JPH0377951B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Field of technology to which the present invention pertains The present invention is directed to irradiating electromagnetic waves or light onto targets such as aircraft, flying objects, or vehicles, and detecting electromagnetic waves or light reflected from those targets. In continuous wave and pulse distance tracking radars that use light as a medium to track the distance to a target, the emitted electromagnetic waves or light are transmitted in a highly secretive broadband modulation format, and the reflected waves from the target are received in a narrow band. This invention relates to the improvement of a distance tracking radar that automatically tracks the distance from the distance tracking radar to a target.

(2) Background of the present invention Conventional distance measuring radars can be roughly divided into pulse type and continuous wave type. In continuous wave type, the electromagnetic waves that the radar itself irradiates to the target are always transmitted to the receiver within the radar itself. Because of this, it was difficult to make the receiver highly sensitive. For this reason, pulse type distance measuring radars are relatively often used.

Due to the pulse modulation format used in pulse type radars, the receiver must have a wide bandwidth, and the sensitivity is not very good due to the large amount of receiver noise. Furthermore, because the receiver bandwidth is wide, it is vulnerable to radio wave jamming by the target side, which is a serious drawback.

Various methods have been proposed for radar technology to counter radio interference, but the frequency and format of the radio waves emitted by the radar itself towards the target are such that the target side cannot detect the electromagnetic waves. If it can be irradiated, it will be one of the fundamental solutions to counter radio interference.

For the reasons mentioned above, one direction in which distance measuring radars should move in the future is: (a) If the sensitivity of the receiver deteriorates due to leakage of transmitted output into the receiver, a pulse method should be adopted. By switching between transmission and reception, and by making the pulse repetition frequency variable, the transmission pulse and the reception reflected wave pulse are prevented from matching, thereby preventing a drop in reception power. (3) Improving the anti-jamming ability by reducing the bandwidth of the receiver as much as possible, and also increasing the sensitivity. Simultaneous realization of these is strongly desired.

(3) Prior art and its general problems A conventional example of a distance tracking radar will be explained using the block diagram of FIG. 1 and the time chart of FIG. 2.

The reference pulse generator output 29, which is the output of the reference pulse generator 57, is waveform-shaped into a pulse having a predetermined pulse width by the shaping circuit 58, and becomes the reference pulse 23.

The source output 15 produced by the transmit source 59 is pulse modulated by a pulse modulator 60 to which the reference pulse 23 is applied, resulting in a pulse modulator output 24.
is amplified by the power amplifier 61 to become the power amplifier output 17, which is transmitted to the target as the transmission output 18 by the transmission antenna 50.

The reflected wave from the target is delayed by T (seconds) after transmission, and is received by the receiving antenna 51 as receiving input 1, and becomes receiving antenna output 2. Local oscillator output 13 produced by local oscillator 56 is supplied to mixer 52
is mixed with receiving antenna output 2 by
The signal is amplified by the intermediate wave amplifier output 37, which is amplitude detected by the amplitude detector 54, and becomes the amplitude detector output 10. The display 55 displays the amplitude detector output 10 based on the reference pulse 23.
By displaying the obtained distance calculation output 26, the distance from the radar to the target can be determined.

(4) Specific problems with conventional technology Tracking radars that search for, detect, and track a target not only have the ability to accurately track the target, but also have the ability to accurately track the target even in the face of interference from the target side. is important. Now, if the transmission output 18 of the distance tracking radar in FIG. 1 is _S18 , a signal of _S18 =P(sinωpt)cosωt (1) is irradiated to the target. However, P
(sinωpt) is the pulse amplitude modulated signal of the transmit output 18 of FIG. 2, and ωp is the angular frequency of pulse repetition.

In this case, the target uses a frequency counter or a frequency analyzer to detect that a signal with an angular frequency ω is being emitted from the radar, and detects a signal with an angular frequency ω or noise with a center angular frequency ω. The modulated signal can be easily sent back,
It is possible to easily interfere with target tracking by the other party's radar.

The received input 1, which is a reflected wave from the target, that is, the received signal S ₁ is S ₁ =q[sinωp(tT)]cos[ω(tT)]...(2). However, T is the round trip time from the radar to the target, and q[sinωp(t-T)] is the pulse modulation term of the received signal (therefore, the function q[sinωp(t
−T)] includes the function p[sinωp(t−T)]. ).

Knowing the time T, the distance to the target can be determined from the relationship 1 microsecond = 150 m. However, in order to determine the distance from the radar to the target, it is necessary to demodulate the wideband signal q[sinωp(t-T)], and the receiver naturally has a wideband signal, making it susceptible to interference. Therefore, one of the fundamental solutions from the viewpoint of radio wave interference of the distance tracking radar is to prevent the target side from knowing the transmission signal of the distance tracking radar.

(5) Purpose of the present invention The present invention modulates the modulation format of the transmitted radio waves of the tracking radar using two-phase phase modulation of 0 and π (pi) so that the frequency used by the radar is not easily detected on the target side. None, 0 and π (a wideband pulse wave (or continuous wave) phase-modulated with two phases of pi is irradiated toward the target, and a wideband signal from the target can be received at a narrow band intermediate frequency. It is an object of the present invention to provide a two-phase modulation distance tracking radar that has extremely high radio secrecy and high anti-radio jamming capability.

(6) Main points of the configuration of the present invention Before explaining the embodiments shown in FIGS. 4, 5, 6, and 7 in detail, we will explain the principle of the present invention using the time chart shown in Give an explanation.

In FIG. 3, a transmission output 18 synchronized with a signal for pulse modulation (pulse shaping circuit output) 22
is cosωt and −
Transmit cosωt signals alternately. Here, since the transmission signal is called pulse phase modulation or pulse balance modulation, looking at the spectrum of the transmission signal 18, the center frequency of the transmission signal 18 is ω.
The spectral components of are almost zero. The receiver receives a time T corresponding to the distance between the radar and the target.
Reception input 1, which is a reflected wave from the target, is received with a delay of (seconds). Similar to the transmission output 18, the reception input 1 is received as a pair of [cosω(t-T), -cosω(t-T)] (the reception antenna output 2 is also the same),
In such a phase modulation signal, the spectrum of the center frequency of the carrier wave is zero, so in a simple narrowband receiver according to the prior art that receives the signal by narrowing the bandwidth of the intermediate frequency amplifier, [cosω(t-T) and -cosω
(t-T)] pair is filtered by a narrowband filter and the output becomes almost zero. This means that from the standpoint of jamming radio waves, it is difficult to decipher radar frequencies and generate jamming waves, and radio waves are highly confidential.

Up to now, a case has been described in which cosωt and -cosωt are switched for each transmission, but this does not necessarily have to be the case, and it is sufficient if the number of occurrences of the 0 phase and the π phase is approximately the same.

Now, the transmission source output 15 (S ₁₅ ) is determined as follows.

S ₁₅ = sinωt (3) where ω is the angular frequency of the carrier wave of the transmission source output 15.

The third phase modulator output 16 (S ₁₆ ) is S ₁₆ =sin[ωt+π/2Sign(sinωst)] (4). However, ωs is the voltage controlled oscillator output 28
Alternatively, it is the angular frequency of the signal generator output 20.
moreover It is.

The pulse modulator output 24, the power amplifier output 47 and the transmission output 18 (S ₁₈ ) can be expressed in the same way,
It will look like this:

S ₁₈ = P(sinωpt) sin[ωt+π/2
Sign(sinωst)] =P(sinωpt)sin[π/2Sign(
sinωst)] cosωt...(6). However, S ₂₂ =P(sinωpt)...(7). This equation (7) indicates the pulse shaping circuit output 22.

In the case of the transmission output 18 in equation (6), the principle of demodulating the distance information of the reception input 1, which is a reflected wave from the target, will be explained. Reception input 1 (S ₁ ) is received with a delay of T than transmission, so S ₁ = q[sinωp(t-T)]×sin{π/2S
ign[sinωs(t-T)]}cosω(t-T)...(8).

In order to drop the receive input 1 (S ₁ ) to an intermediate frequency, two mutually orthogonal first phase modulator outputs 7
(S ₇ ) and the second phase modulator output 8 (S ₈ ) are used as switching signals to the first mixer 62 and the second mixer 63. Here, the first phase modulator output 7
(S ₇ ) is S ₇ = sin{π/2Sign[sinωs(t−τ)]}Xco
s[ω _l (t−τ)]……(9). However, π is the amount of delay. The second phase modulator output 8 (S ₈ ) is S ₈ =sin {π/2Sign[cosωs(t−π)]}Xco
Let s[ω _l (t−τ)]……(10). In addition, the following relational expressions, equations (11) and (12) sin {π/2Sign[sinωs(t-T)]}Xsin{π
/2Sign[sinωs(t-τ)]}≒cosωs(T-τ)...
…(11) −sin{π/2Sign[sinωs(t-T)]}Xsin{
π/2Sign[cosωs(t-τ)]}≒sinωs(T-τ)
...(12) holds true. However, is the average of one period.

Therefore, the first mixer output 3 (S ₃ ) is S ₃ =q[sinωp(t-T)]cosωs(T-τ)Xcos
[t(ω- _ωl )-(ωT- _ωlτ )]...(13) This becomes a signal for creating a reference signal for the synchronous detector 67. The second mixer output 4 (S ₄ ) is S ₄ =q[sinωp(t-T)sinωs(T-τ)Xcos[
t(ω−ω _l )−(ωT−ω _l τ)]……(14).

The amplitude limiter output 25 (S ₂₅ ) is the amplitude limiter 66
When the noise is suppressed by |cosωs(T−τ)|>0 (15), the amplitude of equation (15) becomes constant and can be normalized. Furthermore, the pulse modulation signal q[sinωp(t-
The spectrum other than the center frequency of the double-side band waves of T)] is removed by the narrow band first intermediate frequency amplifier 64, and the signal of equation (13) becomes _S25 = cos[t(ω-ω _l ) −(ωT−ω _l τ)]
...(16) It becomes a narrow band signal and becomes a reference signal to the synchronous detector 67.

Similarly, from the second intermediate frequency amplifier output 6 (S ₆ ), the spectrum other than the vicinity of the center frequency of both sideband waves is removed by the narrow band second intermediate frequency amplifier 65, and S ₆ = sinωs (T - τ). cos[t(ω−ω _l )
−(ωT−ω _l τ)]……(17) Equation (17) includes the round trip time T to the target, which corresponds to the distance to the target, which is the purpose of the present invention. , is included in the amplitude component sinωs(T−τ) due to phase modulation, although it is a narrowband signal.

In addition, the amplitude component sinωs (T−τ) due to phase modulation
is a synchronization error component, so it is a narrowband signal when T≈τ. The synchronous detector output 9 (S ₉ ) is S ₉ = ₂₅・₆ = sinωs (T - τ) ... (18), and since equation (18) can take positive and negative values around 0, the synchronous detector 67 is desirable as the output.

(a) Therefore, if a signal corresponding to the distance T from the radar to the target can be freely generated in the distance radar, then T=τ...(19), which makes equation (18) always 0. By doing so, the radar can track the target, and the distance to the target can be determined from the known quantity τ.

(b) In order to set the right side of equation (18) to 0, T = τ in equation (19), but ωs (T - τ) = 0, π, 2π, ..., nπ
...(20) may also be used. However, n is an integer. Here, τ is the amount that can be generated by the radar itself, so if τ = 0 ... (21), then ωsT = 0, π, 2π, ..., nπ ... (22), which is proportional to the distance from the radar to the target. Even if T in equation (22), which is the amount to Since it is easy to measure the frequency ωs by the radar itself, the time (distance) from the radar to the target is calculated from the angular frequency ωs.
can be obtained from equation (22).

(7) Embodiment of the present invention A first embodiment of the present invention shown in FIG. 4 will be described.

Signal generator output 2 which is the output of signal generator 75
0 is the transmission source 59 in the third phase modulator 71
Phase modulates the transmission source output 15, which is the output of
The third phase modulator output 16 is obtained by performing phase modulation of two phases with a phase difference of π radians.

The distance signal generator output 46, which is a signal generated by the distance signal generator 76 and corresponds to the time T from when the radar irradiates an electromagnetic wave to a target until it is reflected back to the radar receiver, is generated by a pulse reference signal generator. 72
, it is calculated whether the arrival time of the reflected wave from the target does not overlap with the transmission time of the transmission output 18 and becomes the pulse reference signal generator output 21, which is made into a signal with a predetermined pulse width by the pulse shaping circuit 73. This becomes the pulse shaper circuit output 22.

The third phase modulator output 16 becomes the pulse modulator output 24 by using the pulse shaping circuit output 22 as a modulating signal in the pulse modulator 60, and is amplified by the power amplifier 61 to output the power amplifier. 47, and the transmission power 18 is directed toward the target by the transmission antenna 50.

Reception input 1, which is a reflected wave from the target, is received by reception antenna 51 and becomes reception antenna output 2, which is then sent to first mixer 62 and second mixer 63.
, and using the first phase modulator output 7 and the second phase modulator output 8, respectively, the first
The frequency is converted into a mixer output 3 and a second mixer output 4, and the frequency is converted into a first intermediate frequency amplifier 64 and a second intermediate frequency amplifier 64, respectively.
The intermediate frequency amplifier 65 amplifies the first intermediate frequency amplifier output 5 and the second intermediate frequency amplifier output 6.
become. Further, the amplitude of the first intermediate frequency amplifier output 5 is made constant by an amplitude limiter 66 to become an amplitude limiter output 25, which becomes a reference signal to a synchronous detector 67. The second intermediate frequency amplifier output 6 is synchronously detected in a synchronous detector 67 to become a synchronous detector output 9, which is input to a distance signal generator 76.

The other output of the signal generator output 20 is sent to a delay device 74 using the distance signal generator output 46 as a control signal to change the delay amount (corresponding to τ) so that the synchronous detector output 9 is always 0. In addition, it becomes the delay device output 19, and further becomes the π/2 phase shifter output 27 whose phase is changed by π/2 radians by the π/2 phase shifter 69. Then, the local oscillator output 13 produced by the local oscillator 56 is phase-modulated in a first phase modulator 70 that receives the π/2 phase shifter output 27, and is applied to the first mixer 62. The device output becomes 7. On the other hand, the second phase modulator 82 converts the local oscillator output 13 into the delay output 1
9 to produce a second phase modulator output 8. This second phase modulator output 8 is applied to a second mixer 63.

According to this first embodiment, by controlling the delay amount of the delay device 74 to always set the equation (18) to 0, it is possible to track the target and find the distance to the target from the delay amount. .

The second embodiment shown in FIG. 5 will be described, but to avoid duplication, only the differences from FIG. 4 will be described.

The voltage controlled oscillator 68 is controlled by the output voltage of the synchronous detector output 9 to obtain the voltage controlled oscillator output 28 whose oscillation frequency is changed so that equation (18) becomes zero. The voltage controlled oscillator output 28 is π/
This becomes an input signal to the second phase shifter 69 and the second phase modulator 82. Further, one of the voltage controlled oscillator outputs 28 becomes a modulation signal to the third phase modulator 71, and the other output 28 is input to the distance calculator 83.
The distance calculator 83 calculates the distance (time) to the target from equation (22) and outputs the distance calculator output 26.
Input to pulse reference signal generator 72. 4th below
It is similar to the figure.

According to this second embodiment, the oscillation angular frequency ωs of the voltage-controlled oscillator 68 is changed in accordance with the change in the amount T proportional to the distance from the radar to the target, so that equation (22) is established, and the angular frequency From ωs, the time (distance) from the radar to the target can be determined from equation (22).

The third embodiment shown in FIG. 6 will be explained.
In this figure, only the carrier wave in FIG. 4 has been changed from electromagnetic waves to light, so only the differences from FIG. 4 will be described.

Optical transmit source output 30 produced by optical transmit source 77
The power amplifier output 47 amplified by the power amplifier 61 is used as a modulation signal, which is modulated by the optical modulator 78, becomes the optical modulator output 31, and is directed from the transmission optical system 79 to the target as the optical transmission output 32. irradiated. In this case, two-phase phase modulation with a phase difference of π radians in the third phase modulator 71;
Pulse modulation in the pulse modulator 60 is performed on the transmission source output 15 (which becomes a subcarrier signal) which is the output of the transmission source 59.

The optical reception input 33, which is a reflected wave from the target, is received by the reception optical system 80 and becomes the reception optical system output 34, which is detected by the photodetector 81 and becomes the photodetector output 35. Since the signal has the same characteristics as the receiving antenna output 2 in FIG. 4, no further explanation is necessary.

The fourth embodiment shown in FIG. 7 will be explained.
Since the carrier wave in FIG. 5 is simply changed from electromagnetic waves to light, only the differences from FIG. 5 will be described.

Optical transmit source output 30 produced by optical transmit source 77
The power amplifier output 47 amplified by the power amplifier 61 is used as a modulation signal, which is modulated by the optical modulator 78, becomes the optical modulator output 31, and is directed from the transmission optical system 79 to the target as the optical transmission output 32. irradiated. In this case, two-phase phase modulation with a phase difference of π radians in the third phase modulator 71;
Pulse modulation in the pulse modulator 60 is performed on the transmission source output 15 (which becomes a subcarrier signal) which is the output of the transmission source 59.

The optical reception input 33, which is a reflected wave from the target, is received by the reception optical system 80 and becomes the reception optical system output 34, which is detected by the photodetector 81 and becomes the photodetector output 35. Since the signal has the same characteristics as the receiving antenna output 2 in FIG. 5, further explanation is unnecessary.

(8) Supplementary explanation of the embodiment (a) The output signal of the voltage controlled oscillator 68 in FIGS. 5 and 7 does not have to be a sine wave, but may be a distorted wave such as a sawtooth wave.

(a) Although the transmitting antenna and the receiving antenna are configured separately in FIGS. 4 and 5, the same antenna may be used for transmitting and receiving. Similarly, the 6th
Although the optical systems in the figures and FIG. 7 are configured separately for transmission and reception, the same optical system may be used for transmission and reception.

(C) (6) In the main points of the configuration of the present invention, a pulse type distance tracking radar has been described, but it is also possible in principle to use a continuous wave type for transmission and reception.

(D) In FIGS. 4 and 6, the output of the signal generator 75 has been explained with a single spectrum such as a sine wave, but it may be a signal with a wide spectrum such as random noise.

(E) The first embodiment shown in Fig. 4, the second embodiment shown in Fig. 5,
The amplitude limiter 66 used in the third embodiment shown in FIG. 6 and the fourth embodiment shown in FIG. be.

(9) Effects of the present invention (1) Since the phase is transmitted in two phases, 0 and π radians, from the standpoint of causing radio wave interference, the 2nd aspect of the present invention is
Since it is difficult to detect the phase signal, decipher the frequency, and send the interfering radio waves back to the other radar, it is a distance tracking radar with high radio secrecy and excellent resistance to radio interference.

(2) When a single frequency disturbance is applied to the distance tracking radar of the present invention, the mixer acts as a multiplier, so the first mixer output 3 has the same spectrum as the first phase modulator output 7. I get the output,
The second mixer output 4 has the same spectrum as the second phase modulator output 8, and the first
Since the spectrum is dispersed outside the narrowband first intermediate frequency amplifier 64 placed after the mixer 62 and the narrowband second intermediate frequency amplifier 65 placed after the second mixer 63, the receiver There is little interference with

(3) Although it has not been possible to achieve accurate ranging with conventional narrowband reception radars, the present invention makes it possible to measure distances with narrowband reception, and it is possible to measure distances using narrowband reception, ensuring that the transmitted and received pulses match. This can be done by repeating the problem and changing the pulse interval.
Transmission output efficiency improves.

(4) Since the frequency bandwidth of the bandpass amplifier can be narrowed, the unavoidable inherent noise in the receiver can be reduced, making it an extremely sensitive distance tracking radar.

(5) The distance measuring radar of the present invention can be used in the same radio wave format when used in combination with a narrowband reception type monopulse angle tracking radar, so this device can be used in combination with a monopulse tracking radar rather than being used alone. It can also be used as

(6) In conventional pulse modulation radar, when the received signal, which is a reflected wave from the target, passes through a narrow-band intermediate frequency amplifier, the component containing distance information (round trip time T to the target) is lost, but the phase When a modulated signal is combined with the configuration according to the present invention, a component containing distance information is output even though a narrow band intermediate frequency amplifier is used.

(7) Therefore, from an economic point of view, when comparing a distance measuring radar that tracks the same distance with the pulse type distance measuring radar shown in the conventional example in Figure 1,
The price is extremely low.

[Brief explanation of drawings]

Figure 1 is a block diagram showing a conventional example of distance tracking radar, Figure 2 is a time chart for explaining the conventional example in Figure 1, and Figure 3 is a time chart for explaining the embodiment in Figure 4. 4 is a block diagram of the first embodiment of the present invention using a delay device using electromagnetic waves; FIG. 5 is a block diagram of the second embodiment using a voltage controlled oscillator using electromagnetic waves; FIG. The figure is a block diagram of a third embodiment using an optical delay device, and FIG. 7 is a block diagram of a fourth embodiment using an optical voltage controlled oscillator. 1...Reception input, 2...Reception antenna output, 3
...First mixer output, 4...Second mixer output, 5
...First intermediate frequency amplifier output, 6... Second intermediate frequency amplifier output, 7... First phase modulator output, 8...
...Second phase modulator output, 9...Synchronized detector output,
10... Amplitude detector output, 13... Local oscillator output, 15... Transmission source output, 16... Third phase modulator output, 18... Transmission output, 19... Delay device output, 20... Signal generation 21...Pulse reference signal generator output, 22...Pulse shaping circuit output, 23...Reference pulse, 24...Pulse modulator output, 25...Amplitude limiter output, 26...Distance calculator output , 27...π/2 phase shifter output, 28...
Voltage controlled oscillator output, 29... Reference pulse generator output, 30... Optical transmission source output, 31... Optical modulator output, 32... Optical transmission output, 33... Optical reception input, 34... Reception optical system Output, 35...Photodetector output, 36...Mixer output, 37...Intermediate frequency amplifier output, 46...Distance signal generator output, 47...
...Power amplifier output, 50...Transmission antenna, 51
... Reception antenna, 52 ... Mixer, 53 ... Intermediate frequency amplifier, 54 ... Amplitude detector, 55 ... Display, 56 ... Local oscillator, 57 ... Reference pulse generator, 58 ... Shaping circuit , 59... transmission source, 6
0... Pulse modulator, 61... Power amplifier, 62
...First mixer, 63...Second mixer, 64...
1st intermediate frequency amplifier, 65...2nd intermediate frequency amplifier, 66...amplitude limiter, 67...synchronous detector,
68... Voltage controlled oscillator, 69... π/2 phase shifter, 70... First phase modulator, 71... Third phase modulator, 72... Pulse reference signal generator, 73...
... Pulse shaping circuit, 74 ... Delay device, 75 ... Signal generator, 76 ... Distance signal generator, 77 ... Optical transmission source, 78 ... Optical modulator, 79 ... Transmission optical system, 80 ... Receiving optical system, 81...Photodetector, 8
2...Second phase modulator, 83...Distance calculator.

Claims (1)

[Scope of Claims] 1. A distance tracking radar equipped with a transmitting antenna, a receiving antenna, a mixer, a local oscillator, an intermediate frequency amplifier, a synchronous detector or multiplier, a delay device, and a signal generator, wherein the signal generator A signal obtained by phase-modulating the output of the transmission source using the output signal of The outputs of the local oscillators are phase-modulated by being delayed by a time corresponding to the propagation time from transmission to the target to reception using the delay device, and are made orthogonal to each other. The signals are used as switching signals and are received by the mixer. Each signal is reduced to two intermediate frequencies, amplified by the intermediate frequency amplifier, and synchronously detected or multiplied by the synchronous detector or multiplier. Using the obtained signal, the amount of delay of the delay device is determined. A distance tracking radar that tracks a target by changing the distance. 2. In the case of a pulse method in which a pulse wave is irradiated toward a target, the output signal of the synchronous detector or multiplier is used to vary the pulse repetition frequency, thereby adjusting the transmission time and the amount of reflected waves from the target. The distance tracking radar according to claim 1, characterized in that coincidence with reception time is prevented. 3. A distance tracking radar equipped with a transmitting antenna, a receiving antenna, a mixer, a local oscillator, an intermediate frequency amplifier, a synchronous detector or a multiplier, and a voltage-controlled oscillator, which uses the output signal of the voltage-controlled oscillator to generate a transmitting source output. A phase-modulated signal is irradiated toward the target by the transmitting antenna, and the reflected wave from the target is received by the receiving antenna and added to the mixer for a time corresponding to the propagation time from transmission to the target to reception. , the outputs of the voltage controlled oscillators whose oscillation frequencies have been changed are made orthogonal to each other, the signals obtained by phase modulating the outputs of the local oscillators are used as switching signals, and the received signals are reduced to two intermediate frequencies by the mixer, respectively; Tracking the target by changing the frequency of the voltage controlled oscillator using a signal obtained by amplifying the intermediate frequency amplifier and synchronously detecting or multiplying the signal by the synchronous detector or multiplier. A distance tracking radar featuring: 4 In the case of a pulse method in which a pulse wave is irradiated toward a target, by using the oscillation frequency of the voltage controlled oscillator and making the pulse repetition frequency variable, the transmission time and the reception time of the reflected wave from the target can be adjusted. The distance tracking radar according to claim 3, characterized in that the distance tracking radar prevents coincidence of the following. 5. A distance tracking radar equipped with a transmitting optical system, an optical modulator, a receiving optical system, a photodetector, a mixer, a local oscillator, an intermediate frequency amplifier, a synchronous detector or multiplier, a delay device, and a signal generator, Using a signal obtained by phase-modulating a subcarrier signal with an output signal of the signal generator, the optical transmission output modulated by the light source is irradiated from the transmission optical system toward a target by the optical modulator,
The receiving optical system receives the reflected light from the target, the photodetector detects the subcarrier signal and adds it to the mixer, and the output of the signal generator is transmitted from the optical transmission to the target using a delay device. Using signals obtained by phase-modulating the outputs of the local oscillators by delaying them by a time corresponding to the propagation time until reception, making them mutually orthogonal, and phase-modulating the outputs of the local oscillators, respectively, dropping the subcarriers to two intermediate frequencies by the mixer, The target is tracked by changing the delay amount of the delay device using a signal obtained by amplifying the intermediate frequency amplifier and synchronously detecting or multiplying the signal by the synchronous detector or multiplier. A distance tracking radar characterized by: 6. In the case of a pulse method in which pulsed light is irradiated toward a target, the output signal of the synchronous detector or multiplier is used to vary the pulse repetition frequency, thereby adjusting the transmission time and the amount of reflected waves from the target. 6. The distance tracking radar according to claim 5, characterized in that coincidence with reception time is prevented. 7. A distance tracking radar equipped with a transmitting optical system, an optical modulator, a receiving optical system, a photodetector, a mixer, a local oscillator, an intermediate frequency amplifier, a synchronous detector or multiplier, and a voltage controlled oscillator, wherein the voltage controlled Using a signal obtained by phase modulating a subcarrier signal with an output signal of an oscillator, the optical transmission output modulated from the light source by the optical modulator is irradiated toward the target from the transmission optical system, and the optical transmission output is irradiated from the target by the reception optical system. The subcarrier signal is detected by the photodetector and added to the mixer, and the oscillation frequency is changed by a time corresponding to the propagation time from light transmission to the target to light reception. The outputs of the voltage controlled oscillators are made orthogonal to each other, and the signals obtained by phase modulating the outputs of the local oscillators are used as switching signals, respectively dropped to two intermediate frequencies by the mixer, and amplified by the intermediate frequency amplifier. A distance tracking radar characterized in that a target is tracked by changing the frequency of the voltage controlled oscillator using a signal obtained by synchronous detection or multiplication by a detector or a multiplier. 8 In the case of a pulse method in which pulsed light is irradiated toward a target, by using the oscillation frequency of the voltage-controlled oscillator and making the pulse repetition frequency variable, the transmission time and the reception time of the reflected wave from the target can be adjusted. 8. The distance tracking radar according to claim 7, wherein the distance tracking radar prevents coincidence of the following.