Three-harmonic time-domain load-pull measurement system with the 40-GHz maximum third order harmonic frequency for nonlinear device characterization

A three-harmonic time-domain load-pull measurement system, which operates up to 40 GHz for the highest harmonic, is demonstrated. The system uses a 50-GHz nonlinear vector network analyzer. The load generator is comprised of three synchronized signal generators and a harmonic combining network using cascaded broadband diplexers, as well as an optional mechanical tuner. Load-pull measurements are validated up to 16-GHz fundamental frequency by comparing the source impedance measured using a network analyzer and the Γopt measured using the load-pull measurement system. Measurements of a 0.25-μm GaN HEMT at 6-GHz fundamental frequency and a 0.5-μm InP HBT at 10-GHz fundamental frequency suggest that the power efficiency of amplifiers using the devices can be improved by 3-6% using the measurement results.