Multitone measurement system for linearity investigations of microwave devices

This paper presents a refined multitone measurement system for the robust characterization of nonlinear microwave devices when subjected to broadband multi-tone stimuli. This refined system has the ability to present specific, constant impedances, not only to the baseband (IF) components, but also to signals located around fundamental (RF) and significant harmonic frequencies. Achieving such comprehensive impedance control across wide modulation bandwidths is important and allows the ‘emulation’ of new and specific modes of power amplifier operation, and the subsequent waveform characterization of microwave devices operating in such environments. The modified 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 multitone Class-J impedance environment with optimized baseband impedance environment that interestingly highlights the presence of separate optimum baseband impedance conditions necessary for the reduction of individual Intermodulation (IM) products.

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