Keywords: Time Interval Measurements, 10 ps Resolution, Localization, Low-Cost Field-Programmable Gate Arrays, Electromagnetic Signals
Motivation: Even though localization methods, such as GPS, have been existing for quite some time, precise indoor localization is still an open research topic. Many use the strength of an incoming signal for this task. However, the signal strength of electromagnetic signals is likely to be distorted by any type of obstacles, such as desks, chairs, walls, equipment, persons, and the like. Therefore, others try to use the time-of-flight of a suitable signal. Unfortunately, ultra sonic signals lack longer ranges, whereas electromagnetic signals travel with the speed of light c=300.000 km/s, which is way too fast for low-cost approaches. Nevertheless, the localization by means of the time-of-flight of an electromagneic signal would excel other low-cost methods by far.
Developing a time measurement system
that has the following properties:
(1) easy to implement on standard, low-cost field programmable gate arrays (FPGAs),
(2) high-resolution, way below both the system clock and the inherent, technology-dependent gate delays, and
(3) high tolerance with respect to gate placement, and internal time delays induced by internal wire lenghts
This project has explored the following approaches:
(1) exploring tapped delay lines (TDLs),
(2) exploiting the delays induced by internal wire lengths on which signals propagate wuth two third of the speed of light
(3) utilizing basis concepts of the barn owl nucleus laminaris
The first prototypical implementation of the BOUNCE system
on an Altera Stratix II EP2S60 has shown
(1) that with only 1024 logic elements for the delay evaluation (evnt detectors)
(2) the resolution is as low as about 10 ps
(3) at an effective range of 1.5 ns
when using an external rectangular signal.
Poster: Further information can be found on the poster.
Contact: Ralf Joost