IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 64, NO. 7, JULY 2016 2971 Wide-Scan MSC-AFTSA Array-Fed Grooved Spherical Lens Antenna for Millimeter-Wave MIMO Applications Zouhair Briqech, Member, IEEE, Abdel-Razik Sebak, Fellow, IEEE , and Tayeb A. Denidni, Senior Member, IEEE Abstract—A new three-element multi-sin-shape corrugated antipodal Fermi tapered slot antenna (MSC-AFTSA) array integrated with a grooved spherical (GS) lens operating at 57–64 GHz is introduced. Multicorrugated patterns are imple- mented to obtain better matching performance when the antenna feeds the GS lens with broadband coverage. An implemented design for grooving the lens profile presents a new principle to obtain an optimum focal point feed using the tapered slot antennas. This technique gives more freedom to enhance the E- and H -plane characteristics with a gain of 20 dB, radiation efficiency of 83% at 60 GHz, and wide angle multibeam coverage. It is a relatively small spherical-lens antenna with three feeds of MSC-AFTSA array, 44.2 × 51.6 × 25.4 mm 3 in size. There is a good agreement between calculated and measured results. The proposed antenna prototype with its wide-scan per- formance is suitable for broadband multiple-input–multiple- output communication systems operating at millimeter-wave bands. Index Terms— 60 GHz, fifth-generation (5G) communication, lens antennas, millimeter wave (MMW), multiple-input–multiple- output (MIMO) antennas, tapered slot antennas (TSAs), wideband antenna feeds. I. I NTRODUCTION A 60-GHz frequency range has become a reasonable band for high data rate services, which are seeing increasing demand nowadays for short range multiple-input–multiple- output (MIMO) communications for fifth-generation (5G) applications [1], [2]. To overcome high propagation loss encountered within the 60-GHz band, an antenna with high gain, stable radiation characteristics, and an ability to cover a full unlicensed worldwide bandwidth of 5–7 GHz is required. These features are satisfied by utilizing the printed tapered slot antennas (TSAs) [3]–[6], which provide a wide band- width, high gain end-fire characteristics, and high radiation efficiency, and are easy to fabricate. The planar design of TSAs Manuscript received November 10, 2015; revised March 17, 2016; accepted April 25, 2016. Date of publication May 10, 2016; date of current version July 5, 2016. Z. Briqech and A.-R. Sebak are with the Department of Electrical and Computer Engineering, Concordia University, Montréal, QC H3G 2W1, Canada (e-mail: z_briqec@encs.concordia.ca; abdo@ece.concordia.ca). T. A. Denidni is with the Institut National De La Recherche Scientifique, Montréal, QC H5A 1C6, Canada (e-mail: denidni@emt.inrs.ca). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TAP.2016.2565704 makes them easier to employ in low-profile beam-steerable directional antennas for indoor applications and base stations, and/or as portable devices. The choice of a 60-GHz broadband for MIMO applica- tions has been reported in [7]–[11]. The indoor 60-GHz applications presented in [7] have introduced a hybrid sys- tem of downlink beamforming with phased antenna arrays using a division of multiple access channels to support a multiuser MIMO system. In [9], a wireless data speed of up to 51 Gb/s at 60 GHz has been achieved, per- formed with a 2 × 2 spatially multiplexed MIMO with an orthogonal frequency division multiplexing system. A suc- cessful characterization of underground mine conducted at a 60-GHz band with MIMO radio channels has used a 2 × 2 planar microstrip antenna array demonstrated in [10]. Rappaport and his team [1] have presented intensive outdoor measurement scenarios to demonstrate operations within several millimeter-wave (MMW) bands, including 60 GHz, for MIMO 5G applications. A 60-GHz single- polarized horn antenna and 2 × 2 dual-polarized array front ends have been employed in [11] for short-range MIMO communications. Despite good performance of the antenna elements reported in [8], [10], and [11], a large array design with relatively low gain per single antenna element and a complex array structure increase the overall system losses. The selection of an efficient antenna that can deliver a high gain and high radiation efficiency is essential in order to increase the MIMO system performance. In addition, wide angle scanning antennas are desired for several MMW applications, such as automobile radars [12], broadband MIMO communications [11], and imaging sys- tems [13]. Dielectric lens antennas have been employed for a wide scan with TSA, reported in [12], [14], and [15]. As experimentally conducted in [9], spatial arrangements with angled antennas can increase the system robustness, espe- cially when employed with spatial multiplexing MIMO for 60-GHz wireless systems, which effectively increases the sys- tem capacity. Schoenlinner et al. [12] introduced a wide-scan system using a 33-beam array of TSA-fed spherical Teflon lenses for automotive radars operating at 77 GHz. A planar lin- ear TSA-fed 2-D cylindrical Luneberg lens antenna based on a partially filled parallel plate technique conducted at 30 GHz 0018-926X © 2016 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.