A Coherent, Optically Controlled Phased Array System.

Abstract : An optically controlled microwave phased array antenna system is analyzed. Beamforming is accomplished with a large number of antenna elements that can receive any of several different true-time delays from a single fiber using multi-channel optical heterodyne techniques. System performance such as signal to noise ratio, signal to interchannel interference ratio, and dynamic range (DR) for various modulation-demodulation schemes (i.e. AM, FM, and PM) are quantitatively analyzed. An experimental system insensitive to laser linewidth arid IF frequency instabilities is demonstrated. Accurate true-time delay is demonstrated across the L band (0.8 to 1.5 GHz). The DR for one channel is 52 dB/MHz. For a narrow channel spacing of 1 angstrom at 1.55 micrometers, the interchannel interference is <-50dB. Also, monolithic photonic integration using vertical twin-waveguide (TG) structure based on single-step MBE grown InP/InGaAsP material is studied as a means of practical implementation of large scale photonic systems. Finally, high efficiency, high power semiconductor lasers employing a 1.5 micron InGaAsP/InP separate confinement multi-quantum well structure, are investigated for use in high DR, high density RF-optical links.