Development of a direct penetrating signal compensator in a distributed reception channel of a surveillance radar

General structure of a compensator of a direct penetrating signal in the diversed reception channel was developed. It is advisable to use the antenna and the receiver of the auxiliary diverted reception channel as an auxiliary antenna and an auxiliary channel. To be able to suppress the penetrating signal in the band of the receiving device of the surveillance radar, distance between the antennas should be up to 6 m. In general, the compensator of the penetrating signals should contain an adder in which the signals received by the main channel are added with the signals received by the auxiliary channel and sent through the amplifier with a corresponding complex transmission coefficient. The direct penetration signal compensator features the obligatory condition of adjusting the value of the complex transmission coefficient of the auxiliary channel signal amplifier. The direct penetration signal compensator is digital and uses the direct method of forming weighting coefficients without the use of feedback. To reduce the time of formation of weighting coefficients when using direct methods of calculation of the correlation matrix, the technology of parallel computational processes was used. The quality of operation of the direct penetrating signal suppression system in the diverted reception channel was evaluated. It was established that without the use of suppression of direct penetrating signals, their powerful response at the output of the matched filter mask weak echo signals. When using a direct penetrating signal in the main channel of the compensator, its response at the output of the matched filter is significantly reduced. This makes it possible to observe weak echoes against the background of a strong penetrating signal. The use of the developed direct penetrating signal compensator provides suppression of the direct penetrating signal from 57 dB to 70 dB

ON SOFTWARE IMPROVEMENT OF IMAGE CHANNEL SUPPRESSION IN SDR RECEIVERS WITH ANALOG CONVERSION TO A LOW INTERMEDIATE FREQUENCY

A method for digital signal processing in SDR receivers with analog conversion to a low intermediate frequency is proposed. In contrast to known systems, the proposed approach does not consider parasitic phase and amplitude distortions, but uses the direct method minimizing of the signal of the mirror reception channel. Generally speaking, this can be done simultaneously at several frequencies. It is shown that in computational terms, this is reduced to signal processing by an algorithm similar to a digital non-recursive filter, and to determine its coefficients, it is sufficient to solve a system of linear algebraic equations.

SYNTHESIS OF A SIGNAL-INVARIANT ALGORITHM FOR ESTIMATING THE AVERAGE POWER OF A GAUSSIAN NOISE OF UNKNOWN INTENSITY

Решается актуальная задача тестирования канала приема радиосигнала с точки зрения помеховой обстановки. Приводятся результаты синтеза алгоритма оценивания средней мощности совокупной гауссовой помехи в канале приема с неизвестной интенсивностью, инвариантного к наличию сигнала в нем, и варианта технического решения, реализованного на его основе. Новизна предлагаемого подхода заключается в применении автокорреляционной и корреляционной обработки входного процесса в виде аддитивной смеси сигнала неизвестной формы и гауссовой помехи для измерения априори неизвестной средней мощности помехи. Измерение основано на различии в дисперсиях помеховой (шумовой) составляющей на выходах автокорреляционного и корреляционного каналов обработки. Это различие позволяет алгоритмически путем вычитания определить неизвестную среднюю мощность помехи. The actual problem of testing the radio signal reception channel from the point of view of the interference environment is solved. The results of the synthesis of an algorithm for estimating the average power of the aggregate Gaussian interference in a receiving channel with an unknown intensity, invariant to the presence of a signal in it, and a variant of a technical solution implemented on its basis are presented. The novelty of the proposed approach consists in the application of autocorrelation and correlation processing of the input process in the form of an additive mixture of a signal with unknown shape and a Gaussian noise for measurement an a priori unknown average noise power. The measurement is based on distinction in dispersions of an interfering (noise) component on outputs of autocorrelated and correlative processing channels. This distinction allows us to determine the unknown average interference power.

INFLUENCE OF INTERACTION BETWEEN ELEMENTS OF THE RADAR ANTENNA–FEEDER NETWORK ON THE NOISE CHARACTERISTICS OF THE RECEPTION CHANNEL

The influence of the interaction effects of the transmitting and receiving antennas of a mil-limeter-range radar, as well as the direct transmission of the transmitter signal to the receiver input via the internal circuits of the microwave chip on the level of the decorrelated phase noise is under consideration. It is shown that for a certain amount of interaction between the anten-nas, the delay time of signal propagation along the paths of additional reception, the receiver noise factor and the level of phase noise of the carrier frequency of the transmitter at the detun-ing frequency equal to the frequency of the useful signal, the output noise power of the receiver converter by the additional receiving channel and the receiver’s own noise become comparable. Due to the additional noise reception channel, the signal-to-noise ratio decreases and the range of the radar action decreases as well. The calculation uses data for the noise factor of the re-ceiver and the spectral density of the phase noise of the synthesizer of the AWR1243 millimeter–wave transceiver chip from Texas Instruments in the frequency range from 77 till 81 GHz. The effect of a dielectric antenna shelter on the coupling between the transmitting and receiving antennas, and on the spectral noise power density at the receiver input, is considered. The de-pendences of the spectral density of the decorrelated phase noise due to additional communi-cation channels in comparison with the receiver’s own noise are show