Topic
Discrete-time Fourier transform
About: Discrete-time Fourier transform is a research topic. Over the lifetime, 5072 publications have been published within this topic receiving 144643 citations. The topic is also known as: DTFT.
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TL;DR: A new architecture is proposed that encodes a primary image to white noise based on iterative fractional Fourier transform that can provide additional keys for encryption to make the code more difficult to break.
174 citations
TL;DR: In this paper, a technique reduisant le temps de calcul d'une transformation de Fourier discrete d'un facteur 4 a 6, sans perte significative de precision, is presented.
Abstract: On presente une technique reduisant le temps de calcul d'une transformation de Fourier discrete d'un facteur 4 a 6, sans perte significative de precision
173 citations
TL;DR: The general conditions for these mappings to be unique and cyclic are given, and the application to discrete Fourier transform (DFT) and convolution evaluation is considered.
Abstract: The mapping of one-dimensional arrays into two- or higher dimensional arrays is the basis of the fast Fourier transform (FFT) algorithms and certain fast convolution schemes. This paper gives the general conditions for these mappings to be unique and cyclic, and then considers the application to discrete Fourier transform (DFT) and convolution evaluation.
172 citations
TL;DR: In this article, a Fourier series-based method for approximation of stable infinite-dimensional linear time-invariant system models is discussed, where the Fourier coefficients can be replaced by the discrete Fourier transform coefficients while maintaining H/sup infinity / convergence.
Abstract: A Fourier series-based method for approximation of stable infinite-dimensional linear time-invariant system models is discussed. The basic idea is to compute the Fourier series coefficients of the associated transfer function T/sub d/(Z) and then take a high-order partial sum. Two results on H/sup infinity / convergence and associated error bounds of the partial sum approximation are established. It is shown that the Fourier coefficients can be replaced by the discrete Fourier transform coefficients while maintaining H/sup infinity / convergence. Thus, a fast Fourier transform algorithm can be used to compute the high-order approximation. This high-order finite-dimensional approximation can then be reduced using balanced truncation or optimal Hankel approximation leading to the final finite-dimensional approximation to the original infinite-dimensional model. This model has been tested on several transfer functions of the time-delay type with promising results. >
171 citations
TL;DR: In this article, a new method for image encryption using fractional Fourier transform and chaos theory is proposed, where the input image is combined with the first random phase mask at the object plane and is then transformed using the FFT transform.
171 citations