-
一直以来,宽波束天线单元都具有很广泛的应用价值,其中包括比较典型的如:卫通天线[1-2],需要较宽的波束宽度同时与多颗卫星进行通信;宽角扫描相控阵天线[3-4],为减小宽角扫描时的增益下降,需要设计具有较宽波束宽度的天线单元等。
近年来,国内外对如何展宽天线单元波束宽度的研究逐渐增多,文献[5]设计了宽波束的Vivaldi天线,并应用于相控阵宽角扫描中;文献[6-7]利用电磁偶极子天线设计了宽波束的天线单元,并利用反射板进一步展宽波束宽度。同时也有一些研究采用可重构技术,使用分时波束工作的方式,等效展宽了天线单元的波束宽度[8-10]。当天线单元组阵时,阵列中天线单元的有源方向图会由于互耦的影响而发生改变[11-13],所以在实际设计中,需要考虑天线单元的互耦环境,由此引申出了一系列的宽角阻抗匹配技术[14-17]。另外,从根本上减小天线之间的互耦[18-19]也是一种可行的思路。
综上,从实用性出发,本文选择了直接设计具有低互耦特性的宽波束天线单元,并进行阵列组阵研究,设计具有宽角扫描特性的相控阵列。
-
在设计工程实用的天线单元时,必须考虑阵列环境对天线单元的影响,故在本文的设计中,使用一个8元线阵加以说明,天线单元的设计将在此8元线阵中进行调整和优化。
其阵列环境仿真模型如图3所示。本文中天线工作的中心频点设计为2.9 GHz,考虑到布阵和栅瓣抑制条件,选择布阵间距为50 mm,约为中心频率的半个波长。
天线各个设计参数在如图3的阵列环境中进行优化,得到如表1所示的参数数据,折叠地板高出最上方贴片4 mm。天线单元整体尺寸为50 mm×70 mm×14 mm。
表 1 天线各设计参数最终取值
mm Ws1 Ws2 Wg1 Ls1 Lp 70 40 60 50 28 Lf h h1 hp1 hp2 10 14 10 2 1 为说明各个主要参数对天线方向图、驻波及互耦等的影响,本文还进行了部分重要参数的对比仿真研究。图4为4号天线单元在有无上层贴片情况下的S参数曲线对比,从图中可明显看出,在谐振频点上,有上层贴片的天线结构其隔离度有8 dB的改善,这和天线本身结构带来的S11改变有一定的关系,但提升隔离度的效果还是较为明显。
图5为4号天线单元,在有无折叠地板时对S参数的影响对比。从图中可以明显看出,没有折叠地板的天线隔离度远比带有折叠地板的天线单元差,其中还需去除隔离度的影响,证明折叠地板对天线单元之间的耦合有极大影响。
图6为不同折叠地板高度参数h,对4号阵元S参数的影响对比,h变化从13 mm到17 mm,天线隔离度最高和最低有5 dB的差距,隔离度最优的结果出现在h=14 mm的位置。可见,通过合理调节h参数可改善天线的隔离度。
需要值得注意的是,调整h参数时需要同时考虑对方向图波束宽度的影响。图7为不同折叠地板高度对天线单元辐射方向图的影响,可见不同高度对辐射方向图的影响很大,且趋势并非单调趋势,在h=14 mm时其波束最宽。
图8为该天线单元(1, 2, 3, 4)在阵列环境下的有源方向图对比,从中可看出由于低互耦的效果,其波束保持基本一致,且宽度极宽,大于140°。
Design of a Low Mutual Coupling\Wide Beam Microstrip Antenna
-
摘要: 该文主要描述了一种适合宽角扫描的相控阵天线单元设计思路,研究了其组阵实现宽角扫描的特性。为尽量减少大角度扫描过程中由于天线单元波束宽度有限带来的阵列增益下降,采用折叠地板的方式展宽天线单元半功率波束宽度;同时,为了降低互耦引起的天线单元方向图畸变,在宽波束设计基础上探索了降低天线互耦的方法,使得真实阵列方向图尽可能地满足方向图乘积定理,从而实现宽角、高增益扫描的目的。经一维线阵的仿真和测试,设计了一种能扫描到±70°且增益变化不大的宽角扫描阵列。设计的天线还能作为一种典型的天线单元,应用于5G等民用消费电子场景。Abstract: This paper introduces a novel idea for designing a phase array microstrip antenna element with low coupling and wide beam scan capabilities. Consisted of two-layers patches separated by an air gap and fold grounds, the proposed antenna element has a simple structure. In order to minimize the array gain drop due to the limited antenna beam width, the proposed antenna is designed to expand the half-power beam width as far as possible with fold grounds structure. At the same time, in order to reduce the distortion of antenna element pattern caused by mutual coupling, some methods are proposed for reducing the mutual coupling to make sure satisfy the product theorem of antenna pattern as much as possible. Moreover, a prototype of the proposed antenna and a linear array are fabricated and measured. The measured results show that the wide angle scanning array is capable of scanning up to ± 70° along with stable gain characteristics. Meanwhile, the proposed antenna is a classical antenna which can be used for 5G applications ranging from infotainment solutions to consumer devices.
-
Key words:
- hign gain /
- hign isolation /
- phased antenna array /
- wide angle scanning
-
表 1 天线各设计参数最终取值
mm Ws1 Ws2 Wg1 Ls1 Lp 70 40 60 50 28 Lf h h1 hp1 hp2 10 14 10 2 1 -
[1] MASHHADI S H H, JIAO Y C, CHEN J. Broadbeam cylindrical dielectric resonator antenna[J]. IEEE Access, 2019, 7(1): 112653-112661. [2] MENG Q, YANG W, CHE W, et al. Novel wideband low-profile dual-circularly polarized metasurface antenna[C]//2018 International Workshop on Antenna Technology (iWAT). Nanjing: [s.n.], 2018: 1-3. [3] XIAO D, WANG Bing-zhong, HE Guo-qiang. Research on a millimeter-wave phased array with wide-angle scanning performance[J]. IEEE Transactions on Antennas & Propagation, 2013, 61(10): 5319-5324. [4] MAILLOUX R J. Phased array antenna handbook[M]. 2nd ed. London: England Artech House, 2005. [5] 王茂泽. 二维宽带宽角扫描相控阵天线研究[D]. 西安: 西安电子科技大学, 2014. WANG Mao-ze. Design of the antenna array of two dimension broadband and wide angle phased array antenna[D]. Xi’an: Xidian University, 2014. [6] WEN Ya-qing, WANG Bing-zhong, XIAO Ding. Wide-beam SIW-Slot antenna for wide-angle scanning phased array[J]. IEEE Antennas and Wireless Propagation Letters, 2016, 15(2): 1638-1641. [7] GUO Jia-jia, XIAO Shao-qiu, LIAO Shao-wei, et al. Dual band and low profile differentially-fed slot antenna for wide-angle scanning phased array[J]. IEEE Antennas & Wireless Propagation Letters, 2017, 17(2): 259-262. [8] OUYANG Jun, YANG Feng, YANG Shi-wen, et al. A novel e-shape radiation pattern reconfigurable microstrip antenna for broadband, wide-beam, high-gain applications[J]. Microwave and Optical Technology Letters, 2008, 50(8): 2052-2054. doi: 10.1002/mop.23554 [9] SELVAM Y P, KANAGASABAI M, MOHAMMED G N, et al. A low profile frequency and pattern reconfigurable antenna[J]. IEEE Antennas and Wireless Propagation Letters, 2017, 16(1): 3047-3050. [10] MEHTA A, MIRSHEKAR-SYAHKAl D. Pattern steerable square loop antenna[J]. Electronics Letters, 2007, 43(9): 491-493. doi: 10.1049/el:20070662 [11] JEDLICKA R P, POE M, CARVER K. Measured mutual coupling between microstrip antennas[J]. IEEE Transactions on Antennas & Propagation, 1981, 29(1): 147-149. [12] SVANTESSON T, RANHEIM A. Mutual coupling effects on the capacity of multielement antenna systems[C]// IEEE International Conference on Acoustics. [S.l.]: IEEE, 2001: 2485-2488. [13] GUPTA I J, KSIENSKI A A. Effects of mutual coupling on the performance of adaptive arrays[J]. IEEE Transactions on Antennas & Propagation, 2006, 31(5): 785-791. [14] 郑学誉, 万长宁. 宽带宽角扫描相控阵天线[J]. 电波科学学报, 1995, 10(1, 2): 33-38. ZHENG Xue-yu, WANG Chang-ning. Scanning phased array antenna with broadand and wide angle[J]. Chinese Journal of Radio Science, 1995, 10(1, 2): 33-38. [15] 罗耀辉, 李正军. 宽角扫描相控阵天线有源阻抗的计算[J]. 空间电子技术, 2009, 6(4): 84-87. LUO Yao-hui, LI Zheng-jun. Active impendence simulation of wide-angle scanning phased array antenna[J]. Space Electronic Technology, 2009, 6(4): 84-87. [16] 鲁加国. 适于一维相控阵宽角扫描的非对称单脊波导裂缝线源[J]. 现代电子, 2011, 23(4): 1-5. LU Jia-guo. Asymmetric ridge waveguide slot linear array for one dimension wide angle scan phased array[J]. Modern Electronics, 2011, 23(4): 1-5. [17] 郑秋容. 微波光子晶体带隙特性及其在天线中的应用[D]. 合肥: 国防科学技术大学, 2007. ZHENG Qiu-rong. Band gap characteristics of microwave photonic crystals and their applications in antennas[D]. He fei: National University of Defense Technology, 2007. [18] ZHOU Z, WEI Z, TANG Z, et al. Design and analysis of a wideband multiple-microstrip dipole antenna with high isolation[J]. IEEE Antennas and Wireless Propagation Letters, 2019, 18(4): 722-726. doi: 10.1109/LAWP.2019.2901838 [19] SAURABH A K, RATHORE P S, MESHRAM M K. Compact wideband four-element MIMO antenna with high isolation[J]. Electronics Letters, 2020, 56(3): 117-119. doi: 10.1049/el.2019.2871