Showing papers on "Prototype filter published in 2000"

High-Q HF microelectromechanical filters

Abstract: IC-compatible microelectromechanical intermediate frequency filters using integrated resonators with Q's in the thousands to achieve filter Q's in the hundreds have been demonstrated using a polysilicon surface micromachining technology. These filters are composed of two clamped-clamped beam micromechanical resonators coupled by a soft flexural-mode mechanical spring. The center frequency of a given filter is determined by the resonance frequency of the constituent resonators, while the bandwidth is determined by the coupling spring dimensions and its location between the resonators. Quarter-wavelength coupling is required on this microscale to alleviate mass loading effects caused by similar resonator and coupler dimensions. Despite constraints arising from quarter-wavelength design, a range of percent bandwidths is still attainable by taking advantage of low-velocity spring attachment locations. A complete design procedure is presented in which electromechanical analogies are used to model the mechanical device via equivalent electrical circuits. Filter center frequencies around 8 MHz with Q's from 40 to 450 (i.e., percent bandwidths from 0.23 to 2.5%), associated insertion losses less than 2 dB, and spurious-free dynamic ranges around 78 dB are demonstrated using low-velocity designs with input and output termination resistances of the order of 12 k/spl Omega/.

Higher order filter response in coupled microring resonators

Abstract: Second- and third-order filter response is experimentally shown in filters constructed using mutually coupled microring resonators. The higher order filters have passbands with sharper rolloff and flatter tops, and greater out-of-band rejection than previously demonstrated microring filters, which were first order. The effect of varying interesonator coupling on filter passband shape was studied.

Design of highly selective microstrip bandpass filters with a single pair of attenuation poles at finite frequencies

Abstract: This paper presents the design of a class of highly selective microstrip bandpass filters that consist of microstrip open-loop resonators that exhibit a single pair of attenuation poles at finite frequencies. A practical design technique for this class of filters is introduced, including tables and formulas for accurate and fast filter synthesis. Two design examples of a six-pole filter with a fractional bandwidth of 7.331% at 955 MHz and an eight-pole filter with a fractional bandwidth of 10.359% at 985 MHz are described. Theoretical and experimental results are presented. The compact size and the excellent performance of this class of filters have been demonstrated.

Least-squares design of IIR filters with prescribed magnitude and phase responses and a pole radius constraint

Abstract: This paper presents a method for the frequency domain design of infinite impulse response (IIR) digital filters. The proposed method designs filters approximating prescribed magnitude and phase responses. IIR filters of this kind can have approximately linear-phase responses in their passbands, or they can equalize magnitude and phase responses of given systems. In many cases, these filters can be implemented with less memory and with fewer computations per output sample than equivalent finite impulse response (FIR) digital filters. An important feature of the proposed method is the possibility to specify a maximum radius for the poles of the designed rational transfer function. Consequently, stability can be guaranteed, and undesired effects of implementations using fixed-point arithmetic can be alleviated by restricting the poles to keep a prescribed distance from the unit circle. This is achieved by applying Rouche's theorem in the proposed design algorithm. We motivate the use of IIR filters with an unequal number of poles and zeros outside the origin of the complex plane. In order to satisfy simultaneous specifications on magnitude and phase responses, it is advantageous to use IIR filters with only a few poles outside the origin of the z-plane and an arbitrary number of zeros. Filters of this type are a compromise between IIR filters with optimum magnitude responses and phase-approximating FIR filters. We use design examples to compare filters designed by the proposed method to those obtained by other methods. In addition, we compare the proposed general IIR filters with other popular more specialized structures such as FIR filters and cascaded systems consisting of frequency-selective IIR filters and phase-equalizing allpass filters.

Aperture compensation technique for innovative design of ultra-broadband microstrip bandpass filter

Abstract: Aperture compensation technique is proposed for the enhancement of coupling strength in the parallel-coupled microstrip line (PCML). Through applying a so-called "short-open calibration" procedure in our full-wave MoM algorithm, this PCML is characterized by an equivalent J-inverter network. A novel bandpass filter with a single resonator is designed through its equivalent circuit topology. Both predicted and measured results show its ultra-broadband and multi-pole bandpass behavior with BW>70% and |S/sub 11/|<-15 dB.

Efficient modified-sinc filters for sigma-delta A/D converters

Abstract: In this paper, a method to design and implement a very efficient multistage decimation filter for a sigma-delta (/spl Sigma//spl Delta/) A/D converter is proposed The scheme is composed of two stages, but the proposed method can be easily extended to a multiple-stage implementation The first-stage filter is obtained by properly rotating the zero-pole distribution of a comb filter in the z-plane The obtained structure exhibits linear phase and can be implemented by using a recursive structure with only two multipliers The design phase is easy and very flexible As most of the quantization noise is eliminated at the first stage, the second-stage filter can be designed with relaxed specifications Any classical design algorithm can be used for it An alternative scheme for the second stage can be obtained by splitting the stage into two substages, and the method proposed in this paper can be iterated

Cosine-modulated filterbanks based on extended Gaussian functions

Abstract: A new family of cosine-modulated filterbanks based on functions called extended Gaussian functions (EGFs) is obtained. The design is particularly simple since it is mainly based on a closed-form expression. Nearly perfect reconstruction cosine-modulated filterbanks are obtained as well as guidelines to estimate the filterbank parameters. This analytical design method can be used to produce, with a controlled accuracy, filterbanks with practically no upper limitations in the number of coefficients and subbands. Furthermore, a slight modification of the prototype filter coefficients is sufficient to satisfy exactly the perfect reconstruction constraints. An analysis of the time-frequency localization of the discrete prototype filters also shows that under certain conditions, EGF prototypes are at less than 0.3% from the optimal upper bound.

Widely programmable high-frequency continuous-time filters in digital CMOS technology

Abstract: We present design considerations for programmable high-frequency continuous-time filters implemented in standard digital CMOS processes. To reduce area, accumulation MOS capacitors are used as integrating elements. The filter design problem is examined from the viewpoint of programmability. To allow frequency scalability without deterioration of noise performance and of the frequency response shape, we employ a technique called "constant-capacitance scaling," which assures that even parasitic capacitances remain invariant when transconductors are switched in and out of the filter. This technique is applied to the design of a programmable fourth order Butterworth continuous-time filter with a bandwidth programmable from 60 to 350 MHz implemented in a 0.25-/spl mu/m digital CMOS process. The filter has a dynamic range of 54 dB, dissipates 70 mW from a 3.3-V supply, and occupies an area of 0.15 mm/sup 2/.

General IIR optical filter design for WDM applications using all-pass filters

Abstract: A general design algorithm is presented for infinite impulse response (IIR) bandpass and arbitrary magnitude response filters that use optical all-pass filters as building blocks. Examples are given for an IIR multichannel frequency selector, an amplifier gain equalizer, a linear square-magnitude response, and a multi-level response. Major advantages are the efficiency of the IIR filter compared to finite impulse response (FIR) filters, the simplicity of the optical architecture, and its tolerance for loss. A reduced set of unique operating states is discussed for implementing a reconfigurable multichannel selection filter.

Canonical signed digit representation for FIR digital filters

Abstract: It is shown that the use of a canonical signed digit (CSD) representation of the filter coefficients can significantly reduce the complexity of the hardware implementation of digital FIR filters. This paper presents an example filter design that shows the error involved in limiting the number of allowable non-zero CSD coefficients for a real FIR bandpass filter. If not done carefully, brute force limiting can lead to large errors in the frequency response. The error is evaluated for varying numbers of non-zero CSD coefficients. Lastly, a system level architecture with a multiplier utilizing the properties of the CSD number representation system is proposed.

Optical half-band filters

Abstract: This paper proposes two kinds of novel 2/spl times/2 circuit configuration for finite-impulse response (FIR) half-band filters. These configurations can be transformed into each other by a symmetric transformation and their power transmittance is identical. The configurations have only about half the elements of conventional FIR lattice-form filters. We derive a design algorithm for achieving desired power transmittance spectra. We also describe 2/spl times/2 circuit configurations for infinite-impulse response (IIR) half-band filters. These configurations are designed to realize arbitrary-order IIR half-band filter characteristics by extending the conventional half-band circuit configuration used in millimeter-wave devices. We discuss their filter characteristics and confirm that they have a power half-band property. We demonstrate design examples including FIR maximally flat half-band filters, an FIR Chebyshev half-band filter, and an IIR elliptic half-band filter.

Characteristics of the Vold-Kalman order tracking filter

Abstract: The filter characteristics of the Vold-Kalman (1993, 1960, 1961) order tracking filter are presented. Both the frequency response as well as the time response and their time-frequency relationship have been investigated for different filter types and guidelines for optimum choice of filter parameters are presented. The Vold-Kalman filter allows for the high performance simultaneous tracking of orders in systems with multiple independent shafts. With this new filter and using multiple tacho references, waveforms, as well as amplitude and phase may be extracted without the beating interactions that are associated with conventional methods. Orders extracted as waveforms have no phase bias, and may hence be used for playback, synthesis and tailoring.

FIR and IIR digital filters

Abstract: A digital filter is a basic building block in any digital signal processing (DSP) system. The simulation results presented show how finite bit precisions can affect the performance of a digital filter. IIR filters are shown to be even more susceptible to finite bit precision effects than FIR filters. However, these effects can be reduced using the IIR filter with a cascaded structure.

On the performance of HTS microstrip quasi-elliptic function filters for mobile communications application

Abstract: The low-loss and high-selective high-temperature superconducting (HTS) bandpass filters can enhance performance of mobile communications systems. In this paper, we summarize a recent progress of novel HTS preselect bandpass filters that have been developed for a European research project. The objective of the project is to construct an HTS-based transceiver for mast-mounted DCS1800 base stations. The HTS preselect receive filters have been designed to have a quasi-elliptic function response in order to provide low insertion loss and very steep rolloff at the filter band edges. The filters cover a 15-MHz sub-band of a receive band, which ranges from 1710 to 1785 MHz. The filters have been fabricated using double-sided YBCO thin films on 03-mm-thick MgO or 0.5-mm-thick LAO substrates. The latest experimental results of the filters, including those encapsulated with a low-noise amplifier in an RF module are presented, showing very promising performance. The issues associated with asymmetric frequency response are investigated to improve the filter performance.

Systematic design of EMI-filters for power converters

Abstract: EMI-filters are often designed by trial and error. To take guesswork out of filter design, a systematic approach is described in this paper. The design procedure is divided into three steps: (1) measurement of the impedance and amplitude spectrum of the noise source; (2) determination of the sink impedance; (3) calculation of the filter component values to fulfil a given limit curve with least costs for the overall filter. Using this design procedure, the filter topology, the filter order and the component values are determined to provide a lowest cost EMI-filter design.

Fast implementation of oversampled modulated filter banks

Abstract: This paper presents an efficient implementation of oversampled filter banks derived from a prototype filter by modulation. Via a polyphase analysis, redundancies in the filter operations are removed. With some modifications, a very simple and efficient implementation is found, which is briefly compared to existing realisations.

Modulated filter banks with arbitrary system delay: efficient implementations and the time-varying case

Abstract: We present a new method for the design and implementation of modulated filter banks with perfect reconstruction. It is based on the decomposition of the analysis and synthesis polyphase matrices into a product of two different types of simple matrices, replacing the polyphase filtering part in a modulated filter bank. Special consideration is given to cosine-modulated as well as time-varying filter banks. The new structure provides several advantages. First of all, it allows an easy control of the input-output system delay, which can be chosen in single steps of input sampling rate, independent of the filter length. This property can be used in audio coding applications to reduce pre-echoes. Second, it results in a structure that is nearly twice as efficient as performing the polyphase filtering directly. Perfect reconstruction is a structurally inherent feature of the new formulation, even for nonlinear operations or time-varying coefficients. Hence, the structure is especially suited for the design of time-varying filter banks where both the number of bands as well as the prototype filters can be changed while maintaining perfect reconstruction and critical sampling. Further, a proof of effective completeness is given, and the design of equal magnitude-response analysis and synthesis filter banks is described. Filter design can be performed by nonconstrained optimization of the matrix coefficients according to a given cost function. Design and audio-coding application examples are given to show the performance of the new filter bank.

Active and hybrid filters for power conditioning

Abstract: This paper describes principles, system configurations, control strategies and implementations, and filtering characteristics of active and hybrid filters for power conditioning. Their practical applications are expanding not only into office-buildings, hospitals, water supply utilities and rolling stock but also into electric power utilities. For example, a hybrid filter consisting of a 5 MVA series active filter and a 25 MVA shunt passive filter has been installed at the Yamanashi test line for high-speed magnet-levitation trains. The series active filter makes a great contribution to damping of harmonic resonance between the supply inductor and the shunt passive filter.

An algorithm for integrated noise reduction and sharpness enhancement

Abstract: Noise reduction and image sharpening are techniques to improve video image quality. However, noise filters tend to blur image detail, while filters for image sharpening tend to increase noise. So, cascading the two filters does not always give the best performance. We present an integrated filter that reduces noise and sharpens details in a noisy video signal depending on local image statistics. This allows both features to be maximally exploited.

Design considerations for narrow-band dielectric resonant grating reflection filters of finite length

Abstract: An interference-waveguide approach is developed to predict the response of a resonant grating reflection filter and to provide a better understanding of the resonant process. An expression for the reflected field that accounts for all internal boundary reflections within the filter is developed. Under the assumption of an antireflective design, expressions characterizing the line shape of a filter of infinite length are first developed; then the effects of finite length on the response are determined. Expressions relating the length of the filter to the peak reflection efficiency and line width are developed. The degradation of the response as a function of filter length is evaluated. An equivalent waveguide representation is used to determine the location of the resonance as well as the spectral and angular linewidths of the filter. The minimum obtainable spectral linewidth for a filter of given length is determined to be on the order of Δλ∼λ2/L. Rigorous analysis is used to verify the interference-waveguide approach.

Design of digital filters and filter banks by optimization: A state of the art review

Abstract: The many advancements in the area of numerical optimization in conjunction with the ever-increasing power of computers have made optimization-based filter design an increasingly important field of research. In this paper, several recent optimization methods for the design of FIR and IIR digital filters and filter banks are reviewed.

Microstrip triangular patch resonator filters

Abstract: In this paper we present some results of a primary development of microstrip bandpass filters comprised of triangular patch resonators for high temperature superconducting (HTS), micromachined circuits and other applications. Advantages of a triangular patch resonator filter are not only its higher capability of power handling, but also its natural circuit topology that can inherently implement finite-frequency transmission zeros in a simple cascading structure. In order to have the transmission zeros on the either side of the passband, two different resonant modes of triangular patch resonators are employed. Two three-pole filters of this type, which may form the basic units for higher order filters, are for the first time demonstrated both theoretically and experimentally.

High-speed recursive digital filters based on the frequency-response masking approach

Abstract: The frequency-response masking approach for highspeed recursive infinite-impulse response (IIR) digital filters is introduced. In this approach, the overall filter consists of a periodic model filter, its power-complementary periodic filter, and two masking filters. The model filters are composed of two all-pass filters in parallel, whereas the masking filters are linear-phase finite-impulse response (FIR) filters. The transfer functions of the all-pass filters are functions of z/sup M/, which implies that the maximal sample frequency for the overall filter is M times that of the corresponding conventional IIR filter. The maximal sample frequency can be increased to an arbitrary level for arbitrary bandwidths. The overall filter can be designed by separately optimizing the model and masking filters with the aid of conventional approximation techniques. The obtained overall filter also serves as a good initial filter for further optimization. Both nonlinear-phase and approximately linear-phase filters are considered. By using the new approach, the potential problems of pole-zero cancellations, which are inherent in algorithm transformation techniques, are avoided. Further, robust filters under finite-arithmetic conditions can always be obtained by using wave-digital all-pass filters and nonrecursive FIR filters. Several design examples are included illustrating the properties of the new filters.

Noncausal spatial prediction filtering for random noise reduction on 3-D poststack data

Abstract: A common practice in random noise reduction for 2-D data is to use pseudononcausal (PNC) 1-D prediction filters at each temporal frequency. A 1-D PNC filter is a filter that is forced to be two sided by placing a conjugate‐reversed version of a 1-D causal filter in front of itself with a zero between the two. For 3-D data, a similar practice is to solve for two 2-D (causal) one‐quadrant filters at each frequency slice. A 2-D PNC filter is formed by putting a conjugate flipped version of each quadrant filter in a quadrant opposite itself. The center sample of a 2-D PNC filter is zero. This paper suggests the use of 1-D and 2-D noncausal (NC) prediction filters instead of PNC filters for random noise attenuation, where an NC filter is a two‐sided filter solved from one set of normal equations. The number of negative and positive lags in the NC filter is the same. The center sample of the filter is zero. The NC prediction filters are more center loaded than PNC filters. They are conjugate symmetric as PNC fi...

Hybrid filter control system with adaptive filters for selective elimination of harmonics and interharmonics

Abstract: The interharmonics produced by some classes of nonlinear loads limit the effectiveness of classical passive filter compensation and active compensation must be considered. In high-voltage, high-power applications hybrid filter systems are technically justified and cost-effective solutions. Hybrid filter control strategies successfully employed in the compensation of high-power rectifier loads based on the detection of the total current distortion are less effective in the compensation of interharmonics. A frequency selective control system for a voltage controlled active filter connected to the power system through a multistage passive filter is described. A bank of second-order IIR digital filters with interharmonic tracking ability is employed for high-resolution spectral estimation and control. This approach is verified by simulation. It is shown for example that the active filter can compensate for supply interharmonics produced by a cycloconverter load. Different control strategies based on the selective control system are investigated and compared with an earlier strategy based on the detection of the total current distortion. By using individual detection and compensation of critical harmonics and interharmonics, hybrid power filters can be optimised to satisfy the distortion limits with the lowest active filter rating and switching frequency.

Constrained FIR filter design by the method of vector space projections

Abstract: A new technique for designing linear and arbitrary-phase finite-impulse response (FIR) filters with various types of constraints is proposed. The approach is based on the method of vector space projections. We describe the constraint sets and their associated projections that capture the properties of the desired filters. In filter design, as in many other engineering problems, one is primarily interested in meeting design constraints, i.e., finding a feasible solution, not necessarily an optimum one. Vector space projection methods are well-suited for this purpose. We furnish numerous examples of FIR filter design by vector space projections, including the important and difficult arbitrary phase/magnitude problem. Examples that demonstrate the advantages and flexibility of this method over other known methods are furnished.

Design and properties of polynomial-based fractional delay filters

Abstract: Design and properties of polynomial-based FIR filters with adjustable fractional delay are studied. Given the passband region, the filter parameters are optimized to minimize in the passband the worst-case phase delay deviation from the desired value (the maximum deviation for fractional delays between zero and unity) subject to a given worst-case amplitude deviation from unity in the passband. It is shown that the filter with fractional delay equal to one-half determines the lower limit for the achievable amplitude distortion. Because the filters under consideration are polynomial-based, they can be efficiently implemented using the modified Farrow structure introduced by the authors. The main benefit of the proposed synthesis scheme lies in the fact that it results in the structure where the linear-phase branch filters of the modified Farrow structure are fixed and only one parameter controls the fractional delay.