Multi-harmonic load-pull: a method for designing MESFET frequency multipliers

A multiharmonic active load-pull system is used to characterize transistors in their nonlinear region of operation. The harmonic tuning for optimum loads is done independently from the fundamental tuning. Load-pull measurements on a MESFET have been performed at the fundamental (f₀), second harmonic (2f₀ ), and third (3f₀) harmonic. The active multiharmonic load-pull method presented is applied to the design of a frequency doubler and frequency tripler for a quasi-class B bias point. The maximum of second harmonic generation corresponds to a short circuit at the fundamental Z_L (f₀). The third harmonic generation is optimum for an impedance Z_L (f₀) close to an open circuit. Harmonic generation processes seem to be independent of the harmonic loads. This information for a series of bias points helps to design high-performance frequency multipliers