In this paper, a new frequency tunable filtering-antenna (so-called filtenna) is inspired by a Defected Ground Structure (DGS) band-pass filter for the fifth generation picocell base stations. It is intended for use in Cognitive Radio (CR) communications within the European Union Sub-6 GHz spectrum, which ranges between 3.4 and 3.8 GHz. Firstly, a Wideband (WB) monopole antenna is proposed where the operational frequencies cover 3.15-4.19 GHz, taking the 10-dB return loss level as a threshold. A band-pass filter of a Semi-Square Semi-Circle shape is integrated into the WB antenna ground to obtain the communicating filtenna. The narrowband frequency tunability is achieved by changing two varactor diode capacitances located on the filter slots. The antenna is prototyped occupying a total space of 60 x 80 x 0.77 mm3, then tested to verify the simulated results. Three operating frequencies 3.4, 3.6 and 3.8 GHz of the filtenna are studied in terms of return loss, realized gain and radiation patterns which verify that the frequency shift has almost no effect on the antenna performance. The filtenna has a maximum gain of 4.5 dBi in measurements and 3.47 dBi in simulations. The obtained results have proved their efficiency for CR communications.
2. Vodafone and Samsung strategic partnership to launch Smart Home services, https://www.vodafone.com/news-and-media/vodafone-group-releases/news/vodafone-and-samsung-strategic-partership, January 7, 2022.
3. Global update on spectrum for 4G and 5G, https://www.qualcomm.com/media/documents/files/spectrum-for-4g-and-5g.pdf, December 2020.
4. Dudzinsky, Jr., S. J. Atmospheric effect on terrestrial millimeter-wave communication, https://www.rand.org., March 1974.
5. Kusaladharma, S. and C. Tellambura, "An overview of cognitive radio networks," Wiley Encycl. Electr. Electron. Eng., August 2017.
6. Kingsly, S., D. Thangarasu, M. Kanagasabai, M. Gulam Nabi Alsath, R. R. Thipparaju, S. K. Palaniswamy, and P. Sambandam, "Multiband reconfigurable filtering monopole antenna for cognitive radio applications," IEEE Antennas Wirel. Propag. Lett., Vol. 17, No. 8, 1416-1420, 2018.
7. Tang, M. C., Z. Wen, H. Wang, M. Li, and R. W. Ziolkowski, "Compact, Frequency-reconfigurable filtenna with sharply defined wideband and continuously tunable narrowband states," IEEE Trans. Antennas Propag., Vol. 65, No. 10, 5026-5034, 2017.
8. Mishra, S. R. and S. Kochuthundil Lalitha, "Filtennas for wireless application: A review," Int. J. RF Microw. Comput. Aided Eng., Vol. 29, No. 10, 1-28, 2019.
9. Nella, A. and A. S. Gandhi, "A five-port integrated UWB and narrowband antennas system design for CR applications," IEEE Trans. Antennas Propag., Vol. 66, No. 4, 1669-1676, 2018.
10. Nachouane, H., A. Najid, A. Tribak, and F. Riouch, "Dual port antenna combining sensing and communication tasks for cognitive radio," International Journal of Electronics and Telecommunications, Vol. 62, No. 2, 121-127, 2016.
11. Srikar, D. and S. Anuradha, "A compact 3 port integrated wide band sensing antenna and narrow band antennas for cognitive radio applications," 2019 PhotonIcs & Electromagnetics Research Symposium --- Spring (PIERS --- Spring), Rome, Italy, June 17-20, 2019.
12. Ramadan, A. H., J. Costantine, M. Al-Husseini, K. Y. Kabalan, Y. Tawk, and C. G. Christodoulou, "Tunable filter-antennas for cognitive radio applications," Progress In Electromagnetics Research B, Vol. 57, 253-265, 2014.
13. Atallah, H. A., A. B. Abdel-Rahman, K. Yoshitomi, and R. K. Pokharel, "Compact frequency reconfigurable filtennas using varactor loaded T-shaped and H-shaped resonators for cognitive radio applications," IET Microwaves, Antennas Propag., Vol. 10, No. 9, 991-1001, 2016.
14. Lee, W. W. and B. Jang, "A tunable MIMO antenna with dual-port structure for mobile phones," IEEE Access, Vol. 7, 34113-34120, 2019.
15. Hannula, J. M., T. O. Saarinen, A. Lehtovuori, J. Holopainen, and V. Viikari, "Tunable eight-element MIMO antenna based on the antenna cluster concept," IET Microwaves, Antennas Propag., Vol. 13, No. 7, 959-965, 2019.
16. Ikeda, T., S. Saito, and Y. Kimura, "A frequency-tunable varactor-loaded single-layer ring microstrip antennas fed by an L-probe with a reduced bias circuit," 2017 International Symposium on Antennas and Propagation (ISAP), Thailand, October 30-November 2, 2017.
17. Fischer, B. E., I. J. Lahaie, M. D. Huang, M. H. A. J. Herben, A. C. F. Reniers, and P. F. M. Smulders, "Measurements corner: Causes of discrepancies between measurements and EM simulations of millimeter-wave antennas," IEEE Antennas Propag. Mag., Vol. 55, No. 6, 139-149, 2013.
18. Chen, C. J., "Design of parallel-coupled dual-mode resonator bandpass filters," IEEE Trans. Components, Packag. Manuf. Technol., Vol. 6, No. 10, 1542-1548, 2016.
19. Liu, Q., D. F. Zhou, D. W. Zhang, D. L. Lu, and Y. Zhang, "Dual-mode microstrip patch bandpass filters with generalized frequency responses," IEEE Access, Vol. 7, 163537-163546, 2019.
20. Shome, P. P. and T. Khan, "A quintuple mode resonator based bandpass filter for ultra-wideband applications," Microsyst. Technol., Vol. 26, 2295-2304, 2020.
21. Lin, S. C., P. H. Deng, Y. S. Lin, C. H. Wang, and C. H. Chen, "Wide-stopband microstrip bandpass filters using dissimilar quarter-wavelength stepped-impedance resonators," IEEE Trans. Microw. Theory Tech., Vol. 54, No. 3, 1011-1018, 2006.
22. Sekiya, N. and S. Sugiyama, "HTS dual-band bandpass filters using stub-loaded hair-pin resonators for mobile communication systems," Phys. C Supercond. and Its Appl., Vol. 504, 88-92, 2014.
23. Pozar, D. M., Microwave Engineering, John Wiley & Sons, 2011.
24. Balanis, C. A., Advanced Engineering Electromagnetic, John Wiley & Sons, 1999.
25. Zhang, Z., F. Zhao, and A. Wu, "A tunable open ring coupling structure and its application in fully tunable bandpass filter," Int. J. Microw. Wirel. Technol., Vol. 11, No. 8, 782-786, 2019.
26. Varactor Diode BB659, Data Sheet, Semiconductor and System Solutions-Infineon Technologies, https://www.infineon.com/, January 6, 2022.
27. Wen, L. H., S. Gao, Q. Luo, Q. Yang, W. Hu, and Y. Yin, "A low-cost differentially driven dual-polarized patch antenna by using open-loop resonators," IEEE Trans. Antennas Propag., Vol. 67, No. 4, 2745-2750, 2019.