Optically controlled phased arrays Latest techniques

The authors present examples of how the following four functions can be implemented in phased arrays: the distribution of a frequency reference to provide a stabilized carrier signal in both transmit and receive (T/R) modes of operation, the distribution of baseband information from CPU (T/R modules) to T/R modules (CPU), the distribution of control signals for amplitude and phase control of active T/R modules, and optical signal processing that will lead to the removal of the burden of signal processing from the small area of T/R modules to the distribution networks. It is noted that optically fed phased array antennas using the T/R level data mixing are realizable up to Ka-band with today´s photonic device technology; however, this architecture demands a change in the design topology of the MMIC (monolithic microwave integrated circuit) T/R modules. True time delays are integrated with the data signals in this architecture by combining the externally modulated FO (fiber-optic) links with the acoustic-optic beam deflectors, to avoid beam squint. Initial analysis indicates that, at present, the T/R level data mixing architecture is superior to the CPU level data mixing as the carrier frequency exceeds C-band for the directly modulated, and X-band for the externally modulated FO links.<>