Highly Linear and Efficient Asymmetrical Doherty Power Amplifiers with Adaptively Bias-controlled Predistortion Drivers

A highly linear and efficient asymmetrical Doherty power amplifier (ADPA) with adaptively bias-controlled predistortion drivers (PDDs) is represented for 2.14-GHz wide-band code division multiple access (WCDMA) repeater systems. The ADPA shows the extended efficiency range by using unequal saturation powers of the main carrier and peaking cells. The driving carrier and peaking cells are used as the PDDs with the adaptive gate bias control to improve the linearity of the ADPA. To verify the proposed method, two 2-W GaN HEMTs and two 20-W GaN HEMTs are used as the driving and main cells, respectively. For a one-carrier WCDMA signal, the ADPA with PDDs produces an adjacent channel leakage ratio (ACLR) of 51.5 dBc with a total drain efficiency of 27.9% and a total gain of 28.7 dB by adaptively controlling the gate biases of PDDs. For the asymmetrical class-F DPA with PDDs, an ACLR of -38.2 dBc is achieved the total drain efficiency of 37.2 % and a total gain of 26.5 dB.