Showing papers on "Quadrature mirror filter published in 2010"

Two-Channel Linear Phase FIR QMF Bank Minimax Design via Global Nonconvex Optimization Programming

Abstract: In this correspondence, a two-channel linear phase finite-impulse-response (FIR) quadrature mirror filter (QMF) bank minimax design problem is formulated as a nonconvex optimization problem so that a weighted sum of the maximum amplitude distortion of the filter bank, the maximum passband ripple magnitude and the maximum stopband ripple magnitude of the prototype filter is minimized subject to specifications on these performances. A modified filled function method is proposed for finding the global minimum of the nonconvex optimization problem. Computer numerical simulations show that our proposed design method is efficient and effective.

An Improved Method for Designing Quadrature Mirror Filter Banks via Unconstrained Optimization

Abstract: This paper proposes an algorithm to design a two-channel linear phase quadrature mirror filter (QMF) bank. The design problem is presented systematically as an unconstrained optimization that minimizes the weighted sum of error of transfer function of the filter bank at quadrature frequency, stopband energy and the passband error of a prototype filter (PF). A new method is developed for the design of a low pass prototype filter for QMF banks. For solving given optimization problem, Quasi-Newton optimization technique is used. Numerical examples and comparisons with several existing methods are included to show the performances and effectiveness of this method. An application of the proposed method is considered in the area of subband coding of the images.

High input impedance voltage-mode universal filter and quadrature oscillator

Abstract: A new single input and five outputs high input impedance voltage-mode universal biquadratic filter using three DVCCs, five passive components is presented The proposed circuit offers the following

Digital chromatic dispersion compensation in coherent transmission system using a time-domain filter

Abstract: We demonstrate the chromatic dispersion equalization employing a time-domain filter in a 112-Gbit/s polarization division multiplexed quadrature phase shift keying coherent system. The required tap number of the filter is analyzed from anti-aliasing and pulse broadening. The dynamic range of the filter is evaluated by using different number of taps.

Two-Channel Parallelogram QMF Banks Using 2-D NSHP Digital All-Pass Filters

Abstract: This paper presents a novel structure for the analysis and synthesis filters of two-channel parallelogram quadrature mirror filter (PQMF) banks. Two-dimensional recursive digital all-pass filters (DAFs) with nonsymmetric half-plane (NSHP) support regions are used as the basic sections for building this structure. With an appropriate combination of the 2-D NSHP DAFs, the resultant analysis/synthesis filters possess a 2-D doubly complementary symmetry that facilitates the design and implementation of two-channel PQMF banks. Moreover, the proposed PQMF bank provides approximately linear-phase response without magnitude distortion. The design problem of the proposed PQMF bank is appropriately formulated to result in a minimization of the linear-phase error associated with the 2-D NSHP DAFs in the pth-norm (Lp) sense. Efficient design techniques are developed to solve the Lp optimization problems. Simulation results for illustration and comparison are also provided.

A New Approach to the Common-Factor Design Technique for Hilbert-Pair of Wavelets

Abstract: A Hilbert-Pair consists of a pair of filter banks whose corresponding wavelets are Hilbert transforms of each other. Selesnick proposed the simple common-factor technique for its design. The filter transfer functions consist of the product of a factor that is common to both filter banks and a phase factor which gives the (approximate) half-sample-delay requirement. Previously the design of the phase factor has been based on designing an allpass filter approximating the half-sample-delay. This paper proposes a different approach to designing the phase factor by exploiting a basic multirate identity. The downsampling approach allows greater flexibility and can yield filters and wavelets with better properties.

An algorithm for spectrum sensing in cognitive radio using tree-structured filter bank

Abstract: One of the key requirements in cognitive radio is accurate detection of vacant spectrum bands. In this paper, an energy detector based on a tree-structured quadrature mirror filter bank (TQMFB) is proposed for detecting the center frequencies of the channels (frequency bands). Simulation results are presented to show the trade off between the window size, k, and the error in estimating the center frequency of a specific channel. It is shown that, as the value of FFT size increases, the error in estimation decreases for smaller window sizes and does not change significantly for larger windows. The proposed method is compared with discrete wavelet packet transform (DWPT) based energy detector for complexity and performance. Design examples and simulation show that the proposed method estimates the center frequency of the channels with high accuracies for a specific spectral scenario and signal to noise ratio (SNR).

Analysis and Properties of Time-Varying Modified DFT Filter Banks

Abstract: We provide a comprehensive analysis of the time-varying modified DFT (MDFT) filter bank based on the general time-varying filter bank theories (Wang, 2005, 2006, 2008, 2009) in both the time domain and frequency domain. We give firstly the description of the time-invariant MDFT filter bank including its perfect reconstruction (PR) condition, its mechanism of aliasing error cancellation and the relationship with the cosine-modulated filter bank in detail. Then, the time-varying MDFT filter bank is analyzed according to the time-domain description. Finally, the window switching method is introduced to design the prototype filter in the time-varying MDFT filter bank with examples. The error analysis shows that the introduced design approach is useful in practice.

Two-channel quadrature mirror bank filter design using a Fitness- Adaptive Differential Evolution algorithm

Abstract: In this article, a modification of Differential Evolution (DE), Fitness-Adaptive Differential Evolution (FiADE) is used to design the quadrature mirror filter (QMF) banks with linear phase in frequency domain. The three main attributes used in assessing the performance of filter are reconstruction error, mean square error in pass band and mean square error in stop band. The proposed method produces better result than the result obtained by Particle Swarm Optimization (PSO). As compared to the existing methods this method is very simple to implement for the QMF bank optimization. To implement the proposed DE algorithm, a MATLAB program is developed and three examples have been presented to illustrate the performance of the proposed method.

Two-frame algorithm to design quadrature filters in phase shifting interferometry

Abstract: The main purpose of this paper is to present a method to design tunable quadrature filters in phase shifting interferometry. From a general tunable two-frame algorithm introduced, a set of individual filters corresponding to each quadrature conditions of the filter is obtained. Then, through a convolution algorithm of this set of filters the desired symmetric quadrature filter is recovered. Finally, the method is applied to obtain several tunable filters, like four and five-frame algorithms.

Towards optimal implementation of a class of quadrature mirror filter using genetic algorithms

Abstract: This paper considers theoretical issues regarding reconstruction errors and conditions for perfect reconstruction (PR) of the input signal for a 2-channel multirate quadrature mirror filter (QMF) bank. The main emphasis is on the application of genetic algorithms in the optimisation process of a new design technique for a perfect reconstruction QMF bank using infinite impulse response (IIR) filters. This design is based on using a transformation of variables technique. The genetic algorithm (GA) optimisation is used for the initial design of the QMF bank and for the IIR filters using finite word length (FWL) coefficients. The optimised results are then explored to be applied towards a real time digital signal processing implementation.

Wireless apparatus and signal processing method

Abstract: A wireless apparatus includes: an A/D converter which samples an in-phase signal component and a quadrature signal component from a quadrature-modulated signal of analog form alternately; a digital quadrature demodulation unit which applies digital quadrature demodulation to an output signal of the A/D converter and outputs an in-phase signal and a quadrature signal; and an error detection unit which, based on the in-phase and quadrature signals output from the digital quadrature demodulation unit, detects a time difference error between the sample timing of the in-phase signal component and the sample timing of the quadrature signal component.

I/Q imbalance effects in quadrature ΣΔ modulators — Analysis and signal processing

Abstract: This article focuses on the in-phase/quadrature (I/Q) imbalance problem in quadrature ΣΔ modulators (QΣΔM). In the literature, such quadrature modulators have been seen as a promising possibility for software defined radio (SDR) receivers, but matching the quadrature circuits is an inevitable problem for this kind of systems. In this article, an analytic closed-form model will be derived for a mismatched first order QΣΔM by means of the modulator transfer functions and the underlying implementation components. In addition, notching the signal transfer function (STF) on the desired signal mirror frequency inside the modulator is proposed for cancelling the mirror frequency interference originating from the blocking signal on that band. This is shown to be effective in case of the modulator feedback branch mismatches and can be implemented with simple additional feedforward coefficient(s) compared to ordinary modulator.

QMF implementation using Xilinx SysGen (XSG)

Abstract: The Quadrature Mirror Filter (QMF) basically is a parallel combiation of of a High Pass Filter (HPF) and Low Pass Filter (LPF), which performs the action of frequency subdivision by splitting the signal spectrum into two spectra. Thus QMF finds wide applications in many signal processing tasks such as transmultiplexing1, equalizing wireless communication channels; sub-band coding of speech and image signals, sub-band acoustic echo cancellation etc[1,2]. Hence this paper is devoted to the effective utilization of XSG for hardware implementation of QMF. This assists the Xilinx IP Core generator to deliver the optimized results for the implemented device within short duration of time. The results obtained in the simulation of QMF using XSG and the communication system built using QMF at transmitter and receiver side indicate that the nearly ‘Perfect Reconstruction’ is possible without any effect of aliasing. The obtained Synthesis Report for implemented QMF indicates that the utilization of sililcon die area and power dissipation, for Spartan 3E device, are sufficiently low. Also the comparison between the results of XSG and Simulink depicts that it is efficient to built QMF using XSG. The study reveals that QMF-DPCM provides much better approach towards the communication system. DPCM using QMF is introduced to pave the way for smooth transition from conventional 4 kHz band telephone systems to 7 kHz wide-band systems[3].

A Unified Framework to Design Orthonormal Wavelets Packet Bases for Multi-Carrier Modulation

Abstract: Wavelet Packet Modulation (WPM) is a novel multicarrier communication technique where information carrying symbols are placed on orthogonal wavelet packet bases. The WPM system is realized by a tree structure obtained by cascading a pair of half-band Quadrature Mirror Filter (QMF) duo. By altering the properties of these filters the transmission characteristics of the WPM system can be customized to a given design specification. In this article we present a general, unified approach to design and develop orthogonal wavelet packet bases according to a requirement. To this end, the design criterion and the wavelet constraints are first listed. The problem which is originally non-linear and non-convex in nature is then converted into a tractable convex optimization problem and finally solved using suitable Semi Definite Programming (SDP) tools. The proposed mechanism is demonstrated through two toy examples where families of wavelets which are i) maximally frequency selective and ii) have the lowest cross correlation energy, respectively, are developed.

The analysis and design of two-dimensional nearly-orthogonal symmetric wavelet filter

Abstract: The analysis and design of two-dimensional nearly-orthogonal symmetric wavelet filter has been studied. Methods for analyzing the correlation of the nearly-orthogonal filter banks are proposed. The basic idea is to impose multiple zeros at the aliasing frequency to a symmetric filter, minimize the deviation of the filter satisfying the orthogonal condition, then a nearly orthogonal filter bank can be obtained. The way in this paper is to find a FIR complementary filter of the minimized filter and thus construct a perfect reconstructed biorthogonal filter bank. Then a corresponding wavelet filter bank can be generated and correlation analysis can also be conducted.

Quadrature signal decoding using a driver

Abstract: A system and method for decoding quadrature signals includes a quadrature signal generator, a quadrature signal decoder, a key matrix and a driver The quadrature signal generator generates quadrature signals on rotation The quadrature signal decoder is configured to convert the quadrature signals into non-overlapping signals The key matrix is configured to receive the non-overlapping signals The driver is configured to scan the key matrix to decode the non-overlapping signals to generate an event update corresponding to a direction of rotation of the quadrature signal generator

Multi-channel loudness compensation method for digital hearing aids based on DSP

Abstract: Loudness compensation is a key function of hearing aids. A new four-channel loudness compensation method was proposed based on human auditory,especially on presbycusis. The filter-band designed for sub-band loudness compensation was given by using quadrature mirror filter bank( QMFB). The signal at senile hearing loss was simulated using a low-pass filter. A TMS320C5402 chip was utilized to realize loudness compensation in high bands. Results of simulation by Matlab and experiments on DSP show that,energy loss in high bands of hearing loss patients is well compensated.

Sound signal processing apparatus, sound encoding apparatus and sound decoding apparatus

Abstract: Provided is a sound signal processing apparatus capable of performing a sound signal processing, such as time scaling or frequency modulation, with only a small calculation amount. A sound signal processing apparatus for converting an input sound signal sequence by use of a predetermined adjustment factor comprises: a filter bank (2601) that is operative to convert an input sound signal sequence to a QMF (Quadrature Mirror Filter) factor sequence by use of a QMF analysis filter; and an adjusting unit (2602) for adjusting the QMF factor sequence by causing the QMF factor sequence to be dependent on the predetermined adjustment factor.

Enhanced Wideband Adaptive Arrays with Different Length Quadrature Mirror Filter Banks

Abstract: The performance of a sub-band adaptive beamforming array (ABA) using different length quadrature mirror filter banks (QMF) for wideband signals is investigated. Delay taps have to be introduced to the full band ABA for wideband signals' operation for deep suppression of the interference. The addition of more taps may result in an increase of uncorrelated noise to the ABA operation. Hence an undesirable power loss at the direction perpendicular to the ABA may occur. The problem of the loss introduced by the additional taps is overcome by introducing a QMF based sub-banding concept. In this paper, different kernels QMF banks are used for the evaluation and hence the comparison of the beamforming application. The beamforming performance of the ABA using the short kernel QMF (eighth order) sub-band ABA is compared with that using a long kernel QMF (sixteenth order). The sub-band ABA with long kernel QMF shows improved signal gain and deep suppression of interference (similar to the short kernel QMF) in the direction perpendicular to the ABA, compared to the full band ABA.

Filter bank synthesis for adapted wavelet analysis

Abstract: The multiresolution theory of orthogonal wavelets proves that any conjugate mirror filter characterizes a wavelet that generates an orthonormal basis of L 2 R. This paper presents a method to obtain a discrete wavelet function, through FIR filter synthesis starting from a random discrete sequence. This sequence is used as a FIR filter which generates the four conjugate mirror filters necessary to implement the Discrete Wavelet Transform. The refinement of this sequence is carried out by a learning structure which follows to minimize the error between the signal and its reconstructed form from first order decomposition.

Parameters Extraction of Pseudo-Code PM Combined with SFM Signal Based on QMFBT Techniques

Abstract: To extract feature parameters of Pseudo-code binary phase modulation combined with sine frequency modulation continuous wave(PRBC-SFMCW), the linear decomposition techniques using Quadrature Mirror Filter Bank Tree (QMFBT) is adopted. With this method, the intercepted signal is decomposed and analyzed by QMFBT. Then according to the feature of PRBC-SFMCW signal contained in different time-frequency layers the algorithm of feature parameter extraction on an appropriate time-frequency layer is presented. The analysis and simulation results show that the SNR of PRBC-SFMCW signal is improved after decomposition. At the same time, the across section disappear and parameters can be estimated accurately in a low SNR condition.

A simple method for designing quadrature mirror filter banks via quadratic constrained optimisation

Abstract: This paper proposes a simple algorithm for the design of a two-channel linear phase quadrature mirror filter (QMF) bank. The design problem is formulated as a quadratic constrained least square minimisation that optimises the performance of a prototype filter (PF) and distortion transfer function of filter bank at quadrature frequency. A new method is developed for the design of a low pass prototype filter for QMF banks. For solving the given optimisation problem, a sequential quadratic programming (SQP) technique is used. Numerical examples and comparisons with several existing methods are included to show the performances and the effectiveness of the proposed method. An application of this method is considered in the area of subband coding of the images.