Author:
Hakkı TORAN
Year:
2012
Abstract:
In this thesis, fundamental concepts of metamaterials and electromagnetic wave propagation in metamaterial medium, brief theory of transmission lines, and CRLH transmission line approach to metamaterials are introduced. Using the concept of CRLH metamaterial, compact size ultra-wideband metamaterial antennas are designed and implemented Antennas are excited by a coaxial feed. The shape of the antenna is tapered to provide impedance matching over a wider band. Furthermore ring slot is opened on the radiating part of the antenna; however spurious resonances emerged within the frequency band of the metamaterial antenna. Using rectangular split-ring slots instead of rectangular ring slots eliminated those unwanted resonances and improved the voltage standing wave ratio (VSWR) frequency bandwidth and gain of the antenna. The final antenna, compact size ultra-wideband antenna with split-ring slot, has VSWR value<2 from 3.8GHz to 16.4GHz according to simulation results, 4GHz to 17.5GHz according to measurement results. Although the designed and realized antennas have very compact sizes overall dimensions of the antenna are just 18mm x 26.2mm, they can successfully cover a large spectrum. The final antenna has an omni-directional radiation pattern. During design a commercial 3D electromagnetic solver program FEKO was used to simulate the antenna and obtain antenna evaluate the results. Metamaterial antennas designed and simulated using FEKO, are fabricated on a FR4 substrate with dielectric constant 4.3?_0 and thickness 1mm. Voltage standing wave ratio and input impedance of the fabricated antennas are measured using a network analyzer. The results obtained from measurement and simulation are in good agreement with each other.