Showing papers on "Quadrature mirror filter published in 2003"

Active polyphase inverter filter for quadrature signal generation

Abstract: A quadrature signal generator receives a differential input signal and generates quadrature output signals that are 90 degrees out-of-phase with each other. The quadrature generator includes a coarse stage and a plurality of refinement stages. The coarse stage generates quadrature signals that may have some phase error, and the refinement stages process the quadrature signals to reduce any phase error. The refinement stages receive quadrature signals from the output of the coarse stage, and processes the quadrature signals to reduce the phase errors. The coarse stage and the refinement stages are configured using delay circuits that can be implemented with inverter circuits, such as, for example, CMOS inverter circuits. In the refinement stages, corresponding outputs of the delay stages are averaged together to reduce the quadrature phase error.

Orthogonal Hilbert transform filter banks and wavelets

Abstract: Complex wavelet transforms offer the opportunity to perform directional and coherent processing based on the local magnitude and phase of signals and images. Although denoising, segmentation, and image enhancement are significantly improved using complex wavelets, the redundancy of most current transforms hinders their application in compression and related problems. In this paper we introduce a new orthonormal complex wavelet transform with no redundancy for both real- and complex-valued signals. The transform's filter bank features a real low pass filter and two complex high pass filters arranged in a critically sampled three-band structure. Placing symmetry and orthogonality constraints on these filters, we find that each high-pass filter can be factored into a real high pass filter followed by an approximate Hilbert transform filter.

Two-channel FIR filter banks utilizing the FRM approach

Abstract: The frequency-response masking (FRM) approach has been introduced as a means of generating narrow transition band linear-phase finite impulse response (FIR) filters with a low arithmetic complexity. This paper proposes an approach for synthesizing two-channel maximally decimated FIR filter banks utilizing the FRM technique. For this purpose, a new class of FRM filters is introduced. Filters belonging to this class are used for synthesizing nonlinear-phase analysis and synthesis filters for two types of two-channel filter banks. For the first type, there exist no phase distortion and aliasing errors, but this type suffers from a small amplitude distortion as for the well-known quadrature mirror filter (QMF) banks. Compared to conventional QMF filter banks, the proposed banks lower significantly the overall arithmetic complexity at the expense of a somewhat increased overall filter bank delay in applications demanding narrow transition bands. For the second type, there are also small aliasing errors, allowing one to reduce the arithmetic complexity even further. Efficient structures are introduced for implementing the proposed filter banks, and algorithms are described for maximizing the stopband attenuations of the analysis and synthesis filters in the minimax sense subject to the given allowable amplitude and/or aliasing errors. Examples are included illustrating the benefits provided by the proposed filter banks.

A reconfigurable multi-standard channelizer using QMF trees for software radio receivers

Abstract: The flexibility of a software-defined radio (SRR) depends on its capability to operate in multi-standard wireless communication environments. The most computationally intensive part of wideband receivers is the channelizer, which extracts multiple narrowband signals from adjacent frequency hands. In an SDR receiver, the compatibility of the channelizer with different communication standards is guaranteed by its reconfigurability. This paper presents an efficient channelizer that has a reconfigurable architecture based on quadrature mirror filter bank (QMF) trees. We show that the channelizer can he efficiently implemented using common subexpression based filter structures. An example of dual-mode global system for mobile communication (GSM)/personal digital cellular (PDC) channelizer is discussed to illustrate the proposed design methodology.

Design of two-channel linear-phase QMF banks based on real IIR all-pass filters

Abstract: The design of two-channel linear-phase quadrature mirror filter (QMF) banks constructed by real infinite impulse response (IIR) digital all-pass filters is considered. The design problem is appropriately formulated to result in a simple optimisation problem. Using a variant of Karmarkar's algorithm, the optimisation problem can be efficiently solved through a frequency sampling and iterative approximation method to find the real coefficients for the IIR digital all-pass filters. The resulting two-channel QMF banks possess an approximately linear phase response without magnitude distortion. The effectiveness of the proposed technique is achieved by forming an appropriate Chebyshev approximation of the desired phase response and then finding its solution from a linear subspace in a few iterations. Finally, several simulation examples are presented for illustration and comparison.

Scheme for subband adaptive beamforming array implementation using quadrature mirror filter banks

Abstract: A novel scheme for a subband adaptive beamforming array (SABA) implementation is presented. The higher subband output signal is optimised and then multiplied with a factor to generate an output similar to the optimised lower subband. Both outputs are then combined to produce the desired signal. This arrangement reduces circuit complexity as well as the cost of the SABA, while maintaining the same beamforming performance.

Wavelet-based multicarrier CDMA system and its corresponding multi-user detection

Abstract: A novel digital transmission system based on wavelet signalling has been proposed and analysed. The basic system consists of a bank of filters derived using the quadrature constrained least square (QCLS) algorithm and satisfying the perfect reconstructed quadrature mirror filter (PR-QMF) theory. A multicarrier CDMA system is constructed using this technique, where a user's data is spread in the frequency domain and constraints are imposed to ensure channel orthogonality. The system exploits the localisation properties of the wavelets in time and frequency to develop data channels that have compact PSD characteristics and are resilient in an environment exposed to fading. Practical implementation of the wavelet transmission system using a bank of polyphase filters is considered. Simulation results are presented which show the wavelet system can better combat ISI and multiple access interference than an FFT-based multicarrier modulation system when both systems operate in identical fading environments. A wavelet detection scheme based on the MMSE criterion and then made adaptive using the LMS algorithm is theoretically analysed and software simulated. The proposed wavelet detector is near–far resistant and shows better BER performance compared with a decorrelator, but with higher computation costs.

Multicriterion optimized QMF Bank design

Abstract: The quadrature mirror filter (QMF) bank with multicriterion constraints such as minimal aliasing and/or minimal error coding is among the most important problems in filterbank design, for solving which linear algebra-based methods are still heuristic and do not always work, especially for large filter length. It is shown in this paper that this problem can be reduced either to convex linear matrix inequality (LMI) optimization (when filters are of nonlinear phase) or to semi-infinite linear (SIP) programming (when filters are of linear phase), which can be very efficiently solved either by the standard LMI solvers or our previously developed SIP solver. The proposed computationally tractable optimization formulations are confirmed by several simulations.

DSP implementation of low-complexity equalizer for multicarrier systems

Abstract: Efficient complex perfect reconstruction filter bank structures based on cosine and sine modulated filter bank sections have recently been introduced. In the transmultiplexer configuration, these filter banks can be used as a basis when developing filter bank based multicarrier systems for wireless communications. Also a simple channel equalization concept for such systems has been proposed recently. This so-called ASCET structure uses an oversampled analysis bank in receiver end to be able to do the equalization in per-carrier way. In this paper we explore the possibilities of implementing the receiver bank and equalizer sections with a digital signal processor (DSP), using the TMS320C5510 as the platform. Both single- processor and two-processor designs are considered. With realistic filter bank parameters, about 1 MHz and 2 MHz sampling rates are possible in the two cases, respectively.

Mirror suppression circuit and receiver using such circuit

Abstract: A mirror suppression circuit includes a first quadrature signal path coupled between quadrature signal input and output terminals and an error correction circuit for correction of amplitude and phase errors in a carrier modulated quadrature signal. To obtain a suppression of both amplitude and phase imbalance of the carrier modulated quadrature signal as well as signal amplitude variations, a quadrature output of the error correction circuit is coupled to an error detection circuit. The error detection circuit detects amplitude and phase errors and provides amplitude and phase control signals to the error correction circuit for a negative feed back of the amplitude and phase errors. The amplitude and phase control signals vary with products of components of the quadrature signal and components of a quadrature reference signal.

Low-order IIR filter bank design

Abstract: The advantage of IIR filters over FIR ones is that the former require a much lower order to obtain the desired response specifications. However, the existing deterministic techniques for IIR filter bank design based on heuristic usually lead to too high order IIR filters and thus cannot be practically used. In this paper, we propose new method to solve the low-order IIR filter bank design, which is based on linear matrix inequalities (LMI) optimization. Our focus is the QMF bank design, although other IIR filter related problems can be treated and solved in similar way.

Adaptive wavelet filter design for optimized image source encoding

Abstract: Despite intensive research being conducted on the topic of adaptive filter design in general, adaptive filter design in the discrete wavelet transform (DWT) domain with specific constraints is still an active research area. We have developed a method for the design of a 2-channel perfect-reconstruction adaptive wavelet filter which is optimized under minimum energy constraints in specific bands. The optimal 2-channel conjugate quadrature filter (CQF) bank has been designed using sequential quadratic programming techniques for nonlinear, nonconvex functions in general, although finding a global minimum is not guaranteed. However, such a filter can be effectively used with a wavelet based image encoder for high fidelity transmission of large image data sets at low bit rates.

Mirror suppression circuit in a quadrature demodulator

Abstract: Mirror suppression circuit and receiver using such mirror suppression circuit comprising a first quadrature signal path coupled between quadrature signal input and output terminals and including an error correction circuit for correction of amplitude and phase errors in a carrier modulated quadrature signal comprising a pair of in-phase and phase quadrature signal components. To obtain a suppression of both amplitude and phase imbalance of said carrier modulated quadrature signal as well as signal amplitude variations, a quadrature output of said error correction circuit being coupled through a first filter circuit for a selection of said quadrature signal to a first quadrature input of an error detection circuit, said first quadrature signal path being coupled prior to said first filter circuit through a second quadrature signal path to a second quadrature input of said error detection circuit, said error detection circuit detecting amplitude and phase errors and providing amplitude and phase control signals to amplitude and phase control inputs of said error correction circuit for a negative feed back of said amplitude and phase errors to said error correction circuit, said amplitude control signal varying with at least one of products Iw*Iref and Qw*Qref and said phase control signal varying with at least one of products Iw*Qref and Qw*Iref, Iw and Qw, respectively Iref and Qref, representing the in-phase and phase quadrature signal components of said quadrature signal at the first quadrature input of the error detection circuit, respectively the in-phase and phase quadrature signal components of a quadrature reference signal occurring at the negative carrier frequency of said quadrature signal at the second quadrature input of the error detection circuit.

Filter banks, wavelets, and frames with applications in computer vision and image processing (a review)

Abstract: The purpose of this article is to present some of the fundamental principles of filter banks, wavelets and frames and their connections, with special emphasis on applications in computer vision and image processing. This is a vast field and we can only give a glimpse of it. We start with a short historical review and a rather broad discussion of filter banks, wavelets and frames. It is discussed how filter banks and wavelets are connected via multiresolution. Some of the most important structures and properties are presented but hardly no mathematical details are given. We focus especially on directional filter banks and wavelets, on analysis and extraction of directional features in images and image sequences. A system for motion estimation (estimation of optical flow) is presented.

A Proof of the Necessary Condition for Perfect Reconstruction of Signals Using the Two-channel Wavelet Filter Bank

Abstract: Wavelet representation of signals and images is very useful for compression purposes. To obtain a wavelet representation by splitting a digital signal into two subsampled sygnals in a two-channel filter bank, the filters must satisfy perfect reconstruction conditions. This paper presents a theorem that formulates perfect reconstruction conditions for two-channel filter bank and a complete proof of both necessary and sufficient conditions. Additional requirements for filters guaranteeing the existence of the wavelets are reviewed.

Localized linear operators: application to image sequence compression using optical signal processing

Abstract: This paper discusses about the extension of Gabor Expansions to the optical domain and the design of an efficient filter bank to provide adaptive equalization in the light of Optical Signal Processing. The isomorphism between this localized linear operator and the filter design fundamentals are examined in the framework of image sequence compression. A new and efficient technique to perform Gabor expansion of Optical signals is introduced. The multi-resolution representation of data is considered in particular. A new approach to filter bank design in optical domain, using matrix formulation is introduced. Using this approach, an efficient optical filter bank with low complexity and good frequency response is designed. It is interesting to note that this design is a mathematical model of the quincunx filter bank. The characteristics of this optical filter bank are compared with that of other commonly used short kernel filter banks, for video compression applications. The approach is based on multi-resolution representation of data, which is generated by the filter bank proposed in this work. The use of multi-resolution data structure in conjunction with other components of the system allows a simple and efficient implementation. Simulations on typical image sequences show that it is possible to perform generic coding with reduced complexity and good efficiency.

A novel method for designing adaptive compaction orthogonal wavelet filter banks

Abstract: Recently, there has been a growing interest in investigating signal-adaptive multirate filter banks. In this paper, we propose a direct method of constructing signal-adaptive orthogonal wavelet filter banks with better energy compaction performance than that of Daubechies wavelet filters of same length. The speed of this method is fast, so it can be constructed in real time.

Direction angle estimation of moving targets by applying MUSIC to the outputs of quadrature mirror Doppler filter bank

Abstract: In radar signal processing, it is important to separate multiple targets that are covered in same radar antenna beam and in same range bin. It is also important to measure the position of each target. This paper proposes a new angular measurement system by applying MUSIC (multiple signal classification) to the outputs of Doppler filter bank consisting quadrature mirror filters. Some numerical experiments show that the proposed method can estimate the angles of moving targets at high speed, even for coherent targets and under low signal-to-noise ratios.

SDP for multi-criterion QMF bank design

Abstract: The quadrature mirror filter (QMF) bank, with multi-criterion constraints such as minimal aliasing and/or minimal error coding, is among the most important problems in filter bank design, for solving which linear algebra-based methods are still heuristic and do not always work, especially for large filter length. It is shown in this paper that when filters are of nonlinear phase, this problem can be reduced to convex linear matrix inequality (LMI) optimization, which can be very efficiently solved either by the standard LMI solvers or our previously developed solver. The proposed computationally tractable optimization formulations are confirmed by several simulations.

On the lifting construction of a class of non-separable 2D orthonormal wavelets

Abstract: In most cases 2D (or bivariate) wavelets are constructed as a tensor product of 1D wavelets. Such wavelets are called separable. However, there are various applications, e.g. in image processing, for which non-separable 2D wavelets are preferable. In this paper, we are concerned with the class of compactly supported 2D wavelets that was introduced by Belogay and Wang (1999). A characteristic feature of this class of wavelets is that the support of the corresponding filter comprises only two rows. As a result, the 2D wavelets in this class are intimately related to some underlying 1D wavelet. We explore this relation in detail, and we explain how the 2D decompositions can be realized by a lifting scheme, and hence allow an efficient implementation. We also describe an easy way to construct wavelets with more rows and shorter columns.

Optimized filter banks for the compression of subtraction angiographic images

Abstract: Several classes of images contain a clearly determined set of basic signals. This permits the development of signal-matched filter banks for image compression. A new approach for the derivation of signal-optimized filter banks using nonlinear optimization is presented here. Filters optimized with respect to the vessel and background signal of angiographic images are provided as a design example. Experimental results show that the new filter bank is competitive with the best biorthogonal wavelets.

Permutation of conjugate quadrature filter

Abstract: After some permutating of a conjugate quadrature filter (CQF), new CQFs can be derived In this paper, we give a method to construct bivariate orthogonal wavelets by permutating of separable two-dimensional CQF Non-separable bivariate orthogonal wavelets can be obtained by this method Finally, an example is provided to demonstrate this method

Phase error compensation method for reception and/or transmission system with in-phase and quadrature signal paths

Abstract: The phase error compensation method uses a phase corrector (PC) inserted in the digital signal processing stage (10') for the in-phase and quadrature signal paths, for calculation of phase-corrected in-phase and quadrature signal components using matrix operations. An Independent claim for a reception and/or transmission system with in-phase and quadrature signal paths is also included.