Waveform Reveals Damage

Tuesday, March 10, 2009 - 7:00pm

Dr. Robert Flake has discovered the first non-sinusoid signal that doesn’t undergo dispersion on transmission lines that would normally distort a signal. The waveform, “Speedy Delivery” (SD), helps to pinpoint the exact location of a crack in a foundation when sent through a metal cable encased in the foundation.

America is looking at a potential crisis in bridge repair. According to the American Society of Civil Engineers, deferred maintenance has left one-quarter of the nation’s bridges deficient, but the number could be much higher since that figure is based on visual inspections. The industry standard is to use a time-domain reflectometer (TDR) to test the soundness of a structure. The TDR sends an electrical pulse through a metal cable encased in the foundation. Any impedance, such as a crack, sends the signal back towards the source.

Pinpointing the exact location of an internal crack reduces repair costs dramatically. It would also be helpful to know the location of faults that have not become severe enough to actually break the cable. In other words, it would be helpful for the electrical pulse used to test the structure to provide more exact information.

In a vacuum, all waves have the same velocity of propagation. In the real world, waveforms undergo dispersion (change of shape) during transmission—until now.Dr. Robert Flake, professor of Electrical & Computer Engineering at The University of Texas at Austin, has discovered the first non-sinusoid signal that doesn’t undergo dispersion on transmission lines that would normally distort a signal. The waveform, “Speedy Delivery” (SD), is a pulse with a positive exponential leading edge.

The ultimate goal is to use SD to develop a new generation of high-resolution TDR instruments. Flake’s working prototype consists of a laptop, oscilloscope, and function generator. Field tests have proven that conventional TDRs cannot pinpoint a fault after traveling only 600 feet. This ultra-fidelity signal technology holds potential for advancing the interconnect performance and design of audio and high-speed computer communication systems.