DE2448898C1 - Radar or laser based proximity detonator for shell or rocket - Google Patents

Abstract

The detonator uses evaluation of reflected radiation using a doppler effect for detonating an explosive charge at a given proximity to a target object, the ignition criteria provided by a given doppler frequency being reached. The detonation signal is provided by a digital phase comparator coupled to a doppler frequency oscillation source and to a digital reference frequency generator, supplying the given doppler frequency. A logic circuit acting as an interference block is inserted between the reference frequency generator and the phase comparator, with a second input coupled to the doppler frequency oscillation source, for blocking the signals from the reference frequency generator upon failure in the output signals from the doppler frequency oscillation source.

Description

The invention relates to a proximity fuse according to the Oberbe handle of claim 1. The retroreflective measurements take place at Igniter according to the invention preferably by the radar method, can In principle, however, it is also carried out using a laser device will. A generic igniter is in the older patent 24 35 949 have already been proposed.

A disadvantage of the proposed igniter is the possibility that temporarily - due to interference-induced signal dips - off falling Doppler signals a premature ignition occurs.

The invention has for its object a detonator of this type  specify which is dependent on the relative approximation ge speed to its target and from the splinter speed of your own grenade or missile, even then twists when dips into the Doppler due to interference vibrations occur, which may be temporary Failure of output signals from the Doppler frequency vibration source.

The features of a gat solving this task Appropriate igniter can be found in claim 1. The Sub-claims contain the features of advantageous embodiment shapes and developments of the invention.

Fig. 1 shows - as far as necessary to explain the invention - the block diagram of an embodiment of the invention. The high-frequency part with Doppler frequency amplifier of this exemplary embodiment is not shown in FIG. 1 because it is known per se and is not itself the subject of the invention; "from the RF part" indicates this Doppler frequency vibration source, which gives the Doppler signal of the frequency f _D in digitized vorm, at the same time to a D / A converter and an input of a phase comparator PC. The Inter interference lock shown in Fig. 1 initially remain out of consideration, since it is described in more detail below. First of all, it is rather assumed that the other input of the phase comparator PC is connected directly to the output of a reference frequency generator which, in the example according to FIG. 1, from the series circuit shown of the aforementioned D / A converter with a function generator, a memory and on the output side a voltage-controlled one (VCO) oscillator G exists and its output frequency is the given Doppler frequency of the ignition criterion. Since the phase comparator at the detonator according to FIG. 1 is a digital phase comparator, its input signal from the reference frequency generator is likewise supplied to it by appropriate training in a digital vorm.

In the case of target acquisition, which generally occurs at a target distance that is comparatively large for the ignition distance, the frequency f _{D is} the maximum possible Doppler frequency f _Dmax , because then the line of sight between the detonator and the target is practically the same direction and coincides with the detonator trajectory. The D / A converter always converts the instantaneous Doppler frequency into a voltage U _fD that is proportional to it, which is changed by the function transmitter so that the subsequently controlled generator (VCO) oscillates at the ignition frequency, which is explained in more detail below becomes. The ignition frequency is supplied in digital form to the digital phase comparator PC, which is an edge-controlled digital memory circuit consisting of four flip-flops and control gates and is likewise explained in more detail below. If the detonator continues to approach the target, the Doppler frequency f _D decreases to zero until it passes the target and then rises again, provided that the detonator does not ignite beforehand. The phase comparator compares the ignition frequency given by the reference frequency generator with the Doppler frequency that is directly supplied to it as the approximation becomes smaller and emits the ignition signal as soon as the instantaneous Doppler frequency falls below the ignition frequency, whereby in practice there is typically only one ignition signal delay (due to a switching time of two Doppler half waves) on the order of µs.

This delay-free signal evaluation is with the Er object of the invention an optimal ignition even with very dense ones Flying past at a target distance of less than 1 m possible, what in the case of proximity detonators belonging to the prior art, in particular especially those with analog evaluation is not guaranteed; the known detonators ignite in such a small flyby  experience has shown that distances are much earlier than in your opti paint ignition timing.

The detonator according to the invention, in particular its phase compa rator and reference frequency generator (ignition frequency source) easily implemented in IC technology and therefore small, cheap and acceleration-resistant.

Fig. 2 is used to explain the ignition geometry of the fuse according to the Invention. For a given splinter speed v _S , each value of the relative speed V _R between the detonator and the target is assigned a specific ignition angle α _Z according to tg α _Z = v _S / v _R. Since v _a = v _R. cosα, the approach speed V _aZ at the ignition point results

The course of this function v _aZ = f (v _R ) for v _S = 1000 m / s is shown in FIG. 3.

The function generator in the example according to FIG. 1 has the task of emulating this function - transferred into proportional voltage values. According to the exemplary embodiment in FIG. 4, it expediently comprises the voltage divider R1 / R2 and the Zener diode D1. The diode D2 and the capacitor C according to FIG. 4 form an advantageous exemplary embodiment for the memory in FIG. 1.

The target acquisition gives (because of α ≈ 0) U _fD = U _fDmax ∼ v _R. This value is immediately converted in the function generator into the voltage U _Sp ∼ f _DZ ∼ v _aZ and stored in the memory. In the fol lowing VCO, the ignition frequency is produced from U _Sp .

In the embodiment of the invention according to FIG. 1, the interference barrier already mentioned briefly above and not previously considered is provided in the sense of the invention, which prevents misfires as a result of Doppler signal dips by providing a missing Doppler signal at the input of the scarf shown in FIG. 1 device keeps reference frequency signals from the ignition frequency channel away from the phase comparator. An advantageous implementation of this interference barrier can be seen in FIG. 5, in which the circuitry of the interference barrier is delimited by a dashed box. In Fig. 5 is also a conventional Differen ornamental element from a capacitor C and an ohmic resistor R can be seen, which performs the differentiation of the output signals of the oscillator VCO ( Fig. 1) in the sense of digitization. 5 at the output of the phase comparator is shown in FIG., A load resistor R _L, over which the firing signal appears.

Fig. 6 shows a known and advantageously usable as a phase comparator of the arrangement of FIG. 1 digital phase comparator, which is described in detail for example on pages 2 and 3 with reference to phase comparator II in the publication ICAN 6101 with regard to structure and mode of operation. This document was published in 1972 by the RCA company.

The phase comparator according to FIG. 6 is an edge-controlled digital storage network. It consists of four bistable stages, control circuits and an output circuit which can assume three states and contains p and n driver stages with a common output 13 . This phase comparator only reacts to the positive edges of its digital input signals at inputs 3 and 14 . If the input frequency at 3 is higher than that at 14 , the output part of the comparator denoted by p is constantly in its switched-through state. If the reverse input frequency relationships are present, on the other hand, the output part denoted by n is constantly driven. If the input frequency at 3 and 14 match, but there is a phase difference between the two input signals, there are also three output states of the phase comparator, which can be varied as a result of positive edges of the signals at connection 3 and 14 according to the following table; see. see also FIG. 6.

State B is fixed to D = O by external resistor R _L.

The digitized Doppler signal A is offered in the form that both the positive and the negative half-wave of the analog signal - if a certain threshold value is above or above is undershot - appears as logical L You get there by doubling the frequency.

The comparison signal B is obtained by differentiating the VCO-Sig won. The frequency corresponds to twice the ignition frequency quenz.  

The interference barrier has the task in the absence of a Doppler signal A the pulses of the comparison frequency (signal B or C) keep away from the phase comparator. With each pulse of the Sig Nale B is checked whether A = L. Only then does signal C appear. This creates very fast interference fade out.

When approaching the target, the Doppler frequency is initially higher than the comparison frequency. The output of the phase comparator assumes states A and B, i.e. H. D = O. If the The state becomes Doppler frequency below the comparison frequency achieves that within an interval of signal A two Pulses of the comparison frequency (B or C) on the phase comparator issue. This will make D = L (condition C) and the ignition will initiated.

The further development of the invention described below he then proves itself in comparison with the prior art partial if aircraft by means of the invention Proximity igniter to be fought and with disorders of the detonator by ground clutter is to be expected, for example in low-flying combat. Depending on the nature of the soil and after flight altitude, reflections of the transmission waves can on Pretend ground detonator approaches to a target.  

This further development of the invention is simultaneous the ECM strength of the igniter is significantly increased. A sturgeon To be successful, the transmitter must take several milliseconds with sufficient power, the interference frequency with a Ge radiate accuracy of 0.01 ‰, which is practically immense May cause difficulties.

As is known in radar technology, the ground clutter power N typically has a distribution according to FIG. 7. The following abbreviations are used in this figure.

A = reception power required for evaluation
f _A = Doppler frequency of the ground clutter to be measured without ground clutter suppression
f ₂ = comparison frequency
f _Do Doppler frequency of a resting target

Requires z. B. a proximity detonator the received power A, then the evaluation circuit measures the Doppler frequency generated by: Boden f _A. If you prevent a circuit that only frequencies greater than f ₂ can be evaluated (the reception power at f ₂ does not reach the response threshold), then the disturbances of the ground clutter are ineffective.

FIG. 8 also shows, similarly to FIG. 7, the spectral distribution of the ground clutter for a proximity igniter moving horizontally above the earth's surface, the clutter limit f _Do corresponding to that Doppler frequency that the igniter's own speed v _{g is} proportional to.

The block diagram of FIG. 9 relates to an advantageous embodiment according to a development of the invention, which largely corresponds to the example of FIG. 1 according to the upper part of FIG. 9. This development of the invention is characterized in that for suppressing any disturbing ground clutter signals in the Doppler channel of the detonator and / or for increasing its ECM strength, a voltage comparison circuit (comparator) is provided, which is one of the instantaneous Doppler frequency of the received vibrations compares proportional voltage with a function transmitter voltage (function transmitter 2 ) and which prevents the generation or delivery of the ignition signal as long as the voltage proportional to the Doppler frequency of the received oscillations is less than the function transmitter voltage, the function transmitter voltage always being smaller than and of the same order of magnitude 0.9 -fold voltage, which is proportional to that Doppler frequency that would result from the instantaneous flight speed of the detonator.

FIG. 10 shows further details about expedient implementation possibilities of the voltage comparator and function generator 2 of the arrangement according to FIG. 9.

Since the frequency measurement circuit works broadband, that is, it has an integral character, if clutter signals of sufficient amplitude are present, a voltage U _{fD will be} set at the output of the D / A converter, which corresponds to an effective clutter frequency; see. Fig. 11. This is much lower than f _D0 . In the comparator, the resulting voltage U with a reference voltage U _{fD see} that about 0.9 is now. f corresponds to _D0 . In the case of U _fD <U _cf. the VCO is blocked, so that ignition is impossible. If a useful signal is present from a stationary or approaching target, U _{fD increases} to the value corresponding to the relative speed v _R. Now U _fD < _{U see} , the VCO is released and the phase or frequency comparison can begin.

The clutter edge f _D0 or the airspeed v _g decreases continuously over the flight time after an e-function. In order to be able to correctly detect between target and clutter signals, the reference voltage must also decrease accordingly. This is done by the function generator 2 ( Fig. 9). The function of the same can be seen from Fig. 10. When the device is U _cf. equal to the breakdown voltage V _Z of the Zener diode (capacitor C is discharged). With increasing flight time C is such that U _cf. decreasing function over R e up load after a.

Regarding disturbance of the device by ECM measures, the requirement applies that the disturbance signal must be present for approx. 5 ms with a frequency between f _S + f _D0 and f _S + f _Dmax . The time of 5 ms is required to load the memory.

Claims (8)

1. Proximity detonator, which ignites the explosive charge in a grenade or missile when approaching a target object by evaluating ongoing retroreflectivity measurements using the Doppler effect, in which the predetermined ignition criterion is the reaching of a given Doppler frequency, in order to determine the ignition criterion and generating the ignition signal, a digital phase comparator with two inputs is provided, one input of which is connected directly to the Doppler frequency oscillation source, which emits the Doppler signal in digitized form, and the other input of which is also connected to a likewise digital reference frequency generator, the output frequency of which in turn is the predetermined Doppler frequency of Ignition criterion is characterized in that between the reference frequency generator and the phase comparator is inserted an interference barrier consisting of a logic circuit with two inputs, one input of which at the reference frequency generator tor and their other input to the Doppler frequency vibration source lie and which prevents signals from the reference frequency generator from reaching the phase comparator in the absence of an output signal from the Doppler frequency vibration source. 2. Detonator according to claim 1, characterized in that the Doppler frequency vibration source is designed such that at its off  the positive as well as the negative half wave of the ana Logen Doppler signal appears as a logical L, and that the off gearing vibration of the reference frequency generator also fre is doubled in number. 3. Detonator according to claim 1 or 2, characterized in that the Reference frequency generator from a voltage controlled oscillator (VCO), whose control voltage consists of a battery or a voltage storage, e.g. B. a charged capacitor and which is followed by a differentiator. 4. igniter according to claim 3 with a storage capacitor as a control Voltage source, characterized in that for charging the condenser sators a function generator is provided which when approaching the Target object during the time of occurrence of Doppler vibrations keeps the capacitor voltage at the level required for the oscillator to generate the frequency corresponding to the ignition criterion is such. 5. Detonator according to claim 4, characterized in that the radio tion generator from the series connection of two ohmic resistors against ground and a Zener diode, which is the input side Resistor is in parallel, and that the output signal of the function is removable above the output side of the two resistors. 6. igniter according to claim 4 or 5, characterized in that the Capacitor is connected upstream of a diode.   7. Igniter according to one of claims 1 to 6, characterized in net that the phase comparator consists of four bistable circuits, Control gates and an output circuit that can assume three states and that it is known as a result of itself Interconnection of its components in connection with the area code its load resistance only on the positive edges of its digital reception signals responds in such a way that it delivers the ignition signal when the ignition criterion is met. 8. Detonator according to one of claims 1 to 7, characterized in that a voltage comparison circuit (comparator) is provided to suppress any disturbing ground clutter signals in the Doppler channel of the detonator and / or to increase its ECM strength compares the instantaneous Doppler frequency of the receive vibrations per proportional voltage with a function transmitter voltage (function sensor 2 ) and which prevents the generation or delivery of the ignition signal as long as the voltage proportional to the Doppler frequency of the receive vibrations is lower than the function transmitter voltage, the function transmitter voltage always being smaller than and the correct size is equal to 0.9 times the voltage, which is proportional to that Doppler frequency, which would result from the instantaneous flight speed of the detonator.