In this paper, the general formulas which relate the analytical expression for the fundamental frequency signal and the in-band distortion components to the order of a power amplifier (PA) polynomial modelare derived. A robust method for estimation of coefficients of nonlinear model is presented and applied to a particular amplifier in an impulsive noise environment. Such nonlinear models are used for analyzing performances of the transmitter and developing digital predistortion linearizers. Modelled and experimental results are presented to validate the argument. A very good agreement between modelled and measured results is achieved.