Construction of photonic rotman-lens module for radar phased array antennas

In this paper we report for the first time the construction and the experimental characterization of a novel microwave photonic implementation of a Rotman-lens that eventually offers improved performance for Radar phased array antennas. The proposed scanning unit is an optical module, where photo-detectors connected to the transmitting/receiving antennas are the interfaces, converting between the RF signals and their respective optical waves. In addition to the improvement that is obtained by realizing the solution in photonics, the proposed improved design for the photonic Rotman lens realizes a linear phase profile with a varied slope, that is obtained at the output of the lens for any possible position at the input to the lens. This is in contrast to what is currently available with the conventional RF Rotman lens, where output phase front linearity is obtained for a small and discrete number of input positions.