PROXIMITY FUSE WITH PASSIVE UNIT

Abstract: A proximity fuse for initiating detonation of the effective part of a robot, comprising a passive unit is described. It includes a first antenna means (1) for receiving electromagnetic radiation within the microwave range, having a relatively narrow first antenna lobe, and a second antenna means (2) for receiving electromagnetic radiation within the microwave range, having a second, relatively broad antenna lobe, that encloses the first antenna lobe, the first and second antenna lobes preferably being rotationally symmetric in the roll direction of the robot. The proximity fuse comprises electronic components and circuits (3-8, 10, 11) for detecting a first signal S1 from the first antenna lobe and a second signal S2 from the second antenna lobe and a first means (9) for issuing a third signal S3 for initiating a detonation of said effective part. It is in particular characterized in that the proximity fuse is arranged to issue the third signal S3 in the case where the following conditions are simultaneously satisfied: a) the quotient Z of the amplitude A1 of the signal S1 and the amplitude A2 of the signal S2 exceeds a first value Z1 determined in advance, i.e. that Z = A1/A2 > Z1, and b) the time derivative dZ/dt exceeds a second value Z2 determined in advance, i.e. dZ/dt > Z2.

Description: PROXIMITY FUSE WITH PASSIVE UNIT The present invention relates to a proximity fuse for initiating a detonation of the effective part of a robot, comprising a passive unit having a first antenna means for receiving electromagnetic radiation within the microwave range, with a relatively narrow first antenna lobe, and a second antenna means for receiving electromagnetic radiation within the microwave range, with a second, relatively broad antenna lobe, enclosing, as to the directions thereof, the first antenna lobe, the first and second antenna lobes preferably being rotationally symmetric in the roll direction of the robot, the proximity fuse comprising electronic components and circuits for detecting a first signal from the first antenna lobe and a second signal from the second antenna lobe, and a first means for issuing a third signal for initiating a detonation of said effective part. Active proximity fuses that issue and receive electromagnetic waves generated by the fuses are subject to the risk of being totally disturbed in the case where the target is equipped with strong jamming transmitters. The inclusion of a passive unit results, just in itself, in improved performance. However, proximity fuses existing up to now including a passive unit do not provide an entirely secure operation and can in certain cases initiate a detonation at a large distance of the target. It may also occur that escorting airplanes give false ignition pulses. The object of the present invention is therefore to provide a proximity fuse of the kind mentioned in the beginning, providing a secure operation also in the case where the target or escorting airplanes issue more or less strong interfering signals. According to the invention such a proximity fuse is primarily characterized in that the proximity fuse is arranged to issue the third signal in the case where the following conditions are simultaneously fulfilled, i.e. that both the quotient of the amplitude of the first signal and the amplitude of the second signal exceeds a first value determined in advance and that the time derivative of said quotient exceeds a second value determined in advance. In a preferred embodiment of this proximity fuse according to the invention it is arranged to emit the third signal in the case where in addition the amplitude of the first signal exceeds a third value determined in advance. Actually, it can be possible to use a proximity fuse including only a passive unit but often a proximity fuse is preferred that also comprises an active unit having a first transmitter for issuing modulated electromagnetic radiation within the microwave range and a first receiver for receiving the portion of this radiation that is reflected from a target, the radiation being issued and received by a third antenna means within a relatively narrow, third antenna lobe which is a preferably rotationally symmetric in the roll direction of the robot, and further comprises a second means for generating a fourth signal in the case where the target detecting conditions in the active unit, that are based on parameters such as distance value, signal amplitude, doppler frequency, are satisfied. In this case a proximity fuse according to the invention is primarily characterized in that the proximity fuse is arranged to issue the third signal in the case where at least one of the following conditions is satisfied: either the fourth signal is generated, or that both the quotient of the amplitude of d e first signal and the amplitude of the second signal exceeds a first value determined in advance and that the time derivative of said quotient exceeds a second value determined in advance, or that in addition the amplitude of the first signal exceeds a third value determined in advance. The characteristics mentioned above of three embodiments of the proximity fuse according to the invention are defined in the appended claims numbered 1 - 3 and additional embodiments appear from the claims numbered 4 - 11. The invention will be described in the following in greater detail with reference to the accompanying drawings showing block diagrams of a principle nature according to the following: Fig. 1 shows a first embodiment of the proximity fuse according to the invention, only including a passive unit, having a directly detecting receiver, Fig. 2 shows a second embodiment of the proximity fuse, also only including a passive unit, but having a heterodyne receiver (local oscillator and mixer), Fig. 3 shows a third embodiment of the proximity fuse, having an active unit combined with a passive unit according to Fig. 1, Fig. 4 shows a fourth embodiment of the proximity fuse, having an active unit combined with a passive unit according to Fig. 2, Fig. 5 shows a fifth embodiment of the proximity fuse, having an active unit comprising a band pass filter and an envelope detector, combined with a passive unit according to Fig. 1, Fig. 6 shows a sixth embodiment of the proximity fuse, having an active unit comprising a band pass filter and an envelope detector, combined with a passive unit according to Fig. 2, and Fig. 7 shows a longitudinal sectional view through the point of a robot including rotationally symmetric first and second antenna lobes. The first, relatively simple embodiment of the proximity fuse according to the invention thus appears from Fig. 1. In it a first antenna means having a relatively narrow, first antenna lobe, is denoted by 1 and a second antenna means having a second, relatively broad antenna lobe, by 2. For die sake of clarity it is not illustrated in the figure that the second antenna lobe encloses tiie first one but tfiat is true. The antenna lobes are preferably rotationally symmetric in the roll direction of a robot and directed somewhat forwards. This is an advantageous embodiment, though other ones are conceivable. The signal from the first antenna means 1 passes through a unit including a bandpass filter 3, an envelope detector 4 and an amplifier 5 and thus proceeds, in the shape of a first signal S 1 both to a first signal processing unit 9 and to a quotient forming unit 10. The signal from the second antenna means 2 passes through another unit, including a bandpass filter 6, an envelope detector 7 and an amplifier 8 and thus proceeds, in the shape of a second signal S2, to said quotient forming unit 10. The signal Z from the quotient forming unit is supplied both to said first signal processing unit 9 and to a derivative unit 11, from which the signal dZ/dt is also provided to the signal processing unit 9. Therefrom a third signal S3 can be fed to an effective part, not shown, of the robot and initiate a detonation thereof in the case where the conditions set out in claim 1 are satisfied, i.e. that the quotient Z of the amplitude Al of the signal SI and the amplitude of the signal S2 exceeds a first value Zl determined in advance and in addition that the time derivative dZ/dt exceeds a second value Z2 determined in advance. In this embodiment some security is obtained that only jamming transmitters in the target which are located near by, can initiate a detonation of the effective part, interfering signals from escorting or more remote airplanes not being able to achieve this effect. As a further condition it can be added that the amplitude Al of the first signal is in addition to exceed a tirird value Z3 determined in advance. However, it is possible to increase the sensitivity of the proximity fuse by introducing a heterodyne receiver including a HF-oscillator, two mixers and two envelope detectors according to Fig. 2. Thus, here the signal from the first antenna means 1 also in this case proceeds to a bandpass filter 3 but then to a mixer 13 where it is mixed with a local oscillator signal from a HF-oscillator 12, after which the resulting signal continues to a bandpass filter/amplifier 15 and then passes to an envelope detector 4, and then it proceeds, as in the first embodiment, in the shape of a first signal SI both to the first signal processing unit 9 and to the quotient forming unit 10, etc. In the corresponding manner the signal from the second antenna means 2 passes to the bandpass filter 6, after that to a mixer 14, where it is mixed with a local oscillator signal from the HF-oscillator 12, after which the resulting signal continues to a bandpass filter/amplifier 16 and an envelope detector 7 and therefrom, in the shape of a signal S2, proceeds to the quotient forming unit 10. If the passive unit of the proximity fuse is combined with an active unit as is illustrated in a tiiird embodiment of the proximity fuse according to the invention in Fig. 3, the performance thereof can be improved. The passive unit is here identical to tiiat in the first embodiment in Fig. 1. The first antenna means is here referenced la and the bandpass filter has here been denoted by 3a. The active unit has a third antenna means 17 for issuing modulated electromagnetic radiation for an active search of targets. This radiation is provided by an HF-oscillator 18 that is modulated by a modulator 19. The signal from the HF-oscillator proceeds together with a signal from the low pass filter 3a to a mixer 20, from which the resulting signal is fed to a second signal processing unit 21. It outputs, in the case where the target detecting conditions based on parameters such as distance value, signal amplitude, doppler frequency, are satisfied, a tiiird signal S4 that passes to the first signal processing unit 9, together with said first signal SI, the signal Z and the signal dZ/dt. As appears from claim 3, the third signal S3 is issued for initiating a detonation either in the case where the signal S4 is generated or the conditions according to claim 1 are satisfied, or in the case where the conditions according to claim 2 are satisfied. The operation of the active unit can be assigned a priority by arranging a threshold of the amplitude Al of the first signal, i.e. determining that it is to exceed a certain value AL, in order that the passive unit is to generate a detonation. It is defined in claim 4. Proximity fuses having an active unit can also, in a third embodiment that appears from Fig. 4, be designed including a passive unit according to Fig. 2. Compared to the third embodiment the signal from the bandpass filter 3 only passes through the mixer 20, the signal therefrom also being supplied to the passive unit. The mixer 14 of the passive unit receives, in addition to the signal from the second antenna means 2 through the bandpass filter 6, also a local oscillator signal from the HF-oscillator 18 of the active unit. In a fifth and a sixth embodiment of the proximity fuse according to Figs. 5 and 6 the active unit is provided with a bandpass filter 22 arranged in series with an envelope detector 23, through which a signal passes from the first antenna means, through the mixer 20, in addition to its travel to the second signal processing means 21. In this way it is obtained, in addition to the fourth signal S4, a fifth signal S5, the amplitude of which is related to the amplitude of an occurring jamming or disturbing signal, i.e. the disturbance amplitude of the pass band. This signal S5 passes to the first signal processing unit 9. As is defined in claim 5, a detonation is initiated either in the case where the signal S4 is generated, or that the conditions of claim are satisfied combined with the condition that the amplitude A5 of the signal SS exceeds a value AM determined in advance, that is determined considering die probability that the target detecting conditions are satisfied. The pass band of the bandpass filter 22 preferably covers a frequency band that at least includes the frequency range of d e issued, modulated electromagnetic radiation, the bandpass filters 15, 16, 3a and 6 preferably covering a broader frequency band. In the fifth embodiment according to Fig. the passive unit is the kind illustrated in Fig. 1, and in the sixth embodiment the passive unit corresponds to that of Fig. 2, i.e. including a heterodyne receiver. The antenna arrangements can, within the scope of the invention, be designed in many different ways. As is defined in claims 6 - 10 the passive and active unit can, actually, have separate antennas but they can also be combined, being arranged to perform d e required operations. It is suitable to construct the antenna means as array antennas. In Fig. 7 a longitudinal sectional view is illustrated of die point of a robot 24comprising first and second antenna lobes 26, 27, that are rotationally symmetric about an axial symmetry axis 25. In the same way electronic components and circuits for generating and detecting microwaves and for signal processing respectively included in the passive and active unit can at least partly be shared or common. Parts of the signal processing can also be made digitally, the signals being A/D-converted and d e analogue circuit functions being performed using equivalent program algorithms. The embodiment described above presupposes that bandpass filters of a relatively broad band type are used. An alternative is to replace diem with a filter bank of narrow band filters, which is each one followed by an envelope detector comprising me following signal processing 10, 11, 9. The signals SI, S2, ... , S5 and Z, dZ/dt are then replaced with vectors of die same dimensions as die filter bank. In a digital implementation the filter bands and d e operations thereof can be substituted by for example FIR-filters or FFT-algorithms.

Claims: Claims 1. A proximity fuse for initiating a detonation of the effective part of a robot including a passive unit comprising: a first antenna means (1) for receiving electromagnetic radiation within d e microwave area, having a relatively narrow, first antenna lobe, and a second antenna means (2) for receiving electromagnetic radiation within the microwave area, having a second, relatively broad antenna lobe, this lobe as to the direction enclosing a first antenna lobe, the first and second antenna lobes preferably being rotationally symmetric in the roll direction of the robot, d e proximity fuse comprising electronic components and circuits (3-8,10,11) for detecting a first signal SI from the first antenna lobe and a second signal S2 from the second antenna lobe, and a first means (9) for issuing a third signal S3 for initiating a detonation of said effective part, c h a r a c t e r i z e d i n that the proximity fuse is arranged to issue the third signal S3 in the case where d e following conditions are simultaneously satisfied: a) d e quotient Z of d e amplitude Al of the signal SI and the amplitude A2 of die signal S2 exceeds a first value Zl determined in advance, i.e. Z = A1/A2 > Zl. b) the time derivative dZ/dt exceeds a second value Z2 determined in advance, i.e. that dZ/dt > Z2. 2. A proximity fuse according to claim 1, c h a r a c t e r i z e d i n that d e proximity fuse is arranged to issue the third signal in the case where in addition the amplitude Al of the signal SI exceeds a tiiird value Z3 determined in advance, i.e. that Al > Z3. 3. A proximity fuse according to claim 1 or 2, also comprising an active unit (3a, 17-21) having a first transmitter for issuing modulated electromagnetic radiation witiiin the microwave area and a first receiver for receiving a portion of this radiation reflected from a target, the radiation being issued and received by a third antenna means (17) within a relatively narrow, third antenna lobe, that is preferably rotationally symmetric in die roll direction of the robot, and further comprising a second means (21) for generating a fourth signal S4 in die case where in die active unit the target detecting conditions based on parameters such as distance values, signal amplitude, Doppler frequency, are satisfied, characterized in that de proximity fuse is arranged to issue die third signal S3 in the case where at least one of the following conditions is satisfied: c) the signal S4 is generated. d) the conditions according to claim 1, e) the conditions according to claim 2. 4. A proximity fuse according to claim 3, characterized in tivat me proximity fuse is arranged to issue the third signal S3 in the case where at least one of the following conditions is satisfied: f) die signal S4 is generated g) the conditions according to claim 1 combined with the condition that the amplitude Al of de signal SI exceeds a value AL, i.e. tiiat Al > AL, AL being determined to have such a large value tiiat a priority state of the condition f) to the condition g) is normally true. 5. A proximity fuse according to claim 3, in the case where the active unit comprises a bandpass filter, a fifth signal S5 being generated, the amplitude of which is related to the amplitude of an existing disturbing or jamming signal, i.e. the amplitude of the pass band, characterized in tiiat die proximity fuse is arranged to issue the third signal S3 in the case where at least one of the following conditions is satisfied: h) the signal S4 is generated, i) the conditions according to claim 1 combined with the condition that the amplitude A5 of the fifth signal S5 exceeds a value AM determined in advance, i.e. that A5 > AM, AM being determined considering the probability that the target detecting conditions are satisfied. 6. A proximity fuse according to one of claims 3-5, characterized in that said tiiird antenna means has separate means for a transmission and reception respectively. 7. A proximity fuse according to one of claims 3-5, characterized in tiiat the tiiird antenna means has common antennas for transmission and reception respectively. o 8. A proximity fuse according to one of claims 3-7, characterized in tiiat die operation of said third antenna means is accomplished by said first antenna means. 9. A proximity fuse according to one of claims 1-8, characterized in that the function of at least some of said antenna means is performed by at least partiy common antennas. 10. A proximity fuse according to one of claims 1-9, characterized in that at least one of said antenna means is constituted of one or several array antennas. 11. A proximity fuse according to one of claims 3-10, characterized in that in electronic components and circuits for generating and detecting microwaves and for signal processing respectively included in the passive and active unit are at least partly common for said passive and active units.

Inventors: AXELSSON SUNE, AXELSSON, SUNE
Applicants: SAAB MISSILES AB
Application year: 1995
Main classification: F42C13
IPC codes: F42C13