Showing papers on "Prototype filter published in 1978"

Adaptive filtering in the frequency domain

Abstract: Adaptive filtering in the frequency domain can be accomplished by Fourier transformation of the input signal and independent weighting of the contents of each frequency bin. The frequency-domain filter performs similarly to a conventional adaptive transversal filter but promises a significant reduction in computation when the number of weights equals or exceeds 16.

MOS switched capacitor ladder filters

Abstract: A new technique for designing precision, fully integrated, high-order filters using standard MOS technology is described. Switched capacitor integrators have been used to realize long time constants in small areas, and by interconnecting these integrators in a `leapfrog' configuration, monolithic high-order filters have been implemented with transfer functions that are very insensitive to component variations. Experimental results are presented for an NMOS fifth-order Chebyshev low-pass ladder filter with 0.1-dB passband ripple, a cutoff frequency of 3.4 kHz when clocked at 128 kHz, and a dynamic range of 83 dB. An efficient method for implementing transmission zeros is also presented, along with a complete design example, and additional experimental results for a third-order elliptic low-pass ladder filter which achieved 90-dB dynamic range, with a total power dissipation of 18 mW in a die area of 4400 mil/SUP 2/.

A class of all-zero lattice digital filters: Properties and applications

Abstract: A class of minimum- or maximum-phase all-zero lattice digital filters, based on the two-multiplier lattice of Itakura and Saito, is developed. Different lattice forms with different numbers of multipliers are derived, including two one-multiplier forms. Many of the properties of these lattice filters are given, including the important orthogonalization and decoupling properties of successive stages in optimal inverse filtering of signals. These properties lead to important applications in the areas of adaptive linear prediction and adaptive Wiener filtering. As a specific example, the design of a new fast start-up equalizer is presented.

Use of the Butterworth low-pass filter for oceanographic data

Abstract: The characteristics of the Butterworth low-pass filter are well known in electrical engineering. Here we discuss its use for oceanographic records and compare its characteristics with other low-pass filters now in use: the cosine-Lanczos filter, the Gaussian filter, and the ideal filter. The Butterworth filter is recursive, i.e., past values of the output are used as input, so a phase shift is introduced unless the data are filtered forward and backward through the same filter. When this is done, the filtered signal differs only slightly from that of other low-pass filters. Because the Butterworth filter uses fewer multiplicative constants for the same effect, there is a reduction in computer time over other low-pass filters; the difference becomes more pronounced as more data points are used.

Stability of general two-dimensional recursive digital filters

Abstract: Two-dimensional recursive filters are defined from a different point of view. A general stability preserving mapping theorem is presented which allows most recursive filters of a particular type to be mapped into any other type of recursive filter. In particular, any type of filter can be mapped into a first-quadrant filter. This mapping is used to prove a number of general stability theorems. Among these is a theorem which relates the stability of any digital filter to its two-dimensional phase function. Furthermore, other stability theorems which are valid for any type of recursive filter are presented. Finally, a number of practical stability tests are developed including one which requires the testing of only several one-dimensional polynomial root distributions with respect to the unit circle.

Block implementation of recursive digital filters--New structures and properties

Abstract: Several new structures for the block implementation of HilR digital filters are proposed. The relation between the pole locations of the block structure to that of the original scalar transfer function is derived. A method to obtain the scalar transfer function from a given block structure is described.

Design of recursive digital filters with optimum magnitude and attenuation poles on the unit circle

Abstract: A class of infinite impulse response (IIR) digital filters with optimum magnitude in the Chebyshev sense, arbitrary attenuation in the passband and stopband, all zeros on the unit circle, and different order numerator and denominator is discussed. Several properties of low-pass filters of this type are described, such as the effect of an extra ripple in the passband and the minimum attainable passband ripple for a given order. An algorithm for the design of these filters is presented, which given the order of the filter, passband edge, stopband edge and passband ripple minimizes the stopband ripple. Alternatively, the stopband ripple can be fixed and the passband ripple minimized. This is done by working with the numerator and denominator separately. This algorithm is fast compared to other existing design procedures. Several examples are presented and compared with the classical elliptic filters. Filters are described which meet the same tolerance scheme as an elliptic filter with fewer multiplications.

Design of two-dimensional recursive digital filters with specified magnitude and group delay characteristics

Abstract: A technique is proposed for the design of two-dimensional (2-D) recursive filters with a response that best approximates, in the l_p sense, prescribed magnitude and group delay specifications. The filter stability is guaranteed through the use of a frequency transformation. The optimization technique used is that of Davidon-Fletcher and Powell. Several examples are given to illustrate the proposed algorithm.

A design technique for circularly symmetric low-pass filters

Abstract: The design of two-dimensional (2-D) circularly-symmetric low-pass digital filters by cascading several rotated filters (a rotated filter is defined to be one produced by rotating a one-dimensional (1-D) continuous filter into a two-dimensional continuous filter which is in turn bilinearly transformed into a two-dimensional digital filter) is a well-known and useful technique. An alternate approach which is an extension of the above technique is presented. This new method is based on a spectral transformation from the one-dimensional discrete domain into the two-dimensional discrete domain. This approach retains most of the advantages of the original technique while permitting design entirely in the discrete domain, yielding filters with better stability characteristics, and facilitating frequency response optimization via nonlinear programming.

Design of two-dimensional recursive digital filters

Abstract: The present paper develops a design technique for approximating nonseparable frequency characteristics by sums and products of separable transfer functions. This approximation is called the "piecewise separable" decomposition of the characteristic. In the design technique, the desired filter with half-plane symmetry (radial symmetry) is obtained by shifting a low-pass characteristic in the frequency domain, and by combining these shifted characteristics. Also the paper includes design approaches for the four-quadrant symmetry filters. Two examples illustrate the technique of the paper.

Computer-Aided Filter Alignment and Diagnosis

Abstract: The cavity resonant frequencies and coupling values of a wide range of bandpass filters, band-reject filters, and equalizers have been determined in situ by computer-adjusting analytic models to fit the scattering parameters measured on an automatic network analyzer. A higher order mode elliptic filter, a dual-mode quasi-elliptic filter, and a dual-mode band-reject filter are presented as examples. The general relationships between mechanical dimensions and circuit parameters are discussed. The circuit adjustment procedure is outlined, and equations for the sensitivity coefficients of several element types are tabulated.

Aliasing error in the design of multirate filters

Abstract: A narrow-band filter is inherently of high order, and requires a high computation rate if implemented directly. A multirate implementation can offer the advantage of much reduced computation per output sample. This paper derives an expression for the system error of such an implementation. This error consists of two components, one due to the approximation of the desired filtering characteristics and the other due to aliasing. An expression for the fixed point multiplication roundoff error is also derived. Design rules are suggested which fix the aliasing error at a specified level. Examples are given.

Fully-integrated high-order NMOS sampled-data ladder filters

Abstract: This paper will disclose an approach for implementing NMOS sampled-data recursive filters by using switched-capacitor integrators in an active ladder configuration. Experimental results for a fifth order Chebyshev 3400Hz low-pass filter with 0.1dB passband ripple will be presented.

On an adaptive algorithm for IIR filters

Abstract: The purpose of this communication is to discuss an IIR adaptive filter algorithm developed by Stearns [1], in terms of an example that appeared in a recent article [2]. The example concerns the approximation of a fixed second-order filter by a first-order adaptive filter, when subjected to a white noise input.

Design of signal flow graph (SFG) active filters

Abstract: A systematic procedure is presented for the design of active filters obtained as operational simulations of LC ladder prototypes. The method is based on the signal-flow graph (SFG) approach, but allows one to obtain the final circuit without ever considering signal-flow graphs. Practical design problems, namely, scaling for maximum dynamic range, stabilizing the reciprocator amplifiers, predistorting the LC prototype to compensate for the parasitic reactances introduced by reciprocators, eliminating the inherent dc offsets, and tuning are solved and illustrated by examples. Complete design and experimental results are given for a twelfth-order bandpass channel bank filter.

Active R ladders: High frequency, high order, low sensitivity active R filters without external capacitors

Abstract: Active R filter techniques which make use of the pole of an operational amplifier to produce the state variables without the need for inductors or external capacitors may be employed to simulate all of the elements of both singly and doubly terminated reactance ladders. Although the design techniques are very simple and follow directly from passive synthesis techniques, the resulting filters offer high-order circuits with low sensitivity. However, the primary advantage of these active R filters is the ability to design filters which operate in a considerably higher frequency range than obtainable with standard active RC designs. While still primarily of research interest due to dynamic range problems and temperature sensitivity problems, active R ladders may be adequately compensated to allow many applications in specialized signal processing environments.

Computer-aided design of withdrawal-weighted SAW bandpass filters

Abstract: This paper reviews some of the motivation that has led to development of SAW bandpass filters, based on withdrawal-weighted designs. A computer-aided procedure for the synthesis of such filter described. Using a spectral-weighting transducer model which is valid at fundamental and harmonic frequencies, examples of withdrawal-weighted filters designed with a computer are presented.

Linear transformation active filters

Abstract: An approach is presented in this paper for the design of active filters from doubly terminated lossless ladder filters. The method relies-on-the-lnear transformation of port variables from the V-I domain to a new domain in which the filter is realized actively. The resulting active filters are referred to as linear transformation active (LTA) filters. The transformations are applied on an element-by-element basis thus producing a systematic and effective way of achieving new active structures while others like the leapfrog and the wave active filter structures appear as special cases. Examples are presented in the paper to show the efficiency of the method and the importance of the results.

Bandpass (bandstop) digital filter design routine.

Abstract: As a complement to the design methods for low pass digital filters previously published [Rev. Sci. Instrum. 48, 1447 (1977)], we present a description of a bandpass (or bandstop) digital filter design program, a demonstration of its use, and the fortran code.

Synthesis of acoustic-surface-wave-resonator filters using any of various coupling mechanisms

Abstract: Design of surface-wave resonator bandpass filters from lumped-element low-pass prototypes is treated by use of a generalized version of Cohn's direct-coupled filter theory. Equations are presented for straightforwud application of the method to the design of SAW resonator filters with acoustic-array couplings, transducer couplings, or multistrip couplings. To illustrate this technique, a four-resonator filter with a given Chebyshev response is set as an objective, and several designs were worked out for such a filter, each using different coupling arrangements. The responses for the various designs were computed, and though an met the given passband specifications, some are seen to have stronger stopband attenuation than others. Conclusions are drawn with regard to the range of application of the various types of couplings. The derivation of the equations needed for the design of acoustic-array and multistrip couplings is outlined in appendices.

Design of digital FIR filters with complex conjugate pulse responses

Abstract: Conventional linear phase finite impulse response digital filters have real-valued coefficients forming a symmetric or antisymmetric pulse response. Such filters have a frequency response with an even magnitude about 0 Hz. Odd-length filters with complex coefficients forming a complex conjugate symmetric pulse response also have a linear phase response but can have a magnitude response which is not even about 0 Hz. These filters have applications in single-sideband modulation systems and in processing in-phase and quadrature signals in sonar and radar. Only minor modifications are required in two FIR filter design computer programs (the Parks and McClellan Remez exchange algorithm and the Leon and McCallig constrained ripple algorithm computer programs) to allow the design of linear phase filters with complex coefficients.

Variable-cutoff two-dimensional lowpass f.i.r. digital filters

Abstract: A recently formulated transformation for implementing 1-dimensional variable-cutoff filters is extended to the design of 2-dimensional variable-cutoff lowpass filters, and it is shown that the cutoff frequencies along the two frequency axes can be independently controlled, each by one parameter. The filters designed with the 1st-order transformation have certain drawbacks, which are shown to be overcome with the 2nd-order transformation with proper constraints on the variable parameters.

Design of selective linear-phase filters with equiripple amplitude characteristics

Abstract: A simple numerical technique is described for the construction of a nonminimum phase transfer function with an optimum equiripple passband amplitude response and linear-phase characteristics. The linearphase behavior may be maintained over part of or over the entire passband by varying the number of transmission zeros at infinity. Increasing the number increases the selectivity of the filter at the expense of a deterioration in the phase performance towards the edge of the passband. Synthesis is performed using even- and odd-mode decomposition, and tables of element values are provided with graphical design information to enable the design engineer to choose the correct prototype to meet a given specification.

Weighting coefficients for certain maximally flat nonrecursive digital filters

Abstract: The weighting coefficients for maximally flat nonrecursive digital ruters have been derived for low-pass filters having equal passband and stopband widths. The solution is in closed form and can be readily evaluated even for large filter order. Asymptotically the coefficients of the finite series expansion converge to the Fourier series coefficients. Hilbert transformers and decimation filters are among the suggested applications for this form of filter.

Separation of NTSC Signals by Minimum Mean Square Error Filters and Adaptive Filters

Abstract: Two techniques for separating a composite NTSC signal into luminance and chrominance components are developed and compared. In the first technique, fixed filters, which are based upon minimum mean square error estimators, are designed. It is shown that, when samples from successive lines are used, these filters have a comb structure in the region of the frequency spectrum in which the luminance and chrominance signals overlap. In the second technique, the composite signal is filtered by several filters, and the outputs of the filters are selected dependent upon the local characteristics of the picture. Both recursive and nonrecursive filters are considered, the criterion for selecting between filters is investigated and the effect of delayed decisions is determined. The various filters are compared using subjective criterion and a number of quantitative criterion. The relationships between the quantitative and qualitative criterion are stated.

The design of optimal multirate bandpass and bandstop filters

Abstract: Narrow-band bandpass and bandstop filters are inherently of high order and require a large computation rate. A multirate filter using decimators and interpolators can be designed to have bandpass or bandstop characteristics, often with a much smaller computation rate. This paper develops rules for designing such a filter by placing constraints on the filter approximation error and the aliasing error. The question of admissible decimation factors is investigated in detail. A method to minimize the computation rate is described. Several examples are presented.

On the design of wave digital lattice filters with short coefficient word lengths and optimal dynamic range

Abstract: Wave digital lattice filters require, in general, fewer multipliers than other digital realizations and have excellent passband sensitivity properties. Because of the variety of solutions which are possible for the realization of the lattice reactances, these filters can be designed with simple multiplier coefficients in spite of the high sensitivity in the stopband. The filter structure which offers the optimal dynamic range is determined by means of the equivalences between parallel and series adaptors and by means of scaling with coefficients equal to powers of two. This is illustrated by some specific examples.

Fully integrated analog filters using bipolar-JFET technology [active fifth order Chebyshev low-pass realisation]

Abstract: A new approach for realizing high-order analog filters which can be fully integrated using a compatible bipolar and ion-implanted JFET process is described. This approach is based on the recognition that what is really needed is a long time constant monolithic integrator which can be effectively realized in a small silicon area. These integrators have been designed, fabricated, and used in a `leapfrog' or active ladder configuration to realize a fifth-order 8 kHz Chebyshev low-pass filter with 0.1 dB passband ripple. No external trimming operations and no anti-aliasing prefilter are required.

An Odd Order Elliptic Function Narrow-Bandpass Microwave Filter

Abstract: Multiple coupled high Q cavities can be used to generate even order elliptic function bandpass filter responses. This paper describes the design of odd order elliptic function bandpass filters using a minimum number of cavities connected by simple and resonant coupling elements. Experimental results of a 3-pole, 20-MHz bandpass waveguide cavity filter centered at 3890 MHz correlate well with theory.