Examples of high-speed harmonic load pull investigations of high-efficiency GaN power transistors

This paper presents the capability of an advanced and high-speed, mixed-signal active harmonic load-pull system through measurement activity on AlGaN/GaN transistors. The advantages of the GaN technology which can provide a high power density and a high efficiency are best exploited when the optimum fundamental and harmonic terminations are provided to the transistor. The ultra-high speed of the system, together with its capability to control up to three harmonic impedances, can be used to search for the optimum terminations in a fast and effective manner. This has led to max drain efficiency as high as 90% at 2 GHz, while delivering at the same time 3.5 W of output power for a 1.2 mm device gate width. Further X-band analysis by using the same load-pull system, yields PAE >65 % over the entire wafer.