RU2199763C1 - Device for giving protection against chaotic pulsation noise - Google Patents

Abstract

FIELD: radio engineering. SUBSTANCE: device has amplitude-to-digital converter, pulsation detection unit, pulsation distribution unit, decoder having multi-channel structure and unit for estimating pulsation flow connected in series. Pulsation detection unit output is connected to the second inputs of decoder and unit for estimating pulsation flow. EFFECT: enhanced effectiveness of protection. 2 cl, 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 that are resistant to impulse noise.

 A chaotic impulse noise is a stream of pulses with a random interval between them. All pulses have the same duration. Chaotic impulse noise (HIP) is characterized by an average density of N imp / sec. Traditional methods of protection - coarsening of the sensitivity of the receiving channel in proportion to the power (amplitude) of the HIP As a result - loss of range of the equipment.

 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 device for suppressing multicomponent interference [2], having a complex circuit-technical solution aimed at suppressing a three-component passive interference. Known rank adaptive sequential detector of signals [3] (prototype), which, like the proposed device contains an analog-to-digital Converter and a pulse detection device.

 The technical result, which the invention is directed to, is to create a device that allows not to reduce the sensitivity of the receiving device for protection against HIP, but to determine the energy areas with a center corresponding to the power of the acting HIP, and it is for signals belonging to this area to close the receiver.

 The technical result is achieved by the fact that the device for protection against chaotic impulse noise comprises a series-connected amplitude-to-digital converter, a pulse detection unit, a pulse distribution unit, a decoder, an impulse flow estimation unit and an encoder enable / disable unit, while the output of the pulse detection unit is connected to the second input of the impulse flow estimation unit, the second input of the enable / disable start block of the encoder is connected to the output of the decoder. The pulse flow estimator, as an option, can be implemented on a serially connected random access memory (RAM) and an arithmetic device, the control input of which is connected to the decoder, and the output is the output of the device, while the RAM address input is connected to the output of the pulse detection unit.

 In the proposed technical solution, the range of the equipment is maintained. Only those signals whose power falls into the forbidden region are not served. As an example, Fig. 1 shows a set of interrogation signals for the NATO Mk-X identification system. This information is known from the source of information [4].

Зная величину Р_л=0,13, можно определить количество образующихся ложных сигналов в сек
n_л=1/2•N•Р_л=1/2•50•10³•0,13=3250.From the above example, it follows that, due to the simplest structure of interrogation signals consisting of two pulses, as a result of HIP, a false set of interrogation code is generated. At the same time, the probability of a set of false request codes, with HIP density. for example, N = 50 • 10 ³ imp / s is determined by the formula
P _l = 1- [P (O)] ⁴ = 1- (e ^{-Δt · N} ) ⁴ ,
where 4 is the number of vacancies in the set of false codes based on 21 μs, because the decoder expects any code out of 4 possible

Knowing the value of R _l = 0.13, you can determine the number of false signals generated in sec
n _l = 1/2 • N • P _l = 1/2 • 50 • 10 ³ • 0.13 = 3250.

Given that the transmitter protection circuitry provides only 1200 holes. / sec, it’s not difficult to make a second conclusion; the responder will be fully occupied with serving false signals
The invention is illustrated by the structural diagram of the device shown in Fig 2, where 1 is the signal from the receiver of the radar transponder, 2 is an amplitude-digital converter (ADC), 3 is a pulse detection unit, 4 is a pulse distribution unit 5 is a decoder, 6 is an impulse flow estimator; 7 — enable / disable block of the response signal encoder; 8 — decoded request signals.

 The device operates as follows.

The video pulse from the output of the receiver of the radar transponder (not shown) is fed to the input of an analog-to-digital converter. Digital codes with an interval At corresponding to the instantaneous values of the video pulse are input to the pulse detection unit. Detection criteria: exceeding a given digital threshold by a digital code and the number of codes that have exceeded the threshold, depending on the duration of the video pulse. If a pulse is detected and its parameters correspond to the requirements for its duration, then the information about the detected pulse goes to the digital block for evaluating the pulse flow and through the pulse distribution block to the digital decoder. The digital unit for estimating the pulse flow is a multichannel device, the number of channels is determined by the resolution in amplitude and theoretically can be equal to 2 ⁿ (where n is the number of bits of the ADC). The unit for evaluating the pulse flow can be implemented on the basis of RAM (random access memory) or adders, then the number of adders is 2 ⁿ . Such devices are widely covered in the technical literature [4]. Consider the option when the impulse flow estimation unit is made of sequentially connected RAM and AU (arithmetic device), the control input of which is connected to the output of the decoder. The arithmetic device provides reading information from RAM, increasing it by 1, if it is necessary to take into account the detection of the next pulse, subtracting the number 2 from the number stored in RAM, if the signal from the decoder arrives, comparing it with a predetermined threshold, recording information back and allowing decoding output . The RAM address input is connected to the output of the pulse detection unit, and the amplitude of the incoming signal is the address of the recording cell. For example, if an impulse with an amplitude of A ₅ arrives, then the number 1 is written to the 5th RAM cell, a second impulse with an amplitude of A _{5 is} received, another 1 is written in the same cell, etc. If the decoder decoded the request with an amplitude of A ₅ , then through the AU the subtraction of the number 2 from the RAM and the command to check that the threshold is exceeded for a given number passes. If the threshold is not exceeded, the decoding signal passes to the input of the enable / disable block of the encoder. Since the requests consist of two pulses, then in the flow of request signals with an amplitude, for example, A ₅ , in the absence of HIP, the contents of the RAM memory cell with address A ₅ will be zero. When exposed to HIP with an amplitude of A _{5, the} contents of the mentioned memory cell will be non-zero. In the unit for evaluating the pulse flow, a scheme for periodically zeroing all RAM memory cells is provided, the period of this operation depends on the HIP density and is established experimentally.

Thus, if the flow of pulses is the essence of the flow of interrogation signals, then the contents of the memory cells of the pulse flow estimator will be close to zero. If a stream of pulses with amplitude An is a consequence of the influence of HIP, then a number will accumulate in the memory cell with address An, since the collection of a false code from this stream is a random process. Subtraction of the number 2 from the contents of the cell An will occur with a probability P _l . When decoding a request signal with amplitude An, the pulse flux estimator extracts the stored number in the cell with address An. If this number is less than the critical value, the start signal is sent from the output of the device to the response code encoder (not shown). If this number is greater, then the response code encoder does not start, that is, a decision is made that the HIP acts with the amplitude An, and unsolicited signals should not be answered.

 In the proposed technical solution, the sensitivity of the receiving path is not roughened, the range of the equipment is preserved, but one of the channels in power is closed for processing, namely the one that most likely contains a false code (HIP).

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

 2. RF patent 2064190, MKI G 01 S 7/36, published July 20, 1996.

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

 4. Reference radar. Ed. M. Skolnik. M .: Soviet Radio, vol. 3, 1976.

Claims (2)

 1. Device for protection against chaotic impulse noise, comprising a series-connected amplitude-to-digital converter and a pulse detection unit, characterized in that a pulse distribution unit, a decoder, an impulse flow estimation unit and an encoder enable / disable block are introduced in series, the output being the pulse detection unit is connected to the input of the pulse distribution unit and to the input of the address of the pulse flow estimation unit, the second input of the enable / disable block of the encoder connected to the output of the decoder.  2. The device according to claim 1, characterized in that the pulse flow estimation unit comprises a random access memory (RAM) and an arithmetic device whose control input is connected to a decoder and the output is the output of the device, while the RAM address input is connected to the output pulse detection unit.

Images