Showing papers on "Stopband published in 1972"

Chebyshev Approximation for Nonrecursive Digital Filters with Linear Phase

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.

Waveguide Bandstop Elliptic Function Filters

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.

Multilayer filter based on substitution of herpin equivalent layers in a antireflection coating formula

Abstract: A filter comprises a plurality of thin films of alternating materials arranged in a periodic pattern wherein various symmetrical periods define a stopband and have equivalent indices and thicknesses in the passbands determined by adjusting the ratio q of layer thicknesses within the period, the equivalent indices being chosen to correspond to a known antireflecting coating in the passband, while holding the sum sigma of the effective layer thicknesses constant for each period.

Monotonic low-pass filters with improved stopband performance

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.

Design Equations for a Class of Wide-Band Bandpass Filters (Short Papers)

Abstract: Design equations and experimental data for a class of bandpass filters having up to two attenuation poles at finite frequencies in the stopband are presented. The new designs are obtained by a relatively simple modification of only the end sections of conventional interdigital and half-wave parallel coupled-line filters. Practical realizability constraints generally limit the design technique to wide-band flters.

Weighted interdigital transducers for smoothing of ripples in acoustic-surface-wave bandpass filters

Abstract: The transfer function of acoustic-surface-wave (a.s.w.) bandpass filters exhibits ripples in the passband and sidelobes in the stopband, owing to the finite length of the sin x/x-shaped interdigital transducer used for the filter's impulse-response synthesis. A direct means of overcoming this inconvenience by weighting the interdigital transducer according to smoothing functions, such as those of Fejer and Lanczos, which were developed for the suppression of ripples due to the Gibbs phenomenon, has been devised. The reported results show the effectiveness of this simple approach to the improvement of a.s.w.-filter capabilities.

Computational algorithm for the design of elliptic filters

Abstract: A simple and fast algorithm, based on the simultaneous chebyshev character of the passband and stopband characteristic, is presented for the computation of the transfer function of elliptic filters. The algorithm does not use elliptic functions; rather, a set of nonlinear equations is established and solved using Newton's method. Since useful initial approximations are easy to find, the solution requires only 2–4 iterations. The results are obtained directly in the transformed variable z and hence are immediately usable for computer-aided design.

Design of elliptic function filters using a double-layer RC distributed-active circuit

Abstract: An active double-layer RC distributed circuit is analyzed. Design charts for realizing a second-order transfer function with real-frequency zeros and a pair of complex-conjugate poles are given using the dominant-pole approach. A fifth-order Cauer-Chebyshev-(CC) type low-pass filter with equiripple passband and stopband characteristics is realized using these charts.

Predistorted singly and doubly terminated 0.01 dB-ripple 1st-kind Chebyshev filters

Abstract: Existing synthesis techniques are utilised to develop Tables of low-pass prototype element 'g' values of predistorted singly and doubly terminated first-kind 0.01 dB-ripple Chebyshev-filter networks with up to nine sections. Through conventional frequency-transformation techniques, corresponding bandpass circuits can also be realised. Excessive predistortion (low Q factor) will deteriorate the passband voltage standing-wave ratio, whereas the effects on stopband selectivity are insignificant. Further, the sensitivity of the prototype-element values becomes more acute as the requirement for predistortion is increased. The Tables may be used as a design tool for realising the optimum prescribed insertion-loss characteristics in practical microwave networks where the effects of parasitic component dissipation are critical.