| 摘要 |
<p>A surface wave device resonator filter comprises two SPUDTs - single phase unidirectional transducers - or RSPUDTs - resonant SPUDTs - (22, 24) on a piezoelectric substrate, coupled in line for propagation of surface waves via a resonant cavity, or via two cavities (C2, C3) one on each side of a central reflection grating (26), between the transducers. Reflectors (28, 30) at outer ends of the transducers reflect the propagated surface waves for resonance, and can be provided either by reflection gratings, optionally providing a further resonant cavity (C1, C4) between each grating and the adjacent transducer, or by weighting functions applied to the transducers. The weighting functions can comprise withdrawal weighting or apodization. The filter can provide a low insertion loss and other advantages of resonator filters.</p> |
