Switchable band pass BAW filter based on Ba0.7Sr0.3TiO3 for C band RF applications

This paper presents the design and fabrication of a switchable band pass filter based on barium strontium titanate (Ba_0.7Sr_0.3TiO₃) thin film materials. This filter is designed and fabricated as a solidly mounted resonator (SMR) using spin-on metal organic solution decomposition. It consists of six film bulk acoustic resonators (FBARs), two series and four shunt. Without voltage biasing, there is no frequency switching and the filter has shown capacitive response of return loss S11 at -3 dB and insertion loss of -21 dB. By applying 10.8 dc voltage to the six resonators, the filter has exhibited band pass response at 4.67 GHz with 150 MHz band width and insertion loss of 3.8 dB and shown an agreement between the simulation and measurement results.