Design And Research Of Novel Microstrip Antenna Based On Metamaterials

In recent years,with the development of science and technology,the modern wireless communication system has been upgraded and renewed,which has also put forward higher and higher requirements for wireless communication equipment.As an indispensable part of the wireless communication system,the antenna must also develop towards multiple frequency bands,high gain,miniaturization,wide band and high isolation.The traditional microstrip antenna has the advantages of low cost and easy fabrication,but it can not meet the increasingly stringent demand brought by the development of the times,and the emergence of metamaterials opens up a new path for the research and design of new microstrip antennas.Metamaterials are an artificial medium different from natural materials.By arranging some periodic structures reasonably and orderly in size and shape,it can obtain the electromagnetic properties which are not available in the natural materials,by using these new materials can break through the traditional electromagnetic theory in microwave devices,which can greatly improve their performance.In this paper,we investigate the performance improvement of traditional microstrip antennas with the addition of metamaterials.The specific research contents and achievements are summarized as follows:First,antenna as the transceiver front-end of modern wireless communication system,the dual band or multi-band frequency performance can allow a device to receive and transmit multiple frequency band information with only one antenna,which can achieve better efficiency and low cost performance.On this question,two new metamaterial multiband antennas for WLAN and WiMAX are proposed based on the traditional microstrip antenna.The antenna 1 adds a 5.8 GHz high-frequency band compared to the original antenna at 3.5GHz by etching 2x3 complementary split ring resonator elements on the backside of a simple monopole antenna.Two working bands can be used to WiMAX 3.5 GHz and WLAN 5.8 GHz bands.The antenna 2 by etching a complementary split ring resonator unit slot on the patch of a simple traditional microstrip antenna,a triple-band characteristic is formed and three working bands operating at 2.45 GHz,3.5 GHz and 5.25 GHz.It can be used to WLAN 2.4GHz,WiMAX 3.5 GHz and 5.25 GHz bands.Meanwhile,two designed multi-band antennas have a good impedance matching characteristic,a high gain performance and an omni-directional radiation patterns.Second,the gain is one of the basic performance parameters to measure the antenna radiation ability,the wireless communication system is directly determined by the performance of antenna gain,and a high performance defect of microstrip antenna is its low gain.Aiming at this issue,two new metamaterial units are designed based on the metamaterial theory,and the gain of the original antenna can be improved by the means of loading and covering.First,a metamaterial unit with nearly zero refraction is designed,which refractive index is close to zero in the 4.3 GHz-4.5 GHz band,and by covering the proposed metamaterial unit with original antenna,the gain of the original antenna can be increased by nearly 3 dBi in the working frequency band.Then,a modified complementary split ring resonator structure was designed and found that it have negative permeability at 4.8 GHz-5.5GHz through retrieving.By loading them around the original microstrip antenna,2 dBi gain promotion can be achieved.When the two antennas increase the gain,the resonant bandwidth and radiation characteristics are almost not affected.Third,multi-input multi-output(MIMO)technology has the advantages of greatly improving the spectrum and channel capacity,reducing multipath propagation and so on.And the MIMO antenna has been widely concerned,but the mutual coupling between the radiating elements of the MIMO antenna has restricted the further development of the MIMO antenna,because the high mutual coupling will affect the performance of the antenna bandwidth,directional pattern and so on.Aiming at the above problems,two methods to improve the isolation of multi-input multi-output(MIMO)microstrip antenna are proposed by using the theory of metamaterials.First,modified complementary split ring resonator units are applied to both sides of the MIMO antenna,which can improve the isolation between the two antennas by as much as 23 dB with respect to the original antenna.Then,a new type of3-dimensional metamaterial structure unit is designed.The S-parameters retrieval method is used to retrieve the electromagnetic parameters of unit,and find that it has the negative permeability characteristic,and embedding five three-dimensional metamaterial units to the substrate between two radiation patches,about an isolation promotion of 20 dB is achieved.When the two antennas are used to improve the isolation between antenna elements,the resonant bandwidth and radiation characteristics of the antenna are only slightly affected.