Channelized Analog Microwave Short-Time Fourier Transform in the Optical Domain

In this article, analog microwave short-time Fourier transform (STFT) with improved measurement performance is implemented in the optical domain by employing stimulated Brillouin scattering (SBS) and channelization. By jointly using three optical frequency combs and filter-and SBS-based frequency-to-time mapping (FTTM), the time-frequency information of the signal under test (SUT) in different frequency intervals is measured in different channels. Then, by using the channel label introduced through subcarriers after photodetection, the obtained low-speed electrical pulses in different channels mixed in the time domain are distinguished and the time-frequency information of the SUT in different channels is, respectively, obtained and spliced to implement the STFT. For the first time, channelized measurement technology is introduced into the STFT system based on frequency sweeping and FTTM, greatly reducing the frequency-sweep range of the required frequency-sweep signal to the analysis bandwidth divided by the number of channels. In addition, channelization can also be used to improve the time and frequency resolution of the STFT system. A proof-of-concept experiment is performed. The 12-and 10-GHz analysis bandwidth is implemented by using a 4-GHz frequency-sweep signal and three channels and a 2-GHz frequency-sweep signal and five channels. Measurement performance improvement is also demonstrated.