Load–Pull Characterization Using Different Digitally Modulated Stimuli

A large-signal fully automated load-pull system for characterization of wireless communication systems dependant on digitally modulated signals is described. Load-pull measurements are used to determine optimum load impedances for power gain and adjacent-channel power ratio (ACPR) in a laterally-diffused metal oxide semiconductor stimulated with wideband code division multiple access and orthogonal frequency-division multiplexing signals of various peak-to-average ratios. The results are compared to load-pull measurements of gain and third-order intermodulated products (IMD3), based on a two-tone source signal. The results indicate that the optimum match impedance changes depending on whether a two-tone or a digitally modulated source is used as a stimulus. Furthermore, it is shown that the optimum load impedance for power gain and ACPR is also dependant on the desired output power the device. It is shown, that the change in the optimum load match for the different types of signals is significant enough to warrant further investigation