array has low RCS within the operation band. Over 5 dB RCS reduction can be obtained with respect to the array without MS for x- and y-polarized incident waves. Experi- mental results are in good agreement with simulated ones. Thus, the proposed array offers solutions for satellite com- munication and stealth platform owing to its wideband, low RCS, and low-profile properties. ORCID Qi Zheng http://orcid.org/0000-0002-7748-8994 REFERENCES [1] Zheludev NI, Kivshar YS. From metamaterials to metadevices. Nat Mater. 2012;11(11):917–924. [2] Sun W, He Q, Hao J, Zhou L. A transparent metamaterial to manipulate electromagnetic wave polarizations. Opt Lett. 2011; 36(6):927–929. [3] Liu Y, Li K, Jia Y, Hao Y, Gong S, Guo YJ. Wideband RCS reduction of a slot array antenna using polarization conversion metasurfaces. IEEE Trans Antennas Propag. 2016;64(1):326–331. [4] Zhang L, Dong T. Low RCS and high-gain CP microstrip antenna using SA-MS. Electron Lett. 2017;53(6):375–376. [5] Li K, Liu Y, Jia Y, Guo YJ. A circularly polarized high-gain antenna with low RCS over a wideband using chessboard polar- ization conversion metasurfaces. IEEE Trans Antennas Propag. 2017;65(8):4289. [6] Orr R, Goussetis G, Fusco V. Design method for circularly polarized Fabry–Perot cavity antennas. IEEE Trans Antennas Propag. 2014;62(1):19–26. [7] Montalv~ ao ES, Montalv~ ao AC, Campos AL, Neto AG. A new model of metasurface used for linear-to-circular polarization con- version in antenna array. Microwave Opt Technol Lett. 2016;58 (4):861–864. [8] Zhu HL, Cheung SW, Liu XH, Yuk TI. Design of polarization reconfigurable antenna using metasurface. IEEE Trans Antennas Propag. 2014;62(6):2891–2898. [9] Huang Y, Yang L, Li J, Wang Y, Wen G. Polarization conversion of metasurface for the application of wide band low-profile circular polarization slot antenna. Appl Phys. Lett. 2016;109(5):054101. [10] Liu W, Chen ZN, Qing X. Metamaterial-based low-profile broadband aperture-coupled grid-slotted patch antenna. IEEE Trans Antennas Propag. 2015;63(7):3325–3329. [11] Huang J. A technique for an array to generate circular polariza- tion with linearly polarized elements. IEEE Trans Antennas Propag. 1986;34(9):1113–1124. [12] Evans H, Gale P, Aljibouri B, Lim EG, Korolkeiwicz E, Sam- bell A. Application of simulated annealing to design of serial feed sequentially rotated 2 3 2 antenna array. Electron Lett. 2000;36(24):1987–1988. [13] Pang KK, Lo HY, Leung KW, Luk KM, Yung EKN. Circularly polarized dielectric resonator antenna subarrays. Microwave Opt Technol Lett. 2000;27(6):377–379. [14] Chen A, Zhang Y, Chen Z, Cao S. A Ka -band high-gain circu- larly polarized microstrip antenna array. IEEE Antennas Wireless Propag Lett. 2010;9:1115–1118. How to cite this article: Zheng Q, Guo C, Ding J. Wideband and low RCS planar circularly polarized array based on polarization conversion of metasurface. Microw Opt Technol Lett. 2018;60:784–789. https:// doi.org/10.1002/mop.31050 Received: 10 August 2017 DOI: 10.1002/mop.31045 Broadband tapered planar monopole antenna with parasitic elements for multiple wireless operations C. Karakus 1 | C. Dogusgen (Erbas) 2 | S. C. Yurt 3 | S. Kent 4 1 CKK EM Sensors, Istanbul, Turkey 2 Electrical and Electronics Engineering Department, Istanbul Yeni Yuzyil University, Istanbul, Turkey 3 Electrical and Computer Engineering Department, University of New Mexico, NM, USA 4 Electronics and Communication Engineering Department, Istanbul Technical University, Istanbul, Turkey Correspondence C. Dogusgen (Erbas), Electrical and Electronics Engineering Department, Istanbul Yeni Yuzyil University, Istanbul, Turkey. Email: cihan.dogusgen@yeniyuzyil.edu.tr Abstract We designed a planar monopole antenna with an imped- ance matching part and two rectangular parasitic elements. Parasitic elements significantly increased radiation band- width and gain. Measured fractional bandwidth and maximum gain for the case with parasitic elements were 129.9% and 5.67 dB, respectively. Antenna operated between 675 MHz and 3177.5 MHz. KEYWORDS bandwidth enhancement, electromagnetic coupling, gain enhancement, parasitic element, planar antenna KARAKUS ET AL. | 789