Further Clarification on the Use of Bessel Function Expansion to Approximate TWTA Nonlinear Characteristics

The Bessel function expansion has been used [1] to approximate the TWTA nonlinear characteristics to assist in the evaluation of intelligible crosstalk between FDM/FM carriers using the Shimbo-Pontano method [2]. In particular, the arbitrary constant α was chosen to be in the range of 100-1000. This correspondence presents a further theoretical clarification on the selection of suitable values for α, which was briefly explained in [3]. In this analysis, it is shown that the suitably chosen values for α (as given in the main text) cannot be large (roughly,
\alpha \leq 1.6
).