Abstract: A surface wave device comprises first and second SPUDT (single phase unidirectional transducer) resonator filters each comprising first and second transducers, which are preferably RSPUDTs (resonant SPUDTs), the resonator filters being the same except that one transducer of the second resonator filter is a mirror image of the corresponding transducer of the first resonator filter to provide a phase difference of 180.degree.. The surface wave device serves as a balun by having an unbalanced signal connection to the first transducers, and a balanced signal connection comprising signal connections to the second transducer of each of the first and second resonator filters. The resonator filters can be arranged side by side on a common piezoelectric substrate.