RADIO PHYSICS AND RADIO ASTRONOMY

Subject and Purpose. One of the main challenges in achieving high-accuracy radar target parameter determination and improving radar system noise immunity is the presence of sidelobes in the ambiguity function of the used signals, especially when these signals are periodic Pseudo-Random m-Sequences (PRS) of maximum length. In this work, a new method for completely suppressing ambiguity function sidelobes is developed through theoretical analysis with cross-correlation processing of PRS-modulated signals and a specially tailored reference signal.

Methods and Methodology. The new approach to suppressing sidelobes of the PRS ambiguity function addresses cross-correlation processing of the received signals. These are PRS modulated using a reference signal tailored so that zero values of the
sidelobes of the correlation function fall beyond the zone of high correlation in the signals.

Results. The proposed method can completely suppress all ambiguity function sidelobes along the time delay axis for the PRS of maximum length. Compared to traditional processing, the sidelobe level along the Doppler shift axis of the carrier is slightly higher. However, this is so when the number of PRS elementary pulses is too small. As their quantity increases, the difference tends to be negligible. The signal-to-noise ratio at the correlator output and the range resolution performance have been estimated for both the proposed and traditional processing methods.

Conclusions. A new algorithm for PRS cross-correlation processing has been developed, accompanied by a straightforward method for tailoring a reference signal. The innovation enables sidelobe elimination regardless of the PRS length, while maintaining both range resolution and signal energy efficiency. It has been demonstrated that the signal-to-noise ratio at the correlator output remains unchanged compared to traditional processing. These points highlight a significant advantage over conventional approaches. Those often call for lengthening the sequence or applying weight processing, which leads to a loss of radar energy efficiency.

Keywords: pseudo-random sequences, sidelobes, radar ambiguity function, autocorrelation function, cross-correlation function

Manuscript submitted  12.01.2025

Radio phys. radio astron. 2025, 30(4): 258-267

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