Generating Digital Radar Images Using Nonlinear Filtering Methods for Discrete and Continuous Parameters of Return PM Signals

Abstract

This work considers the method for generating high-resolution radar images (RI) based on the multipath side looking (SL) radar (MPSL), consisting of a set of independent single-beam small-sized radar stations (SRS) with synthetic aperture of the antenna (SAR), working on transmission and reception in any given polarization on board the aircraft (AC). As probing signals, binary PM signals, which belong to one cluster L formed on binary sequences of the maximum linear recurrent period (MLRP) equal to L = 2m −1, m ≥ 2 are used. Emission of probing and reception of return PM signals are carried out simultaneously in all cases. Each SRS is assigned its own PM signal from the cluster L. Based on the representation of binary MLRP by the complex Markov chain with two states for one homogeneous single-beam RLS, the receiver is synthesized with the L-channel recurrent matched filter (RMF), own or common for all RLS with SAR included in MRLS, for the simultaneous reception of several or all of the cluster L return PM signals of one and the same azimuth in all SAR beams in range. The characteristic feature of the RMF is the absence in outputs of the RMF side lobes of two-dimensional ACF received PM signals, which allows for simultaneous nonlinear filtering of the discrete and continuous parameters of return PM signals: energy - amplitude fluctuating according to Gaussian or Rayleigh laws, and non-energy - frequency, delay and etc., which, due to cross-links, provide a high estimate of the discrete parameter of the return PM signals, and, accordingly, high resolution RI. To assess the effectiveness of the proposed method, computer simulation of the formation of the RI of the artificial relief with various objects was performed under the influence of Gaussian amplitude fluctuations in return PM signals with Gaussian Doppler random frequencies and their delays relative to the emission time. The simulation results demonstrate the reception of high-resolution real-time RI data in range and azimuth in case of collaborative nonlinear filtering of the discrete (phase) and continuous parameters (amplitude, delay and Doppler frequency) of the return PM signals with minimal computational resources on board the ACt in real time.