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MASTER (COMPLETED)


Researcher : OSMAN AYOP (Master - Graduated)

RESEARCH TITLE : ELECTROMAGNETIC BAND STRUCTURE INCORPORATED WITH UWB ANTENNA

Abstract :

This research focuses on electromagnetic band gap (EBG) structures and their application on ultra-wideband antenna. The first phase involves a parametric study of conventional 2-D mushroom-like EBG (mEBG) structure using method of suspended transmission line. The observation on 9 patch elements of mEBG structure is proposed to indicate the periodic arrangement. The parametric study is conducted based on patch width, gap between elements, substrate thickness, via radius and dielectric constant. Then, a new shape of EBG structure named as slotted patch EBG (spEBG) structure is presented. This new structure provides additional stop band frequency at higher frequency band and it is suitable to be used as dual band rejecter. A parametric study is also conducted for this structure to understand the characteristic of the stop band frequency for different parameters effect. All the results are presented in form of table and graph. The second phase involves the design of a new structure of ultra-wideband (UWB) antenna. Based on simulation, this antenna operates from 2.7 GHz to 13.8 GHz while from measurement, it operates from 2.9 GHz to 13.9 GHz. The third phase presents the incorporation of UWB antenna with single mEBG structure which is operates at 5.8 GHz and also spEBG structure operates at 3 GHz and 8 GHz. The simulated S21 and radiation pattern show that the single mEBG structure can be used as single frequency band rejecter while single spEBG structure can be used as dual frequency band rejecter. All the structures have been fabricated and the measurement result shows a good agreement with the simulation results in term of stop band frequency, return loss, and radiation pattern.



Researcher : FARID ZUBIR (Master - Graduated)

RESEARCH TITLE : Microstrip Reflectarray Antenna With Minkowski Shape Radiating Element

Abstract :

Microstrip Reflectarray Antenna (MRA) is an alternative for high gain antenna, which combines some of the most noticeable features of a traditional parabolic reflector antenna with microstrip array technology. Since the structure is flat, phase compensation is mandatory in designing MRA in order to have the same behaviour and functionality as the conventional parabolic reflector-type antenna. The concept is based on analysis from the reflection coefficient of individual cells. By varying the physical parameter of each reflectarray unit cell, the required phase-shift can be obtained and will scatter the incident communication signal towards the intended direction of propagation. In this work, several configurations of reflectarray unit cells using fractal shapes as the radiating element such as Koch-square, Koch-triangle and Minkowski have been analyzed and compared with the square shape at 11 GHz. A unit cell configuration with a Minkowski shape as the radiating element printed on RF-35 substrate of thickness of 1.524 mm is suitable and can provide acceptable phase range (305°) and low insertion loss (< -0.4 dB). At 11 GHz, the MRA with Minkowski elements is found to have a higher gain of 29.6 dB and a lower side-lobe level (SLL) of -25 dB when compared to the conventional MRA with square elements which gives 27.4 dB gain and -19 dB SLL respectively. Validation for the MRA with Minkowski elements is achieved here by comparing the simulated and measured radiation patterns. Additionally, the margin difference between the sweeping realized gain (simulation) and the sweeping power received (measurement) is compared within a frequency range of 10 – 12 GHz.



Researcher : MUHAMMAD FAIZAL ISMAIL (Master - Graduated)

RESEARCH TITLE : Frequency Reconfigurable Log-Periodic Antenna Design

Abstract :

The concept of reconfigurable antenna is widely used as additional features of reconfigurable ability for future wireless communication system. There are various configurations of reconfigurable antenna such as monopole, dipole and log-periodic wideband antenna. The integrations of reconfigurable antennas with radio frequency (RF) switches are needed to perform the switchable ability. In this research, a log-periodic antenna (LPA) has been designed to perform a wideband frequency operation by connecting thirteen square-patch antennas using inset feed line technique. Then, the reconfigurable log-periodic antenna (RLPA) is designed by connecting positive-intrinsic-negative (PIN) diodes at every transmission lines with a quarter-wave length radial stub biasing. The representation of real PIN diodes and the locations of biasing circuits in simulation are also included. Three different sub-band frequencies with a bandwidth of 20% (3 - 4, 3.7 - 5, and 4.8 - 6 GHz for each band) are configured from the total of 73% bandwidth (3 to 6 GHz) of the wideband operations by switching ON and OFF of the PIN diode. Other sub-bands or narrow band can also be configured by selecting other group of patches. Validation for the LPA and RLPA is achieved by comparing the simulated and measured radiation patterns. The measured half-power beamwidth (HPBW) for LPA are 62°, 58° and 72° at frequency 3.4 GHz, 4.0 GHz and 5.8 GHz, respectively, while 73°, 67° and 72° for RLPA at the same frequency band. The simulated gain for LPA and RLPA are around 4.9 dB and 5.0 dB respectively, while the measured gain is around 5.5 dBi for LPA and 5.7 dBi for RLPA within a frequency range of 3 – 6 GHz. All the structures have been fabricated and the measurement results show accuracies of 97.5% for return loss, 80.2% for gain and 98.4% for HPBW with the simulation results.



Researcher : AMERUDEEN WAHID (Master - Graduated)

RESEARCH TITLE : Dual Layer Printed Microstrip Reflectarray Antenna With Minkowski Radiating Element Shape

Abstract :

The planar microstrip reflectarray antenna is a combination of the advantages of parabolic reflector and phase array antenna. Reflectarray is a planar antenna consisting of an array of microstrip patches on a grounded substrate, where the required phase shift is obtained by tuning the dimension of the radiating patches. Whenever a signal from a primary source propagates towards the reflectarray, the incident signal is scatter towards the intended propagation. Reflectarray is widely use in communication system especially in the satellite communication technology to replace the bulky and high complexity parabolic dish antenna. In this research project, a fractal shape (Minkowski) is introduced as a radiating element shape. Three configurations for a dual layer printed reflectarray antenna are designed and analyze at 11 GHz. The configurations are two staked arrays composed of two Minkowski patches, two staked arrays composed of Minkowski and Square patches and lastly two staked arrays composed of two Square patches. To evaluate the performance of the configuration, a modeling design is carried out using CST Microwave Studio. From the unit cell simulation of the 3 configurations, the unit cell of two staked arrays composed of Minkowski has widest phase range of up to 420º and lowest insertion loss which is lower than 0.6 dB. To fully validate the reflection phase simulation setup, the unit cells are characterized and measured in waveguide simulators. A dual layer printed microstrip reflectarray antenna with Minkowski radiating shape elements prototype has been designed, built and measured to verified and compared to the simulation modeling result. The prototype has been constructed using Taconic RF-35. From the measured radiation pattern at 11 GHz shows a HPBW of 4.1º, a side lobe level of –15 dB and a maximum directivity of 29 dBi. Additionally, the measurement of the power receive was conducted within a frequency range of 10 – 12 GHz.



Researcher : NAZIRAH BINTI OTHMAN (Master - Graduated)

RESEARCH TITLE : ENERGY ABSORPTION BY HUMAN BODY IN THE PRESENCE OF CONDUCTIVE ITEM

Abstract :
This study quantifies the effects of human body on antenna performance and SAR in the presence of conductive metallic object focussing on the area of human wrist. Conventionally, the mobile handset is left inside the trousers pocket where a certain amount of electromagnetic energy passes through the body rather than being directly radiated. A anatomically realistic Voxel body model is exposed to the near-field radiation. The position of the human sensitive organ (testicles) is closed to the radiation source. This study was carried out using CST Microwave Studio which is based on Finite-Integration Technique. Three types of common metallic objects and medical implant are used in this research; coin, ring, zip and intramedullary rod in order to determine the effect of metallic object on antenna performance and SAR. The results are discussed in term of S11, antenna radiation pattern and energy absorption by the human biological tissue (inside the human leg and testicles) in the presence of conductive metallic items.



RESEARCHER : Muhammad Azfar Abdullah (Master - GRADUATED)

RESEARCH TITLE : DESIGN AND DEVELOPMENT OF TEXTILE ARTIFICIAL MAGNETIC CONDUCTOR INCORPORATE WITH PLANAR DIPOLE ANTENNA

Abstract:
The radiation characteristics of wearable dipole antenna which are omni-directional radiation pattern towards human body are very crucial for wearable application.  In order to avoid the radiation towards human body, artificial magnetic conductor (AMC) are designed and analysed. The purpose of implementing the textile AMC is to reduce the back radiation towards the human body from the antennas radiation characteristics. This will increase the gain of the antenna when incorporate with the AMC. By implementing this concept, the dipole antennas beam direction is shifting outward from the human body and the antenna’s gain is increased. In this work, the incorporation of dipole antenna with AMC is described and analyzed. The propose antenna and AMC is designed, simulated and analysed using CST Microwave studio. The antenna and the AMC is fully made of textile material.  The antenna's substrate is made from denim jeans with a tangential loss of 0.019 and dielectric constant of 1.67 with 0.67mm substrate thickness. The radiating elements are made from two different conductive fabric which are shieldit super fabric and purely copper fabric. Three configurations of artificial magnetic conductor are presented and discussed. A textile dipole antenna incorporate with 3 x 3 arrays of textile magnetic conductor is designed at 2.4 GHz  The second design is at 5.8 GHz with 3 x 3 arrays of AMC. Finally, both designs are combined to become a dual band artificial magnetic conductor. The properties of the fabric such as bending effect, wetness effect and on-body measurement are investigated for the antenna incorporate with AMC.  The different position of the dipole antenna above the AMC which may alter the performance of the antenna is also analysed and discussed. The performances of the dipole antenna with and without AMC are compared. A Very good agreement between simulated and measured results such as return loss, radiation pattern and gain is achieved, thus verifying the proposed antennas concepts. 



Researcher: MOHD EZWAN JALIL (Master - GRADUATED) 

RESEARCH TITLE: DESIGN AND DEVELOPMENT OF MULTIBAND AND ULTRA WIDEBAND TEXTILE ANTENNA FOR WEARABLE APPLICATION 

Abstract:
In recent year, a wearable system has been growing rapidly for monitoring, tracking and navigating activities in healthcare, medicaland military sector. A flexible and comfortable antenna is required for wearable application. The flexible textile antenna using denim materials are proposed for wearable application due to robustness, conformal and light-weight type of material. The permittivity of denim material is 1.7 and the loss tangent of denim is 0.025 are discovered using coaxial probe method for dielectric measurement. Two types of conducting element for textile are investigated which are Shield fabric and copper foil tape to evaluate the antenna performance with different conducting element. Two designs are proposed for wearable application. For the first design, a multiband Koch fractal textile antenna is designed which resonate at 0.9, 2.45GHz and 5.8GHz. For the second design, a coplanar waveguide (CPW) ultra wideband (UWB)textile antenna which cover the frequency from 2.5GHz until 15 GHz The detail analysis are conducted on a multiband anda ultra wideband (UWB) antenna in term of bending, wetness condition and on body measurement.



Researcher: IZNI HUSNA (Master - GRADUATED) 

RESEARCH TITLE: Switchable and Tunable Multiband Slot Dipole Antenna 

Abstract:
Developments of frequency reconfigurable antennas in the wireless communication systems have attracted a lot of attention recently. Most reported antennas have narrowband to narrowband reconfiguration and multiband to multiband  reconfigurations. In this research, a slot dipole antenna has been introduced with the ability to produce a multiband to narrowband reconfiguration. This type of antenna can suppress the problem of co-site interferences. Thus, two types of frequency reconfigurable antennas are studied and discussed which are switchable and tunable multiband antennas. The switchable multiband antenna is reconfigured by using Radio Frequency (RF) switches. The proposed antenna is capable to reconfigure from multiband to dual and/or single band. By having seven configurations of switches, this antenna can operate at 2.4 GHz, 3.5 GHz and/or 5.2 GHz. The antenna is able to have three states of single-band, three states of dual-band and one state of tripleband. Meanwhile, the tunable multiband antenna is reconfigured by using variable capacitors. The proposed antenna is capable to have a wide frequency tunability range for dual or single band operation (1.5 GHz - 4.5 GHz, ratio of 3:1). Each antenna has been successfully designed, fabricated and tested. The simulation and measurement results were analysed and presented in terms of reflection coefficient, radiation pattern and gain. The simulation and measurement results have been compared and a very good agreement was achieved. The reflection coefficient average accuracies of 98% has been achieved. These proposed antennas are suitable for future multi-mode applications such as cognitive radio systems.



Researcher : MUHAMMAD ISHAK BIN ABDUL SUKUR (Master - GRADUATED)

RESEARCH TITLE : HYBRID DIELCTRIC RESONATOR WITH PATCH ANTENNA AT UHF FREQUENCY 

Abstract :
This project proposes a hybrid Dielectric Resonator Antenna with patch antenna, also known as dielectric-resonator-on patch (DRoP) at UHF band ranged from 400 MHz untill 900 MHz. At this particular frequency band, the size of the antennas such as the patch antenna is relatively big. The usage of the hybrid DRA can reduce the size of the antenna, while the patch antenna will help in expending the antennas bandwidth. At lower frequency, the efficiency of the system decreases, so the DRA was used to provide higher system efficiency. This also will later be introduced in the public safety and television broadcasting applications.



Researcher : MUHAMMAD HAZMI MOKHTAR (Master - GRADUATED)

RESEARCH TITLE : COMPACT MICROSTRIP ANTENNA ARRAY FOR POINT TO POINT COMMUNICATION

Abstract:
This project describes the compact design of microstrip patch antenna array operating at 2.4 GHz frequency band for point to point or bridging communication system. The array of four by four microstrip square patch antennas has been investigated with new technique using slot to reduce the existence size of microstrip antenna. The aray of the new antenna will be incorporated with Artificial Magnetic Conductor(AMC) to increase the gain of the antenna. The properties of the antenna is investigated in term of return loss, radiation pattern, bandwidth and gain of the antenna. The performane of the antenna will be compared with the existing microstrip antenna array using the setting up of point to point wireless communication system.



Researcher : KHAIRUL HILMI YUSOF (Master - GRADUATED)

RESEARCH TITLE : SPECTRUM SENSING USING ENERGY DETECTION FOR RECONFIGURABLE ANTENNA

Abstract:
Rigorous development in cognitive radio give birth to software defined radio (SDR) that can somewhat realize the dream of cognitive radio. The SDR can be used with a reconfigurable antenna to achieve the full cognitive radio system. So to prove the concept of cognitive radio system, development on spectrum sensing algorithm that can work with antenna will be carried out. Investigation on the effect of different antenna used and real environment measurement of the cognitive radio need to be done. Initial result shows that a cognitive radio system using energy detection spectrum sensing can perform better in a high SNR value. The probability of false alarm can be reduced if a high number of samples are taken. From the initial result, it can be concluded that if a high gain antenna is used and adequate number of sample is taken, the performance of the cognitive radio system can be boosted


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