Now showing items 1-20 of 76

    • About the Wigner distribution of a graded index medium and the fractional fourier transform operation 

      Ozaktas, H. M.; Mendlovic, D.; Lohmann, A. W. (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 

      Sayin I.; Arikan F.; Arikan, O. (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 

      Turgay, E.; Teke, O. (2011)
      In this paper, a new histogram based auto-focusing 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 

      Dorsch, R. G.; Lohmann, A. W.; Bitran, Y.; Mendlovic, D.; Ozaktas, H. M. (Optical Society of America, 1994-11-10)
      In the Wigner domain of a one-dimensional 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 

      Mendlovic, D.; Melamed, O.; Ozaktas, H. M. (Optical Society of America, 1995)
      Optical signal processing can be done with time-lens devices. A temporal processor based on chirp-z transformers is suggested. This configuration is more compact than a conventional 4-f temporal processor. On the basis of ...
    • Comparative analysis of different approaches to target differentiation and localization with sonar 

      Barshan, B.; Ayrulu, B. (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 

      Ozaktas, H. M.; Goodman J. W. (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 

      Ertosun, M. G.; Atlı, H.; Özaktaş, H. M.; Barshan, B. (IEEE, 2004-04)
      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 

      Kutay, M. A.; Özaktaş, H. M.; Yetik, İ. Ş.; Özaktaş, H. (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 singular-value decomposition, underlies a number of ...
    • Cost-efficient approximation of linear systems with repeated and multi-channel filtering configurations 

      Kutay, M. A.; Erden, M. F.; Ozaktas, H. M.; Arikan, O.; Candan, Ç.; Güleryüz, Ö. (IEEE, Piscataway, NJ, United States, 1998)
      It is possible to obtain either exact realizations or useful approximations of linear systems or matrix-vector products arising in many different applications, by synthesizing them in the form of repeated or multi-channel ...
    • Design of dynamically adjustable anamorphic fractional Fourier transformer 

      Erden, M. F.; Ozaktas, H. M.; Sahin, A.; Mendlovic, D. (Elsevier BV * North-Holland, 1997-03-01)
      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 

      Onural L.; Ozaktas, H., M. (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 

      Onural, L. (Optical Society of America, 1993-06-01)
      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 

      Ozaktas, H. M.; Arıkan, O.; Kutay, M. A.; Bozdağı, G. (Institute of Electrical and Electronics Engineers, 1996-09)
      An algorithm for efficient and accurate computation of the fractional Fourier transform is given. For signals with time-bandwidth product N, the presented algorithm computes the fractional transform in O(NlogN) time. A ...
    • The discrete fractional Fourier transform 

      Candan, Ç.; Kutay, M. A.; Ozaktas, H. M. (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 

      Arıkan, O.; Kutay, M. A.; Özaktaş, H. M.; Akdemir, Ö. K. (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 

      Durak L.; Arikan, O.; Song V.I. (2005)
      A novel adaptive short-time Fourier transform (STFT) implementation for the analysis of non-stationary multi-component jammer signals is introduced. The proposed time-frequency distribution is the fusion of optimum STFTs ...
    • Effect of fractional Fourier transformation on time-frequency distributions belonging to the Cohen class 

      Ozaktas, H. M.; Erkaya, N.; Kutay, M. A. (Institute of Electrical and Electronics Engineers, 1996-02)
      We consider the Cohen (1989) class of time-frequency distributions, which can be obtained from the Wigner distribution by convolving it with a kernel characterizing that distribution. We show that the time-frequency ...
    • Efficient computation of the ambiguity function and the Wigner distribution on arbitrary line segments 

      Özdemir, A. K.; Arıkan, O. (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 2-D geometries in stratified media 

      Aksun, M. I.; Çalışkan, F.; Gürel, L. (IEEE, 2002)
      A numerically efficient technique, based on the spectral-domain method of moments (MoM) in conjunction with the generalized pencil-of-functions (GPOF) method, is developed for the characterization of two-dimensional ...