An Ultra-Wideband Spectrum and Spatial Spectrum Sensing System Based on Improved Nyquist Folding Receiver and Phase Coding

Abstract

In the complex electromagnetic environment, non-cooperative radar signal information extraction and equipment miniaturization in the wide frequency band and wide spatial range are important research topics for radar warning. Some scholars have proposed a high-resolution phase sampling interferometry named Optimum Symmetrical Number System (OSNS). This structure has the characteristics of high resolution, small baseline, a smaller number of phase sampling comparators, and can overcome the Direction of Arrival (DOA) ambiguity caused by the imperfect array spacing, but this algorithm needs to obtain the signal frequency first. To sense the signal frequency in a wide frequency range, a sensor structure, Nyquist folded receiver (NYFR), is proposed, which can receive the signal using a low-speed ADC while retaining the signal information. The architecture introduces a key parameter, the Nyquist zone Index (NZI), which marks the frequency band where the signal originally resides. Direct estimation of NZI requires high signal-to-noise ratio (SNR) conditions and needs to update the algorithm logic according to the signal type. This paper presents an ultra-wideband spectrum and spatial spectrum sensing system based on improved Nyquist folding receiver and phase coding, namely Phase Coding Nyquist Folding Receiver (PC-NYFR). The system combines frequency measurement and direction finding with pre-operation, and NYFR is improved to Dual-antenna Dual-channel NYFR (DDNYFR), which completes effective, high-precision, and anti-noise frequency estimation, compared with the original structure, the performance of SNR requirement is decreased by 3dB; The obtained frequency information is used to encode the phase of DOA like OSNS and complete DOA estimation. PCNYFR is a small baseline array architecture with an ultra-wideband frequency range and wide spatial range, which can obtain all signal information, and uses a small number of antennas, phase comparators, and low-speed ADC. Comparative simulation experiments verify the effectiveness of PC-NYFR and its robustness to noise.