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Showing papers on "Butterworth filter published in 1974"


Patent
Harry F. Chapell1
01 Aug 1974
TL;DR: In this paper, a multiple-section L-C Chebyshev low-pass filter prototype is designed to support only one mode in both the passband and primary stop band, and the series inductors are calculated in accordance with evanescent mode operation.
Abstract: The filter may be designed from a multiple section L-C Chebyshev low pass filter prototype and is of generally ridged filter construction. The distributed shunt capacitors in the ridged section are designed to support only one mode in both the passband and primary stop band. The series inductors are calculated in accordance with evanescent mode (below cut-off) operation.

25 citations


Journal ArticleDOI
TL;DR: In this article, an extension of the Bessel filter is given for which the transfer function is a rational function with finite zeros, and a design example for a second-order all-pass constant time delay filter with linear phase response is given.
Abstract: An extension of the Bessel filter is given for which the transfer function is a rational function with finite zeros A special case is shown to combine the constant magnitude response of the all-pass filter with the linear phase response of the Bessel filter A design example for a second-order all-pass constant time delay filter is given; there is good agreement with theory

23 citations


Patent
18 Jul 1974
TL;DR: In this paper, a low-pass microwave filter consisting of a two-conductor transmission line including at least two cascaded tapered sections is described. But the filter does not exhibit the usual rapid transition between the pass band and stop band which is a general characteristic of conventional low pass microwave filters utilizing reflective harmonic structures.
Abstract: A low pass microwave filter comprised of a two conductor transmission line including at least two cascaded tapered sections wherein one of the conductors in each filter section has a tapered surface, preferably linear, and having an electrical length substantially equal to one half the wavelength of the center frequency of operation. Geometrically and performance-wise the subject filter is unsymmetrical with respect to its input and output ports. The filter does not exhibit the usual rapid transition between the pass band and stop band which is a general characteristic of conventional low pass microwave filters utilizing reflective harmonic structures.

21 citations


Journal ArticleDOI
TL;DR: In this paper, an analytical solution for the transfer function of a digital filter which exhibits an optimum maximally flat amplitude characteristic and a maximumally flat delay characteristic simultaneously was obtained for the direct realization in terms of the degree of the network and an arbitrary bandwidth scaling factor.
Abstract: An analytical solution is obtained for the transfer function of a digital filter which exhibits an optimum maximally flat amplitude characteristic and a maximally flat delay characteristic simultaneously. Explicit values for the multipliers are given for the direct realization in terms of the degree of the network and an arbitrary bandwidth scaling factor. Finally, it is concluded that this type of filter is useful in the area where the degree of a non-recursive filter becomes excessive to fulfil an amplitude requirement (e.g. narrow bandwidth) and where recursive filters designed solely on an amplitude basis are too dispersive.

19 citations


Patent
24 Jan 1974
TL;DR: A digital filter with a cut-off frequency of fc to which code words of a frequency fs are applied and which supplies code words at a frequency f's is described in this paper.
Abstract: A digital filter having a cut-off frequency of fc to which code words of a frequency fs are applied and which supplies code words at a frequency of f's The filter comprises a first digital filter section supplying numbers having a reduced frequency fm and whose output is directly coupled to an interpolating digital filter supplying the outgoing numbers of the filter at the frequency f's The first filter section and the interpolating digital filter are each built up as a digital filter having a cut-off frequency of fm/2

16 citations


Journal ArticleDOI
TL;DR: In this article, a new class of monotonic passband low-pass filters, referred to as transitional Butterworth-Legendre (TBL) filters, is introduced.
Abstract: A new class of monotonic passband low-pass filters, referred to as transitional Butterworth-Legendre (TBL) filters, is introduced. The closed form expressions of the characteristic functions of these filters depending on one variable parameter q are derived by generalization of the results previously obtained for Legendre sharp cut-off monotonic filters. The parameter q, the values of which are restricted to non-negative integer values (q≤n) controls the number of flatness conditions in the magnitude response at the origin and enables a trade-off between the passband loss and the stopband attenuation of the resulting filters. The Legendre, Halpern and Butterworth filters are shown to be special cases of TBL filters. Only all-pole filter functions are discussed although the results can easily be extended so as to include low-pass filters with finite real frequency transmission zeros.

15 citations


Patent
04 Feb 1974
TL;DR: The n-pole filter as discussed by the authors has four filter circuits cascaded in series, each of the filter circuits is a low-pass filter circuit and each has a controllable frequency response which is variably controlled from a common current or voltage source.
Abstract: The n-pole filter preferably has four filter circuits cascaded in series. Each of the filter circuits is preferably a low-pass filter circuit and each has a controllable frequency response which is variably controlled from a common current or voltage source. Each filter circuit includes a transconductance circuit and inverting operational amplifier. A feedback resistor couples between the first and last filter circuits and is adjustable to provide different amounts of resonance.

13 citations


Patent
28 Mar 1974
TL;DR: In this article, the first and second parallel coupled filter branches are coupled in series to form a filter circuit, with the adder of the second pair of filter branches generating the output signal of the filter circuit and being coupled to the signal feedback means of the circuit.
Abstract: A filter circuit which comprises first and second parallel coupled filter branches each including a first multiplier, an intermediate frequency filter, and a second multiplier, respectively, coupled in series. A signal generator generates two output signals which are linearly independent of each other at a frequency which is equal to that of an input signal which is to be passed by the filter branches, and has a pair of output terminals coupled to the first multipliers of the filter branches for transmitting these output signals thereto. An adder is coupled to the second multipliers of the filter branches and generates an output signal which forms the output signal of the filter circuit. An adjustable signal feedback means is coupled to the output of the adder and to the inputs of the first multipliers of the filter branches for adjusting the bandwidth of the filter circuit. In an alternative embodiment of the invention, two pairs of identical filter branches are series coupled to form the filter circuit, with the adder of the second pair of filter branches generating the output signal of the filter circuit and being coupled to the signal feedback means of the circuit.

10 citations


Journal ArticleDOI
TL;DR: In this article, a hairpin bandpass filter and a folded-line bandstop filter are used for channel-dropping in MIC systems, which is particularly suited for stripline and microwave integrated circuits (MIC).
Abstract: A compact channel-dropping filter geometry is described that is particularly suited for stripline and microwave integrated circuits (MIC). The channel-dropping filter is comprised of a hairpin bandpass filter and a new bandstop filter, referred to herein as a folded-line bandstop filter. Design parameters for the latter filter for a range of bandwidths are tabulated. Analytical and experimental data for a trial channel-dropping filter are presented and discussed.

7 citations


Journal ArticleDOI
TL;DR: In this paper, a filter structure for over-moded circular waveguide is presented which fulfills all aspects of the design objectives, including mode conversion loss, ease of being analyzed and synthesized, and feasibility for economical fabrication.
Abstract: As the frequency spectrum extends to the millimeter wave range, the rapid rise in intrinsic loss and the diminishing physical dimensions greatly curtail the usefulness of conventional waveguide filters in dominant mode waveguide The incentive for designing filters in over-moded waveguide is all too apparent However, filter design in over-moded waveguide faces challenging design criteria, such as mode conversion loss and intrinsic loss, ease of being analyzed and synthesized, and feasibility for economical fabrication A filter structure is presented which fulfills all aspects of the design objectives The structure involves a type of discontinuity which is not only free from mode conversion but also extremely simple to characterize analytically The latter renders feasible the use of available filter synthesis techniques While the proposed filter structure can be designed either as a bandpass filter, a bandstop filter or a low-pass filter in an over-moded uniform waveguide of arbitrary cross section, for illustration purposes only the low-pass filter in over-moded circular waveguide is discussed in great detail Design theories are presented which allow the proposed structure to be designed either by the image method or by operating parameter filter synthesis Excellent agreement between the theory and measurements made on filter models is shown

6 citations


Journal ArticleDOI
TL;DR: In this paper, a canonic active RC low-pass filter with both capacitors earthed is presented, and the ω0 and the Q sensitivities with respect to all circuit components are derived.
Abstract: A canonic active RC low-pass filter having both capacitors earthed is given. The ω0 and the Q sensitivities with respect to all circuit components are derived. A unique feature of the circuit is that uo, is absolutely insensitive to the gain-bandwidth of the operational amplifiers.

Journal ArticleDOI
01 Apr 1974
TL;DR: In this paper, it was shown that the poles of sharp cutoff low-pass filters can be obtained analytically for orders 3, 4, 6, and 8, through the solution of quadratic, cubic, or quartic algebraic equations.
Abstract: It is shown that the poles of sharp cutoff low-pass filters, Butterworth- or Chebyshev-derived, can be obtained analytically for orders 3, 4, 6, and 8, through the solution of quadratic, cubic, or quartic algebraic equations. For the Butterworth case, higher order filters having a value of 3, 4, 6, 8 for the ratio (order of filter)/(order of zero) are also shown to have analytical solutions for the poles. Explicit solutions for the Butterworth-derived filter are given for third and fourth orders.

Proceedings ArticleDOI
12 Jun 1974
TL;DR: In this paper, the feasibility of a new, compact bandstop filter geometry is demonstrated theoretically and experimentally, and the filter geometry was particularly suited for stripline and MIC fabrications in that grounding is not required for any part of the filter.
Abstract: The feasibility of a new, compact bandstop filter geometry is demonstrated theoretically and experimentally. The filter geometry is particularly suited for stripline and MIC fabrications in that grounding is not required for any part of the filter. Hybrid folded-line geometries allow the filter designer substantial flexibility in choosing a suitable shape factor without significantly effecting the filter's electrical characteristics. The filter geometry is suitable for narrow bandwidth (provided capacitive coupled stubs are used) to wide bandwidth applications.

01 Jan 1974
TL;DR: In this paper, a filter structure for over-moded waveguide is presented which fulfills all aspects of the design objectives, such as mode conversion loss and intrinsic loss, ease of being analyzed and synthesized, and feasibility for eco-nomical fabrication.
Abstract: As the frequency spectrum extends to the millimeter wave range, the rapid rise in intrinsic loss and the diminishing physical dimensions greatly curtail the usefulness of conventional waveguide filters in dominant mode waveguide. The incentive for designing filters in over-moded waveguide is all too apparent. How- ever, filter design in over-moded waveguide faces challenging design criteria, such as mode conversion loss and intrinsic loss, ease of being analyzed and synthesized, and feasibility for eco- nomical fabrication. A filter structure is presented which fulfills all aspects of the design objectives. The structure involves a type of discontinuity which is not only free from mode conversion but also extremely simple to characterize analytically. The latter renders feasible the use of available filter synthesis techniques. While the proposed filter structure can be designed either as a bandpass filter, a bandstop filter or a low-pass filter in an over-moded uniform wave- @de of arbitrary cro& section, for illustration purposes only the low-pass filter in over-moded circular waveguide is discussed in great detail. Design theories are presented which allow the proposed structure to be designed either by the image method or by operating parameter filter synthesis. Excellent agreement between the theory and measurements made on filter models is shown.

Journal ArticleDOI
TL;DR: In this paper, a system is described that automatically and rapidly measures the electrical parameters for each channel in a multichannel digitally tuned bandpass filter, and the performance of the filter over its entire tuning range is determined from the individual channel frequency characteristics.
Abstract: A system is described that automatically and rapidly measures the electrical parameters for each channel in a multichannel digitally tuned bandpass filter. The performance of the filter over its entire tuning range is determined from the individual channel frequency characteristics. Channel frequency characteristics are displayed to summarize the overall performance of the filter and in such a manner as to indicate the channel tuning adjustments necessary to meet the filter specifications.

Journal ArticleDOI
TL;DR: In this article, the authors used bucket-brigade devices to build a new type of active filter that is equivalent to a second-order digital filter without the need for complex analog-to-digital conversion.
Abstract: Bucket-brigade devices have been used to build a new type of active filter that is equivalent to a second-order digital filter without the need for complex analog-to-digital conversion. The x It) filter response characteristics, i.e., center frequency and bandwidth, + I depend on the circuit parameters of gain and clock frequency, both e2(t- U of which may be electronically controlled. + By using a variable clock signal, 1023 frequencies can be ac- I e0%, curately selected by the proper setting of ten switches. The selected clock frequency uniquely determines the center frequency of the bucket-brigade filter. The programmable feature of the clock circuit, DELAND therefore, allows the convenient selection of the center frequency u It-T,) of the bandpass filter. A slight modification to the programmable bandpass filter converts it into a programmable oscillator. Thus, any one of 1023 tones can be generated by the proper setting of the switches. A device that ex- D hibits both filter and oscillator functions has been demonstrated in the laboratory.

Journal ArticleDOI
TL;DR: A new technique for voltage-controlled filtering is presented, based on a linear system with periodically operated synchronous switches, and though only Butterworth filters were considered, the method is expected to have much broader applications.
Abstract: A new technique for voltage-controlled filtering is presented in this work. The results to be expected from the technique are analyzed by simulation since the filter can be described analytically only through approximations. The filtering technique is based on a linear system with periodically operated synchronous switches. A hardware model of the filter was built and the digital simulation outputs are compared with those obtained with the hardware. Filtering performances in the simulation and in the hardware were in close agreement. Though only Butterworth filters were considered, the method is expected to have much broader appli cations.