A Miniature Reconfigurable Acoustic RF Coupler

We report the first bulk acoustic wave (BAW) radio frequency (RF) coupler and switch utilizing, offering a record small footprint, lower insertion loss than previously reported, and dual coupling and switching functionality. The proof-of-prinicple demonstration leverages paraelectric phase barium strontium titanate (BST). The prototype is 155 μm x 155 μm wherein only 4900 μm2 are mechanically active. Furthermore, the coupler topology presented is electronically reconfigurable via ferroelectric polarization switching offering quadrature and 180° operational modes each with capability to interchange, 180° delay, and switch off signal at coupled and through ports. Experimental verification of the quadrature and switched-off modes is provided. This proof-of-concept article highlights the potential of ferroelectric BAW technology for compact, multifunctional RF signal processing.