Research On Performance Of Microstrip Antenna Loaded With Cascaded Hexagonal Ring Metamaterial Structure

Antennas play an important role in transmitting and receiving electromagnetic waves,and their status in wireless communication systems is absolutely pivotal.In recent years,wireless communication technology has grown rapidly,and the requirements of the system on antennas have also been increasing.Microstrip antennas are widely used due to their easy integration with other devices,small size,low production cost and easy fabrication.However,the disadvantages of traditional microstrip antennas such as low gain,poor directivity,and narrow bandwidth have become problems that many scholars need to overcome.The emergence of metamaterials offers a new idea to overcome the shortcomings of traditional microstrip antennas.Electromagnetic metamaterials are artificial structures which are arranged periodically,and their special properties are completely different from conventional materials,for example negative refractive index and inverse Doppler.So they are often used in wave absorbers,hyperlenses,antennas,sensors and other research fields.Introducing electromagnetic metamaterials into traditional microstrip antennas can improve antenna gain performance,broaden antenna bandwidth and realize directional radiation,which is a simple and effective measure to improve the performance index of traditional microstrip antennas.In this paper,the improvement and enhancement of the performance of microstrip antennas which based on electromagnetic metamaterials are selected as the object to carry out research.Two new types of metamaterial cell structures was constructed,which were applied to traditional microstrip antennas,and the performance of microstrip antennas based on the electromagnetic metamaterials were analyzed.The specific research content involves the following points:1.A metamaterial unit with a cascaded hexagonal ring structure was proposed,we analyzed and verified the double negative characteristics of the proposed unit structure,and arranged it periodically then placed it on top of a traditional microstrip antenna as a superstrate to constitute a new microstrip antenna on the basis of electromagnetic metamaterials.The simulation results showed that the designed new metamaterial microstrip antenna worked around 10 GHz.Contrasted with the traditional microstrip antenna,the impedance bandwidth was expanded by 0.25 GHz.The gain was increased by 8.7498 d B,and the half-power beam width of the E-plane and H-plane were reduced respectively.The performance index of the proposed new metamaterial microstrip antenna had been improved in terms of directivity,bandwidth,and gain.On this basis,a cross-shaped slot was further etched to expand the impedance bandwidth of the antenna,which was on the ground plane of the microstrip antenna.The results showed that,based on the metamaterial microstrip antenna above on,the metamaterial slot microstrip antenna based on the cascaded hexagonal ring structure works in two frequency bands.The bandwidth has been further expanded to 0.06 GHz and 0.56 GHz,and the antenna gain after etching the slot is 13.454 d B,which is also significantly improved compared to the traditional microstrip antenna.2.A nested double hexagonal ring structure unit was proposed.The metamaterial had a left-hand frequency band near the two resonant frequencies of 10 GHz and 14 GHz.The double negative characteristics were verified and the arrangement of the metamaterial array was changed.Then it was placed above on the traditional microstrip antenna,and the cross-shaped slot was etched on the antenna ground plane.The results showed that on the basis of traditional microstrip antennas,the nested double hexagonal ring structure metamaterial slot microstrip antennas worked in two frequency bands of 10 GHz and 14 GHz.The bandwidth of the antenna had been expanded.The two working bandwidths are respectively increased by 1.74 GHz and 4.98 GHz,and the gain and directivity are also improved compared with traditional microstrip antennas.The metamaterial unit structure proposed in this paper has certain reference value for enriching the types of metamaterials and the application of metamaterials to traditional microstrip antennas.