Application of phase-code shift keyed probing signals with zero autocorrelation zone to improve the quality of measurements in SAR

Abstract

For SARs, a polyphase (p-phase, where p is a prime number) probing signal with a zero autocorrelation zone has been synthesized, which is a train of p phase-code shift keyed (PCSK) pulses coded by complementary sequences of a p-ary D-code with additional phase-code shift-keying of the sub-pulses (discretes) of pulses by an M-sequences. To assess the quality of radar images of point targets and extended surfaces, the levels of the maximum side lobe and one-way integrated correlation noise of the autocorrelation function (ACF) are used, respectively. For this purpose, the work carried out a comparative analysis of the total ACFs of the synthesized ensemble of signals with ensembles of orthogonal chirp and PCSK-signals used in adjacent SAR sounding cycles. The work also considers the problem of superimposition of SAR echo signals from different ranges at a relatively high repetition rate of probing pulses. To assess the level of suppression of recurrent interference from point targets and from extended surfaces, the levels of the maximum side lobe and one-sided integral correlation noise of the cross-correlation function (CCF) are used, respectively. For this purpose, the work carried out a comparative analysis of the total CCFs of the synthesized ensemble of signals with ensembles of orthogonal chirp and PCSK- signals used in the SAR aperture synthesis modes. The use of orthogonal chirp and PCSK-signals makes it possible to successfully suppress false signals from bright point targets from adjacent repetition periods. However, the high level of integral correlation noise of the CCF of orthogonal signals distorts radar images of weakly reflecting surfaces located next to bright extended objects. The indicators of the total correlation characteristics of the synthesized ensemble of signals exceed the corresponding indicators of the total correlation characteristics of the ensemble of orthogonal PCSK-and chirp signals, both without mismatch and with Doppler frequency mismatch. This makes it possible to successfully use an PCSK-signal with a zero autocorrelation zone to improve the quality of radar images and suppress recurrent range interference in SAR.