SPST Acoustic Switch Based on Poled Ferroelectrics

A first demonstration of a single-pole single-throw (SPST) matched acoustic switch operating at 3.6 GHz using phase inversion in ferroelectric bulk acoustic wave (BAW) resonators is presented. Independent control of piezoelectric coefficient in two shunt barium strontium titanate (BST) resonators is leveraged to achieve switching function. The switch presented uses stacked crystal filters (SCF) connected in parallel to produce peak isolation of 41.5 dB in the OFF state and insertion loss of less than 3.7 dB in the ON state. The fractional bandwidth of the ON response is 4.4% with a center frequency of 3.6 GHz. The total active area of the resonators is 1126 um^2. The operating principle of the switch can be extended to any ferroelectric acoustic structure. Furthermore, the switch technology presented herein is suitable for replacing electronic switches for channel selection in acoustic filter banks for radio frequency front ends (RFFE).