 5, the reception signal outside the band of the band-pass filter 15 is frequency-inverted and converted by the mixer 20 by the Doppler frequency corresponding to the speed set by the operator, so that the received signal is shifted into the band and the band-pass filter 15 is shifted. After passing through, the signal is frequency-added and converted by the Doppler frequency in the mixer 22, so that the signal passes through the band-pass filter 15 without loss due to the pass-band characteristics of the band-pass filter 15, and the Doppler frequency added to the received signal is restored. be able to.

Embodiment 4 FIG. 6 is a block diagram showing a fourth embodiment of the present invention. In FIG. 6, reference numerals 1 to 17 denote the same components as those of the above-described prior art, 18 denotes a speed setting device for setting a target speed by a radar operator, and 19 denotes an input. A voltage-controlled oscillator for generating a signal having a frequency proportional to the voltage, a mixer 21 for frequency subtraction conversion, and a mixer 22 for frequency addition conversion.

In the configuration as shown in FIG. 6, when the Doppler frequency added to the reflected reception signal from the target is out of the band of the band-pass filter 15, the radar operator changes the speed of the target predicted in advance to the speed. Set in the setting device 18. The speed setter 18 generates a signal of a voltage proportional to the set value and outputs the signal to the voltage controlled oscillator 19. The voltage controlled oscillator 19 generates a Doppler signal having a frequency proportional to the input signal voltage, and outputs it to the mixer 21 and the mixer 23.
The mixer 21 performs frequency subtraction conversion of the local oscillation signal input from the stabilized local oscillator 21 based on the Doppler signal input from the voltage controlled oscillator 19 and outputs the result to the mixer 14. On the other hand, the mixer 23 performs frequency addition conversion of the source oscillation signal input from the coherent oscillator 8 based on the Doppler signal input from the voltage controlled oscillator 19 and outputs the resultant signal to the phase detector 17. The mixer 14 performs frequency subtraction conversion of the received signal into an intermediate frequency received signal shifted by the Doppler frequency based on the local oscillation signal input from the mixer 21, and performs the band-pass filter 1.
Output to 5 The intermediate frequency reception signal that has passed through the band pass filter 15 is amplified by an intermediate frequency band amplifier 16 and then output to a phase detector 17. The phase detector 17 detects the intermediate frequency reception signal from the source oscillation signal input from the mixer 23 into a video signal shifted by the Doppler frequency, and outputs the video signal to the signal processor 6.

The frequency characteristics of the received signal are the same as in FIG. 5 in the third embodiment. According to FIG. 5, the received signal outside the band of the band-pass filter 15 is shifted by the mixer 14 by the Doppler frequency corresponding to the speed set by the operator and is shifted into the band by frequency subtraction conversion to the intermediate frequency. After passing through the band-pass filter 15, the signal is frequency-added and converted by the phase detector 17 by the Doppler frequency, so that the signal passes through the band-pass filter 15 without loss due to the pass-band characteristics of the band-pass filter 15 and The added Doppler frequency can be restored.

[0026]

According to the first aspect of the present invention, a speed setter capable of generating a voltage signal proportional to a set value by an operator of the radar apparatus arbitrarily setting a target speed, and the speed setting device A voltage-controlled oscillator that generates a Doppler signal at a frequency proportional to the voltage of the output signal of the device, and a mixer that generates an intermediate frequency reception signal shifted by the Doppler frequency by performing frequency subtraction conversion on the intermediate frequency reception signal with the Doppler signal, An operator sets a predicted target speed in a speed setting device, generates a signal of a Doppler frequency according to the set speed by a voltage controlled oscillator, and performs a frequency subtraction conversion of an intermediate frequency reception signal with the Doppler signal. Function to shift the frequency of the received signal into the pass band of the band-pass filter to avoid loss when the received signal passes through the band-pass filter. There is an effect that can be obtained.

According to the second aspect of the present invention, a speed setter capable of generating a voltage signal proportional to a set value by an operator of the radar apparatus arbitrarily setting a target speed;
A voltage-controlled oscillator that generates a Doppler signal at a frequency proportional to the voltage of the output signal of the speed setting device; anda mixer that generates a local signal that is shifted by the Doppler frequency by performing frequency subtraction conversion on the local signal with the Doppler signal. The operator sets the predicted target speed in advance in the speed setting device,
A Doppler frequency signal corresponding to the set speed is generated by a voltage-controlled oscillator, and the local signal is frequency-subtracted and converted by the Doppler signal to shift the reception signal frequency into the pass band of the band-pass filter. There is an effect that a function of avoiding loss when a signal passes through a band-pass filter can be obtained.

According to the third aspect of the present invention, a speed setter capable of generating a signal of a voltage proportional to a set value by an operator of the radar apparatus arbitrarily setting a target speed;
A voltage-controlled oscillator that generates a Doppler signal at a frequency proportional to the voltage of the output signal of the speed setting device, and a mixer that generates a reception signal shifted by the Doppler frequency by performing frequency subtraction conversion on an intermediate frequency reception signal with the Doppler signal. The Doppler signal includes a mixer that performs frequency addition conversion of the intermediate frequency reception signal after passing through the band-pass filter, and an operator sets a predicted target speed in advance to a speed setting device,
A signal having a Doppler frequency corresponding to the set speed is generated by a voltage-controlled oscillator, and the intermediate frequency reception signal is subjected to frequency subtraction conversion with the Doppler signal, thereby shifting the reception signal frequency into a pass band of a band-pass filter, After passing through the band-pass filter, the intermediate frequency reception signal in the Doppler signal is frequency-added again to avoid loss when the reception signal passes through the band-pass filter, and is added to the reception signal by moving the target. There is an effect that a function of restoring the Doppler frequency can be obtained.

According to the fourth invention, a speed setter capable of generating a voltage signal proportional to a set value by an operator of the radar apparatus arbitrarily setting a target speed,
A voltage-controlled oscillator that generates a Doppler signal at a frequency proportional to the voltage of the output signal of the speed setting device, and a mixer that generates a local oscillation signal shifted by the Doppler frequency by performing frequency subtraction conversion on the local oscillation signal with the Doppler signal. A mixer for performing frequency addition conversion of the source oscillation signal with the Doppler signal,
The operator sets a target speed predicted in advance to the speed setting device, generates a signal of a Doppler frequency according to the set speed by a voltage controlled oscillator, and performs frequency subtraction conversion of a local oscillation signal with the Doppler signal. The received signal frequency is shifted into the pass band of the band-pass filter, and after passing through the band-pass filter, phase detection is performed with the source oscillation signal that has been frequency-added and converted by the Doppler signal. There is an effect that a function of restoring the Doppler frequency added to the received signal by moving the target can be obtained while avoiding the loss.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of a radar apparatus according to the present invention.

FIG. 2 is a diagram illustrating frequency characteristics of a received signal of the radar apparatus according to the first embodiment of the present invention;

FIG. 3 is a diagram showing a second embodiment of the radar apparatus according to the present invention;

FIG. 4 is a diagram showing a third embodiment of the radar device according to the present invention;

FIG. 5 is a diagram illustrating a frequency characteristic of a received signal in a radar apparatus according to Embodiment 3 of the present invention;

FIG. 6 is a diagram showing a fourth embodiment of the radar apparatus according to the present invention;

FIG. 7 is a diagram illustrating a basic principle of a conventional radar device.

FIG. 8 is a diagram showing a configuration of a conventional radar device.

FIG. 9 is a diagram illustrating frequency characteristics of a received signal of a conventional radar device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Transmitter, 2 transmission / reception switch, 3 antennas, 4 targets, 5 receivers, 6 signal processors, 7 indicators, 8 coherent oscillators, 9 modulators, 10 stabilized local oscillators, 11 mixers, 12 power amplifiers, 13 Low noise amplifier, 14 mixers, 15 bandpass filters, 16
Intermediate frequency band amplifier, 17 phase detector, 18 speed setting device, 19 voltage controlled oscillator, 20 mixers, 21 mixers, 22 mixers, 23 mixers.

Claims (4)

[Claims] 1. A radar device capable of transmitting a pulse signal having a constant repetition period toward a target, receiving a reflected signal from the target, and detecting a distance and an azimuth to the target, and a moving speed of the target. A coherent oscillator for generating a source oscillation signal of the transmission signal; a modulator for pulse-modulating the source oscillation signal generated by the coherent oscillator to generate an intermediate frequency transmission signal; and a frequency difference between the transmission signal and the intermediate frequency signal. A stabilized local oscillator that generates a local signal at a frequency, a mixer that performs frequency addition conversion of the intermediate frequency transmission signal with the local signal to generate a transmission signal, and a reception signal that is reflected from a target and is frequency-converted by the local signal. A mixer that performs subtraction conversion to generate an intermediate frequency reception signal, and an operator of the radar device arbitrarily sets a target speed and generates a signal having a voltage proportional to the set value. A speed setting device that can produce
A voltage controlled oscillator for generating a Doppler signal at a frequency proportional to the voltage of the output signal of the speed setting device, a mixer for performing frequency subtraction conversion of the intermediate frequency reception signal with a Doppler signal, and an intermediate frequency reception shifted by the Doppler frequency A radar apparatus comprising: a band-pass filter that removes an unnecessary frequency component signal from a signal. 2. A radar device capable of transmitting a pulse signal having a constant repetition period toward a target, receiving a reflected signal from the target, and detecting a distance and an azimuth to the target, and a moving speed of the target. A coherent oscillator for generating a source oscillation signal of the transmission signal; a modulator for pulse-modulating the source oscillation signal generated by the coherent oscillator to generate an intermediate frequency transmission signal; and a frequency difference between the transmission signal and the intermediate frequency signal. A stabilized local oscillator that generates a local oscillation signal at a frequency, a mixer that generates a transmission signal by performing frequency addition conversion of the intermediate frequency transmission signal with the local oscillation signal, and an operator of the radar device arbitrarily sets a target speed; A speed setting device capable of generating a signal of a voltage proportional to the set value; and a Doppler signal generated at a frequency proportional to the voltage of the output signal of the speed setting device. A voltage-controlled oscillator, a mixer for performing frequency subtraction conversion of the local oscillation signal with a Doppler signal, and a frequency subtraction conversion of a reception signal reflected from a target with a local oscillation signal shifted by the Doppler frequency to convert an intermediate frequency reception signal. A radar apparatus comprising: a mixer to be generated; and a band-pass filter that removes an unnecessary frequency component signal from the intermediate frequency reception signal shifted by the Doppler frequency. 3. The radar apparatus according to claim 1, further comprising a mixer that performs frequency addition conversion of a signal output from the band-pass filter with a Doppler signal output from the voltage controlled oscillator. 4. A mixer that performs frequency addition conversion of a source oscillation signal output from a coherent oscillator with a Doppler signal,
3. The radar according to claim 2, further comprising: a phase detector for detecting a phase of the intermediate frequency reception signal shifted by the Doppler frequency output from the band-pass filter by using a source oscillation signal shifted by the Doppler frequency. apparatus.