Multibeam array using Rotman lens and RF heterodyne

An RF heterodyne technique applied to a Rotman lens to reduce the size of the beamforming network for an airborne antenna operating at L-band is presented. An example is given for a multibeam transmit array with 48 columns of radiating elements and 60 beam positions. To fit the antenna in the limited space on the aircraft, the feed network can be reduced ten times in size by mixing two input signals at X- or Ku-band. The method is also applicable to the receive mode, and a fiber optic version may be implemented to achieve a even more compact and flexible feed network.