IL33982A - An airborne homing system - Google Patents

Description

33982 /2 nooizn nn"iao nmya An airborne homing system BLBCTRONIQUE MARCEL DASSAUU 0/ 32242 ¾he invention relates to an airborne homingV system and method.

In a distance homing radar the radar echo is compared in a discriminator with telemetering windows} the signal provided by the discriminator which represents the acceleration of the target with respect to the radar is applied to a first integrator, providing a voltage representing the speed, said voltage being applied to a second integrator whose output is a voltage representing the distance. $he telemetering windows are obtained by comparison of said last mentioned voltage with a sawtooth voltage released by the radar emission signal.

In such a radar, the precision is not as high as desired owing on one hand to the integrators whose operating conditions vary and on the other hand to the disturbances which are carried in the sawteeth when there is an unintentional variation in the feeding voltage.

According to the present invention there is provided an airborne homing system for a craft carrying an explosive charge, comprisingJ radar means for determining variations in the distance between the craft and a target; computer means including a memory initially connected to said radar means for establishing a progressively diminishing distance indication upon the craft approaching said target; a first comparator in the output of said computer means for generating a switching signal upon said distance indication assuming a first predetermined value? switchover means responsive to said switching signal for disconnecting said computer means from said radar means while preserving data stored in said memory to provide said distance indication independently of said radar means; and a second comparator in the output of said computer means for generating a firing pulse for the detonation of said charge upo said distance indication assuming a second predetermined value.

The invention will he fully understood from the description which follows made with reference to the accompanying drawings in which? Figure 1 is a block diagram of a telemetering apparatus according to the invention; Figure 2 is a block diagram of a part of the telemetering apparatus; Figure 3 is a block diagram of part of the apparatus for an embodiment; Figure 4 is a block diagram of part of the apparatus for an embodiment; Figure 5 is a block diagram similar to the one shown in Figure 1; Figure 6 is a block diagram of an apparatus according to the invention; - Figure 7 is a block diagram of part of said apparatus, - Figure 8 is also a block diagram of part of said apparatus ■-, Reference is first made to Figure 1. The discriminator 10 receives the radar echo from the lead 11 and the telemetering windows from the lead 12 . The signal on output 14 of the discriminators which represents the acceleration of the target is applied to an integrator 15 · At a second input 16 of the integrator 15 can be applied a voltage which represents an acceleration. The voltage on the output 17 of the integrator 15 which represents the relative speed of the target is, according to the invention, applied to a distance increments generator or incrementor 18 which produces a voltage represented by a straight line the slope of which is proportional to the amplitude of the voltage at its input. When said voltage reaches a predetermined value, it returns to zero and the incrementor then provides a pulse at its output 19, the voltage provided by the incrementor then grows again linearly up to the predetermined value when a new pulse is emitted on output 193 etc.. The freq ency of the pulses on output 19 from the incrementor is thus representative of the value of the input voltage. The pulses provided by the incrementor are introduced into a counter register or distance memory register 2 1 , the combination of the incrementor and the register forming an integration device. The contents of the register 2 1 represents the distance to the target. The output 22 can be used for displaying purposes.

The distance memory register 2 1 is associated with a shift register 23 to which it is connected by a line *1 controlled by means of a gate 25 to which the operating signal is carried by a lead 26 . The operating signal comprises a transfer ulse provided by the radar emitter at an instant between the pilot pulse of the emitter and the hyper-frequency or top-emission pulse ; this can be, for example, the pulse applied to the thyratron of the emitter. Upon the arrival of the transfer pulse, the register 23 is filled and its contents reproduces the contents of the register 21. The shift of the register 23 is effected by pulses provided by an electronic clock 27, preferably quartz controlled, and carried along a lead 28 on which is a gate 29. The gate opens upon the application of the "top-emission" carried by the conductor 31.

To the shift register 23 is associated a decoder 32 providing at its output 33 a pulse for the zero contents of the register 23· This pulse is used in a device 30 for the customary generation of the telemetering windows applied by the lead 12 on the discriminator 10.

The device of Figure 2 shows means used for directly obtaining two telemetering windows. To the shift register 23 is associated not only a decoder 32 providing a pulse for indicating the zero value of the register s but a second decoder 3*1 providing a pulse at its output 35 when the contents of the register 23 is equal to the width of a telemetering window, for example + x, and a third decoder 36, providing a pulse when the contents of the shift register is - x. A bistable 38 is operative upon arrival of a pulse on conductor 35 connected to the output of decoder 34 and in the opposite direction upon arrival of a pulse on conductor 33 from the output of the decoder 32. A second bistable 39 takes, upon arrival of a pulse via conductor 33, the same condition as bistable 3 upon arrival of a pulse on conductor 35, and takes its other condition when it receives a pulse via conductor 37 of the output of the decoder 36. The outputs 41 and 42 of the bistables 38 and 39 are the telemetering windows which are Initially, a distance can be introduced into the register 21.

An appropriate value of acceleration can be introduced via lead 16.

A value of speed can be introduced by the input *i0 of the incrementor.

The frequency of the clock and the increments provided by the distance incrementor are connected to one another so that the contents of the distance register are of a suitable scale. For example, the clock may have a frequency of 200 MHz and the value of the increments may be 0.75m.

According to the invention, the pulse applied by the lead 31 to the gate 29 is generated from the "top-emission" not by applying the same directly on the gate 29 but by means of the F stage 41 (Figure 3) of the receiver and the video stage k2 , the lead 31 being connected to an output ^3 of the video stage. The variations in transmitting conditions in said stages are thus avoided, their influence on the echo being the same as that on the pulse controlling the shift of the counter.

A radar according to the invention which can be classified as digital is of simpler construction than that of a conventional homing radar but is of substantially increased accuracy. Such a radar avoids the difficulties of conventional radar linked with the sawtooth generator and with the analogi-cal integrator for determining the distance.

Reference is now made to Figure Ί . The radar emitter 50 sends a hyper-frequency signal in space by the antenna 51. The echo radar reaches the receiver 52 via conductor 53 where it is processed by the MF stage 54 and the video stage 55, whose output is applied to the position discriminator 6 vrhich receives on the other hand the telemetering windows via leads channel 60 a voltage which is a function of a distance resulting from the first integration in the integrator 6l and of the second integration in the second integrator 62. A second input 63 for the comparator 59 provides a voltage from a sawtooth generator 6^ which is operated starting at the "top-emission" which is applied to the generator 59 via lead 65.

According to the invention , a comparator 66 s the input channel 57 of which receives the voltage representing the distance, receives on its other input 68 a known voltage, so that the comparator provides a signal at its output 69 when the distance generated by the chain comprising the integrator devices assumes, during the tracking, a predetermined value. This pulse is used to put the apparatus in a second operating condition, i.e. the memory condition, in which the distance is provided by integrator 62 from stored speed values, and which are for instance those provided by integrator 6l during the time period preceding immediately the commutation.

The distance voltage assumes values which correspond to a progressive diminution of the distance and these values are applied by an input 70 to a comparator 71 which receives on its other input 72 a voltage which corresponds to a predetermined value of the distance, for instance, the zero value. When the comparison shows that the voltage on the input 70 is equal to the voltage on the input 72, a pulse is delivered at the output 73 of the comparator, and the pulse can be used to fire an explosive charge. Such a device operates as a proximity fuze. It obviates the difficulties due to the parasitic echoes, or to the "image" of the missile during a low altitude flight, especially above Reference is now made to Figure 5. The integrator 80 can be connected by a switch 8l to the discriminator 82, or else may operate^ as a memory device, In the first condition, integrator 80 provides at its output 83 a voltage repre senting the speed of the missile carrying the apparatus with respect to a target, by means of a distance increment generator 84, also called incrementator, followed by a distance register 85. An output 86 of the register is connected to a decoder 8f which provides at its output 88 a switching order when the distance appearing in the register 85 becomes. during its diminution, equal to a predetermined value.

After this switching, the apparatus functions in open-loop, starting with the value of speed stored in the memory of the device 80 at the moment of switching and upon which can act a second accelerometric input 89. The register 85 is connected by a channel 90 to a second decoder 91 which provides at its output 92 a firing order when the distance recorded in the register 85 reaches a determined value, for example the zero value.

The speed memory device 80 can also be used when the apparatus is in the condition assuring its functioning as homing or tracking radar, for example in the case of tempo rary disappearance of the echo or when it has been jammed. It can be controlled by a device sensitive to jamming which is thus without any undesirable effect.

A systematic passage to the operation calling upon the speed memory in response to certain prescribed uses can also be provided.

Referring next to Figure 6. In this embodiment, on the distance memory register 101 acts not only the output 102 of the distance increment generator 103, but also via lead channel 106 the pulses which are provided by a decounting device 107.

The counting device 105 counts and t¾e decounting device 107 decounts the pulses provided by a sequencer 108. The sequencer 108 receives at its input 109 regular tine successive pulses which can be provided for example by the clock 110 which is provided to produce the decounting pulses for the shift register 111 disposed in the distance tracking chain or else another clock. The sequencer device 108 is appro-priate to provide pulses which can be of a frequency different from that of the pulses provided by the clock 110. The frequencies on the outputs 98 and 99 of the sequencer can differ from one another.

The counting pulses and the decounting pulses origi-nating from devices 105 and 107 are further applied to the inputs 113 and 11*1 of a searching counter 115 which controls by means of a low stop 116 and a high stop 117 and a bistable 118, by the outputs 119 and 120 of the bistable, the coining into operation of the counting device 105 and the decounting device 107 vrhen the distances introduced into the register 101 by the inputs 104 and 106 reach predetermined values. The order to search is provided to the sequencer 108 by the input 121.

An input 122 s by and initiating signal, permits the introduction into the distance memory register 101, by means of the counter 115 a of a predetermined distance from which the search is started.

When the apparatus is in the searching condition owing to the order transmitted via the channel 121, the register 101, causes, by means of the shift register 111, the displacement of the telemetering windows generated in the device 123 starting from the distance corresponding to the initiating signal applied via lead 122 and this as a function of the pulses which are transmitted first to it, for example by the counting device 105, to which corresponds a predetermined direction of displacement of the telemetering windows and then by means of a stop, for example the high stop 117, and the bistable 118 and, in the other direction, under the effect of the pulses which are provided by the decounting device 107 and that until the intervention of the other stop, the low stop 116 in the example, and the bistable 118 which renders inoperative the decounting device 107 and again renders operative the counting device 105, etc.. In the case wherein the pulse frequencies provided by the counting device 105 and the decounting device 107 are different, the displacement of the telemetering windows is made at a speed different in one direction and in the other.

At the outset of the search, the bistable 118 inhibits the decounting device 107 and permits by the inpwfc 119 the operation of the counting rievio© 105. The counting device 105 receives via input 98 a series of pulses and directs this series simultaneously to the input 113 of the searching counter 115 and to the input lOU of the register 101 During each recurring period defined by the radar synchro applied at the input 128, the contents of the searching counter 115 and the distance memory register 101 increase by c distance increments. As soon as the contents of the sear-ching counter 115 reaches a value equal to the sum of half its capacity plus a value B representing the amplitude of the search in the desired distance toward greater distances, the high stop device 117 causes by the corresponding input of the bistable 118 the swinging of said bistable thus inhibiting the counting device 105 and permits the operation of the decounting Nd and simultaneously directs these pulses to the input 114 of the search counter 115 and to the input 106 of the distance memory register 101. The contents of the search counter and of the distance memory register decrease by distance incre-ments during each recurring period. When the contents of the search counter 115 reaches a value equal to the difference between half its capacity and a quantity B' representing the amplitude of the distance search desired toward lower distances, the low stop device 116 causes by the corresponding input of the bistable 118 the swinging of this bistable thereby returning the search device to its counting condition.

The end of the order to search leaves the distance memory register 101 with the contents that it had at the moment the order ends.

If the order to search reappears without an initiating signal being applied to channel 122, the distance search proceeds without changing the central distance of the search.

During the distance search, the distance memory register 101 also receives distance increments generated, from the speed memory function of the speed integrator.

Initially, each time that the telemetering urindows are synchronized with the radar echo, the radar generates a signal which by the input 122 puts the bistable 118 in a known state and positions the search counter 115 so that the contents thereof are equal to one half of its maximum capacity.

In order to avoid disturbances which could arise from the introduction of the generation of distance increments from the device 103 when the apparatus is in its search condition, the pulse synchronized with the "top-emission" which is carried by the conductor 1 4 is applied not only to the gate 125 controlling the shift register 111, but also to The transfer order from the distance memory register into the decounting register 111 is provided by a pulse applied through channel 129. It is thus made certain that at the moment of the transfer from the distance register 101 into the register 111, the distance contained in the register 101 does not vary.

The search order applied by the channel 121 to the sequencer 108 is also applied via lead 93 to a gate 9^ which also receives by channel 95 the switching order causing the apparatus to pass from its condition as homing radar to that assuring the firing order. The switching is effected by the switching device 96.

Figure 7 shows the make-up of the sequencer 108. A first gate 130 is provided along the lead 109 which is controlled by the lead 131 from an inhibiting bistable 132 which assures the closing of the gate 130 upon the arrival of a pulse along the lead 133 which precedes the transfer order pulse applied by the lead 109- The opening of the gate 130 is controlled by the bistable 152 upon the arrival via channel 126 of the pulse synchronized with the "top-emission". The gate 134 provided at the input of the sequencer 108 is opened by the order to search applied to the input 121. The sequencer 108 comprises a first pulse divider 135 for providing a first series of counting pulses by the channel 98 and a second pulse divider 137 for providing a series of decounting pulses via channel 99· According to a modification of the invention, the first integration device comprises an incrementor device followed by a register. The discriminator 150 (Figure 8) is then followed by an incrementor which further comprises an accelerometric input 152. The output 153 of the device 151 applies the speed increments to a speed register 15^ which can be of the memory type and which prepositions a multiplier 155 receiving pulses from a clock 156 accompanying it. The multiplier 155 provides on its output 157 distance increments which are applied to a distance register 158.

The incrementor 151 is provided with a device for reducing the band pass width in order that the servo control be stable and responds to the desired characteristics. 33982/2 4

Claims (1)

1. CLAIMS An airborne homing system for a craft carrying an explosive radar means for determining variations in the distance between the craft and a computer means including a memory initially connected to said radar means for establishing a progressively diminishing distance indication upon the craft approaching said a first comparator in the output of said means for generating a switching signal upon said distance indication assuming a first switchover responsive to said switching signal for disconnecting said means from said radar means while preserving data stored in said memory to provide said distance indication independently of said radar and a second comparator in the output of said means for generating a firing pulse for detonation of said upon said distance indication assuming a second predetermined A system according to Claim 1 wherein said memory comprises a first integrator receiving ration signals from said radar said computer means further comprising a second integrator connected to the output of said first A ag o to a of aaa a r a to output a of far aoaalara a t of d or t aa or o a t o aaia a train of of to o a ay for for ai d a old a a Claim 4 naii fur raid orago of aula a aula a d i to of 4 or a id a of Of b xat to pro roa of to a a r od t o r fa a d au a insufficientOCRQuality