Showing papers on "Prototype filter published in 2004"

Acoustic Echo and Noise Control: A Practical Approach

Abstract: List of Figures.List of Tables.Preface.Acknowledgments.Abbreviations and Acronyms.Part I: Basics.1 Introduction.1.1 Some History.1.2 Overview of the Book.2 Acoustic Echo and Noise Control Systems.2.1 Notation.2.2 Applications.3 Fundamentals.3.1 Signals.3.2 Acoustic Echoes.3.3 Standards.Part II: Algorithms.4 Error Criteria and Cost Functions.4.1 Error Criteria for Adaptive Filters.4.2 Error Criteria for Filter Design.4.3 Error Criteria for Speech Processing and Control Purposes.5 Wiener Filter.5.1 Time-Domain Solution.5.2 Frequency-Domain Solution.6 Linear Prediction.6.1 Normal Equations.6.2 Levinson{Durbin Recursion.7 Algorithms for Adaptive Filters.7.1 The Normalized Least Mean Square Algorithm.7.2 The Affine Projection Algorithm.7.3 The Recursive Least Squares Algorithm.7.4 The Kalman Algorithm.Part III: Acoustic Echo and Noise Control.8 Traditional Methods for Stabilization of Electroacoustic Loops.8.1 Adaptive Line Enhancement.8.2 Frequency Shift.8.3 Controlled Attenuation.9 Echo Cancellation.9.1 Processing Structures.9.2 Stereophonic and Multichannel Echo Cancellation.10 Residual Echo and Noise Suppression.10.1 Basics.10.2 Suppression of Residual Echoes.10.3 Suppression of Background Noise.10.4 Combining Background Noise and Residual Echo Suppression.11 Beamforming.11.1 Basics.11.2 Characteristics of Microphone Arrays.11.3 Fixed Beamforming.11.4 Adaptive Beamforming.Part IV: Control and Implementation Issues.12 System Control-Basic Aspects.12.1 Convergence versus Divergence Speed.12.2 System Levels for Control Design.13 Control of Echo Cancellation Systems.13.1 Pseudooptimal Control Parameters for the NLMS Algorithm.13.2 Pseudooptimal Control Parameters for the Affine Projection Algorithm.13.3 Summary of Pseudooptimal Control Parameters.13.4 Detection and Estimation Methods.13.5 Detector Overview and Combined Control Methods.14 Control of Noise and Echo Suppression Systems.14.1 Estimation of Spectral Power Density of Background Noise.14.2 Musical Noise.14.3 Control of Filter Characteristics.15 Control for Beamforming.15.1 Practical Problems.15.2 Stepsize Control.16 Implementation Issues.16.1 Quantization Errors.16.2 Number Representation Errors.16.3 Arithmetical Errors.16.4 Fixed Point versus Floating Point.16.5 Quantization of Filter Taps.Part V: Outlook and Appendixes.17 Outlook.Appendix A: Subband Impulse Responses.A.1 Consequences for Subband Echo Cancellation.A.2 Transformation.A.3 Concluding Remarks.Appendix B: Filterbank Design.B.1 Conditions for Approximately Perfect Reconstruction.B.2 Filter Design Using a Product Approach.B.3 Design of Prototype Lowpass Filters.B.4 Analysis of Prototype Filters and the Filterbank System.References.Index.

Dual-band bandpass filters using equal-length coupled-serial-shunted lines and Z-transform technique

Abstract: A synthesizing method is presented to design and implement digital dual-band filters in the microwave frequency range. A dual-band filter consists of a bandstop filter and a wide-band bandpass filter in a cascade connection, wherein the transfer functions of both the bandpass filter and bandstop filter are expressed in the Z domain. The bandstop filter is implemented by using a coupled-serial-shunted line structure, while the wide-band bandpass filter is constructed by using a serial-shunted line configuration. In particular, the bandwidth of each passband of the dual-band filter is controllable by adjusting the characteristics of both the bandpass filter and bandstop filter. By neglecting the dispersion effect between microstrip lines of different widths over a wide bandwidth, a dual-band filter is realized in the form of microstrip lines and its frequency responses are measured to validate this method.

Control of bandstop response of Hi-Lo microstrip low-pass filter using slot in ground plane

Abstract: This paper examines the effect of the geometrical shapes of a defected ground-plane structure (DGS) slot on performance of the Hi-Lo microstrip low-pass filter (LPF). A three-pole LPF based on an arrowhead DGS slot has 67% less length as compared to a conventional three-pole LPF. It has insertion loss of 0.5 dB and 15-dB rejection in the stopband up to three times the cutoff frequency.

Use of nondegenerate resonant leaky modes to fashion diverse optical spectra

Abstract: In this paper, we show that bandstop and bandpass filters with versatile spectral attributes can be implemented with modulated films possessing asymmetric grating profiles. The profile asymmetry breaks the resonant leaky mode degeneracy at normal incidence thereby permitting precise spectral spacing of interacting leaky modes with interesting implications in optical filter design. Several example filters, containing only a single grating layer, are designed with this methodology to demonstrate the concept.

Parallel coupled microstrip filters with ground-plane aperture for spurious band suppression and enhanced coupling

Abstract: Parallel coupled microstrip sections with a slotted ground plane are proposed as building blocks of coupled-line microstrip filters with enhanced performance. It is shown that, by proper adjustment of the ground-plane slot dimensions, the double frequency spurious band associated with unequal even/odd electrical lengths can be suppressed or meaningfully reduced. As an additional feature, this simple design relaxes tolerances of strip width and spacing in those cases where tightly coupled high-impedance sections are required. A rough preliminary design can be obtained within a few seconds using a fast optimization algorithm based on a quasi-TEM analysis of the coupled sections. Fine tuning is based on the use of a commercial electromagnetic simulator. Finally, experimental check of filter performance is provided.

Practical analog and digital filter design

Abstract: Introduction to Filters and Filter Design Software. Analog Filter Approximation Functions. Analog Lowpass, Highpass, Bandpass, and Bandstop Filters. Analog Filter Implementation Using Active Filters. Introduction to Discrete-Time Systems. Infinite Impulse Response Digital Filter Design. Finite Impulse Response Digital Filter Design. Digital Filter Implementation Using C. Digital Filtering Using the FFT. Appendices.

Passive enhancement of resonator Q in microwave notch filters

Abstract: The lumped-element bridged-T notch filter concept is extended to reciprocal distributed-element microwave filters. A prototype microstrip bridged-T notch filter employing single-mode resonators is described that enhances the effective resonator Q/sub u/ by a factor of 325, while a different microstrip filter topology with a triple-mode resonator is described that enhances the effective resonator Q/sub u/ by a factor of 89. The new notch filters can be either partly reflective or fully absorptive within the stopband. Additional enhanced-Q/sub u/ notch filter topologies, such as a hybrid-coupler notch filter, that include at least two resonances and at least two signal paths are suggested.

Efficient wideband channelizer for software radio systems using modulated PR filterbanks

Abstract: An efficient method is proposed for channelizing frequency division multiplexed (FDM) channels in wideband software radio (SWR) received signals that do not satisfy the conditions required for polyphase decomposition of the discrete filterbank (DFB) channelizer The proposed method, which uses modulated perfect reconstruction (PR) filterbanks, requires fewer computations than DFBs for channelizing wideband signals that are composed of FDM channels of nonequal bandwidths, especially when a large number of channels are extracted The proposed channelizer, if applied in the reverse direction, can be used to synthesize a set of channels with nonequal bandwidths into a single wideband signal in SWR transmitters A method is also proposed for efficiently designing the modulated PR filterbanks, which have a large number of subchannels and prototype filters with high stopband attenuations that are used in the proposed channelizer The computational complexity of the proposed channelizer is compared with the complexity of the DFB channelizer for channelizing the wideband and high-dynamic-range signals that are typical of SWR systems, and simulation results of the proposed channelization method are discussed

Improved structures of maximally decimated directional filter Banks for spatial image analysis

Abstract: This paper introduces an improved structure for directional filter banks (DFBs) that preserves the visual information in the subband domain. The new structure achieves this outcome while preserving both the efficient polyphase implementation and the exact reconstruction property. The paper outlines a step-by-step framework in which to examine the DFB, and within this framework discusses how, through the insertion of post-sampling matrices, visual distortions can be removed. In addition to the efficient tree structure, attention is given to the form and design of efficient linear phase filters. Most notably, linear phase IIR prototype filters are presented, together with the design details. These filters can enable the DFB to have more than a three-fold improvement in complexity reduction over quadrature mirror filters (QMFs).

Design techniques for orthogonal Modulated filterbanks based on a compact representation

Abstract: This paper presents a method to design perfect reconstruction orthogonal modulated filterbanks having a very large number of subbands. At first, using the angular parameterization of the underlying lattice structure, the problem is formulated as an unconstrained optimization problem. Then, it is shown for two different optimization criteria (the minimization of the out-of-band energy and the maximization of the time-frequency localization) that the optimized lattice coefficients can be interpolated in two different ways. A first characterization takes advantage of the fact that the angles related to successive polyphase components of the prototype filter have a smooth behavior. A new parameterization, named compact representation, is therefore introduced, which shows that a linear increase of the number of parameters with respect to the number of subbands can be avoided with practically no loss of accuracy. A second observation concerns the also smooth behavior of each angular parameter when considering an increasing number of subbands. The efficiency of the two approaches is illustrated by the design of filterbanks with a large number of subbands going from 32 up to 4096, including prototype filters up to a length of 32 768.

All-pass filters based on CCII- and CCCII-

Abstract: This paper proposes a first-order all-pass filter using one negative type second-generation current conveyor (CCII−), two resistors and a capacitor. From the proposed CCII− based filter, by replacing the CCII− and a resistor by a negative second-generation current-controlled conveyor (CCCII−) a new filter is developed which requires only one each of CCCII−, capacitor and resistor. The experimental and simulated results are found in good agreement with theoretical analysis. The circuits are also analyzed for non-ideal current conveyors to show that they still function as all-pass filters but with slight altered values of gain and phase.

Dual-band coupling and feed structure for microstrip filter design

Abstract: A new configuration of dual-band filter design is presented in this paper. Stepped-impedance transmission-line sections are used as the tunable dual-band resonators. New coupling structures and matching networks at input and output are also proposed to achieve a dual-band characteristics. Three filters with their second passband at 1.5, 2, and 2.5 times the fundamental frequency are designed as examples, and they are all verified by experimental results.

Wideband coplanar-waveguide bandpass filters with good stopband rejection

Abstract: Wideband coplanar-waveguide (CPW) bandpass filters based on the cascade of CPW lowpass and highpass periodic structures are proposed. The upper and lower stopband characteristics of proposed bandpass filter can be easily designed by separately adjusting the lowpass and highpass sections, respectively. Specifically, two wideband CPW bandpass filters with sharp roll-off at passband edges and good stopband rejection are demonstrated.

Generalized selection weighted vector filters

Abstract: This paper introduces a class of nonlinear multichannel filters capable of removing impulsive noise in color images. The here-proposed generalized selection weighted vector filter class constitutes a powerful filtering framework for multichannel signal processing. Previously defined multichannel filters such as vector median filter, basic vector directional filter, directional-distance filter, weighted vector median filters, and weighted vector directional filters are treated from a global viewpoint using the proposed framework. Robust order-statistic concepts and increased degree of freedom in filter design make the proposed method attractive for a variety of applications. Introduced multichannel sigmoidal adaptation of the filter parameters and its modifications allow to accommodate the filter parameters to varying signal and noise statistics. Simulation studies reported in this paper indicate that the proposed filter class is computationally attractive, yields excellent performance, and is able to preserve fine details and color information while efficiently suppressing impulsive noise. This paper is an extended version of the paper by Lukac et al. presented at the 2003 IEEE-EURASIP Workshop on Nonlinear Signal and Image Processing (NSIP '03) in Grado, Italy.

Method and apparatus for single burst equalization of single carrier signals in broadband wireless access systems

Abstract: A receiver implementing a single carrier single burst equalization (SC-SBE) method is capable of achieving near optimal reception of individual single carrier RF bursts by making an accurate estimate of the burst's propagation channel impulse response (CIR). The SC-SBE method uses a CIR based coefficient computation process to obtain filter coefficients for a minimum mean square error decision feedback equalizer (MMSE-DFE). The MMSE-DFE filter computation process computes a sufficiently large number of coefficients for the DFE filters, i.e., the feed forward filter (FFF) and feedback filter (FBF), so that each filter spans the maximum anticipated length of the CIR. In order to implement the filters efficiently, a coefficient selection process eliminates less significant computed FFF and FBF coefficients. The resulting FFF and FBF are sparse filters in that most of the taps in the filter delay lines do not have a filter coefficient. Such filters may be efficiently implemented in the time domain.

Direct synthesis of a new class of bandstop filters

Abstract: A direct synthesis technique of a new class of bandstop coupled resonator elliptic filters is presented. Two different coupling schemes, which both include source-load coupling are used. The first coupling and routing scheme is the standard folded structure used in implementing bandpass elliptic filters with N transmission zeros using N resonators. The second coupling scheme is identical to the multipath parallel structure, which was recently introduced for the synthesis of fully elliptic bandpass filters. In both cases, the source and load are directly coupled by an inverter in order to generate the required transmission zeros. It is shown that, for each coupling scheme, two distinct solutions that are not related by a similarity transformation exist. Furthermore, the two solutions both have realistic coupling coefficients in contrast to the bandpass case where only one solution, in general, is practical. It is also shown that the same coupling scheme can implement pseudoelliptic bandstop filters with N/sub z/ reflection zeros where 0/spl les/N/sub z//spl les/N.

Design of minimum phase digital IIR filters by using genetic algorithm

Abstract: Genetic Algorithm (GA) based design techniques are widely proposed for IIR filters. However, the unstability problem and the phase distortion occurring during the design process are important disadvantages for IIR filters. In this work, an effective design method using GA for minimum phase and stable digital IIR filters is presented.

Coplanar quarter-wavelength quasi-elliptic filters without bond-wire bridges

Abstract: This paper presents the design and experimental results of two coplanar quarter-wavelength microwave filters operating at a frequency of approximately 3 GHz. Coplanar designs are of particular interest because they are less sensitive to the thickness of the dielectric substrate than other transmission-line types such as a microstrip. One of the designs has a quasi-elliptic frequency response. In addition, the design also eliminates problems with unbalancing of the ground planes normally present in coplanar structures. Bond wires between the ground planes are not required. This paper describes in detail the structure of the resonators and how they are coupled together to form a filter.

Efficient design of oversampled NPR GDFT filterbanks

Abstract: We propose a flexible, efficient design technique for the prototype filter of an oversampled near perfect reconstruction (NPR) generalized discrete Fourier transform (GDFT) filterbank. Such filterbanks have several desirable properties for subband processing systems that are sensitive to aliasing, such as subband adaptive filters. The design criteria for the prototype filter are explicit bounds (derived herein) on the aliased components in the subbands and the output, the distortion induced by the filterbank, and the imaged subband errors in the output. It is shown that the design of an optimal prototype filter can be transformed into a convex optimization problem, which can be efficiently solved. The proposed design technique provides an efficient and effective tool for exploring many of the inherent tradeoffs in the design of the prototype filter, including the tradeoff between aliasing in the subbands and the distortion induced by the filterbank. We calculate several examples of these tradeoffs and demonstrate that the proposed method can generate filters with significantly better performance than filters obtained using current design methods.

Novel all-optical RF notch filters with equivalent negative tap response

Abstract: New all-optical radio-frequency notch filters with frequency response equivalent to two-tap negative tap notch filters are presented. Two topologies are described, based on a dual-output electrooptic modulator that undergoes double-pass modulation, and whose phase difference of the modulated signals at the outputs are used to obtain equivalent negative tap behavior in the notch filter response. Results are presented for the novel structures, which demonstrate the realization of an equivalent negative tap notch filter response, and which also show the important advantages of eliminating coherence and phase noise limitations in the operation of the processors.

Theory for the design of C-type filter

Abstract: Based on the theoretical analysis, the paper introduces an algorithm for calculating the parameters of C-type filter that has not been published before. Firstly, the relationships of all parameters are established and discussed. Then, parameters with lowest cost filter are derived, and the method is testified by the parameters of C-type filters having been used in some HVDC projects.

Design of practically perfect-reconstruction cosine-modulated filter banks: a second-order cone programming approach

Abstract: Designing optimal perfect-reconstruction (PR) and near PR (NPR) cosine-modulated filter banks is essentially a constrained nonlinear minimization problem. This paper proposes two second-order cone-programming based algorithms for designing NPR and practically PR cosine-modulated filter banks with improved performance relative to several established design methods.

Pole-zero diagram approach to the design of ring resonator-based filters for photonic applications

Abstract: The pole-zero diagram is a tool that has been widely employed in digital and electronic filter design. It greatly facilitates filter design by producing a simple and direct visualization of parametrical behaviors and general spectral characteristics. In this paper, we propose new methods of applying pole-zero diagrams to photonic filter design, aimed at tailoring spectral characteristics. In particular, we demonstrate the effectiveness of this method in designing ring resonator-based filters for application to optical wavelength interleavers and deinterleavers. We show that there exist close relations between the pole-zero diagram of an optical filter and its wavelength response, and derive pole-zero diagrams for filters with various ring resonator configurations. Further, we propose a novel graphical technique using pole-zero diagrams for optimizing filter performance. As a practical example to demonstrate the effectiveness of the pole-zero approach, we present a new wavelength interleaver design with low crosstalk. This design was realized by superimposing the pole-zero diagrams of parallel and series-coupled ring resonator arrays.

RF transversal filter using an AOTF

Abstract: An acoustooptic tunable filter (AOTF) is employed in an optical system to obtain an independently tunable and reconfigurable radio-frequency transversal filter. Manipulating only the control signals of the AOTF modifies the transfer function of the filter. This letter demonstrates the experimental implementation of a two-tap version of the proposed filter. Avenues for increasing the number of taps are discussed.

Adjustable 60Hz noise reduction by a notch filter for ECG signals

Abstract: After the analog ECG signal is transferred into digital format, the digital filter can be used to suppress the 60 Hz embedded noise. In this paper, we propose the use of finite impulse response filters with a linear phase property to obtain the noise reduction without introducing the phase distortion. In our design, we use the notch filter with a pole/zero canceling method, the comb notch filter with a pole/zero canceling method and the equiripple notch filter with the usage of the Parks-McClellan algorithm. By the comparison of the transition bandwidth (/spl Delta//spl omega/), stopband attenuation gain (Astop) of these filters, we can learn the frequency response of these filters. Furthermore, we use the mean square error (MSE) to estimate the effect of the digital filters in order to reduce the embedded 60 Hz noise. We compute the mean square error with respect to the order, N, of these filters and plot the relationship of MSE and N. In addition, we find the relationship of the CPU time and N, and we also learn that the CPU time is in proportion to the order, N, of the filters. According to the relations among N, MSE and CPU time, we can find that the advantages and disadvantages of the proposed filters and then choose the best filter for the corresponding conditions.

RF Bulk Acoustic Wave Resonators and Filters

Abstract: Small sized, highly selective solidly mounted bulk acoustic wave (BAW) band pass filters are of great interest for mobile and wireless systems operating in the frequency range of 0.8 GHz up to more than 10 GHz. They can be fabricated on silicon or glass wafers using standard semiconductor integration techniques. These filters are based on electro-acoustic high Q resonators, which exploit the thickness extensional mode of a thin piezoelectric AlN or ZnO film. This film has to be grown with its polar axis, oriented perpendicular to the substrate. Both the deposition process and using a textured electrode support excellent c-axis oriented growth and thus high electromechanical coupling coefficient kt and filter bandwidth. Modelling of the filter and resonator response is performed by means of a combination of a 1D electro-acoustic model together with an electromagnetic model. The paper shows examples of filters operating in the range between 2 and 8 GHz.

Using scattering parameters to characterize EMI filters

Abstract: In this paper, the EMI filter is first characterized by S-parameters. Based on this S-parameters model, the insertion voltage gain of EMI filters with arbitrary source and load impedances are derived. Experiments are carried out to verify this approach. The S-parameters with current bias are also measured to characterize the EMI filter under current bias conditions. The concept of waves is then used to interpret the impedance requirement of the filters. Finally, the predictions on filter insertion voltage gain with practical source impedances are compared with the results from the measurement and the effects of the source impedances are analyzed.

Miniature high-Q double-spiral slot-line resonator filters

Abstract: A new class of low insertion-loss miniaturized filters using slot-line resonators is proposed. Miniaturization is achieved by terminating the slot line with a double-spiral inductive termination at both ends. Using this miniaturized resonator, both positive and negative couplings may be realized, and therefore, both standard coupled-line and cross-coupled quasi-elliptic filters are realizable. The unloaded Q of these slot-line filters is considerably higher than that of miniaturized microstrip filters of comparable dimensions due to the inherent higher Q of the slot line. To demonstrate the validity of the design procedures and the performance characteristics, two different types of filters were fabricated and tested. One is a four-pole Chebyshev filter and the other is a quasi-elliptic filter where, in each case, the full-wave simulations show very good agreement with measurements.

Novel inductance-incorporated microstrip coupled-line bandpass filters with two attenuation poles

Abstract: A microstrip coupled-line bandpass filter with good stopband rejection is proposed. By introducing an additional shunt inductance to the conventional coupled-line filter, along with the capacitively coupled gap between coupled-line sections, two attenuation poles at upper and lower stopbands may be achieved without increasing the circuit area. The proposed filter exhibits good stopband rejection with no repeated passband at twice the center frequency as compared to the conventional coupled-line filters. Specifically, a microstrip coupled-line bandpass filter centered at 2.4 GHz with 5.4% 3-dB bandwidth and two attenuation poles is implemented.