Showing papers on "Prototype filter published in 1984"

High-frequency CMOS continuous-time filters

Abstract: Fully integrated, high-frequency continuous-time filters can be realized in MOS technology using a frequency-locking approach to stabilize the time constants. A simple, fully differential integrator, optimized for phase-error cancellation, forms the basic element; a complete filter consists of intercoupled integrators. The center frequency of the filter is locked to an external reference frequency by a phase-locked loop. A prototype sixth-order bandpass filter with a center frequency of 500 kHz dissipates 55 mW and occupies 4 mm/SUP 2/ in a 6-/spl mu/m CMOS technology.

Median filtering by threshold decomposition

Abstract: Median filters are a special class of ranked order filters used for smoothing signals Repeated application of the filter on a quantized signal of finite length ultimately results in a sequence, termed a root signal, which is invariant to further passes of the median filter In this paper, it is shown that median filtering an arbitrary level signal to its root is equivalent to decomposing the signal into binary signals, filtering each binary signal to a root with a binary median filter, and then reversing the decomposition This equivalence allows problems in the analysis and the implementation of median filters for arbitrary level signals to be reduced to the equivalent problems for binary signals Since the effects of median filters on binary signals are well understood, this technique is a powerful new tool

Multirate filter designs using comb filters

Abstract: Results on multistage multirate digital filter design indicate most of the stages can be designed to control aliasing with only slight regard for the passband which is controlled by a single stage compensator. Because of this, the aliasing controlling stages can be made very simple. This paper considers comb filter structures for decimators and interpolators in multistage structures. Design procedures are developed and examples shown that have a very low multiplication rate, very few filter coefficients, low storage requirements, and a simple structure.

A History of Microwave Filter Research, Design, and Development

Abstract: An account of the development of microwave filters is surveyed, commencing from 1937. Much of the foundation of modem filter theory and practice took place during the period of World War II and the years immediately following, especially by such pioneers as the late P. I. Richards, whose subsequent career is briefly described. Filter topics discussed include low-pass, bandpass, high-pass, and multiplexers constructed in a variety of media such as waveguide, coaxial line, microstrip, and stripline, as well as dielectric resonators. All types of filter characteristics are surveyed, such as Chebyshev, elliptic and pseudo-elliptic function, Achieser-Zolotarev, and a variety of generalized designs, including linear phase.

A CMOS narrow-band signaling filter with Q reduction

Abstract: A circuit for extracting signaling information from its associated voice channel in frequency-division multiplexing has been integrated in metal gate CMOS technology. It uses a frequency translation technique that effectively enhances the Q of the filter to >100. It contains a programmable prefilter, a programmable modulator, and a highly selective bandpass filter. The frequency translation was accomplished through the use of a balanced modulator, which is well suited to a switched-capacitor realization. Design considerations that must be addressed in choosing an optimum architecture and a method of analyzing the ill effects of aliasing in a sampled data modulator were also presented. The technique described here is applicable to the design of a filter with an effective Q of much greater than 100.

Broad-Band Millimeter-Wave E-Plane Bandpass Filters (Short Papers)

Abstract: An accurate method to obtain starting estimates for an E-plane bandpass filter CAD program recently developed by Shih, Itoh, and Bui is presented. Results agree very well with exact values for filter design with relative bandwidths exceeding 10 percent at W-band and D-band and 20 percent at lower frequencies.

Computationally efficient QMF filter banks

Abstract: This paper introduces a computationally efficient technique for splitting a signal into N equally spaced sub-bands subsampled by 1/N and for near perfectly reconstructing the original signal from the sub-band signals. This technique is based on a multirate approach where some operations are nested to decrease the computation load. Simulation results show that the performances are comparable to that of conventional quadrature mirror filters, but with a very significant reduction in computational complexity.

Fast block data processing via a new IIR digital filter structure

Abstract: A new structure for realizing IIR digital filters is introduced based on the idea of processing sequences by blocks. It is shown that this structure exhibits high inherent parallelism that is ideally suited for VLSI implementation or multimicroprocessor systems. This enables high-speed processing with the number of multiplies and additions per output sample much less than those of the block-state or canonical filter realizations. The roundoff noise level in the output of the new filter structure is derived and compared to the noise levels of the block-state and canonical forms. Further, it is shown that the new filter structure will present no scaling problems if the canonical filter is scaled. Finally, the extension of the new filter structure to the realization of periodically time-varying digital filters is also presented.

Design of three- dimensional recursive digital filters

Abstract: Three types of three-dimensional (3-D) recursive digital filters are first defined under different radial symmetry constraints in the 3-D coordinate axes: the symmetrical filter, the nonsymmetrical filters I and II. A design technique is then outlined for these 3-D recursive digital filters whose magnitude responses can be decomposed into several cubic pass- and stopbands. The filter designed by the present approach can be realized by cascading and paralleling of the well-known one-dimensional (1-D) component transfer functions so that the stability test is simple and the filter can be implemented easily. Three examples are included to illustrate the design procedure for each type of 3-D filter.

A new structure for narrow transition band, lowpass digital filter design

Abstract: In this paper, a new class of lowpass linear phase FIR filters is introduced. It is shown that lowpass filters with narrow transition bands can be realized efficiently by a structured form composed mainly of a few small FIR filters. The modular structure is suited for an implementation by a fast short convolution algorithm or a few single-chip filter IC's. A design procedure is considered in some detail and illustrated by an example. The properties and performance of the filter are discussed by analysis as well as design results. A brief discussion on its implementations concludes the paper.

E-Plane Integrated Circuit Filters with Improved Stopband Attenuation (Short Papers)

Abstract: Improved stopband attenuation is achieved by thick strips, by reduced waveguide sidewall dimensions, and by double planar integrated circuits. In contrast to thick strips which may cause high passband insertion losses and filters with reduced waveguide dimensions which require additional tapers, double planar E-plane integrated circuit filters combine the advantages of low costs, high stopband, and low passband insertion losses. Computer-aided design of a four-resonator Ka -band double metal insert filter achieves a calculated stopband attenuation between 40 and 60 GHz of more than 50 dB, the calculated minimum passband insertion loss is 0.43 dB (measured 1.8 dB). Higher order mode excitation and finite thicknesses of the inserts are included in the calculations.

Novel Lowpass Harmonic Filters for Satellite Application

Abstract: A new class of Iowloss spurious-free lowpass filters in ridged waveguide have been developed for space application. These filters are currently being incorporated for INTELSAT VI at 4 GHz and SATCOM K satellites at 12 GHz and will likely replace the present generation of Zolotarev stepped-impedance or waffle-iron filter networks for future spacecraft.

On the design of optimal state-space realizations of second-order digital filters

Abstract: Simple design equations are derived for optimal (minimum roundoff noise) state-space realizations of second-order digital filter sections with complex poles. These relations permit easy computation of filter coefficients and unit noise gain directly from the filter transfer function. New parameters are identified that are easily computed from the transfer function, are invariant under certain frequency-scaling transformations, and which can be used to simply describe all of the design variables of optimal second-order filters, including state covariance matrix, unit noise matrix and second-order modes. The design relations are illustrated by computing the unit noise gains and eigenvalue sensitivities of optimal parallel realizations of Chebyshev lowpass filters.

High resolution noncollinear acoustooptic filters with variable passband characteristics: design

Abstract: A generalized method for designing a high resolution acoustooptic filter with variable passband characteristics is described and experimentally verified in crystalline quartz. The optical passband of this filter configuration is made insensitive to acoustic divergence by canceling the wave vector mismatch caused by acoustic divergence by the similar effect introduced by the anisotropy of the acoustic velocity within the acceptance angle. About 0.4-nm half-power bandwidth with an external half-angular aperture of ~3° was obtained at 488 nm in a quartz filter. By changing the effective interaction length from 47 to 6 mm the passband was varied approximately from 0.4 to 3.5 nm. The possibilities of finding suitable filter orientations in Tl3AsSe3 and TeO2 are also discussed.

Image Decimation and Interpolation Techniques Based on Frequency Domain Analysis

Abstract: A scheme for a spatial domain image data preprocessing decimation and postprocessing interpolation is presented. The scheme is implemented by appropriate FIR digital filters. Frequency and patial domain specifications are discussed in the design of the corresponding digital filters. Fast approximation techniques in the spatial domain are presented.

A digital linear filter for resistivity sounding with a generalized electrode array

Abstract: This paper presents a digital linear filter which maps composite resistivity transforms to apparent resistivities for any four—electrode array over a horizontally layered earth. A filter is provided for each of three sampling rates; the choice of filter will depend on resistivity contrasts and computational facilities. Two methods of filter design are compared. The Wiener-Hopf least-squares method is preferable for low sampling rate filters. The Fourier transform method is more successful in producing a filter with a high sampling rate which can handle resistivity contrasts of 100 000: 1.

On maximally-flat linear-phase FIR filters

Abstract: An implementation for maximally-flat FIR filters is proposed that requires a much smaller number of multiplications than a direct form structure. The values of the multiplier coefficients in the implementation are conveniently small, and do not span a huge dynamic range, unlike in a direct form implementation.

On the Design of FIR Filters with Powers-of-Two Coefficients

Abstract: FIR filters with powers-of-two coefficients are attractive for cost-effective implementations. The performance of one such structure, the difference routing digital filter [8], is discussed. Using an SNR criterion, an optimal algorithm to select the value of the filter coefficients is presented. Results indicate that a 2-3 dB improvement in the SNR can be obtained with this new approach. In addition, the study gives some insight into the relationship between the filter sampling rate, the number of coefficients, and the size of the coefficient alphabet. In particular, it is seen that a tradeoff between the filter sampling rate and the size of the coefficient alphabet exists.

Linear phase bandpass digital filters with variable cutoff frequencies

Abstract: A low-pass-to-bandpass transformation for linear phase FIR filters is discussed. The transformed bandpass filter is implemented in a network structure in which the cutoff frequencies are controlled through two parameters. The range through which the cutoff frequencies of the transformed filter can be varied depends on the cutoff frequency and the stopband edge frequency of the prototype low-pass filter. For a given prototype filter, this range is obtained from a set of simple graphs.

Plasma-Dielectric Sandwich Structure Used as a Tunable Bandpass Microwave Filter (Short Paper)

Abstract: A plasma-dielectric sandwich structure used as a tunable bandpass filter in a microwave spectrum is investigated in detail. The unique characteristics of this filter are that the center frequency of its passband and its bandwidth can be tuned electrically by varying the electron density of the plasma, which in turn can be adjusted by a voltage applied across the plasma electrodes. First, the principle in establishing the filtering effect is briefly discussed physically with an aim of suggesting a practical structure for theoretical analysis. A conventionsal multilayer theory is then employed to analyze this plasma-dielectric structure, and an optimization technique called the simplex method is used to find the center frequency. Both cases of having the TE/sub10/ dominant mode in a rectangular waveguide and the TEM mode in an unbounded structure are studied. Finally, included are the computed results for characterizing the filter such as reflection coefficients, center frequencies, bandwidths, quality factors, and Iossy effects, etc.

Filter for determining target data

Abstract: In this filter, optimum filter coefficients are determined from widely scattered measurement values, for example bearings, in an iterative signal processing circuit. The filter coefficients and the measurement values are used for driving an accumulation circuit which determines correction values for an initial estimate of the target data. According to the invention, the filter is improved by additional multiplication circuits for determining the coefficients for the dynamic target data, that is to say the velocity components. Such filters are used in solving navigation tasks, particularly the passive determination of position and motion data of target vehicles.

Constant Z bandswitched input filter

Abstract: A constant impedance (Z) bandswitched input filter for use in a wideband signal receiver includes a low pass filter, a high pass filter and a bandpass filter for reducing intermodulation distortion as well as for providing a flat input impedance characteristic. The bandpass filter resonates at the crossover frequency between the low and high pass filters for minimizing insertion loss while maintaining a constant termination impedance across the entire input signal bandwidth to reduce the input standing wave ratio (VSWR). Switching means are provided for coupling the high and low pass filters as well as the bandpass filter in circuit depending upon the frequency band tuned to. The constant Z bandswitched input filter is particularly adapted for use in a wide band cable television (CATV) system for substantially reducing intermodulation distortion and signal reflections arising from impedance mismatches, but has application in any cable operated multichannel communications system.

Digital filters with equiripple magnitude and group delay

Abstract: This paper introduces a class of recursive digital filters having equiripple behavior in both the magnitude and group delay responses. The filters consist of an all-pole IIR component cascaded with a linear phase FIR component. The IIR component is synthesized so that its group delay exhibits an equiripple variation in the passband, whereas the FIR component is used to obtain the desired equiripple nature for the amplitude response in both the passband and stopband(s). An iterative procedure is presented for optimizing the ripple in the group delay and the order of the IIR part in such a way that the overall multiplication rate attains its minimum. Examples show that standard simultaneous amplitude and phase optimization methods only slightly change the results obtained using this method. The new method is straightforward to implement and avoids the problems of guessing good initial values and of premature termination. Several examples show that the new filters require significantly fewer multipliers in narrow-band applications than equivalent FIR and delay equalized elliptic designs at the expense of a negligible variation in the group delay.

MOS-VLSI pipelined digital filters for video applications

Abstract: The interactions between digital filter design and VLSI design methodology are discussed. The constraints imposed by the MOS-architecture are discussed, an appropriate filter structure is proposed. The mapping of this structure to a VLSI-realization is shown for intermediate and high sample rates. Design examples for FIR and IIR filters for video applications and lowpass filters for decimation and interpolation are given.

Spatial-domain design of a class of two-dimensional recursive digital filters

Abstract: This paper presents a technique for designing a class of two-dimensional (2-D) recursive digital filters, and also proposes a new state-space model for the 2-D recursive digital filters. The technique is applicable to the design of both quarter-plane causal filters and 2-D weakly causal filters. The filter is designed in terms of a canonic form state-space model, as well as a transfer function. The design is based upon minimization of the sum of squared differences between the desired and actual 2-D impulse responses over a finite interval. The test of stability for such filters is easy.

Exact synthesis of bandpass switched- capacitor LDI ladder filters

Abstract: Exact design techniques are given for the design of leapfrog switched-capacitor bandpass filters using lossless discrete integrator (LDI)-type building blocks. No assumptions are made regarding the sampling rate except that of satisfying the sampling theorem, and only strays-insensitive circuits are employed. The design techniques derive from a prototype filter employing unit elements. The filters have no lumped counterpart, and cannot be obtained from lumped filters by a transformation or otherwise. They also retain the optimum sensitivity properties of the corresponding passive distributed filters.

New method for generating two-variable VSHPs and its application in the design of two-dimensional recursive digital filters with prescribed magnitude and constant group delay responses

Abstract: In the paper a method is presented for the design of 2-D stable recursive digital filters satisfying prescribed magnitude and constant group delay responses. This technique uses the properties of positive definite matrices and their application in generating 2-variable Very Strictly Hurwitz Polynomials (VSHPs), which will be assigned to the denominator of a 2-D analogue reference filter. Bilinear transformations are then applied to the transfer function of the derived 2-D analogue reference filter to obtain the discrete version of the 2-D filter. Parameters of the discrete 2-D filter can be used as the variables of optimisation to minimise the leastmean-square error between the desired and designed magnitude and group delay responses of the filter. To show the usefulness of the technique, an example is given.

Filter for data processing

Abstract: Improved Filter for Data Processing Abstract An imaging method and apparatus having a new and improved data filter. In one application of the inven-tion computed tomography number inaccuracies are avoided by use of a new filter function derived from discrete points of a truncated spatial domain convolution filter. The points from the truncated convolution filter are fourier transformed to yield a ramp filter with ripple in the spatial frequency domain. Data from a CT scan is filtered with this new filter function and back projected to produce images that do not exhibit CT number inaccuracies.