High linearity MMIC power amplifier design with controlled junction temperature

A combination of techniques for designing high linearity power amplifiers under controlled junction temperature required for space applications is explained and demonstrated. Junction temperature calculation is taken into account in the transistor selection to ensure high reliability operation and is verified by IR measurement. A non linear model is used to accurately predict harmonics generation and intermodulation products. Optimal bias point and loads are chosen to improve the linearity performance. The design method is demonstrated in a C band high linearity GaAs MMIC power. The techniques described lead to an output 1 dB compression point of 26.6 dBm, saturated power 28.9 dBm and PAE 20.9%, with a gain higher than 30 dB. The output third order intercept point (OIP3) reaches levels over 40 dBm with power consumption less than 2 W. The design keeps the critical junction temperature under 108°C and de-rating drain bias of 4 volts is used.