Iterative method using constrained optimization techniques for second-order effects compensation in SAW filters

A novel algorithm for broadband compensation of second-order effects in SAW (surface acoustic wave) filters consisting of one apodized and one unapodized interdigital transducer (IDT) is presented. The method ensures effective compensation of second-order effects even at frequencies close to or equal to zeros of unapodized IDT response. In contrast to earlier methods, inequality constraints are imposed on positions of gaps in apodized IDT. Owing to this feature, this fixed aperture of the IDT can be easily maintained throughout the compensation process. Compensation results are given for a 14 λ aperture SAW TV-IF filter