300W Dual Path GaN Doherty Power Amplifier with 65% Efficiency for Cellular Infrastructure Applications
Use of advanced signal processing techniques has a potential of pushing the envelope in improving the performance metrics of RF circuits. In this work, digitally-assisted, dual-path Doherty architecture is used to improve the efficiency of high power GaN PA designed for infrastructure applications. Optimized phase delay adjustment between Carrier and Peaking PA paths, and improved gain profile of Peaking PA path (achieving dynamic power splitting) yields higher efficiency of operation with tradeoff of degraded linearity. Segmented-Digital predistortion approach is used which improves the linearization while keeping the model complexity low. For hardware validation, NXP’s 300W asymmetric GaN Doherty PA operating across 2535–2635 MHz band is used. Using dual-path GaN Doherty PA operating at 2.55GHz, for single LTE20 carrier 65% efficiency is achieved at the average output power of 47.5dBm with linearity better than -56dBc, which is an efficiency improvement of 3–5 percent points across the band (2535–2635 MHz) when compared with conventional single-path GaN Doherty PA. In addition, linearity performance of waveforms with instantaneous bandwidth of 60 MHz and 100 MHz is provided (Drain Efficiency=63.4/62.3%; Linearity=-53/-48 dBc respectively).