Balanced surface acoustic wave ladder filter

The filter includes a piezoelectric substrate and a plurality of surface acoustic wave resonators provided on the piezoelectric substrate. The filter circuit includes input-side balanced signal terminals A1 and A2 connected to an external balanced circuit, output-side balanced signal terminals B1 and B2 connected to an external balanced circuit, at least one first series arm surface acoustic wave resonator S1 connected in series between the input-side balanced signal terminal A1 and the output-side balanced signal terminal B1, at least one second series arm surface acoustic wave resonator S2 connected in series between the input-side balanced signal terminal A2 and the output-side balanced signal terminal B2, and at least one impedance element C1 connected between a first signal line connecting the input-side balanced signal terminal A1 to the output-side balanced signal terminal B1 and a second signal line connecting the input-side balanced signal terminal A2 to the output-side balanced signal terminal B2. The impedance may be provided by a discrete element or by grounding one terminal of a parallel arm resonator. Many other embodiments are described (figs 12, 15, 18, 21, 24).