Integrated High-Speed Digital Optical True-Time-Delay Modules for Synthetic Aperture Radars

Crystal Research, Inc. proposes an integrated high-speed digital optical true-time-delay module for advanced synthetic aperture radars. The unique feature of this proposed approach is that both the true-time-delay waveguide circuit and high-speed electro-optic switching elements are made by using a single polymeric waveguide system and are monolithically integrated in a single substrate. As a result, it significantly reduces the device size while eliminating the most difficult packaging problem associated with the delicate interfaces between optical fibers and optical switches. Such a monolithic approach offers great precision (0.11 microns) for the RF phase control due to the sub-micrometer accuracy of lithography-defined optical waveguide delay lines. More important, the proposed optical switched true-time-delay network requires very low electrical power consumption (< 1 micro watts) due to very low power operation of electrically-switchable electro-optic waveguide gratings. Furthermore, the electrically-switchable electro-optic waveguide gratings have a very fast switching speed (<50 micro seconds) that is at least 100 time faster than any existing commercial optical switches. Other advantages of using the proposed switched digital optical true-time-delay lines include: microwave true-time-delay compatible, small, light weight, low loss, and immune to electro-magnetic interfere.