Compact Photonics-Assisted Short-Time Fourier Transform for Real-Time Spectral Analysis

A compact photonics-assisted scheme for short-time Fourier transform (STFT) is proposed and experimentally demonstrated. In the proposed scheme, a periodic chirp signal and an electrical bandpass filter (BPF) are applied to achieve a sliding window function. At the same time, the BPF is utilized to realize frequency-to-time mapping and obtain the frequency-domain information in each time window. The STFT can be realized by splicing the frequency-domain information corresponding to different time windows into a two-dimensional time-frequency graph. Experimentally, STFTs of various time-varying microwave signals are demonstrated, where a frequency resolution of 100 MHz, a time resolution of 0.1 mu s, and a real-time measurement range from 1 to 9.7 GHz are separately realized. In addition, the measurement range is only limited by the bandwidth of the applied periodic chirp signal and the center frequency of the BPF. Furthermore, the proposed scheme avoids additional processing latency compared to dispersion-based STFT schemes, which ensures great real-time performance.