Multitone power and intermodulation load-pull characterization of microwave transistors suitable for linear SSPA´s design

In this paper, an experimental load-pull characterization of microwave transistors operated under N-tone-excitations (2⩽N⩽32) is presented. Such characterization is very useful to investigate the linearity of high-power amplifiers via intermodulation distortion analysis. All the measurements were carried out using a newly developed multiline measurement system which uses an arbitrary waveform generator (AWG) to generate the spectrum of any N desired tones and a microwave transition analyzer (MTA) as a vector receiver. The measured intermodulation rejection (IMR) behavior, as the number of tones increases, is compared with previously published theoretical results. Constant output power contours and IMR contours in the Γ_L (f₀) plane for different number of tones are presented and discussed. The dependency of the IMR on the biasing conditions and the carriers´ phase distribution is also investigated