2.45 GHz ISM-Band RF-PA Demonstrator for GaN-HEMT optimization

In this work empirical results of an investigation aimed at improving GaN-HEMTs for higher frequency operation are presented. Two GaN-HEMT versions with nominal 60W output power and different gate-drain distances (LGD) are inves- tigated using load-pull measurements and in a fabricated power amplifier (PA) demonstrator for the ISM band at 2.45 GHz. The load-pull investigation shows that the optimum impedances in the 2.0. . .3.5 GHz range are very similar for both types of transistors. At 2.45GHz the shorter LGD transistor provides up to 0.7 dB improved output power (POUT ) with 4% improved maximum power added efficiency (PAE). In the PA demonstrator the load- pull results are verified. The transistors show similar frequency response but in general >0.5 dB more saturated output power resulting in a 5 - 10% points improvement in PAE for the shorter LGD transistor.