Telecommunication Engineering Assignment
The focus of this episode is on a telecommunication engineering project that I carried out during my undergraduate studies at COMSATS Institute of Information Technology (CIIT), Islamabad, Pakistan during the 6th semester from May till November 2011. The title of the project was “Antenna Design for Mobile systems”
I started this project considering this fact that nowadays due to the technological advancement in telecommunication industry there is a dynamic demand and a necessity for having antennas effectively and efficiently designed.
One of the compulsory subjects for telecommunication engineering students at CIIT was a subject titled “Microwave Engineering” which focused on a wide range of antennas and their application in telecommunication industry. For the practical side of this project I decided to consider the design of a multiband antenna. However, I realized that the design of such antennas entail a notable workload and technical knowledge, thus I needed to apply certain restraints to bring the scope of project into feasibility area of my technical expertise. I communicated with my supervisor via E-mail, submission of research proposal and weekly meeting to determine the scale of the work. Ultimately, I commenced my work having in mid to achieve the following:
- Conduct a comprehensive analysis on the fundamentals of antennas
- Designing an antenna and simulating the radiation pattern
- Analyzing the antenna performance
CE2.3) Activities on the Personal workplace
CE2.3.1) Definition of System
At the beginning of the project, I did an extensive research using telecommunication engineering faculty resources on the nature of multiband antennas and chose topics which I could include in my design according to my restraints, such as Operating Frequency and Size, different geometrical characteristics, bandwidth, Standing Wave Ratio (SWR) and Polarization. I defined each parameter in my design by applying proper descriptive formulation and was able to theoretically evaluate the performance of the antenna under ideal conditions.
CE2.3.2) Design and Analysis of Multiband Antenna
After the primary stage, I concluded that the most effective satellite design is multiband antenna. Multiband antenna can provide excellent compactness for a wide number of bands and can work on six bands mainly GSM900.The first step that I took toward the design of this antenna was to simulate a simple structure of it in Simulink and study basic parameters such as return of loss rate, frequency responses, antenna efficiency and etc. Therefore, I used blocks in Simulink and adjusted them by applying mathematical formulation to model a simple antenna that functions under certain frequency and bandwidth. I was able to study the relationship between Return Loss Rate and Frequency fluctuation. Conducting, this simple simulation, assisted me in realising the crucial role of frequency range in determining other characteristics mainly radiation pattern. I planned the design of this antenna on Planar Inverted Basis with small scale. Then, by considering the dimension of the expected frequency and knowing the mathematical fact that the frequency is inversely related to size, I computed the dimension of my antenna. Furthermore, I considered a hypothetical scenario to reduce the size of the antenna by studying techniques like wall shorting and edge bending. Moreover, I considered loops in my design which are suitable for multiband operation with a low radiation resistance. These loops helped me to increase the electrical length without making the antenna bigger and contributed to the enhancement of the bandwidth; moreover, by doing so, I could resolve technical problems regarding with performance degradation which was the explicit result of loops limiting the current on the ground plane.
After, I determined the basic factors for the antenna structure mainly dimensions; I used CST software which allows engineers to make an educated choice for an antenna to serve their requirements to simulate my design. My main objective was to design a compact antenna with high gain covering almost all the applications which are required for wireless communication with a minimum -12dB reference. In the CST environment, I established the Operation and Resonant frequency. Then, I used a high dielectric constant FR4 substrate having a loss tangent of 0.02 to keep the antenna compact and determined its height. The next adjustment was the Patch which I set its dimension to be 16 x 14 mm2. I designed a wave port to allocate to the patch of the antenna for delivering the power to antenna so it can start radiating. I embedded the patch in simulation with full ground plane and had it improved to a certain value to obtain a band near 8 GHz. I adjusted the default value of the impedance and dimension of the wave port. Then, I considered the Partial Ground Plane in the design to obtain higher impedance bandwidth. Next, I added the Air Box to the antenna to acquire the results caused by far field radiation from the patch and ground. Having this information, I computed the dimension of the box. I used CST option to implement meandering on the patch by inserting slits and L-slot.
After adjusting all the dimensions and boundary conditions for the multiband antenna, I conducted different test on the antenna to evaluate its performance. I studied the Return Loss behavior versus frequency and observed that the antenna generates a dip on 1.9 GHz and some on higher frequencies. I was able to shift the dip by manipulating the frequency and observe results closer to my goals. Moreover, I analyzed the Optimization by meandering and grounding which led me to a broaden bandwidth and shifting toward lower resonant frequency. Furthermore, I compared the behavior of the antenna in regard with return loss at different solution frequencies, such as 6 GHz, 700 MHz and 800 MHz. I concluded that over higher frequencies the antenna possesses an acceptable return loss; however, it led to significant decrease in bandwidth. The next level of analysis was radiation pattern analysis. I generated 3D diagrams which depicted the radiation pattern of multiband antenna for different frequencies and the level of gain based on dB. Moreover, Using CST, I was able to investigate the current distribution in the Patch and Ground which was ab easy way for me to calculate antenna impedance, radiation resistance, and reactance.
After this stage, I collated my information in a tabular format and showed that the multiband antenna that I have designed can be used for cellular purposes and wireless communication,
since it can support requirement, such as Frequency Band, Bandwidth and Return Loss necessary for such applications.
This academic assignment which was a part of laboratory assessment was a very good start to learn the basic structure of antenna design and software which are used by professional to study such devices. I was able to model my design mathematically, analyzed it by manipulating different parameters. I was able to satisfy all the expectations of my supervisor and received good feedback concerning my performance.