Digital Radar Imaging by Nonlinear Filtering Methods of Discrete and Continuous Parameters (Amplitude and Delay) of Reflected PM Signals

Abstract

The article discusses a method for getting high-resolution radar images (RI) based on a side looking airborn radar (SLAR), which consists of a set of single independent single-beam small-sized radar stations (SRS) and a synthetic-aperture radar (SAR) used for transmission and reception in any given polarization on board of the aircraft (AP). Probing signals are binary PM signals of one cluster L formed on binary sequences of the maximum linear recurrent period (MLRP) equal to L = 2m − 1 (m ≥ 2). The emission of probing PM signals and the coordinated reception of the reflected PM signals can be carried out simultaneously by all SRS. Each SRS has its own PM signal from the L cluster. Based on the representation of binary MLRP by a complex Markov circuit with two states and taking into account the same type of SRS, it is possible to synthesize a receiving device with an L-channel recurrence matched filter (RMF) common to all SRSwith the radar included in the MRLP for simultaneous reception of several or the entire cluster L reflected PM signals of the same azimuth in all beams of SAR by range.A characteristic feature of the RMF is the absence of side lobes at the RMF outputs of the autocorrelation functions of the received reflected PM signals of each beam. It allows to get simultaneous joint nonlinear filtering of the discrete parameter (phase) and continuous parameters (amplitude and delay) of the reflected PM signals that provide to obtain a higher evaluation of a discrete parameter and, accordingly, high-resolution radar images. The result of the reflected PM signals of each beam is recorded in the memory unit, where SLAR is formed. To assess the effectiveness of the proposed method, the authors carried out computer modeling of the formation of the radar image of an artificial pattern with various objects under the influence of Gaussian fluctuations in the amplitude and delay of the reflected PM signals relative to the time of their radiation. The simulation results demonstrate getting high-resolution radar images in resolution range and azimuth in real time.