Development of a highly linear Ka-band power amplifier using second harmonic injection linearization

We demonstrate the development of a highly linear Ka-band power amplifier (PA) using second harmonic injection at the gate of a pseudomorphic high mobility electron transistor (pHEMT). The second harmonic injection PA (HI PA) achieves a measured gain of 18.5 dB and P_1dB of 23.5 dBm at 28.5 GHz. Compared to the same PA without second harmonic injection, the HI PA has a 3.5 dB higher in P_1dB and a 12 dB improvement in the third-order intermodulation distortion (IM3). To the best of our knowledge, our 2^nd harmonic injection PA is the first demonstration of the technique at millimetre-wave frequencies.