| With the smooth launching of Tiantong satellite,China has finally filled in the gap of satellite communications.Thus researches for satellite communications will become a hot topic in the antenna area.Basing on the combination of satellite communication antennas and the traditional handset antennas,the paper designs and fabricates three antennas.The three antennas are an S-band “Connection in moving” antenna,a dual-band linear polarized antenna and a combined antenna of linearly polarized antenna and circularly polarized antenna.The first antenna is the S-band “Connection in moving” antenna,which is based on the circularly polarized microstrip antenna.By forming an array the radiation gain is increased,which means the antenna has the ability to transmit large amounts of data.to maximize the communication capacity,the radiation beams are controlled from the elevation angle 15° to 90°,only by changing the feeding phase.During the design,the dual-band circularly polarization of the unit is realized by the structure of the double-layer microstrip,and the ratio is optimized by rotating the units.The measured results of the antenna show that VSWR is less than 1.5: 1.With only three beams the antenna's radiation pattern could cover the whole angle range,which requires a 10 d Bi-gain.Also,the axial ratio of the main direction is less than 1d B.The second design is a dual-band linearly polarized antenna.This antenna is comprised of two whip antennas,with only one port.Through the flexible using of capacitors and inductors,the design combines the two antennas together,which could both ensure the antenna's performance in each band,and the entire size of the antenna.The measured results show that the VSWR in the two bands(400MHz~ 470 MHz and 2.33 GHz ~ 2.55GHz)meets the requirement of less than 2:1,and the radiation pattern is omnidirectional in the horizontal plane.On the basis of the second antenna design,this paper presents two kinds of UHF and S-band combined antennas.The two forms are single-port and dual-port.According to the requirements,the UHF antenna operates from 400 MHz to 678 MHz,with VSWR less than 3:1,and the polarization mode is vertical polarization.The S-band antenna operates from 1.98 GHz to 2.01 GHz and 2.17 GHz to 2.2GHz,with VSWR less than 2:1,and the polarization mode is left circularly polarization.During the design of the S-antenna,we combine two helix antennas together,which can resonate at two frequencies respectively,and then match the impedance of the combined antenna,so that the antenna can meet the requirements in both two bands.In the design of UHF antenna,two ideas are used.The first one is a single-port structure.Similar with the second antenna,a slot is put on the S antenna's feeding line,and then the matching network is loaded at the place.This approach is somewhat more complicated relatively,when taking the impedance matching problem of the S-band antenna into account.And it is proved that the measured results of the antenna could meet the requirements if inductors and capacitive are used correctly.The second design is a dual-port structure,directly connects the UHF antenna's feeding line to the helix antenna's outer conductor,and then designs the impedance matching network of UHF antenna.This is a relatively simple solution for the antenna,because it would not have big impact on the performance of S-band antenna,also the matching network is easy.However,one thing should be noticed that choke measures should be loaded on the S antenna feeder to prevent the UHF current from short-circuiting.Results shows that when the antenna is working at the S-band,the gain is higher than 2d Bi during the elevation angle from 55° to 90°,and the axial ratio is less than 3d B,also when the antenna is working at the UHF-band(400MHz~678MHz)the gain of the antenna in the horizontal direction is higher than 0d Bi.In this paper,the three antennas are designed under a certain circumstance,and to some extent could have a large application prospects. |
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