Georgia Tech Engineers Develop Ultra-compact Passive True Time Delay Device

An electronically steered antenna system can be created by using an array of individual antennas each fed with RF delayed by the precise amount needed to generate a directional pattern at the specified angle. While the concept is relatively simple, generating the specific delays required is not. Typically this has been done using electromagnetic delay lines. Researchers from the Georgia Institute of Technology have come up with an Acoustic Time Delay Device that could reduce the size and cost of phased array systems. The patent-pending device takes advantage of the difference in speed between light and sound. While acoustic delay lines are not new--some of them were used in early analog color TV sets--the Georgia Tech solution uses acoustic delay lines embedded entirely within thin film materials.

Kyle Davis, a Georgia Tech Research Institute (GTRI) research engineer and team member explained the role of delay lines in phased array antennas. “The individual antenna elements of a phased array appear to scan together, but in fact each element’s signal has to leave up to a few nanoseconds later than its neighbor or the steered beam will be spoiled. These delays need to march down each element in the array in succession for a steered beam to be produced. Without correct time delays, the signals will be degraded by a periodic interference pattern and the location of the target will be unclear.”

“Microwave acoustic delay lines actually date back to 1959, but our ultra-compact delay's small size represents a significant advance that should allow microwave acoustic delay lines to be manufactured and integrated much more readily,” said William Hunt, a professor in the Georgia Tech School of Electrical and Computer Engineering. “And it's worth noting that this innovative work took place as the result of both strong student participation and very effective collaboration across several Georgia Tech units.”

The Georgia Tech team has successfully demonstrated the current version of the ultra-compact passive true time delay can handle radar signals at 100 percent bandwidth while delivery 10-nanosecond delay. Work continues to address issues such as signal loss and to demonstrate an improved device design.

While the Georgia Tech work focused on radar applications, I wonder if this technology could be used to create low cost electronically steered receive antennas?

Doug Lung

Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.