Rectangular Waveguide Method Research Articles

Reconstruction of Material Inhomogeneity Profile Using Partially Filled Rectangular Waveguide Measurements

This article presents a novel technique to reconstruct the inhomogeneity profiles of the material using partially filled rectangular waveguide (RWG) measurements. Variation in the sample width is developed to obtain the required independent scattering parameters for accurately reconstructing the inhomogeneity profiles. The electromagnetic parameters of the inhomogeneous sample are obtained, minimizing the difference between the measured and the theoretically calculated scattering parameters. For the first time in this article, the scattering parameters of the inhomogeneous material partially loaded in the RWG are theoretically calculated using the hybrid of mode matching and Taylor’s series expansion. A prototype of the measurement system is fabricated for experimental verification. Through comprehensive examples, experimental verifications are performed for the three types of inhomogeneous materials. The validity and accuracy of the proposed method are verified by comparing the results obtained by the RWG methods. The suggested technique is less expensive and more straightforward than the previously developed RWG method, which uses multiple waveguides and requires a single-time calibration.

Rectangular Waveguide Characterization of Biaxial Material Using TM11 Mode

A novel measurement technique is presented to determine the electromagnetic parameters of a biaxial material loaded in the rectangular waveguide. For the first time, in this paper, the TM₁₁ waveguide mode is used as an incident filed for characterization. The electromagnetic parameters of the biaxial sample are obtained, minimizing the difference between the measured and the theoretically calculated scattering parameters. For this purpose, we theoretically calculate the reflection and transmission coefficients. A prototype of the measurement system is fabricated to validate the proposed approach. Subsequently, the proposed technique is used to experimentally characterize two types of biaxial materials. The validity and accuracy of the proposed method are verified by comparing the experimental results with those obtained by the conventional rectangular waveguide method. The suggested technique eliminates the problem of preparing multiple samples and rotating them in the traditional waveguide method.

Experimental and computational study on epoxy resin reinforced with micro‐sized OPEFB using rectangular waveguide and finite element method

Epoxy resin (ER) composites reinforced with micro-sized oil palm empty fruit bunch (OPEFB) were fabricated to improve the biodegradability of electromagnetic interference connector gasket. The dielectric properties, transmission coefficient |S 21|, reflection coefficient |S 11|, reflection loss, power loss and shielding effectiveness were studied at a frequency range of 8–12 GHz. OPEFB–ER composites were prepared by varying the percentages of OPEFB (0, 5, 10, 15, 20, 25, 30 and 40%) at room temperature (25°C ±2). Dielectric constant (ɛ′), loss factor (ɛ″), reflection and transmission coefficients of the composites were measured using rectangular waveguide connected to vector network analyser. In addition, ɛ′ and ɛ″ were used in finite element method technique to obtain |S 11| and |S 21|. The results showed that the dielectric properties increased but |S 11| and |S 21| decreased with increasing OPEFB percentage in the composites. The shielding effectiveness, power loss and reflection loss increased with increasing OPEFB percentage in the composites. The simulated and measured results of |S 11| and |S 21| were in good agreement.

Attenuation and Shielding Performance of Wood-Polymer Composites Synthesized via Melt-Blend Technique

In the recent, filler-polymer composites researches have been on the rise due to its implication to electromagnetic interference (EMI) applications. The composition, morphology and surface rheology of the filler-polymer composites play an immense role in determining the electrical, mechanical, and optical properties. In this paper, the preparation and characterization of micro-composites of wood (biodegradable waste material)/polycaprolactone (PCL) composites are reported. The micro-composites were prepared using melt blend technique via the solid state route. This method was selected because of its numerous advantages compared to other methods such as being easy, cheap with mass production of materials. To determine attenuation, rectangular waveguide (RWG) method was used. The magnitudes of the transmission coefficient (S21) from the waveguide measurement were used to determine the attenuation of the wood-PCL composite substrate with respect to different percentages of wood filler. Result from the measurement showed amongst others that as the filler content increases, the attenuation increases. The highest magnitude for attenuation was calculated for the 62.5% wood-PCL composites with a value of -6.46 dB and the least attenuation was calculated for the 12.5% wood micro filler, which value gave -3.34 dB which is good for low shielding applications. Scanning electron microscope (SEM) was used to study the surface morphology of the samples.

EMI Shielding and Reflection From Textile Mesh Grids Compared With Analytic Models

In this paper, new textile-based shielding materials are presented. The woven textile mesh grids (2 × 2 and 4 × 4 mm2) are made with the use of three different types of conductive threads based on polyester yarn twisted together with steel filaments, silver-plated polyamide filaments, and silver-plated copper filaments. The conductive threads are characterized by SEM images. The transmission and reflection coefficients over the wide frequency range from 2.6 to 18 GHz are measured and analyzed using a rectangular waveguide method in a TE10 mode. The measurement results are verified and validated by two types of model analysis: theoretical analysis based on the metal-grid approach and filter model analysis based on the equivalent circuit theory. The unknown model parameters in the two cases are determined with the use of an optimization procedure that is specially designed for the scalar measurement data.

Finite element simulation and analysis of the dielectric properties of unidirectional aramid/epoxy composites

Aramid fiber reinforced composites have drawn much attention due to outstanding mechanical and dielectric properties. Dielectric properties should be predicted exactly when such composites are used as electromagnetic functional materials. A simulation method was proposed to predict the effective dielectric constants of unidirectional aramid/epoxy composites in this study. Randomly planar distributed 3D models were created to describe the microstructures of the composites. Parallel and series models were calculated by classical formulas and finite element method to verify the simulation. The distributions of aramid fibers and the dielectric anisotropy of unidirectional composites were analyzed. Dielectric measurements were carried out by the rectangular waveguide method in X‐band and excellent agreements between simulations and experiments were observed. The compression of aramid fibers and interface effect were taken into account to improve the forecasting precision. Comparative analysis was conducted between our simulation method and classical formulas, and it was found that the Maxwell‐Garnett model gives the best fit to the simulation. In addition, the effect of the fiber orientation in electric field was analyzed. POLYM. COMPOS., 39:E2226–E2233, 2018. © 2017 Society of Plastics Engineers

FeCoNi coated glass fibers in composite sheets for electromagnetic absorption and shielding behaviors

To evaluate the electromagnetic (EM) absorption and shield of magnetic composite sheet, we prepared the FeCoNi coated glass fibers filled in composite sheet. The FeCoNi was coated by electroless plating on glass fiber as a filler. The coated FeCoNi found that consist of mixtures of bcc and fcc phase. The magnetization and coercivity of coated FeCoNi are about 110 emu/g and 57Oe, respectively. The permittivity and permeability of the FeCoNi composite sheet were about 21 and 1, respectively. Power absorption increased 95% with the increment of frequency up to 10GHz. Inter-decoupling of this composite sheet showed maximum 30dB at around 5.3GHz, which is comparable to that of a conductive Cu foil. Shielding effectiveness (SE) was measured by using rectangular waveguide method. SE of composite obtained about 37dB at X-band frequency region.

Full 3-D Printed Microwave Termination: A Simple and Low-Cost Solution

This paper describes the realization and characterization of microwave 3-D printed loads in rectangular waveguide technology. Several commercial materials were characterized at X-band (8–12 GHz). Their dielectric properties were extracted through the use of a cavity-perturbation method and a transmission/reflection rectangular waveguide method. A lossy carbon-loaded Acrylonitrile Butadiene Styrene (ABS) polymer was selected to realize a matched load between 8 and 12 GHz. Two different types of terminations were realized by fused deposition modeling: a hybrid 3-D printed termination (metallic waveguide + pyramidal polymer absorber + metallic short circuit) and a full 3-D printed termination (self-consistent matched load). Voltage standing wave ratio of less than 1.075 and 1.025 were measured over X-band for the hybrid and full 3-D printed terminations, respectively. Power behavior of the full 3-D printed termination was investigated. A very linear evolution of reflected power as a function of incident power amplitude was observed at 10 GHz up to 11.5 W. These 3-D printed devices appear as a very low cost solution for the realization of microwave matched loads in rectangular waveguide technology.

An electromagnetic simulation study of the distribution of the power absorbed in evaporative humidifier elements

To resolve the uneven microwave heating of an evaporative humidifier element, the distribution of the electric field in the humidifier cavity and the power absorbed in the humidifier element were investigated using a microwave simulation. The dielectric constant and loss tangent from changes in the water content of the humidifier element were measured using a rectangular waveguide method and calculated using microwave simulation to perform the electric field calculations. Then the penetration depth of microwaves in the element was identified for different water densities. The results demonstrated that the microwave could penetrate a 100-mm-thick element with a water density of 0.054 g/cm3. The simulation results indicated that the average power density lost across the cross-section of the element (thickness) was attenuated from the front face to the rear face with increasing water density. The depth profile of the power absorbed in the element agrees with the experimental results. However, the vertical profile of the power absorbed into the element did not match with heating patterns. An air fluid analysis should be undertaken in future simulations to predict the temperature change of the evaporative humidifier element.

Preparation and characterization of liquid phase (55B2O3–45Bi2O3) sintered cobalt doped magnesium titanate for wideband stacked rectangular dielectric resonator antenna (RDRA)

Cobalt doped magnesium titanate (MCT) was prepared by a solid state ceramic method. Phase formation was investigated using X-ray diffraction and Rietveld refinement methods. 55B2O3–45Bi2O3(wt%) glass was prepared by the melt quench method. 0, 1 and 3wt% glass was added to lower the sintering temperature of MCT from 1250°C to 1050°C. Dielectric properties of cobalt doped magnesium titanate (MCT) sintered with glass were determined. Dielectric constant was measured using transmission line (rectangular waveguide) method at different microwave frequencies in X-band (8.5–12.0GHz). It has been found that value of dielectric constant is reduced by increasing percentage of glass. Optimized dielectric properties of MCT were achieved for the case of 1% glass addition and sintering at 1000°C for 2h. This MCT composition was used in fabrication of stacked (with Teflon) rectangular dielectric resonator antenna (RDRA) using coaxial probe feed for excitation with good impedance matching and wideband performance. Effects of antenna parameters such as probe height and teflon height are investigated using Ansys High Frequency Structure Simulator (HFSS) software. The experimental results are in good agreement with simulated results. The proposed antenna provides the measured input impedance bandwidth of 38.6% (6.44–9.52GHz) for reflection coefficient (S11) values less than −10dB with a measured peak gain of 7.9dB at 8.4GHz. The broadside radiation patterns are obtained (for both E- and H-planes) in the useful frequency range with fairly low cross-polarization levels in E-plane.

Electromagnetic characterization of strontium ferrite powders in series 2000, SU8 polymer

In this article, electromagnetic characterization of strontium hexaferrite powders and composites with SU8 was carried out to determine their compatibility with micro and millimeter wave fabrications. The structures of both powders and their composites were scanned with electron microscope to produce the SEM images. Two powder sizes (0.8–1.0 μm and 3–6 μm), were mixed with SU8, spin cast and patterned on wafer, and then characterized using energy dispersive x-ray spectrometry, ferromagnetic resonance (FMR) and vibrating sample magnetometry. In this investigation, FMRs of the samples were determined at 60 GHz while their complex permittivity and permeability were determined using rectangular waveguide method of characterization between 26.5 and 40 GHz frequency range. The results obtained show no adverse effects on the electromagnetic properties of the composites except some slight shift in the resonant frequencies due to anisotropic field of the samples.

STUDY OF CROSS-SLOTTED CIRCULAR MICROSTRIP FOR REFLECTARRAY DESIGN

In this paper, a circular microstrip patch centrally etched with a cross slot is studied. The slot dimensions are varied for controlling the re∞ection loss and the phase range of a re∞ectarray. It is found that the dominant TM mode of the slotted circular patch can be easily excited, and the slot length can be varied to function as a phase-changing parameter. Cross slots with equal and unequal arms are investigated. Study shows that the slope of the S curve can be made slow-changing by increasing the slot widths simultaneously. A maximum re∞ection phase range of 328.68 - is achievable in the S curve. Rectangular waveguide method has been deployed for simulating and verifying the design idea. Reasonable agreement is found between the measurement and simulation.

DRA REFLECTARRAY UNIT ELEMENTS WITH THIN UNDER-LOADING PARALLEL SLOTS

This paper presents three dielectric resonator (DR) unit elements loaded with one, two, and three narrow slots underneath for designing re∞ectarrays. The slots are aligned in parallel, and the lengths are varied to function as phase shifter for changing re∞ection phase. It is found that the dominant TE mode of the square DR element can be easily excited by placing multiple parallel slots beneath a DR element. Study shows that the number and width of the slots can be used as additional design parameters for tuning the re∞ection loss and phase range of the re∞ectarray. Rectangular waveguide method has been deployed, showing reasonable agreement between simulation and measurement. It is found that a reasonable re∞ection phase range of 313 - with slow slope is obtainable when the DRA is loaded with two slots beneath, which can be used for designing a small-size re∞ectarray. The re∞ection characteristics of the unit elements are studied, along with a complete parametric analysis.

電界シミュレーションによる気化式加湿器エレメントのマイクロ波吸収量分布に関する基礎検討

To resolve uneven microwave heating on the evaporative humidifier element, we investigate the distribution of electric field in the humidifier cavity and power absorbed in the humidifier element using microwave simulation. The dielectric constant and loss tangent by changes in the water content of the humidifier element were measured using a rectangular waveguide method and calculated using microwave simulation to perform the electric field calculations. Then, the penetration depth of microwaves in the element was identified in the water densities. The results demonstrated that the microwave can be penetrated into the 100 mm of the thick element with a water density of 0.054 g/cm3. The simulation results shown that the average of power loss density across the cross section of the element (thickness) was attenuated from the front face to the rear face when increased the water density. The distribution for the thickness of power absorbed in the element agrees with the experimental results. However, absorbed power into the element for vertical profile of the element did not match with heating patterns. To predict temperature change on the evaporative humidifier element, an air fluid analysis in the simulation should be undertaken.

Refractive index sensing characteristics of dual resonance long period gratings in bare and metal-coated D-shaped fibers

We present a theoretical study of the ambient refractive index sensing characteristics of long period gratings in bare and metal-coated D-shaped fibers. An equivalent rectangular core waveguide method based on the first-order perturbation theory has been used to study the modal behavior of the waveguide. Power coupling corresponding to dual resonance in both cases has been investigated, and an optimum metal thickness giving maximum sensitivity has been found to exist. The study shows that the dual resonances can be shifted to lower wavelengths by increasing (decreasing) the metal thickness (core to flat surface separation). Further, an optimum combination of metal thickness and core to flat surface separation, corresponding to maximum sensitivity, has been presented for different cladding modes and their relative performance has been discussed. It has been shown theoretically that detection of refractive index changes as small as 1.67x10(-7) RIU in the ambient region is possible using the optimized parameters. The study should find application in realizing highly sensitive biochemical sensors.

Analysis of polymeric arrayed waveguide grating multiplexers with non-ideal core cross sections modeled by ‘tanh’ function

By employing perturbation theory, a technique called the 'equivalent rectangular waveguide method' is proposed for analyzing the transmission characteristics of polymeric arrayed waveguide grating (AWG) multiplexers with non-ideal core cross sections, which are modeled by the 'tanh' function. Simulation results show that the non-ideal core cross sections cause the shift of the transmission spectrum, and result in the increase of crosstalk compared with the device originally designed with exact rectangular core cross sections. In order to eliminate the shift of the transmission spectrum, reduce the crosstalk and further realize accurate demultiplexing, the redesign of the AWG device is carried out.

Characterization of ferrimagnetic and dielectric materials with a rectangular waveguide—method, limits of validity

The development of passive components in the microwave range for telecommunication applications is a major focus for the next years. Some microwave passive components (such as circulators, isolators, etc.) still use magnetic materials. It is then necessary to characterize the electromagnetic properties of such materials, their scattering behaviours and to eventually highlight a non-reciprocal propagation. A method for the dielectric and magnetic characterization of multi-layer materials in the X-band (8.2–12.4GHz) is presented as well as its reliability and its domain of validity. It allows to determine the elements of the permeability tensor of ferrite sample.

Effects of trapezoid core cross-sections on transmission characteristics of polymer arrayed waveguide grating multiplexers

Based on the perturbation theory, a technique named “equivalent rectangular waveguide method” is presented for analyzing the transmission characteristics of arrayed waveguide grating (AWG) multiplexers with trapezoid core cross-sections. As an example, by using this technique, effects of the trapezoid core cross-section on transmission characteristics are performed for a 33×33 polymer AWG multiplexer around the central wavelength of 1.550918 μm with the wavelength spacing of 0.8 nm. Computed results show that the trapezoid core cross-sections result in the shift of the transmission spectrum, and lead to the increase of the crosstalk compared with the device originally designed with exact rectangular core cross-sections. In order to eliminate the shift of the transmission spectrum, decrease the crosstalk, and further realize the accurate demultiplexing, the redesign of the AWG device is carried out.

Modeling microwave electromagnetic field absorption in muscle tissues

Absorption of electromagnetic energy in human tissues is an important issue with respect to the safety of low-level exposure. Simulation is a way to a better understanding of electromagnetic dosimetry. This letter presents a comparison between results obtained from a numerical simulation and experimental data of absorbed energy by a muscle. Simulation was done using a bidimensional double-scale homogenization scheme leading to the effective permittivity tensor. Experimental measurements were performed at 10 GHz on bovine muscle, 30 hours after slaughter, thanks to the open-ended rectangular waveguide method. Results show a good agreement between measurements and simulated data.