Showing papers on "Stopband published in 1973"

Theory and Design of the Surface Acoustic Wave Multistrip Coupler

Abstract: The multistrip coupler performs the function of a directional coupler for freely propagating surface acoustic waves on a piezoelectrically active substrate. Its operation is analyzed in terms of a transmission line based equivalent circuit. Expressions are obtained for the directionality (transmission and reflection) in terms of the number of coupler strips and the acoustic frequency. Theory and experiment are shown to be in very good agreement. 50-percent metallization is found to give optimum performance; progressive increase in the proportion of the coupler area covered with metal is shown to involve a progressive change from an inline field model to a crossed-field model. Outside a stopband region it is found that a simplified expression for the directionality is valid; this greatly facilitates component design. Design criteria for multistrip components are discussed in terms of substrate and bandwidth requirements. An analysis is included of resistive and capacitative effects on coupling, and problems associated with coupling between dissimilar materials are discussed.

Least-squares monotonic lowpass filters with sharp cutoff

Abstract: A new class of lowpass-filter functions with no finite zeros and a monotonic magnitude response is first derived by using a least-squares norm to minimise the passband attenuation, and these filter functions are then augmented by adding one pair or multiple pairs of j?-axis zeros. The magnitude characteristics of these filters are compared with those of the generalised inverse Cheby?shev filters and are found to be superior, both in the passband and in the stopband.

Properties of Laser Mirrors at Non-normal Incidence

Abstract: For laser mirrors made out of lossless periodic dielectric mutlilayers, having a basic period of two layers (ZnS and MgF2) with different refractive indices and equal effective optical thicknesses, both the reflectivity at the stopband centre and the width of the stopband are calculated as a function of the angle of incidence for radiation polarized perpendicular or parallel to the plane of incidence. The results of computer calculations for mirrors with up to 20 layers are presented in a number of graphs and are discussed in detail. The graphs simplify the design of laser mirrors according to prescribed specifications and make it possible to distinguish between a maximum or a minimum of the spectral reflectivity at the centre of the stopband.

A class of high-pass digital MTI filters with nonuniform PRF

Abstract: A class of digital feed-forward filters is developed, satisfying the requirement of a maximally flat stopband characteristic at zero frequency if the pulse-repetition frequency is modulated. A simple algorithm is given to obtain the filter coefficients. Some properties are summarized.

Electric resonant transfer filter

Abstract: A resonant transfer filter is disclosed for use in a resonant transfer system having a normally open gate which is closed at a sampling frequency for the transfer of energy. The filter incorporates inductance elements and capacitance elements having values determined directly from the transmission function for filters in the resonant transfer mode developed by Cattermole and having a passband width of less than one-half of the sampling frequency. The filter element values are determined by first choosing a prototype filter configuration which approximates the system attenuation requirements and which is suitable for resonant transfer applications. The prototype element values are used as starting values which are revised or altered to decrease the difference between the Cattermole transmission function when computed using the starting element values, and later the altered values, and the ideal transmission function, equaling unity over the passband and zero in the stopband.

Design of a Staggered-PRF MTI Filter

Abstract: : To avoid blind speed phenomena, staggered PRF MTI systems are used in modern radars for detection of high-speed targets. In this report a procedure is presented which considers both the effect of filter weights and the interpulse durations simultaneously. The design goal of this procedure is to yield a filter with minimum variations in the passband and maximum attenuation in the stopband.

On the design of equal ripple delay filters with Chebyshev stopband attenuation

Abstract: This paper is concerned with the design of low-pass filters, without all-pass sections, approximating to a constant group-delay in an equal ripple manner which simultaneously exhibit a Chebyshev type of stopband attenuation. A special type of equal ripple delay approximation, referred to as the constrained Chebyshev approximation, is used to derive the polynomial of odd degree in the denominator of the rational transfer functions of these filters. Then, using the procedure, described by Temes and Gyi, the imaginary axis transmission zeros are determined so that the Chebyshev stopband attenuation of the resulting filter is obtained. The steady-state and transient responses of these filters are discussed and shown to be superior when compared with those for the filters using Chebyshev delay approximants with the so-called standarderror function, especially for larger values of the maximum delay deviation. Tables are also presented enabling directdetermination of the odd-ordered approximants for minimum stopband attenuation.

New Non-Uniform Waveguide Taper Design Yielding Low VSWR and High Rejection

Abstract: A new and improved theoretical method is described for the design of continuous exponential waveguide tapers which may be utilized in designing high pass filters or transitions between different sized waveguides. Comparisons are made between the new approach and commonly published designs. Experimental results from a filter, with a 1% separation between the passband and the stop band, designed by the new method are presented.