Switchable and Tunable BAW Duplexer based on Ferroelectric Material.

A switchable and tunable BAW duplexer for RF applications is presented in this paper. The fabricated BAW duplexer was built on sapphire substrate using solidly mounted resonators (SMR). A metalorganic solution deposition (MOSD) technique was used to form resonators with barium strontium titanate (BST) thin film and six layers of silicon dioxide and tantalum oxide as a Bragg reflector. By applying DC bias, the BST thin film shows an electrostrictive effect, and the two filter paths of the BAW duplexer switch to band pass response with center frequencies at 4.635 GHz and 4.878 GHz and show a bandwidth of 119 MHz and 154 MHz for transmitting (Tx) and receiving (Rx) filters, respectively. Further, the BAW duplexer was simulated using circuit model, Butterworth-van-Dyke (BVD) model, and EM model. The simulated results are in agreement with the measurements and show a response of band pass filters at center frequencies of 4.633 GHz and 4.876 GHz for Tx and Rx, respectively.