Tunable multiband power amplifier using thin-film BST varactors for 4G handheld applications

A new methodology for multiband tunable power amplifiers (PA) using barium-strontium-titanate (BST) varactors is presented. A prototype tunable power amplifier has been developed and its performance is evaluated in context of the upcoming 4G scenario which demands for multimode/ multiband power amplifiers capable of operating over multiple frequency bands. The tunable PA requires two tuning voltages at the output matching network as well as an additional tuning voltage for a novel tunable 2 nd harmonic termination. The PA is continuously tunable from 1700 to 2300 MHz, covering multiple bands. Tunable PA measurements with LTE signals show a maximum gain of 27 dB with Pmax of 24.1 dBm and an EVM of 6% using BST varactors having Q-factors not more then 30 at sub-2 GHz frequencies.