Showing papers on "Prototype filter published in 1992"

A filter bank for the directional decomposition of images: theory and design

Abstract: The authors introduce a directionally oriented 2-D filter bank with the property that the individual channels may be critically sampled without loss of information. The passband regions of the component filters are wedge-shaped and thus provide directional information. It is shown that these filter bank outputs may be maximally decimated to achieve a minimum sample representation in a way that permits the original signal to be exactly reconstructed. The authors discuss the theory for directional decomposition and reconstruction. In addition, implementation issues are addressed where realizations based on both recursive and nonrecursive filters are considered. >

A CMOS transconductance-C filter technique for very high frequencies

Abstract: CMOS circuits for integrated analog filters at very high frequencies, based on transconductance-C integrators, are presented. First a differential transconductance element based on CMOS inverters is described. With this circuit a linear, tunable integrator for very-high-frequency integrated filters can be made. This integrator has good linearity properties and nondominant poles in the gigahertz range owing to the absence of internal nodes. The integrator has a tunable DC gain, resulting in a controllable integrator quality factor. Experimental results of a VHF CMOS transconductance-C low-pass filter realized in a 3- mu m CMOS process are given. Both the cutoff frequency and the quality factors can be tuned. The cutoff frequency was tuned from 22 to 98 MHz and the measured filter response is very close to the ideal response of the passive prototype filter. Furthermore, a novel circuit for automatically tuning the quality factors of integrated filters built with these transconductors is described. >

Cosine-modulated FIR filter banks satisfying perfect reconstruction

Abstract: The authors obtain a necessary and sufficient condition on the 2M (M=number of channels) polyphase components of a linear-phase prototype filter of length N=2 mM (where m=an arbitrary positive integer), such that the polyphase component matrix of the modulated filter is lossless. The losslessness of the polyphase component matrix, in turn, is sufficient to ensure that the analysis/synthesis system satisfies perfect reconstruction (PR). Using this result, a novel design procedure is presented based on the two-channel lossless lattice. This enables the design of a large class of FIR (finite impulse response)-PR filter banks, and includes the N=2M case. It is shown that this approach requires fewer parameters to be optimized than in the pseudo-QMF (quadrature mirror filter) designs and in the lossless lattice based PR-QMF designs (for equal length filters in the three designs). This advantage becomes significant when designing long filters for large M. The design procedure and its other advantages are described in detail. Design examples and comparisons are included. >

Time-domain filter bank analysis: a new design theory

Abstract: The authors present a new time-domain approach for the analysis and design of a broad class of general analysis/synthesis systems based on M-band filter banks. They derive a set of time-domain conditions for reconstruction which can be used directly in a filter bank design procedure. The general and unrestricted nature of this framework allows for the design of many useful banks. In addition to the complete derivation of the time-domain conditions, they also describe the associated filter bank design procedure and a number of design examples are included. >

Quadratic filters for signal processing

Abstract: Polynomial (or Volterra) filters are introduced, and the quadratic filters are presented as the simplest example of such filters. The principle aspects and properties of quadratic filters are derived in the framework of the discrete Volterra expansion. Fixed as well as adaptive filters are considered in one-dimensional and multidimensional environments. Such issues as design and efficient realizations are thoroughly addressed, and standard and advanced adaptation algorithms are presented. Several examples of signal processing applications requiring quadratic filters are discussed. >

Applications of simulated annealing for the design of special digital filters

Abstract: The authors describe the salient features of using a simulated annealing (SA) algorithm in the context of designing digital filters with coefficient values expressed as the sum of power of two. A procedure for linear phase digital filter design, using this algorithm, is presented and tested, yielding results as good as those for known optimal methods. The algorithm is then applied to the design of Nyquist filters, optimizing at the same time both frequency response and intersymbol interference, and to the design of cascade form finite-impulse-response (FIR) filters. The drawback of using SA is that the computation time is on the order of 1-2 h for each filter design, on the Sun 3/60. However, this was more than compensated by the versatility of the new algorithm, which can be used to design filters with multiple constraints. >

Development of low-loss band-pass filters using SAW resonators for portable telephones

Abstract: A bandpass filter using surface acoustic wave (SAW) resonators in a ladder circuit structure for portable telephone systems is reported. For filter design, a simulation tool is used to consider the effects of electrodes (their apertures, the number of paired elements, thickness, and bulk wave radiation). Filter input and output impedance conditions are designed by the resonator capacitance to match the line impedance. The insertion loss and stopband rejection values are traded off against each other and are controlled by the ratio of capacitances between the parallel arm and series arm resonators, 800-MHz and 1.9-GHz band filters mounted in 3.8 mm*3.8-mm*1.5-mm ceramic packages were fabricated. They are suitable for surface mount technology (SMT). Typical frequency response characteristics are 2.5-dB maximum insertion loss in the 25-MHz passband and a stopband rejection of 25 dB. >

A general class of current amplifier-based biquadratic filter circuits

Abstract: A general class of current amplifier-based biquadratic filter circuits capable of realizing arbitrary filter functions including the low-pass, high-pass, and bandpass transfer functions is presented. These realizations are derived from a class of well-known low sensitivity single amplifier biquadratic (SAB) filter circuits using the principle of adjoint networks. The salient features of the proposed circuits are that they are synthesized using the same procedure as their op-amp-based SAB circuit counterparts, and they possess the same sensitivities to component variations as the original SAB circuits. However, it is demonstrated experimentally that unlike op-amp-based SAB realizations whose effective operating bandwidth is much less than the unity-gain bandwidth of the op-amp, these current-based filter circuits are effective over the entire bandwidth of the current amplifier. >

High-linearity continuous-time filter in 5-V VLSI CMOS

Abstract: High-linearity self-tuning continuous-time filters, fabricated in a standard 1.6- mu m 5-V CMOS process, are presented. Frequency control is achieved using switchable arrays of highly linear double-polysilicon capacitors in an active RC filter structure, resulting in tunable filters with very low signal distortion. One filter, a Tow-Thomas biquad, exhibits dynamic range and signal linearity of typically 91 dB. Another smaller implementation, a Sallen and Key filter, attains >or=76 dB. Cutoff frequency response is maintained to an accuracy of around +or-5%. >

Narrow-band optical channel-dropping filter

Abstract: Waveguide couplers are combined with lambda /4 shifted distributed feedback (DFB) resonators to produce narrowband channel dropping filters. The bandwidth of the filter can be made much narrower than the stopband of the grating. It is possible to remove the spurious responses of the grating filter by appropriate dispersion characteristics for the coupled waveguides. However, in some practical applications it may not be necessary to do this, if all channels can be accommodated within half the grating bandwidth of the filters. >

Lagrange multiplier approaches to the design of two-channel perfect-reconstruction linear-phase FIR filter banks

Abstract: The authors present two approaches to the design of two-channel perfect-reconstruction linear-phase finite-impulse-response (FIR) filter banks. Both approaches analyze and design the impulse responses of the analysis filter bank directly. The synthesis filter bank is then obtained by simply changing the signs of odd-order coefficients in the analysis filter bank. The approach deals with unequal-length filter banks. By designing the lower length filters first, one can take advantage of the fact that the number of variables for designing the higher length filters is more than the number of perfect-reconstruction constraint equations. The second approach generalizes the first, and covers the design for all parts of linear phase perfect reconstruction constraint equations. >

Wide bandwidth bandpass filter comprising parallel connected piezoelectric resonators

Abstract: A plurality of piezoelectric resonators (10,32,37,57,62,66,79,88,93) are utilized to form a bandpass filter (31,56,78). The resonators (10,32,37,57,62,66,79,88,93) are connected in parallel to form a plurality of parallel paths between an input (43,73,81) and an output (47,74,82) of the filter (31,56,78). A predetermined number of the piezoelectric resonators (10,32,37,57,62,66,79,88,93) provide a phase shift of approximately 180 degrees. Each parallel path has a passband and center frequency that is displaced from the passband and center frequency of other paths. Consequently, the passband of each parallel path algebraically sums and creates a filter passband that is wider than the passband of each of the filter's individual parallel paths.

METEOR: a constraint-based FIR filter design program

Abstract: It is proposed to specify a filter only in terms of upper and lower limits on the response, find the shortest filter length which allows these constraints to be met, and then find a filter of that order which is farthest from the upper and lower constraint boundaries in a minimax sense. The simplex algorithm for linear programming is used to find a best linear-phase FIR filter of minimum length, as well as to find the minimum feasible length itself. The simplex algorithm, while much slower than exchange algorithms, also allows the incorporation of more general kinds of constraints, such as concavity constraints (which can be used to achieve very flat magnitude characteristics). Examples are given to illustrate how the proposed and common approaches differ, and how the proposed approach can be used to design filters with flat passbands, filters which meet point constraints, minimum phase filters, and bandpass filters with controlled transition band behavior. >

Modeling of thin film resonators and filters

Abstract: Thin-film piezoelectric resonators have been used in the synthesis of crystal filters at microwave frequencies and for oscillator control. These resonators may be modeled using equivalent circuits or analytical expressions derived from acoustic boundary value excitation problems. Results of the modeling are described in three forms: (1) impedance characteristics plotted versus frequency, (2) analytical expressions of impedance, and (3) lumped-element equivalent circuits useful for filter design and analysis. Two filter types are modeled: a simple ladder filter and a more complex stacked crystal filter using acoustically coupled resonators. >

Noise in active resonators and the available dynamic range

Abstract: Active resonators used to make bandpass filters are shown to suffer from a fundamental deterioration in available dynamic range with increasing Q, which is shown to arise from the dissipation in the transistors simulating inductance or performing an equivalent function. An active resonator with Q>1 may only attain a specified dynamic range with the use of a larger tuning capacitance than its passive counterpart, and with a consequent larger lower dissipation at a given frequency of operation. This poses a serious limitation on the integrated circuit realization of high-frequency filters with high-Q poles. >

Optimal multilayer filter design using real coded genetic algorithms

Abstract: A novel approach for designing optimal multilayer filters based on a real-coded genetic algorithm is presented. Given the total number of layers in the filter, as well as the electrical properties of the materials constituting each layer, the algorithm iteratively constructs multilayers whose frequency response closely matches a desired frequency response. In contrast to existing iterative techniques, this method does not require a preliminary design using classical techniques. Also, the design procedure is independent of the nature of the multilayer as well as the characteristics of the incident and substrate media. The algorithm is applied to the design of various lowpass and high-pass optical filters, operating between practical terminal conditions. The performance of the resulting designs matches or improves on that for filters that were synthesised using semiclassical techniques.

Thin film bulk acoustic wave filters for GPS

Abstract: The design and analysis of ladder filters are discussed, and reports on progress to date in the implementation of these devices for Global Positioning System (GPS) applications are summarized. Results are described for a two-dimensional plate wave analysis that illustrates the effects of resonator size on spurious resonances that degrade filter performance. Ladder filters in the series/shunt configuration are fabricated with 5-12 resonators on a common membrane of AlN supported by a silicon substrate. Preliminary experimental results show that the ladder filters have a clean out-of-band response with some spurious responses near the passband region. The filter insertion loss in the experimental devices requires improvement. >

Introduction to the design of transconductor-capacitator filters

Abstract: Preface. 1. Introduction. 2. Filter Topologies and Terminology. 3. Biquad Filters. 4. Gyrator Filters. 5. State-Variable Filters. 6. Dealing with Floating Capacitors. 7. The Non-Ideal Transconductor. Part I: Parasitic Capacitances and Mismatches. 8. The Non-Ideal Transconductor. Part II: Output Impedance. 9. The Non-Ideal Transconductor. Part III: Non-Linearity. 10. Tuning of Transconductors. 11. Design of the gm-C Integrator. 12. Design of a gm-C Filter. 13. Tuning of gm-C Filters. Index.

Fast filter bank (FFB)

Abstract: The sliding fast Fourier transform (FFT) filter bank has an exceedingly low complexity of one multiplication per channel per sample. However, its frequency selectivity and passband response are poor. It is shown that the sliding FFT filter bank is in fact a particular member of a new family of fast filter banks (FFBs). In the case of FFT, each cluster of butterflies can in fact be derived from a pair of complementary two-tap (i.e. first-order) prototype FIR filters. The poor selectivity and degraded passband response of the FFT filter bank is a direct consequence of the poor frequency response of the prototype first-order filter. It is shown that by increasing the order of the prototype filters, it is possible to implement a filter bank with arbitrarily good selectivity and flat passband response. The FFB retains the low-complexity feature of the FFT. Because of its very much improved frequency response characteristics, the FFB be suitable for use in many applications where the FFT filter bank is unsuitable. >

Design of linear-phase IIR filters via impulse-response gramians

Abstract: A new method for the design of a linear-phase infinite-impulse-response (IIR) filter is presented. It involves designing a finite-impulse-response (FIR) filter satisfying the given frequency response specifications and subsequently obtaining a significantly lower order IIR filter using model reduction based on impulse-response gramians. The general outline of the method and a brief overview of the existing linear-phase FIR filter design and model-reduction techniques are presented. The impulse-response gramian and the model-reduction algorithm used are presented. The method is illustrated by design examples and is compared with other methods for the design of linear-phase IIR filters using equalizers. >

Wideband beamforming using fan filter

Abstract: A novel approach to wideband beamforming using FIR (finite impulse response) fan filters is presented. The method is based on two-dimensional filtering for the outputs of a linear array of sensors. To beamform in the broadside of the array, a symmetrical 90 degrees /n filter is employed. The filter in which the angle of fan is more acute can form the narrower beam over the full band while the order of the filter becomes higher. To beamform in the direction along the array, an asymmetrical 45 degrees fan filter is used. As aliasing occurs in this beamforming, the band which is available is limited a little in width. A general implementation of the FIR fan filter beamformer is given as the parallel connection of one-dimensional FIR filters. >

Pipelined recursive filter with minimum order augmentation

Abstract: Pipelining is an efficient way for improving the average computation speed of an arithmetic processor. However, for an M-stage pipeline, the result of a given operation is available only M clock periods after initiating the computation. In a recursive filter, the computation of y(n) cannot be initiated before the computations of y(n-1) through y(n-N) are completed. H.B. Voelcker and E.E. Hartquist (1970) and P.M.Kogge and H.S. Stone (1973) independently devised augmentation techniques for resolving the dependence problem in the computation of y(n). However, the augmentation required to ensure stability may be excessively high, resulting in a very complex numerator realization. A technique which results in a minimum order augmentation is presented. The complexity of the resulting filter design is very much lower. Various pipelining architectures are presented. It is demonstrated by an example that when compared to the prototype filter, the augmented filter has a lower coefficient sensitivity and better roundoff noise performance. >

Pyramid processor integrated circuit

Abstract: An integrated circuit (IC) for implementing a variety of multiresolution filters in an image processor includes a programmable, symmetric, and separable two-dimensional filter (110). The input signal to the filter can be an input signal applied to the IC or a combination of two such signals. Circuitry in the IC may be programmed to imply pixel values around the edges of the two-dimensional image signals processed by the filter. The filter provides an output signal as well as each of the unfiltered signals from a tapped delay line of a filter that combines successive lines of the image. The IC also includes an arithmetic and logic unit in which the filtered output signal may be combined with an unfiltered input signal or one of the unfiltered tap signals.

Quadrature mirror filter banks and method

Abstract: M-channel pseudo-quadrature-mirror-filter (QMF) banks using a prototype filter having a linear-phase spectral-factor of a 2Mth band filter. The overall transfer function of the analysis filter/synthesis filter system is a delay, and the aliasing cancellation has all the significant aliasing terms canceled. Consequently, the aliasing level at the output of the pseudo-QMF banks is comparable to the stopband attenuation of the prototype filter, with the error at the output of the analysis filter/synthesis filter system approximately equal to the aliasing error at the level of the stopband attenuation. The pseudo-QMF banks have the stopband attenuation of the analysis filters and thus synthesis filters of -100 dB. The resulting reconstruction error is also on the order of -100 dB. Optimization of the pseudo-QMF banks by a quadratic-constrained least-squares formulation converges very fast as both a cost function and constraints are quadratic functions with respect to unknown parameters, providing a much higher stopband attenuation compared to previous filter banks.

Eigen-approach for designing FIR filters and all-pass phase equalizers with prescribed magnitude and phase response

Abstract: An effective eigenfilter approach is proposed for designing FIR filters with complex-valued frequency responses. By minimizing a quadratic measure of the error in the frequency band, an eigenvector of an appropriate matrix is computed to get the filter coefficients. The algorithm is easy and optimal in the least squares sense; it is used to design to major classes of FIR filters, including multiband filters, differentiators, Hilbert transformers, and all-pass phase. Several examples and comparisons to the existing linear programming methods are presented to demonstrate the flexibility and effectiveness of this approach. >

Method and apparatus for automatic tuning calibration of electronically tuned filters

Abstract: A method and apparatus for automatic tuning calibration of electronically tuned filters which comprises a programmable frequency generator for producing a calibration frequency signal, a filter for filtering the calibration frequency signal, a detector for producing a detector voltage, a processor for programming the frequency generator to specific test frequencies and for producing a stepped filter tuning voltage and storing the detector voltage in response to the stepped filter tuning voltage, and a converter for digital-to-analog conversion of the stepped filter tuning voltage. Calibration frequency signal versus tuning voltage responses are stored for a number of calibration iterations within the usable range of the filter and the resulting table can be used to determine the correct tuning voltage for the filter when operating at any frequency within the usable filter range.

Two's complement quantization in two-dimensional state-space digital filters

Abstract: Two-dimensional (2-D) state-space digital filters are investigated for stability with and without quantization. A sufficient condition is obtained for the stability of the linear Fornasini-Marchesini (1976) state-space model. The same model is then studied for stability when implemented using two's complement truncation quantization, and a sufficient condition for asymptotic stability of the nonlinear filter is obtained. In the process, a theorem is proved which gives a sufficient condition for the stability of a one-dimensional (1-D) state-space digital filter under the same type of quantization. >

A 10 GHz thin film lumped element high temperature superconductor filter

Abstract: A narrowband thin-film lumped-element filter centered at 10 GHz has been fabricated using thalium-based high-temperature superconductor (HTS) technology. This filter does not suffer from the undesired spurious responses seen in thin-film distributed filters using HTS technology. The measured filter has 2.5-dB insertion loss at band center and 3% bandwidth and is within 50 MHz of the desired center frequency. Measurements were made to confirm the broad spurious free stopbands from 1 GHz to 21 GHz. Because this filter does not generate spurious modes in the substrate, it may be possible to put several filters on the same substrate in microwave systems applications. >

A quadratic-constrained least-squares approach to the design of digital filter banks

Abstract: The author formulates the filter bank design problem as a quadratic-constrained least-square minimization problem. The solution of the minimization problem converges very fast since the cost function and the constraints are quadratic functions with respect to the unknown parameters. The cosine-modulated and the two-channel linear-phase filter banks are designed using the proposed formulation. Compared to other design methods, the proposed technique yields PR (perfect reconstruction) filter banks with much higher stopband attenuation. The filter designed using the new approximation could be used as an initialization filter in a conventional PR filter bank design. >

A class of generalized cosine-modulated filter bank

Abstract: It is well known that FIR (finite impulse response) filter banks which satisfy the perfect reconstruction (PR) property can be obtained by cosine modulation of a linear-phase prototype filter of length N=2mM, where M is the number of channels. Moreover, the overall delay of this system is (2mM-1) samples. The author presents a PR cosine-modulated filter bank in which its overall delay is (2( alpha +1)M-1) samples, where alpha is a positive integer in the range 0 >