Abstract: A surface wave directional detection system for determining the direction in which an electromagnetic wave propagating along a metallic surface is travelling includes a first loop probe and a second loop probe positioned in close proximity to the metallic surface so that the electromagnetic wave induces a signal in each of the loop probes. The two loop probes are separated by a quarter wavelength so that the two signals induced in the probes are out of phase. The first and second loop probes are connected by equal length transmission lines to a quadrature hybrid which generates two output signals that vary in magnitude in correspondence with the direction of travel of the electromagnetic surface wave. The two output signals from the quadrature hybrid are provided to RF detectors, which generate output voltage signals that vary in proportion to the magnitude of the output signals from the quadrature hybrid.

Abstract: This is an automatic direction finder comprising a separately located first and second sensor means for receiving a first and second representation signal from a remote electromagnetic signal source, an error correction loop means connected to the first and second sensor means for nulling the second representation signal in the second sensor means, and an indicator means responsive to the error correction loop means for computing and displaying an off-boresight direction of the electromagnetic signal when the second representation signal is substantially nulled at the second sensor means.