Yeng Seng Lee

Experimental determination of the performance of rice husk-carbon nanotube composites for absorbing microwave signals in the frequency range of 12.4-18 GHz

Composites of rice husks and carbon nanotubes (RHC- NTs) are an innovation in improving the absorption of microwave sig- nals. Rice husks, which are an agricultural waste material, have been found to possess a signiflcant propensity for absorbing microwave sig- nals. Studies have shown that both rice husks and carbon nanotubes (CNTs) have high percentages of carbon. Thus, in this paper, we present the results of our experimental study in which we varied the ratios of rice husks and CNTs in the composite materials and deter- mined the dielectric properties of the composites and measured their abilities to absorb microwave signals. The experimental microwave

A Study of the Anechoic Performance of Rice Husk-Based, Geometrically Tapered, Hollow Absorbers

Although solid, geometrically tapered microwave absorbers are preferred due to their better performance, they are bulky and must have a thickness on the order of λ or more. The goal of this study was to design lightweight absorbers that can reduce the electromagnetic reflections to less than −10 dB. We used a very simple approach; two waste materials, that is, rice husks and tire dust in powder form, were used to fabricate two independent samples. We measured and used their dielectric properties to determine and compare the propagation constants and quarter-wave thickness. The quarter-wave thickness for the tire dust was 3 mm less than that of the rice husk material, but we preferred the rice-husk material. This preference was based on the fact that our goal was to achieve minimum backward reflections, and the rice-husk material, with its low dielectric constant, high loss factor, large attenuation per unit length, and ease of fabrication, provided a better opportunity to achieve that goal. The performance of the absorbers was found to be better (lower) than −20 dB, and comparison of the results proved that the hollow design with 58% less weight was a good alternative to the use of solid absorbers.

A Simple Technique for Improving the Anechoic Performance of a Pyramidal Absorber

In this paper, we propose a very simple technique that ofiers an extra degree of freedom to optimize the design of a tire dust- based absorber with reduced height. Cladding is a technique that is used to enhance the surface properties of a part, and it has been used in many applications for many years. In this technique, a clad layer is created on the core material, and the composition of the clad layer is adjusted to enhance the performance of the core material. We use a rice husk-clad layer to enhance the impedance matching characteristics of the low-loss, tire-dust core, microwave absorber. The overall design is a two-layer, geometrically-tapered, pyramidal structure composed of two lossy waste materials. Our main goal was to make the front surface less re∞ective (impedance matched), hence the material of the outer layer (clad) of the absorber was selected on the basis of the analysis of the dielectric properties of the candidate materials. Optimum thickness of the clad was obtained by using CST simulation software and found to be 12mm, for which a re∞ectivity performance of less than i20dB was

ENHANCED FIVE-PORT RING CIRCUIT REFLECTOMETER FOR SYNTHETIC BREAST TISSUE DIELECTRIC DETERMINATION

In this study,a Six-port Reflectometer (SPR) with dielectric probe sensor is used to predict relative dielectric,er of normal and tumorous breast tissue in frequency range from 2.34GHz to 3.0GHz. Other than that,a superstrate with an exterior copper layer is overlaid on the surface of a primitive Five-port Ring Circuit (FPRC),which is also a denominated,enhanced superstrate FPRC. It is the main component of the SPR and is presented in this paper as well. The enhanced superstrate FPRC is capable of improving its operating bandwidth by 26% and shifting the operating centre frequency to a lower value without increasing circuit physical size. The detailed design and characteristics of the FPRC are described here. In addition,the enhanced superstrate FPRC is integrated into the SPR for one-port reflection coefficient measurement. The measurement using the SPR is benchmarked with Agilent’s E5071C Vector Network Analyzer (VNA) for one-port reflection coefficient. Maximum absolute mean error of the linear magnitude and phase measurements are recorded to be 0.03 and 5.50°,respectively. In addition,maximum absolute error of the predicted dielectric and loss factor are 1.77 and 0.61,respectively.

Composites Based on Rice Husk Ash/Polyester for Use as Microwave Absorber

This paper is to study the dielectric properties and microwave absorption of rice husk ash/polyester (RHAP) composites. The RHAP composites prepared with different weight ratio (40–80 wt. %) of rice husk ash (RHA) loading into polyester was fabricated. A rectangular waveguide transmission line method was used to measure the dielectric properties of the RHAP composites. The RHAP samples were designed and simulated with different thickness and percentage of RHA loading by using Computer Simulation Technology Microwave Studio (CST-MWS) software. The materials, their dielectrics properties measurement and microwave absorption result over 12.4–18 GHz (Ku-Band) frequency range are discussed. The dielectric properties of composites increase with increasing loading the RA wt%. The RHAP sample with different thickness was investigated in Ku-Band. The microwave absorption was up to 99.84 %, using 80 % loading of RHA with thickness 15 mm at 13.81 GHz, and showing the RHAP composites is applicable as microwave absorber.

Dielectric spectroscopy of pharmaceutical drug (Paracetamol) dosage in water

This paper discuss about the dielectric measurement on different concentration of pharmaceutical drug using Agilent 85070E High-Temperature and Slim form probe. A microwave dielectric measurement is set up to measure dosage of drug in solution. It is well-known as non-destructive and rapid method. In this work, the drug used is paracetamol because it is a common consumed pharmaceutical drug by public as mild painkiller. The dielectric measurement was conducted on paracetamol from 200 MHz to 10 GHz. The solution of paracetamol was prepared in various concentrations (molarity). Solution with different concentration will exhibit different dielectric properties. A P-Series Network Analyzer (PNA) is used to measure the dielectric properties.

Investigation of Rice Husk/CNTs Composites Performance in Microwave Properties

This paper is to study the performance of rice husk and carbon-nanotubes nanotubes (RH-CNTs) composite material as a microwave absorber. The rice husk (RH) is a lossy material that contains dielectric properties which suitable used as microwave absorber. The dielectric properties are playing a main role in microwave absorption of any material. The dielectric properties of materials were measured using an Agilent dielectric probe. The microwave absorption performance of rice husk and CNTs composites was investigated by using rectangular waveguide transmission line in simulation. The microwave absorbers were designed and simulated using the Computer Simulation Technology Microwave studio software (CST-MWS). The ability of microwave absorption between rice husk and RH-CNTs was compared in 8.2–12.4 GHz. The microwave absorption with different thickness of RH-CNTs samples was investigated. The results show that the RH-CNTs composites have a better ability of microwave absorption compared than pure rice husk.

Study on Dielectric and Magnetic Properties of MWCNTs/Polyester Composites

This paper is to study the dielectric properties, magnetic properties, and dielectric conductivity of Multi-walled carbon nanotubes (MWCNTs) and polyester (PE) composites. The composites with different amount of MWCNTs (5-15%) have been studied in the Ku-Band range (12.4-18 GHz). The rectangular waveguide (WR-62) was used to measure the dielectric properties and magnetic properties of the samples. The results show the dielectric properties and conductivity of MWCNTs/PE composites is increasing with the MWCNTs filler increases. The real part of dielectric properties values increase from 5.5 to 26.6 with increasing the MWCNTs loading from 5 % to 15 %. The increasing of MWCNTs filler in the MWCNTs/PE composites does not effects on magnetic properties, the real part and imaginary part of magnetic properties are approximate to 1 and 0. The highest conductivity of 15 % MWCNTs loading is reach to 11.02 (S/m) at 18 GHz. Keywords: composites, dielectric properties, magnetic properties, conductivity

An experimental thickness of microwave absorber effect absorption in Ku-band frequency

This paper presents the different thickness of rice husk microwave absorber effects microwave absorption performance. The sample microwave absorber was fabricated using rice husk material. The complex permittivity will be measured using an Agilent dielectric probe. The reflection loss and absorption performance of rice husk microwave absorbers will be investigated. The rectangular waveguide simulation technique had been used. This rice husk microwave absorber was simulated using the CST Microwave Studio simulation software. The ability of absorption microwave frequency between different thicknesses of the rice husk microwave absorber was compared.

Difference loss tangent layer microwave absorber effect absorption in X-band frequency

This paper presents the different layers of microwave absorbing materials (MAM) effects microwave absorption performance. The different layers microwave absorbers were simulated using Computer Simulation Technology (CST) Microwave Studio simulation software. The absorption of different layer MAM will be investigated. The absorption in microwave frequency between different arrangement layers of MAM was compared.