  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, channelization measurement technology is introduced in 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. 12-GHz and 10-GHz analysis bandwidth
is implemented by using a 4-GHz frequency-sweep signal and 3 channels and a
2-GHz frequency-sweep signal and 5 channels. Measurement performance
improvement is also demonstrated.
