Photonic RF Mixing Food For Multibeam Arrays

Abstract

A number of optical beamforming techniques are currently being pursued which make use of low loss, low dispersion, single mode fiber to construct wide-band feed networks for phased array antennas [ l ] . The photonic RF mixing feed is one promising approach which uses the feed network itself to produce phased signals required for beam scanning. This method uses two fiber manifold networks to produce and to distribute two sets of RF modulated optical control signals to the antenna elements. The control signals are subsequently photodetected, and then mixed and filtered in the RF domain to provide each element with the proper output frequency and phase for beam scanning. As was shown in the initial L-band demonstration of this technique (21, the inter-element phase varies linearly with the sum of the two control frequencies and the output frequency is equal to their difference. Subsequent investigations of this technique 13-51 found similar single-beam phase behavior.