In this paper, a co-planar waveguide fed circular slot antenna with an operational impedance bandwidth of 20-28 GHz is proposed. In order to reduce the effective occupied volume when the antenna is integrated onto a typical mmWave 5G smartphone, a conformal topology is investigated. Since the radiating aperture is not backed by an electrically large ground plane, it leads to a bidirectional beam resulting in an inherently low forward gain of 4 dBi with a front to back ratio of 1 dB. Hence, a compact exponentially tapered copper film reflector is integrated electrically close (0.046λ at 28 GHz) to the radiating aperture to achieve a forward gain of 8-9 dBi with an effective radiating volume of 0.24λ03. The impedance bandwidth is from 25 to 30 GHz (18.2%) with a 1-dB gain bandwidth of 34.7% indicating high pattern integrity across the band. Since the proposed antenna element offers wideband with high gain, it is a potential candidate for mmWave 5G smartphones.
2. Hong, W., K. Baek, Y. Lee, Y. Kim, and S. Ko, "Study and prototyping of practically large-scale mmWave antenna systems for 5G cellular devices," IEEE Communications Magazine, Vol. 52, No. 9, 63-69, September 2014.
3. Ta, S. X., H. Choo, and I. Park, "Broadband printed-dipole antenna and its arrays for 5G applications," IEEE Antennas and Wireless Propagation Letters, Vol. 16, 2183-2186, 2017.
4. Yang, B., Z. Yu, Y. Dong, J. Zhou, and W. Hong, "Compact tapered slot antenna array for 5G millimeter-wave massive MIMO systems," IEEE Transactions on Antennas and Propagation, Vol. 65, No. 12, 6721-6727, Dec. 2017.
5. Dadgarpour, A., B. Zarghooni, B. S. Virdee, and T. A. Denidni, "Improvement of gain and elevation tilt angle using metamaterial loading for millimeter-wave applications," IEEE Antennas and Wireless Propagation Letters, Vol. 15, 418-420, 2016.
6. Dadgarpour, A., B. Zarghooni, B. S. Virdee, and T. A. Denidni, "One- and two-dimensional beam-switching antenna for millimeter-wave MIMO applications," IEEE Transactions on Antennas and Propagation, Vol. 64, No. 2, 564-573, Feb. 2016.
7. Briqech, Z., A. Sebak, and T. A. Denidni, "Wide-scan MSC-AFTSA array-fed grooved spherical lens antenna for millimeter-wave MIMO applications," IEEE Transactions on Antennas and Propagation, Vol. 64, No. 7, 2971-2980, July 2016.
8. Sun, M., Z. N. Chen, and X. Qing, "Gain enhancement of 60-GHz antipodal tapered slot antenna using zero-index metamaterial," IEEE Transactions on Antennas and Propagation, Vol. 61, No. 4, 1741-1746, April 2013.
9. Wani, Z., M. P. Abegaonkar, and S. K. Koul, "Millimeter-wave antenna with wide-scan angle radiation characteristics for MIMO applications," Int. J RF Microw. Comput. Aided Eng., e21564, 2018.
10. Karthikeya, G. S., M. P. Abegaonkar, and S. K. Koul, "CPW fed conformal folded dipole with pattern diversity for 5G mobile terminals," Progress In Electromagnetics Research C, Vol. 87, 199-212, 2018.
11. Karthikeya, G. S., M. P. Abegaonkar, and S. K. Koul, "CPW fed wideband corner bent antenna for 5g mobile terminals," IEEE Access, Vol. 7, 10967-10975, 2019.
12. Jilani, S. F. and A. Alomainy, "Planar millimeter-wave antenna on low-cost flexible PET substrate for 5G applications ," 2016 10th European Conference on Antennas and Propagation (EuCAP), 1-3, Davos, 2016.
13. Sarabandi, K., J. Oh, L. Pierce, K. Shivakumar, and S. Lingaiah, "Lightweight, conformal antennas for robotic flapping flyers," IEEE Antennas and Propagation Magazine, Vol. 56, No. 6, 29-40, Dec. 2014.
14. Garg, R., "Microstrip Antenna Design Handbook," Artech House, 2001.