NASA’s Jet Propulsion Laboratory has developed a low-loss dielectric waveguide that provides a simple, versatile, and flexible transmission medium. Dielectric waveguides — long, solid pieces of dielectric that confine electromagnetic waves — offer high bandwidth and low transmission loss compared to conventional metallic waveguides. Despite these advantages, practical use of these waveguides has been limited because a large fraction of signal power is lost at the state-of-the-art interconnects joining conventional metallic waveguides and dielectric waveguides. JPL’s interconnect solution uses lens coupling to reduce these losses by a factor of 10 or more, yielding a reliable, cost-effective alternative to conventional waveguides.
Conventional interconnects consist of tapering the extremities of the dielectric waveguide that are inserted directly in the metallic waveguides, using a long waveguide transition to reduce coupling loss (radiation at the dielectric-metallic interface). With JPL’s novel interconnect solution, a lens couples the power from the metallic waveguide to the dielectric waveguide. This lens can be fabricated inexpensively from the same dielectric material as the dielectric waveguide. The ellipsoid geometry of the lens is designed to maximize the coupled power into the dielectric waveguide, resulting in only a small fraction of the coupled power radiating at the interface (14 to 20 dB). A small stepped impedance at the input of the lens and inserted in the waveguide provides a better matching impedance network at the discontinuity. Unlike conventional interconnects, the lens-coupled dielectric waveguide does not depend on physics contact; this improves reliability, reduces packaging complexity, and allows for added vibration/stress immunity.
Potential uses include data transmission media in applications where low transmission/coupling losses are critical, and data links with added vibration/stress immunity like those used in communication links between modules on spacecraft, landers, and rovers.