Scanned antenna system

Abstract

The invention comprises a feed horn () illuminating a circular flat panel () formed from a high impedance surface structure. By controlling the resonant frequencies of the individual elements of the array, a controlled phase shift profile is applied across the surface of the panel to an incident phase front spherically spreading from the feed antenna so as to reflect that wavefront in a particular direction or impose a certain desired beam shape. The principles are reciprocal so a receiving system can also be achieved or indeed a simultaneous transmit and receive operation can be supported. The phase controlled reflecting plate advantageously performs focussing to the feed and beam scanning or beam shaping. This concept of feed to a phased reflector plate allows the power distribution to be implemented in free space. In addition, the active component at each array element affecting the resonant frequency is a single varactor tuning diode per element with negligible power dissipation since it operates in reverse bias or a MeMs switch network. A further embodiment is described comprising a transmissive panel with phase shifting elements implemented in MeMs technology coupled to each element of the array. Calibration techniques are described that correct for non-systematic errors in the phase shifts on reflection which would corrupt the beam shape and pointing direction in a practical environment. These can be performed repeatedly, interleaved with the radar or communications waveforms passing through the antenna.