Intermodulation interception points of nonlinear circuits connected in cascade

The influence of the input and output matching conditions on the third order intermodulation intercept points (IP3) of two amplifiers connected in cascade is investigated. Here we show that in order to get high convergence between prediction of the IP3 by the conventional formula and by circuit simulation, high matching levels must be given. Return losses of -10 dB, usually used to describe acceptable matching level in radiofrequency (RF) and microwave circuits are not enough to forecast the nonlinear behaviour by wide employed engineering formula of amplifiers connected in cascade. Also, it is shown the type of the matching networks can play an important role on the linearity of amplifiers connected in cascade.