A low-profile wideband circularly polarized (CP) microstrip antenna with conical radiation pattern is designed in this paper. Based on the center-fed circular microstrip patch structure, the proposed antenna symmetrically employs 5 shorting vias connecting the patch and the ground plane to provide the θ-polarization and 11 slant sector branches at the edge of circular patch to generate the φ-polarization. With the phase difference of 90° between the two orthogonal polarizations, the design radiates right-handed circularly polarized (RHCP) waves. The proposed antenna works at three resonant modes. To realize broad operating bandwidth, the slant sector branches should be carefully adjusted to make the second resonant mode couple the first mode (TM01 mode) and third mode (TM02 mode) together. The measured results show that the proposed antenna has a low profile of 0.025λ, impedance bandwidth of 35.4% (3.74-5.35 GHz), and axial ratio (AR) bandwidth of 38% (3.7-5.45 GHz). To further verify the characteristics of the proposed antenna, the studies on several important parameters are carried out by HFSS simulation, and a simple design guideline is provided.
2. Pan, Y. M., K.W. Leung, and K. Lu, "Omnidirectional linearly and circularly polarized rectangular dielectric resonant antennas," IEEE Trans. Antennas Propag., Vol. 60, No. 2, 751-759, Feb. 2012.
3. Pan, Y. M. and K. W. Leung, "Wideband omnidirectional circularly polarized dielectric resonator antenna with parasitic strips," IEEE Trans. Antennas Propag., Vol. 60, No. 6, Jun. 2012.
4. Pan, Y. M. and K. W. Leung, "Wideband circularly polarized dielectric bird-nest antenna with conical radiation pattern," IEEE Trans. Antennas Propag., Vol. 61, No. 2, 563-570, 2013.
5. Park, B. C. and J. H. Lee, "Omnidirectional circularly polarized antenna utilizing zeroth-order resonance of epsilon negative transmission line," IEEE Trans. Antennas Propag., Vol. 59, No. 7, 2717-2721, 2011.
6. Li, W. W. and K. W. Leung, "Omnidirectional circularly polarized dielectric resonator antenna with top-loaded Alford loop for pattern diversity design," IEEE Trans. Antennas Propag.,, Vol. 61, No. 8, 4246-4256, Aug. 2013.
7. Yu, D., S. X. Gong, Y. T. Wan, Y. L. Yao, Y. X. Xu, and F. W. Wang, "Wideband omnidirectional circularly polarized patch antenna based on vertex slots and shorting vias," IEEE Trans. Antennas Propag., Vol. 62, No. 8, 3970-3977, Aug. 2014.
8. Lin, W. and H. Wong, "Circularly-polarized conical-beam antenna with wide bandwidth and low profile," IEEE Trans. Antennas Propag., Sep. 2014.
9. Pan, Y. M., S. Y. Zheng, and B. J. Hu, "Wideband and low-profile omnidirectional circularly polarized patch antenna," IEEE Trans. Antennas Propag., Vol. 62, No. 8, 4347-4351, Aug. 2014.
10. Hsiao, F. R. and K. L. Wong, "Low-profile omnidirectional circularly polarized antenna for WLAN access point," Microw. Opt. Technol. Lett., Vol. 46, No. 3, 227-231, 2005.
11. Yu, Y. F., Z. X. Shen, and S. L. He, "Compact omnidirectional antenna of circular polarization," IEEE Trans. Antennas Wireless Propagat. Lett., Vol. 11, 1466-1469, 2012.
12. Liu, J. H., Q. Xue, H. Wong, H. W. Lai, and Y. L. Long, "Design and analysis of a low-profile and broadband microstrip monopolar patch antenna," IEEE Trans. Antennas Propag., Vol. 61, No. 1, 11-18, Jan. 2013.
13. Oraizi, H. and R. Pazoki, "Wideband circularly polarized aperture-fed rotated stacked patch antenna," IEEE Trans. Antennas Propag., Vol. 61, No. 3, 1048-1054, Mar. 2013.
14. Fakhte, S., H. Oraizi, R. Karimian, and R. Fakhte, "A new wideband circularly polarized stairshaped dielectric resonator antenna," IEEE Trans. Antennas Propag., Vol. 63, No. 4, 1828-1831, Apr. 2015.