| In radio astronomy,high-resolution radar,microwave radio relay communication,and other fields in communications,reflector antennas and lens antennas have been widely used.With the development of communication technology,higher performance of antenna system is demanded in daily life.Ultra-wideband,dual-polarization,and other related keywords are constantly being mentioned by researchers.The performance of reflector antennas is actually determined by feed antenna.Ultra-wideband dual-polarized feed antennas reported so far can be categorized into the following types: ATA(The Allen Telescope Array)antenna,dielectric rod antenna,quadruple-ridged flared horn,QSC(Non-Planar Quasi-Self-Complimentary)feed antenna,and Eleven antenna.The first four feed antennas mentioned above usually have some defects in structure or electrical performance.The phase center of ATA feed antenna,for example,changes a lot versus frequency.The overall length of dielectric antenna is too long.And,if there is requirement for broadband performance,materials with different dielectric constants would be needed to fabricate the dielectric rod antenna,which is not easy to carry out.The beamwidths of the quadruple-ridged flared horn are not stable when frequency changes.The existing structures of QSC feed antenna are all made of metal,and applications at higher frequency have not been found up to now.Compared with the feed antennas above,Eleven antenna gets many characteristics that a good feed antenna should have,such as ultra-wideband,stable phase center and stable beamwidth in the whole operating frequency band.An indepth study on the Eleven feed antenna and the specific works have been done:1.A linearly polarized Eleven antenna which works in 5?16GHz is designed.To slove the problem that the feeding structures reported so far are relatively complex and costly,a new type of feeding structure is designed.The new feeding structure integrates the power divider and impedance transformer in the same printed circuit board.With the use of the new feeding structure,the two differential ports of the same polarization can be combined into one port,which will make an additional power divider unnecessary and simplify the overall structure of the antenna.A prototype is manufactured to verify the simulated results.The measured voltage standing-wave ratio is almost the same as the simulated one and the measured radiation patterns are very similar to the simulated patterns,which verifies the accuracy of simulations.2.To work out the backlobe problem caused by applying the feed structure of the single-polarized Eleven antenna to the dual-polarized Eleven antenna,a new type of feed structure suitable for the dual-polarized Eleven antenna is designed.And then,a dualpolarized Eleven antenna that works in 5?16GHz,in which the novel feeding structure is used,is designed.The feeding structure becomes more complicated because of the requirement of dual-polarization.Two groups of feeding structures are designed to excite the dualpolarized Eleven antenna.The first group of feeding structures is obtained by slightly changing the size of the feeding structure used in linearly polarized Eleven antenna.However,the back lobe level is very high when the first group of feeding structures is used,which will decrease the gain of the main beam.To suppress the back lobe level,the second group of feeding structures is designed.The second group of feeding structures can also adapt to the situation that higher working frequency will lead to a smaller physical central area,which provides a new feeding scheme for the high-frequency application of the dual-polarized Eleven antenna.To verify the correctness of this design,a prototype is manufactured.The measured results show that the voltage standing wave ratio and the shape of radiation patterns are just the same as simulated ones.Therefore,the simulations are verified experimentally and numerically. |
PDF Full Text Request