Elliptic cavity couplers for traveling-wave tubes

The elliptic cavity coupler is described as a broad band low-loss coupler for microwave slow-wave structures. This type of coupler is particularly useful in helix-type traveling-wave tubes, but can be adapted for other slow-wave structures as well. Usable bandwidths as wide as 3 to 1 and broad-band insertion losses of less than 1 db have been observed. This type of coupler could readily be utilized with slow-wave structures in the millimeter wavelength region.