RU2206103C2 - Device to decode request signals - Google Patents

Abstract

FIELD: radiolocation, radar systems with active response in which decoders of request signals are used. SUBSTANCE: device to decode request signals includes amplitude-digital converter, pulse detector, multichannel decoder, pulse distributor, unit comparing amplitudes of signals. EFFECT: potential for isolation of signal received from interrogator from aggregate of noises at any time moment with high degree of authenticity. 2 dwg

Description

 The invention relates to radar and can be used for radar systems with an active response, which are used decoders request signals.

 The interrogation signals of the NATO recognition system of the MK-XA type and the international secondary radar system for air traffic control (ATS RBS) is a two-pulse code, which is presented in the drawing of Fig. 1. The request code is determined by the time interval between the leading edges of the pulses P1 and P3. A similar two-pulse structure of request codes has been adopted in the domestic radar system for air traffic control (GOST 21800-89).

In both international and domestic secondary radar systems, decryption of the request is carried out, including under the condition that the amplitude of the RE pulse differs from the pulse amplitude P1 by no more than ± ΔР. Therefore, for reliable detection of the request signal, it is necessary to remember the amplitude of the pulse P1 for subsequent comparison with it the amplitude of the pulse P3. Under the influence of pulse interference, each pulse received at the input of the decoder can be considered as the first pulse (P1) of the request signal. Since the maximum interval between pulses is 21 μs, which corresponds to the request of mode C of the international exchange system RBS, the memory device must store information about the amplitude of the pulse P1 during this time. With a flow of impulse noise with a density of N imp / s, the storage device will be occupied for a time t = N • 21 • 10 ^-6 s, which will cause the loss of a part of the interrogation signals, which will increase with increasing N. If N reaches the value ~ 50 • 10 ³ pulses / s, then the processing of interrogation signals will practically stop.

 A known method of protection against intra-system interference in radar systems with an active response [1], in which to exclude marks of false targets periodically change the interval between the pulses of the response signals. A known method for detecting a pulsed radio signal against a background of an interfering radio pulse and white noise [2], in which an additional detection channel is formed, in which the DC component of the delay time between the information and interfering signals is evaluated. Known rank adaptive sequential detector of signals [3] (prototype), which, like the proposed device, contains an analog-to-digital Converter and a detection device. Each of these devices provides specific tasks, but does not meet the requirements of a radar transponder. All domestic and foreign responders known from published at present [4] (domestic СО-69, СО-72, ОСА-С, СО-94, 680, 620, 420, foreign TRA-67A, AN / APX-103, AN / APX-109 and others) have single-channel decoders of request signals.

 The technical result to which the invention is directed is to ensure that the interrogator signal is received with greater reliability at any time, not to miss the interrogation signal.

The technical result is achieved by the fact that the device for decoding the request signals contains a series-connected amplitude-to-digital converter, a pulse detection unit, a pulse distribution unit, a decoder that has a multi-channel structure with the number of channels calculated by the formula of n channels = 21 • 10 ^-6 • N max + 1, where N is the density of impulse noise at the input of the receiving device, and the signal amplitude comparison unit, the output of the pulse detection unit is connected to the input of the pulse distribution unit and to the input m of amplitude selection of the signal amplitude comparison unit, the output of the pulse distribution unit is connected to the inputs of each decoder channel, the outputs of which are connected to the corresponding inputs of the signal amplitude comparison unit, the output of which is the output of the device.

 In the proposed technical solution, at any moment in time, a channel for decoding will be free for a request signal arriving against the background of impulse noise.

 The drawing of figure 2 shows the functional electrical circuit of the device for recognizing pulses, where 1 is the signal from the receiver of the radar transponder, 2 is an amplitude-to-digital converter (ADC), 3 is a pulse detection unit, 4 is a pulse distribution unit 5 is a decoder , consisting of n channels, 6 - block comparison of amplitudes, 7 - decoded request signals.

 The device operates as follows.

 The signals received by the antenna (not shown in the drawing) from the output of the receiving device 1 are fed to the input of the ADC 2, then to the pulse detection unit 3, which performs the evaluation of the pulse parameters. From the detection unit, the selected pulses are fed to the pulse distribution unit and to the input of the amplitude selection of the signal amplitude comparison unit. The pulse distribution unit is connected to a multi-channel decoder (DS), the task of which is to recognize the request signals. The busy time of each channel is not more than 21 μs from the moment the first pulse arrives at its input. From the outputs of the channels, the decoded signals are sent to a signal amplitude comparison unit for amplitude comparison. Decoding is possible in the presence of coincidence of pulses in time and amplitude. Download channels as follows. The pulse distribution unit, built, for example, on the basis of a ring register with comparison circuits, ensures uninterrupted operation of the decoder channels. The ring register provides sequential inclusion of channels from the 1st to the n-th, after which the first channel is turned on again. All channels of the decoder are identical and can be constructed, for example, according to the standard scheme based on the shift register and the logical circuits of AND and OR.

 The next impulse arrives for record in LH. If there is already a previously recorded pulse in the n-channel, then the time interval between the moment of arrival of the first pulse and the current one received in the LH is evaluated. If the interval corresponds to the request code, then the code combination is sent to the signal amplitude comparison unit, where the amplitudes received from the pulse detection unit are compared with the amplitude of the pulses contained in the code combination. The amplitude of the pulse received from the detection unit is stored and stored in a storage device (RAM) of the signal amplitude comparison unit during the cycle time of the decoder 21 μs. If the amplitude in the code combination received from the DS does not correspond to any of the amplitudes of the previously received pulses, the difference should be no more than ± ΔР, then decoding does not occur. If there is a coincidence in time and amplitude, the decoded request signal from the output of the signal amplitude comparison unit goes for further processing to the analysis schemes of the radar transponder.

References
1. RF patent 1290879 MKI: G 01 S 13/76, published October 20, 1999.

 2. RF patent 2160905 MKI: G 01 S 7/292, published on December 20, 2000.

 3. RF patent 2100822 MKI: G 01 S 7/292, published October 27, 1997.

 4. Aircraft radar systems. Ed. P.S. Davydova M., "Transport", 1988, pp. 252-282.

Claims (1)

A device for decoding request signals, containing a series-connected amplitude-to-digital converter and a pulse detection unit, characterized in that a decoder is introduced, which has a multi-channel structure with the number of channels calculated by the formula n channels = 21 • 10 ^-6 • N max + 1, where N is the density of impulse noise at the input of the receiving device, the pulse distribution unit and the signal amplitude comparison unit, the output of the pulse detection unit is connected to the input of the pulse distribution unit and to the amplitude input of the selection of the signal amplitude comparison unit, the output of the pulse distribution unit is connected to the inputs of each decoder channel, the outputs of which are connected to the corresponding inputs of the signal amplitude comparison unit, the output of which is the output of the device.

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