Construction of a Gigahertz Measurement System and Application of Non-destructive Testing Inside Reinforced Concrete

Abstract

A spectral measurement system using a sub-THz source in the bandwidth up to 100 GHz, obtained by multiplying and amplifying a frequency-variable signal in the GHz band operated by a silicon semiconductor device, was constructed in conjunction with a frequency-tunable single-frequency THz source using GaP, which has been developed previously, in a transmission and reflection optical arrangement. The absorption spectra of ferrous corrosion products and the reflective imaging of metal fragments hidden behind concrete plate were measured. These results of the sub-THz and THz waves suggest that the interior of building structures can be inspected non-destructively based on the dielectric constant-based absorption and reflection of corrosion products and metals inside the concrete and metal surface under coating respectively, which have a high transmission property.