Showing papers on "Prototype filter published in 1975"
TL;DR: It is demonstrated that phase accuracy is extremely important in image processing filters and the hope is that more work will be done on the development of filter design techniques which use phase as well as magnitude specifications.
Abstract: We demonstrate that phase accuracy is extremely important in image processing filters and express the hope that more work will be done on the development of filter design techniques which use phase as well as magnitude specifications.
174 citations
TL;DR: In this article, it is shown that for wave digital filters, the earlier concept of pseudopower leads to a function called stored pseudo-power, from which a simple criterion guaranteeing absence of parasitic oscillations can be derived.
Abstract: Parasitic oscillations can occur in digital filters due to the granularity of the signal and to overflow. It is shown that for wave digital filters, the earlier concept of pseudopower leads to a function called stored pseudopower, from which a simple criterion guaranteeing absence of parasitic oscillations can be derived. For fixed-point two's-complement arithmetic, this criterion can be taken into account by particularly simple requirements for the adaptor output signals. A special type of calculus is developed which makes it possible to derive the corresponding simple requirements for the chopping operations at the various stages of the signal processing in the adaptors. The method is extended to cover scaling.
141 citations
TL;DR: In this paper, it is shown how, using the techniques of decimation and interpolation, a desired narrow-band filter can be realized with a greatly reduced number of multiplications per second in the realization over standard direct form implementations.
Abstract: In an earlier paper Crochiere and Rabiner [1] discuss the theory of using finite impulse response (FIR) digital filters for signal decimation, interpolation, and filtering. In this paper we expand on the ideas presented in the earlier paper on implementing narrow-band designs efficiently. It is shown how, using the techniques of decimation and interpolation, a desired narrow-band filter can be realized with a greatly reduced number of multiplications per second in the realization over standard direct form implementations. Further, it is shown that the proposed implementation can have less roundoff noise and less severe coefficient sensitivity problems than a standard direct form implementation. Several examples are presented to illustrate the applicability of this implementation to practical design problems.
109 citations
TL;DR: In this article, the spectral response characteristics of optical-waveguide filters were derived from coupled-mode formalism, and the functional dependence of spatial-perturbation period on the distance along the direction of wave propagation in the waveguide filter was derived.
Abstract: Analytical formulas for the synthesis of optical-waveguide filters having arbitrary spectral-response characteristics are derived from coupled-mode formalism. Use of these general formulas is illustrated by design of several filters, one of which is a linear power discriminator. The synthesis yields the functional dependence of spatial-perturbation period on the distance along the direction of wave propagation in the waveguide filter. The coupled-mode equations for the functional perturbation forms as determined by the synthesis process were solved numerically to find the actual response characteristics of the filter designs. Excellent agreement was found between the desired characteristics and those of the synthesized filters.
102 citations
TL;DR: Theoretical analysis of an acousto-optic filter using noncollinear interaction is presented in this article, where various characteristics of the filter, including tuning curve, resolution, angular aperture and deflection angle, are determined.
Abstract: Theoretical analysis of an acousto-optic filter using noncollinear interaction is presented. The various characteristics of the filter, including tuning curve, resolution, angular aperture and deflection angle, are determined. The theoretical calculations are in good agreement with the measured results of a TeO2 filter.
56 citations
TL;DR: In this article, the authors showed that a magneto-optical filter with a very narrow passband (less than 30mA) and a very high transmission (up to nearly 100% apart from losses arising from the glass cell, lenses and polarizers) is possible.
Abstract: Transmission curves and theoretical calculi of the magneto-optical filter, designed and built by the authors, are shown together with some observed transmission spectra. At present the filter has a total halfwidth of ≈80mA; and the maximum transmission is 25%. From the analysis of the theoretical curves and from the observed spectra, we deduced the possibility of making up a filter with a very narrow passband (less than 30mA) and a very high transmission (up to nearly 100% apart from losses arising from the glass cell, lenses and polarizers).
55 citations
TL;DR: In this paper, the frequency weighted least-square design of finiteduration filters, in one and two dimensions, continuous and discrete, is considered and some new theoretical results and some practical design techniques for conventional and unconventional filters are presented.
Abstract: The frequency weighted least-square design of finiteduration filters, in one and two dimensions, continuous and discrete is considered. Some new theoretical results and some practical design techniques for conventional and unconventional filters are presented. In some cases optimum discrete filters can be found conveniently by matrix inversion. In many cases a simple, iterative approximation technique using FFT can be used to carry out the design or to adjust the frequency response of filters.
48 citations
TL;DR: In this paper, a method for the synthesis of active filters based on processing of wave quantities is presented and some experimental results confirm the feasibility of the principle and possibilities for practical implementation are shown.
Abstract: Inductorless active filters which are derived from double terminated classical reactance filters, such as gyrator-capacitor filters and filters using the FDNR concept, are known to exhibit low sensitivity. Stimulated by the ideas underlying the method of wave digital filters the attempt has been made to establish a concept for the synthesis of active filters which is based on processing of wave quantities. In this paper the method leading to this new kind of active filters is presented and possibilities for practical implementation are shown. Some experimental results confirm the feasibility of the principle.
46 citations
[...]
TL;DR: A method is described and implemented for the derivation of active RC filters from analogue passive filters of the lossless ladder doubly terminated kind using scattering-parameter formulation.
Abstract: A method is described and implemented for the derivation of active RC filters from analogue passive filters of the lossless ladder doubly terminated kind. The method is based on scattering-parameter formulation and the active RC filters thus derived are referred to as wave active filters.
31 citations
TL;DR: This paper presents a technique for achieving flat composite response using linear-phase fir digital filters based on some special properties of fir filters designed by the windowing method.
Abstract: In using filter banks for processing speech signals, it is often important that the sum of the individual frequency responses of the bandpass filters (composite response) be flat with linear phase. This paper presents a technique for achieving flat composite response using linear-phase fir digital filters. The design method is based on some special properties of fir filters designed by the windowing method. Excellent response characteristics can be achieved with complete flexibility in choosing the center frequencies and bandwidths of the individual filters.
28 citations
TL;DR: It is shown that for nonrecursive digital filters in the first canonic form the hardware requirements are proportional to the output rate and that 8 bits are enough for the filter coefficients.
Abstract: It is shown that for nonrecursive digital filters in the first canonic form the hardware requirements are proportional to the output rate. Using a low output rate, a relatively simple receiver for multifrequency-code (MFC) signals can be achieved. Linear phase bandpass pairs with a 90° phase difference are used to eliminate the input signal phase dependence. Narrow linear phase bandpass filters with even and odd symmetric impulse response are compared with filters with no phase constraints. It turns out that linear phase filters are almost as good as filters without phase constraints and that 8 bits are enough for the filter coefficients. Some aspects of the design of a digital receiver for PCM-encoded MFC signals are discussed.
TL;DR: In this paper, the design of symmetric Hilbert transformers is derived from corresponding designs for symmetric half-band low-pass filters, and vice versa, and the latter filter type is particularly useful for interpolation or smoothing in sample-rate alteration.
Abstract: Designs of symmetric Hilbert transformers are shown to be easily derived from corresponding designs for symmetric half-band low-pass filters, and vice versa. The latter filter type is particularly useful for interpolation or smoothing in sample-rate alteration.
TL;DR: In this article, the design of crystal and mechanical filters requires a knowledge of techniques not generally known to the designer of LC filters, these techniques are emphasized in this paper, and a flow chart shows the normal design process, and the electrical transformations that are commonly used to develop the LC designs into useful form.
Abstract: As the design of crystal and mechanical filters requires a knowledge of techniques not generally known to the designer of LC filters, these techniques are emphasized in this paper. The paper discusses the commonality of mechanical resonance possessed by these filters and how this leads to design restrictions. The basics of resonator theory are discussed and also the coupling techniques used to make multi-resonator filters. A listing is supplied of the types of filters that are generally made with mechanical or crystal resonators. A flow chart shows the normal design process, and the electrical transformations that are commonly used to develop the LC designs into useful form are also described. The subjects of tuning techniques and manufacturing methods, in general, are discussed as they can have an important bearing on these types of filters. The properties of the materials conmmonly used for the resonators and the transducers are described, as well as the restrictions that they in turn place on the design process. The paper concludes with a discussion of some topics where more work can and should be done. The aim of the paper is to impart to the nonspecialist some idea of how this important class of filters is designed and manufactured, as well as giving an idea of the performance that can reasonably be expected from them.
TL;DR: In this paper, the authors obtained design formulas for the basic stepped impedance distributed low-pass prototype filter which exhibits a maximally flat or equiripple insertion loss response characteristic, and the coefficients of a truncated power series in the bandwidth scaling factor for the characteristic impedances.
Abstract: Design formulas are obtained for the basic stepped impedance distributed low-pass prototype filter which exhibits a maximally flat or equiripple insertion loss response characteristic. Explicit formulas are given for the coefficients of a truncated power series in the bandwidth scaling factor for the characteristic impedances. For the low-sensitivity digital wave filter based upon this prototype, the multiplier values are given. Computer results on the analysis of the prototype filter using the new design equations are cited, showing the vast improvement over the narrow band, lumped element, explicit design formulas.
TL;DR: In this article, a 2-port filter using piezoelectrically coupled acoustic-surface-wave resonators is described, and a lumped-element equivalent circuit is proposed, with expressions for element values.
Abstract: A 2-port filter using piezoelectrically coupled acoustic-surface-wave resonators is described. A lumped-element equivalent circuit is proposed, with expressions for element values. Theoretical insertion-loss/frequency characteristics of some 2-resonator filters are presented.
28 May 1975
TL;DR: In this paper, a model proposed for an operational amplifier gyrator circuit is used to develop a compensation technique whereby the useful bandwidth of the gyrators circuit can be increased.
Abstract: A model proposed recently for an operational amplifier gyrator circuit is used to develop a compensation technique whereby the useful bandwidth of the gyrator circuit can be increased. The compensation technique is verified first by computer-aided analysis and then by experiment. It is shown that a significant increase in the useful gyrator bandwidth can be achieved by using an inexpensive capacitor. The compensation technique is then applied in the design of a gyrator-C channel-bank filter. The influence of dc-supply voltage and ambienttemperature variations on the performance of the filter is examined.
TL;DR: In this paper, an equivalent dielectric constant is defined for the length of the filter sections, by means of which the lengths of filter sections are to be computed, which can be used to correct the asymmetric response of a parallel-coupled bandpass filter.
Abstract: The difference in odd- and even-mode wavelengths on a parallel-coupled bandpass filter leads to an asymmetric filter response. This asymmetry may be corrected by defining an equivalent dielectric constant, by means of which the lengths of the filter sections are to be computed.
01 Feb 1975
TL;DR: A multichannel filter using a 32-stage CCD analog shift register (ASR) and a recursive two-pole, one-zero network will be described.
Abstract: A multichannel filter using a 32-stage CCD analog shift register (ASR), will be described. The filter uses a recursive two-pole, one-zero network. The center frequencies, bandwidths and gains, are independently programmed using four quadrant multiplying digital-to-analog converters.
12 May 1975
TL;DR: In this article, a practical method for solving the approximation problem for narrowband bandpass filters with equal-ripple passband response and arbitrary phase response is presented, based on the use of generalized Chebyshev rational functions with arbitrary choice of transmission zero locations.
Abstract: A practical method is presented for solving the approximation problem for narrowband bandpass filters with equalripple passband response and arbitrary phase response. The method determines the element values of the low-pass prototype filter and is based on the use of generalized Chebyshev rational functions with arbitrary choice of transmission zero locations. The use of both real frequency and complex frequency transmission zero locations is considered. Results of trial design problems are presented and are related to previous design results to illustrate practical realization and performance limitations.
TL;DR: In this article, it was shown that reverse time filtering of signals which start discontinuously but decay slowly to zero enables output signal discontinuities to be avoided, and that the optimum reverse time filter for exponential signals is an RC filter whose time constant equals that of the decay.
Abstract: The difficulty of defining a digital filter whose frequency characteristics match those of a desired continuous filter is discussed theoretically. The 'impulse invariant' filter design is used to derive a formula for calculating the digital filter parameters. Important aspects of the actual use of digital filters are analysed with special reference to the single section RC, three pole Butterworth and three pole Bessel filters. It is shown that reverse time filtering of signals which start discontinuously but decay slowly to zero enables output signal discontinuities to be avoided. Such filtering enhances the slow decay components of multicomponent exponential decays but leaves the exponential nature of the data unchanged. The optimum reverse time filter for exponential signals is an RC filter whose time constant equals that of the decay. The use of digital filters whose bandwidth echoes changes in the signal information bandwidth are examined with special reference to multicomponent exponential decays.
TL;DR: In this article, the computer implementation of a numerical algorithm for obtaining rational approximations is discussed, which offers the promise of a comprehensive solution to the problems of two-dimensional recursive digital filter design.
Abstract: The computer implementation of a numerical algorithm for obtaining rational approximations is discussed. This method offers the promise of a comprehensive solution to the problems of two-dimensional recursive digital filter design. Combination of this technique with an easily implemented stability test avoids current stability problems in present methods and places no restrictions as to type on filters that may be designed. Both one- and two-dimensional filters may be designed with this technique.
01 Apr 1975
TL;DR: An efficient algorithm is presented for performing optimal Chebyshev approximation in the absence of the Haar condition and has been successfully used in the design of two-dimensional FIR low-pass filters with and without symmetry constraints in the impulse response.
Abstract: : An efficient algorithm is presented for performing optimal Chebyshev approximation in the absence of the Haar condition. It has been successfully used in the design of two-dimensional FIR low-pass filters with and without symmetry constraints in the impulse response and also in the design of special classes of one-dimensional FIR filters with impulse response constraints such as interpolation filters.
TL;DR: In this paper, prototype characteristics of nonequiripple antimetric elliptic-function filters which can be realized in orthogonal cascaded dual-mode circular or square waveguide structures are presented.
Abstract: Selected prototype characteristics of nonequiripple antimetric elliptic-function filters which can be realized in orthogonal cascaded dual-mode circular or square waveguide structures are presented. Cavity-coupling data for 4-, 6-, and S-section 0.01- and 0.05-dB-ripple passband designs with variable stopband levels are tabulated. Quantitative comparisons of elliptic and Chebyshev filter designs are also discussed, indicating the superior characteristics of elliptic networks.
TL;DR: It is shown that recursive band-pass digital filter structures according to a bandpass transformation that is incorporated directly in the structure can be implemented with fewer multiplies than in conventional designs and with shorter coefficient word lengths.
Abstract: Several advantages are observed in designing recursive band-pass digital filter structures according to a bandpass transformation that is incorporated directly in the structure. In particular, it is shown that such structures can be implemented with fewer multiplies than in conventional designs and in some cases, with shorter coefficient word lengths.
01 Oct 1975
TL;DR: In this paper, the synthesis, optimization and practical realization of a 4 GHz waveguide multiplexer composed of a WR229 straight waveguide manifold with one end shorted and dual TE111-mode Chebyshev bandpass filters arranged at intervals along the broad wall sides are treated.
Abstract: The paper treats the synthesis, optimization and practical realization of a 4 GHz waveguide multiplexer composed of a WR229 straight waveguide manifold with one end shorted and dual TE111-mode Chebyshev bandpass filters arranged at intervals along the broad wall sides. The optimization process includes the filter spacings and several initial elements of each distributed filter equivalent circuit. The results of measurements performed on the breadboard model of a 4-channel multiplexer with 4-pole dual-mode filters are in good agreement with the calculated responses.
TL;DR: In this article, a new type of microwave branching filter is proposed, using a curved slotted-waveguide array to focus different frequencies into different receiving apertures in a near-field focal plane.
Abstract: A new type of microwave branching filter is proposed, using a curved slotted-waveguide array to focus different frequencies into different receiving apertures in a near-field focal plane. An example of a theoretical response for a 7-channel filter is given.
TL;DR: It is shown that assigning the poles and zeros "closest to each other" is not always an optimum solution and the dynamic programming method which yields the exact solution is described.
Abstract: Digital filters are often realized by a cascade of second order sections. Each multiplier in the filter generates round-off noise. The noise power at the output is minimized by a suitable selection of the pole-zero pairs, the gain factors and the ordering of the 2nd order sections. These degrees of freedom are optimized simultaneously by dynamic programming which yields an optimal solution. Examples for this method will be presented. It is shown that assigning the poles and zeros \"closest to each other\" is not always an optimum solution. Digitale Filter werden h ufig als Kettenschaltung von Teilfiltern 2. Grades realisiert. Jeder Multiplizierer im Filter erzeugt Rundungsrauschen. Die Rauschleistung am Ausgang kann minimiert werden durch geeignete Wahl der Γοΐ-Nullstellen-Zuofdnung, der Verst rkungsfaktoren und der Reihenfolge in der Kettenschaltung f r die Teilfilter 2. Grades. Diese Freiheitsgrade werden mit dynamischer Programmierung simultan behandelt, was eine optimale L sung liefert. An Hand von Beispielen wird gezeigt, da die Zuordnung von direkt benachbarten Polen und Nullstellen nicht immer eine optimale L sung darstellt. F r die Dokumentation: Digitales Filter / Rundlingsrauschen / Optimierung / Dynamisches Programmieren Introduction Digital filters are often realized by a cascade of 2nd order sections. The multipliers in the filter generate round-off noise. The noise power at the output of the filter should be minimized. To achieve this goal we shall first point out the degrees of freedom for the minimization. Then we shall describe the dynamic programming method which yields the exact solution. Finally we shall give some examples and compare them with previous solutions. The degrees of freedom We start our investigation with a given rational transfer function
TL;DR: In this paper, a new class of low-pass filter, referred to as transitional Halpern-Thomson (t.h.t.) filters, has been proposed, which enables a tradeoff between, the overshoot and the risetime in response to a unit-step input.
Abstract: A new class of lowpass filter, with all transmission zeros at infinity, having a monotonic passband response is described. The transfer function of these filters, referred to as transitional Halpern-Thomson (t.h.t.) filters, depends on a variable parameter that enables a tradeoff between, the overshoot and the risetime in response to a unit-step input.