True time delay for interference cancellation

True time delay (TTD) is essential for optically coupled phased array radars. How to implement the phased array is not so clear since a complete manifold of delays for transmit and delays must be implemented without introducing glitches associated withswitching. In a continuous transmit and receive mode, it is difficult to interrupt the operation to implement a new TTD delay combination in a noiseless way. However, TTD could be used more directly to eliminate spurious signals such as cancellation oftransmitted signals on a separate nearby receiving antenna. In such a case, the TTD delay is fixed. By implementing an adjustable signal gain, with 180,a of phase shift, the delay can be used for cancellation of excess transmitter signal. We introduce anoptoelectronic technology in the form of integrated circuits to implement the TTD. The technology provides lasers (at 980nm, 1300nm or 1550nm), directional coupler switches interconnected by passive waveguides, HFET logic and detectors all in GaAs basedepitaxy. A single integrated circuit combined with a fiber delay line and a duplicate transmitter on the receive circuit offers a rugged , low power, light weight transmitter canceller. In this STTR, we will develop the integrated components to realizeTTD. Successful development of this technology will provide high speed optical delay lines and will enable linear arrays of vertical cavity lasers to be coupled to fibers with controlled rf optical frequencies as required for many potential applicationsincluding photonic phase shifters, optoelectronic oscillators and optical beam forming networks. The components also enable interconnect technology required for many commercial applications including multi-gigabit networks, distributed computingarchitectures and high quality real-time multi-media distribution.