Patent ID: 7489213

Claim:
A surface acoustic wave (SAW) filter comprising: a transducer comprising an acoustic track to pass a SAW, a center frequency of the filter exciting the SAW; wherein the acoustic track comprises cells along a longitudinal direction of the acoustic track, each cell comprising electrode fingers, the cells comprising different cell types, where a cell type is defined by a connection sequence of electrode fingers in a cell; wherein at least some of the cells are functional cells, each functional cell for exciting and/or reflecting the SAW; wherein the functional cells comprise at least one functional cell having a length that corresponds to a phase shift of 2πn of the SAW where n is an integer; wherein the functional cells comprise at least two functional cells of a same cell type; and wherein the functional cells are configured so that, when the SAW passes through at least two functional cells that have different cell types, the SAW experiences different phase shifts of φ and φ′.