Showing papers on "Quadrature mirror filter published in 2002"

An efficient and simple method for designing prototype filters for cosine-modulated pseudo-QMF banks

Abstract: We present a new method to design prototype filters for conventional cosine-modulated pseudo-quadrature mirror filter (QMF) banks. This method is based on windowing, and sets the 3-dB cutoff frequency of the filter obtained at /spl pi//2M. In this way, the filter bank performance can be significantly improved compared to other existing design methods.

Active quadrature signal generator using load having low-pass and high-pass filter characteristics

Abstract: An active quadrature signal generator produces poly-phase quadrature signals necessary in high frequency transmit and receive elements of a communication system. The quadrature signals are produced using the phase difference between a load representing a low-pass filter characteristic and a load representing a high-pass filter characteristic and the quadrature signal is then used in the differential structure to produce amplified signal having 4 quadrature phases. The device can reduce a loss characteristic of the signal and additional power consumption for compensating for it in a common poly-phase quadrature filter having only conventional resistors and capacitor.

A Novel Genetic Algorithm for the Design of a Signed Power-of-Two Coefficient Quadrature Mirror Filter Lattice Filter Bank

Abstract: A novel genetic algorithm (GA) for the design of a canonical signed power-of-two (SPT) coefficient lattice structure quadrature mirror filter bank is presented in this paper. Genetic operations may render the SPT representation of a value noncanonical. In this paper, a new encoding scheme is introduced to encode the SPT values. In this new scheme, the canonical property of the SPT values is preserved under genetic operations. Additionally, two new features that drastically improve the performance of our GA are introduced. (1) An additional level of natural selection is introduced to simulate the effect of natural selection when sperm cells compete to fertilize an ovule; this dramatically improves the offspring survival rate. A conventional GA is analogous to intracytoplasmic sperm injection and has an extremely low offspring survival rate, resulting in very slow convergence. (2) The probability of mutation for each codon of a chromosome is weighted by the reciprocal of its effect. Because of these new features, the performance of our new GA outperforms conventional GAs.

Image Features Based on a New Approach to 2D Rotation Invariant Quadrature Filters

Abstract: Quadrature filters are a well known method of low-level computer vision for estimating certain properties of the signal, as there are local amplitude and local phase. However, 2D quadrature filters suffer from being not rotation invariant. Furthermore, they do not allow to detect truly 2D features as corners and junctions unless they are combined to form the structure tensor. The present paper deals with a new 2D generalization of quadrature filters which is rotation invariant and allows to analyze intrinsically 2D signals. Hence, the new approach can be considered as the union of properties of quadrature filters and of the structure tensor. The proposed method first estimates the local orientation of the signal which is then used for steering some basis filter responses. Certain linear combination of these filter responses are derived which allow to estimate the local isotropy and two perpendicular phases of the signal. The phase model is based on the assumption of an angular band-limitation in the signal. As an application, a simple and efficient point-of-interest operator is presented and it is compared to the Plessey detector.

An octave-band family of non-redundant directional filter banks

Abstract: This paper introduces an octave-band family of directional filter banks for images, capable of dividing the spatial frequency spectrum both angularly and radially using an efficient structure. The new directional filter bank employs efficient separable analysis and synthesis filters with perfect reconstruction. Unique to the octave-band directional filter bank family are the properties of joint radial frequency selectivity and pyramid oriented frequency selectivity, all within a maximally decimated structure.

Strain contouring with Gabor filters: filter bank design

Abstract: A novel fringe processing method is proposed to segment whole-field strain distributions from interferometric deformation patterns by use of Gabor filters. This novel strategy is specifically proposed for strain measurement with a Gabor filter used as a set of wavelets. To increase computational speed as well as for selection of contour intervals, judicious design of the filter bank, based on the fringe pattern and the requirements of the user, is crucial in this methodology. A filter design strategy is developed and, based on the proposed filter design scheme, properly designed filter banks are generated and applied for strain contouring in low-strain and strain concentration regions. This scheme allows one to measure engineering strains within regions of interest and hence provides the design engineer great flexibility of monitoring, testing, or analysis.

Method and apparatus for transmitting wideband speech signals

Abstract: A method and an apparatus for transmitting a speech signal are provided. A speech signal transmitter includes a quadrature mirror filter, a base sub-band encoder, an enhancement sub-band encoder, and a network connector. The quadrature mirror filter receives a speech signal, divides the speech signal into an enhancement band speech signal and a base band speech signal, and outputs the enhancement band speech signal and the base band speech signal. The base sub-band encoder receives and encodes the base band speech signal. The enhancement sub-band encoder receives and encodes the enhancement band speech signal. The network connector multiplexes the encoded enhancement band speech signal and the encoded base band speech signal based on the kinds of networks over which speech signals are transmitted, and transmits the multiplexed signals to the networks. A speech signal is multiplexed and transmitted by various methods based on the kinds of networks. Thus, the speech signal can be efficiently transmitted.

A novel translation and modulation invariant discrete-discrete uncertainty measure

Abstract: The quantification of signal localization simultaneously in time and in frequency is fundamental to a variety of signal processing applications where time-frequency analysis is to be performed on nonstationary signals. In this paper, we develop novel joint localization measures defined on equivalence classes of finitely supported discrete-time signals. These measures bear strong analogies to the well-known continuous-time Heisenberg-Weyl inequality. In particular, they are invariant to signal translations and modulations and admit an intuitive interpretation in terms of the temporal and spectral variance of the signal energy. The new measures are used to design optimal wavelet quadrature mirror filter banks that exhibit improved localization relative to the Haar and Daubechies analysis filters.

Detection and analysis of FMCW and P-4 polyphase LPI waveforms using quadrature mirror filter trees

Abstract: This paper investigates the performance of a quadrature mirror filter (QMF) in detecting two low-probability of intercept (LPI) emitter waveforms: a triangular Frequency Modulation Continuous Wave (FMCW) waveform and a P-4 polyphase code CW waveform. Detection performance for signal-to-noise ratios (SNRs) of +10 dB, 0 dB, −10 dB, and −20 dB is examined. Signal features that can be extracted are also quantified. Results indicate that QMF processing can provide good detection of LPI waveforms even in the presence of a moderate amount of noise.

Receiver with mirror frequency suppression

Abstract: Receiver comprising an RF front end circuit for a selection and conversion of an RF input signal into a pair of quadrature IF (intermediate frequency) signals being supplied through in-phase and phase quadrature signal paths to signal inputs of quadrature phase detection elements, such as in-phase and phase quadrature phase detectors included in a (PLL) phase locked loop, an output of the quadrature phase detection elements being coupled through a loop filter to a control input of a quadrature IF oscillator supplying a pair of quadrature IF oscillator signals to carrier inputs of the quadrature phase detection elements. To suppress amplitude and phase mismatch deteriorating proper mirror cancellation the quadrature phase detection elements is coupled to amplitude and phase error signal for a detection of amplitude and phase errors in the output signal of the quadrature phase detection elements and a quadrature frequency doubler is coupled between the quadrature local oscillator and carrier inputs of the amplitude and phase error detection means to supply respectively thereto in-phase and phase quadrature error detection carrier signals at twice the IF carrier frequency of the pair of quadrature IF signals, the amplitude and phase error detection means respectively providing amplitude and phase error signals through first and second low-pass filters to an amplitude correction circuit and a phase correction circuit preceding at least one of the inputs of the quadrature phase detection elements for a negative feedback of the amplitude and phase errors.

Adjusting the trans-conductance of a filter

Abstract: A digital tuning circuit which generates a digital code representative of a difference of signals generated by a mirror trans-conductor circuit (having electrical characteristics similar to a trans-conductor circuit in a filter) and a reference circuit. The digital code is used to adjust the trans-conductance of both the mirror trans-conductor circuit and the filter. Some of the most/more significant bits may be used to selectively activate the respective trans-conductor elements contained in the mirror trans-conductor circuit and the filter. The remaining bits may be used to fine-tune the trans-conductance of the trans-conductor elements and the filter.

Multirate filter bank reconstruction of bandlimited signals from bunched samples

Abstract: A method for reconstructing a bandlimited signal from its periodic bunched samples is presented As in prior approaches, a multirate filter bank structure is used to reconstruct the signal; however, the technique used to design the reconstruction filter bank is different The solution presented employs an interpolation filter to model the signal at the input of the reconstruction filter band FIR synthesis filters are selected to reduce aliasing and distortions of the reconstructed signal Simulation results showing the quality of reconstruction are presented

Polyphase Filter Approach for High Performance, FPGA-Based Quadrature Demodulation

Abstract: The polyphase filter approach to quadrature demodulation is shown to be well suited for the implementation of purpose-designed wide bandwidth digital quadrature demodulators. The duplicated polyphase filter approach is introduced, as a way to increase the maximum allowable input signal bandwidth for a given implementation technology. Other algorithmic and architectural considerations specifically applicable to the realization of digital filters in low-cost Field-Programmable Gate Array (FPGA) technology are discussed. A design example suitable for processing input signals centered on an intermediate frequency of 160 MHz with a bandwidth of ∼45 MHz is presented. This design occupies 83% of the Configurable Logic Blocks (CLBs) in a low-cost Xilinx X4010E-3 FPGA. Additional techniques for further performance optimization are presented.

Theory and lattice factorization of oversampled linear-phase perfect reconstruction filter banks

Abstract: This paper presents the theory and structure of a large family of oversampled linear-phase perfect reconstruction filter banks (OLPPRFBs). For such filter banks, we first derive the necessary existence conditions on the number of symmetric filters and antisymmetric filters. We then develop lattice factorizations of these OLPPRFBs, followed by two design examples to confirm the validity of the theory.

Transient model of power transformer using wavelet filter bank

Abstract: This paper presents a model of the power transformer for electromagnetic transient studies, which employs a wavelet filter bank. In this model both the primary and the secondary windings are represented by stages of a wavelet filter bank where the dimensions of such a filter bank depend on the number of turns of primary windings and secondary windings. The basic building block consists of stages of the wavelet filter bank. Transformer total response is composed of the sum of responses of all stages, which depends on the nature of the primary current. Using the wavelet filter model, the losses due to eddy currents, leakage flux, and inrush currents have been studied. The proposed wavelet filter model has been found to be suitable for power transformer inrush currents including high frequency transient effects.

Multi-level face image recognition method and system

Abstract: The present invention applies the quadrature mirror filter and uses the multi-resolution decomposition method to decompose an image into at least two sub-images with different resolutions. The decomposed sub-images are applied to a self-organizing map neural fuzzy network for performing a classification learning without monitoring. The test stage is started from the lowest resolution. The possible person is given to a higher level resolution to be recognized if it can not be recognized due to low resolution.

A data hiding for audio using band division based on QMF bank

Abstract: In the watermarking techniques for audio are required quality, security and robustness. This paper presents method that improves security and robustness, besides restricting the noise. Special attention is given to band-division by using a filter bank based on the Quadrature Mirror Filter (QMF) that several audio compression standards adopt. First, we divide the time-domain data into several subbands and select the sub band to embed the watermarking. Then, we spread the signal included in the selected sub band using Direct Spectrum Spreading (DSS), one of the spectrum spreading methods, and embed the watermarking in the frequency-domain data. Finally, we reconstruct the signal by synthesizing whole subbands. By this method, we can reduce the noise and improve security and robustness against MPEG1 Audio Layer3 compression. Experimental results show good robustness of the approach against some signal processing manipulations. Quality and robustness are evaluated by computer simulation.

Discrete wavelets and filtering chaotic signals

Abstract: We study the behavior of one-dimensional chaotic signals and filtering using the discrete Haar wavelet and Daubechies wavelets.

Discrete Wavelet Encoder using Quadrature Mirror Filter

Abstract: PURPOSE: A discrete wavelet encoder using a quadrature mirror filter is provided to perform compression of images, which requires fast processing, with a small amount of calculations in real time. CONSTITUTION: A discrete wavelet encoder using a quadrature mirror filter includes an input controller(301), a vertical filter bank(307), a line memory(304), and a horizontal filter bank(308). The input controller down-samples an input signal into column and row components and outputs the components simultaneously. The vertical filter bank filters the column component signals and divides the signals into low-frequency and high-frequency signals. The line memory outputs the row component signals, output from the vertical filter bank, in parallel, and stores the filtered signals. The horizontal filter bank filters the row component signals and outputs the signals as signals having different frequency bands.

Direct conversion wireless receiver with digital phase equalization

Abstract: A direct conversion receiver (DCR) with a pair of quadrature conversion paths. Each of the quadrature conversion paths receives an RF input signal and converts the RF input signal to a digital baseband signal. The quadrature conversion paths each include a mixer mixes the RF input signal with a carrier phase signal. Quadrature baseband signals from the mixer pass through an analog filter which provides a filtered baseband signal. An analog to digital converter (ADC) converts the quadrature baseband component to a digital baseband signal. A 5 th order elliptical filter filters the quadrature baseband component. The 5 th order elliptical filter may be before or after the ADC. A digital baseband component from the ADC and filtered by the 5 th order elliptical filter passes to a phase equalizer which compensates for phase distortion from the analog filter. The quadrature digital baseband outputs from the quadrature conversion paths are passed to a baseband processor.

On two-channel orthogonal and symmetric complex-valued FIR filter banks and their corresponding wavelets

Abstract: Two-channel orthogonal and symmetric complex-valued FIR filter banks and their corresponding wavelets are investigated. First, the conditions for the filter bank to be orthogonal, symmetric and regular are presented. Then, a complete and minimal lattice structure is developed, which enables a general design approach for filter banks and wavelets with arbitrary length and arbitrary order of regularity. Finally, two integer implementation methods that preserve the perfect reconstruction property are proposed. Their performances are evaluated via experimental results.

Signal-adapted binary tree-structured paraunitary filter bank design

Abstract: Signal adapted filter bank design that uses energy compaction as the adaptation criterion has been applied in the past to quadrature mirror filter (QMF) banks, as well as to M-channel FIR paraunitary filter banks. This analysis was extended to tree-structured filter banks having signal adapted, FIR QMF banks at each level. It showed that fewer parameter allocations to represent filter coefficients are required for tree structured filter banks with similar energy compaction performance, compared to an equivalent structure filter bank with M channels.

Quadrature demodulator using compensation of phase and amplitude imbalances

Abstract: Device for down-transforming the frequency of signals, for example le radio and/or television signals. The device comprises a transformer unit with quadrature channels for transforming the signals into quadrature signals of a lower frequency. The device further comprises a filter unit for suppressing mirror frequencies. The filter unit comprises an amplitude and phase correction filter for correcting the quadrature signals and a correction control unit for controlling the filter. The device further comprises a frequency generator which supplies reference signals having a frequency within the frequency band of the mirror signals to the input of the transformer unit.

Design of 2D filter banks based on 1D lattice structure

Abstract: This paper proposes a design procedure for the 2D linear-phase para-unitary filter bank, based on the 1D lattice structure. As the first step, the perfect reconstruction conditions of 1D and 2D cases are compared, and it is shown that the 2D filter bank satisfying the perfect reconstruction condition can be realized by the 1D lattice structure with a constraint. It is known, on the other hand, that the 1D perfect reconstruction filter bank can be converted to the lattice structure, using only half of the filter coefficients, and a simple optimization procedure can derive the whole filter coefficients. Based on those investigations, it is shown that the 2D filter bank can be designed by directly designing only half of the channels of the 2D filter bank in the time domain. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 85(12): 38–46, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.10005

A comparative survey for an adaptive FIR filter design in image compression by wavelets decomposition

Abstract: In this paper, adaptive filtering, wavelets, and lossy image compression are considered. Performances of the subband adaptive digital filter are discussed. We propose a transform coding method in which the low pass filters in the wavelets decomposition tree are time-varying. The idea is to decompose a digital image using an adaptive FIR 1 filter in each low frequency subband and compare it with an invariant filter of Daubechies. We employ a framework that includes the main comparison parameters. It is clearly shown here that it provides better performances than invariant filters in most applications. This work consists of applying an adaptive FIR 1 filter by the ADFFLS 2 algorithm to digital images. The filter performances on the different stages of the data image compression chain are then valued and compared with an invariant and biorthogonal filter of Daubechies. This is done studying of the main parameters, namely the covariance matrix, the subband coding gain, the concentration of energy in the low frequency subband, the signal to noise ratio, the correlation, the bit allocation, and the compression ratio. This study resides in the meticulous choice of comparison parameters, and the different stages of comparison. Results show that the PSNR 3 , the correlation between original and reconstructed images, and the compression ratio are better with the adaptive filter for different lengths, quantifiers, and quantification levels.

A class of multi-valued signature sequences for DS/CDMA systems

Abstract: In this paper, we propose a class of multi-valued signature sequences for direct sequence code division multiple access (DS/CDMA) systems. We obtain the signature sequences by modifying the coefficients of the subbands of a perfect reconstruction quadrature mirror filter (PR-QMF) bank. The class has perfect correlation properties for synchronous DS/CDMA systems, and in general has better correlation properties than other well-known sequences in asynchronous DS/CDMA systems also. Some numerical results for the performance of the asynchronous DS/CDMA systems with several sequences including the proposed class of sequences are obtained.

Comparison of the modified least squares and the weighted least squares algorithms for designing quadrature mirror filters

Abstract: The least squares (LS) and the weighted least squares (WLS) algorithms are well known procedures that are used in the design of quadrature mirror filters (QMF). The equiripple nature of the WLS and its performance near the filter band edge has been reported to be better than that of the former. It is known that these design techniques suffer from a pass-band anomaly under certain conditions. Recently, it has been shown that the design anomaly in the LS algorithm can be overcome by using an initial guess filter obtained by a frequency sampling design (see Premkumar, A.B. and Vinod, A.P., IEEE Sig. Proc. Letters, vol.7, no.8, p.224-7, 2000). The same technique can be extended to overcome the pass-band anomaly in WLS filters. We present a comparison of modified LS and WLS designs based on simulation results. It is shown that the LS design is more robust, computationally less intensive and offers optimal performance over a wide range of cut-off frequencies.