Millimeter Wave Cavity Coupling by Quarter-Wave Transformer (Correspondence)

In order to use high mode-order microwave cavities (Fabry-Perot, confocal, or biconical spherical resonators) to achieve either high field intensities or high selectivity with low transmission losses, it is necessary to couple power into the resonaters efficiently. This may be accomplished if the coupling system acts as a transformer matching the lossy elements of the cavity to a source of input power, and if the coupling system has an aperture large enough to make diffraction losses negligible.