Circulator in a stripline microwave transmission line circuit

摘要

A circulator in a stripline microwave transmission line circuit that is disposed in a pattern of printed circuit conductors between a pair of facing dielectric material circuit boards having conductive ground planes on their exposed broad faces. The circulator includes three printed circuit center conductors disposed between the two boards in a symmetrical array extending radially from a circular hole aligned through the two boards; a conductive foil having a central portion concentrically disposed within the perimeter of the hole and three radially projecting arms arranged in contact with the radially extending center conductors; a pair of pucks of ferrite material of a predetermined size selected to provide circulation of microwave signals of a predetermined wavelength concentrically disposed in the hole on opposite sides of the conductive foil; a pair of conductive covers in contact with the ground plane conductors and extending to completely enclose the ferrite pucks within the hole; a pair of magnets disposed on opposite sides of the boards in axial alignment with the ferrite pucks for providing a magnetic field through and normal to the central portion of the conductive foil; magnetically permeable material contacting the magnet and concentrically disposed for providing a closed magnetic loop for shielding the circulator; and a pair of high dielectric material rings disposed in the holes for radially enclosing the pucks and making contact with both the pucks and the surfaces of the board defining the holes, wherein the radial thickness of each ring is one- quarter of the predetermined wavelength for impedance matching the circulator to each of the transmission lines defined by the center conductors and the ground planes. The conductive covers are dished to have respective central portions that are recessed below the ground planes to broadly contact the ferrite pucks and maintain the ferrite pucks in contact with the conductive foil.