Design Of Miniaturized Electromagnetic Band Gap Structure And Its Application In Microstrip Antenna

Recently, the electromagnetic band Gap (EBG) structure, as one of the novel artificial materials, has been significant interested in researching. It presents some unique characteristics, such as forbidden band gap, in-phase reflection, etc. EBG structure can be used in antennas design to improve their characteristics, such as improving the radiation patterns, enhancing the gain, and reducing the sidelobe and backlobe levels, etc. So the EBG structure satisfied the modern wireless communication technology requesting the high performance antenna,and is applied widely in the microwave communication.With the requirement of the practical applications, the research works presented in this paper focuses on miniaturized compact EBG structures and improving the performances of the microstrip patch antennas. Firstly, several types and analyzing method of EBG structure are summarized. This paper expatiates on the basic theory of HIS EBG structure, including the LC equivalent circuit model, the study on the properties of the EBG structure and the surface wave suppressed. In addition, a number of measurement methods are introduced briefly in the paper.Secondly, the design methods of miniaturized EBG structure are discussed in details here, which contain the methods of increasing the equivalent capacitance and increasing the equivalent inductance. In this paper, the second method is adopted to introduce double reverse split rings (RSR) into the square patch to increase additional inductance, reducing the EBG cell size. The band-gap of the Spiral-like EBG structure is simulated and researched by Ansoft HFSS 11. Based on the theory of the loaded planar spiral inductance, a novel RSR (Reverse Split Rings) EBG structure is designed, for the small design of the EBG structure. The measured results show good agreements with the simulated results which show that the size of EBG cell is reduced, and the band-gap achieves bandwidth. It is also analyzing the effect of changing several parameters of the RSR EBG structure in details.In the end, the applications of miniaturized EBG structure on microstrip patch antennas are studied, which is mainly used to suppress the surface wave, in order to improve the antenna performances. The work is mainly focused on:(1) A fractal microstrip antenna is implemented using the EBG structure as a ground plane, and the measured results show that the reduction in the surface wave level is remarkable. Resulting in the backward radiation of the antenna suppressed. (2) The EBG structure is integrated between two fractal microstrip antennas to reduce the mutual coupling. Furthermore, more EBG cells are added around the patches, the mutual coupling is reduced more effectively. (3) The EBG structure is integrated between two broadband microstrip patch antennas to reduce the mutual coupling in the whole broadband frequency ranges. (4) The spiral-like EBG structures are placed into the middle of the dual-polarized antenna array, the simulated results show that the mutual coupling of the same polarization ports and cross-polarization ports are reduced in the whole working frequency ranges, and the backward radiation is also reduced. On this method, the dual-polarized antenna array having 12 units is fabricated and measured. Compared with the conventional antenna arrays, the experimental results demonstrate that the mutual coupling of the same polarization ports and cross-polarization ports are reduced and the backward radiation is decreased, and the gain is increased, making it more suitable for practical engineering applications.