Coupled Surface-Acoustic-Wave Resonators

Surface-acoustic-wave resonators are now well established as one-pole, narrowband filters in the frequency range 30 to 1000 MHz. 1,2 Recent work 3-10 has shown that multipole filters can be formed by coupling several resonators. In general, multipole filter responses can be synthesized by using one or more of the three established coupling mechanisms: (i) collinear acoustic coupling,3-5 (ii) acoustic directional coupling (multistrip coupler),6-7 or (iii) electrical coupling using transducers. 8-10 Examples of two-pole resonator filters using the three types of cavity-coupling mechanisms are presented in Fig. 1. In each configuration, 1447 kWWWVCT 1W W S N W W3 K WW M WVW kWWWWWN kWWWWWI LWWWWWN NVVWWVVW] KWWWWWI kWWWWWN KWWWWWI kWWWWWH LWWWWWM KWWWWWI KWWWWWN LIE LTE Hi' KWWWV^ "If J KWWWWWI kWWWWWN LWWWWvW KWWWWWI kWWWWWN LWWWWWN KWWWWWI LWWWWWN r W W W W W3 J1 LWWM WWW c L KWWWWWI tWWWWWM J] kWWWWWN KWWWWWI KWWWWWH LWWWWWM KWWWWWI [wwwww^i "L KWWN WWW K V VW WWV M KVWM WW W IWWWWWM kWWWWWi kWWWWWS LWWWWWM KWWWWWI KWWWWWI kWWWWWN KWWWWWI KWWWWWI kWWWWWN KWWWWWI