Assessment of UHF power amplifier linearisation by measurement and simulation

Most communication system simulator programs use complex envelope signal representation. The particular program considered and used in the work is SIGNALS. This general system simulator program works in the time domain. A nonlinear model for inclusion in such a program must operate on time samples of the complex envelope waveforms of the signals. Volterra series is a general nonlinear model. A Volterra series representation can be derived for a subsystem either by circuit theory if the circuit or equivalent circuit is known or by a complex series of measurements on the subsystem, if it is treated as a `black box´. Once a Volterra series representation has been derived the response of the circuit or subsystem to simple multitone signals can be calculated. Volterra series is however of no use as a general nonlinear model for any general signal and it cannot easily be adapted for use in complex envelope based simulator programs. Hence a new nonlinear model had to be derived