PROGRAMMABLE SURFACE ACOUSTIC WAVE (SAW) FILTER

摘要

A novel programmable SAW filter (100) with switchable multi-element interdigital transducers (IDTs) controlled by a microprocessor or a computer is provided that realizes the tunability of both center frequency and 3dB bandwidth of the SAW filter (100). As an example design, the center frequency of the SAW filter (100) provided in a dual in line package (102) ranges from 126.8 MHz to 199.1 MHz, while the 3 dB bandwidth ranges from 18.8 MHz to 58.9 MHz. The multi-input configuration increases the programmability of the device and improves insertion loss. A matching network further improves insertion loss level and stopband attenuation. A resistance weighting method improves in band ripple with the passband ripple being reduced from 6.44 dB to 1.37 dB. The programmable SAW filter (100) simplifies the device structure and fabrication process by shaping frequency response without apodization, and by eliminating the tap weighting and summing circuits, resulting in smaller devices and lower costs.