Broadband linear frequency modulation signal compression based on a spectral Talbot effect

Abstract

Broadband linear frequency modulation (LFM) signals with a long duration are widely used in radar and broadband communication systems. The LFM signals are compressed to a Fourier-transform-limited pulse train after matched filtering, which effectively improves the signal-to-noise ratio (SNR) of detection. Quadratic phase response is the key component of matched filtering, which can be achieved by phase filters or dispersion elements. Suffering from the limited resolution of phase filters and complex equivalent large dispersion structures, pulse compression of broadband LFM signals with a long duration remains an open challenge. In this paper, LFM signal compression based on the spectral Talbot effect is proposed and experimentally demonstrated, where ultra-large equivalent dispersion (around 1.7  ×  109 ps/nm) is realized by a simple optical filter ring. Experimentally, the LFM signal with a bandwidth of 12 GHz and a duration of 163 µs is compressed into a Fourier-transform-limited pulse train, which improves the SNR by 24 dB. Moreover, the proposed method also measures the delay difference between two LFM signals, ranging from 0 to 110 ns.