Research Of Broadband Circularly Polarized Antennas And Filtering Antennas

As an important RF front-end device in wireless communication system,the performance of antennas affects the whole communication quality.Improving the performance of the antennas has become an inevitable research direction.Among which,the circularly polarized antennas has the advantages of anti-polarization mismatch,anti-faraday rotation effect.Moreover,the circularly polarized antennas can receive the linearly polarized wave in any direction and circularly polarized wave can be received by the linearly polarized antennas regardless of any form of polarization.Circularly polarized antennas have been widely studied for their advantages over linearly polarized antennas.Dual-circularly polarized antennas can radiate both left-circularly polarized and right-circularly polarized waves within the same frequency band.One pair of dual-circularly polarized antenna can realize the functions of two antennas,which can improve the utilization rate of spectrum resources and alleviate the problem of spectrum resource shortage.In order to realize device miniaturization,filtering antennas are proposed.Filtering antennas can reduce the using of filters by integrating filtering and radiation performance.For the antennas,the wider the bandwidth is,the larger the communication capacity will be.So the broadband antennas have great research value.In this paper,several circularly polarized antennas and filtering antennas are designed based on the broadband technology.The main work is as follows:1.A broadband circularly polarized slot antenna is proposed with 55.06%(2.04GHz-3.59GHz)frequency band.The slot antenna fed by a microstrip is composed of a square slot and a Z-shaped radiation patch.A wide bandwidth can be obtained by reasonably adjusting the size of the Z-shaped radiation patch and its relative position in the square slot.Based on the circularly polarized slot antenna,a dual-frequency tri-polarization slot antenna is designed.2.A broadband dual-circularly polarized slot antenna is proposed,which can work in 1.65 GHz-3.88 GHz(80.65%)frequency band.The antenna is composed of a square slot and a chamfered square radiation patch.The antenna fed by coplanar waveguide(CPW),there are two feeding port,when one of the ports inputs signal,another port matched with a 50 ? impedance load,the antenna radiates one of the left-hand or right-hand circularly polarized wave.The two types of circularly polarized waves work in the same frequency band.Good isolation between the two ports is obtained by some technical methods.3.Two broadband circularly polarized dipole antennas are proposed.One of the antennas to increase the antenna gain by adding a director like the Yagi-Yuda antenna.The other antenna achieves broadband circular polarization performance by etching slots and chamfering the radiator.These two antennas are fed by a coaxial cable,and have obtained 55.57%(1.77GHz-3.0GHz)and 68.13%(3.3GHz-6.71GHz)circular polarization bandwidth respectively.Based on the broadband circularly polarized dipole antennas,two band-notched wideband circularly polarized antennas are proposed.4.A broadband filtering antenna is proposed.The filtering antenna is composed of a ground with a dumbbell-shaped slot and a microstrip feeding structure.A pair of SIR are loaded on both sides of the microstrip feeding line and a pair of parasitic patches are loaded in the dumbbell-shaped alot,which not only broadens the bandwidth of the antenna,but also improves the gain rectangularity of the antenna,thus the filtering antenna have achieved good filtering performance.