Research And Design Of Broadband Magnetoelectric Dipole Filter Antenna

With the rapid development of wireless communication system,antennas have been developed towards multi-functional and high performance since they are the key component of the radio frequency front-end.As a kind of complementary antenna,magneto-electric(ME)dipole antennas have the characteristics of wide bandwidth,similar radiation patterns of the E-plane and the H-plane,low back lobe level,and low cross polarization.Thus they are very suitable for base stations of the mobile communication systems.However,most of the reported magneto-electric dipole antennas have been designed to improve their performance within the operation frequency band.Accordingly,if the filtering function can be integrated into the ME dipole antennas to realize wideband filtering antennas,it will be more efficient to solve the problems of the shortage of spectrum resources and reduce the loss brought by the connection of antennas and filters.Given that,we proposed two wideband filtering ME dipole antennas without introducing additional filtering circuits.The main work of this dissertation is summarized as follows:1.This thesis investigates the research background and status of the magneto-electric dipole antennas and filtering antennas to clarify the significance and application context of this research.Then the theoretical knowledge involved in this paper,including relevant performance indications of antennas and the working principle of the magneto-electric dipole antenna have been introduced,providing the basis of this study.2.The classic magneto-electric dipole antenna has been analyzed at first.As the antenna exhibits a band-pass filter response,but there are harmonics in the higher frequency out of the operation band.Thus we presented a wideband magneto-electric dipole antenna with third harmonic suppression by modifying the structure of the classic magneto-electric dipole antenna.The impedance bandwidth is effectively increased to 79.3 % by adding a parallel branch line to the horizontal part of a ?-shaped strip feedline.In addition,an open stub with quarter-wave length is loaded on the ?-shaped strip to introduce a radiation null in the high frequency out of band,suppressing the harmonics.The out-of-band suppression level of the antenna is further improved by etching slots on the edges of the patches.Finally,a third harmonic suppression level better than 11 d B is achieved.3.A dual-polarized broadband filtering magneto-electric dipole antenna based on C-slot is proposed.First,two pairs of trapezoidal horizontal patches are adopted to achieve wider bandwidth.Then a pair of orthogonal ?-shaped strip feedlines are used to realize two orthogonal linear polarized waves.Besides,the strips are bent respectively to improve the isolation between the two feeding ports.And a box-shaped reflector is placed under the antenna to improve the gain.Specifically,a radiation null can be introduced at the upper out-of-band by etching C-shaped slots on the horizontal patches.Combing the radiation null brought by the feeding structure at the lower out-of-band,the proposed antenna exhibits a band-pass filter response with sharp skirt selectivity.