Surface-acoustic-wave filter

A SAW bandpass filter includes parallel arms 62-64 each containing a first SAW resonator R1, R3, R5 having a predetermined resonance frequency (frp), and a series arm 61 containing second SAW resonators R2, R4 having a predetermined resonance frequency (frs) approximately equal to or higher than the antiresonance frequency of the first SAW resonator (fap). The resonators have reflectors 132, 133 on both sides of their interdigital electrodes 131. These reflectors, however, can give rise to an undesired ripple in the pass band. In the invention the ripple is substantially eliminated by selecting the thickness (i.e. the weight) of the electrode films so that the ripple is pushed out of the pass band. For instance, with aluminium electrodes the thickness should be 0·06-0·09.λp, where λp is the finger pitch.