Selectable performance filter

Abstract

RF programmable SAW filters achieve selectable filter performance by providing tunable input and output interdigital (IDTs) with different synchronous frequencies and substantially reduce electromagnetic interference (EMI) associated with RF signals not of interest. The RF programmable SAW filter includes tunable input and output IDT's, with the input and output IDT's having different input and output IDT synchronous frequencies. The input signal is divided into multiple output signals along multiple signal paths that are applied to an input tap weight network wherein the amplitude of each output signal may be varied individually. The individually weighted signal paths are then applied one each to individual IDT input electrode fingers in a means for IDT input, which is characterized by a synchronous frequency F. The IDT input means generates an acoustic wave that propagates to a means for IDT output, which is characterized by a synchronous frequency F, where Fand Fare not the same. The electrical signals generated in the IDT output means are processed through an output tap weight network, and the output signal is formed as a weighted sum to provide a selectable center frequency, a selectable bandwidth, a minimum insertion loss, a maximum sidelobe rejection level and a selectable filter transfer function, or phase/magnitude profile. RF programmable SAW filters, RF partially programmable SAW filters, RF fully programmable SAW filters and a method for making programmable RF SAW filters are provided.