Intermodulation Distortion in Fifth-order Nonlinear RF Circuits/Subsystems under Multitone Excitation

A new analytic approach for modeling 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 thirdorder models and have shown that restricting the analysis of highly nonlinear systems to third-order nonlinearity leads to optimistic results.