Characterization of electrical memory effects for complex multi-tone excitations using broadband active baseband load-pull

This paper focuses on multi-tone characterization of baseband (IF) electrical memory effects and their reduction through the application of complex-signal, active baseband load-pull. This system has been implemented to allow the precise evaluation of intrinsic nonlinearity in high-power microwave devices for wideband applications. The developed active baseband load-pull capability allows a constant, frequency independent baseband load environment to be presented across wide modulation bandwidths, and this capability is important in allowing the effects of baseband impedance variation on the performance of nonlinear microwave devices, when driven by broadband multi-tone stimuli, to be fully understood. The experimental investigations were carried out using a 10 W GaN HEMT device, under 9-carrier complex modulated excitation. These confirmed that presenting a wideband baseband short circuit was essential for maximum ACPR suppression together with the minimization of ACPR asymmetry, confirming the importance of proper termination of baseband frequency components when designing DC bias networks.