Browsing by Keywords "Fourier transforms"
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About the Wigner distribution of a graded index medium and the fractional fourier transform operation
(S P I E  International Society for Optical Engineering, 1993)Upon propagation through quadratic graded index media, the Wigner distribution of the wavefunction of light rotates uniformly. As a consequence, a definition of fractional Fourier transforms based on rotating the functions ... 
Application of fractional fourier transform to finite difference time domain method
(2010)With the improvement in the computer speed and memory, Numerical Methods are frequently used in the solution of electromagnetic problems. Numerical Methods can be classified as the frequency domain and the time domain based ... 
Autofocus methodin thermal cameras basedon image histogram
(2011)In this paper, a new histogram based autofocusing method for thermal cameras is proposed. This proposed method is realized by FPGA (Field Programmable Gate Array) and DSP (Digital Signal Processor) working together and ... 
Chirp filtering in the fractional Fourier domain
(Optical Society of America, 19941110)In the Wigner domain of a onedimensional function, a certain chirp term represents a rotated line delta function. On the other hand, a fractional Fourier transform (FRT) can be associated with a rotation of the ... 
Compact optical temporal processors
(Optical Society of America, 1995)Optical signal processing can be done with timelens devices. A temporal processor based on chirpz transformers is suggested. This configuration is more compact than a conventional 4f temporal processor. On the basis of ... 
Comparative analysis of different approaches to target differentiation and localization with sonar
(Elsevier, 2003)This study compares the performances of different methods for the differentiation and localization of commonly encountered features in indoor environments. Differentiation of such features is of interest for intelligent ... 
Comparison of local and global computation and its implications for the role of optical interconnections in future nanoelectronic systems
(Elsevier, 1993)Various methods of simulating diffusion phenomena with parallel hardware are discussed. In particular methods are compared requiring local and global communication among the processors in terms of total computation time. ... 
Complex signal recovery from fractional Fourier transform intensities
(IEEE, 200404)The problem of recovering a complex signal from the magnitudes of two of its fractional Fourier transforms is addressed This corresponds to phase retrieval from the transverse intensity profiles of an optical field at two ... 
Continuous and discrete fractional fourier domain decomposition
(IEEE (Institute of Electrical and Electronics Engineers), 2000)We introduce the fractional Fourier domain decomposition for continuous and discrete signals and systems. A procedure called pruning, analogous to truncation of the singularvalue decomposition, underlies a number of ... 
Costefficient approximation of linear systems with repeated and multichannel filtering configurations
(IEEE, Piscataway, NJ, United States, 1998)It is possible to obtain either exact realizations or useful approximations of linear systems or matrixvector products arising in many different applications, by synthesizing them in the form of repeated or multichannel ... 
Design of dynamically adjustable anamorphic fractional Fourier transformer
(Elsevier BV * NorthHolland, 19970301)We form optical systems by using only free space portions and cylindrical lenses, and consider these systems as anamorphic fractional Fourier transformers. We dynamically adjust the transform order, scale factor and field ... 
Diffraction and holography from a signal processing perspective
(2006)The fact that plane waves are solutions of the Helmholtz equation in free space allows us to write the exact solution to the diffraction problem as a superposition of plane waves. The solution of other related problems can ... 
Diffraction from a wavelet point of view
(Optical Society of America, 19930601)The system impulse response representing the Fresnel diffraction is shown to form a wavelet family of functions. The scale parameter of the wavelet family represents the depth (distance). This observation relates ... 
Digital computation of the fractional Fourier transform
(Institute of Electrical and Electronics Engineers, 199609)An algorithm for efficient and accurate computation of the fractional Fourier transform is given. For signals with timebandwidth product N, the presented algorithm computes the fractional transform in O(NlogN) time. A ... 
The discrete fractional Fourier transform
(IEEE, Piscataway, NJ, United States, 2000)We propose and consolidate a definition of the discrete fractional Fourier transform which generalizes the discrete Fourier transform (DFT) in the same sense that the continuous fractional Fourier transform (FRT) generalizes ... 
The discrete fractional Fourier transformation
(IEEE, Piscataway, NJ, United States, 1996)Based on the fractional Fourier transformation of sampled periodic functions, the discrete form of the fractional Fourier transformation is obtained. It is found that only for a certain dense set of fractional orders such ... 
Durağan olmayan çok bileşenli boğucu sinyaller için yeni bir uyarlanir karişma çikarici analizi
(2005)A novel adaptive shorttime Fourier transform (STFT) implementation for the analysis of nonstationary multicomponent jammer signals is introduced. The proposed timefrequency distribution is the fusion of optimum STFTs ... 
Effect of fractional Fourier transformation on timefrequency distributions belonging to the Cohen class
(Institute of Electrical and Electronics Engineers, 199602)We consider the Cohen (1989) class of timefrequency distributions, which can be obtained from the Wigner distribution by convolving it with a kernel characterizing that distribution. We show that the timefrequency ... 
Efficient computation of the ambiguity function and the Wigner distribution on arbitrary line segments
(IEEE, Piscataway, NJ, United States, 1999)Efficient algorithms are proposed for the computation of Wigner distribution and ambiguity function samples on arbitrary line segments based on the relationship of Wigner distribution and ambiguity function with the ... 
An efficient method for electromagnetic characterization of 2D geometries in stratified media
(IEEE, 2002)A numerically efficient technique, based on the spectraldomain method of moments (MoM) in conjunction with the generalized penciloffunctions (GPOF) method, is developed for the characterization of twodimensional ...