Abstract: High amplitude signals reflected back to the horn radiator-receptor in a microwave tank-contents measuring assembly from the interface between a microwave dielectric lens and the tank-contents-atmosphere, which reflected signals mimic returning ranging signals and interfere with detection of returning legitimate ranging signals, are substantially canceled by incorporating in the lens which is plano-convex a thin layer of electrically conductive material in a plane parallel to the plano surface of the lens, said layer being formed from a uniform array of a repetitive pattern of regions containing the conductive material alternating with regions free of said material. One embodiment has an hexagonal array of circular conductive regions while another embodiment has the conductive material in the form of a rectilinear grid.

Abstract: A microwave tank-contents level measuring system is housed within a housing having an open end obturated by a hyperbolically curved convex-plano fluid impermeable solid dielectric lens providing a seal for the tank opening over which the housing is installed while collimating the outgoing ranging signal and focusing the return signal. A separate removable housing cover provides access to the electronic components for service while the tank-opening sealing function of the lens is not disturbed. A transmitting-receiving horn is dimensioned and positioned on the axis of the lens with its effective phase center at the operating frequency coinciding with a focal point of the hyperbolic surface.