Norhudah Seman

Mutual Coupling Analysis Using FDTD for Dielectric Resonator Antenna Reflectarray Radiation Prediction

A simulation technique based on Finite-Difierence Time- Domain (FDTD) is used to analyze mutual coupling efiects in re∞ectarray environment. The neighbouring element method has the ability to analyze actual non-identical re∞ectarray unit-cell accurately compared to the traditional Floquet simulation which assumes all unit- cell is identical. It is also found that the nearest neighbouring unit-cell located in E-plane has a larger mutual coupling efiects compared to the neighbouring unit-cell in H-plane. A good agreement is shown between simulation and measurement results. This technique presents a new prediction method for the radiation pattern of re∞ectarray antenna.

Design of compact single-section directional coupler for butler matrix beam-forming MIMO

This paper demonstrates a new design of 3 dB coupler operating in UWB frequency band between 3.1 GHz and 10.6 GHz. Together with UWB phase shifter, this coupler is claimed to be one of the key factors in designing a Butler Matrix that can operate in very wide frequency range. Butler Matrix has been seen to be the most preferable technique to realize the beam-forming network besides provide compact in size and more cost-effective. The arrangement between beam-forming and multiple-input and multiple-output (MIMO) can broaden the coverage and capacity of users for wireless communication system. The proposed coupler design was accomplished in multilayer microstrip-slot technology by employing broadside coupling technique. The initial dimension of the coupler was obtained using a simple mathematical formula and finalized using CST Microwave Studio simulator. The simulation results show the coupler is having a very tight coupling of 3 dB ± 2 dB, the return loss and isolation are better than 21 dB and the phase difference performance is in the range of 90° ± 2° over the designated band. The designed device occupies an area of 25 mm × 15 mm.

Reflection coefficient detection of simulation models for microwave imaging simulation system.

The study was conducted based on two objectives as framework. The first objective is to determine the point of microwave signal reflection while penetrating into the simulation models and, the second objective is to analyze the reflection pattern when the signal penetrate into the layers with different relative permittivity, εr. Thus, several microwave models were developed to make a close proximity of the in vivo human brain. The study proposed two different layers on two different characteristics models. The radii on the second layer and the corresponding antenna positions are the factors for both models. The radii for model 1 is 60 mm with an antenna position of 10 mm away, in contrast, model 2 is 10 mm larger in size with a closely adapted antenna without any gap. The layers of the models were developed with different combination of materials such as Oil, Sandy Soil, Brain, Glycerin and Water. Results show the combination of Glycerin + Brain and Brain + Sandy Soil are the best proximity of the in vivo human brain grey and white matter. The results could benefit subsequent studies for further enhancement and development of the models.

Resource element-level computations for long term evolution networks

The long term evolution base station transmits a power that is shared by all downlink channels, i.e. user data plus control channels. The powers shared by these channels result from spreading the entire transmission power of the cell over the resource elements corresponding to those channels within an LTE frame. A wide range of decisive dimensioning activities; such as cell capacity, coverage, overall available cell resources, and system overhead rely heavily on those resource elements and most importantly their corresponding power contributions. This paper gives a resource element-level analysis of the long term evolution physical layer channels. The expressions for calculating channels resource elements, their power contributions and resultant overhead are fully presented. Based on realistic frame characteristics, this paper fills the gap of the previous approaches found in literature.

Wideband six-port reflectometer design formed by enhanced branch-line couplers

A new wideband six-port reflectometer design concerning operating frequency of 2.5 to 4 GHz is presented in this article. The proposed reflectometer is constructed by using five branch-line couplers, which designed by implementing stub impedances and Defect Ground Structure (DGS). The applied DGS has a shape of rectangular ring headed dumbbell. The design and analysis of the proposed branch line coupler and reflectometer are performed by applying CST Microwave Studio software. The simulation result shows that the scattering parameter performances of branch line coupler and reflectometer have good achievement over 2.5 to 4 GHz, which is enhanced up to 11% of bandwidth compared to the conventional branch line coupler.

Reduced-size witricity charger design and its parametric study

Wireless electricity (Witricity) application is recently gaining interest owing to its effectiveness and reliability in mid-range wireless power transfer (WPT). This paper presents a parametric study on Witricity design in order to achieve a good coupling efficiency in term of S21 at the targeted frequency. The dimension of the design is 80 mm × 80 mm, which offer 75% size reduction compared to previous design of 161 mm × 161 mm. The results show that it is possible to compute the resonance frequency by varying the thickness of the substrate, dimension of the capacitors and the number of turns at transmitter and receiver side.

Human Brain Phantom Modeling: Concentration and Temperature Effects on Relative Permittivity

This paper discusses on selecting the most appropriate material for developing human-like brain phantom. It aims to investigate the effect of concentration and temperature to relative permittivity of a sample. This phantom was developed as a human-like brain for tumour detection using microwave signal. Result shows that plant gelatine is a stable and appropriate material for building phantom than agar-agar. A few models were developed based on the proposed ratio of mixture.

Design of complex ratio measuring unit (CRMU) for 2 to 6 GHz WiMAX applications

A Complex Ratio Measuring Unit (CRMU) for 2 to 6 GHz WiMAX applications is presented in this article. CRMU is formed by three 3-dB quadrature couplers and one inphase power divider, which are placed symmetrically. The configuration and performance of each coupler, power divider and CRMU are presented. The coupler, power divider and CRMU are designed using CST Microwave Studio while the S-parameter analysis is using Advanced Design System Software (ADS).

New wideband textile antenna for SAR investigation in head microwave imaging

In this paper, a wideband textile antenna for microwave imaging is presented. The antenna operates from 1.2 to 6 GHz at -10 dB level of the reflection coefficient magnitude. Whilst, the transmission coefficients of the two antennas are lower than -20 dB level. The SAR value when only one antenna is attached to the head phantom has been investigated. In addition, the maximum value of SAR is also obtained when two antennas are attached to the head phantom. The results show that the SAR levels are 0.047 W/kg and 0.022 W/kg at averaged 10 g tissues, respectively. Due to the values of SAR are far below the standard limit, thus this antenna is suitable to be used for microwave imaging.

Effect of Rainwater and Seawater on the Permittivity of Denim Jean Substrate and Performance of UWB Eye-Shaped Antenna

The effect of rainwater and seawater on the permittivity of denim jean substrate and performance of an ultrawideband (UWB) eye-shaped textile antenna is investigated in this letter. For the simulated and measured reflection coefficients in dry condition, it was found that the antenna operates at 2.4-10.9 and 1.6-12 GHz, respectively, with the simulated gain between 3.2 and 5.8 dBi from 2 to 12 GHz with efficiencies greater than 50%. The antenna can operate at the entire range in dry conditions when S11 ≤ -10 dB, but with limited performance under wet conditions. However, it cannot be used when immersed in rainwater and seawater. From the investigation, it can be shown that the permittivities of denim jean substrate under wet and immersed conditions are proportional to the permittivities of the absorbed medium (rainwater or seawater) at 2-12 GHz.