V.V. Akimtsev

One of promising techniques of increase of radar distance resolution is connected with an application of digital signal processing together with nonparametric tests that can show differences in the structure of the returned signal in the range of its duration under the condition that this signal is a sample of overlapping of returned signals received from several targets. Such technique under the condition of a priori uncertainty, when there is no information about properties of internal receiver noise and external noise, can give acceptable for practice values of resolution. Generally pulse radars are used for an airspace observation and there is a necessity to represent the returned from a target impulse signal in such a way that makes it possible to raise and to decide the problem of how to exceed the distance resolution of pulse radars above the Rayleigh limit and to receive a value that would be sufficient for qualitative resolution of targets. The necessary type of representation of returned from a target signal that fits for using of nonparametric tests is discussed in the article. Also the limit of time delay resolution for this representation is determined. This limit is specified by the sampling interval of receiver-s input process during its digital processing. Nonparametric procedure of distance resolution of unknown number of targets by means of surveillance radars is suggested. Operational reliability of the distance resolution algorithm is confirmed by the method of statistical modeling, quality characteristics of the algorithm for the simplest but widespread case, when signals are observed against the background of receiver noise, are received. Operability analysis of nonparametric algorithm, when retuned signals have frequency shifts and clock oscillator of the ADC receiver has the frequency drift, is carried out. It is shown that for real values of the oscillator instability and Doppler frequency shift of returned signals operability of nonparametric algorithm of distance resolution is maintained.