Tunable impedance matching networks on printed ceramics for output matching of RF-power transistors

This work addresses tunable matching networks fabricated on functional thick film layers of Barium-Strontium-Titanate (BST) for RF-power transistors. The deposition of BST layers is performed in a screen-printing process and the fabricated components are patterned by photolithography. Around 2.0 GHz, the insertion loss varies in a range between 0.7 dB and 1.1 dB depending on the tuning state and frequency, transforming 7.5Ohm to 50 Ohm. For verification, the tunable matching network is implemented as the main part of the output matching of three cells of a bare-die GaN HEMT. The transistor is operated in class AB at 2.0 GHz at 15V and 28V drain voltage with a peak power of 36.9 dBm and 40.1dBm along with 47.1% and 41% drain efficiency respectively, which is an improvement of approximately 10%-points in efficiency and more than 6 dB in power compared to previous work.