Study Of Microstrip Antenna Based On Electromagnetic Metamaterials

Metamaterial is a kind of artificial composite structure, which is composed of periodic sub-wavelength metallic structures. Metamaterials can generate electric or magnetic resonances with electromagnetic waves under certain frequencies, thus they possess some special electromagnetic characteristics that are non-existent in the nature. Scientists have been making great efforts to apply the special electromagnetic characteristics of metamaterials into practical projects. Microstrip antenna is one of the most popular antennas used in wireless communication systems, and it has many advantages, such as simple structure, small size, light weight, low profile, low cost, easy to integrate and fabricate. In the case of designing and appling microstrip antenna, metamaterials show enormous potential in improving radiation performance of microstrip antenna, as well as miniaturizing size of microstrip antenna. Therefore, it is of great significance to study microstrip antenna based on metamaterials, which will improve the performance of antenna as well as communication qualities.In this thesis, the design and applications of microstrip antenna based on electromagnetic metamaterials have been discussed and studied. The main contents included research on improving directionality of microstrip array antenna by using electromagnetic metamaterials, research on reducing RCS(Radar Cross Section) of microstrip antenna by using metamaterial absorbers, and research on designing multi-band microstrip antenna by using complementary metamaterial structures, as well as research on using metamaterial unit cells as radiating patches of omnidirectional microstrip antennas.Firstly, we introduced the basic theories of metamaterial and microstirp antenna. The method for extracting equivalent electromagnetic parameters from metamaterial unit cells is mainly introduced. We also used the metamaterial model in the literature to verify the correctness of our simulation method for metamaterial structures. Secondly, a small size of metamaterial structure was placed between the array elements of the microstrip array antenna, and then the surface wave of the antenna was effectively suppressed because of the wave notching characteristics of metamaterial structure. Therefore, coupling between array elements was greatly reduced and directionality of the whole antenna was improved. Thirdly, after loading designed periodic metamaterial absorbers on a coaxial microstrip antenna as conformal parts, directionality of the antenna was improved, at the same time, the RCS of the antenna was greatly reduced, and the maximum reduction of RCS is 24.4 dB. Fourthly, a complementary metamaterial structure was etched in the radiating patch of a conventional microstrip antenna, and then an additional working frequency band can be generated at lower frequency range by electromagnetic resonance of the complementary metamaterial structure. Therefore, a multi-band and miniaturized microstrip antenna can be realized by this method. Finally, two multi-band omnidirectional microstrip antennas were designed by using metamaterial unit cells as their radiating patches. The working frequency bands of the two antennas are both produced by magnetic resonances of each radiating patch. Experimental results show that these two antennas can work in Mobile 4G, WLAN, WiMax and other frequency bands. Besides, the two antennas meet the communication requirements of wireless sensor networks (WSN). One of the two antennas is a miniaturized microstrip antenna, the electrical size of which is only 0.18?×0.144?×0.013?, and reduced by 40% compared with conventional microstrip antennas, and then miniaturization of microstrip antenna is therefore effectively realized.The above research results can provide a reference for the application of metamaterial structures in microstrip antenna and the design of miniaturized microstrip antennas.