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Signal Processing Letters, IEEE

Issue 7 • Date July 1998

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Displaying Results 1 - 9 of 9
  • On the realization of the polynomial Wigner-Ville distribution for multicomponent signals

    Page(s): 157 - 159
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (133 KB)  

    A method for the polynomial Wigner-Ville distributions realization, in the case of multicomponent signals, is presented. Using this method, one may theoretically get a sum of the polynomial Wigner-Ville distributions of each component separately. The method is illustrated by a numerical example. View full abstract»

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  • Efficient dual-tone multifrequency detection using the nonuniform discrete Fourier transform

    Page(s): 160 - 163
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (68 KB)  

    The International Telecommunication Union (ITU) recommendations for dual-tone multifrequency (DTMF) signaling are not met by conventional DTMF detectors. We present an efficient DTMF detection algorithm based on the nonuniform discrete Fourier transform that meets all of the ITU recommendations. The key innovations are the use of two sliding windows and development of sophisticated timing tests. Our algorithm requires no buffering of input samples. To perform DTMF detection on n telephone channels, our algorithm requires approximately n MIPS on a digital signal processor (DSP), 75+30n words of data memory, and 1000 words of program memory. Using the new algorithm, a single fixed-point DSP can perform ITU-compliant DTMF detection on the 24 telephone channels of a T1 time-division multiple multiplexed telecommunications line. View full abstract»

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  • On the period of sums of discrete periodic signals

    Page(s): 164 - 166
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB)  

    Unlike the continuous case, given two discrete periodic signals, their sum is always periodic. We give a characterization for the period of the sum; as shown, the least common multiple of the periods of the signals being added is not necessarily the period of the sum. Number theoretical proofs are given for the sake of rigor; examples and an interpretation in the Fourier frequency domain are given for the sake of intuition and applications. View full abstract»

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  • Design of two-channel equiripple FIR linear-phase quadrature mirror filters using the vector space projection method

    Page(s): 167 - 170
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (162 KB)  

    A new technique for designing finite impulse response (FIR) quadrature mirror filters (QMFs) is proposed. The approach is based on the vector space projection method (VSPM). Convex constraint sets and their projections that capture the properties of the desired QMFs are given. The proposed approach produces equiripple filters. This method is compared with the classical Johnston's (1980) method and is shown to have certain advantages. View full abstract»

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  • Minimum order input-output equation for linear time-varying digital filters

    Page(s): 171 - 173
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (111 KB)  

    The objective of this paper is to obtain minimum order input-output equations for a class of linear time-varying digital filters in state equation with constant dimension state vector. It is shown that the minimum order of the input-output equation may not be identical to the dimension of the state vector and there exists a nonunique solution for the minimum order input-output equation. View full abstract»

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  • On the evaluation of estimated impulse responses

    Page(s): 174 - 176
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (89 KB)  

    We discuss the philosophy of evaluating estimated impulse responses for applications in which the overall scaling or gain is irrelevant, as, for example, in blind channel identification. We argue that no matter how the estimate is obtained, the performance should be independently evaluated using an error measure that is appropriate for a problem of this class. Of several possible error measures, the normalized projection error, which is obtained by minimizing the l/sub 2/ norm over all possible gain values, seems to be the most natural and consistent. An example demonstrates that using an inappropriate error measure can produce misleading results. View full abstract»

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  • On the Cramer-Rao bound under parametric constraints

    Page(s): 177 - 179
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (149 KB)  

    This paper presents a simple expression for the Cramer-Rao bound (CRB) for parametric estimation under differentiable, deterministic constraints on the parameters. In contrast to previous works, the constrained CRB presented does not require that the Fisher information matrix (FIM) for the unconstrained problem be of full rank. This is a useful extension because, for several signal processing problems (such as blind channel identification), the unconstrained problem is unidentifiable. Our expression for the constrained CRB depends only on the unconstrained FIM and a basis of the nullspace of the constraint's gradient matrix. We show that our constrained CRB formula reduces to the known expression when the FIM for the unconstrained problem is nonsingular. A necessary and sufficient condition for the existence of the constrained CRB is also derived. View full abstract»

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  • Subspace methods for blind identification of multichannel FIR filters using space-time contraction of cumulants

    Page(s): 180 - 184
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (239 KB)  

    We show that the popular subspace method for identification of multichannel systems can be implemented using particular contractions of higher-order cumulants, in the case of independent, identically distributed (i.i.d.) inputs. The algorithm appears to outperform the traditional correlation-based subspace algorithm in low signal-to-noise-ratio (SNR) and/or correlated noise. View full abstract»

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  • An H/sup /spl infin// approach to mitigate the effects of array uncertainties on the MUSIC algorithm

    Page(s): 185 - 188
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (133 KB)  

    In this letter, a novel robust technique is proposed to mitigate the degrading effects of finite sampling and imprecise modeling on the performance of the multiple signal classification (MUSIC) algorithm, Initially, a new array-signal state space model is developed, which is valid for any array geometry. Based on this model, formulated in an H/sup /spl infin// framework, a new robust direction-finding approach has been proposed. This theoretical framework is supported by simulation examples that demonstrate the robustness of the new technique to the presence of array uncertainties and signal correlation. View full abstract»

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The IEEE Signal Processing Letters is a monthly, archival publication designed to provide rapid dissemination of original, cutting-edge ideas and timely, significant contributions in signal, image, speech, language and audio processing.

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Editor-in-Chief
Peter Willett
University of Connecticut
Storrs, CT 06269
peter.willett@uconn.edu