| With the great improvement in the communication technology,the performance requirement of the omnidirectional circularly polarized(CP)antenna is strict by modern communication systems,especially for the wireless communication network and broadcast system.With the background of this,a novel omnidirectional CP antenna based on the coaxial waveguide structure with perpendicular slot pairs is reported in this paper.The main contents of the paper are as follows:First,an electromagnetic model is researched,and with this foundation an omnidirectional CP antenna based on the coaxial waveguide structure is designed and it works in 5GHz frequency band.The antenna realized the omnidirectional CP property by setting four rounds of the perpendicularly slot pairs on the out conductor of the coaxial waveguide along axis and every round of slots contains four slot pairs around axis.The test results and the simulation results of the antenna are coincident.Second,with the design foundation of the omnidirectional CP antenna,a high gain omnidirectional CP antenna with 9dBic gain is designed by setting more rounds of the slot pairs on the out conductor of the coaxial waveguide,and the size of the slots are optimized to balance the feeding power to each round of slots.Third,a dual-CP omnidirectional antenna is designed utilizing the character of transmission line and the principle of the circularly polarized.The RHCP port and LHCP port are assigned in the two sides of the coaxial line respectively.Compared with the antenna designed before,the dual-CP omnidirectional antenna is designed with a simpler structure in the match and feeding part.At last,a novel T shaped coaxial connection line is designed to feed the omnidirectional CP antenna and the upper directional antenna which constitute the space diversity system and realize space coverage with different antenna.The two antennas in the space diversity system are independent with each other and with no effect with each other. |
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