Abstract: A microwave flaw detector system and method are disclosed which include the use of a pair of parallel strip transmission lines which are located a parallel spaced distance from the surface of the test, or work, piece. The strip transmission lines are capable of supporting first and second orthogonal transmission modes, and means are included for supplying the same with a signal of the first mode. The strip transmission lines are located adjacent the surface of an object to be tested for flaws, and may be moved relative thereto for scanning the surface thereof for flaws. The test piece constitutes one ground plane for the pair of current-carrying strips within which return currents flow in a direction opposite to the strip currents. When a surface flaw on the test piece perturbs the ground plane current in the test piece under one strip, some of the power in the test piece is converted to a second mode orthogonal to the incident-mode current.

Abstract: An antenna comprises the combination of a biconical-horn and a circular waveguide. The major symmetry plane of the horn is horizontal and the horn describes a figure of revolution about the major axis of the circular waveguide. Coupled to the one wall of the horn with its axis perpendicular to the horizontal symmetry plane of the horn is the circular waveguide. A TEM coaxial port on the vertical axis of the horn is provided at the vertex of the cone forming the surface of the biconical-horn. Two orthogonal-ports are provided in the circular waveguide with two respective TEM transmission lines extending from within the circular waveguide outside of these ports to provide at their outputs the TE.sub.11 modes.