tailieunhanh - Báo cáo hóa học: " Fourier Transforms of Finite Chirps"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Fourier Transforms of Finite Chirps | Hindawi Publishing Corporation EURASIP Journal on Applied Signal Processing Volume 2006 Article ID 70204 Pages 1-7 DOI ASP 2006 70204 Fourier Transforms of Finite Chirps Peter G. Casazza1 and Matthew Fickus2 1 Department of Mathematics University of Missouri Columbia MO 65211 USA 2 Department of Mathematics and Statistics Air Force Institute of Technology Wright-Patterson AFB OH 45433 USA Received 15 October 2004 Revised 27 February 2005 Accepted 5 April 2005 Chirps arise in many signal processing applications. While chirps have been extensively studied as functions over both the real line and the integers less attention has been paid to the study of chirps over finite groups. We study the existence and properties of chirps over finite cyclic groups of integers. In particular we introduce a new definition of a finite chirp which is slightly more general than those that have been previously used. We explicitly compute the discrete Fourier transforms of these chirps yielding results that are number-theoretic in nature. As a consequence of these results we determine the degree to which the elements of certain finite tight frames are well distributed. Copyright 2006 Hindawi Publishing Corporation. All rights reserved. 1. INTRODUCTION A linear chirp is a function whose frequency changes linearly with time. For example while a wave function of the form exp 2nixt has constant frequency x the chirp exp 2ni xt yt 2 has frequencyx yt at time t e R. Chirps often arise in nature as a consequence of the Doppler effect the phenomenon by which the perceived frequency of a wave is altered whenever the wave is emanating from or reflecting off a moving body. As such chirps have historically been of great interest in applications such as radar and sonar. However the study of chirps has mostly been confined to the real line and the integers in the context of integral transforms and the chirp Z-transform respectively. Less attention has been paid to the study of chirps over .

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