Power Conversion in Nonlinear Resistive Elements Related to Interference Phenomena

This paper derives the power conversion in a nonlinear resistive element that is in series with linear resistors. The derivation of the power conversion is analogous to the Manley and Rowe analysis. The power at the fundamental and intermodulation frequencies is defined as the product of the Fourier coefficients of the current and voltage components at these frequencies. In the analysis, the Fourier coefficients are derived as functions of the generator voltage in a lumped-element circuit. To evaluate the Fourier coefficients, the relationship between current and generator voltage is expressed by a power series. The coefficients of the power series are given in the form of polynomials that are valid for nonlinear resistive elements with exponential characteristics. For the investigation of interference phenomena, the equivalence between the lumped-element circuit and a microwave circuit is derived and the generator voltage is related to the power flux density carried by the incident waves intercepted by support structures. The transfer of power at the intermodulation frequencies to radiating structures is then described. Finally, the power at the intermodulation frequencies is evaluated numerically for different power levels in the incident waves. The computed values were verified experimentally.