A load-pull approach using multi-frequency harmonic tuners for enhancing PAE and device model accuracy

A load-pull process for characterizing and modeling devices used in switching microwave circuits is presented. The proposed process takes advantage of state-of-the-art Multi-Harmonic Impedance Tuners. These tuners have the ability to control and sweep terminations seen at multiple harmonic frequencies simultaneously, and therefore the true mutual interaction between the different harmonics is always captured during the load-pull process. This is as opposed to the commonly-used single-harmonic impedance tuners where only one harmonic termination can be controlled and swept at a time. Consequently, the set of optimum harmonic terminations obtained from the proposed load-pull process will result in a higher Power Added Efficiency (PAE) than the set obtained by the load-pull process that employs single-harmonic impedance tuners. Moreover, the measurement-based X-parameter model generated during the proposed load-pull process will more accurately predict the performance of the device under real operating conditions. Experimental results of a 0.25 μm GaN device operating at 10 GHz show that an improvement of 11% in PAE is achieved with the optimum harmonic terminations obtained by the proposed approach.