A frequency reconfigurable antenna with conical radiation pattern is presented. The antenna is mainly composed of a suspended circular patch, eight shorting posts, and a ground plane. The circular patch is loaded with two concentric annular slots, and four varactors are placed across the outer annular slot to vary the resonant frequency of the antenna. Simulated results show that the resonant frequency can be tuned from 3.25 to 5.7 GHz as the capacitance of the varactors is varied from 0.2 to 12 pF, and conical radiation patterns are obtained when the antenna is operated at each resonant frequency. In the simulation, the reversed-bias circuit of the varactor is also included, and it is found that a bias tee or an inductor is not necessary for the proposed reconfigurable antenna. Experiments are also realized using two different varactors, and the measured results indicate that the peak gains of the conical radiation patterns occur around θ = ±40˚, and they are about 4.5 ± 1.5 dBi when the constructed prototypes are operated in the frequency range from 3.1 to 5.7 GHz.
2. Majid, H. A., M. K. A. Rahim, M. R. Hamid, and M. F. Ismail, "A compact frequencyreconfigurable narrowband microstrip slot antenna," IEEE Antennas Wireless Propag. Lett., Vol. 11, 616-619, 2012.
3. Boukarkar, A., X. Q. Lin, Y. Jiang, and X. F. Yang, "A compact frequency-reconfigurable 36- states patch antenna for wireless applications," IEEE Antennas Wireless Propag. Lett., Vol. 17, 1349-1353, 2018.
4. Li, T., H. Zhai, L. Li, and C. Liang, "Frequency-reconfigurable bow-tie antenna with a wide tuning range," IEEE Antennas Wireless Propag. Lett., Vol. 13, 1549-1552, 2014.
5. Ge, L. and K. M. Luk, "Frequency-reconfigurable low-profile circular monopolar patch antenna," IEEE Trans. Antennas Propag., Vol. 62, 3443-3449, 2014.
6. Esmaeili, M. and J.-J. Laurin, "Polarization reconfigurable slot-fed cylindrical dielectric resonator antenna," Progress In Electromagnetics Research, Vol. 168, 61-71, 2020.
7. Singh, P. P., S. K. Sharma, and P. K. Goswami, "A compact frequency reconfigurable printed antenna for WLAN, WiMAX Multiple applications," Progress In Electromagnetics Research C, Vol. 106, 151-161, 2020.
8. Fertas, F., M. Challal, and K. Fertas, "A compact slot-antenna with tunable-frequency for WLAN, WiMAX, LTE, and X-Band applications," Progress In Electromagnetics Research C, Vol. 102, 203-212, 2020.
9. Hussain, R., M. S. Sharawi, and A. Shamim, "4-element concentric pentagonal slot-line-based ultrawide tuning frequency reconfigurable MIMO antenna system," IEEE Trans. Antennas Propag., Vol. 66, 4282-4287, 2018.
10. Nguyen-Trong, N., L. Hall, and C. Fumeaux, "A frequency- and pattern-reconfigurable centershorted microstrip antenna," IEEE Antennas Wireless Propag. Lett., Vol. 15, 1955-1958, 2016.
11. Ge, L., M. Li, J. Wang, and H. Gu, "Unidirectional dual-band stacked patch antenna with independent frequency reconfiguration," IEEE Antennas Wireless Propag. Lett., Vol. 16, 113-116, 2017.
12. Chaouche, Y. B., F. Bouttout, M. Nedil, I. Messaoudene, and I. B. Mabrouk, "A frequency reconfigurable U-shaped antenna for dual-band WiMAX/WLAN systems," Progress In Electromagnetics Research C, Vol. 87, 63-71, 2018.
13. Liu, J., Q. Xue, H. Wong, H. W. Lai, and Y. Long, "Design and analysis of a low-profile and broadband microstrip monopolar patch antenna," IEEE Trans. Antennas Propag., Vol. 61, 11-18, 2013.
14. Lin, S. J. and J. S. Row, "Monopolar patch antenna with dual-band and wide-band operations," IEEE Trans. Antennas Propag., Vol. 56, 900-903, 2008.