A novel tunable matching network for dynamic load modulation of high power amplifiers

Dynamic load modulation (DLM) has been proposed as a promising technique to improve the backoff efficiency of power amplifier (PA) for wireless communication systems with high peak-to-average power ratio (PAPR), where the design of a tunable matching network (TMN) with wide impedance tuning range and low loss is essential. This work proposes a novel TMN circuit topology that has three main features satisfying closely to the requirements of DLM: able to generate impedance trajectory close to the pure resistance, easy to produce impedance trajectory of a wide tuning range, e.g., with reflection coefficient Γcoverage up to 0.9, and possessing high potential to generate a TMN having low loss especially at high Γ. A TMN circuit for load modulation of 2.14GHz Class-B GaN HEMT PAs based on the proposed topology is built and measured. Static measurements show that, given a properly selected PA, the drain efficiency is improved by 30% at 7.5dB backoff by the load modulation.