Low Profile, Low Frequency Metamaterial for Sub-GHz Microwave Application

Electromagnetic metamaterial is composites consisting of sub-wavelength structures designed to exhibit particular responses to an incident electromagnetic wave. In general, the electromagnetic metamaterial is at wavelength scale or sub-wavelength scale and these metameterial are applicable for high frequencies applications which fall into range from 10 GHz to 20 GHz. The application of metamaterial for sub-GHz application is little discussed in the past decades. In this thesis, by incorporating novel structures (like 3D SRR (split ring resonator)) and new loading materials (like ferrite composite film), the unit cell size of metamaterial has been successfully scaled down. Small-scale unit cell allows electromagnetic metamaterial to have far greater flexibility in various applications. This thesis describes the design, mechanism and development of low profile, low frequency metamaterial for sub-GHz microwave applications.;To offer a better understanding of electromagnetic metamaterial, we firstly examines those traditional types of electromagnetic metamaterial including: electromagnetic band gap ("EBG"), frequency selective surface ("FSS"), and negative index material ("NIM"). Based on review on traditional designs, we described several novel metamaterial designs, among which we demonstrated a mushroom-like metamaterial, a novel 3D split ring resonator ("3D SRR") design, and ferrite composite film loaded metamaterial. Both analytical and numerical simulation models are used to analyze this innovative metamaterial. The simulation and preliminary measurement results demonstrate the metamaterial developed in this thesis can significantly reduce the resonant frequency of metamaterial. In the meantime, these novel structures also demonstrate the reduced the size of unit cells.;Then, the bulk material property of the metamaterial is retrieved from the unit cell. The retrieval methodology is introduced, which is an effective medium model for the metamaterial. The bulk material properties could be retrieved from the scattered parameters, S11 and S21. The retrieved material property clearly shows that the metamaterial exhibit both negative permittivity and permeability at certain frequency, which means the refraction index at these frequencies is negative. The bulk material simulation shows that the metamaterial could be used as electromagnetic flat lens.;By incorporating this structure, low profile sub-GHz metamaterial is completely achievable for various real life applications. The second half of this thesis demonstrates the vast applications of these metamaterial, especially for sub-GHz microwave applications such as RFID (Radio Frequency Identification). Four kinds of metamaterials are used for this application, the mushroom-like metamaterial as a reflector, the single unit cell metamaterial as a RFID tag, the 3D SRR (Split Ring Resonator) as a flat lens, and the metamaterial surface antenna. These measurement results showed that the incorporation of metamaterial could significantly improve the performance of RFID device in various applications including some problematic deployments such as in metallic environment.