Design of a Fully Integrated Wideband Continuous-Mode Asymmetrical Doherty Power Amplifier in GaN-on-SiC HEMT Technology

In this brief, a novel continuous-mode asymmetrical Doherty power amplifier (CM-ADPA) is proposed. It is illustrated that by applying complex impedance at the power combining node, the continuous-mode impedance condition can be obtained for the main amplifier at both saturation and output power back-off (OBO) to obtain broadband high-efficiency performance. To further expand the bandwidth, an LC-ladder-based lumped Wilkinson divider and impedance inverter are employed for wideband power division and phase alignment between sub-amplifiers, respectively. To validate the proposed topology, a CM-ADPA monolithic microwave integrated circuit (MMIC) is implemented with a highly compact die size of 2.2× 1.8 mm². The fabricated MMIC obtains a 4.4-5.6 GHz bandwidth. Within the operating band, the DPA exhibits a saturation output power of 40.7-41.0 dBm, a saturated drain efficiency (DE) of 53.7%-59.4%, and a DE of 34.0%-43.8% at 8-dB OBO. Under a 100-MHz orthogonal frequency division multiplexing (OFDM) signal, the CM-ADPA also demonstrates good linearity and efficiency. © 2004-2012 IEEE.