Control of RF cavity resonance frequency using reflected power measurements

Control of the natural resonance frequency of an RF cavity is challenging due to the variations in the input frequency and the highly nonlinear dynamics involved. The drift of resonance frequency due to disturbances such as temperature variations has to be compensated using a sensor based feedback controller. Additionally, there are limited possibilities for measurement of relevant quantities such as the resonance frequency for the purpose of real-time control due to the extremely high frequencies involved. To address the control problem, this paper presents a nonlinear control scheme that relies on the measurement of reflected power. To this end, a mathematical dynamical model for the cavity is derived, based on which a feedback control scheme using the method of steepest descent is proposed. A Lyapunov stability analysis is presented for the closed-loop system. Simulations are presented to evaluate performance of the proposed controller.