Time-stretched short-time Fourier transform
ABSTRACT The authors propose and demonstrate the time-stretched short-time Fourier transform (TS-STFT) technique to overcome the limitation of an analog-digital converter (ADC) in the time-frequency analysis of ultrafast signals. Experimentally, the time-frequency analysis of highly chirped RF signals, with a chirp rate as high as 350 GHz/ns, is demonstrated. An effective real-time sampling rate of 320 GSa/s is achieved. Time stretching enhances the analog bandwidth and the effective sampling rate of the ADC and enables measurement of the instantaneous behavior of highly nonstationary ultrawideband signals.
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ABSTRACT: Moving load could enhance damage structural nonlinear character. And time-frequency analysis described character of non-stationary signal more exactly than traditional fourier spectrum. Affine class time-frequency analysis was good at wide-band signal analysis and cross terms suppression. The result of time-frequency analysis was two dimensional�» and time-domain entropy or frequency-domain entropy can extract information and characters from it. Using these characters the structural damage pattern could be recognized by neural network. The validity of this method was reviewed by a beam under moving load. When structure has damage, time-frequency entropy of structural vibration can figure the nonlinear grade of signal availably, and it is not sensitive to noise. It can be used as eigenvectors of pattern identification based on neural network. Keywords-damage identification�◊ time- frequency entropy�◊ moving load�◊ structure�◊ time-frequency analysis�◊ affine class�◊ neural network I� �È?'01/2011;
Conference Proceeding: A cascadable ASIC prototype for real time time-frequency analysis[show abstract] [hide abstract]
ABSTRACT: Wide-band non stationary digital signals are extensively used by modern telecomunications applications. Analyzing those signals in real time is a complex task as we need a joint analysis in time and frequency which is called a time-frequency representation (TFR). As far as we know, there is currently no dedicated ASIC solution for TFR, as the usual approaches are computationally too intensive or do not meet resolution requirements both in time and frequency. In a previous paper we proposed an alternative architecture using a modulation/filtering/decimation/interleaving approach called F-TFR. In this paper, we present a cascadable prototype used to validate this architecture.Circuits and Systems, 2007. MWSCAS 2007. 50th Midwest Symposium on; 09/2007
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ABSTRACT: An all-optical approach to implementing short-time Fourier transform (STFT) of a high-speed and broadband elec- trical signal is proposed and demonstrated for the first time to our knowledge. The STFT is implemented based on a temporal pulse shaping system incorporating an array of cascaded linearly chirped fiber Bragg gratings (LCFBGs). An electrical signal to be analyzed isappliedtoaMach-Zehndermodulator(MZM)tomod- ulate the optical spectrum of a time-stretched optical pulse from a mode-locked laser (MLL). Each individual LCFBG in the LCFBG array functions as a bandpass filter to filter a specific range of the spectrum, which is equivalent to applying a window function to the corresponding section of the temporal signal, and at the same time, as a dispersive element to implement real-time Fourier transform. Atheoreticalanalysisisperformedwhichisverifiedbyanumerical simulation and a proof-of-concept experiment. The key feature of this technique is that STFT can be implemented in real time which can find applications in analyzing an electrical signal with a band- width up to several hundreds of gigahertz.IEEE Photonics Technology Letters 01/2011; 23(20):1439-1441. · 2.04 Impact Factor