Showing papers on "Butterworth filter published in 1969"

The Stepped Digital Elliptic Filter

Abstract: The design and synthesis of various types of microwave elliptic function filters has been accomplished by a number of authors. However, one problem in this field which remains is the realization of compact narrow-band bandpass elliptic function filters. In this paper, a procedure is presented which enables this class of filters to be constricted in a compact digital form. Since the physical realization is in the form of an n-wire line, one-quarter of a wavelength Iong at the center frequency of the passband, where the impedance levels are stepped along the center of the coupled lines, the filter has been termed the stepped digital elliptic filter. The absence of awkward interconnections in the filter due to the stepped digital structure inherently implies that reasonable insertion loss characteristics may be achieved in the X-band region and above, and also simplifies the mechanical construction. It is shown that the resonant elements in the filter, due to the design procedure adopted, are relatively insensitive to the absolute bandwidth of the filter, and consequently fractional bandwidths of approximately 30 percent and below may be readily achieved while the normalized impedance values of the elements in the network remain of the order of unity. This latter result is similar to that obtainable from conventional interdigital filters but in the case of narrow bandwidths the stepped digital filter is considerably smaller in physical size. A systematic procedure is also formulated for the inclusion of the parasitic lumped end effect capacitances into the overall design procedure in order to maintain the equiripple passband and stopband responses. Experimental results are presented for a five-element, 11 percent bandwidth filter and are shown to be in good agreement with theoretical predictions.

N-path filter using digital filter as time invariant part

Abstract: A time division multiplexed digital filter is used as the timeinvariant part of an N-path filter. The use of a multiplexed digital filter alleviates the problem of closely matching the transmission characteristics of each of the N-paths.

The Half-Wave Stepped Digital Elliptic Filter

Abstract: A design procedure for narrow-band bandpass TEM-line elliptic-function filters is presented. The proposed realization is in the form of a stepped-impedance digital n-wire line which is one-half of a wavelength long at midband and short circuited to ground at both ends, where the digital line is stepped in impedance along any arbitrary prescribed plane in the filter. Due to its physical form and mode of electrical operation, the filter has been termed the half-wave stepped digital elliptic filter. A detailed design procedure for the construction of the two characteristic admittance matrices which describe the digital n-wire line from the low-pass prototype element values is presented. It is also shown that the normalized impedance values of the elements in the filter are all of the order of unity and independent of the actual bandwidth of the falter except for the input and output transformer elements. A numerical example and experimental results on a seventh-degree 1-percent bandwidth filter with a center frequency at 3.7 GHz are given, demonstrating the significant improvements which may be obtained from the half-wave stepped digital elliptic filter over most other known form of microwave TEM-line narrow-band bandpass filter.

A tuneable, Bandwidth-adjustable solid-state filter☆

Abstract: Tuneable adjustable solid state bandwidth filter using N path system for low pass to bandpass filter transformation

Narrow Bandwidth Elliptic-Function Filters

Abstract: Although wide bandwidth microwave elliptic-function filters have previously been reported, this paper describes a circuit which provides, for the first time, a narrow bandwidth elliptic-function response at microwave frequencies. It is for narrow bandwidth applications (from 5 percent to a fraction of a percent) that the elliptic-function filter offers its most important advantages over other filter types--lower loss and greater selectivity. These features are verified by theoretical analysis and experimental data on a 1-percent bandwidth S-band stripline filter. The design of the filter, which is based upon the low-pass prototype, is simple to obtain with the relationships presented in this paper, and the elliptic-function response is readily realizable in printed or other TEM transmission lines. A waveguide elliptic-function filter is also discussed, but experimental verification of this has not yet been attempted.

Vhf filter having absorptive tuned section to eliminate narrow spurious passband

Abstract: Disclosed is a very high frequency filter for use with a high frequency radio transmitter which prevents transmission of harmonics. The filter includes an absorptive filter which eliminates spurious passbands resulting from interaction of components. The absorptive filter includes highpass filters arranged in an L-network.

Hybrid filter for two-way transmission over a single line

Abstract: A hybrid filter is disclosed wherein the characteristics of a hybrid coupler and high and low pass filters are combined. Each port of the hybrid filter exhibits a constant input impedance that is independent of frequency. The hybrid filter provides a common, low pass and a high pass port, thus providing both frequency and power isolation between branches.

The Stepped Cavity Coupled Elliptic Filter

Abstract: A design procedure is presented whereby compact, narrow-band (<30%) T.E.M. line, band-pass, elliptic function filters may be realized. The proposed realization is in the form of a stepped impedance, digital n-wire line which is one half of a wavelength long at midband and short circuited to ground at both ends, where the digital line is stepped in impedance along any arbitrary prescribed plane in the filter. Due to its physical form and the mode of electrical operation, the filter has been called "The Stepped Cavity Coupled Elliptic Filter". Recently, "The Stepped Digital Elliptic Filter" has been proposed as a realization of the narrow-band, band-pass elliptic filter and consisted of a stepped impedance digital n-wire line , one quarter of a wavelength long at mid-band where the line was shorted to ground at one end and open-circuited at the opposite end. In this filter, the fringing capacitances at the open-circuited ends of the line necessitate the use of a compensation procedure based upon an estimation of these parasitic lumped capacitances. Consequently, in the very narrow-band cases, where these end effect capacitances have a considerable effect upon the performance of the filter, it is very difficult to construct a filter with the required electrical performance. In the new design procedure, this problem is eliminated since the digital line is short circuited to ground at both ends and this also provides the filter with greater physical rigidity.

New type of time-varying octave filter

Abstract: Double quadrature-modulation realisations of lowpass and highpass filters were described recently by Saraga. Extensions to these methods lead to the design of an octave filter using one carrier oscillator rather than the two needed for an equivalent filter designed by the technique referred to above. If the output frequencies are not required to be identical to the input frequencies, this filter also uses fewer modulators. By employing two carrier oscillators, any desired bandwidth may be obtained; the bandwidth and passband position may then be independently varied.

Low-pass prototype element values for doubly loaded butterworth filters with 16 through 25 resonators

Abstract: The low-pass prototype element values for doubly loaded Butterworth filters with 16 through 25 resonators have been calculated and tabulated. This material is of interest because of the increased use of these filters.

Optimum distributed-parameter Butterworth-filter type as a limiting case of the optimum Chebyshev approximation

Abstract: It is shown that the optimum distributed-parameter Butter-worth approximation function for a cascade of m LC elements and nunit elements is a limiting case of the Chebyshev type when the value of the passband ripple approaches zero.