Analysis of Re-radiated RF Harmonic Disturbance Caused by Integrated Circuit Input Pin Nonlinearity

A wireless system is presented, consisting of an aggressor antenna operating at 1.84 GHz, a victim antenna operating in the 5 GHz WiFi band, and a nonlinear integrated circuit (IC). The aggressor RF disturbance signal is picked up by the IC, the third harmonic frequency is generated due to nonlinear distortion at the IC pad, and it is re-radiated to the victim. The IC nonlinearity is characterized by measurements, and it is modelled using a voltage-dependent RC term obtained from circuit simulations, with good correlation between model, simulations, and measurements. A full 3D-FEM simulation of the wireless system and the IC model are used in the top-level simulation. A significant interference signal in the band of the victim antenna is observed. The speed-up factor of the IC model in the large-signal simulation is in the order of 100 times.