Time domain modeling of nonlinear loads

The behavior of an antenna or scatterer when loaded with a nonlinear element can be changed greatly from that observed under linear conditions. In some cases, the nonlinearity causes effects such as the intermodulation products arising from the nonlinear mixing of two frequencies. In other cases, the nonlinearity may be exploited, for example, to reduce late-time ringing on a pulse-excited antenna. A procedure for treating general nonlinear loads is described and illustrated. This procedure is applied using a computer to several specific types of nonlinearities. The treatment within the framework of the thin-wire approximation to the electric field integral equation is developed. As such, the treatment can be applied to the large class of objects modeled by wires. The nonlinear load types that are considered include those with piecewise-linear voltage-current curves (e.g., one or more diodes), a load with a time varying resistance (which permits modulating the scattered fields), and a general nonlinear load represented by specified voltage-current functions.