A Waveguide Verification Standard Design Procedure for the Microwave Characterization of Magnetic Materials

Abstract

Abstract-A waveguide standard is introduced for validation purposes on the measurement accuracy of electric and magnetic properties of materials at microwave frequencies. The standard acts as a surrogate material with both electric and magnetic properties and is useful for verifying systems designed to characterize engineered materials using the Nicolson-Ross-Weir technique. A genetic algorithm is used to optimize the all-metallic structure to produce a surrogate with both relative permittivity and permeability within a target range across S-band. A mode-matching approach allows the user to predict the material properties with high accuracy, and thus compensate for differences in geometry due to loose fabrication tolerances or limited availability of component parts. The mode-matching method also allows the user to design standards that may be used within other measurement bands. An example standard is characterized experimentally, the errors due to uncertainties in measured dimensions and to experimental repeatability are explored, and the usefulness of the standard as a verification tool is validated.

Analysis of the Nicolson-Ross-Weir Method for Characterizing the Electromagnetic Properties of Engineered Materials

“…Some specific structures may be made from metallic elements in vacuum or air [18]. Although there will always be some small metallic or dielectric losses associated with all non-superconducting metamaterials, the assumption of a lossless material greatly simplifies the analysis of the NRW method.…”

“…For instance, the magnetic waveguide material standard described in [18] is metallic. Some of the basic observations described here were first identified in the analysis of that structure.…”

Insertable Waveguide Verification Standards for the Electromagnetic Characterization of Materials

“…Recently, an all-metal material surrogate was proposed by Crowgey et al [21] that can be duplicated with high precision using normal machining techniques. When characterized using the NRW method, the surrogate produces properties similar to those of typical magnetic materials and thus can be used to verify the proper performance of the measurement system.…”

Double waveguide method to retrieve the electromagnetic parameters of biaxial anisotropic materials

“…Introduction: To characterise the electromagnetic (EM) parameters of natural materials, the Nicolson-Ross-Weir (NRW) method [1][2][3] has been widely used by measuring the reflection/transmission (R/T) coefficients in free space [4] or through a transmission line, e.g. an enclosed single waveguide (SW) [5][6][7][8][9]. Much of the effort has been made assuming the material under test (MUT) is isotropic [7][8][9].…”

“…an enclosed single waveguide (SW) [5][6][7][8][9]. Much of the effort has been made assuming the material under test (MUT) is isotropic [7][8][9]. However if the MUT is anisotropic, the problem becomes complex.…”