Research On A Novel Microstrip Antenna Based On Metamaterials

Traditional microstrip antenna has been widely used due to its advantages such as simple structure,thin profile and light weight,but its disadvantages of narrow band width and low gain are one of the difficult problems in antenna research.In this paper,metamaterials with strange characteristics are used in traditional microstrip antennas to improve the performance.The specific research content can be divided into the following three points:(1)Based on transformation optics theory,the microstrip antenna's size in the virtual space can be achieved enlargement and reduction on the premise of the same size in the physical space,and the working frequency bands of antennas corresponding to different radius of virtual space will be connected to form broadband in our design.Finally,the relative bandwidths of metamaterials loaded in the circular domain and the whole circle domain were 36.2%and 80.0%respectively.(2)The current analysis was used to compare the differences between TM11 and TM21 modes of the circular microstrip patch antenna,and it was found that the central area current of TM11 mode was strong,while the central area current of TM21 mode was close to zero.In this way,the shunt capacitance part(center area)in the equivalent circuit of TM21 mode can be regarded as open circuit.By loading the MNZ metamaterial to the center of the antenna,TM11 mode can move to the high frequency side while TM21 mode barely moves.In this ideal case,a high-gain antenna with a maximum gain of 10.45dBi and a broadband antenna with a bandwidth of 56.45%can be designed.Finally,the MNZ equivalent structures,which are CELC and Meanderline,were found and loaded on the microstrip antennas.Respectively,the highest directivities of the high-gain antenna in two frequency bands reached 8.32dBi and 9.13dBi,and the bandwidth of the broadband antenna was 28.4%.(3)The antenna design is carried out using characteristic mode analysis.By analyzing the far field radiation pattern and surface current pattern of different modes,and loading the low-dispersion structure on the patch antenna,the different modes can be effectively regulated and the antenna with excellent performance can be designed.Finally,two antennas are designed,which are multi-directional broadband antenna and multi-omnidirectional broadband antenna.The former combines two modes radiating towards the z axis to form a broadband antenna of 20.8%,while the latter combines two monopole-like modes TM01 and TM02 to form a broadband antenna with a relative bandwidth of 49.04%.The relative bandwidth and size of the antenna are better than similar antennas,and the maximum gain is up to 8.5dBi.The antenna with metamaterials is designed by combining three different points of transformation optics,modal current analysis and characteristic mode analysis.From these methods,the antennas' performance improve and these works will provide a new idea for the research of novel microstrip antenna.