Showing papers on "Quadrature mirror filter published in 2009"

Quadrature signal generation in radio-frequency apparatus and associated methods

Abstract: A radio-frequency (RF) apparatus, which may reside in a receiver or transceiver, includes receive-path circuitry. The receive-path circuitry includes a poly-phase filter and a harmonic filter. The poly-phase filter accepts an input signal and generates two output signals. One output signal of the poly-phase filter constitutes an in-phase (I) signal. The other output signal of the poly-phase filter constitutes a quadrature (Q) signal. The a harmonic filter couples to the poly-phase filter. The harmonic filter accepts as input signals the in-phase and quadrature output signals of the poly-phase filter.

Correction of quadrature errors

Abstract: A transmit chain comprises a correction network (1a) for correcting a frequency dependent quadrature error between in-phase and quadrature signal paths for the transmission of an input signal. The correction network has an in- phase input port, a quadrature input port, an in-phase output port and a quadrature output port and each input port is connected to each output port by a digital filter network, the digital filter network comprising a set of filter tap coefficients and configuration means for configuring values of said set of filter tap coefficients. Input signals are up-converted, and a portion of the up- converted signal is coupled to a quadrature downconverter (21). A controller (22) determines an error signal by comparing the down-converted signal with the input signal and modifies the set of values of filter tap coefficients on the basis of the error signal and the input signal to correct said frequency dependent quadrature error.

Design of Quadrature Mirror Filter Bank using Particle Swarm Optimization (PSO)

Abstract: In this paper, the particle swarm optimization technique is used for the design of a two channel quadrature mirror filter (QMF) bank. A new method is developed to optimize the prototype filter response in passband, stopband and overall filter bank response. The design problem is formulated as nonlinear unconstrained optimization of an objective function, which is weighted sum of square of error in passband, stop band and overall filter bank response at frequency (ω=0.5π ). For solving the given optimization problem, the particle swarm optimization (PSO) technique is used. As compared to the conventional design techniques, the proposed method gives better performance in terms of reconstruction error, mean square error in passband, stopband, and computational time. Various design examples are presented to illustrate the benefits provided by the proposed method.

Nyquist folding analog-to-information receiver: Autonomous information recovery using quadrature mirror filtering

Abstract: A broadband Nyquist-folding analog-to-information receiver, allows multiple Nyquist zones to be directly undersampled and subsequently folded into a continuous time analog interpolation filter. This paper presents a new algorithm that autonomously extracts the intercepted pulse parameters on the time-frequency plane using a quadrature mirror filter bank at the output of the interpolation filter. Parameters include a running calculation of the exact bandwidth, frequency, pulse duration and slope. By the examination of the signal's slope we show that a direct computation of the actual Nyquist zone is possible. Monte Carlo simulation runs are presented to demonstrate the robustness of the algorithm for −20≤SNR≤10 dB.

A novel approach to the design of oversampling complex-modulated digital filter banks

Abstract: This paper addresses the minimisation of the overall disturbances of the output signal of an oversampling DFT subband-coder filter bank. These disturbances are separated into aliasing and imaging. By means of the definitions of these disturbance components, two quadratic functions are derived that are used as objective functions in the design approach. The algorithm optimises in an iterative manner the coefficients of the prototype filters of the analysis and synthesis filter banks. It is proved that the design problem is convex. An efficient implementation of the algorithm is given. A numerical example shows that the output disturbances are highly reduced compared to standard designs.

A tree-structured non-uniform filter bank for multi-standard wireless receivers

Abstract: A new approach to implement computationally efficient reconfigurable filter banks for multi-standard wireless receivers is presented in this paper. Based on the concepts of tree-structured quadrature mirror filter bank (TQMFB) and coefficient decimation approach, a reconfigurable and efficient tree-structured non-uniform filter bank (TNFB) is proposed in this paper. The proposed filter bank is designed to extract channels of non-uniform bandwidths with reduced complexity when compared to TQMFB. Each stage of the proposed filter bank consists of a modal filter and a complementary delay to obtain the low-pass and high-pass channels respectively. Design examples show that the proposed TNFB offers an average multiplication rate reduction of 69% over the TQMFB.

The Analysis and Design of Nearly-Orthogonal Symmetric Wavelet Filter Banks

Abstract: The design and analysis of nearly-orthogonal symmetric wavelet filter banks 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, and a nearly orthogonal filter bank can be obtained. Since multiple zeros are imposed, a scaling function may be generated from the minimized filter. The integer translates of the wavelet and the scaling functions are nearly orthogonal. The integer translates of the wavelet at different scale are completely orthogonal. We will construct a perfect reconstructed semi-orthogonal filter bank. Detailed analysis of correlation of the nearlyorthogonal filter banks are given in this paper.

Two-Channel Quincunx QMF Banks Using Two-Dimensional Digital Allpass Filters

Abstract: This paper presents a novel structure for the analysis and synthesis filters of two-channel quincunx quadrature mirror filter (QQMF) banks. This structure uses an appropriate combination of 2-D recursive digital allpass filters (DAFs) with symmetric half-plane (SHP) support regions. The proposed analysis/synthesis filters possess a 2-D doubly complementary half-band (DC-HB) property that facilitates the design and implementation of the proposed two-channel QQMF banks. Moreover, the proposed structure provides approximately linear-phase response without magnitude distortion. The design problem of the proposed QQMF banks is appropriately formulated to result in a linear optimization problem that only minimizes the linear-phase error associated with the 2-D SHP DAFs in the p th-norm (Lp) sense. Efficient design techniques are developed to solve the Lp optimization problem for finding the coefficients of the 2-D recursive SHP DAFs. Finally, we provide simulation results for illustration and comparison.

On time-interleaved analog-to-digital converters for digital transceivers

Abstract: This paper presents a transceiver model that comprises two time-interleaved analog-to-digital (A/D) converter systems to sample the inphase and quadrature signals in a digital receiver Random data is used as the information signal and quadrature modulation is employed as the modulation scheme A polyphase filter bank is derived as a representation of the time-interleaved A/D converter system, thereby modelling its converter mismatch Furthermore, filter bank theory is used to design reconstruction filters that mitigate aliasing and distortion and achieve matched filtering in a single post-processing scheme, therefore reducing the digital implementation complexity of the receiver Simulations results are presented to illustrate the performance degradation due the usage of non-ideal A/D converters and to verify the propose reconstruction scheme Finally, an analysis of the required synthesis filter complexity is presented for different error magnitudes as a guideline for the filter bank design

A simple iterative technique for the design of cosine modulated pseudo QMF banks

Abstract: This paper presents a simple and efficient iterative technique for the design of cosine modulated pseudo quadrature mirror filter (QMF) banks. In the proposed algorithm, cutoff frequency is optimized to satisfy a new perfect reconstruction condition at frequency (ω = π/2M). Adjustable Window functions are used to design the prototype filter cosine modulated pseudo QMF banks. When compared to other existing techniques, the proposed algorithm significantly reduces amplitude distortion, number of iterations, aliasing distortion, and computation time. Several design examples are included to illustrate the proposed algorithm and its improved performances over other exiting methods.

An Improved Method for Designing Prototype Filter for M-Band Pseudo QMF Banks

Abstract: This paper presents an iterative algorithm for the design of multichannel cosine modulated pseudo quadrature mirror filter (QMF) banks. In this algorithm, passband frequency is optimized to satisfy new perfect reconstruction condition at frequency ( ). The proposed algorithm is simple, and has high design efficiency. The performance of this algorithm is evaluated in terms of computational time (CPU time), reconstruction error (RE), number of iterations (NOI), aliasing distortion (AD) and signal to noise ratio (SNR). Several design examples are included to illustrate the proposed algorithm and its improved performances over other exiting methods.

A novel quadrature demodulation based on shifted matched filter in SAR imaging processing

Abstract: There is an increasing performance demand in receiving system of synthetic aperture radar (SAR) in recent days. Different kinds of digital quadrature demodulation (DQD) algorithms have come down to the filter design. A novel DQD filter based on the shifted matched filter is introduced in this paper. The performance of different filters is evaluated based on simulated echo data of one point target. Simulation shows that proposed filter can make the DQD meet precision demand and reduce computation greatly. The work in this paper provides a guide to design digital receiver in SAR.

Quadrature decoder filtering circuitry for motor control

Abstract: The disclosed quadrature decoder filtering circuitry for motor control uses one quadrature signal to correct an error in the other quadrature signal, thus allowing a noisy signal due to large dust particles or scratches to be recovered. In some implementations, a system processing for quadrature signals comprises a first circuitry triggered by edges of a first quadrature signal to detect inactivity of a second quadrature signal during consecutive edges of the first quadrature signal. A second circuitry is operable to count the number of consecutive edges of the first quadrature signal during inactivity of the second quadrature signal. A third circuitry is operable to combine transitions of the first quadrature signal with the second quadrature signal during a period of time determined by the count value of the second circuitry.

Low power reconfigurable sub-band filter bank ASIC for MP3 decoder

Abstract: There is an ever demanding need to develop low power audio devices using MP3 technology. From the profiled results of MP3 algorithm on ARM processors, it has been observed that the synthesis filter bank in the audio decoder consumes maximum power. Hence, to reduce the power consumption of the filter bank, we developed an IEEE 754 single precision floating-point runtime reconfigurable architecture. The proposed architecture consumes less power at run time as the last 12 bits of the mantissa part of the synthesis filter coefficients are zero most of the time and, hence, the corresponding multipliers will be switched off. Since the active multipliers during inverse polyphase quadrature mirror filter banks (IPQMF) are less, we are able to achieve low powered decoding process without significantly compromising on the accuracy and speed. We synthesised and simulated the architecture using 0.35 μm process technology under synopsys environment. A uniform worst case power reduction of 23.7% has been achieved in the frequency range from 1 MHz to 20 MHz when all the multipliers are in active state.

Design of FIR Quadrature Mirror-Image Filter Banks Using Fuzzy Adaptive Simulated Annealing

Abstract: An alternative approach for designing quadrature mirror filter (QMF) banks is presented. Although it is used in this paper to fit filter banks to frequency domain specifications, the method is able to be used in other tasks of digital filter synthesis, when it is possible to convert the original problem into a global minimization one. Here, the overall target is to find adequate coefficients for the prototype filter H 0 , so that the filter banks satisfy jointly global performance indices, such as the ripple in the frequency response of the whole system and out of band rejection of the prototype filter. The chosen global optimization algorithm is based upon the well-known simulated annealing paradigm and its implementation known as fuzzy adaptive simulated annealing. The method starts from frequency domain constraints to a generic, parameterized QMF bank family, synthesizes a corresponding real-valued cost function (of prototype filter coefficients) reflecting those constraints and, finally, obtains particular parameter values that determine the proposed optimal system. Besides, it will be presented a multi-objective approach to that classical problem that will make it possible to evaluate tradeoffs involving the complexity of the prototype filter and the reconstruction error produced by the resulting filter bank.

Design of 2-D Perfect Reconstruction Diamond-Shaped and Fan-Shaped FIR Filter Banks

Abstract: The paper gives a design method of two-channel FIR diamond-shaped and fan-shaped filter banks, which are the important part of directional filter banks. Firstly, we make an analysis of 2-D two-channel filter banks where the perfect reconstruction condition is derived. On this basis, the 2-D maximally flat filter is adopted to be the mapping filter and the 1- D two-channel filter bank is constructed to satisfying the perfect reconstruction condition. Afterwards the 1-D two-channel filter bank is mapped into the 2-D diamond-shaped filter bank using the method of variable substitution. Finally the 2-D fan-shaped filter bank is obtained by modulating the diamond-shaped filter bank.

Design of Quadrature Mirror Filter bank using constrained optimisation

Abstract: In this paper, a constrained optimisation technique is used for designing a two-channel Quadrature Mirror Filter Bank (QMFR). A new method is developed based on ideal characteristics of a prototype filter and overall response of the filter bank in transition band. The design problem is formulated as nonlinear constrained optimisation of an objective function, which is weighted sum of square of error in passband, stop band and overall filter bank response at frequency (ω = 0.5 π). For solving optimisation problem, Sequential Quadratic Programming (SQP) optimisation technique is used. The simulation results included illustrate the superiority of the proposed method over the other techniques terms of reconstruction error, mean square error in passband, stopband and transition band.

Design of Digital Quadrature Modulator Based on AD9957

Abstract: Digital quadrature modulator is one of the key parts of Software Radio system.Now the miniature、universal and parameter-configured digital quadrature modulator is required.Based on the features of QDUC chip-AD9957,a new design solution of universal digital quadrature modulator based on AD9957 is proposed,and it features variable parameters,simple hardware structure,high-degree integration,and digital shaping,etc.Finally,the core hardware circuit theory diagram and the experiment results of are given.Test results show that the actual signal performance is basically in consistent with reference data.

Error Resilient Speech Coding Using Sub-band Hilbert Envelopes

Abstract: Frequency Domain Linear Prediction (FDLP) represents a technique for auto-regressive modelling of Hilbert envelopes of a signal. In this paper, we propose a speech coding technique that uses FDLP in Quadrature Mirror Filter (QMF) sub-bands of short segments of the speech signal (25 ms). Line Spectral Frequency parameters related to autoregressive models and the spectral components of the residual signals are transmitted. For simulating the effects of lossy transmission channels, bit-packets are dropped randomly. In the objective and subjective quality evaluations, the proposed FDLP speech codec is judged to be more resilient to bit-packet losses compared to the state-of-the-art Adaptive Multi-Rate Wide-Band (AMR-WB) codec at 12 kbps.

Two-Channel Perfect Reconstruction Filter Banks Using Hilbert Transformers

Abstract: Applying a pi /2 frequency shift to the original twochannel quadrature mirror filter bank (QMFB) yields an equivalent system with two complex half-band filters. Since their coefficients are complex conjugate to each other, one can be removed. The retained filter is a combination of an identity system and a Hilbert transformer, therefore the system is called the quadrature mirror Hilbert transformer (QMHT). However, a perfect reconstruction QMFB is designed by decomposing a zero phase half-band filter into a pair of conjugate mirror filters. The related QMHT is obtained by applying the frequency shift to the zero phase half-band filter before the decomposition. This work establishes the relationship between QMFB and QMHT for systems with perfect reconstruction. For a given QMFB, filter specifications and the design procedure for the QMHT are investigated.

On the use of discrete Wavelet Transform for resolving Channel Impulse Response

Abstract: This paper presents a new Discrete Wavelet Transform (DWT) based technique for resolving multipath components in Channel Impulse Response (CIR). CIR is calculated from channel transfer function (CTF) using Inverse Fast Fourier Transform (IFFT). CTF for scattering from building faces modeled semi-deterministically is found using Method of Moments (MoM). As the CTF is calculated in limited frequency band therefore the time resolution in the CIR is limited. Hence the contributions from scattering centers located in close proximity to each other cannot be identified. In order to overcome this problem DWT as a Quadrature Mirror Filter (QMF) bank is applied to extract the major components in the CIR. Simulation results indicate that DWT can be used to identify the various contributions in the CIR especially the very weak diffracted field components. Results were validated using geometrical optics to verify the proposed technique.

Novel Design of Perfect Reconstructed Quadrature Mirror IIR Filter Banks

Abstract: A novel design for a two-channel IIR quadrature mirror filter(QMF) bank with near-perfect reconstruction was presented in this thesis.The analysis filter bank was given by an efficient poly-phase network implementation based on all-pass filters.The arising phase distortions were almost compensated by the synthesis filter bank.Based on the theo-ry of the perfect reconstruction of QMF,the synthesis filter bank was also given by the stable all-pass filters,designed via analytical closed-form expressions,so the design of IIR QMF was transformed into the design of the phase equali-zer.The simulation results show that the aliasing and amplitude distortions are completely canceled,and phase distortions minimized at the expense of an additional signal delay.The proposed IIR QMF banks have a lower algorithmic complexity and are always stable.

A Simple Alias-Free Linear Phase Quadrature Mirror Filter Bank

Abstract: This paper presents a new algorithm for the design of a two band alias-free linear phase quadrature mirror filter (QMF) bank. The proposed algorithm is based on the optimum value of passband edge frequency ( p ω ) that is found by approximately satisfying the magnitude response condition of the prototype filter at frequency ( 0.5 ωπ = ). In this algorithm, passband edge frequency is optimized. Performances of this algorithm are evaluated in term of computational time, reconstruction error and number of iterations. The design examples given in this paper clearly illustrate the superiority of this algorithm in terms of the peak reconstruction error, computation time, and number of iterations over Creusere and Mitra algorithm. The proposed algorithm is simple, easy to implement, and linear in nature.

An improved structure and design procedure for signed power-of-two lattice QMF bank

Abstract: In this paper, an improved structure and design procedure for signed power-of-two (SPT) lattice quadrature mirror filter (QMF) bank is presented Previous work by the authors has shown that the angle quantization method of lattice coefficient results in a lower approximation error than the direct quantization This paper extends the work by exploiting the rotations which yield more possible sum of SPT representations This enable us to reduce the approximation error further Also, an algorithm for the efficient gathering of candidate discrete coefficients based on the trellis based searching (TBS) approach is developed in order to alleviate the overheads of optimization program Design examples are given to show that the proposed structure and algorithm provide larger stopband attenuation of filter than the existing methods

Fast filter bank using mixed-radix decompositions for an arbitrary number of output channels

Abstract: The Fast Filter Bank has a very low single-rate computational complexity, but is however limited to having powers-of-two number of output channels. In this paper, a new mixed-radix architecture is proposed that allows an arbitrary number of output channels to be implemented.

An Approach for Realization Structure of DWT Using Digital Filters

Abstract: With the rapid development of VLSI, it is essential and possible to use special chips designed for signal processing to make the mathematical transforms faster. Hardware realization structure can provide a way of realizing Mallat's algorithm. In this paper, the author employed digital filter design techniques in wavelet representation of discrete signals. The finite impulse response (FIR) and infinite impulse response (IIR) filters were used as mirror filters based on convolutions with quadrature mirror filtering. Digital filter for down-sampling is proposed and described mainly. This paper showed that the structures of FIR and IIR filters can accomplish the decomposing of a discrete approximation into approximation at a coarser resolution and the detail signal. The realization structure of hardware chips can be used to signal processing, analysis and pattern recognition.

Wavelet Denoising by Using Linear-Phase NPR-QMF Banks

Abstract: In this paper we compare the near-perfect reconstruction (NPR) quadrature mirror filter (QMF) design, versus perfect reconstruction (PR)-QMF design in terms of the flexibility of the design and the design filter characteristics, and their efficiency for denoising of the signals based on wavelet shrinkage technique.

Estimation of Signal Matched Complex Wavelet Filter bank

Abstract: Different properties of complex wavelets were studied and proved theoretically and practically. The dual-tree complex wavelet transform (CWT) is a relatively recent enhancement to the discrete wavelet transform (DWT). It is nearly shift invariant and directionally selective in two and higher dimensions. Firstly equations are formulated for real signal and complex -valued filter coefficients for 2-channel complex filter bank. Secondly the equations are written for complex inputs and complex filters. The matched wavelet filter bank concept is implemented for the dual tree system with the help of derived equations and applied to 1-D and 2-D signals The properties like shift invariant and directional properties are discussed and proved with the suitable diagram. The signal matched wavelet concept of A.Gupta (1) for real wavelets is extended to complex wavelets. The complex fir biorthogonal filter bank system is described. Corresponding closed form equations are derived for the 2-Channel complex filter bank. The properties for real wavelets is extended to complex wavelets.