Multi-Band Balanced-to-Doherty Reconfigurable High-Q-Filtering Power Amplifier

This paper presents a novel filtering power amplifier with frequency and mode reconfigurability. The design employs a tunable filtering quadrature coupler as a post-matching power combiner, consisting of four high-Q substrate integrated cavities and contactless tuning. Balanced and quasi-Doherty modes are achieved by exchanging the bias of the sub-PAs and the termination of the output coupler. This method reduces the footprint required by the output filter and minimizes the post-amplification losses. The device was measured across different modes of operation, achieving a 1.43 tuning ratio, up to 40 dBm output power, 62% peak drain efficiency, 47% 6 dB back-off efficiency, and 16 dB gain. Modulated measurements showed good linearity with a -27 dBc adjacent channel power ratio and 54% average efficiency with a 64 QAM signal. The proposed filtering amplifier has applications in highly integrated and high-power radio front-ends.