Design options for SAW IF filters used in wireless applications

The boom of the wireless industry throughout the world has created a tremendous market for the the components going into the wireless systems. Surface acoustic wave (SAW) filters are one such component experiencing this increased demand. This article describes designs tailored for SAW IF filters used in wireless systems. An overdesigned SAW filter requiring a larger substrate package than necessary will produce disastrous effects on the product's competitiveness. The design approach described in this article involves the selection of the proper eigen function depending on the specification and critical placement of these eigen functions to obtain the desired pass band and stop band characteristics. In addition, the optimal use of transfer functions of both transducers is determined. A table is provided that lists the various options available to optimize the design, depending on the specifications. The approaches published previously using eigen functions are discussed along with their limitations, and SAW IF filters used in wireless applications that benefit from the presented design approach are listed.