An Envelope-Tracking Hybrid Field-Circuit Simulator for Narrowband Analysis of Nonlinearly Loaded Wire Antennas

An envelope-tracking hybrid field-circuit simulator is proposed for efficiently analyzing narrowband scattering from wire antennas loaded with nonlinear devices. The simulator models the interactions of fields with wires and lumped elements by coupling and simultaneously solving the thin-wire electric field integral equation and Kirchhoff's equations, respectively. The coupled nonlinear system of equations is iteratively solved by a time marching scheme that represents the fields, voltages, and currents of interest (signals) as a truncated series of harmonic sinusoids (carriers) multiplied with complex-valued time-varying coefficients (envelopes). Unlike time-domain simulators, which sample the signals at a rate proportional to their maximum frequency content, the proposed envelope-tracking simulator samples the envelopes at a rate proportional to their maximum bandwidth; thus, it requires significantly fewer time-steps when solving narrowband problems. Moreover, the envelope-tracking simulator is generally more accurate than its time-domain counterpart because of smaller integration and interpolation errors. Numerical results demonstrate that the proposed simulator improves the tradeoff between accuracy and computation time, especially when analyzing antennas excited by narrowband signals or loaded with weakly nonlinear devices.