Design of a complex impedance matching circuit in microstrip used to detect corrosion in anchor rods

Anchor rods have been used to lash down guyed cables in telecommunications and power transmission lines. The ones can be buried or encased in concrete below-ground. Electric power companies perform inspections on their anchor rods through invasive techniques to analyze the corrosion levels. A promising nondestructive technique based on a Frequency Domain Reflectometry (FDR) method has been developed to measure the rods condition. A high frequency connector was designed to plug a network analyzer to the anchor rods. An impedance matching circuit was designed and it must be used between the connector and this instrument. Simulated and experimental results are presented for the matching circuit, and laboratory tests are shown, where it was plugged to the high frequency connector and a one-meter anchor rod.