From passive to active radar reflectors and beyond

Classical calibration procedures for radars make use of metallic trihedrals offering high radar cross section (RCS) with limited sensitivity to angular positioning. A specific shape of the trihedral plates is able to flatten further the angular response. So do also Luneberg lenses, having the further interest to be more easily integrated onboard a flying platform for calibrating surface-based radars at long range or training tracking radar operators.But achieving large RCS with such passive devices may face size limitations, which can be overcome through an active setup of a receive antenna, an amplifier and a transmit antenna. The equivalent RCS can be easily controlled by the gain of the amplifying chain. Despite limitations coming from antenna coupling and non-linearity of the amplifier, a wide range of operation can be achieved with such an active device; it becomes even wider when adding capability for amplitude and/or phase modulation.