Moments-Based Computation of Intermodulation Distortion of RF Circuits

Linearity is one of the main design requirements for RF circuits, and one of the main figures of merit used to measure linearity is the third-order intercept point (IP3). However, obtaining the IP3 using traditional harmonic balance simulation requires multitone inputs, which significantly increases the computational costs. On the other hand, analytical approaches based on obtaining closed-form expressions for Volterra functional series are too complex to be fully automated for arbitrary circuit topologies. In this paper, a method for the numerical evaluation of the Volterra kernels required for obtaining the IP3 is proposed. The proposed approach is applied directly to the harmonic balance equations and is thus independent of circuit topology and type of nonlinearity. Furthermore, it is shown that the computation cost of this approach is significantly less than a harmonic balance simulation.