Large-signal automated load-pull of adjacent-channel power for digital wireless communication systems

A large-signal fully automated load-pull system for characterization of adjacent-channel power for /spl pi//4-DQPSK-based digital wireless communication systems is described. It is demonstrated that the commonly held beliefs that adjacent-channel power for the North American digital system follows a third-order process and that adjacent-channel power for the Japanese digital system follows a fifth-order process are in general not true. Instead, it is shown that adjacent-channel power is a composite of third- and fifth-order nonlinearities, the relative contributions of each being load impedance and device dependent. A simplified power series analysis coupled with spectral decomposition of the digitally modulated source signal is used to characterize conditions under which third-order intermodulation will correlate to adjacent-channel power.