Intermodulation distortion in fifth-order nonlinear RF circuits/subsystems under multitone excitation

A new analytic approach for modelling nonlinear RF circuits/subsystems, under multitone excitation is proposed. Particularly, the intermodulation (IM) distortion of fifth-order memoryless nonlinear systems is predicted under a randomly phase-modulated multitone excitation. The efficiency of the proposed approach is demonstrated by analyzing standard IM figures of merit such as MIMR and ACPR of a commercial RF power amplifier for different values of input power and number of input tones. The obtained results were compared to third-order models and have shown that restricting the analysis of highly nonlinear systems to third-order nonlinearity leads to optimistic results.