An enhanced phase shifted transmitter based on 2ndHT GaN-PAs with energy recovery circuit

Phase Shifted Transmitter (PST) operates without mixers and allows the direct generation and transmission of any envelope and phase-modulated signals. Besides of maintaining all the benefits of the standard PST architecture, the solution here proposed allows the integration of an energy recovery circuit capable to boost the efficiency of the overall transmitter up to 50%. The theoretical analysis of the novel architecture is reported highlighting the relevant differences and advantages with respect to the standard approach. The required key RF blocks have been realized in hybrid technology employing GaN HEMT devices and Schottky diodes to design the power amplifiers (PAs) and the energy recovery circuit, respectively. In particular, the former have been designed by exploiting the 2^nd harmonic tuning approach. Experimental results on the PAs have shown an efficiency higher than 70% at 39 dBm of output power with an associated gain greater than 11 dB at 2GHz. Moreover, a draft experimental validation of the overall system is also reported showing promising performances.