Optical control of phase and frequency of microwave oscillators

Discusses how the operation of an active phased array antenna requires that a number of control and reference signals be distributed to the array elements. The distribution of these signals, in particular those at microwave frequencies, presents considerable problems. Coaxial or waveguide transmission lines may be used, but with the number of elements large-often of the order 10000-the resulting feed network is complex, bulky and heavy. An alternative attracting much attention in recent years is to use a fiber-optic feed network. The principal advantages of using optical fibre for this application are its small size and low weight. In addition signals distributed by optical fibre are immune to electromagnetic interference, suffer low loss and also have high isolation. Despite these benefits microwave fibre-optic feeds have not been utilised, mainly because of shortcomings in the performance of the transceivers which convert between the electrical and optical domains