Liyana Zahid

Development Of Pyramidal Microwave Absorber Using Sugar Cane Bagasse (SCB)

The need to flnd ways to efiectively utilize the large quantities of agricultural waste that are produced is indicative of the huge potential associated with producing an alternative pyramidal microwave absorber for anechoic chamber-testing applications. We propose the development of a pyramidal microwave absorber that can use sugar cane bagasse (SCB), a byproduct from the production and processing of sugar cane, as the absorbent. In this paper, we report the results of our use of dielectric probe measurement to determine the dielectric constant and loss tangent of SCB. These values were used to model and simulate an SCB pyramidal microwave absorber in Computer Simulation Technologys (CSTs) Microwave Studio. This absorber was operated in the microwave frequency range between 0.1GHz and 20.0GHz.

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

Performance of Sugarcane Bagasse and Rubber Tire Dust Microwave Absorber in Ku Band Frequency

The electromagnetic interference (EMI) absorbing materials in various microwave frequency were required most now due to increasing demand of electromagnetic compatibility (EMC) for electronic devices with various electromagnetic environments. So, absorber materials are needed in RF/Microwave to eliminate and absorb electromagnetic energy. Absorbers can be used to create a free space environment in anechoic chamber. This work describes the performances which are the reflection loss and absorption for composite of sugarcane bagasse mixed with rubber tire dust microwave absorber in Ku Band frequency (12.4–18 GHz). The parameters such as dielectric properties, reflection coefficient (S11) and transmission coefficient (S21) were investigated. The main objectives of this research are to design and develop a microwave absorber with new green materials which are sugarcane bagasse and other waste material such as rubber tire dust. These agricultural wastes can help save the nature and the fabrication cost of microwave absorber can be reduced. Based on the result, it proved that the sugarcane bagasse-rubber tire dust can be a good alternative material to be used as microwave absorber and can operate in frequency range between 12.4 and 18 GHz.

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.

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

On the Miniaturization High Permittivity DRA with Array Patches

The miniaturization on planar printed-circuit antennas by loading the ceramic material of high permittivity material bismuth titanate has been experimentally demonstrate on the micro strip patch antenna. Due to its very small size and radiation performance, it is compatible for packaging constraints and can be easily integrated in a big variety of portable devices. The results show that the size reduction is achieved with the gain of the ceramic material antenna comparable with that of conventional micro strip antenna. In this paper, the miniaturized antenna array technology with high permittivity ceramic material, bismuth titanate array antenna is described, along with comparison computer simulation results with conventional micro strip patch antenna.

Anechoic characteristics of a metal backed anechoic agro-waste for EMC applications

Electromagnetic Interference (EMI) is a serious threat to the modern unprotected microelectronics-based integrated systems. Various techniques are implemented, to protect the mission critical and sensitive systems, against the EMI threats. One of the most important techniques is the use of absorbing material to suppress the EMI at the sources and/or receptors to ensure their Electromagnetic compatibility (EMC). Rice husk is an agro-waste and had been identified, as a naturally available cheaper anechoic material, in recent years. Some of the investigations, based on the transmission line theory, in the C band frequency range from 4 to 8 GHz, are presented in this paper. The main goal of this paper was to investigate the potential use of a single layer of the agro-waste for no reflection (perfectly matched) condition. We fabricated samples by mixing the Rice Husk Powder (RHP) with a commercially available, an easy to apply and non-toxic, glue and complex permittivity was measured. These measured values were then used to determine the perfect impedance matched condition and finally we simulate the material using CST MWS software.