Characterization of the refractive index of isotropic materials by three-detector microwave ellipsometry (original) (raw)
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Microwave and Optical Technology Letters, 2015
BSF pattern. This simulation was performed using the SONNET simulator randomly at 4.2, 6.1, 8.4, and 10.9 GHz. The adjacent frequencies at 4.2, 8.4, and 10.9 GHz has a good current distribution; however, at 6.1 GHz, the current distribution almost completely stopped, indicating that the frequency is sharply rejected. This behavior is confirmed by observing the low current distribution at that frequency band. These results are shown in Figure 4, with the high to low current density represented by red to blue, respectively.
Materials Characterization Using Microwave Waveguide System
Microwave Systems and Applications, 2017
This chapter reviews the application and characterization of material that uses the microwave waveguide systems. For macroscopic characterization, three properties of the material are often tested: complex permittivity, complex permeability and conductivity. Based on the experimental setup and sub-principle of measurements, microwave measurement techniques can be categorized into either resonant technique or nonresonant technique. In this chapter, calibration procedures for non-resonant technique are described. The aperture of open-ended coaxial waveguide has been calibrated using Open-Short-Load procedures. On the other hand, the apertures of rectangular waveguides have been calibrated by using Short-Offset-Offset Short procedures and Through-Reflect-Line calibration kits. Besides, the extraction process of complex permittivity and complex permeability of the material which use the waveguide systems is discussed. For one-port measurement, direct and inverse solutions have been utilized to derive complex permittivity and complex permeability from measured reflection coefficient. For two-port measurement, in general, the material filled in the waveguide has been conventional practice to measure the reflection coefficient and the transmission coefficient by using Nicholson-Ross-Weir (NRW) routines and convert these measurements to relative permittivity, ε r and relative permeability, μ r. In addition, this chapter also presents the calculation of dielectric properties based on the difference in the phase shifts for the measured transmission coefficients between the air and the material.
IEEE Transactions on Instrumentation and Measurement, 1998
A free-wave method for determining the dielectric and magnetic properties of materials from reflection measurements made at normal incidence and transmission measurements made at normal and oblique incidence is proposed. The method combines frequency domain measurements and time domain (TD) analysis and uses polarization to avoid typical ambiguities in the results. Varying the incident angle and the polarization, measurements were made in the X-band. The technique was validated by comparing the results obtained with those from well-established waveguide techniques. A focusing assembly makes it possible to measure relatively small samples, thus avoiding diffraction problems. It also improves the ambiguity-solving procedure proposed for the technique. The measurement procedure is fully automated by using the HP8510 network analyzer controlled by an HP362 computer, which also processes the data. Results for low-loss dielectrics such as teflon, nylon, and polymethyl methacrylate (PMMA) and for microwave-absorbing materials are reported.
Free-Space Electromagnetic Characterization of Materials for Microwave and Radar Applications
PIERS Online, 2005
Characterization of the electrical material properties ε r , µ r and tan δ is of prime importance for all microwave and antenna design applications. Experimental "S" parameters in wide frequency band are used. Problem related to the calibration elements, calibration references planes and the thickness samples (d) are reported. Problem of calibration can be avoided by using noncontact free space electromagnetic characterization based on the measurement of the insertion transfer function. This method allows spatial correction of the experimental set-up. Problem of the sample thickness (d) is essentially due to the existence of multiple solutions when solving the set of basis equations with S 21 , S 11 , ε r and µ r . This is the principal reason why some algorithms give spurious solutions or didn't converge. In this work, we developed a method combining several solutions suggested otherwise based on:
IEEE Transactions on Instrumentation and Measurement, 1991
A free-space bistatic measurement system suitable for operation in the frequency range 5.85-40 GHz is calibrated to measure the parallel and perpendicular reflection coefficients of metal-backed planar samples for obliquely incident waves. The measurement system consists of transmit and receive antennas in the bistatic configuration, mode transitions, precision coaxial cables, and the network analyzer. Diffraction effects at the edges of the sample are minimized by using spot-focusing born lens antennas, which focus most of the energy on a one-wavelength diameter circular section of the sample. A new freespace bistatic calibration technique was developed to eliminate errors due to multiple reflections between transmit and receive antennas via the surface of the sample. The effect of defocusing due to the obliquely incident plane wave with focused antennas is minimized by introducing correction factors which modify measured reflection coefficients. Details of the calibration procedure and a discussion of the experimental results obtained for planar samples of Teflon and Eccogel 1365-90 in the frequency range 12.4-18 GHz are presented. I. INTRODUCTION REE-SPACE methods employing normal incidence F S-parameter measurements of a planar sample have been used for the calculation of electromagnetic properties of microwave materials [ I], [2]. Free-space bistatic measurements give a unique and explicit determination of complex permittivity (E *) and complex permeability (p *) of magnetic materials [3], [4], which is an important consideration for characterizing novel materials. The effects of moisture content in the soil [ 5 ] , [6], dielectric properties of biological materials at millimeter wavelengths [7], and the reflectivity reduction characteristics of microwave absorbers as a function of incident angle can be studied by measuring reflection coefficients for parallel (1',1) and perpendicular (r I) polarizations. A free-space bistatic measurement set up operating in the frequency range 5.85-40 GHz is employed for the measurement of rIl and r i. The measurement set up consists of transmit and receive antennas in the bistatic configuration, mode transitions, precision coaxial cables, and the vector network analyzer. The mode transitions are needed to connect the coaxial cables from the S-parameter test set to antennas. Rectangular waveguide to coaxial line adapters and circular-to-rectangular waveguide Manuscript
2012
The transmission / reflection technique for complex permittivity determination is employed to characterize dielectric materials. The algorithm for permittivity extraction eliminates mathematically the systematic errors of the experimental setup. This technique needs two uncalibrated scattering parameter measurements using the Vector Network Analyser; the first is done with a partially filled rectangular waveguide by a standard dielectric Teflon sample (PTFE), and the second is performed with the sample under test. The relative complex permittivity of wood material is measured over the X-band frequencies [8.2 12.4] GHz and the average relative error between the calibrated and uncalibrated results is calculated. To improve furthermore the proposed method, the mobile average is applied to the experimental uncalibrated measurements and the results agree well with the calibrated measurements.
Measurement, 2013
The work of this article is a contribution to the characterization of new materials at microwave frequencies and enrichment the existing database. The transmission/reflection technique for complex permittivity determination is employed to characterize a set of low-loss dielectric materials. The algorithm for permittivity extraction eliminates mathematically the systematic errors of the experimental setup. This technique needs two uncalibrated scattering parameter measurements by the Vector Network Analyzer; the first is done with a partially filled rectangular waveguide by a standard dielectric Teflon sample (PTFE), and the second is performed with the sample under test. The relative complex permittivity of Delrin, Peek, Spanish Peek, Nylatron, Vulkollan, Arnite and Celotex materials are measured over the X-band frequencies (8.2-12.4 GHz), and the average relative errors between the calibrated and uncalibrated results are calculated. As other non-resonant methods, rough results are indicated of the imaginary part of the permittivity for very low-loss samples.
Microwave Measurements Part I: Linear Measurements
2007
B y convention, radio frequency (RF) and microwave frequencies range between 30 MHz and 300 GHz. Conversely, this means their wavelengths range between 10 m and 1 mm. Intense research in radar development during World War II extended the RF spectrum beyond the usual applications in radio communications. The use of shorter wavelengths resulted in laboratory equipment with proportionally smaller dimensions to generate, convey, transmit, and detect higher-frequency signals. Wavelengths shorter than 1 mm require equipment too small to be realized.