Design technique for nonlinear phase SAW filters using slantedfinger interdigital transducers

摘要

This paper describes a useful design technique to achieve annonlinear phase SAW filter using slanted finger interdigital transducersn(SFITs) or tapered interdigital transducers which are suitable fornwide-band filters in intermediate frequency stages. A required nonlinearnphase response in the passband can be obtained by changingncenter-to-center distances between input and output SFITs along an axisnperpendicular to the SAW propagation axis. The design is based on anbuilding-block approach in the frequency domain. A nonlinear phase SAWnfilter with a center frequency of 70 MHz and a fractional bandwidth ofnabout 10% is demonstrated on x-cut 112.2° y-propagating LiTaO3n. Because the substrate has a power flow angle of 1.55 degrees,nthe SFIT pattern is tilted along that angle. Good agreement betweenntheoretical and experimental results is obtained