Phase-Code Shift Keyed Probing Signals with Discrete Linear Frequency Shift Keying and Zero Autocorrelation Zone

Abstract

Modern synthesized aperture radars (SAR), e.g. space SARs for remote sensing of the Earth, use signals with linear frequency modulation and signals with phase-code shift keying (PCSK) coded by M-sequence (MS) as probing signals. Utilization of PCSK-signals permits an essential improvement of the radar image quality at the stage of its compression on azimuthal coordinate. In this paper, probing signals with zero autocorrelation zone (ZACZ) are synthesized, which signals represent a sequence of two PCSK-pulses with additional linear frequency shift keying of sub-pulses in the pulses. A comparative analysis of the correlation characteristics of the synthesized signal and the PCSK-signal coded by MS has been performed. It shows that in ZACZ, at a mismatch in the Doppler frequency, the level of all ACF side lobes (SL) of the synthesized signal is less than the ACF SL level of the PCSKsignal coded by MS. The total ACF of the ensemble of 4 signals has zero SL along the whole time axis $\tau$, and at a mismatch in frequency in ZACZ, it has a lower SL level than the total ACF SLs of the ensemble of 4 PCSK-signals coded by MS.