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The Electronic Tether
by
David Popelka and Timothy Threw
Advisors: Dr. Brian Huggins and Dr. James Sennott
In an age where kidnappings occur daily, parents need to know the constant
location of their children. Numerous products have been designed to perform
this task; however all have used signal strength to derive ranging information
proving unreliable in noisy environments. To overcome this problem, the
Electronic Tether uses a time of arrival system to measure round-trip range.
The concept of "round-trip range" has been applied in long distance ranging
for many years in radar and navigation systems. Accurate short distance
ranging presents a major challenge; a radio or light pulse will travel
between the parent and child in 10 billionths of a second. The tether system
employs Spread Spectrum technology which utilizes Pseudo-Random Noise (PRN)
encoding for unique system identification. The system consists of an Interrogator
worn by the parent and a Transponder attached to the child. If the child
exceeds a set distance, an alarm sounds in the Interrogator, warning the
parent.
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