Improving the Accuracy and Resolution of Filter- and Frequency-to-Time Mapping-Based Time and Frequency Acquisition Methods by Broadening the Filter Bandwidth

In this article, a method for improving the accuracy and resolution of the filter- and frequency-to-time mapping (FTTM)-based time and frequency acquisition system in the fast sweep scenario is proposed by broadening the filter bandwidth. It is found that the width of the generated pulse via FTTM is mainly determined by the impulse response of the filter when the sweep rate is very fast. Therefore, appropriately increasing the filter bandwidth can significantly reduce the pulsewidth, so as to improve the measurement accuracy and resolution. To verify the validity, short-time Fourier transform (STFT) and microwave frequency measurement (MFM) systems employing the stimulated Brillouin scattering (SBS)-based FTTM are further investigated by inserting a frequency-sweep pump wave for SBS gain bandwidth broadening. The improvement of accuracy and frequency resolution is well confirmed by comparing the measurement results with and without SBS gain spectrum broadening. The MFM accuracy is improved by more than ten times compared with other reported works under a similar fast sweep rate, and the frequency resolution of the STFT is also much improved compared with our former results.