IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 63, NO. 4, APRIL 2015 1881 REFERENCES Sidelobe Canceling for Reconfigurable Holographic [1] J. Huang and J. A. Encinar, Reflectarray Antennas. Hoboken, NJ, USA: Metamaterial Antenna Wiley/IEEE Press, Nov. 2007, ISBN: 978-0-470-08491-5. [2] J. A. Encinar et al., “Dual-polarization dual-coverage reflectarray for Mikala C. Johnson, Steven L. Brunton, Nathan B. Kundtz, space applications,” IEEE Trans. Antennas Propag., vol. 54, no. 10. and J. Nathan Kutz pp. 2827–2836, Oct. 2006. [3] T. Toyoda, D. Higashi, H. Deguchi, and M. Tsuji, “Broadband reflectarray with convex strip elements for dual-polarization use,” in Proc. Int. Symp. Abstract—Accurate and efficient methods for beam-steering of holo- Electromagn. Theory (EMTS’13), Hiroshima, Japan, May 20–24, 2013, graphic metamaterial antennas is of critical importance for enabling pp. 683–686. consumer usage of satellite data capacities. We develop an algorithm capa- [4] R. E. Hodges and M. Zawadzki, “Design of a large dual polarized Ku ble of optimizing the beam pattern of the holographic antenna through band reflectarray for space borne radar altimeter,” in Proc. IEEE Antennas software, reconfigurable controls. Our method provides an effective tech- Propag. Soc. Int. Symp., Monterey, CA, USA, 2004, vol. 4, pp. 4356– nique for antenna pattern optimization for a holographic antenna, which 4359. significantly suppresses sidelobes. The efficacy of the algorithm is demon- [5] A. E. Martynyuk and J. I. Martinez Lopez, “Reflective antenna arrays strated both on a computational model of the antenna and experimentally. based on shorted ring slots,” in Proc. IEEE Microw. Symp. Dig., Phoenix, Due to their exceptional portability, low-power consumption, and lack AZ, USA, May 2001, vol. 2, pp. 1379–1382. of moving parts, holographic antennas are an attractive and viable tech- [6] A. Yu, F. Yang, A. Z. Elsherbeni, and J. Huang, “An X-band circularly nology when combined with proven software-based strategies to optimize polarized reflectarray using split square ring elements and the modified performance. element rotation technique,” in Proc. IEEE Antennas Propag. Soc. Int. Symp., San Diego, CA, USA, Jul. 2008, pp. 1–4. Index Terms—Holography, satellite antennas, sidelobe canceling. [7] S. Malfajani and Z. Atlasbaf, “Design and implementation of a broadband single layer circularly polarized reflectarray antenna,” IEEE Antennas Wireless Propag. Lett., vol. 11, pp. 973–976, Aug. 2012. I. INTRODUCTION [8] B. Strassner, C. Han, and K. Chang, “Circularly polarized reflectarray The reconfigurable holographic metamaterial surface antenna with microstrip ring elements having variable rotation angles,” IEEE Trans. Antennas Propag., vol. 52, no. 4, pp. 1122–1125, Apr. 2004. (MSA) is an emerging technology for satellite communications. [9] C. Han, C. Rodenbeck, J. Huang, and K. Chang, “A C/Ka dual frequency The MSA is a low-power device that is flat, thin, and lightweight. dual layer circularly polarized reflectarray antenna with microstrip ring Moreover, it achieves active electronic scanning without any mechan- elements,” IEEE Trans. Antennas Propag., vol. 52, no. 11, pp. 2871– ical moving parts. However, in order to operate across its entire 2876, Nov. 2004. [10] J. Huang, C. Han, and K. Chang, “A Cassegrain offset-fed dual- dynamic-scanning range, the antenna must be able to scan reliably band reflectarray,” in Proc. IEEE Antennas Propag. Soc. Int. Symp., without unacceptable levels of far-field radiation in undesired direc- Albuquerque, NM, USA, Jul. 2006, pp. 2439–2442. tions (sidelobes). It is therefore mandatory to suppress the production [11] A. Yu, F. Yang, A. Z. Elsherbeni, and J. Huang, “Experimental demonstra- of sidelobes in a robust fashion while still preserving a strong main tion of a single layer tri-band circularly polarized reflectarray,” in Proc. beam. We develop an optimization algorithm for the far-field pattern IEEE Antennas Propag. Soc. Int. Symp., Toronto, Canada, Jul. 11–17, 2010, pp. 1–4. of an MSA that addresses these issues. Specifically, we demonstrate [12] C. Guclu, J. Perruisseau-Carrier, and O. A. Civi, “Proof of concept of a an algorithm for sidelobe suppression in software without resorting to dual-band circularly-polarized RF MEMS beam-switching reflectarray,” nonadaptive hardware modifications. IEEE Trans. Antennas Propag., vol. 60, no. 11, pp. 5451–5455, Nov. Hardware developments for MSAs have recently undergone major 2012. innovations [1]–[3]. These works demonstrate the viability of building [13] J. Huang and R. J. Pogorzelski, “A Ka-band microstrip reflectarray with elements having variable rotation angles,” IEEE Trans. Antennas Propag., a metamaterial Ka-band antenna using existing materials and pro- vol. 46, no. 5, pp. 650–656, May 1998. cesses. However, the hardware antenna is only part of the system [14] S. Mener, R. Gillard, R. Sauleau, A. Bellion, and P. Potier, “Unit-cell for needed as the antenna also must have software control algorithms to dual-circular polarisation reflectarrays,” in Proc. 8th Eur. Conf. Antennas achieve optimal beam performance, being able to tailor, in a rapid Propag., The Hague, The Netherlands, Apr. 6–11, 2014, pp. 1615–1618. [15] E. Girard, R. Moulinet, R. Gillard, and H. Legay, “An FDTD optimization and robust fashion, the radiation pattern of the antenna to achieve of a circularly polarized reflectarray unit-cell,” in Proc. IEEE Antennas the desired characteristics that include a high peak gain, acceptable Propag. Soc. Int. Symp., San Antonio, TX, USA, Jun. 2002, vol. 3, beamwidth, and sidelobe suppression. pp. 136–139. In this paper, we address the problem of sidelobe suppression for [16] S. Mener, R. Gillard, R. Sauleau, C. Cheymol, and P. Potier, “Design a holographic antenna. Section II covers the background for classi- and characterization of a CPSS-based unit-cell for circularly-polarized reflectarray applications,” IEEE Trans. Antennas Propag., vol. 61, no. 4, cal antenna sidelobe cancelation and holographic antennas. Section III pp. 2313–2318, Apr. 2013. describes the antenna system and computational model used to pre- [17] R. Pereira, R. Gillard, R. Sauleau, T. Dousset, and X. Delestre, “Dual dict the behavior of the antenna investigated in this work. Section IV linearly-polarized unit-cells with nearly 2-bit resolution for reflectarray presents the algorithm developed for sidelobe reduction. Finally, in applications in X-band,” IEEE Trans. Antennas Propag., vol. 60, no. 12, Section V, results demonstrating the efficacy of the algorithm on both pp. 6042–6048, Dec. 2012. [18] S. Mener, R. Gillard, R. Sauleau, C. Cheymol, and P. Potier, “An the computational model and on experimental hardware are exhibited. improved topology for reconfigurable CPSS-based reflectarray cell,” in Proc. Eur. Conf. Antennas Propag. (EuCAP), Gothenburg, Sweden, Apr. Manuscript received June 05, 2014; revised January 07, 2015; accepted 8–12, 2013, pp. 2721–2725. January 26, 2015. Date of publication February 04, 2015; date of current version April 03, 2015. M. C. Johnson is with the Department of Applied Mathematics, University of Washington, Seattle, WA 98195 USA, and also with Kymeta Corporation, Redmond, WA 98052 USA (e-mail: [email protected]). S. L. Brunton and J. N. Kutz are with the Department of Applied Mathematics, University of Washington, Seattle, WA 98195 USA (e-mail: [email protected]). N. B. Kundtz is with Kymeta Corporation, Redmond, WA 98052 USA. Digital Object Identifier 10.1109/TAP.2015.2399937 0018-926X © 2015 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. 1882 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 63, NO. 4, APRIL 2015 We then conclude the paper with discussion of the possibilities that our a rectangular waveguide beneath the elements [see Fig. 1(a)]. This proposed control strategy provides. structure leads to several characteristics that must be considered when approaching optimization of the radiation pattern. II. BACKGROUND First, a metamaterial antenna capable of closing a link with a satel- lite must have enough surface area to attain high enough gain. To A. Sidelobe Cancelation in Arrays achieve this basic performance requirement, the antenna is of the Sidelobe cancelation has a rich history in the academic literature as approximate dimensions shown in Fig. 1(a), and thus is composed of well as in practice. Several patents were issued for device configura- more than 10 000 continuously and individually controlled unit cells. tions for sidelobe cancelation in the mid-1960 s [4]–[7]. Additionally, The control of each cell varies the amplitude of scatter of the cell from there are many previous works in sidelobe cancelation of digital a minimally excited state to a maximally excited state as the voltage beamforming networks [8]–[10]. tunes the resonant frequency of the cell. It is impractical and infeasi- However, unlike the operating principles of the metamaterial ble to try random controls, e.g., a genetic algorithm, in search of good antenna, these early works dictate the use of spatially separate arrays control patterns. and assume that the signal from each antenna comprising the array is Apart from the large number of cells, each meta-atom resonant cell separable, i.e., each element of the beamformer has its own transceiver responds nonlinearly in both phase and amplitude to its control. The chain consisting of amplifier, filter, mixer, etc. During the processing of cells do not display independent amplitude and phase modulation as the signal from each individual receiver, the interference signal is sub- a phased array would, but instead the amplitude and phase shift occur tracted from the reference, and thus the unwanted information received simultaneously as the control is changed. This resonant behavior is from sidelobes is suppressed, an approach due to Widrow [11]. sensitive to manufacturing tolerances. The holographic antenna, on the other hand, is engineered to treat The coupling between the elements and the coupling between all the the pattern and the control of the antenna in aggregate.