S-functions mixer modeling for linearization purposes

In this work, the S-functions behavioral modeling method has been used for the first time under two-tone large signal excitation. For this purpose, a modified S-functions model representation is proposed. The technique is applied to harmonic balance simulations of a doubly balanced diode mixer. The new model is almost five time faster than the circuit model, and still accurately predicts the inband frequency components at IF and RF ports of the mixer. Moreover, the obtained S-functions model coefficients directly allow to calculate a predistorsion signal for mixer linearization purposes. As a result, up to 35 dB suppression of the 3^rd order intermodulation product is achieved for the mixer operating at 1 dB compression point.