Laterally Coupled BST/Sapphire High Overtone Bulk Acoustic Resonators Exhibiting DC Tunable Comb Filter Response with High Q.f Product

SummaryIn this paper, the use of laterally coupled barium strontium titanate (BST) based high overtone bulk acoustic resonators (HBAR) for RF comb filter applications is investigated. Ba
0.5
Sr
0.5
TiO
3
(BST) being in its paraelectric phase, the DC dependence nature is exploited for studying capability of tuning the 2-port device and exploring the enhancements such categories of devices has to offer. The individual resonators having the capability of exhibiting high Q multimode across a wide frequency spectrum, the 2-port device does provide multiple filter passband which are periodically spaced in the measured frequency range of 300 MHz to 10 GHz. The effect, DC biasing has on the filter response is studied and is found that the biasing conditions significantly enhances the Q and the bandwidth (BW) of the filter. Q.f product in the range of 4×10
¹³
Hz (with BW around 65 kHz) with DC tunabilty is reported for one of the filter modes.