Microwave NDT of textile composites using rectangular dielectric waveguide technique

Abstract

The Rectangular Dielectric Waveguide (RDWG) Technique is a Non-Destructive Technique (NDT) which uses microwaves to determine the complex permittivity (εr) and complex permeability (μr) of dielectric materials using S-parameters. In this study, a Rectangular Dielectric Waveguide (RDWG) Measurement System was setup using a Vector Network Analyser (VNA) to perform the thru, reflect and line (TRL) calibration. The TRL calibration feature in the VNA is used to eliminate the errors arising due to multiple reflections. The S-parameters (S11 and S21) measurement is undertaken to determine complex permittivity (εr) and complex permeability (μr) of dielectric samples of textiles materials at C-band frequency (4-8GHz). This will help to study their electrical and physical properties. The time-domain gating function in the Vector Network Analyser combined with TRL calibration is utilized to remove the effects of undesirable multiple reflections due to sagging of fabric. Measurements are compared with established values of the material properties to ascertain accuracy of RDWG measurement technique. Readings thus obtained are compared with the theoretical model based on microwave mathematical quations.