Abstract
In this paper, a new wideband digital receiver based on the modulated wideband converter compressed sampling (CS) system is proposed to replace a conventional wideband digital receiver, solve the cross-channel signal problem, and achieve intra-pulse modulation recognition for the low probability of intercept (LPI) radar signals. The proposed receiver uses cyclic-shifted pseudo-random sequences to mix the received signals to baseband. The mixed signals are low-pass filtered and down-sampled to obtain compressed sampling data containing the full information of the received signals. Since the phases of the multi-branch CS data are designed to change regularly, we propose a phase correction factor to correct the phases of the multi-branch CS data, which can be superposed to increase the output signal-to-noise ratio (SNR). Then, a recognition method based on the short-time Fourier transform (STFT) and spectrum energy focusing rate tests are proposed. First, the spectrum modulation bandwidth based on the STFT spectrum of the superposed CS data is tested to distinguish phase modulation signals and frequency modulation signals approximately. Then, the spectrum energy focusing rate of the superposed CS data is tested to determine the intra-pulse modulation type specifically. Finally, the superiority of the proposed recognition system for LPI radar signals and cross-channel signals is demonstrated by simulations and analysis. Simulation results show that the overall ratio of the successful recognition (RSR) is 100% when the SNR is greater than 0 dB.
Highlights
In recent decades, low probability of intercept (LPI) radar signals that are anti-jamming and high resolution have been widely applied in passive radar systems and electronic reconnaissance equipment [1], [2]
We propose a recognition method based on short-time Fourier transform (STFT) [42], [43] and the spectrum energy focusing rate [30] tests for LPI radar signals including normal signal (NS), binary phase shift keying (BPSK), quadrature phase-shift keying (QPSK), linear frequency modulation (LFM), non-linear frequency modulation (NLFM), and binary frequency shift keying (2FSK) intercepted by the proposed MWC discrete compressed sampling receiver
In this paper, we propose a wideband digital receiver based on the MWC discrete compressed sampling receiver to intercept and recognize LPI radar signals and cross-channel signals in electronic reconnaissance equipment and passive radar systems
Summary
LPI radar signals that are anti-jamming and high resolution have been widely applied in passive radar systems and electronic reconnaissance equipment [1], [2]. In [23], a novel compressed sampling system based on MWC is proposed to acquire the chirp signal, which does not require prior information of the carrier frequency and chirp rate of the received signal. We propose a recognition method based on short-time Fourier transform (STFT) [42], [43] and the spectrum energy focusing rate [30] tests for LPI radar signals including normal signal (NS), BPSK, QPSK, LFM, NLFM, and binary frequency shift keying (2FSK) intercepted by the proposed MWC discrete compressed sampling receiver. Simulation results are presented to demonstrate the validity of the proposed MWC compressed sampling receiver for recognizing LPI radar signals including normal signal (NS), BPSK, QPSK, LFM, NLFM, 2FSK and cross-channel signals.
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