Generalized Truncated Time Functions for SAW Filter Synthesis

摘要

Truncated time functions with good sidelobe behavior in frequency domain are often used in the synthesis of SAW filters. A wide range of design requirements for sidelobe levels and shape factors demand an exhaustive range of efficient truncated time functions to suit each specification. There are several time functions described in the literature which are used for SAW filter synthesis. Among them, the cosine series functions offer stopband rejection and mainlobe width which increase with the increase in the order of the series. A general set of new truncated series is described in this paper, which facilitates derivation of an innumerable number of truncated time functions to obtain a range of sidelobe levels and mainlobe widths in addition to those obtained by the cosine series. As an example, a set of truncated time function series is derived from the generalized function series and frequency response plots of the series up to the third order are given. The sidelobe levels and mainlobe widths of the series are different from those due to cosine series, adding further flexibility in designing SAW filters.