APPARATUS FOR TRACKING RESONANT FREQUENCY

摘要

An apparatus for tracking the varying resonant frequency of an electrically resonant structure, characterised by: a variable frequency oscillator providing an excitation signal of a variable frequency encompassing the possible resonant frequency range of said resonant structure, a bidirectional RF transmission line connecting said variable frequency oscillator and said resonant structure, said transmission line incorporating a directional coupler which generates a directional coupler signal proportional to the reflected signal from said resonant structure, said directional coupler signal being conditioned by a processor to provide a feedback signal to the input of the variable frequency oscillator, such that the mean frequency of said excitation signal is caused to continuously track the varying resonant frequency of said resonant structure. Typically the tracking of said varying resonant frequency involves at least two functions, a first search function for initially searching the possible resonant frequency range of said resonant structure and, once resonance of said resonant structure is established, a second following function for following said variable resonant frequency as it varies as a function of time.