Broadband, non‐destructive characterisation of PEC‐backed materials using a dual‐ridged‐waveguide probe

Abstract

A new probe which utilises a dual-ridged waveguide to provide broadband, non-destructive (ND) material characterisation measurements of a perfect electric conductor (PEC)-backed material is introduced. The new probe possesses a bandwidth similar to existing coaxial probes and is structurally robust like rectangular waveguide probes. The combinations of these two qualities make it especially attractive for ND inspection/evaluation applications in the field. The theoretical development of the dual-ridged-waveguide probe is discussed. A magnetic field integral equation is derived by applying Love's equivalence theorem and enforcing the continuity of transverse fields at the dual-ridged-waveguide aperture. The magnetic field integral equation is then solved for the theoretical reflection coefficient using the method of moments. The permittivity and permeability of the material under test are found by minimising the root-mean-square difference between the theoretical and measured reflection coefficients using non-linear least squares. To validate the new probe, experimental results are presented of a magnetic absorbing material comparing results obtained using the new probe with those obtained using a traditional, destructive technique. The probe's sensitivity to sample thickness, flange-plate thickness, cutoff wavenumber and measured S-parameter uncertainties is also investigated.

Multi-mode analysis of dual ridged waveguide systems for material characterization

“…This section details the experimental results using multiple modes for the single probe DRWG system. All experimental data came from [21] with those using a single mode. They are also consistent with the results using the NRW method.…”

“…In addition to there robustness, rectangular and circular waveguides do not have the coupling problems previously noted for coaxial waveguides. [21] as well as clamped systems [20] showing the ability to accurately characterize simple materials with approximately 3 times the bandwidth of a traditional X-band waveguide.…”

“…These estimates are compared to experimental measurements taken from a single probe system. Experimental measurement data used was the same data obtained and used in [21]. After comparing Γ 1 1 and Γ 2 1 to reflection coefficients of the experimental system, an update to and µ is calculated and used to recalculate Γ 1 1 and Γ 2 1 .…”