Resolution enhancement algorithms as per Doppler frequency when detecting moving objects by system of radio receivers

Abstract

The research refers to multi-position semi-active and active detection systems of moving objects for the purpose of small areas security. The surveillance system comprises two multichannel Doppler receivers with antenna arrays. Signals reflected from objects are processed in several measuring channels in the receivers. Object angular coordinates are defined by phase method in each resolution range element in Doppler spectrum. The paper’s target is to improve operation efficiency of Doppler radio systems for surveillance over low-altitude and small-size moving objects by enhancing resolution as per Doppler frequency. As opposed to many analytical spectral methods of superresolution in operation, resolution enhancement effect is achieved by means of system operation of two relatively oriented receivers, where the first receiver is active (transmits and receives probing signal), and the second one is auxiliary and can function in passive or active modes. The receivers are guided so that their antenna visual lines make an angle close to 900 and analytical justification is given for that. Estimates of one receiver with a great number of narrow spectral components exceeding the threshold of detecting wanted signal are selected through an analysis of Doppler spectrum. Signal processing algorithms for semi-active and active object detection systems are presented. Advantage of two receivers’ operation is testified by computer-based simulation method of semi-active system enabling to increase detection probability of two objects from 0.7 up to 0.9 and by a narrow margin concerning the estimate precision under simulation by comparison with one active receiver. Active mode operation has an advantage as per Doppler resolution of objects compared to semi-active mode but requires higher energy consumption for beaming. Semi-active mode operation has an advantage of stealth and thus higher reliability compared to active mode. Assessment approaches of frequency and phase in frequency and time domains are shown in comparison. Time domain processing enables to reduce twice signal processing time compared to spectral domain processing subsequent to simulation results but it is limited in case of object resolution by range elements. The concept of constructing radio engineering system to protect small areas within specified range boundaries from unauthorized infiltration of airborne low-altitude objects is stated. The obtained results can be applicable in current semi-active and active systems of airborne object detection.