Characterizing nonlinear resonant structures
Dmitry V. Masterov, Sergey A. Pavlov, Alexey E. Parafin · Technical Physics Letters · 2009
A method for the characterization of nonlinear resonant systems is proposed, which is based on the measurement of the transfer coefficient as a function of the frequency at constant amplitude of oscillations in the resonator. In this case, the amplitude-dependent characteristics of the nonlinear resonator, such as the level of losses and the resonance frequency, are the same for all points of the measured resonance curve. This situation can be realized by carrying out the measurements at a fixed output power. The resonance curve measured using this approach, in contrast to the standard amplitude-frequency characteristic obtained at a constant input power, has a Lorentz shape even for a strongly nonlinear system (irrespective of the operative mechanism of nonlinearity), which allows the Q value to be correctly defined (so that it will be constant for the entire measured resonance curve) and determined. The proposed method is illustrated by measuring the characteristics of a superconducting filter in a nonlinear regime.