Microwave waveguide seal assembly

Abstract

A microwave waveguide is presented which includes a gas tight seal which provides pressure isolation between two portions of the waveguide. In accordance with an important feature of this invention, an upper flange includes a threaded axial opening for receiving and retaining a threadably mated dielectric filling material. If the thread pitch is small relative to the signal wavelength, the threaded section has essentially the same electrical characteristics as a smooth waveguide. The resulting structure provides an economical and practical method of retaining a solid dielectric filling material in a waveguide against high pressure without changing the effective diameter of the waveguide. In accordance with another feature of this invention, a novel high pressure seal is provided between the upper and lower flanges in the area surrounding the threaded axial opening. This high pressure seal comprises the capture of a membrane or disk of soft material, preferably polytetrafluoroethylene (PTFE), in an essentially constant volume, closed cavity. The PTFE thus acts like a compressed fluid and provides for high pressure gas operation in hostile environmental conditions with reduced failure relative to prior art PTFE (or like materials) to metal sealing arrangements. In accordance with still another feature of this invention, the sealing membrane or disk described above is rendered thin (on the order of 0.002 to 0.020 inches) and includes outer dimensions which are larger than the outer dimensions of the waveguide. The disk or membrane is thin enough so as not to impact the electrical characteristics of the waveguide.

Dependencies are inferred from the claim text.