A Wideband Doherty Power Amplifier With Shunted Reactive Load for Efficiency Enhancement

Abstract

Abstract-A highly efficient Doherty power amplifier (DPA) using shunted reactive load is designed to achieve wideband operation. For enhanced back-off efficiency over the whole bandwidth, a modified load modulation network (LMN), which employs a shunted reactive load at the combining point, was firstly designed to enlarge the effective load impedance of the carrier amplifier at low and high frequencies. Then, the two-point matching approach was employed to design the carrier and peaking output matching networks, which can eliminate the use of offset lines and simplify the LMN. Measurement results show that the designed DPA can deliver an efficiency of 48%-61% at 6 dB back-off power over the frequency band of 2.2-2.9 GHz. For a 20 MHz LTE modulated signal, an average efficiency of higher than 55% can be achieved at an average output power of 37 dBm, while the adjacent channel leakage ratio is below −49 dBc after linearization.

High efficiency Doherty power amplifiers for modern wireless communication systems: A brief review

“…The efficiency is improved by 2-3% with respect to the conventional DPA. A different approach is proposed in [18], where the load modulation network of the conventional DPA is replaced with two quarter-wavelength impedance transformers and a shunted reactive load for efficiency-bandwidth enhancement simultaneously, as shown in Figure 3. The proposed circuit is fabricated and measured for validation purposes.…”