EP0738870A1 - Communication method for mines of a land minefield and mines for working out thereof - Google Patents

Abstract

The system consist of mines (2) with active induction sensors, generators and signal processors, controlled by fixed or mobile transmitters (3,4). A signal fed to the mines by one of the transmitters is picked up by at least one mine and relayed by it at least once to its neighbouring mines, and so on. The frequency for communicating signals between mines is different from the frequency they use for target detection and is selected at random from the frequencies available, and the signals between the transmitter and the mines and/or between mines are encrypted.

Description

The present invention relates to a communication method for mines in a minefield, and to mines implementing it.

The new generation mines will probably all be remotely controllable so as to fully play their role of counter-mobility vis-à-vis the enemy without hampering friendly maneuvers.

In the case of buried or dispersible mines, many factors of choice require the use of a simple unidirectional radio remote control.

The cost criterion is of course important, since the remote control receiver cannot represent a too significant part of the final price of the mine. Indeed, the latter being supposed to be used statistically, a large quantity of mines must be deployed to be effective, which imposes a low unit price to make this means of action competitive.

The large number of mines to be deployed would make it very complex, if not impossible, to manage acknowledgments of receipt of a two-way remote control.

The energy source on board a mine is always limited and unsuitable for transmitting data over a long distance.

Such a remote control concept has two drawbacks:

The first is psychological: a direct response from the mine would secure the occupants of the friendly tank which must cross the remote-controlled minefield. On the other hand, the reception of an acknowledgment of receipt does not prove with certainty that the mine is in a non-dangerous state, the gain of such a response in terms of dependability remains linked to the design of the igniter. mine.

The second concerns the efficiency of the commissioning of the minefield. Indeed, the radio link, whatever the frequency band chosen, is subject to propagation hazards which can prevent the commissioning of certain mines (fading problems, etc.). Furthermore, the possible drift of certain time pilots can lead to isolating certain mines from the transmitter. This problem, even if it is not disastrous from an operational point of view (we count on the statistical effect of this type of mine), affects the effectiveness of the minefield.

The subject of the present invention is a communication method for mines in a minefield which allows, in a simple and rapid manner, to improve the reliability of communications between a command transmitter station and the mines, as well as between mines, whatever the conditions of propagation of these orders, as well as to make emit by these mines a short range acknowledgment of receipt, and allow to optimally coordinate the triggering of these mines.

The present invention also relates to mines capable of implementing such a communication method, without requiring significant modifications to these mines, or significantly increasing the cost price.

The method of the invention applies to a communication system between a fixed or mobile transmitting station and mines dispersed in a limited geographical area and constituting a minefield, and this method consists, after having sent a message by the transmitting station, to have it broadcast at least once by at least one of the mines to the neighboring mines, the mines which receive the message broadcast by at least one of their neighbors in turn retransmitting it at least once, and so on until '' that each mine that received the message sent it at least once.

A mine implementing the method of the invention comprises a sensor circuit with mutual induction coils, a generator producing at least two different frequencies, a demodulator, a signal processing circuit for detecting targets and a signal reception circuit. communications.

• la figure 1 est un schéma simplifié d'un champ de mines, d'un poste émetteur fixe et d'un poste émetteur mobile, fonctionnant selon le procédé de l'invention,
• la figure 2 est un bloc-diagramme d'un émetteur-récepteur de mine conforme à l'invention.

The present invention will be better understood on reading the detailed description of an embodiment, taken by way of nonlimiting example and illustrated by the appended drawing, in which:

• FIG. 1 is a simplified diagram of a minefield, of a fixed transmitting station and of a mobile transmitting station, operating according to the method of the invention,
• Figure 2 is a block diagram of a mine transceiver according to the invention.

There is shown in Figure 1 a minefield 1 arranged in a forced passage of vehicles such as tanks. This field includes a large number of buried mines 2, only a few of which have been represented. These mines are of the igniter activation and deactivation type, in particular by remote control. This remote control is implemented by a fixed transmitting station 3, which can be distant from the field 1 and / or by a mobile transmitting station 4, which is for example, placed on board a vehicle 5. This vehicle 5 makes, by example part of a friendly convoy which must cross field 1 without hindrance. This convoy may include several mobile stations such as station 4. Station 4 deactivates, if necessary, the igniters of the mines in field 1 just before the passage of vehicle 5 and the convoy, and reactivates them after this passage. In the case of the passage of a convoy, the last vehicle may also include a station 4.

So that the communication system is the cheapest possible and the least bulky possible, the invention provides for using means already present in the mine igniter to implement the communication method. Indeed, to achieve a long-range remote control system, it would seem necessary to associate with the igniter a conventional radio transceiver, by reusing the antenna already present in the mine. The increase in price and the increase in electrical consumption of such equipment are prohibitive.

On the contrary, the invention provides for using active sensors with mutual induction of mines when they exist and at least a part of their electronic circuits, or if not, to add to them such sensors with their electronic circuits. The term active sensor is understood here to mean a sensor comprising at least one "transmitting" coil coupled to a "receiving" coil, the transmitting coil being supplied with energy, and the passage of a metal part or mass near this sensor modifying the mutual induction between the two coils, so the signal collected by the receiving coil. Conventional sensors with mines are used to detect vehicles passing over the mine, taking into account its depth of burial and the ground clearance of the vehicles. The range of these sensors is relatively small. According to the invention, this radius of action is increased by increasing the current passing through the sensors, so as to allow communication between each mine and at least one neighboring mine.

As shown in FIG. 2, the mine communication device 6 comprises a mutual induction sensor 7 with two flat coils 8, 9 placed horizontally. The emitting coil 8 emits within a radius of action whose value essentially depends on the current flowing through it. The device 6 includes a generator 10 with frequency synthesis, generally controlled by software. The generator 10 is, on the one hand, connected by a digital-analog converter 11 to the coil 8, and on the other hand to a circuit 12 for simulating the transfer function equivalent to that of the device 6 (in transmission and in reception). The circuit 12 is connected by a digital-analog converter 13 to an input of a mixer 14, the other input of which is connected to the output of an amplifier 15, itself connected to the coil 9. The output of the mixer 14 is connected by an analog-digital converter 15 to an input of a mixer 16, the other input of which is connected to a generator 17 of sinusoidal signals. The output of the mixer 16 is connected to a device 18 for synchronous demodulation, for example by FFT. An output (measurement channels) of the device 18 is connected to a signal analysis device 19, and another output (communication channels) of the device 18 is connected to a decoding device 20, itself connected to a device 21 decryption.

In the device 6, the generator 10 synthesizes the measurement frequencies (F1) and those of communication (F2). The generator 10 can be controlled, for example, by a program taking place in the microcomputer (not shown) present in the mine. A microcomputer generally equips current mines and controls various functions such as their standby state and the processing of the signal from the sensor (in order to reduce the rate of false alarms and sensitivity to interference). It therefore suffices to modify, in a manner obvious to a person skilled in the art on reading this description, the existing program to adapt it to the communication system of the invention. Of course, in a simplified variant of the device 6, the generator 10 can produce only two frequencies or a small number of frequencies.

The carriers F1 and F2 produced by the generator 10 are amplitude and phase modulated by the device 12 to serve for neutralization of the receiver, by being mixed in 14 with the signals received by the coil 9 and amplified in 15. The mixer 16, receiving the carrier of the generator 17, performs the frequency shift of the received signals to bring them back to baseband. The circuit 18 performs, in baseband, the demodulation by FFT of the signals received. The demodulation results have non-zero values for the frequencies F1 and F2 in the presence of a vehicle and in the case of reception of remote control signals, respectively. One can also measure in these cases non-zero values on frequencies close to F1 and F2, but practically nothing on other frequencies.

Thanks to such an FFT demodulation device, it is possible to discriminate between communications (remote control in particular), target signals and the various possible jammers. Communications are made on the frequency F2, both in reception and in transmission, and are preferably encrypted (and are decrypted at 21). The targets behave like simple transponders: they only modulate in amplitude and phase the signals transmitted and received at the frequency F1. However, the jammers behave differently. "FM" type jammers transmit on one frequency at a time, but scan a whole range of frequencies. “CW” type jammers transmit on several frequencies simultaneously, and with less power, on a given frequency, than FM jammers. The following jammers listen to the transmitted signals and retransmit them by introducing information characteristic of the presence or absence of a target.

To discriminate between these different signals, the invention provides, on the one hand, for demodulation by FFT, and on the other hand, for broadening the bandwidth of mine transmitters and receivers.

Indeed, demodulation by FFT makes it possible to examine the spectra received on a large number of different frequencies, therefore to discriminate the FM and CW jammers which produce signals on several frequencies at the same time.

In order to eliminate the following jammers, several communication frequencies and several measurement frequencies can be transmitted by the mines simultaneously (without however using all the frequencies available). These frequencies transmitted simultaneously are advantageously determined randomly among all the frequencies available, and, on reception, we must find only these frequencies, neither more nor less (it being understood that the frequencies close to the frequencies emitted and possibly analyzed by FFT are not taken into account). Advantageously, the microcomputer can eliminate the constantly scrambled frequencies or immediately choose other frequencies when some are scrambled.

When a fixed or mobile station issues a remote control command (activation or deactivation of mine igniters, or service interrogation), it is possible that certain mines in a minefield do not receive it or receive it badly. According to the invention, each mine having correctly received this order retransmits it to its neighbors on one or more frequencies different from the frequency on which it received it. It can repeat this order on the same frequencies or on different frequencies. Thus, each mine in the minefield can receive the order directly from the transmitting station, and / or indirectly from its neighbor. This is possible thanks to the fact that the range of the emitting coil of each mine has been increased so as to allow it to communicate with all its neighbors, it being understood that the respective distances between mines do not exceed a determined value which is a function of the maximum range of their induction coils. Increasing the current passing through these coils has very little effect on the autonomy of the mine's electrical power source, since the amount of communications is generally very low, and their duration can be very short.

Thanks to the fact that the mines can communicate with each other, the invention also provides for optimizing the firing of mines and the overall action of the minefield. Thus, for example, when a convoy of enemy tanks enters the minefield, the first mines encountered signal the detection of these tanks to their neighbors, and the triggering of all mines in the field can be ordered when the lead tank reaches the opposite end of the field. These operations are controlled, in a manner known per se, by the microcomputers of the mines.

This command can be coordinated by one of the mines (for example one mine per row) in order to simplify the procedure for trigger, or be relocated: each mine is triggered when it receives, always by close to close communication, a confirmation of tank detection from one of the mines at said opposite end of the field.

Increasing the range of the mine induction coils, without however going significantly beyond the maximum foreseeable distance between neighboring mines, ensures good discretion in communications between mines.

Claims (8)

1. Communication method for mines in a minefield, between an emitting station and these mines, these mines being provided with active induction sensors, generator means and signal processing means, characterized in that after having send a message by the transmitting station, it is broadcast at least once by at least one of the mines to the neighboring mines, the mines which receive the message broadcast by at least one of their neighbors retransmitting it in turn at least once . 2. Method according to claim 1, characterized in that the frequency of communication between a mine and its neighbors is different from the frequency used for the detection of targets. 3. Method according to claim 1 or 2, characterized in that the frequency of communication between a mine and its neighbors is chosen randomly from several available frequencies. 4. Method according to one of the preceding claims, characterized in that the frequency used for mine detection is chosen randomly from several available frequencies. 5. Method according to one of the preceding claims, characterized in that the communications between transmitter station and mines and / or between mines are encrypted. 7. Mine comprising an active sensor with mutual induction coils, a carrier wave generator and a microcomputer, characterized in that the generator (10) produces at least two different frequencies (F1, F2), and that the mine comprises a demodulator (18) demodulating the signals received on the two different frequencies, the output of this demodulator being connected to a measurement and analysis channel (19) of target signals and to a communication reception channel (20, 21) . 8. Mine according to claim 7, characterized in that the demodulator is a synchronous demodulator by FFT. 9. Mine according to claim 7 or 8, characterized in that the reception channel comprises a decryption circuit (21).

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