Switchable band pass BAW filter based on Ba<inf>0.7</inf>Sr<inf>0.3</inf>TiO<inf>3</inf> for C band RF applications

Abstract

This paper presents the design and fabrication of a switchable band pass filter based on barium strontium titanate (Ba 0.7 Sr 0.3 TiO 3 ) 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.

MEMS switching of contour-mode aluminum nitride resonators for switchable and reconfigurable radio frequency filters

“…Currently, frequency tuning beyond a fraction of a filter bandwidth is only achievable by using electronic or MEMS switches to select pre-determined filters within a circuit [7]. Ferroelectric materials such as barium strontium titanate (BST) have been used to demonstrate switching by tuning of the acoustic sound velocity, but have limited Q, high capacitance, and present materials integration challenges [8,9]. As a result, there are currently no known practical approaches for realizing reconfigurable piezoelectric resonators or filters [10].…”

The Effects of Microwave Postgrowth Processing of BaSrTiO3 Thin Films on Their Dielectric Properties

“…This is due to their temperature and frequency stability, low-tuning voltages, relatively low losses, cost, and their fast response [1,2]. Postprocessing of tunable complex oxide thin films became a common practice to establish or improve dielectric properties of these films [3] grown by such methods as metallo-organic solution deposition (MOSD) [4], RF magnetron sputtering [5][6][7][8][9], metal-organic chemical vapor deposition (MOCVD) [10], and others. In addition to improving the crystallinity of the thin films, this postgrowth processing allows augmenting of the oxygen deficiency in the films through various approaches [11].…”