A parameter estimation algorithm for LFM/BPSK hybrid modulated signal intercepted by Nyquist folding receiver.

Zhaoyang Qiu,Jun Zhu,Pei Wang,Bin Tang

doi:10.1186/s13634-016-0387-2

Abstract

Nyquist folding receiver (NYFR) is a novel ultra-wideband receiver architecture which can realize wideband receiving with a small amount of equipment. Linear frequency modulated/binary phase shift keying (LFM/BPSK) hybrid modulated signal is a novel kind of low probability interception signal with wide bandwidth. The NYFR is an effective architecture to intercept the LFM/BPSK signal and the LFM/BPSK signal intercepted by the NYFR will add the local oscillator modulation. A parameter estimation algorithm for the NYFR output signal is proposed. According to the NYFR prior information, the chirp singular value ratio spectrum is proposed to estimate the chirp rate. Then, based on the output self-characteristic, matching component function is designed to estimate Nyquist zone (NZ) index. Finally, matching code and subspace method are employed to estimate the phase change points and code length. Compared with the existing methods, the proposed algorithm has a better performance. It also has no need to construct a multi-channel structure, which means the computational complexity for the NZ index estimation is small. The simulation results demonstrate the efficacy of the proposed algorithm.

Highlights

The electromagnetic environment is becoming increasingly complex and many modern radar signals have very high carrier frequencies or wide operating bandwidths [1, 2]
Because the linear frequency modulation (LFM)/binary phase shift keying (BPSK) signal intercepted by the Nyquist folding receiver (NYFR) contains the local oscillator (LOS) modulation, it may be difficult to find a time-frequency kernel which is optimal for the NYFR output directly
3.2 Nyquist zone (NZ) index estimation based on matching component function Once the chirp rate has been obtained, the NYFR output hybrid modulated signal can be simplified via the de-chirp method

Summary

Introduction

The electromagnetic environment is becoming increasingly complex and many modern radar signals have very high carrier frequencies or wide operating bandwidths [1, 2]. Some conventional radar signals such as linear frequency modulation (LFM) signal and frequency agile (FA) signal intercepted by the NYFR have been investigated, and the parameter estimation methods using multi-channel structure have been proposed [8, 11]. Linear frequency modulated/binary phase shift keying (LFM/BPSK) hybrid modulated signal is a novel kind of LPI radar signal. Considering the increasing complexity of radar waveform and the growing demand of wideband receiving, it is necessary to study the parameter estimation of LFM/BPSK signal intercepted by the NYFR. Because the LFM/BPSK signal intercepted by the NYFR contains the LOS modulation, it may be difficult to find a time-frequency kernel which is optimal for the NYFR output directly.

NYFR architecture and NYFR output signal analysis

Phase change point and code length estimation simulation

Findings

Conclusions