Nonlinear compensation using orthogonal inverses: broadband inputs and robustness issues

The performance of many analogue and digital signal processing systems is limited by nonlinear distortion which can be reduced by post-distortion compensation. Power series inverse based nonlinear compensation suffers from various limitations resulting from the coupling between the non-orthogonal elements used to represent the nonlinearity. This paper is concerned with an orthogonal nonlinear compensation technique. The technique is based on the removal of specific terms in the orthogonal series, overcoming some of the problems of power series inverse based compensation methods. We illustrate the advantages of the orthogonal inverse based compensation technique with examples involving both narrowband and broadband inputs. We then investigate the robustness of the orthogonal compensation approach to deviations in input signal properties