Experimental Investigation of Resistive–Reactive Class-J Mode Using Time-Domain Low-Frequency Active Harmonic Load–Pull Measurements

In this letter, the intrinsic current and voltage waveforms of a power transistor are measured by using a time-domain low-frequency (LF) active harmonic load–pull (LP) system. The measured waveforms are used to study the device’s behavior under loading conditions corresponding to the impedance design space of the resistive–reactive (R-R) class-J modes. From experimental data of a 10-W GaN-HEMT packaged transistor, the device’s drain efficiency and output power have been measured and compared with those expected from the theory of the R-R class-J modes. This letter describes and demonstrates the capabilities of time-domain LF active harmonic load–pull measurements to experimentally study the R-R class-J modes.