A Segment Match-Filtering Method Based on Microwave Photonic Frequency-Time Mapping

For spectrum management and signal detection, fast electromagnetic spectrum acquisition is essential. It requires a wide bandwidth, high-frequency resolution, and fast multisignal measurement. The spectrum is refined after the match-filtering (MF) process for the microwave photonic frequency-mapping system, with better signal-to-noise ratio (SNR) and frequency resolution. However, the low-frequency range of the spectrum measurement is limited due to the nonlinear frequency-time mapping (FTM) induced by the finite operation bandwidth of the voltage-current conversion circuit. Hence, this article proposes a segment MF method to improve the frequency measurement range. The nonlinear mapping between the frequency and time is measured in the previous calibration and fitted to calculate the signal frequency. Segment MF in accordance with nonlinear mapping is adopted to improve the two sides of the measurable spectrum range. The double-sideband modulation (DSM) at the quadrature operation point of the electrooptic modulator is introduced in the FTM to enhance stability and eliminate the necessity of synchronization. The electromagnetic spectrum monitoring in the proof-of-concept experiment performs with a 0-10 GHz range, 65 MHz accuracy, 75 MHz precision, and 3 MHz frequency resolution at 5 ms.