| Phased array antennas are widely used in various military and civil applications.The common goals of these applications are miniaturization,multifunction,low cost,high accuracy,and high communication capacity.As a result,higher standards are set for the antenna array used in phased array antenna systems,including wide operating bandwidth,low profile,low cost,high-performance aperiodic array design,and multifrequency multipolarized shared-aperture antenna technology,integrated with multiple functions.Based on the application requirements of phased array antenna,this dissertation focuses on the difficulties of low-profile millimeter-wave aperiodic phased array antenna and shared-aperture phased array antennas.The details are as follows:1.To address the contradiction between high sparsity and low sidelobe,as well as high aperture efficiency,an ultrahigh sparsity low-profile phased array antenna operating in W-band is proposed.Substrate-integrated waveguide(SIW)high-gain high-order mode antenna,based on TLY-5 material with low loss in the W-band,is used as the antenna array element.This antenna has the following features: wide bandwidth,high gain,low cross-polarization level,weak coupling between elements,low profile,and high efficiency.The optimization method,based on genetic algorithms,is also improved for array design by combining the structure and radiation performance of the antenna elements.Approximately 4% of the full array of half-wavelength antennas is used,thereby reducing the system cost.The test results show that the antenna gain is greater than 35.3 d B,the aperture efficiency is greater than 20.3%,the normal sidelobe is lower than-18 d B,the sidelobe is lower than-13.5 d B,and the scan drop is lower than 2 d B in the ± 15° scan range.The experiment shows the effectiveness of this design and provides a feasible scheme for designing an aperiodic phased array antenna with a super sparse rate that would significantly reduce the system cost.2.To solve the difficulties of sparse and shared-aperture phased array antennas,a dual-band dual-polarized sparse common-aperture phased array antenna operating in the Ku/Ka frequency band is proposed.To match the antenna heights of different frequency bands in the common aperture,high-and low-frequency antennas are used at different radiation structures and principles starting from the dual-band dual-polarized sharedaperture unit design.The high-frequency antenna is used as the parasitic structure of the low-frequency antenna to broaden the bandwidth and improve the benefits of the lowfrequency antenna.In addition,the low-frequency antenna structure is integrated and optimized as the radiation environment of the high-frequency antenna.The influence of low-frequency antennas on high-frequency antennas in the array antenna is considered in advance.The final shared-aperture antenna unit consists of a broadband Ku dualpolarized unit and four symmetrical broadband Ka antenna units.The antenna size is only0.425 λ(λ is the free space wavelength of the lowest operating frequency of Ku)and the height is 0.11 λ.The proposed antenna element is used to design a sparse array with Ku full arrays and Ka filling rates of 25%.The antenna distribution is optimized using the genetic algorithm.The selected Ka array elements are excited,while the remaining Ka antennas are retained as Ka virtual array elements and Ku antenna parasitic structures.The experiment shows that the impedance bandwidth of the Ku antenna is greater than18.7% with a beam scanning range of ± 60° off-axis angle,the scanning drop is better than 4.5 d B,and the impedance bandwidth of the Ka antenna is greater than 28.7% with a beam scanning range of ± 60° off-axis angle,and the scanning drop is better than 6.2d B.3.To solve the difficulties in the design of high isolation shared-aperture phased array antennas,a K/Ka-band dual-circular-polarization shared-aperture phased array antenna is proposed.A microstrip patch antenna,which is fed by a probe in the center,is used for the antenna array element.A “U” shaped gap with unequal lengths of two arms is used to adjust the feed point position to the center of the patch to realize circular-polarization radiations.The parasitic patch and slot above the ‘U’ patch,as well as the grounded metal column,form the filter structure,allowing a miniaturized circular-polarized array element with filter function to be realized.The K/Ka-band is nested together and arranged in a regular rectangular pattern with a 45° rotation between them.To further improve the axial ratio characteristics of the array,each of the four adjacent antenna elements of the same frequency rotates on its axis according to the rules of 0°,90°,180°,and 270°.The experimental results show that the antenna has a two-dimensional ± 60° beam scanning capability,the axis ratio is better than 6.2 d B during scanning,and the isolation between the receiving and transmitting antennas is greater than 25 d B.This concept can also be applied to linearly-polarized shared-aperture phased array antennas.The experiment shows the effectiveness of this design and provides a feasible scheme for the design of a dual-band dual-circular-polarization transceiver integrated with a common-aperture phased array antenna for satellite communication. |
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