Accurate concurrent simulation of passive and non-linear sub-circuits of a 24 GHz cellulose-based mixer

The design of complex RF devices such as oscillators, amplifiers and mixers requires accurate CAD simulations. Usually these devices are designed by using the “Harmonic Balance” frequency domain technique that calculates the magnitude and phase of voltages (or currents) in a non-linear circuit. The passive part of the sub-system (matching circuits, filters, feeding networks) is simulated exploiting a linear, lumped element equivalent circuit based simulator, usually integrated in the same software suite. In order to improve the overall accuracy of the design method the passive part of the circuit can be optimized by means of EM full-wave simulations. This paper proposes an efficient and accurate approach exploiting the interfacing capabilities of the modern EM software to design an innovative 24 GHz single-balanced diode mixer exploiting cellulose substrate; the ADS Harmonic Balance simulator has been adopted for the non-linear part and the CST Microwave Studio for the passive one.