Showing papers on "Stopband published in 1968"

Low-Pass Filters with Predetermined Phase or Delay and Chebyshev Stopband Attenuation

Abstract: A method is presented for determining the transfer function of low-pass filters whose attenuation shows a Chebyshev characteristic in the stopband and whole phase or delay time can __-_2 for n even be specified independently of the aforementioned attenuation properties The transfer functions may be realized by simple ladder networks In order to obtain, as far as possible, transformerless circuits, the transfer function to be determined has a pole at infinity

Maximally Flat Amplitude Low-Pass Filter with an Arbitrary Number of Pairs of Real Frequency Transmission Zeros

Abstract: The synthesis of a general class of filter with maximally flat passband and Chebyshev stopband attenuation characteristic is presented. The filter has an nth order voltage transfer function with m pairs of transmission zeros in the stopband, where n \geq 2 m + 1 . Butterworth and inverse Chebyshev filters are special cases of this general class with m = 0 and n = 2m + 1 , respectively.

Birefringent Filter for Millimeter Waves

Abstract: A scale model (f/sub 0/ =20 GH/sub z/ of a Solc-type birefringent wave filter for millimeter wavelengths is described. The filter consists of five cascaded identical half-wave plates, or crystals, each composed of an artificial anisotropic dielectric medium with its reference axis tilted at some prescribed angle to the plane of the input polarization. The design and analysis of an individual plate, using Collin's second-order theory of the birefringence of artificial anisotropic dielectrics, and the analysis of multielement filters (filters composed of many plates), aided by Evans' matrix method, are discussed. The experimental filter was tested in the range of 18 to 33 GHz, and its measured performance was found to compare well with the theoretical performance over a major portion of the range of frequencies used in the tests. A synthesis procedure for optimum (equal-ripple stopband) response multielement filters is given, together with tables of plate angles for such filters. In this procedure, the Dolph approximation and the Harris synthesis are combined.

Two Worst-Case Insertion Loss Test Methods for Passive Power-Line Interference Filters

Abstract: The feasibility of two methods for determining the worst-case insertion loss of power-line interference filters is demonstrated. The first method makes use of injection and detection probes (transformers) which introduce an extremely small impedance (L ?50 nH, R ? 3 m?) into the test circuit. The second method does not use injection and detection probes, thus eliminating their problems. Both methods maintain the high Q of the test circuit and permit interfacial resonances to occur between the power-line and filter interface impedances. A conventional filter and a lossy filter were measured by both methods. Large resonances, including a negative insertion loss at 150 kHz, were measured in the stopband of the conventional filter. No resonances were detected in the stopband of the lossy filter. Measurements with the two test methods differed by only a few dB.

Low-Pass, Quasi-Optical Filters for Oversized or Focused-Beam Waveguide Applications

Abstract: A form of Iow-pass quasi-optical filter for millimeter-wave and possibly infrared applications is described which consists of thin layers of dielectric interspersed with arrays of thin metallic strips in a manner similar to an artificial dielectric. Equivalent circuits for filter half-sections of the type used were developed, and formulas and graphs are presented from which image parameters for such half-sections can be obtained. A design procedure is given from which multisection fiters of this type can be designed from low-pass lumped-element prototypes in order to give prescribed transmission characteristics. Some trial designs were worked out and fabricated for use in oversized waveguide, and their responses were computed in detail with a digital computer. Except for some higher order mode effects believed to be due to the standard-size to oversize waveguide tapers which were used, the measured responses were in good agreement with the theory. Stopband edge ratios between 3:1 and 4:1 are possible. Filter structures of this type are amenable to fabrication by techniques similar to those used in integrated circuit technology.

Attenuation Characteristics and Realization of Odd-Order Generalized Inverse Chebyshev Filters

Abstract: Tables of transition bandwidth ratio, zero transmission and minimum attenuation frequencies in the stopband, and element values for two kinds of realizations of odd-order generalized inverse Chebyshev filters with n up to 11 and m up to 3, all using minimum stopband loss as a parameter, are given.