Planar array design and analysis on direction of arrival estimation for mobile communication systems

The demand of wireless communication has increased significantly in the past few decades due to huge demand to deliver multimedia content instantly. The expansion of mobile content paired with affordable mobile devices has opened a new trend for having access to the latest information on mobile devices. This trend is made possible by the technology of smart antenna systems as well as array signal processing algorithms. Array signal processing is not limited to wireless communication, but also found in other applications such as radar, sonar and automotive. One of the important components in array signal processing is its ability to estimate the direction of incoming signals known as directional-of-arrival (DOA). The performance of DOA algorithms depends on the steering vector since it contains information about the direction of incoming signals. One of the main factors to affect the DOA estimation is the array geometries since the array factor of the array geometries determines the definition of the steering vector. Another issue in DOA estimation is that the DOA algorithms are designed based on the ideal assumption that the antenna arrays are free from imperfection conditions. In practice, ideal conditions are extremely difficult to obtain and thus the imperfect conditions will severely degraded the performance of DOA estimation. The imperfect conditions include the presence of mutual coupling between elements and are also characteristic of directional antenna. There are three topics being discussed in this thesis. The first topic being investigated is new geometry of antenna array to improve the performance of DOA estimation. Two variants of the circular-based array are proposed in this thesis: semi-circular array and oval array. Another proposed array is Y-bend array, which is a variant of V-shape array. The proposed arrays are being put forward to offer a better performance of DOA estimation and have less acquired area compared with the circular array. It is found out that the semi-circular array has 5.7% better estimation resolution, 76% lower estimation error, and 20% higher estimation consistency than the circular array. The oval array improves the estimation resolution by 33%, estimation error by 60%, and estimation consistency by 20% compared with the circular array. In addition, for the same number of elements, the oval array requires 12.5% to 15% less area than the circular array. The third proposed array, Y-bend array, has 23% smaller estimation resolution, 88% lower estimation error, and 7% higher estimation consistency than the V-shape array. Among the proposed arrays, the semi-circular possessed the best performance with 25% smaller estimation resolution, ten times smaller estimation error, and 5% higher estimation consistency over the other proposed arrays. Secondly, this thesis investigates the DOA estimation algorithm when using the directional antenna array. In this case, a new algorithm is proposed in order to suit the characteristics of the directional antenna array. The proposed algorithm is a modified version of the Capon algorithm, one of the algorithms in beamforming category. In elevation angle estimation, the proposed algorithm achieves estimation resolution up to 1°. The proposed algorithm also manages to improve the estimation error by 80% and estimation consistency by 10% compared with the Capon algorithm. In azimuth angle estimation, the proposed algorithm achieves 20 times lower estimation error and 20% higher estimation consistency than the Capon algorithm. These simulation results show that the proposed algorithm works effectively with the directional antenna array. Finally, the thesis proposes a new method in DOA estimation process for directional antenna array. The proposed method is achieved by means of modifying covariance matrix calculation. Simulation results suggest that the proposed method improves the estimation resolution by 5° and the estimation error by 10% compared with the conventional method. In summary, this thesis has contributed in three main topics related to DOA estimation; array geometry design, algorithm for the directional antenna array, and method in DOA estimation process for the directional antenna array

Cost effective mask design in CMOS transistor fabrication for undergraduates program

This paper presents a new innovative way of teaching undergraduate program using low cost masks. In MOSFET fabrication, the cost to produce a complete mask set for pattern transfer process extremely high and not cost effective for undergraduates program. The purpose of these masks is to define certain functional region on a wafer. In this work, low cost masks have been fabricated with a simple technology. An economical solution of masks using transparency films with various channel lengths from 300 µm to 500 µm has been produced. Six layer photolithography masks of MOSFET were designed using AutoCAD drawing tools and then printed using high resolution laser printer on the transparency film. Contact printing method has been utilized to transfer the mask layouts onto a 4-inch silicon wafer using standard photolithography techniques to check the line uniformity. Optical observation using high power microscope shows that the mask layouts were successfully transferred onto photoresist with minimum variation. These masks are used to fabricate an n-well CMOS transistor and then tested using Keithley 2400 source meter with Lab-view measurement software. The cost effective mask design proposed was really practical for teaching microfabrication undergraduates program

Optimization of low amplitude pulse electric field exposure on colon cancer cell for wound healing application

Pulse electric field (PEF) is a method of creating transient pores in the cell membrane by exposing it to a high voltage electric field of short duration. Beside having the effect of opening pores in the membrane, PEF can change the cytoskeletal restructuring of the cell, which has an impact on the cell morphological properties and signalling pathways. There was evidence that extracellular matrix (ECM) protein and transforming growth factor beta (TGF-β) can influence cellular behaviours. Similarly, PEF was also found to modulate the cellular behaviours. However, a combined influence of PEF and ECM on cellular behaviour which could further enhances the cellular processes for wound healing and tissue engineering application has not yet been investigated. Therefore, the aim of this study is to examine the effect of PEF in combination with ECM or TGF-βs on cellular behaviour such as attachment proliferation, adhesion, migration and alignment of HT29 cell line monolayer in vitro. Cell-surface adhesion was studied via trypsinization assay in which the time taken for cells to detach from the monolayer would give the means of assessing the strength of adhesion. Cell migration was studied by creating a wound model on a confluence monolayer of the cell in vitro. Cell alignment was investigated via micro contact printing techniques. The PEF was found to increase the attachment, proliferation and migration rate of the HT29 cell by 67.6, 27.1 and 108% respectively and decrease the adhesion strength of the cells by 29.2%. The results also show that 600V/cm and 5ms electric parameter could potentially reduce the unpleasant sensation associated with the standard electric field parameter currently in used in electrochemotherapy. The results of the cell alignment to the ECM proteins pattern have shown that PEF has improved the HT29 cell alignment by more than 40%. Similarly, the PEF was found to increase the proliferation and decrease the adhesion rate of cells in a TGF-β3 supplement by 50.2 and 24.1% respectively. Thus, the outcomes of this research revealed that the use of PEF in the presence of ECM protein have potential implication in wound healing application (by increasing the rate of cell migration and decreasing cell adhesion)

Bluetooth-based alarm system

This paper proposes the implementation and the advantage of Bluetooth technology on wireless alarm system.The system is realized using a microcontroller PIC16F877A and MPLab IDE software as the control block to link between input and output signals. This paper is using both Bluetooth adapter and Bluetooth module to manipulate the command given to the system.In fact, the traditional 32-bit alarm security system seems dwarfed by this wireless alarm system due to its high security, more user-friendly and lower-cost.Moreover, this wireless technology could operate within a distance of up to 10m independent of line of sight even with obstacles in between.The result shows the wireless system could control intended output with no trouble within specified distance. Hence, it is concluded that the system works effectively with more improvement over the conventional system

Characterisation of ballistic carbon nanotube field-effect transistor

Scaling process of silicon transistor, particularly MOSFET, in the past decades had increased the performance of silicon transistor with reduction of its size. However, the scaling process will eventually reaches its limit and by that time a new group of devices are expected to replace MOSFET in digital applications. This group of devices, known as nanoelectronic devices, is expected to offer better device geometry in nanometre scale with superior performance. Carbon nanotube fieldeffect transistor (CNFET), one of nanoelectronic devices, is a transistor with its channel is made of carbon nanotube and it is designed to provide the solution for scaling process and the possibility of coexistence with current silicon technology. The purpose of this project is to study the behaviour of CNFET and the main focus is on the simulation of its current-voltage (I-V) characteristic. The simulation study is carried out using MATLAB program and the result obtained is used to compare the device performance with MOSFET. Further analysis is also made to see the effect of oxide thickness and carbon nanotube diameter on the device performance, in particular the drain current. From the simulation study, it is concluded that the performance of CNFET has no significant advantage over MOSFET and its performance is also affected by both nanotube diameter and oxide thicknes

Peraturan interaksi peristiwa komunikatif wawancara dalam akhbar

Peristiwa komunikatif wawancara merupakan suatu peristiwa dua hala yang bersifat interaktif. Dalam peristiwa komunikatif wawancara, pola komunikasi yang diujarkan melalui lakuan bahasa tertentu memberi makna mengikut maksud ujaran daripada pemeran. Komunikasi berkesan dapat mengungkap persoalan siapa, bila, bagaimana, dan apa yang dapat menjelaskan segala keraguan dalam sesuatu pola komunikasi. Ini secara tidak langsung menyentuh kepada penelitian terhadap komponen dalam peraturan interaksi. Justeru, persoalan tentang etiket bahasa perlu diberi penekanan, kerana etiket bahasa memberi perhatian kepada cara-cara bahasa diungkapkan, berteraskan peraturan sosial dan budaya komuniti penuturnya. Objektif kajian ini adalah untuk menghuraikan dan menjelaskan peraturan interaksi melalui pola komunikasi yang diujarkan oleh pemeran dalam peristiwa komunikatif. Tumpuan kajian adalah terhadap wawancara dalam akhbar Mingguan Malaysia dan Utusan Malaysia dengan memberi penelitian terhadap peraturan interaksi yang terdapat dalam peristiwa komunikatif wawancara akhbar. Analisis data dilakukan dengan mengikut pendekatan etnografi komunikasi, dengan memberi tumpuan hanya kepada satu komponen, iaitu komponen norma interaksi. Berdasarkan kajian peristiwa komunikatif wawancara dalam akhbar ini didapati peraturan interaksi melalui penggunaan bahasa lisan dalam suasana formal dapat menyumbang kepada keberkesanan komunikasi dalam suatu hubungan sosial yang diseimbangkan dengan pemahaman terhadap latar budaya pemeran. Ini menjelaskan bahawa etiket bahasa amat dititiberatkan dalam mencapai matlamat suatu perbincangan yang interaktif. Kebijaksanaan pemeran dalam mematuhi peraturan interaksi yang menjadi nilai tradisi suatu komuniti dapat dimanfaatkan untuk memastikan komunikasi berkesan dicapai. Bahkan dalam suatu perbincangan interaktif kematangan setiap pemeran memberi hujah dapat dinilai daripada kemampuan pemeran memahami budaya yang melatari komuniti tertentu

Greywater treatment technologies for aquaculture safety: Review

This review intends to discuss on greywater treatment technologies, which are the physiochemical, biological and advanced oxidation process (AOP) treatment technologies that are used to remove organic, nutrient and surfactant pollutants in greywater. The focus of this study is to compare the treatment technologies to remove greywater pollutants in the coastal area. Each technology will be compared in terms of its advantages and disadvantages, including its potential in greywater treatment technologies development. Measurement parameters of water quality from other studies include physicochemical, organic content, nutrient, and surfactant that are developed from each greywater treatment mode. AOP has a huge potential in greywater treatment since the technology has a low cost of development, easy to install, and is able to be deployed on a small scale. The AOP could be combined with other treatment techniques to produce an improved output

Effects of growth solutions ageing time to the formation of gold nanorods via two-step approach for plasmonic applications

We demonstrate the structural reorganization of gold nanorods (GNRs) that could fine-tune localized surface plasmon resonance (LSPR) by using modified wet chemical synthesis on the solid substrate. Controlling the growth solution ageing time using the modifiable GNRs is an approach to overcome the limitations of rods formation due to inhomogeneous and uncontrollable size and aspect ratio. In this study, the suitable ageing time of GNRs was determined to produce optimum GNRs in terms of surface density and aspect ratio. As the ageing time was increased from 30 min to 24 h, the colour of the growth solution was changed from light to dark purple. The change is associated with the density of the nanorods formation. The optical spectral peaks of GNRs occur in a range between 500 nm and 800 nm in the visible and near-infrared region spectrum for transverse surface resonance (t-SPR) and longitudinal surface resonance (l-SPR), respectively. From the morphological analysis, it was found that 20 h ageing time resulting in high density and homogeneous GNRs with 74.81% surface density with 4.23 ± 0.04 aspect ratio. Hence, the growth ageing time of GNRs can be manipulated to control their shape evolution and dimension in terms of size and aspect ratio. The controllable aspect ratio and size GNRs can be potentially used as sensing material in plasmonic applications

Effect of additive acid on seeded growth of gold nanobipyramids

The presence of sharp tips and edges of gold nanobipyramids (GNBPs) lead to strong local electromagnetic field enhancement. Herein for the first time we present a study on efficacy of additive acid on the formation of GNBPs. The effect of additive acid type and its concentration in growth solution were investigated to obtain various yield and aspect ratio of GNBPs. Morphological characterization shows the nanoseeds that were grown in growth solution prepared using HCl, H2SO4, and HF at concentration from 0 to 1 mL produced GNBPs with yield ranges from 5.21 ± 0.44 to 91.46 ± 3.32% and aspect ratio from 2.00 ± 0.02 to 2.76 ± 0.05. The optical response of GNBPs exhibit dual plasmon band at wavelength around 550 nm–570 nm, corresponding to transverse surface plasmon resonance (t-SPR) and at wavelength around 700 nm–800 nm, corresponding to longitudinal surface plasmon resonance (l-SPR). The presented approach may be used to produce tunable morphological GNBPs nanostructures which potentially used in sensors, SERS, catalysis, and photonics