Detection of electromagnetic radiation leakage through small structural openings

The successful detection of small structural openings was demonstrated using electromagnetic fields to probe an unknown crack structure. Using EM fields, with frequency components from 2 GHz to 18 GHz, crack dimensions as small as 0.020 inch were detected. This resolution was limited by the data acquisition system and the mechanical tolerances of the test structure. With higher test frequencies and better measurement hardware this resolution should be improved. The crack detection was accomplished using time-domain reflectomety and frequency-domain analysis. The best measured resolution to date was obtained with frequency-domain continuous wave techniques.