Research On High Gain Broadband Omnidirectional Printed Antennas

The rapid development of communication technology puts forward higher requirements for the integration of communication systems.As an electronic signal conversion device between communication equipment and free space,the antenna is also developing in the direction of small size and integration.Printed antennas are widely used in the field of mobile communications due to their low profile,simple processing,and ease of integration,which are in line with the trend of miniaturization of today's electronic devices.Omnidirectional antennas are antennas that have no directionality in the horizontal plane and exhibit directional radiation characteristics in the vertical plane.Combining these characteristics,printed omnidirectional antennas have been used more and more widely,especially for small mobile base stations.In this paper,a high-gain wideband omnidirectional antenna with dielectric plate printing is designed.The main work is as follows:(1)four kinds of structures of impedance transformers have been designed.By comparing the simulation results,the triangular structure is selected as the terminal load of the antenna because its simulation result is better than other structures.Compared with the short-circuit or open-circuit terminal structure,this method makes the antenna easier to achieve impedance matching;(2)four printed upright series-fed transducer array antennas were designed and all of them radiate omnidirectionally.Among them,the best performance antenna operates in the band of 4.37-6.38 GHz,the relative bandwidth is 37%,the omnidirectional radiation gain is greater than 3.8 dBi,and the out-of-roundness of the H-plane pattern is less than 1.3 dB;(3)a new type of balun is designed,which changes the complications of the need to perform balanced feed operation on the feeding coaxial line when feeding the symmetric antenna in the past.It is printed on the dielectric board together with the antenna so that the antenna with the balun can be directly connected to the coaxial line;(4)by optimizing the distance between the antenna and the conductive ground,the adverse effect of the mirror antenna on the performance of the actual antenna is reduced.Through the overall optimization of the simulation model with the overall structure of the conductive ground and the radome,the preset targets were finally achieved.The modeling and simulation of all the above antennas were performed by CST Microwave Studio? electromagnetic simulation software.By comparing the simulations results of these kinds of antennas,the antenna which perform best was selected and it was physically fabricated and tested with the Agilent N5227 A vector network analyzer.The measured results show that the antenna operates in the band of 4.4-5.2 GHz,and the gain is greater than 3.2 dBi.The out-of-roundness of the H-plane is less than 2 dB,and the final size of the antenna is 99.1 mm×12 mm×1.6 mm.The performance of t he antenna in the actual environment satisfies the design requirements which proves the correctness of the design idea of this article,and the designed omnidirectional printed antenna with printed turbulence sleeve can be applied in the corresponding communication system.