Millimeter wave microstrip phase shifter

Claim 1

A microstrip reciprocal phase shifter comprising a length of microstrip transmission line dielectric substrate having top and bottom planar surfaces; an electrically conductive ground plane mounted on the bottom surface of said substrate; first and second lengths of electrically conductive microstrip conductor mounted on the top surface of said substrate in longitudinal alignment with each other and spaced a distance apart by a longitudinally extending gap so that one end of each of said lengths of microstrip conductor defines a different end of said gap; a ferrite rod having a rectangular cross-section, a length shorter than the length of said gap and a dielectric constant greater than the dielectric constant of said substrate, said rod being mounted on the top surface of said substrate in longitudinal alignment with said lengths of microstrip conductor and with one of the four sides of the rod abutting said substrate top surface, the ends of said rod being spaced substantially equidistant from the ends of said gap; a dielectric plate mounted on a second side of said rod which is parallel to said first-named rod side, said plate extending the length of the rod and having a dielectric constant which is substantially the same as the dielectric constant of said substrate; a pair of ramp-shaped dielectric waveguide members mounted on the top surface of said substrate at opposite ends of said rod and occupying the spaces between the ends of said rod and the ends of said gap, each of said ramps having a dielectric constant which is substantially the same as the dielectric constant of said rod, a width which is substantially the same as the width of said rod, a planar bottom surface abutting the top surface of said substrate and a downwardly sloping planar top surface extending between the ends of said plate and the ends of said gap; a third length of electrically conductive microstrip conductor mounted on the top surfaces of said ramps and the top surface of said plate and extending between the ends of said gap, said third length of microstrip conductor having the ends thereof electrically connected to said one end of said first and second lengths of microstrip conductor defining the ends of said gap so that said third length of microstrip conductor is serially interconnected with said first and second lengths of microstrip conductor; and means for applying a unidirectional magnetic field along the longitudinal axis of said rod, whereby said other ends of said first and second lengths of microstrip conductor act as the input and output terminals of said phase shifter and electromagnetic wave energy traveling from the input terminal of said phase shifter to the output terminal thereof is shifted in phase by an amount proportional to the strength of said magnetic field.