Showing papers on "Quadrature mirror filter published in 2000"

Wavelet-based multicarrier transmission over multipath wireless channels

Abstract: The conventional Fourier-based complex exponential carriers of a multicarrier system are replaced with orthonormal wavelets in order to reduce the interference. The wavelets are derived from a multistage tree-structured Haar and Daubechies orthonormal quadrature mirror filter (QMF) bank. Compared with the conventional OFDM, it is found that these wavelets reduce the power of ISI and ICI.

Method of multi-level facial image recognition and system using the same

Abstract: A quadrature mirror filter is applied to decompose an image into at least two sub-images each having a different resolution. These decomposed sub-images pass through self-organizing map neural networks for performing a non-supervisory classification learning. In a testing stage, the recognition process is performed from sub-images having a lower resolution. If the image can not be identified in this low resolution, the possible candidates are further recognized in a higher level of resolution.

Seismic data processing method for data acquired using overlapping vibratory sweeps

Abstract: A system and method for attenuating noise in vibroseis data acquisition. In particular, according to the invention, several preferred methods are discloses that are particularly useful for attenuating noise in seismic data acquired by slip sweep vibroseis techniques. The techniques disclosed involve band-splitting in the time-frequency domain using mirror-filtering, such as a quadrature mirror filter. A noise estimate is made according to which the data is normalized and summed. The time frequency data then reconstructed and transformed back into time domain for further processing.

Fully balanced current-tunable sinusoidal quadrature oscillator

Abstract: An integrable current-tunable sinusoidal quadrature oscillator is presented. A current-tunable all-pass filter using a signal-differencing technique is realized as the frequency-selective network. The implementation is fully balanced so as to enable accurate quadrature signals with symmetry. The oscillation frequency is current-tunable over a wide-frequency sweep range of approximately three orders of magnitude. The quadrature signals possess the amplitude matching and the quadrature phase matching of better than 0.004dB and 0.15°, respectively. The maximum useful frequency of oscillation is in excess of 8MHz. Total harmonic distortions are less than 0.5%.

A new waveform interpolation coding scheme based on pitch synchronous wavelet transform decomposition

Abstract: This correspondence uses a pitch synchronous wavelet transform (PSWT) as an alternative characteristic waveform decomposition method for the waveform interpolation (WI) paradigm. The proposed method has the benefit of providing additional scalability in quantization than the existing WI decomposition to meet desired quality requirements. The PSWT is implemented as a quadrature mirror filter bank and decomposes the characteristic waveform surface into a series of reduced time resolution surfaces. Efficient quantization of these surfaces is achieved by exploiting their perceptual importance and inherent transmission rate requirements. The multiresolution representation has the additional benefit of more flexible parameter quantization, allowing a more accurate description of perceptually important scales, especially at higher coding rates. The proposed PSWT-WI coder is very well suited to high quality speech storage applications.

A successive reoptimization approach for the design of discrete coefficient perfect reconstruction lattice filter bank

Abstract: The lattice structure quadrature mirror filter (QMF) bank structurally guarantees the perfect reconstruction (PR) property. Thus, it is eminently suitable for hardware realization even under the severe coefficient quantization condition. Nevertheless, its frequency response is still adversely affected by coefficient quantization. In this paper, a novel technique is presented for the design of lattice structure PRQMF banks subject to discrete coefficient value constraints. In our technique, the coefficient values are quantized sequentially one at a time. After each coefficient is being quantized, the remaining unquantized coefficient values are reoptimized to partially compensate for the frequency response deviation caused by the quantization of that coefficient value. The order of selection of the coefficients for quantization is based on a coefficient sensitivity measure. Coefficients with higher sensitivity measures are quantized earlier than coefficients with lower sensitivity measures. The improvement in the frequency response ripple magnitude achieved by our algorithm over that by simple rounding of coefficient values differs widely from example to example ranging from a fraction of a dB to over 10 dB.

Robust spatiotemporal quadrature filter for multiphase stepping

Abstract: A robust algorithm for phase recovery from multi-phase-stepping images is presented. This algorithm is based on the minimization of an energy (cost) functional and is equivalent to the simultaneous application of a fixed temporal quadrature filter and a spatial adaptive quadrature filter to the phase-stepping pattern ensemble. The algorithm, believed to be new, is specially suited for those applications in which a large number of phase-stepping images may be obtained, e.g., profilometry with a computer-controlled fringe projector. We discuss the selection of parameter values and present examples of its performance in both synthetic and real image sequences.

Further results on reconstruction methods for processing finite-length signals with perfect reconstruction filter banks

Abstract: In de Queiroz and Rao (1995), new expressions were developed for the perfect reconstruction (PR) of the boundary regions of a finite-length signal after subband processing using uniform and paraunitary filter banks (PUFBs). The present paper points out an incorrect assertion in the previous paper regarding the sufficiency of its solution and presents the general existence (applicability) conditions for the method. Furthermore, we extend the method to encompass perfect reconstruction filter banks, i.e., not only the paraunitary case.

Generalized frame multiresolution analysis of abstract Hilbert spaces and their applications

Abstract: We define a very generic class of multiresolution analysis of abstract Hilbert spaces. Their core subspaces have a frame produced by the action of an abelian unitary group on a perhaps infinite subset of the core subspace, which we call frame multi scaling vector set. We characterize the associated frame multi wavelet vector sets by generalizing the concept of the low and high pass filters and the Quadrature Mirror filter condition. We include an extensive overview of related work of other and we conclude with some examples.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A general design of mixed IIR-FIR two channel QMF bank

Abstract: A general family of mixed IIR/FIR two-channel QMF filter banks with near perfect reconstruction (NPR) is presented. The design method is general in the sense that all possible distortions (aliasing, imaging, amplitude and phase distorsions) can be simultaneously and arbitrarily minimized. The method is based on a simple algorithm, also included, to approximate unstable all-pole filters with FIR filters. The resulting filter bank is efficient because a polyphase implementation is possible and delay is low compared to conventional FIR filter banks. It is also shown that some well-known two-channel FIR and IIR filter banks are particular classes of the proposed one. Examples are also included.

A simple method for designing pseudo QMF banks

Abstract: The traditional designs for the prototype filter of M-band pseudo quadrature mirror filter (QMF) banks usually involve nonlinear optimization. A simple design approach that involves the optimization of only a single parameter is presented. In this method, the prototype filter is formulated as an interpolated FIR filter and is indirectly designed by varying the passband edge of the model filter. A design example is presented to show that very good design can be obtained in spite of the limit of the formulation.

Design of Two-Channel Low-Delay FIR Filter Banks using Constrained Optimization

Abstract: This paper shows the efficiency of using constrained optimization for designing two-channel low-delay finite impulse response filter banks. The filter banks under consideration are quadrature mirror filter (QMF) banks and perfect reconstruction (PR) biorthogonal filter banks. The design problems for both types of banks are stated as constrained minimization problems in forms that enable us to minimize the maximum of the stopband energies of the analysis filter(s) subject to the given passband and transition band constraints of the filter(s) as well as subject to the given allowable reconstruction error for QMF banks or the PR property for biorthogonal filter banks. For solving the given optimization problems a modified Dutta-Vidyasagar optimization technique has been used. The efficiency of the proposed design methods is illustrated by means of some examples.

On the design of 2-band FIR QMF filter banks using WLS technique

Abstract: In the digital filter bank context, many design methods have been proposed. Most of them are for 2-band QMF FIR filter banks. The paper considers the design of (QMF) quadrature mirror filter banks using the iterative method proposed by Chang-Kann Chen and Ju-Hong Lee (1992). Simulations show that the Chen and Lee method needs much iteration. It was examined and improved by using certain modifications based on the weighted least squares (WLS) updating scheme proposed by S. Sunder et al. (1994) to design two channel QMF filter banks. As the current weighting function is adjusted from iteration to iteration, QMF bank design with equiripple reconstruction error and stopband error can be achieved. Computer simulation shows that the proposed approach produced better results than those reported previously by author Chen and Lee. The paper concludes with design examples that illustrate the effectiveness of the approach on the efficiency and performance. Furthermore, the proposed approach requires less iterations compared with existing methods and leads to filter bank design with improved performance. The resultant filter banks are efficient in terms of computational requirements.

Comparative study for optimisation of causal IIR perfect reconstruction filter banks

Abstract: Comparative study for optimisation of causal infinite impulse response (IIR) filters with applications to perfect reconstruction quadrature mirror filter (QMF) banks is presented. A hybrid procedure is applied where a constrained genetic algorithm is first used to search the objective function landscape for a promising valley. Sub-optimal filter parameters are then further optimised using four different methods. These are: new GA based 'creep code', gradient based constrained Sequential Quadratic programming method and Quasi-Newton method and non-gradient based downhill Simplex method. Finally, a comparison is drawn between each of the four methods of optimisation.

H2/H, Signal Reconstruction in Noisy Filter Bank Systems

Abstract: This paper investigates signal reconstruction in the multirate filter bank systems with noisy subband paths. It casts the problem of signal reconstruction into a problem of mixed H2/H, control, and uses the standard results of mixed H2/H, synthesis to design an IIR synthesis filter bank.

A modified design to eliminate passband anomaly in weighted minimax quadrature mirror filters

Abstract: It is known that quadrature mirror filters (QMFs) designed using the algorithm in Lim and Yang (1993) suffer from passband anomaly under certain conditions. A modification to this algorithm was proposed in Goh et al. (1996) to overcome this anomaly. However, this design is not a general solution for different stopband edge frequencies. In this paper, we propose a more robust technique to design QMFs, by modifying the frequency domain approach proposed in Lim and Yang with a better initial guess filter obtained by frequency sampling design. The QMF designed employing the proposed technique overcomes the passband anomaly and has excellent frequency response characteristics that are considerably better than those obtained using earlier methods.

Design of two-channel low-delay FIR filter banks using constrained optimization

Abstract: This paper shows the efficiency of using constrained optimization for designing two-channel low-delay finite impulse response filter banks. The filter banks under consideration are quadrature mirror filter (QMF) banks and perfect reconstruction (PR) biorthogonal filter banks. The design problems for both types of banks are stated as constrained minimization problems in forms that enables us to minimize the maximum of the stopband energies of the analysis filter(s) subject to the given passband and transition band constraints of the filter(s) as well as subject to the given allowable reconstruction error for QMF banks or the PR property for biorthogonal filter banks. For solving the given optimization problems a modified Dutta-Vidyasagar (1977) optimization technique has been used. The efficiency of the proposed design methods is illustrated by means of some examples.

Orthogonal Wavelets via Filter Banks: Theory and Applications

Abstract: Wavelets are used in many applications, including image processing, signal analysis and seismology. The critical problem is the representation of a signal using a small number of computable functions, such that it is represented in a concise and computationally efficient form. It is shown that wavelets are closely related to filter banks (sub band filtering) and that there is a direct analogy between multiresolution analysis in continuous time and a filter bank in discrete time. This provides a clear physical interpretation of the approximation and detail spaces of multiresolution analysis in terms of the frequency bands of a signal. Only orthogonal wavelets, which are derived from orthogonal filter banks, are discussed. Several examples and applications are considered.

Discrete wavelet transform apparatus of a lattice tree

Abstract: PURPOSE: A discrete wavelet transform apparatus is provided to perform a transformation of all resolution levels by use of a quadrature mirror filter bank of a lattice tree. CONSTITUTION: The discrete wavelet transform (DWT) apparatus (100) comprises: a plurality of serial-connected lattice stages (PE0,..., PEm-1); delay adjusters (24) inserted between each lattice; and a data form converter (DFC) (23) installed between feedback output (S¬j(1)) and an input (u(n)) and a first lattice stage (PE0). Between the input (u(n)) and the data form converter (23), a multiplier (s) is installed as a scale factor. And the multiplier (s) is installed at a previous stage of the data form converter (23) so as to reduce the number of the multipliers.

A WLS algorithm for the design of low-delay quadrature mirror filter banks

Abstract: This paper presents a weighted lease squares (WLS) algorithm for the design of low-delay quadrature mirror filter (QMF) banks with a prescribed number of zeros of the low-pass filter at /spl omega/=/spl pi/: this is desirable when the filter bank is used for the wavelet decomposition of a signal. The algorithm needs only a few iterations to obtain a solution which optimizes the filter bank design problem in the weighted minimax sense. A design example is provided for illustration.

Impedance matrix compression using an effective quadrature filter

Abstract: An effective quadrature mirror filter (QMF) proposed by Vaidyanathan has been used to solve 2D scattering problems. QMF has been popular for some time in digital signal processing, under the names of multirate sampling, wavelets, etc. In this work, the impulse response coefficients of QMF were used to construct the wavelet transform matrix. Using the matrix to transform the impedance matrices of 2D scatterers produces highly sparse moment matrices that can be solved efficiently. Such a presentation provides better sparsity than the celebrated and widely used Daubechies wavelets. These QMF coefficients are dependent on the filter parameters such as transition bandwidth and filter length. It was found that the sharper the transition bandwidth, the greater the reduction in nonzero elements of the impedance matrix. It also can be applied in the wavelet packet algorithm to further sparsify the impedance matrix. Numerical examples are given to demonstrate the effectiveness and validity of our finding.

Apparatus and method for generating accurate quadrature over a frequency range

Abstract: The invention produces an accurate quadrature relationship for a range of frequencies using passive components in the primary quadrature splitting circuits. A reference oscillator (202) generates a reference signal which is fed to a conventional passive quadrature splitter circuit (204). However, since the reference circuit provides signals over a range of frequencies, the output signals of the passive quadrature splitter may not have an accurate quadrature relationship. The output signals of the passive quadrature splitter are then equalized in magnitude, and the sum and difference of the signals are produced, which will be in an accurate quadrature relationship.

Necessary conditions on the lifting scheme for existence of wavelets in L/sub 2/(R)

Abstract: Over the years many different libraries of biorthogonal wavelets have been designed. In addition, the lifting scheme has been developed which unifies the design of biorthogonal wavelets using a simple approach. The lifting scheme allows the custom design of wavelets while maintaining the biorthogonal constraint on the filter bank. A drawback of the lifting scheme is that it does not guarantee that the wavelet associated with the iterated filter bank exists in L/sub 2/(R). In practice this raises the possibility that the filter bank may produce numerical artifacts. We present some necessary conditions on the lifting scheme for the resulting wavelets to exist in L/sub 2/(R). Using these conditions, we show how valid wavelet bases can be easily generated from randomly perturbed biorthogonal filter banks.

Pseudo-QMF filter banks for audio signals subband coding

Abstract: Pseudo-QMF banks in which there is no optimization involved in order to obtain the prototype filter used in the cosine modulation are an advance that simplifies the system design. In this paper, three filter bank design methods that satisfy this requirement-all of them employ any conventional designing technique-are proposed. These filter banks do not introduce phase distortion, their aliasing is comparable to the stopband gain of the prototype filter and amplitude distortion can be really minimized. The differences among them are prototype filter specifications and the initial phase factor election. When the prototype filters are appropriately designed, the total error on the reconstructed output signal is reduced. An example where an audio signal is the input signal is included.

Canonical angles, subspace partitioning, and hyrbrid wavelet packets

Abstract: In previous work, hybrid wavelet packets were introduced as a generalization of wavelet packets in which the choice of quadrature mirror filter (QMF) is selected adaptively within the wavelet packet analysis. This was motivated by the observation that for certain classes of signals, the choice of appropriate QMF is not only signal dependent, but may be scale dependent as well. Best Basis selection was generalized to provide a means of optimizing the representation of a given signal. This method can be viewed as an adaptive partitioning of signal subspaces. In such a scheme it is important to determine a small number of QMFs which will provide some diversity in the partitioning of the subspaces. In the current work, canonical correlations and canonical angles are used to quantify the difference between subspaces spanned by two filter pairs. Preliminary results indicate the utility of this method as a data independent metric for filter comparison.

Two-Dimensional Wavelets with Complementary Filter Banks

Abstract: In this paper, the Two-Dimensional (2D) Complementary Filter (CF) Banks, a signal processing technique which can be used to get scaling and wavelets functions, are presented. The 2D multirate signal processing theory and complementary filters properties are the base of CF Banks, permitting us to consider different types of sampling and filters. Two-dimensional nonseparable quincunx, rectangular and circular complementary filters are designed for an alias free decimation and interpolation. When CF bank is implemented with quincunx sampling and filters, perfect reconstruction is achieved and although it is not reached in others cases, the analysis and synthesis are performed without aliasing. The CF banks are related with wavelet theory and procedures to get 2D scaling and bandpass wavelets functions from the L-level filter bank tree structure iteratively are shown. We illustrate scaling and wavelets functions convergence as the level of decomposition increases.

A VVLS Algorithm For The Design Of Low-Dela y Quadrature Filter Banks

Abstract: This paper presents a weighted least squares(WLS) algorithm for the design of low-delay quadrature mirror filter (QMF) banks with a prescribed number of zeros of the low-pass filter at w = T: this is desirable when the filter bank is used for the wavelet decomposition of a signal. The algorithm needs only a few iterations to obtain a solution which optimizes the filter bank design problem in the weighted minimax sense. A design example is provided for illustration. I. INTRODUCTION Quadrature mirror filter (QMF) banks are used extensively in subband coding of digital audio signals and images. These filter banks decompose an input signal into its subband components (analysis phase) and reconstruct the input signal from the sub-sampled version of these subband components with little or no distortion (synthe