High Resolution Subsurface Acoustic Soil Imaging

Not Available Next-generation RF and microwave antenna arrays are expected to possess much advancement beyond existing antenna designs. In particular, improved range and cross-range resolution and new beam capabilities would be made possible with a wideband true-time-delay antenna feed. Several new techniques, such as fiber-optic feeds, offer excellent delay-line performance with the advantages of size, weight, bandwidth, propagation loss, immunity to electro-magnetic interference, and channel isolation. The packaging issues related to fiber-based delay lines, however, are complicated and costly. A guided-wave antenna feed in another form could offer the desirable attributes of fiber-based antenna feeds with simplified packaging and greater compactness. In this program Radiant Research, Inc. proposes a novel three-dimensionally integrated polymer-waveguide-based high-packing-density structure to cover all the advantages provided by optical-fiber arrays, while further reducing the system size and eliminating the complicated optoelectronic packaging problems associated with optical-fiber-based delay lines. Five-bit optical-delay lines of up to 10 meters can be fabricated using a 5 cm by 5 cm plate housing three-layers of polymeric waveguides, which have corresponding time delays of 1 ps to 50 ns. The resulting antenna system will possess the features oflow cost, wide coverage, flexible frequency change, multiple-link capability.