Patent RU-2708372-C1 (RU)
Title: Method for detecting a pack of radio pulses with an arbitrary degree of coherence and a device for realizing said method
Inventor: Krasnyj Vladimir Petrovich
IPC: G01S13/524
Filed: 2018-06-18
Granted: 2019-12-09
Abstract: FIELD: radio engineering and communications. 
     SUBSTANCE: invention relates to radio engineering and can be used to detect radio signals in the form of a pack of radio pulses on propagation paths thereof, when parameters of medium can be considered to be invariable ("frozen") at intervals shorter duration of pack, and at longer intervals of stationarity without additional analysis of propagation conditions of radio waves. Method and device which realizes it enables to detect radio pulses at their arbitrary degree of coherence, which is caused by changes in signal propagation conditions. Device detection characteristics correspond to coherent detection at a coherent signal and incoherent at fully incoherent pulses in the packet, and under certain conditions, the device characteristics are better than both detectors. Technical novelty of the proposed radio pulses burst detector with an arbitrary degree of coherence lies in the fact that instead of using a coherent detector, an incoherent detector or known quasi-coherent receivers, the disclosed device includes two channels, in one of them there is incoherent detector, and in the second channel – receiver of multiplications, outputs of these channels are combined according to scheme OR. Incoherent detector includes a matched filter for a single signal, a shift register (analogue of a multi-lead delay line), units for generating signals from squared shift register outputs (quadratic detectors), an adder, a threshold device, the output of which is supplied to an OR circuit. Multiplication detector includes the same matched filter and a shift register, the output signals of which are summed in (N-2) adder to form sums of the form Σ j=N   j=i+1 bj, are multiplied in (N-1) multipliers (N-number of pulses in the packet), forming products a i Σ j=N   j=i+1 bj, and then go to adder, then to unit for taking real part of complex signal, multiplied by 2 in the next block, are compared with a threshold in a threshold device and come on a common OR circuit with an incoherent detection channel. This allows radars and communication devices to best receive signals passed through the propagation medium with randomly varying parameters. Proposed device operates as follows. Digitized signal is transmitted to matched filter, and its output signal is transmitted to shift register, each of N outputs of which delays signal for pulse repetition period in pack T relative to previous output. From outputs of shift register signals are squared and then added in adder, summation result is compared with threshold. All together forms an incoherent detection channel. From the output of the same shift register, signals other than those corresponding to squares are summed with (i+1) output by (N-1). Output signal of the adder is multiplied with the i-th output of the shift register. Multiplication results are summed up and subjected to taking the real part with multiplying by 2. Multiplication by 2 is determined by the following. In the detector with quadratic detection, N(N-1) products are obtained pairwise complex conjugates, during summation the imaginary parts of the products are compensated, and the real parts are summed up. Therefore, it is possible to carry out twice less multiplications, taking real part from result of multiplications and multiplying it by 2, then comparing with threshold. By combining the channel outputs in the form of solutions of threshold devices according to the OR circuit, at the output of which there will be a result corresponding to the best detector under given conditions. 
     EFFECT: disclosed is a method of detecting a packet of radio pulses with an arbitrary degree of coherence and a device for realizing said signal. 
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