RU2742532C1 - Coherent “ping-pong” interference and backward digital radio frequency memory - Google Patents

Abstract

FIELD: radar and electronic warfare (REW).

SUBSTANCE: invention relates to radar and electronic warfare (REW) and is intended for protecting an object from high-precision weapons by producing angular interference to radar stations (RS). To achieve a technical result proposed is a method for producing a coherent interference which uses two spatially separated receiver-transmitter devices (RTD) with digital radio frequency memory (DRFM). Each device receives and records the received radio signal from the RS into the DRFM. In order to retransmit the signal, each device reproduces the recorded radio signal from the DRFM in a backward (reversible) direction than during recording, wherein the signal phase is changed by 180 degrees in one of the devices. In contrast to the usual organization of the work of signaling memory DRFM on the principle of «first in, first out», the work of signaling memory DRFM in this way organized according to the principle of «last in, first out», with the homing of the interference in the direction and stabilizing the resulting diagram of direction to the source of the signal being performed.

EFFECT: technical result consists in backward reproduction of the recorded radio signal.

10 cl, 7 dwg

Description

The invention relates to the field of electronic warfare (EW) and is intended to protect an object from guided high-precision weapons, by creating angular interference with radar tracking and guidance equipment (radar), including missiles with active radar homing heads (ARGSN) with a monopulse direction finding method.

The actual problem of electronic warfare is the protection of an object from guided high-precision weapons, in particular from missiles with (ARGSN). Modern ARGSN, for guiding the missile to the target, uses a monopulse method of direction finding, which has a high noise immunity from organized interference from the protected object. The essence of the monopulse radar method of direction finding is to measure the normal to the phase front of the wave reflected from the target, the direction of which is identified by the direction finder with the direction to the target. An effective way of self-protection of an object (individual protection) from missiles with a monopulse ARGSN is the creation of coherent interference [Perunov Yu.M., Fomichev LM, Yudin L.M. Electronic suppression of information channels of weapons control systems. M .: Radiotekhnika, 2003].

The coherent interference technique uses a pair of spaced-apart coherent signal emitters to create a multi-lobe radiation pattern. Coherent interference will provide maximum efficiency in the area of space, where conditions close to antiphase and equality of amplitudes of coherent signals are met [Vakin SA, Shustov LN Fundamentals of radio countermeasures and electronic intelligence. M .: Soviet radio, 1968]. A necessary condition for the effectiveness of coherent interference is the excess of the interference power over the reflected signal power at the receiving point. The interference power requirements are reduced when the ARGSN tracking strobe is removed from the protected object.

The effect of coherent interference is the distortion of the wave front in the antenna aperture, which in turn leads to an error in measuring the angular coordinates of the target and, ultimately, to the failure of tracking and missile miss. Due to the distortion of the wavefront, the rocket is aimed at an imaginary target, which is displaced from the true target by an amount depending on the distance between the emitters (base) and the degree of correspondence of coherent signals to antiphase conditions and equal amplitudes. The offset value can reach tens of base lengths, so even with a difference in amplitude of 10% and a phase of 175 degrees, the pointing error will be about 15 base lengths [see, Vakin SA, Shustov L.N. Fundamentals of radio countermeasures and electronic intelligence. M .: Soviet radio, 1968 - p. 200].

The problem of practical use of coherent interference for self-protection of an object (personal protection) is the complexity of the equipment to ensure a stable and optimal amplitude-phase distribution of the resulting interference field at the point of receiving the reflected signal. The complexity of creating equipment is also due to the need to ensure invariance to the signal frequency and direction to the radar.

The known method and device for creating coherent interference, consisting of two transceiver devices with digital radio frequency memory (TsRCHP, English Digital Radio Frequency Memory - DRFM) and cross radio frequency paths with phase shifters [Perunov Yu.M., Fomichev L.M., Yudin L .M. Electronic suppression of information channels of weapons control systems. M .: Radiotekhnika, 2003], [IT RM2009A00330]. The disadvantage of this method and device is the need for cross radio frequency paths.

The invention for creating coherent interference does not require measuring the bearing on the radar, does not require cross radio frequency paths and provides the following technical result:

- simplification of the equipment for creating coherent interference;

- the possibility of using coherent interference for individual-mutual protection;

- expansion of tactical methods of using coherent interference.

The method of creating coherent interference uses two spaced-apart transmitting-transmitting devices (RFM) with digital radio frequency memory (RFMM). Each device receives and records the received radio signal from the radar in the digital frequency readout. To retransmit the radio signal, each device reproduces the recorded radio signal from the digital frequency converter in the opposite direction (reverse) than when recording, while in one of the devices the phase of the signal is changed by 180 degrees (see Fig. 1). PPU can contain amplifiers to increase the gain of the transmit-receive path.

In contrast to the usual organization of the work of the signal memory of the CDRP according to the principle of "first come - first out" (English Fist In - Fist Out, FIFO), the work of the signal memory of the CDRP in this method is organized according to the principle of "last come - first out" (eng. Last In - Fist Out, LIFO) or "last written - first read", i.e. is a stack memory (see Fig. 1). With such an organization of the memory of the digital frequency converter, there is a homing of interference in the direction and stabilization of the resulting radiation pattern to the signal source.

Thus, if the input radio pulse is presented in the form of a ball launched into the protected object, then it, as it were, bounces off it in the opposite direction, without changing its orientation. Therefore, this method of interfering, for the sake of clarity, is proposed to be called "ping-pong".

The principle of creating coherent ping-pong interference is shown in FIG. 2 to FIG. 4. The radar signal, in the form of a pulse, consisting of three periods of the radio signal, is emitted by the radar antenna from point M, received by the antenna of the first PPU at point A and the antenna of the second PPU at point B (see Fig. 2). The memory of the CDRP is conventionally shown by segments, and the direction of recording and playback by arrows. FIG. 2 shows the moment of the start of signal recording; signals are recorded into memory from bottom to top. The radio signal received by the first PPU is recorded in the memory of the DSPC # 1, the radio signal received by the second PPU is recorded in the memory of the DSPC # 2. FIG. 3 shows the moment of the end of recording of radio signals and the start of playback. After recording, the radio signals are reproduced in the reverse order than during recording (from top to bottom) and are emitted by antennas from points A and B, respectively, by the first and second PPU, while the second PPU changes the signal phase by 180 degrees. FIG. 4 shows the moment of the end of playback, it can be seen that the radiated radio signals form a distorted resulting phase front in the direction of point M, where the radar antenna is located.

The method of creating coherent interference "ping-pong" is invariant (not sensitive) to the signal frequency and direction to the radar. The method does not require detection of an input radio signal, therefore, it can be effectively used against radars using signals with a low probability of interception (Low Probability of Intercept, LPI).

To maximize the provision of antiphase conditions and equality of signal amplitudes at the receiving point, the transceiver devices must ensure the maximum identity of the transmit and receive paths in amplitude (gain) and phase. To ensure the identity of the paths, it is possible to use methods of calibration and compensation of distortion in the path.

Coherent interference can be formed in both pulsed and continuous modes. Pulse mode allows to temporarily separate the reception and transmission of signals (temporary isolation), thereby simplifying the transceiver by using a common antenna for reception and transmission. It is preferable to implement the continuous mode of generating interference using separate antennas for reception and transmission, since the use of a common antenna will require the use of devices (circulators) and (or) methods of signal separation (compensation, calibration, etc.). When using separate antennas, it is necessary to maximally ensure the equality of the distances between the phase centers of the receiving and transmitting antennas of the two transmitting and receiving devices and their stability.

In the pulse mode of noise generation, the signal recording in the digital frequency converter periodically alternates with the signal reproduction. The duration of the recording and playback operations can be either the same or different. If the duration of the playback operation is longer, multiple playback of the recorded signal is possible.

For a continuous mode of noise generation, it is necessary to simultaneously record and reproduce a signal in the digital frequency converter, this can be done by applying double buffering, i.e. to organize two buffers (for two frames) in the memory of the digital frequency converter, for performing alternate recording and playback operations in them. Those. when recording a signal into one buffer, at the same time, the previously recorded signal from the second buffer is played back, then operations on the buffers are cyclically changed.

The moments of the beginning of the recording and reproduction of signals in the two DDCs can be either synchronized or not. To synchronize the operation of the two DDS, it is necessary to use a common synchronization signal (see Fig. 5). The synchronization signal can be applied both once at the beginning of the PPU operation, and periodically during operation. The synchronization signal can be formed in one of the PPU, in this case it acts as a master, and the second as a slave (see Fig. 6). The synchronization signal can be transmitted in the form of a radio signal using the transmit-receive paths of the PPU.

Changing the phase of the signal by 180 degrees can be done digitally by inverting the signal (multiplying digital discrete samples of the signal by -1). The change in the phase of the signal can be carried out in the digital frequency converter using a digital phase modulator or manipulator. Changing the phase of the signal, possibly using a separate analog phase shifter or by inverting the signal polarity. The equalization and change of the amplitude (power) of radio signals can also be carried out in digital form in the digital frequency converter or using analog devices (attenuators), controlling that the difference does not exceed 2 dB. Amplitude and phase adjustment can be carried out in one or two PPUs. The control of the operation of the PPU can be carried out from one PPU (master) by transmitting commands to the slave PPU. The control of the PPU operation can also be carried out from an external device.

If the output power is insufficient, to cover the protected object with interference, you can remove the tracking strobe from the protected object (reflected signal), for which, at the first stage of creating interference, the phase difference is set to 0 degrees, in this case, the retransmitted signal received by ARGSN will have a maximum amplitude, over time the tracking strobe is shifted in range and Doppler speed, after which the phase changes smoothly or abruptly up to 180 degrees [Perunov Yu.M., Fomichev LM, Yudin LM. Electronic suppression of information channels of weapons control systems. M .: Radiotekhnika, 2003]. The withdrawal cycles can be periodic or one-shot. In the general case, in order to disrupt tracking and miss a missile, the relayed radio signal can be endowed with modulation in amplitude and / or phase and / or delay. The laws of changing the parameters of radio signals can be different and depend on the tactical situation.

The digital frequency converter requires a reference clock signal, from which it receives the internal clock signals necessary for the operation of the ADC, DAC and FPGA, as a rule, using frequency synthesizers with phase locked frequency control (PLL). Formation of ping-pong interference, possibly with both a common clock signal and independent clock signals. The common clock signal is generated by one generator, the signal from which is fed to both digital frequency converters. The clock signal (CLK) can be generated in one of the PPU, in this case it acts as a master, and the second PPU as a slave (see Fig. 7). The clock synchronization signal can be transmitted in the form of a radio signal (pilot signal) by organizing a separate radio link or using the transmit and receive channels of the PPU for receiving and transmitting. Synchronization of such signals in the DSPC is possible using external radio signals, for example, signals from radio navigation systems (LORAN-C, eLORAN, Chaika, etc.) and satellite navigation systems (GPS, GLONAS, etc.).

With independent clock signals, each DTC device contains an autonomous clock generator. The circuit with independent clock signals provides greater convenience when placed in the protected object, because does not require any connection between two PPUs, which in this case work autonomously. The disadvantage of a circuit with autonomous clock generators is the presence of an additional phase error between the two generated signals due to differences in the frequencies of the generators, which impairs their coherence. Let us estimate the phase error when using temperature-compensated crystal oscillators in the digital frequency converter. Typical value for relative accuracy and frequency stability for this type of oscillator is 10 ^-6 , i.e. at a frequency of one generator of 1 MHz, the relative drift in 1 second of the second generator (frequency 1.000001 MHz) will be one frequency period. Suppose we want to generate interference at 10 GHz, i.e. the signal frequency is 10,000 times greater than the clock signal and, accordingly, at a delay interval of 1 second, the error will be 10,000 signal frequency periods. The high efficiency of coherent interference is maintained with a phase error of no more than 5-10 degrees (i.e., the phase difference was in the range from 170 to 190 degrees). To reduce the phase error, it is necessary to reduce the signal delay in the digital frequency converter, i.e. to reduce the interval between the recording and playback cycles. So, with a decrease in the delay to 1 μs, the phase error will decrease by a factor of 1,000,000 and for our case it will be:

or

Calculations show that by decreasing the delay, it is possible to provide short-term coherence of signals and thereby preserve the effectiveness of the interference. Thus, the main disadvantage of a circuit with autonomous clock generators is the complexity of implementing large signal delays.

A great advantage of the circuit with autonomous clock generators is the independence of the transceiver devices, which allows them to be placed on different objects, including mobile ones, thereby providing effective individual-mutual protection (IVZ) from guided weapons. Comparing the ping-pong interference with the flickering interference, which is also used for IVZ, the ping-pong interference has the advantage that it does not impose such restrictions on the mutual arrangement of objects of protection as flickering interference.

A method of creating multi-point coherent interference "ping-pong" (more than two emitters) is also possible. A necessary condition for the effectiveness of the interference is to ensure a close to zero vector sum of the relayed signals at the receiving point of the goniometric equipment. So, when using three emitters (three-phase system), it is necessary to provide a relative phase shift in three transceivers by 120 degrees, for example, to introduce a phase shift by 0, 120 and 240 degrees, respectively. One PPM can be conventionally taken as a reference and not change the phase of the signal in it. The advantage of multipoint coherent interference is that the wave front can be distorted in two planes and, accordingly, an additional error can be introduced into the goniometric system along the second angular coordinate. Multi-point interference "ping-pong" further destroys the phase front at the point of reception, which makes it impossible to track and guide the missile with ARGSN to the target covered with such interference.

To ensure the excess of the power of coherent interference over the reflected signal, it is possible to use phased antenna arrays (PAR) or active phased antenna arrays (AFAR) in transceivers. The use of coherent interference "ping-pong" is especially effective when organizing individual-mutual protection using on-board radar stations (BRLS) with a suppression mode and equipped with a digital frequency response with reverse signal reproduction.

Coherent interference is also effective against anti-aircraft artillery systems (ZAK) and anti-aircraft missile systems (SAM) with a command method of guiding a missile to a target and using target tracking radars for direction finding.

Coherent interference "ping-pong" can be used to protect objects from targeted weapons using sound (mechanical) waves instead of radio waves.

The creation of coherent ping-pong interference is possible when installing transceiver devices on airplanes, helicopters, ships, stationary objects, towed radar traps (BRL), disposable jamming transmitters (PPOI), unmanned aerial vehicles (UAVs), winged and ballistic missiles, warheads.

Claims (10)

1. A method of interfering with a radar device by receiving a radio signal from a radar device, recording, playing back and transmitting it by two spaced-apart transmitting and receiving devices with digital radio frequency memory and changing the phase of the radio signal by 180 degrees in one of them, characterized in that the playback of the recorded in digital radio frequency memory, the radio signal is produced in the reverse order (direction) than when it was recorded. 2. The method of creating interference according to claim 1, characterized in that the relayed radio signal is endowed with modulation in amplitude and (or) phase and (or) delay. 3. A method for creating interference according to claim 1, characterized in that the transceiver devices operate in a time-decoupled pulse mode. 4. The method of creating interference according to claim 1, characterized in that the transmitting and receiving devices with digital radio frequency memory have a common reference clock generator. 5. The method of interfering with claim 1, characterized in that the start of recording and reproduction in both devices are synchronized. 6. A method for creating interference according to claim 1, characterized in that the phase of the signal varies in the range from 170 degrees to 190 degrees. 7. The method of creating interference according to claim 1, characterized in that the signal phase is changed by 180 degrees by inverting the signal polarity. 8. The method of creating interference according to claim 1, characterized in that the phase of the signal changes with time from 0 degrees to 180 degrees. 9. The method of creating interference according to claim 1, characterized in that the difference in the power of the relayed radio signals does not exceed 2 dB. 10. Digital radio frequency memory for recording and reproducing input radio signals, characterized in that it contains a stack memory for recording and reproducing radio signals, i. E. memory, access to which is organized according to the principle "last written - first read".

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