Coaxial transmission line crossing

Abstract

A crossover for a microwave circuit constructed within a plate includes intersecting square-shaped coaxial transmission lines, each of which is formed by machining channels within the plate, with square-shaped central members disposed along the axes of the channels and insulated from the side walls thereof. The plate is made of an electrically conducting material to provide for the structure of a coaxial line of which the members thereof have a rectangular, preferably square-shaped, cross-section. At the intersection of two of the transmission lines, a septum is placed, the septum being parallel to the plane of the plate. The septum is located halfway between the top and the bottom portions of the channels. An inner, or central, conductor segment of reduced cross-section is slung beneath the termini of rod-shaped members in one line so as to pass beneath the septum and to provide for the structure of a coaxial transmission line beneath the septum. A corresponding conductor segment is located above the septum and disposed on termini of the central conductor members of the other one of the intersecting transmission lines. A cover encloses the channels of the plate. The crossover segment of the second transmission line passes between the cover and the septum to provide the structure of a coaxial line between the cover and the septum. Matching structures in the form of a miter at the end of each center conductor reduces reflection at the junction of the segment at the septum with the balance of the transmission line. The foregoing segments are approximately one-quarter wavelength of the microwave frequency.