High efficiency Doherty transmitter with antenna active load modulation

This paper presents a novel Doherty transmitter architecture with antenna active load modulation (AALM) to improve the efficiency of array transmitters. In this paper, the conventional power combiner which limits the performance of Doherty power amplifier is removed, and two power amplifiers (PAs) are directly connected to antenna array. Unlike conventional Doherty architecture, the proposed Doherty PA makes use of the mutual coupling between the array elements to realize two-way power combiner. A transmitter prototype is designed and realized to confirm the proposed architecture. The implemented transmitter works at 2.3GHz, and achieves power gain of 14 dB, saturated output power of 40.5 dBm, and drain efficiency of better than 40% at 6dB power back off.