Research On Multi-Band And Broadband Metamaterial-Inspired Electrically Small Antennas

In order to meet the requirements of wireless communication, researchers have given much attention recently to dual-band and broadband antennas. Since their potential impact is large, there has been much more focus on electrically small antenna technologies. The metamaterials have been a topic of high interest in recent years, and the radiation efficiency of electrically small antennas could be highly increased due to the introduction of the meta-material. In this paper, research on metamaterial-based and metamaterial-inspired electrically small antennas is carried out based on the theory of electrically small antennas and metamaterials.This dissertation is mainly concerned with the design of dual-band and broadband metamaterial-inspired electrically small antennas. The major contributions are outlined as follows:1. The theories of electrically small antennas and metamaterials are summarized, and the characteristics of metamaterial-based and metamaterial-inpired electrically small antennas and the method of the equivalent circuit are focused on.2. A novel efficient dual-band electrically small antenna is presented. This antenna could match the feed source to realize self-resonance with the introduction of a parasitic element instead of a matching network. The resonant frequencies are 776MHz and 920MHz, and the radiation efficiencies for these two resonance frequencies are 93.08% and 70.18%, respectively. Thus an efficient dual-band electrically small antenna is obtained.3. This part summarizes some common methods of broadband antennas such as adding a broadband matching network, the lump element loaded antenna and so on. Then a scheme for the broadband metamaterial-inspired electrically small antenna is proposed. To achieve a high efficiency in the frequency range of 440MHz≤f≤692MHz, the function of the capacitance of the capacitor in the near field of the antenna to the frequency is derived.