In the paper, a wideband circularly polarized (CP) filtering antenna is proposed, which is composed of four bent Vivaldi elements excited with sequential-rotated feeding technique. Since the Vivaldi element has the advantages of high gain and wide bandwidth, it is selected as the radiation element. On this basis, two cross slots are etched on the Vivaldi antenna to increase the gain at lower frequency band, and bent method which has less effect on the overall performance is applied for lowing the profile of the antenna. To realize filtering characteristic, the quadrature four-feed network consisting of one modified miniaturized filtering rat race coupler (FRC) and two compact wideband quadrature couplers is utilized as the sequential-rotated feeding for the Vivaldi elements. Design procedures of the Vivaldi antenna, the modified filtering FRC and the quadrature four-feed network are given. For validation, a prototype is fabricated and measured. Results show that more than 60% fractional bandwidth (FBW) is achieved under the criterions of more than 10 dB return loss and less than 3 dB axial ratio. Within the AR bandwidth, the gain is in the range of 7.5 dBic~10.1 dBic. Out of the operation band, the gain sharply decreases to be lower than -5 dBic with a rectangle coefficient (|Normalized Gain-10-dB/Gain0-dB|) of 1.25, which indicates good filtering performance.
2. Soliman , S. A. M., E. M. Eldesouki, A. M. Attiya, A. P. Freundorfer, and Y. M. M. Antar, "Circularly polarized folded reflectarray antenna," International Microwave and Antenna Symposium (IMAS), 36-40, Cairo, Egypt, March 2023.
3. Li, J., H. Shi, H. Li, and A. Zhang, "Quad-band probe-fed stacked annular patch antenna for GNSS applications," IEEE Antennas Wireless Propag. Lett., Vol. 13, 372-375, 2014.
4. Li, X., Y. Li, J. T. Huang, and O. Yang Du, "A cross-slot loaded miniaturized UWB Vivaldi dual-polarized antenna," International Conference on Microwave and Millimeter Wave Technology (ICMMT), 1-3, Nanjing, China, May 2021.
5. Guo, L., P. Zhang, F. Zeng, Z. Zhang, and C. Zhang, "A novel four-arm planar spiral antenna for GNSS application," IEEE Access, Vol. 9, 168899-168906, 2021.
6. Zhong, Z.-P. and X. Zhang, "A travelling-wave-fed slot spiral antenna with wide axial-ratio bandwidth and beamwidth for GNSS applications," IEEE Open Journal Antennas Propag., Vol. 2, 578-584, 2021.
7. Zhang, Y.-X., Y.-C. Jiao, Z. Zhang, and S. Feng, "Wideband accurate-out-of-phase-fed circularly polarized array based on penta-mode aperture antenna element with irregular cavity," IEEE Trans. Antennas Propag., Vol. 67, No. 1, 638-642, Jan. 2019.
8. Li, X., R. Ma, H. Cai, Y.-M. Pan, and X. Y. Zhang, "High-gain dual-band aperture-shared CP patch antenna with wide AR beamwidth for Satellite Navigation System," IEEE Antennas Wireless Propag. Lett., Vol. 22, No. 8, 1888-1891, Aug. 2023.
9. Cicchetti, R., V. Cicchetti, A. Faraone, L. Foged, and O. Testa, "A compact high-gain wideband lens Vivaldi antenna for wireless communications and through-the-wall imaging," IEEE Trans. Antennas Propag., Vol. 69, No. 6, 3177-3192, Jun. 2021.
10. Zhang, H., Y. Guo, and G. Wang, "A design of wideband circularly polarized antenna with stable phase center over the whole GNSS bands," IEEE Antennas Wireless Propag. Lett., Vol. 18, No. 12, 2746-2750, Dec. 2019.
11. Yang, W. J., Y. M. Pan, and X. Y. Zhang, "A single-layer low-profile circularly polarized filtering patch antenna," IEEE Antennas Wireless Propag. Lett., Vol. 20, No. 4, 602-606, Apr. 2021.
12. Cheng, G., B. Huang, Z. Huang, and L. Yang, "A high-gain circularly polarized filtering stacked patch antenna," IEEE Antennas Wireless Propag. Lett., Vol. 22, No. 5, 995-999, May 2023.
13. Liu, S., Z. Wang, and Y. Dong, "A compact filtering patch antenna with high suppression level and its CP application," IEEE Antennas Wireless Propag. Lett., Vol. 22, No. 4, 769-773, April 2023.
14. Xiang, B. J., S. Y. Zheng, Y. M. Pan, and Y. X. Li, "Wideband circularly polarized dielectric resonator antenna with bandpass filtering and wide harmonics suppression response," IEEE Trans. Antennas Propag., Vol. 65, No. 4, 2096-2101, April 2017.
15. Zhong, X., D. Shen, L. Zhou, D. You, Q. Lin, and X. Zhang, "Circularly polarized filtering antenna based on integrated substrate gap waveguide," IEEE MTT-S International Wireless Symposium (IWS), 1-3, Nanjing, China, 2021.
16. Wang, J. and Y. Zhang, "Broadband high gain circularly polarized filtering antenna," IEEE Conference on Antenna Measurements and Applications (CAMA), 1-3, Guangzhou, China, 2022.
17. Zhang, K., R. Tan, Z. H. Jiang, Y. Huang, L. Tang, and W. Hong, "A compact, ultrawideband dualpolarized Vivaldi antenna with radar cross section reduction," IEEE Antennas Wireless Propag. Lett., Vol. 21, No. 7, 1323-1327, July 2022.
18. Zhao, Z. M., H. M. Liu, J. H. Ren, Z. B. Wang, and S. J. Fang, "Wideband filtering rat-race coupler with shared triple-mode resonator," Electronics, Vol. 12, No. 12, 2023.
19. Liu, H. M., M. Y. Guan, H. X. Zhang, S. J. Fang, and Z. B. Wang, "Compact wideband and harmonic suppressed quadrature coupler using susceptance loaded coupled lines," Microw. Opt. Technol. Lett., Vol. 64, No. 3, 507-514, March 2022.