| The communication rate and quality of modern millimeter-wave communication systems continue to improve,placing higher demands on the polarization characteristics and frequency band count of antennas.For example,the high polarization isolation,in the fixed wireless access scenario in the W-band,where the application is allocated a narrow bandwidth,the dual-polarization In-Band Full Duplex(IBFD)technology can effectively improve its spectral efficiency.Technically,it is necessary to ensure that the two cofrequency signals that work simultaneously do not interfere with each other,typically requiring the dual-polarization antenna to have an isolation degree of over 50 d B to alleviate the pressure of improving the isolation in the signal processing circuits.Another example is the wideband wide-angle circular polarization.In Ka-band satellite communication using circular polarization beams,antennas in mobile platform applications need to have beam scanning capabilities.However,achieving the wide bandwidth and wide scanning range of circular polarization beams remains challenging.In addition,Ka-band satellite communication uses 20 GHz/30 GHz dual-frequency transceivers.Traditional devices using separate antennas require two antennas for receiving and transmitting to establish the uplink and downlink,resulting in larger satellite communication equipment.The industry hopes to integrate the receiving and transmitting antenna in the same aperture to reduce the system size.To address the above requirements,the polarization control and multi-frequency aperture-sharing technology of millimeter-wave antenna arrays are mainly studied in this dissertation.The specific contributions of the author are as follows:1.For the high polarization isolation requirement of IBFD,the combination of dual differential cancellation and orthogonal mode isolation principles is used to break through the difficult point of improving the polarization isolation of the reflective array in the W band.The research also covers topics such as the high efficiency resonant radiators,the feed pattern manipulation,and the feed-reflectarray co-design for amplitude and phase optimization.Compared to existing similar planar solutions with an isolation of 27 d B,the antenna array’s polarization isolation is increased to over 55 d B.2.For the wideband wide-angle circular polarization requirement of satellite communication,based on the natural 90-degree phase difference between electric current and magnetic current and the bidirectional decoupling mechanism of comb-like structure,the wideband wide-angle circular polarization challenge of Variable Inclination Continuous Transverse Stub(VICTS)-like antennas in the Ka band is overcome.The study also explores the mathematical derivation of the phase difference between waveguide currents and magnetic currents,and optimizes the feeding mechanisms of individual radiating elements to enhance bandwidth and scanning range.Compared to similar antennas with 3.3% circular polarization bandwidth and ±40° scanning range,the proposed antenna achieves a bandwidth and scanning range of 12% and ±60°,respectively.3.For the integration of dual-band shared-aperture antennas in VICTS antenna arrays for satellite communication,based on shared radiating elements and separate feeding networks,the challenge of balanced dual-band radiation and wide-angle scanning of VICTS antenna arrays is overcome.By leveraging the characteristics of short singlestage stubs with fewer resonant points,the bandwidth with stable radiation ratio is extended,allowing for dual-band radiation and scanning capabilities in K/Ka bands.The final design achieves 20 GHz and 30 GHz sharing the aperture with the non-integer frequency-ratio.The maximum scanning angle is 2×60°.4.For the integration of dual-band shared-aperture antennas in phased array antennas for satellite communication,based on a 1:1.5 array topology and the principle of dualband radiating element interchange,with the natural 90° phase difference between current and magnetic flow as the basis,the challenges of realizing wideband,wide-angle,circular polarization,and high isolation in shared-aperture phased array antennas are overcome.The 1:1.5 array topology provides larger positioning space for array elements and a more consistent radiation environment.The proposed design successfully meets the requirements of Ka-band satellite communication phased array antennas,achieving wide bandwidth,wide-angle scanning,circular polarization,and improved isolation simultaneously. |
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