Topic
Time–frequency analysis
About: Time–frequency analysis is a research topic. Over the lifetime, 5407 publications have been published within this topic receiving 104346 citations.
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TL;DR: In this paper, it was shown that an overcomplete Gabor frame has infinite excess, and in fact there exists an infinite subset of points that can be removed yet leave a frame.
33 citations
TL;DR: In this article, the Hilbert transform is used to analyze the instantaneous frequency of system responses to typical identification signals and the potential for identifying some time-varying patterns is shown.
33 citations
TL;DR: The method is based on the joint time-frequency signal analysis and uses the Wigner-Ville and the spectrogram distributions and results show good agreement between exact and reconstructed functions.
Abstract: We propose a method to reconstruct the grating period in fiber grating structures from the field reflection coefficient or the related impulse response. The method is based on the joint time–frequency signal analysis and uses the Wigner–Ville and the spectrogram distributions. Results show good agreement between exact and reconstructed functions.
33 citations
TL;DR: A hierarchical Maximum Likelihood Adaptive Neural System (MLANS), a new type of neural network that incorporates a model-based concept, leading to greatly increased learning efficiency compared to conventional, nonparametric neural networks is proposed for transient signal processing.
33 citations
24 Jun 2007
TL;DR: Based on the regularly spaced pilot pattern, alternative patterns are derived that preserve the non-aliasing property by hopping the scan lines in either time domain or frequency domain, but not both.
Abstract: In an OFDM system, channel estimation can be considered as sampling the time-frequency response of the channel through a number of known pilot symbols placed across the time-frequency plane. Sampling theory dictates that the pilot insertion frequency must be above the Nyquist rates in both time and frequency to avoid aliasing of the delay-Doppler response. Based on the regularly spaced pilot pattern, we can derive alternative patterns that preserve the non-aliasing property by hopping the scan lines in either time domain or frequency domain, but not both. From this extended set of patterns, we find ones with properties that, in addition to channel estimation, can achieve responsively other synchronization tasks such as initial time-frequency offset estimation and device identification. The ambiguity function analysis frequently used in radar signal design leads to a periodic time-hopping pattern based on the costas array that has minimal coincidences with its circular time-frequency shifts, which can be used for the identification of multiple devices. The hopping in time also greatly increases the pilot's time support, thus enabling the quick initial acquisition of timing and frequency offset with very short observation.
33 citations