Fig. 3: Demonstration of highly selective attenuation of nonstationary frequency interferences.
From: Agile manipulation of the time-frequency distribution of high-speed electromagnetic waves
a Measured temporal waveform of the SUT, which is composed of two linear-chirped signals (‘S1’ and ‘S2’) and several interferences (‘\({i}_{1}\)’ – ‘\({i}_{4}\)’) with varying frequency locations and temporal durations. b Intensity of the numerical STFT, or spectrogram, of the SUT. c Measured TM-SP trace at the output of the STFT scheme, with zooms-in around the location of the interferences, each zoomed waveform extending over on analysis period (\({T}_{r} \sim 9\,{{{\rm{ns}}}}\)). The top axis in each zoomed plot corresponds to the equivalent relative frequency axis. d A 2D representation of the measured TM-SP and the close-ups of the interference sections. The different frequency interference components are well discriminated even when extending over a duration as short as the analysis period (9 ns for ‘\({i}_{4}\)’). e The measured output temporal trace (TM-SP) after the temporal filtering, with the same zoom-in regions as in (c), and (f), The corresponding 2D representation of the measured TM-SP of the processed signal, confirming that the unwanted interference components are strongly attenuated. SUT: Signal Under Test, STFT: Short-time Fourier Transform, TM-SP: Time-Mapped Spectrogram, 2D: two-dimensional.
