Patent ID: 7675388

Claim:
A duplexer comprising: a first filter including at least a first capacitor and at least a first acoustic resonator coupled to the first capacitor, the first filter configured to be coupled to an antenna, and the first acoustic resonator including: a first electrode; a second electrode; a first barium strontium titanate (BST) dielectric layer disposed between the first electrode and the second electrode, wherein a DC (direct current) bias voltage is applied across the first BST dielectric layer to switch on the first acoustic resonator with a resonant frequency; and a second filter including at least a second capacitor and at least a second acoustic resonator coupled to the second capacitor, the second filter also configured to be coupled to the antenna, and the second acoustic resonator including: a third electrode; a fourth electrode; a second BST dielectric layer disposed between the third electrode and the fourth electrode, wherein no DC bias voltage is applied across the second BST dielectric layer to switch off the second acoustic resonator.