The design of broadband highly efficient gallium nitride RFPAs used in back-off mode

A requirement for multiple linear RF power amplifiers (RFPA) covering the frequency range 1.5 - 2.8GHz has led to the development of an approach for designing a broadband, linear and highly efficient RFPA operating in output back-off mode (OBO). In addition a 1st pass design flow using NI Microwave Office is described as well as a measurement technique of the input and output impedances of the matching networks prior to RFPA `turn-on'. The effectiveness of this approach is demonstrated using a commercially available discrete 10W GaN on SiC packaged HEMT using a 0.25um process (Triquint T2G6000528) and a 20mil RO4350B PCB dielectric. The fabricated RFPA achieved a peak power of >+40dBm and a peak drain efficiency of >54% over its operating bandwidth. In back off-mode the RFPA achieved an un-corrected linearity of 30dBc and drain efficiency ≥34% when driven with a COFDM 2.5MHz, 9.5dB PAPR modulated signal in the 2.0 - 2.5GHz band.