Overcoming pHEMT Linearity Dependence on Fundamental Input Tuning by Digital Pre-Distortion

In order to achieve highest possible gain and lowest input reflection coefficient, a conjugate match at the input of power transistors is desired. Unfortunately, as will be shown in this paper, such an input termination is not adequate for best linear performance of pHEMT power transistors operated in class AB. Therefore, these parameters need to be traded off against each other, if the device is used as a stand alone amplification stage. The use of digital pre-distortion allows operation of the transistor at best gain, input return loss, and linearity simultaneously.