In this paper, a switchable beam and super-directive Electrically Small Antenna (ESA) dipole deployed at an IoT network gateway at 868 MHz is presented. It consists of one fed dipole and one loaded parasitic dipole. The nature and value of the load are obtained using the Uzkov equations, allowing determining current weighting coefficients in the case of two separately fed antennas, in order to maximize the gain and the directivity in a given direction. Reconfigurability in two directions is achieved using a pair of anti-parallel PIN diodes to steer the beam to the desired direction. The array final dimensions are 109 × 43 mm2 (0.3λ × 0.1λ) generating a high directivity of 6.8 dBi in simulation and 6.7 dBi in measurement at 868 MHz for each beam in the azimuth plane.
2. Harrington, R. F., "On the gain and beamwidth of directional antennas," IRE Transactions on Antennas and Propagation, 219-225, Jul. 1958.
3. Uzkov, I., "An approach to the problem of optimum directive antennae design," Comptes rendues (Do lady) de l’acad´emie des sciences de l’URSS, Vol. 53, No. 1, 35-38, 1946.
4. O’Donnell, T. H. and A. D. Yaghjian, "Electrically small superdirective arrays using parasitic element," IEEE Antennas and Propagation Society International Symposium, 3111-3114, Jul. 2006.
5. Boyle, K., "Radiation patterns and correlation of closely spaced linear antennas," IEEE Trans. Antennas Propag., Vol. 50, No. 8, 1162-1165, Aug. 2002. doi:10.1109/TAP.2002.801367
6. Pigeon, M., A. Sharaiha, and S. Collardey, "Miniature and superdirective two elements endfire antenna array," 8th European Conference on Antennas and Propagation (EuCAP 2014), Apr. 6-11， 2014.
7. Haskou, A. and A. Sharaiha, "Integrating superdirective electrically small antenna arrays in PCBs," IEEE Antennas and Wireless Propagation Letters, Jan. 2015.
8. Haskou, A., A. Sharaiha, and S. Collardey, "Design of small parasitic loaded superdirective end-fire antenna arrays," IEEE Trans. Antennas Propag., Vol. 63, No. 12, 5456-5464, Dec. 2015. doi:10.1109/TAP.2015.2496112
9. Harrington, R. F., "A Reactively controlled directive arrays," IEEE Trans. Antennas Propag., Vol. 26, No. 3, 390-395, May 1978. doi:10.1109/TAP.1978.1141852
10. Milne, R., "A small adaptive array antenna for mobile communications," Antennas and Propagation Society International Symposium, Vol. 23, 797-800, 1985.
11. Zhang, T., S. Y. Yao, and Y. Wang, "Design of radiation-pattern-reconfigurable antenna with four beams," IEEE Antennas Wireless Propag. Lett., Vol. 14, 183-186, 2015. doi:10.1109/LAWP.2014.2360098
12. Dihissou, A., A. Diallo, P. Le Thuc, and R. Staraj, "Directive and reconfigurable loaded antenna array for wireless sensor networks," Progress In Electromagnetics Research C, Vol. 84, 103-117, 2018. doi:10.2528/PIERC18032403
13. Jacob, M. M., et al., "Broadband non-Foster matching of an electrically small loop antenna," IEEE Antennas and Propagation Society International Symposium (APSURSI), 2012.