Results 1  10
of
22
Analysis And Design Of MinimaxOptimal Interpolators
 IEEE Trans. Signal Proc
, 1998
"... We consider a class of interpolation algorithms, including the leastsquares optimal Yen interpolator, and we derive a closedform expression for the interpolation error for interpolators of this type. The error depends on the eigenvalue distribution of a matrix which is specified for each set of sa ..."
Abstract

Cited by 17 (3 self)
 Add to MetaCart
(Show Context)
We consider a class of interpolation algorithms, including the leastsquares optimal Yen interpolator, and we derive a closedform expression for the interpolation error for interpolators of this type. The error depends on the eigenvalue distribution of a matrix which is specified for each set of sampling points. The error expression can be used to prove that the Yen interpolator is optimal. The implementation of the Yen algorithm suffers from numerical illconditioning, forcing the use of a regularized, approximate solution. We suggest a new, approximate solution, consisting of a sinckernel interpolator with specially chosen weighting coefficients. The newly designed sinckernel interpolator is compared with the usual sinc interpolator using Jacobian (area) weighting, through numerical simulations. We show that the sinc interpolator with Jacobian weighting works well only when the sampling is nearly uniform. The newly designed sinckernel interpolator is shown to perform better than ...
PostSampling Aliasing Control For Natural Images
 in Proc. IEEE Int. Conf. Acoustics, Speech, Signal Processing
, 1995
"... Sampling and reconstruction are usually analyzed under the framework of linear signal processing. Powerful tools like the Fourier transform and optimum linear filter design techniques, allow for a very precise analysis of the process. In particular, an optimum linear filter of any length can be deri ..."
Abstract

Cited by 7 (0 self)
 Add to MetaCart
(Show Context)
Sampling and reconstruction are usually analyzed under the framework of linear signal processing. Powerful tools like the Fourier transform and optimum linear filter design techniques, allow for a very precise analysis of the process. In particular, an optimum linear filter of any length can be derived under most situations. Many of these tools are not available for nonlinear systems, and it is usually difficult to find an optimum nonlinear system under any criteria. In this paper we analyze the possibility of using nonlinear filtering in the interpolation of subsampled images. We show that a very simple (5x5) nonlinear reconstruction filter outperforms (for the images analyzed) linear filters of up to 256x256, including optimum (separable) Wiener filters of any size. 1. INTRODUCTION In digital signal processing, it is often necessary to alter the sampling rate of a discrete signal. We usually refer to decimation (or subsampling) as the operation of selecting a subset of the or...
A Multirate PilotSymbolAssisted Channel Estimator for OFDM Transmitter Diversity Systems
 in Proceedings 2001 IEEE International Conference on Acoustics, Speech, and Signal Processing
, 2001
"... Orthogonal frequency division multiplexing (OFDM) transmitter diversity techniques have been shown to be efficient means of achieving near optimal diversity gain in frequencyselective fading channels. For these systems, knowledge of the channel parameters is required at the receivers for diversity ..."
Abstract

Cited by 4 (0 self)
 Add to MetaCart
(Show Context)
Orthogonal frequency division multiplexing (OFDM) transmitter diversity techniques have been shown to be efficient means of achieving near optimal diversity gain in frequencyselective fading channels. For these systems, knowledge of the channel parameters is required at the receivers for diversity combining and decoding. In this paper, we propose a low complexity, bandwidth efficient, pilotsymbol assisted channel estimator for multiple transmitter OFDM systems. The pilot symbols are constructed to be nonoverlapping in frequency to allow for the simultaneous sounding of the multiple channels. The timevarying channel responses are tracked by interpolating a set of estimates obtained through periodically transmitted pilot symbols. The effectiveness and limitations of the proposed estimator are verified by simulations.
Exact Interpolation and Iterative Subdivision Schemes
 IEEE Trans. Signal Processing
, 1995
"... In this paper we examine the circumstances under which a discretetime signal can be exactly interpolated given only every Mth sample. After pointing out the connection between designing an M fold interpolator and the construction of an M channel perfect reconstruction filter bank, we derive nece ..."
Abstract

Cited by 4 (1 self)
 Add to MetaCart
(Show Context)
In this paper we examine the circumstances under which a discretetime signal can be exactly interpolated given only every Mth sample. After pointing out the connection between designing an M fold interpolator and the construction of an M channel perfect reconstruction filter bank, we derive necessary and sufficient conditions on the signal under which exact interpolation is possible. Bandlimited signals are one obvious example, but numerous others exist. We examine these and show how the interpolators may be constructed. A main application is to iterative interpolation schemes, used for the efficient generation of smooth curves. We show that conventional bandlimited interpolators are not suitable in this context. We illustrate that a better criterion is to use interpolators that are exact for polynomial functions. Further, we demonstrate that these interpolators converge when iterated. We show how these may be designed for any polynomial degree N and any interpolation factor M . Th...
Design of a Class of Multirate Systems Using a Maximum Relative l²Error Criterion
, 1996
"... . A criterion for designing the class of multirate systems for rate#changing is presented. This criterion arises from a model#matching perspective with maximum relative # ..."
Abstract

Cited by 2 (0 self)
 Add to MetaCart
(Show Context)
. A criterion for designing the class of multirate systems for rate#changing is presented. This criterion arises from a model#matching perspective with maximum relative #
TimeScale Modification of Speech: A TimeFrequency Approach
, 1991
"... Timescale modification (TSM) is a process whereby signals are compressed or expanded in time in a manner which preserves their original frequency characteristics. This work explores TSM algorithms for sampled speech. A known approach [2] which is based on the shorttime Fourier transform (STFT) is ..."
Abstract

Cited by 1 (0 self)
 Add to MetaCart
(Show Context)
Timescale modification (TSM) is a process whereby signals are compressed or expanded in time in a manner which preserves their original frequency characteristics. This work explores TSM algorithms for sampled speech. A known approach [2] which is based on the shorttime Fourier transform (STFT) is first reviewed, then modified to provide highquality TSM of speech signals at a lower computational cost. The proposed algorithm resembles the sinusoidal speech model (SSM) based approach [9], yet incorporates new phase compensatory measures to prevent excessive structural deterioration of the timescaled signal. In addition, a novel incremental scheme for modifying polar parameters results in substantial computational savings. Sornrnaire La modification d'e'chelle de temps (MET) est un procddd qui effectue la cornpression et l'expansion temporelle de signaux sans dhformer leurs caractdristiques frdquentielles. Cet ouvrage traite d'algorithmes MET pour la parole dchantillon6e. Une mdthode connue [2] dont la thkrie est fond & sur l'analyse de Fourier de courte
Signal Processing Issues In Synthetic Aperture Radar And Computer Tomography
, 1998
"... ..."
(Show Context)
Tracking of FastFading Channels in Long Code WCDMA
, 2002
"... A new technique for blind tracking of fast fading channels in long code CDMA is proposed by exploiting multipath diversity. Based on a linear interpolation channel model, the proposed method blindly identifies a timevarying channel at arbitrary estimating points within a block up to a scale factor ..."
Abstract

Cited by 1 (1 self)
 Add to MetaCart
A new technique for blind tracking of fast fading channels in long code CDMA is proposed by exploiting multipath diversity. Based on a linear interpolation channel model, the proposed method blindly identifies a timevarying channel at arbitrary estimating points within a block up to a scale factor and increases bandwidth efficiency allowing only one pilot symbol within a block which is much larger than channel coherence time. The proposed method can be implemented using an efficient statespace inversion technique for multiuser cases. The mean square error performance of the proposed estimator is compared with CramérRao bound for interpolated channel. Modeling error and bit error rate are also evaluated using MonteCarlo simulations, and compared with the block fading model and a decisiondirected tracking technique.
The BjorkShiley valve: Detecting broken struts using standard diagnostic ultrasound instruments
, 2005
"... The BjorkShiley convexo concave (BScc) mechanical heart valve has been used in surgery between 1979 1986. In its day it was one of the most prevalent mechanical heart valves. The valve is however plagued by an increased occurrence of unexpected mechanical failure of its outlet strut compared to eq ..."
Abstract
 Add to MetaCart
The BjorkShiley convexo concave (BScc) mechanical heart valve has been used in surgery between 1979 1986. In its day it was one of the most prevalent mechanical heart valves. The valve is however plagued by an increased occurrence of unexpected mechanical failure of its outlet strut compared to equivalent valve types, with a high incidence of mortality, when it occurs. Many approaches have been attempted to noninvasively determine BScc valve integrity. None however resulted in adequate performance, mostly due to a lack of either sensitivity or specicity demonstrated in in vitro and/or in vivo studies. Two possible approaches to establish BScc valve integrity noninvasively are researched in this report. The rst revolves around the detection and comparison of the movement of both legs of the BScc valves outlet strut during the cardiac cycle. It is based on the assumption that a broken leg will have increased movement compared to either the intact leg or the
ange. The second method involves the detection of outlet strut resonance due to cardiac excitation, since the frequency of the resonance peak in the Fourier spectrum will be altered, if the strut is broken. For both methods a single element ultrasound transducer is used to direct packets