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 propagating device electrically connected to the transceiver and arranged to propagate a transmitted electromagnetic signal towards a surface of the product contained in the tank, and to return echo signals resulting from reflections at impedance transitions encountered by the transmitted electromagnetic signal, including a surface echo signal resulting from reflection at the surface, back to the transceiver; processing circuitry connected to the transceiver and configured to determine the filling level based on the surface echo signal; and a bottom reflector arranged at a bottom of the tank. The bottom reflector comprises a plurality of phase-modifying structures, each being configured to modify a phase of the transmitted electromagnetic signal and to reflect phase-modified electromagnetic signals, wherein the plurality of phase-modifying structures are arranged in such a way that phase-modified electromagnetic signals being reflected by different phase-modifying structures interact to provide destructive interference towards the propagating device.