CLASSIFICATION OF S PARAMETERS USING RDWG TECHNIQUE in NDT

Abstract

"Rectangular Dielectric waveguide (RDWG) technique employing a dielectric rod antenna is an experimental setup which is better suited for measurement of S - parameters using a Vector Network Analyser. The complex permittivity and associated parameters have a better approximation in Non Destructive Techniques compared to a Free Space Microwave Measurement (FSMM) employing microwaves. The Su. and S21 parameters derived for X-Band of frequencies (8 GHz - 12 GHz) are further processed to get the parameters which are comparable to the industrial standards for strength grading of timbers and other associated test materials. The Vector Network Analyser and the test setup was calibrated using TRL (Through-Reflect-Line) standard to compensate for reflection losses at bends and medium connectors. Nicholas-Ross-Weiner method was employed towards further calculation of dielectric parameters, by developing a code in C++. The dielectric rod antenna and the waveguide fabrication was undertaken using CAD software adhering to WR 90 standards for X band waveguides. The results obtained were comparable to published industrial standards and Network Analyser's record of sample observations for different kind of materials. Two types of Indian timber were used in this experiment and the results are analysed based on their respective thickness in comparison with other test materials with respect to variation of frequencies."