JPH01124784A - Vt fuse - Google Patents

Abstract

PURPOSE:To make it difficult for an opponent side to find a radio wave and to reduce the influence of disturbance by sending a wave by spread spectrum and reducing the sent electric power density per unit frequency band. CONSTITUTION:The output of an oscillator 1 is sent from 1st and 2nd antennas 4a and 4b by spread spectrum modulation by using the output of a spread spectrum code generator 21a. A reflected signal from a target is received by 3rd and 4th antennas 4c and 4d and then inputted to 1st-5th correlators 16a-16e after homodyne detection is performed by a mixer 5. Ignition circuits 10a-10d are controlled with the outputs of those correlators 16a-16d and the oscillation frequency of a voltage-controlled oscillator 20 which drives the generator 21a is controlled.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is directed to a target such as an aircraft that is within the effective range of a warhead of a flying object such as an artillery shell or a missile, and that is visible from the flying object. This relates to a proximity fuse that detects in which direction a target is present.

[Conventional technology]

FIG. 5 is a diagram showing the structure of a conventional proximity fuze disclosed in, for example, Japanese Utility Model Publication No. 62-3741.

In Fig. 1ζ, (1) is an oscillator, and (2) is this oscillator (
1) is a directional coupler that takes out a part of the output, (3) is a circulator that guides the output of this directional coupler (2) to the antenna (41), (5) is a mixer, (6) is a video amplifier, ( 7) is a Doppler filter, (8) is a detector, (9)
is the comparator, α[ is the ignition circuit, and αυ is the threshold setter.

Next, the operation will be explained. The signal transmitted from the antenna (4) is irradiated to the target, and the reflected signal is received again by the antenna (4), passes through the circulator (3),
After being mixed with a part of the output of the directional coupler (2) in the mixer (5) and amplified in the video amplifier (6), only the Tongela frequency corresponding to the relative speed difference with the target flying object is passed. The signal passes through a Doppler filter (7) shaped like T, and its amplitude is detected by a detector (8). The output of this detector (8) is compared with the threshold set by the threshold setter aD by the comparator (9), and the
When the output of the detector (8) is large, the ignition circuit ate is activated and the warhead of the flying object explodes.

The conventional proximity fuse is constructed as described above, and is activated by detecting the Doppler frequency component due to the relative speed difference it of the target flying object.

[Problems that the invention attempts to solve]

However, as mentioned above, since the transmission output C is a single frequency, it is easy to detect that the enemy is emitting radio waves.
Also, it remains the same against interference waves.

If the frequency is within the range that passes through the Doppler filter (7), no countermeasures can be taken. Furthermore, the zero operating range changes depending on the strength of the reflected power from the target.

There is the problem that it is difficult to match the effective range of the warhead, and there is also the problem that when the flying object attempts to fly at a low altitude, it may malfunction due to waves reflected from the ground or sea surface, or the receiving system may become saturated. There was a point, and it was not possible to detect in which direction the target existed as seen from the flying object.

This invention was made to solve the above-mentioned problems, and it is possible to make it less susceptible to interference if the enemy discovers the use of radio waves. The purpose is to obtain a proximity fuze that has a clearly defined operating range, eliminates malfunctions caused by reflected waves from the ground or sea surface, saturation of the receiving system, and has the function of detecting the direction of the target.

[Means for solving problems]

The proximity fuse according to the present invention widens one frequency band by modulating the transmitted wave with a spread spectrum code 6ζ, and even if it is discovered by the enemy and is interfered with, the video amplifier of the received signal can be used. Change the output of vJ41 with a correlator! Interfering waves that are not modulated with the same code as the modulation code are despread by taking a phase difference with the code 1 bit before and 1 bit after the r code.

Because it goes out of the band of the drag filter of this proximity fuze, we made it strong against interference, and set the zero operating range to a distance corresponding to the round trip time of a radio wave that differs by only 1 bit from the modulation code - and 1 point before and after that. The oscillation frequency of the voltage-controlled oscillator that drives the first code generator can be limited to the distance range corresponding to the round-trip time of radio waves bit by bit, and the oscillation frequency of the voltage-controlled oscillator that drives the first code generator can be adjusted to the distance to the ground or sea surface in the downward direction of the flying object. By changing the range according to the distance, the distance range is changed according to the distance to the ground or sea surface.

In addition, since the signal strength of the reflected wave from the ground or sea surface is inversely proportional to the square of the distance from the flying object to the ground or sea surface,
By using a variable attenuation gain whose attenuation is inversely proportional to the square of this distance, the received signal input to the mixer by this reflected wave is constant regardless of the distance to the ground or sea surface, and in the upward direction of the flying object, By keeping constant the oscillation frequency of the clock oscillator driving the second code generator.

The above distance range is made to match the effective range of the warhead of the flying object, and.

Switching the input to the receiving system below the mixer to either the third or fourth antenna output attached to the right or left part of the fuselage using a high-speed synchronizer.From fζ, the target's location as seen from the flying object Information on whether the target exists on the right or left side is obtained, and information on whether the target exists on the lower or upper side is generated by the first or second code generator. By knowing which code is being received, the combination of these right or left and lower or upper codes can be used to determine the position of the target as seen from the aircraft, that is, the axis of the aircraft. This makes it possible to detect in which quadrant of orthogonal planes a target exists.

[Effect]

In the proximity fuse of the present invention, in the downward direction of the projectile, the output of the nine oscillators is spread spectrum modulated by the output of the first 1-bit delay circuit, which delays the output of the first spread spectrum code generator by 1 bit. Transmitted from the first antenna, and for the upward direction of the projectile, the output of the 8 oscillator is spread spectrum modulated by the output of the third 1-bit delay circuit, which delays the output of the second spread spectrum code generator by 1 bit. These signals are then transmitted from a second antenna, the reflected signals from the target are received by a third or fourth antenna, and the output of the third or fourth antenna is switched using a switch. choose.

Homodyne detection is performed by mixing this signal with a part of the output of the oscillator. The detection output is amplified by a video amplifier and then divided into five equal parts, each of which is divided into five correlators, a first correlator, and a second correlator.
and a third correlator, the output of the first code generator, the second code generator which is delayed by 2 bits from the first code generator,
0] Correlation is taken between the output of the 1-bit delay circuit and the output of the ΔT delay circuit delayed by 2 bits+ΔT from the first code generator, and in the fourth correlator and the fifth correlator.

A correlation is taken between the output of the second code generator and the output of the 40th 1-bit delay circuit which is delayed by 2 bits from the second code generator, and the relative speed between the preset target and the flying object is determined. It passes through first to fifth dragura filters through which only Doppler frequency band waves corresponding to the difference range can pass, and the outputs thereof are detected by first to fifth detectors, respectively. A constant voltage is added to the output of the first wave detector in the first bias amplifier, and this and the output of the second wave detector are compared in the first comparator. The first comparator generates a pulse when the output of the first bias adder becomes greater than the output of the first bias adder.

Further, the output of the third detector is compared with the output of the first bias adder in a second comparator, and after the output is integrated in an integrator, the first code generator is driven. Controls the oscillation frequency of the voltage controlled oscillator.

The output Cj of the integrator drives a function generator to cause the variable attenuator to generate an attenuation coefficient inversely proportional to the square of the distance between the flying object and the ground or sea surface.

Furthermore, a constant voltage is added to the output of the fourth detector in the second bias adder, and this and the output of the fifth detector are compared in the first comparator. When the output becomes larger than the output of the second bias adder,
The comparator 1j generates a pulse.

By the way, the above switch is driven by the output of the synchronizer, and when the output is high level, the above switch is connected to the third antenna iζ, and when the output is low level, it is connected to the fourth antenna. . The output of the zero inverter is the inverted high or low output level of the synchronizer. Here, when the receiving system outputs the first code 5-&, the first comparator outputs a high-level pulse, so the first comparator ANDs the outputs of the synchronizer and the first comparator. When there is an IAND AND circuit, the direction tζ is lower and right, as shown in FIG.
Indicates that the target exists in the first quadrant.Similarly to T0, the second quadrant. When the third or fourth A N D circuit has an output C1, it indicates that the target exists in the nth, first, or second quadrant, respectively. In this way, the first to fourth A N
D(The output pulse of gl path is.

Each of the first to fourth ignition circuits is activated to detonate the warhead in an explosion pattern optimal for the target direction.

〔Example〕

Hereinafter, one side of the present invention will be explained with reference to FIG. 1ζ. In Figure 1, (1) is an oscillator, and (2) is this oscillator (
A directional coupler for extracting part of the output of 1).

(4a) is the first antenna that emits radio waves into the air below the flying object; (41)) is the second antenna that emits radio waves into the air above the flying object; (4) and ( 4d) are the third and fourth antennas for reception attached to the right and left parts of the fuselage of the flying object.

(5) is a mixer, (6) is a video amplifier, (7a)
~(7ri is the 1st to 5th Tongera filter, (8a
) to (8 is the first to fifth detectors, (9a) to (9
First to third comparators, (10a) to (10d)
are the first to fourth ignition circuits, (12a) and (12b
) are the first and second modulators.

C3 is a variable attenuator for attenuating the output of the first modulator (12a), and α aneurysm is the third. Fourth antenna (4th antenna)

(4d) A switch for taking out either of the received signals, C5 divides the output of the directional coupler (2) into two equal parts and sends it to the first and second modulators (12a) and (121)) (16a) to (16) are the 11th to 5th correlators; (17a) and (17b) are the first and second bias adders;

(18a) - (18d) are first to fourth AND circuits;
C9 is an integrator, Tsuru is a voltage controlled oscillator, (24a) and (21b) are first and second code generators, (22
a) to (22d) are first to fourth 1-bit delay circuits, c
! In the old ΔT delay circuit, C4 is a clock oscillator, (c) is a function generator, and (to) is a synchronizer that drives switch a4 and switch @. Also, this synchronizer (
The output of c) is input to the first and fourth AND circuits (18a) and (18d), and the output of the 0 inverter @ is input to the second and third AND circuits (181) and (18). It has become.

By the way, spread spectrum codes can be 0M series, gold codes, etc., but all of them generate a high correlation output for signals that are in phase with the white code, and other codes or codes that are out of phase by 1 bit or more. For this case, only an extremely low correlation output fζ is generated. This invention uses this principle.

The output of the first 1-bit delay circuit (22a), which is delayed by 1 bit from the output of the first code generator (21a), is converted into a transmission signal at the first modulator (12a) fζ! After applying 9I, the output of the first modulator (12a) is attenuated by a variable attenuator (13fζ) and transmitted by the first antenna (4a) in a direction below the flying object.

On the other hand, a third 1-bit delay circuit (second modulator (121) with the output of 22), which is delayed by one bit from the output of the code generator (211), modulates the transmission signal,
A second antenna (4b) transmits radio waves in the upper direction of the flying object.

Here, the first and second code generators (21 and (211)
) generate different codes, which will be referred to as a first code and a second code, respectively.

The reflected waves from the target are transmitted to the third or fourth antenna (4C) or (4d) attached to the right or left side of the body of the flying object.
, one of the signals is extracted by switch I, homodyne detected by a mixer (5), amplified by a video amplifier (6), and the first signal is received by the first . Second and third correlators (16
a), (16b) and (160 near) and the correlation is taken with the first code. However, in the first correlator (16a),
Since the correlation is taken with the first code whose phase is one bit ahead of the transmitted signal, the output is only the signal obtained by despreading the transmitted signal, which is uncorrelated with the receiver noise and the interference signal, by the first code. Does not occur. After passing this signal through a Doppler filter (7a) and a detector (8a), a bias adder (17a) adds a constant bias to create an adaptive threshold according to the radio wave environment C inside and outside the proximity fuze. can be set.

In addition, in the second correlator (161), correlation is taken using the first code that is 1 bit behind the modulated transmission wave, so the range of 1 bit before and after the code of N1, which is 1 bit behind the transmission wave. A strong correlation output is generated only when the reflected wave from the iζ target appears. This signal contains a Doppler frequency corresponding to the relative velocity difference between the target and the flying object, so
It passes through a Doppler filter (7b), is detected by a detector (8b), and is sent to a bias adder (1) by a 9m1 comparator (9a).
7a). Second correlator (161))
Since the correlation is taken by the output of the 20th] 1-bit delay circuit (22t), uncorrelated receiver internal noise, external interference waves, and the modulated wave of the first code with a 0-phase shift are detected.

The signal based on the modulated wave of the second code is despread.

A signal only in the passband of the Doppler filter (7b) is sent to the detector (81), added to the output of the Doppler frequency component from the target, and appears at the output of the detector (8b). Therefore, from the output of the first comparator (9a), internal noise of the receiver, external interference signal components and uncorrelated transmitted signal components are subtracted, and only the target signal component appears.

Furthermore, in the third correlator (No. 16), since the correlation is taken by the first code delayed by 1 bit + ΔT from the modulated transmission wave, the correlation is taken by the first code delayed by 1 bit + ΔT from the transmitted signal. When the reflected wave appears in the range of 6ζ
Generates a strongly correlated output.

FIG. 3 shows time and the first bias adder, the second . FIG. 6 is a diagram showing the relationship on the output voltage of the third wave detector.

In the figure, A is the output voltage of the first bias adder (17a).

The symbol "A" indicates the output voltage of the second detector (8b), "C" indicates the output voltage of the third detector (8C), and "2" indicates the tracking distance.

As shown in Figure 3 1ζ, the third detector (8) can obtain the correlation output at the farthest distance from the flying object, so if the flying object is flying at a low altitude, the reflected waves from the ground or sea surface are detected in the above range. It is assumed that the radio waves were obtained within the round trip distance corresponding to
A correlated output will occur. Since this signal includes a Doppler frequency corresponding to the speed of the flying object, it passes through a Doppler filter (7C) and is detected by a detector (8C), and then is added to the first bias by a second comparator (9b). vessel (t7
It is compared with the output of a). The third correlator (Δ in 16
Since the correlation is removed by the output of the T delay circuit, uncorrelated receiver internal noise, external interference waves, and uncorrelated transmitted signals are despread and passed through the Doppler filter (7C). Band-only signals are detected by a detector (sc)
The outputs of the Doppler frequency components of the 9 reflected waves sent by iζ are added together and appear at the output of the detector (8C). Therefore, the output of the second comparator (5b) is the internal noise of the receiver,
External interference signal components and uncorrelated transmitted signal components are subtracted, leaving purely reflected signal components. This signal is integrated by an integrator α9 and input to the voltage controlled oscillator section to control its oscillation frequency. The relationship between the input voltage and the output frequency of the voltage controlled oscillator is shown in Figure 4. The output voltage of (8C) is small, the output of integrator a!1 is Ov, and the output oscillation frequency of voltage controlled oscillator ■ is the corresponding frequency f
However, when the flying object attempts to fly low, an output is generated in the third detector (8C) and the output voltage exceeds the output voltage of the bias adder (17a).
The comparator (9b) outputs the difference voltage between the two. This output voltage is integrated by integrator a9, ! Since it is input to the pressure controlled oscillator ■, its output frequency is as shown in Figure 4
Rise T as shown. The first code generator (21a) is
Since this is driven by a voltage controlled oscillator.

As the frequency increases, the period of one bit becomes shorter, and the corresponding round-trip distance of radio waves also becomes shorter.
The output time width of the third detector (8C) shown in Fig. 3 C becomes narrower, so the output voltage of the third detector (8C) decreases, and this voltage increases the tracking distance shown in Fig. 3. There is a balance between the two points, that is, the first code generator (21) of the voltage controlled oscillator.

The first and i2 1-bit delay circuits (22a) and (
22b).

JT delay circuit 0. The third correlator (16), the third Doppler filter (7c), the third detector (oo), the second comparator (9b) and the integrator a9jζ are input from the video amplifier (6). A loop is set up to track reflected waves from the ground or sea surface, and this tracking distance automatically changes depending on the altitude of the flying object.Therefore, the second correlator (161) ) then.

Since the correlation is taken by the first code which is ΔT before the third correlator (16), the second detector (8b) f
The distance range in which the ζ correlation output can be obtained also varies depending on the flight altitude.
It is inside the correlation output range of li. From this tζ,
Even if the flying object attempts to fly at a low altitude, the output of the second detector (8b) increases due to reflected waves from the ground or sea surface forces 1, and the first comparator (9a) incorrectly receives a pulse. The second detector (8b) is no longer generated, and only when it appears within the distance between the target or flying object and the ground or sea surface.
The output will be obtained.

Incidentally, the output of the integrator 13 includes information on the distance between the flying object and the ground or sea surface due to the tracking loop. Therefore, the variable attenuator 03 is controlled by the frame number generator (c).
By controlling the attenuation amount to be inversely proportional to the square of the distance from the flying body to the ground or sea surface, the reception input to the mixer (5) due to the reflected wave from the ground or sea surface is controlled by the function of variable attenuator 0. By.

Attenuation is inversely proportional to the square of the distance between the flying object and the ground or sea surface. However, the received intensity of the reflected wave from the ground or sea surface is inversely proportional to the square of the distance Sζ, so the use of variable attenuator α3 is necessary. From fζ, mixer (5
) will not change depending on the distance between the flying object and the ground or sea surface.

The output of the video amplifier (6) is also connected to the fourth and fifth
Correlator (16d) and a second code generated by a second code generator (21b) driven by a clock oscillator (2) with one oscillation frequency fL in (16) are used for correlation. Since the correlator (16d) of No. 4 takes the correlation with the second code whose phase is one bit ahead of the transmitted signal, its output is the same as that of the transmitted signal which has no correlation with the receiver noise interference signal. Only a signal despread by the code is generated.

This signal is passed through a Doppler filter (7d) and a detector (8d).
By adding a constant bias using the second bias adder (17b), an adaptive threshold can be set according to the radio wave environment inside and outside the proximity fuze.

In addition, in the fifth correlator (1615>, correlation is established by the second code delayed by 1 bit from the modulated transmission wave, so the range of 1 bit before and after the second code delayed by 1 bit from the transmission wave is A strong correlation output is generated only when a reflected wave from the target appears.This signal contains a Doppler frequency corresponding to the relative speed difference between the target and the flying object, so it is The wave is detected by the detector (8C), and the third comparator (9C) is detected by the #!2 bias adder (
17tl). Since the correlation is taken by the output of the fourth 1-bit delay circuit (22d) in the fifth correlator (16-bit), uncorrelated internal noise of the receiver, interference waves from the outside, and the second The signal due to the modulated wave of the code and the modulated wave of the first code is despread, and the signal of only the pass band of 7 is sent to the detector (8e).
The signal is sent to the target and added to the output of the Doppler frequency component from the target, and appears at the output of the detector (8e). Therefore, the output of the third comparator (9) is obtained by subtracting the receiver's internal noise, external interfering signal components, and uncorrelated transmitted signal components.

Purely only the target signal component appears.

Next, FIG. 2 is a view of a cross section perpendicular to the aircraft axis of the flying body, seen from the rear of the flying body, where the y-axis represents the left-right axis, and the z-axis represents the vertical axis. The positive direction of the y-axis, that is, the right direction (!-2
The quadrant defined by the positive direction of the axis, that is, the downward direction, is the first quadrant, hereinafter referred to as the second quadrant.

The first and second quadrants are defined as shown in the figure. In the figure, A represents the body of the flying object.

(4Ba) to (4d) indicates the fourth antenna to the first 1
mouth.

C, 2 and E are the first. Second. The third and fourth antennas (
4a), (4b), (4d) and (4d) representing the radiation pattern by When connected to the right antenna (4C),
Since a high level pulse is obtained from the output of the first comparator (9a) and the output of the synchronizer ■, which is another input of the first AND circuit (18a), is at a high level, this first The output pulse of the comparator (9a) is passed to activate the first ignition circuit (10a). That is, from the perspective of the flying body.

The first firing circuit (10a) is activated when a target is present in the downward and rightward direction, ie in the first quadrant. Similarly, when the target exists in the 2nd, 1st and 2nd quadrants, the 2nd... third and fourth ignition circuits (101)),
(10 and (10d) are activated to identify the direction in which the target exists.

Note that the second and 40th] 1-bit delay circuits are designed to delay the outputs of the first and 30th] 1-bit delay circuits by 1 bit, but the spread spectrum codes of the first and second code generators are It would be better if it could be delayed by a bit.

Further, for the first to fourth AND circuits, two switch devices which operate in synchronization with the switch I may be replaced by a synchronizer.

〔Effect of the invention〕

As described above, tζ, according to the present invention, since the transmission waves are spread spectrum, the transmission power density per unit frequency band can be kept low, making it difficult for the enemy to detect it.
Furthermore, even in the event of interference, correlation is established within the proximity fuze, so that it will not be affected by interference from an enemy who does not know this modulation code, and furthermore, the effective target detection range of the proximity fuze will be reduced.

Since the round-trip distance of the radio wave corresponds to the phase of one bit before and after the phase that is one bit behind the transmission modulation code, it is possible to match the target detection range with the effective range of the warhead, and it is possible to fly. When the body attempts to fly at a low altitude, the oscillation frequency of the voltage-controlled oscillator @ changes in accordance with the altitude in the downward direction of the flying body, automatically tracking the distance of the reflected waves from the ground or sea surface. Since the above-mentioned effective target detection range can be set smaller than the distance to the ground or sea surface, it is possible to prevent malfunctions due to reflected waves from the ground or sea surface. Because the received signal input power to the mixer due to reflected waves from the ground or sea surface remains constant regardless of changes in the distance to the ground or sea surface, saturation of the receiving system can be prevented. The dynamic range of the receiving system is small and the clock oscillator (
Since the oscillation frequency of (to) is constant, it is possible to ensure the same effective target detection range as when flying at high altitude, and also has the effect of being able to identify in which direction the target exists as seen from the flying object. .

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a proximity fuze according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of a flying object. Figure 3 shows the relationship between time and the output voltage of the first bias adder and the second and third detectors. Figure 4 shows the voltage. FIG. 5 is a diagram showing the relationship between the input voltage and output oscillation frequency of a controlled oscillator, and FIG. 5 is a diagram showing the configuration of a conventional proximity fuse. In figure jζ, 111 is an oscillator, (2) is a directional coupler,
(4) is the antenna, (5) is the mixer, (6) is the video amplifier, ()) is the Donpla filter # (81 is the detector, (
9) is a comparator. α1 is an ignition circuit, t12 is a modulator, (13 is a variable attenuator, No. 0 is a switch, α51 is a distributor, αe is a correlator, (1η is a bias adder, all is an AND circuit,
119 is an integrator, Tsuru is a voltage controlled oscillator, QD is a code generator, c? 3 is a 1-bit delay circuit, @ is a ΔT delay circuit,
aa is a clock oscillator, ca is a function generator, @ is a synchronizer, and gradient is an inverter. In FIG. 0, the same or equivalent parts are designated by the same reference numerals.

Claims (1)

[Claims] a voltage controlled oscillator; a first code generator driven by the output of the voltage controlled oscillator to generate a spread spectrum code; and a first code generator that generates a spread spectrum code by delaying the output of the first code generator by one bit. A bit delay circuit, a second 3-bit delay circuit generated by further bit-delaying the output of the first 1-bit delay circuit, and a minute time ΔT of 1 bit or less to output the output of the second 1-bit delay circuit. A ΔT delay circuit that generates a delay, an oscillator that generates a transmission signal, a directional coupler that branches part of the output of this oscillator, a distributor that divides the output of this directional coupler into two, and this distribution a first modulator that spread-modulates one output of the first 1-bit delay circuit with the output of the first 1-bit delay circuit; a variable attenuator that attenuates the output of the first modulator; and a variable attenuator that attenuates the output of the first modulator; a first antenna attached to the lower fuselage of the flying object for transmitting in the target direction; a clock oscillator; and a first antenna, which is driven by the output of the clock oscillator and generates a spread spectrum code different from the first code generator. 2, a third 1-bit delay circuit that delays the output of the second code generator by 1 bit, and generates the output of the third 1-bit delay circuit by delaying the output by 1 bit. a second modulator that spread-modulates the other output of the distributor with the output of the third 1-bit delay circuit; a second antenna attached to the upper part of the fuselage of the flying object that transmits in the direction; and a second antenna attached to the upper part of the fuselage of the flying object that receives radio waves transmitted in the target direction and reflected from the target by the first and second antennas. third and fourth antennas attached to the right and left parts;
a switch for switching the third or fourth antenna output; a means for mixing the output of the switch with a part of the output of the oscillator branched by the directional coupler and amplifying the video; output and the above first
a first correlator that correlates the output of the code generator, a second correlator that correlates the output of the second 1-bit delay circuit with the video amplified output, and the ΔT delay. a third correlator that correlates the output of the circuit with the video amplified output; a fourth correlator that correlates the output of the second code generator with the video amplified output; a fifth correlator that correlates the output of the fourth 1-bit delay circuit with the video amplified output; and a fifth correlator that correlates the output of the fourth 1-bit delay circuit with the video amplified output; a first to fifth detector that inputs a constant bias voltage to the output of the first detector; a first bias adder that adds a constant bias voltage to the output of the first detector; a first comparator that compares the output of the bias adder with the output of the bias adder and generates a pulse according to the comparison result; and a first comparator that compares the output of the third detector with the output of the first bias adder. a second comparator, an integrator that integrates the output of the second comparator and controls the oscillation frequency of the voltage controlled oscillator, and a second comparator that adds a constant bias voltage to the output of the fourth detector. a third comparator that compares the output of the fifth detector with the output of the second bias adder and generates a pulse according to the comparison result; and a third comparator that drives the switch. an inverter that inverts the output level of the synchronizer, and a first ignition circuit that operates a first ignition circuit only when the output of the first comparator and the output of the synchronizer are both at high level. a second circuit that operates a second ignition circuit only when the output of the first comparator and the output of the inverter are both at a high level; and an output of the third comparator. and a third circuit that operates a third ignition circuit only when the outputs of the inverter and the inverter are both at a high level, and the output of the third comparator and the synchronizer are both at a high level. A proximity fuze comprising a fourth circuit for activating a fourth ignition circuit only at certain times, and a function generator for controlling the amount of attenuation of the variable attenuator by the output of the integrator.