High power active harmonic load-pull system for characterization of high power 100-watt transistors

This paper presents, for the first time, a waveform/time-domain measurement system with active harmonic load pull that is capable of characterising 100W LDMOS devices. In order to achieve the required high-power capability the measurement system employs a new bias-tee design (Benedikt and Tasker, 2002) coupled with broadband impedance transformers (Aboush et al., 2004). The unique characteristics of the high-power bias-tee increases the performance of the measurement system up to 12GHz, 100W CW for the RF channel, and 100V, 10A for the DC channel. The broadband impedance transformers are embedded within the time-domain measurement system and dramatically reduce the power levels required from the active load-pull system for device characterization. This system is demonstrated through the successful characterisation of a 100W LDMOS device, where only 120W of active load-pull power is required to emulate the low impedance optimum load. This represents a remarkable reduction in required power from the impractically high 688W needed in a conventional system with no impedance transformation.