Moments Based Computation of Intermodulation Distortion of Mixer Circuits

The main figure of merit used to evaluate nonlinear distortion is the third order intercept point (IP3). Traditional methods for obtaining IP3 are either simulation based and suffer from a high CPU cost due to the large number of tones present, or are based on analytical methods which are not suitable for arbitrary topologies and complexities. In this paper, a method based on the computation of the circuit moments is presented for directly obtaining the IP3 of a circuit. The new method is general for all topologies and circuit complexities, and is very accurate and CPU efficient. Furthermore, it is suitable for circuits such as mixers which contain switching behavior and large nonlinearities outside the signal path.