Research On Wideband Low Profile Microstrip Antenna Based On Periodic Structure

With the rapid increase of modern wireless communication data service,the wireless communication system's demand for wideband is constantly increasing.And the coexistence of multiple communication systems also requires the antenna to cover multiple communication frequency bands at the same time.In addition,the low profile antenna can effectively reduce the size and occupation space of the base station antenna,saving the cost of antenna manufacturing,but also has the characteristic of the light weight.In recent years,the wideband low profile antenna has attracted extensive attention.In 2014,Z.N.Chen of the National University of Singapore proposed a new wideband low profile antenna based on a periodic microstrip structure with slot coupled excitation to achieve a 0.06 ?0 profile height and a 25%impedance bandwidth.To further expand the bandwidth,in 2017,Z.N.Chen proposed a wideband low profile super surface antenna consisting of a diamond slotted patch with a profile height of 0.07 ?0 and a bandwidth of 31%.Although this antenna achieves good low profile and radiation characteristics,its operating bandwidth is still narrow and cannot meet the wideband requirements of wireless communication systems.Therefore,it is of great significance to study the antenna with wideband and low profile characteristics.Based on the theory of microstrip antenna,two wideband low profile microstrip antennas based on the periodic structure are designed by combining periodic structures with the microstrip antenna.The antenna can not only meet the performance requirements of wideband and low profile at the same time but also has the advantages of simple structure and low cost.The main work of the thesis is as follows:(1)A wideband low profile microstrip antenna based on the periodic structure is proposed.The antenna radiating structure is composed of 20 square patches arranged in a periodic manner.The differential feeding and the asymmetric slot coupling structure are used to excite multiple resonant modes,which effectively expands the impedance bandwidth of the microstrip antenna.The test results show that the impedance bandwidth that less than-10 dB is 2.94-5.3 GHz,the relative bandwidth is 57.3%,the average gain of the antenna is 5.26 dBi,and the height of profile is 0.044 ?0(A0 is the wavelength of 4 GHz in free space),has good radiation performance.(2)A wideband low profile dual polarization microstrip antenna with a high isolation degree is proposed.The main radiation structure of the antenna is composed of 16 square patches,distributed symmetrically in the center.The two ports adopt an independent double aperture slot coupling feeder structure,which can effectively avoid the intersection of the two ports feeders and improve the isolation degree between the ports.The simulation results show that the S-parameter impedance bandwidth less than-10 dB completely covers 3?5 GHz,and the relative bandwidth is greater than 50%,and the port isolation is greater than 38 dB.The peak gain obtained in the band is 10 dBi and the total height of the antenna is 0.046 ?0.