Harmonic Loadpull

[nealt]

Hi all,

We recently received a Focus harmonic loadpull system and are trying to perform harmonic loadpull on a 10W Cree GaN device. At the moment we are finding it difficult to replicate the approximately 80% PAE currently stated in publications. Has anybody any thoughts on how best to obtain the global maximum in terms of PAE and output power considering that there are 5 independent variables (Source fundamental termination, Load fundamental termination, Load 2nd harmonic termination , Load 3rd harmonic termination and Pout). The brute force algorithm appears not to be an option in the software.
Also, performing fundamental loadpull on its own does not appear to correspond to the optimum fundamental impedance to be used in the harmonic loadpull case (somewhat as expected). Should I perhaps start with maximum output power and tune the harmonics to reduce Ids? Should I start with maximum efficiency from the fundamental loadpull case and tune the harmonics from there?
Considering the order as to which of the variables are manipulated should I start with the fundamental fixed and vary the others independently? Any thoughts as to a methodology to employ in harmonic loadpull to obtain high efficiency and power out would be greatly appreciated.

Thanks,
Neal.