Tunable lumped-element-filter for RF power applications based on printed ferroelectrics

This work addresses center frequency and bandwidth tunable filter for implementation in RF base-station front-ends. The filter is fabricated using functional thick-film layers of Barium-Strontium-Titanate (BST). The deposition of BST layers is performed locally in a screen printing process. The fabricated varactors have a Q-factor around 40 at 1 GHz, a tunability larger than 50% and a measured IP3 higher than 65 dBm. The filter is designed to cover typical GSM frequencies from 700 MHz to 960 MHz and 60 MHz to 100 MHz bandwidth. The simulated insertion loss is around 2.2 dB and 3.0 dB, depending on the center frequency and bandwidth. Measurements of the filter reveal an insertion loss of 6 dB to 9 dB which is at least 4 dB higher than predicted by simulations.