US Patent 7636059 Impedance matched guided wave radar level gauge system

A radar level gauge system, for determining a filling level of a product contained in a tank, the radar level gauge system comprising: a transceiver for generating, transmitting and receiving electromagnetic signals; a probe electrically connected to the transceiver at a probe-transceiver connection and arranged to extend towards and into the product contained in the tank, for guiding a transmitted signal from the transceiver towards a surface of the product, and for returning a surface echo signal resulting from reflection of the transmitted signal at the surface back towards the transceiver; an impedance matching device arranged to extend along a portion of the probe inside the tank, an extension of the impedance matching device, in a direction perpendicular to the probe, decreasing along the portion of the probe with increasing distance from the probe-transceiver connection, to thereby provide impedance matching between an impedance of the probe-transceiver connection and an impedance of the probe; and processing circuitry connected to the transceiver for determining the filling level based on the surface echo signal.