Effects of the cavity walls on perturbation measurements

Perturbation methods in microwave measurements are addressed. The perturbation formulas will not remain correct when the perturbation object approaches the wall of the resonant cavity. This is a consequence of the effect of the induced charges on the cavity wall when the object approaches it. The author takes this effect into account, and gives modified perturbation formulas which were verified by experimental results. These modified perturbation formulas can be widely used in the measurement of the electromagnetic fields in linear accelerators and other microwave devices. In deriving the formulas, metallic and dielectric spheres are used in perturbing objects