A Compact Intrinsically Switchable Filter Bank Employing Multifunctional Ferroelectric BST

This paper presents an intrinsically switchable and frequency reconfigurable FBAR filter based on ferroelectric barium strontium titanate (BST). Ferroelectric BST possesses electric-field-induced piezoelectricity, enabling the design of voltage controlled thin film bulk acoustic resonators (FBARs). In this paper, a triple band switchable filter bank consisting of three 1.5 stage filters based on BST FBARs is designed, fabricated. The bandpass filters have center frequencies of 1.78, 1.89, and 1.96 GHz and can be selected solely upon the external DC bias voltage applied to each filter. The footprint of the presented filter bank is notably small (an area of 0.055 mm
²
), due to the integration of both switching and filtering functionalities onto a single device.