Full-Duples LPI/AJ Communications Using Blindly-Adapted Retrodirective Antenna Arrays

An SBIR project is proposed here to develop novel techniques for directive and retrodirective LPI/AJ communications, by using blind adaptation algorithms to adjust the array weights on the receive and transmit paths of a communication system. The proposed processor has the capability to automatically extract signals from the received environment, and to transmit signals back to the signal source using an antenna pattern that is either maximally directed towards the communication source (A/J mode), or directed towards the communicator and away from the other emitters in the environment (LPI mode). The processor can accomplish this adaptation without special-purpose antennas, special sensor geometries, or receiver calibration data to set the reception or transmission arrays. The processor is specifically designed to be used in conjunction with LPI (pseudonoise DS and hybrid FH/DS) modulation formats. The objective of this SBIR project is to demonstrate the utility of blind directive/retrodirective communications for a full-duplex air-to-air/ground communication link. The technique development and evaluation will determine the performance of the system configurations under realistic conditions, using computer simulations. The evaluation will also include an assessment of the cost and performance trade-offs in the overall system, with emphasis on minimizing cost at the ground site.tee