A scanning antenna with an antenna element having an evanescent coupling
portion includes a waveguide assembly including a transmission line,
adjacent the coupling portion, through which an electromagnetic signal is
transmitted, permitting evanescent coupling of the signal between the
transmission line and the antenna element. First and second conductive
waveguide plates, on opposite sides of the transmission line, define
planes that are substantially parallel to the axis of the transmission
line, each plate extending distally from a proximal end adjacent the
antenna element, whereby the propagated signal forms a beam that is
confined to the space between the plates and thus limited to a plane that
is parallel to the planes defined by the plates. The signal coupled
between the transmission line and the antenna element is preferably
polarized so that its electric field component is in a plane parallel to
the planes defined by the plates.