A multi-IDT input tunable surface acoustic wave filter

Tunable surface acoustic wave (SAW) filters (TSF) have been widely used in the wireless telecommunication systems. A prototype of a multi-IDT (interdi gital transducer) input TSF has been developed. The device consists of 11 I DT paralleled in the SAW propagation path. Different SAW filter configurati ons are realized by selecting or combining various IDTs, resulting in the t unability of both center frequency and 3 dB bandwidth. The center frequenci es of the SAW filter range from 126.8 to 199.1 MHz; the 3 dB bandwidths ran ge from 15.2 to 58.9 MHz. Impedance weighting methods have been applied. Th e passband ripple has been reduced from 6.44 to 1.37 dB after resistance we ighting.