Contextual Factors Impacting the Engineering Discipline
This particular part of the study focuses on an engineering project that is managed by me as team leader during my undergraduate studies at COMSATS Institute of Information Technology (CIIT), Islamabad, Pakistan during the 7th semester from February till August 2012. The title of the project was “Multiband Antenna Design for GSM & WiMAX”
I chose this topic of research for our work, due to the fact that GSM and WiMAX are contextual factors impacting the engineering discipline in the field of telecommunication industry.
Antenna & Radio Wave Propagation was a subject which its assessment was tailored based on theoretical and practical assessment. As for the practical part of the project I assembled a group of 2 engineering students to embark on a research on the design of multiband antenna. I liaised effectively with my supervisor to understand the requirement of the project and what was expected as the outcome of this assignment. After briefing my teammates on the scope of the work, I set our main goals as:
- Presents a study on multiband antenna with slots embedded in the patch.
- Analysis of parameters, such as return loss and radiation pattern plots.
- Studying methods for performance enhancement
I applied my engineering management skills to develop a friendly environment to establish mutual understanding, respect and collaboration. I managed the project by conducting fortnightly meetings and discussion on techniques and plans required for completing each phase.
CE3.3) Activities regarding personal engineering
CE3.3.1) Stage of the entire research
In this chapter, I intend to briefly explain the theoretical side of the project that I personally carried out. Firstly, I focused on one of the most important characteristic of antennas which is Radiation Pattern. In order to do so I studied many text books and technical articles which arte published by antenna manufacturing company. I used this information alongside of my learning from subjects, such as Telecommunication System modelling and Microwave to develop mathematical formulas which could predict the behaviour and pattern of radiation. In my formulation, I analysed the role of parameters, like single frequency, polarization, single plane cut, density of the power flux, intensity of the radiation, Field strength and Directivity. Moreover, I employed partial differential equations to study other significant properties, such as radiation pattern lobe and the characteristics of surrounding lobes. Moreover, I developed a comprehensive understanding in calculation and manipulation of factors, such as Gain, half power beamwidth, First-Null Beamwidth and etc.
CE3.3.2) Antenna Comparison
In this stage, I used the mathematical formulation that I had developed in the previous step to simulate different type of antenna in NEC software, so I could prove scientifically what type of antenna can serve our purpose best. NEC is designed for engineers to study antennas capabilities mainly radiation pattern and physical characteristics such as shape. I used the rich library of this software and used its options to choose different antennas and had antennas, such as Wire Antenna, Array Antenna, Reflector Antenna, and Micro strip Patch Antenna simulated for certain frequencies and wave length. I ran the simulation for my modelled antennas and investigated the difference between their gains, radiation pattern, power flux, directivity and etc. Finally, I wrote a technical report on the results of my simulation and presented to my team and could convince them by presenting solid engineering fact that the best antenna for our design is Micro Strip Type.
CE3.3.3) Antenna Structural Design
The main objective of the project was the design of antenna based on our engineering knowledge and application of telecommunication system principles. Firstly, I studied the
physical structure of such antennas by investigating physical properties, such as its metallic patch which is made of pure copper, length and width of substrate and the assembly of different parts. This study assisted me to understand how to design the mechanical parts of the antenna which we were aiming for and achieve the proper level of dielectric constant and create a topology which could obtain suitable bandwidth. I used this information to determine factors, such as Effective dielectric constant, Dielectric constant of substrate, Height and Width of substrate. The next step for me was to determine how to feed the radio waves to the rest of the antenna structure. I used Coaxial Probe Feed technique. Firstly, I had this technique modelled by an equivalent circuit with the rest of antenna by applying my knowledge from Electrical Circuit Analysis. I have found some issues in this part of the project which was the density of the dielectric. This problem disturbed the bandwidth of the antenna and made it narrow. I resolved this challenge by employing impedance matching method. I took this fact into account that because coaxial probe feed has size limitation, had I increased the size probe it would have been more inductive which was not acceptable, therefore, I used a coaxial probe of higher resistance to conduct impedance matching.
CE3.3.4) Antenna Simulation
In the next stage, I used HFSS simulator to equip my antenna with the properties to be used for GSM and WiMAX applications. Firstly, I studied IEEE 802.16-2004 WiMAX standard and selected principles which could fit the bill of our design. I used a wide range of formulation to calculate parameters required for WiMAX setup, such as Frequency Band, Bandwidth, Data Rate, Bit Rate, and did spectrum analysis for frequency band of 2.2 GHz and 3.5 GHz which is considered the WiMAX operational range in Pakistan. I also investigated GSM subsystems, such as Network and Switching Subsystem (NSS), Base Station subsystem (BSS), and Operations support system (OSS) and simulated their architecture in HFSS simulator for 800-1800MHz. In HFSS simulator, I visualized 3D design environment and studied the behavior of electromagnetic waves. Ultimately, I modelled an antenna for GSM and Wi-Fi using probe feed. The length of antenna resonant frequency is manipulated by me and considered slots current path changes and return loss. I ran the simulation for three resonant modes of TM02, monopolar patch, and top loaded monopole mode with conical radiation pattern. I embedded air in between the space of ground and radiating patch in my simulation in order to get monopole radiation pattern. I generated figures describing the relationship between geometry and pattern of projected rectangular-shaped antenna for dual-
band operation. I also applied corner truncation technique to improve return loss, gain, bandwidth and radiation pattern. I also used the options of the simulator to employ slits and slots to improve the effectiveness of electrical length of the patch. Moreover, I studied the GSM application by using probe feed. I configured the geometry of proposed rectangular-patch antenna for dual-band working on a substrate of thickness of 2.4mm and the dielectric constant of 4. I activated my simulation for the frequency range of 0.5GHz to 3.5GHz. The result of my simulation was the computation of loss of dual band patch antenna obtained at two resonant frequencies. I also noticed that by applying slits and slots, I could improve the return loss from 1.82 GHz to 2.07 to 1.68 GHz to 2.14 GHz which showed that the antenna can works with GSM band running frequency.
The above mentioned engineering activities were a brief explanation of overall technical deed carried out by me personally. I had to this opportunity to practice management and communication skills which resulted in leading the team effectively and properly. Moreover, performing mathematical analysis, simulation with NEC and HFSS and employing the principle of telecommunication engineering helped to deepen my knowledge and technical experience. All the objectives of this project were achieved successfully and the final report was submitted on time.