1. A method of predistorting signals using an augmented forward twin nonlinear two-box model to compensate for a nonlinear power amplifier, comprising the steps of accepting an input signal, x in — LUT — F ; the input signal being a digitized signal; predistorting the input signal using values in a look-up table of values computed from a memoryless polynomial to produce a first predistorted input signal, x in — Poly — F ; and predistorting the first predistorted input signal, x in — Poly — F , in accordance with a memory polynomial function including cross terms to produce a second predistorted input signal, x out — Poly — F , for input to the nonlinear power amplifier, the memory polynomial function being characterized by the relation: x out _ Poly_ F ( n ) = ∑ j = 0 M 1 ∑ i = 1 N 1 a ij · x in_Poly _F ( n - j ) ·  x in_Poly _F ( n - j )  i - 1 + ∑ j = 0 M 2 ∑ i = 2 N 2 ∑ i = 1 L 2 b ijl · x in_Poly _F ( n - j ) ·  x in_Poly _F ( n - j - l )  i - 1 + ∑ j = 0 M 3 ∑ i = 2 N 3 ∑ i = 1 L 3 c ijl · x in_Poly _F ( n - j ) ·  x in_Poly _F ( n - j + l )  i - 1 ; wherein x in — Poly — F and x out — Poly — F are input and output waveforms of the output polynomial, respectively, N 1 , N 2 , and N 3 are the nonlinearity orders of aligned, lagging and leading polynomial function terms, respectively, M 1 , M 2 , and M 3 represent memory depths of the aligned, lagging and leading polynomial functions, respectively, L 2 , and L 3 represent lagging and leading cross-terms orders, respectively, a ij , b ijl , and c ijl are the coefficients of the aligned, lagging and leading polynomial functions, respectively.