Field coupling to nonlinear circuits in resonating structures

We present a novel approach to the study of backdoor-coupling of electromagnetic fields to non-linear electronic circuits in resonating enclosures. We measured voltages coupled to a nonlinear loaded wire placed inside a resonator. The resonator was excited by two independent high frequency signals. Correlation analysis was used to distinguish between the influence of line to resonator mode coupling and other effects at low frequencies. We found that high frequency field to line coupling is dominant over low frequency spectral components. However, low frequency line to resonator mode interaction can not be neglected.