An enhanced modulated waveform measurement system for the robust characterization of microwave devices under modulated excitation

This paper presents a refined modulated waveform measurement system for the robust characterization of nonlinear microwave devices when driven by broadband multi-tone stimuli. This enhanced system has the ability to present specific, constant impedances, not only to a large number of baseband (IF) components, but also to signals located around the carrier and significant harmonic frequencies. Achieving such comprehensive impedance control across wide modulation bandwidths is critical in allowing the `emulation' of new power amplifier modes and architectures, and the subsequent waveform characterization of devices operating in these complex and often dynamic impedance environments. The enhanced system is demonstrated through a number of applications: firstly the experimental investigation and baseband optimization of a 10W GaN HEMT under nine-tone excitation, and secondly, the emulation of a modulated Class-J impedance environment that interestingly highlights the presence of separate optimum baseband impedance conditions necessary for the reduction of individual IM products.