A Coherent RF repeater for distributed communications

The quality of a communications link is fundamentally limited by its transmission power. In the case of a mobile or small platform, this limitation can be particularly crippling because of energy storage constraints. In addition, a single platform, especially one equipped with an omni-directional antenna, can be limited in its ability to control where its signal is broadcast spatially. The former challenge motivates the use of a repeater to boost or null the signal power at a target; the latter prompts the concept of having that repeater act as a cooperative platform in order to provide spatial diversity as well as additional power on target. Some cooperative distributed communication methods have been demonstrated (D. Brown, P. Bidigare, and U. Madhow, ICASSP 2012), but these rely on feedback from a receiver. In a noncooperative setting, repeaters can be used to sample a transmitted signal and noncoherently retransmit a modified version of it to degrade the performance of a receiver (D. Torrieri, IEEE J. Sel. Areas Commun., vol. 7, no. 4, pp. 569–575, May 1989).