Non-destructive dielectric measurements and calibration for thin materials using waveguide-coaxial adaptors

This paper focuses on the calibration of apertures for rectangular waveguides using open-short-load (OSL) standards and transmission-line (TL) approaches. The reflection coefficients that were measured using both calibration techniques were compared with the coefficients acquired using the thru-reflect-line (TRL) method. In this study, analogous relationships between the results of OSL calibration and TL calibration were identified. In the OSL calibration method, the theoretical, open-standard values are calculated from quasi-static integral models. The proposed TL calibration procedure is a simple, rapid, broadband approach, and its results were validated by using the OSL calibration method and by comparing the results with the calculated integral admittance. The quasi-static integral models were used to convert the measured reflection coefficients to relative permittivities for the infinite samples and the thin, finite sample

A comparative analysis of the effect of temperature on band-gap energy of gallium nitride and its stability beyond room temperature using a Bose–Einstein model and Varshni'S model

High temperature stability of the band-gap energy of the active layer material of a semiconductor device is one of the major challenges in the field of semiconductor optoelectronic device design. It is essential to ensure the stability in different band-gap energy-dependent characteristics of the semiconductor material used to fabricate these devices either directly or indirectly. Different models have been widely used to analyze the band-gap energy-dependent characteristics at different temperatures. The most commonly used methods to analyze the temperature dependence of band-gap energy of semiconductor materials are: the Passler model, the Bose–Einstein model, and Varshni’s model. This paper is going to report the limitation of the Bose–Einstein model through a comparative analysis between the Bose–Einstein model and Varshni’s model. The numerical analysis is carried out considering GaN, as it is one of the most widely used semiconductor materials all over the world. From the numerical results it is ascertained that below the temperature of 95 K both the models show almost same characteristics. However, beyond 95 K Varshni’s model shows weaker temperature dependence than that of the Bose–Einstein model. Varshni’s model shows that the band-gap energy of GaN at 300 K is found to be 3.43 eV, which establishes a good agreement with the theoretically calculated band-gap energy of GaN for operation at room temperature. Kestabilan bahan peranti semikonduktor pada suhu tinggi di lapisan aktif jurang tenaga (band-gap) adalah salah satu cabaran penting dalam bidang reka bentuk peranti optoelektronik semikonduktor. Faktor ini bergantung kepada bahan semikonduktor yang digunakan untuk proses fabrikasi peranti elektronik ini samada secara langsung atau tidak langsung, bagi memastikan kestabilan dalam pelbagai jurang lapisan tenaga. Model yang berbeza telah digunakan secara meluas untuk mengkaji kebergantungan ciri jurang lapisan tenaga bahan semikonduktor pada suhu yang berbeza. Kaedah yang paling biasa digunakan untuk menganalisa kebergantungan jurang lapisan tenaga bahan semikonduktor pada suhu adalah: model Passler, model Bose-Einstein dan model Varshni. Sementara itu pada suhu melebihi 95K, model Varshni menunjukkan kebergantungan pada suhu adalah lemah berbanding model Bose-Einstein. Model Varshni menunjukkan bahawa jurang tenaga bagi GaN pada suhu 300 K adalah 3.43 eV, di mana ia adalah tepat dan bersamaan dengan kiraan teori pada jurang lapisan tenaga GaN untuk beroperasi pada suhu bilik

Design A Quadband Frequencies Microstrip Patch Antenna With Double C-Shaped Slot

A quadband frequencies microstrip square patch antenna with double C-shaped slot at the patch is proposed in this paper. First, a rectangular shaped patch antenna is designed for 2.40 GHz frequency (WLAN application) with narrow bandwidth of 67 MHz (operate better than – 10 dB between 2.368 GHz and 2.435 GHz). Then, the double C-shaped slot had been embedded in the rectangular patch antenna. There are four stages of design (Design I, Design II, Design III and Design IV) with different dimensions of patch width and substrate width. This addition of this C-shaped slot had been producing a quadband frequency range of 2.40 GHz (2.368 GHz – 2.421 GHz), 5.0 GHz and 5.2 GHz (4.795 GHz - 5.333 GHz) and 5.6 GHz (5.521 GHz – 5.677 GHz). Parametric study with different dimension are also had been considered in Design III and Design IV

Finite difference analysis of an open-ended, coaxial sensor made of semi- rigid coaxial cable for determination of moisture in Tenera oil palm fruit

In this paper, the use of the Finite Difference Method (FDM) is proposed to determine the reflection coefficient of an open-ended coaxial sensor for determining the moisture content of oil palm fruit. Semirigid open-ended coaxial sensor is used in conjunction with Vector Network Analyzer for reflection coefficient measurement of oil palm fruit. Moisture content in oil palm fruit determine optimum harvest time of oil palm fruit. Finite difference method is then used to simulate measured reflection coefficient due to different moisture contents in oil palm fruit at various stages of ripeness. The FDM results were found to be in good agreement with measured data when compared with the quasi-static and capacitance model. Overall, the mean errors in magnitude and phase for the FDM were 0.03 and 3.70°, respectively

Single layer microwave absorber based on rice husk-mwcnts composites

In this paper, rice husk (RH) and multi-walled carbon nanotubes (MWCNTs) composite have been fabricated as single layer microwave absorber. The MWCNTs with various weight ratio composites with RH have been prepared. Three different weight ratio 3 wt% MWCNTs, 5 wt% MWCNTs, and 15 wt% MWCNTs of the RH-CNTs have been designed and fabricated. Moreover, the dielectric properties of different RH-CNTs specimens have been verified by using rectangular waveguide transmission line technique. Furthermore, the microwave absorption of these RH-CNTs has been analyzed using free space measurement and CST Microwave Studio (CST-MWS). The dielectric properties and microwave absorption of different RH-CNTs were investigated in 8.2-12.4 GHz (X-band). From the measurement, the dielectric properties parameter of RH-CNTs is analyzed. The dielectric constant and loss factor of the RH-CNTs composite increases with increasing of MWCNTs weight ratio. However, the magnetic properties of RH-CNTs remain constant, ur= 1-j0. The measurement and simulation result show that such RH-CNTs composites has excellent microwave absorption up to 33 dB in a certain frequency rang

A wearable textile dipole for search and rescue application

A wearable textile antenna for search and rescue application is presented in this work. It is designed based on the dipole topology to operate at 406 MHz for the Cospas-Sarsat application and fabricated fully using textile materials. The meanderline miniaturization technique is chosen to compact the proposed dipole due to its expected large size and wavelength at 406 MHz. The antenna evaluated in planar and bent forms indicated satisfactory performance when evaluated in terms of reflection coefficients, gain and radiation patterns

FEMC Performance of Pyramidal Microwave Absorber using Sugarcane Baggasse and Rubber Tire Dust at 1 GHz to 18 GHz Frequencies

ACES The solid, geometrically tapered microwave absorbers are preferred due to their better performance. The goal of this study is to design absorbers that can reduce the electromagnetic reflections to less than −10 dB. Two waste materials of sugarcane bagasse and rubber tire dust in the powder form were used to fabricate independent samples in the pyramidal form. This paper presents the complex permittivity measurements of sugarcane bagasse and rubber tire dust materials. These two materials are found to be potential absorbing materials in microwave frequency to allow absorption of microwave EMI energy. The materials were combined and fabricated in the composite structure. A measurement system using open- ended coaxial probe method was used for characterizing the dielectric properties of the materials in the range of 1 to 18 GHz microwave frequencies. The dielectric property was used to compare the propagation constants of the material. Comparison of the results proved that these two materials have industrial potential to be fabricated as solid absorbers