Electric Field Interactions within Finite Arrays and the Design of Withdrawal Weighted SAW Filters at Fundamental and Higher Harmonics.

摘要

In this paper the prediction of electric field interactions in finite length IDT and their use in design of withdrawal weighted transversal filters are discussed in detail. The electric field interactions are accurately determined using the formulation recently described by Smith and Pedler; however, the ensuing simultaneous integral equations are solved in an alternative manner. Calculating the electric fields in this manner results in solutions accurate to at least seven significant digits. With very little additional computational effort, withdrawal weighting design tables can be generated from these electric field solutions. Withdrawal weighting design tables are provided for single electrode IDTs operating at the fundamental and fifth harmonic, and double electrode IDTs operating at the fundamental and third harmonic. The remainder of the paper is devoted to the design and performance of withdrawal weighted SAW filters. The performance of illustrative bandpass filters, operating at 1080 and 936 MHz, is elevated. (Author)