Showing papers on "Prototype filter published in 1972"
TL;DR: An efficient procedure for the design of finite-length impulse response filters with linear phase is presented, which obtains the optimum Chebyshev approximation on separate intervals corresponding to passbands and/or stopbands.
Abstract: An efficient procedure for the design of finite-length impulse response filters with linear phase is presented. The algorithm obtains the optimum Chebyshev approximation on separate intervals corresponding to passbands and/or stopbands, and is capable of designing very long filters. This approach allows the exact specification of arbitrary band-edge frequencies as opposed to previous algorithms which could not directly control pass- and stopband locations and could only obtain (N - 1)/2 different band-edge locations for a length N low-pass filter, for fixed \delta_{1} and \delta_{2} . As an aid in practical application of the algorithm, several graphs are included to show relations among the parameters of filter length, transition width, band-edge frequencies, passband ripple, and stopband attenuation.
806 citations
TL;DR: In this article, a simple filter for controlling high-frequency computational and physical modes arising in time integrations is proposed, and a linear analysis of the filter with leapfrog, implicit, and semi-implicit, differences is made.
Abstract: A simple filter for controlling high-frequency computational and physical modes arising in time integrations is proposed. A linear analysis of the filter with leapfrog, implicit, and semi-implicit, differences is made. The filter very quickly removes the computational mode and is also very useful in damping high-frequency physical waves. The stability of the leapfrog scheme is adversely affected when a large filter parameter is used, but the analysis shows that the use of centered differences with frequency filter is still more advantageous than the use of the Euler-backward method. An example of the use of the filter in an actual forecast with the meteorological equations is shown.
799 citations
TL;DR: In this paper, a procedure was described whereby narrow-band pass waveguide filters having ripple in both the passbands and stopbands can be synthesized in the form of coupled waveguide cavities.
Abstract: A procedure is described whereby narrow-bandpass waveguide filters having ripple in both the passbands and stopbands can be synthesized in the form of coupled waveguide cavities. Orthogonal modes in square or circular waveguides are employed to enable negative coupling elements to be realized. As a consequence, very compact filters can be constructed. Experimental results on an 8-cavity orthogonal-mode narrow-bandpass filter are shown to agree well with theory.
564 citations
TL;DR: Two-dimensional recursive bandpass filters as mentioned in this paper can be synthesized to approximate large varieties of desired two-dimensional pulse responses by a conformal transformation of the one-dimensional filters.
Abstract: Two-dimensional recursive filters are conveniently described in terms of two-dimensional z transforms. The designer of these filters faces two fundamental problems, their stability and their synthesis. Stability is determined by the location of the zero-valued region of the filter's denominator polynomial. A conjecture based on a one-dimensional stability theorem leads to a useful empirical stabilization procedure. Two-dimensional recursive filters can be synthesized to approximate large varieties of desired two-dimensional pulse responses. A conformal transformation yields two-dimensional recursive bandpass filters from appropriately specified one-dimensional filters.
340 citations
TL;DR: In this paper, a new class of microwave filters, hairpin line and hybrid hairpin-line/half-wave parallel-coupled-line filters, was reported, which is particularly well suited for microstrip and TEM printed-circuit realizations because grounding of the filter resonators is generally not required.
Abstract: A new class of microwave filters, hairpin-line and hybrid hairpin-line/half-wave parallel-coupled-line filters, is reported. This class of filters is particularly well suited for microstrip and TEM printed-circuit realizations because grounding of the filter resonators is generally not required. Hairpin-line filters have been divided into two types. The first (Type A) is characterized by having its input and output lines open-circuited at their ends. The Type A filter has been found to yield practical impedance levels for narrow to approximately 25-percent bandwidths. The second (Type B) is characterized by having its input and output lines short-circuited at their ends. However, because of space limitations, details of the Type B filter are not presented in this paper. Theoretical background and design equations for Type A bandpass filters are presented. Experimental data for several stripline filters of 5- and 20-percent bandwidths are given. Experimental results for two microwave-integrated-circuit (MIC) filters are discussed.
258 citations
TL;DR: The use of linear programming techniques for designing digital filters has become widespread in recent years as discussed by the authors, among the techniques that have been used include steepest descent methods, conjugate gradient techniques, penalty function techniques and polynomial interpolation procedures.
Abstract: The use of optimization techniques for designing digital filters has become widespread in recent years. Among the techniques that have been used include steepest descent methods, conjugate gradient techniques, penalty function techniques, and polynomial interpolation procedures. The theory of linear programming offers many advantages for designing digital filters. The programs are easy to implement and yield solutions that are guaranteed to converge. There are many areas of finite impulse response (FIR) filter design where linear programming can be used conveniently. These include design of the following: filters of the frequency sampling type; optimal filters where the passband and stopband edge frequencies of the filter may be specified exactly; and filters with simultaneous constraints on the time and frequency response. The design method is illustrated by examples from each of these areas.
175 citations
TL;DR: The theory for designing finite-duration impulse response (FIR) digital filters can readily be extended to two or more dimensions using linear programming techniques, and several of the issues involved in designing two-dimensional digital filters are discussed in this article.
Abstract: The theory for designing finite-duration impulse response (FIR) digital filters can readily be extended to two or more dimensions. Using linear programming techniques, both frequency sampling and optimal (in the sense of Chebyshev approximation over closed compact sets) two-dimensional filters have been successfully designed. Computational considerations have limited the filter impulse response durations (in samples) to 25 by 25 in the frequency sampling case, and to 9 by 9 in the optimal design case. However, within these restrictions, a large number of filters have been investigated. Several of the issues involved in designing two-dimensional digital filters are discussed.
116 citations
TL;DR: Two methods for reducing the necessary word length of a digital filter by choosing a suitable structure for the filter and taking selective filters as a model will be presented.
Abstract: The cost of a digital filter, if implemented as a special-purpose computer, depends heavily on the word length of the coefficients. Therefore, it should be reduced as much as possible. On the other hand, a small word length causes large coefficient deviations that impair the wanted performance of the digital filter. The necessary word length may be reduced by choosing a suitable structure for the filter. Two methods for doing this will be presented, taking selective filters as a model. A further reduction of the word length may be won by optimizing the rounded filter coefficients in the discrete parameter space. A description of a modified univariate search will be given.
104 citations
TL;DR: In this article, the authors apply linear programming techniques to finite impulse response digital filters with arbitrary magnitude response and linear phase constraints, and show how to design filters with exactly linear phase and arbitrary magnitude responses.
Abstract: In this paper it is shown how standard linear programming techniques can be applied to designing finite impulse response digital filters. Attention is concentrated on designing filters having exactly linear phase, and arbitrary magnitude response. The design method is illustrated by examples of the design of frequency sampling filters with constraints on in-band ripple, optimal filters where the passband and stopband cutoff frequencies may be specified exactly, and filters with simultaneous constraints on the time response and frequency response.
95 citations
TL;DR: An analogue sample-data filter exactly equivalent, in the sample- data limit, to a simple RC low pass filter is demonstrated and the basic concept is extended to apply to high-pass and to very-high-Q bandpass filters.
Abstract: An analogue sample-data filter exactly equivalent, in the sample- data limit, to a simple RC low pass filter is demonstrated. The implementation requires only capacitors, MOSFETS, and a pulse generator. The filter time constant can be adjusted by changing the generator's pulse rate. The basic concept is then extended to apply to high-pass and to very-high-Q bandpass filters.
84 citations
TL;DR: In this article, the authors considered the effect of quantization of FIR filter coefficients on the frequency response and showed that quantization can improve the performance of FIR filters with respect to the log of the sample rate reduction ratio.
Abstract: The design of bandwidth-limiting filters for the purpose of sample-rate reduction is considered. Realization of linear-phase finite-duration impulse-response (FIR) filters for this application by direct convolution is shown to be more efficient than the recursive realization [1]. The degree to which the Nyquist rate (relative to the desired signal bandwidth) must be exceeded at the filter output in order to avoid aliasing is suggested as a measure of filter effectiveness. Direct convolution is faster than the fast convolution for FIR equiripple [2] filters designed to operate within 10 percent of the Nyquist rate with 60- to 70-dB stopband attenuation at a 2:1 sample-rate reduction. This advantage improves with the log of the sample-rate reduction ratio. Several comparisons made with recursive realizations of elliptic filters give the advantage to direct convolutional realization of FIR filters for sampling within about 20 percent of the Nyquist rate at 60- to 70-dB attenuation. Elliptic filters become more efficient at higher complexities (of about eight poles and eight zeros). Two design techniques that exploit the reduced output sample rate in the design of FIR filters by direct convolution are suggested. The effects of quantization of FIR filter coefficients on the frequency response are considered and several examples illustrated.
TL;DR: In this paper, a design procedure for a class of waveguide bandstop filters, which exhibit equiripple passband and stopband responses, is presented, using the natural prototype elliptic function filter.
Abstract: Using the "natural prototype" for elliptic function filters, a design procedure is presented for a class of waveguide bandstop filters, which exhibit equiripple passband and stopband responses. Due to the availability of explicit formulas for element values in the natural prototype elliptic function filter, the design procedure is entirely analytic and does not require numerical synthesis techniques. The resulting physical structure is the familiar uniform guide with iris-coupled series stubs. Unlike the bandstop filters designed from maximally flat or Chebyshev prototypes, the elliptic function design results in stubs that are not exactly three-quarter-wave coupled.
TL;DR: In this article, a tunable active bandpass filter with bucket-brigade delay lines was used to build an active band pass filter, and experimental results showed the dependence of center frequency and bandwidth on the delay-line clock frequency.
Abstract: Bucket-brigade delay lines have been used to build a tunable active bandpass filter. Experimental results showing the dependence of center frequency and bandwidth on the delay-line clock frequency, and the dependence of the center frequency and the Q of the filter on internal gain parameters are presented.
TL;DR: A new class of active filters using a single unity-gain amplifier is introduced and shown to have a gain-sensitivity product and a maximum spread of component values lower than those for the corresponding Sallen and Key circuits.
Abstract: A new class of active filters using a single unity-gain amplifier is introduced and shown to have a gain-sensitivity product and a maximum spread of component values lower than those for the corresponding Sallen and Key circuits by a factor of Q.
TL;DR: In this article, the development of infrared filters of both low-pass and bandpass types for the wavelength region λ>40 μm is discussed, and the design techniques of multilayer filters have been extended to mesh filters.
Abstract: This paper discusses the development of infrared filters of both lowpass and bandpass types for the wavelength region λ>40 μm. The design techniques of multilayer filters have been extended to mesh filters. Bandpass filters at wavelengths near 50 and 100 μm with bandwidths between 5% and 10% and up to 90% transmission have been made using either double-halfwave or Fabry-Perot systems. Lowpass filters of high performance, passband transmission 70% and rejection greater than 103 are shown with edges near 100 μm. Narrowband filters for the HCN laser line at 30 cm−1 are also shown.
Patent•
26 Jun 1972
TL;DR: In this article, a filter system for a communications system such as a bidirectional CATV system is presented, which consists of diplex filters having a substantially constant input impedance and a band stop filter to suppress signals at the cross-over frequency of the DIFR.
Abstract: A filter system for a communications system such as a bidirectional CATV system is shown. The filter system includes diplex filters having a substantially constant input impedance and a band stop filter to suppress signals at the cross-over frequency of the diplex filters.
01 Jun 1972
TL;DR: In this paper, a microstrip bandpass filter with dielectric resonators made of a temperature-compensated material was built with a temperature coefficient less than 5 ppm/°C.
Abstract: A microstrip bandpass filter has been built with dielectric resonators made of a temperature-compensated material. Its unloaded Q at X band is calculated to be greater than 1200, a four-fold improvement upon conventional printed-on devices. With additional temperature compensation, a temperature coefficient less than 5 ppm/°C is shown to be feasible.
TL;DR: In this article, the general Remes exchange algorithm and its implementation are discussed briefly and an analog of the exchange algorithm is applied to the problem in which upper and lower constraints are imposed on the frequency response of a non-recursive digital filter with linear phase.
Abstract: The general Remes exchange algorithm and its implementation are discussed briefly An analog of the exchange algorithm is applied to the problem in which upper and lower constraints are imposed on the frequency response of a nonrecursive digital filter with linear phase. A typical design example is presented with rather tight constraints in the passband
Patent•
14 Apr 1972
TL;DR: A combination bandpass and rejection filter system with a null point at the center frequency was proposed in this paper, where the null point was defined as a null node at a center frequency.
Abstract: A combination bandpass and rejection filter system having a null point at a center frequency, comprising:
TL;DR: In this article, the frequency domain representation of the Doppler-invariant frequency modulated signal is derived from relativistic constraints upon the reflection of electromagnetic waves from targets moving with constant velocities.
Abstract: From the relativistic constraints upon the reflection of electromagnetic waves from targets moving with constant velocities, the frequency-domain representation of the Doppler-invariant frequencymodulated signal is derived. This frequency spectrum of the signal uniquely defines the matched-pulse compression filter which approximates to a rectangular amplitude response with a hyperbolic group-delay characteristic over the passband. A maximally flat solution to the problem is derived in closed form and leads to explicit formulas for element values in the canonic nonreciprocal realization, thus enabling a large degree filter to be constructed without recourse to numerical synthesis.
TL;DR: Although the results of that section are correct for the conditions stated, the constraints on phase delay and H_{(N-1)/2} are more restrictive than necessary.
Abstract: The purpose of this correspondence is to correct some inaccuracies in the above paper. Specifically, we refer to the results in the Section "Linear Phase Type 2 Filters" (pp. 205-207). Although the results of that section are correct for the conditions stated, the constraints on phase delay and H_{(N-1)/2} are more restrictive than necessary. Therefore, we offer the following as a correction to the original section.
TL;DR: In this paper, the 4-port non-reciprocal band-stop-pass filter and the tunable resonance type circulator with the properties of the 4port filter are reported.
Abstract: Experimental results of the 4-port nonreciprocal band-stop-pass filter and the tunable resonance type circulator with the properties of the 4-port filter are reported, and the theory of the new nonreciprocal circuit is discussed. The filter operates over a two-octave frequency range and the over about a one-octave frequency range.
TL;DR: In this article, a design procedure for the realization of selective linear-phase channel filters in a cascade configuration is presented, where synthesis is performed using symmetrical second-degree transmission zero producing sections which contain frequency invariant reactances, and the overall network is constructed with complex conjugate symmetry.
Abstract: A design procedure is presented for the realization of selective linear-phase channel filters in a cascade configuration. From the transfer function which exhibits optimum maximally fiat amplitude and linear phase characteristics, synthesis is performed using symmetrical seconddegree transmission zero producing sections which contain frequencyinvariant reactances, and the overall network is constructed with complex conjugate symmetry. Conversion is made to lumped-element bandpass channel filters using the reactance slope parameter method. In all but very narrow bandwidths, dispersion occurs in the bandpass filter, but it is shown that by choosing a dispersive modification to the prototype, flat group-delay characteristics may be recovered in the bandpass filter.
TL;DR: It is shown that significant improvement in the frequency response of the composite filter bank can be achieved by appropriate choice of the relative phases of the bandpass filters.
Abstract: Short‐time spectrum analysis is the basis for many speech analysls systems. Although the fast Fourier transform is generally used to perform spectrum analysis on a general purpose computer, a bank of recursire digital bandpass filters may be the best approach for hardware realizations. This paper discusses the analysis and design of digital filter banks composed of equal‐bandwidth, equally spaced, bandpass filters. It is shown that significant improvement in the frequency response of the composite filter bank can be achieved by appropriate choice of the relative phases of the bandpass filters. Also discussed is an efficient general purpose computer simulation of a bank of recursire digital filters as required, for example, in a phase vocoder analyzer [Flanagan and Golden, Bell Syst. Tech. J. (Nov. 1966), This simulation uses the fast Fourier transform to compute filter outputs at a low sampling rate (approximately 100 Hz). For synthesis, the spectrum parameters are interpolated to a 10‐kHz sampling rate u...
TL;DR: It has been shown that the frequency sampling technique for the design of nonrecursive digital filters in conjunction with a search for optimum transition band samples yields good digital filter designs.
Abstract: It has been shown that the frequency sampling technique for the design of nonrecursive digital filters in conjunction with a search for optimum transition band samples yields good digital filter designs. It is shown that the frequency sampling technique is directly related to the Fourier series design and modifications are proposed for simplifying the design procedure.
01 Nov 1972
TL;DR: In this paper, a z transform analysis of digital filters operated with non-uniform sample periods is presented, applicable to filters using a mean-square definition of transfer function, e.g. moving-target-indicator filters, and also to conventional digital filters.
Abstract: The paper presents a z transform analysis of digital filters operated with nonuniform sample periods. The analysis is applicable to filters using a mean-square definition of transfer function, e. g. moving-target-indicator filters, and also to conventional digital filters. The evaluation of the frequency response of such filters using the analytic results of the paper leads to considerable savings in computation time over direct simulation methods. Nonuniform sampling of conventional digital filters is shown to result in a reduction of the effective Nyquist frequency, although, within this limited frequency range, additional control of the frequency response is possible for certain filters. A pole-zero diagram may be drawn for a nonuniformly sampled filter, and allows comparisons to be made with the corresponding uniformly sampled case.
TL;DR: A new type of voltage-controlled tunable distributed RC filter is described by the type metal-insulator-semiconductor-metal, attained by field-effect control of the capacitance by a bias voltage, independently of the distributed resistance.
Abstract: A new type of voltage-controlled tunable distributed RC filter is described by the type metal-insulator-semiconductor-metal Tuning is attained by field-effect control of the capacitance by a bias voltage, independently of the distributed resistance Results are given for evaporated thin-film NiCr-Y/SUB 2/O/SUB 3/-CdS-Al filters, together with illustrative applications to tunable RF networks
TL;DR: In this article, a frequency discriminator using two Rayleigh-wave filters and two rectifying networks is described, where one transducers has a finger length varying according to a (sin x/x)2 law, so that the frequency response is almost triangular.
Abstract: A frequency discriminator using two Rayleigh-wave filters and two rectifying networks is described. For each filter, one of the transducers has a finger length varying according to a (sin x/x)2 law, so that the frequency response is almost triangular. The central frequencies of the two filters are different. The direct voltages, obtained after rectifying diodes are connected at the output of each filter, are subtracted. The frequency-discriminator response is almost linear over a 1.4 MHz frequency interval and is zero at 29.75 MHz.
TL;DR: In this paper, a new class of monotonic low-pass filter functions which derives its origin from a method of determining optimum monotone lowpass filters described by Halpern is introduced, yielding a very flat passband response and a considerably higher attenuation rate than the all-pole Butterworth functions.
Abstract: A new class of monotonic low-pass filter functions which derives its origin from a method of determining optimum monotonic lowpass filters described by Halpern is introduced. These functions yield a very flat passband response and a considerably higher attenuation rate than the all-pole Butterworth functions. It is also shown by a numerical example that they compare favorably with the maximally flat rational approximants with one pair of imaginary-axis zeros when the comparison is made on the basis of equal complexity of the resulting network.