Switchable and Tunable Ferroelectric Devices for Adaptive and Reconfigurable RF Circuits
The exponential increase in the number of wireless devices as well as the limited wireless spectrum, poses significant challenges in the design of future wireless communication systems. Adaptive and reconfigurable radios that can change their frequency and mode of operation based on the unused/available wireless spectrum as well as their surrounding environmental conditions have been proposed to address such challenges. However, currently available RF and microwave circuit components cannot meet the performance requirements, and cost constraints necessary for the commercialization of such systems. This presentation is on the applications of ferroelectric thin film barium strontium titanate (BST), a low loss, high dielectric constant field dependent multifunctional material. An important characteristic of BST is its DC electric field induced piezoelectric and electrostrictive effect. These property is utilized to design intrinsically switchable film bulk acoustic wave resonators (FBARs) and FBAR filters. Switchable ferroelectric based filter banks can significantly reduce size and power consumption of conventional filter banks employed in multi-standard and frequency agile radios. Properties and performance of a number of intrinsically switchable BST based FBARs will be discussed.