A compact unidirectional slot antenna with front to back ratio (FBR) enhancement is proposed. The antenna consists of a novel compact slot driven antenna, a stepped reflector and a vertical balun from a microstrip to a parallel strip line. Better FBRs are obtained by optimizing the stepped reflector. Impedance bandwidths are enhanced by applying the balun and a pair of microstrip stub etched on the opposite side of the slot. Then, the antenna is manufactured and measured. Measured results show that the proposed antenna has a bandwidth of 76% (1.53-3.41 GHz) for VSWR ≤ 1.5. In addition, from 1.7 to 3.2 GHz, the antenna gains are higher than 8.6 dBi, and the FBRs are greater than 22 dB. Good agreement between the simulated and measured results is obtained. All above indicates that the proposed antenna can be widely used in wireless communications.
2. Yun, S., D.-Y. Kim, and S. Nam, "Bandwidth enhancement of cavity-backed slot antenna using a via-hole above the slot," IEEE Antennas Wireless Propag. Lett., Vol. 11, 1092-1095, 2012.
3. Chair, R., A. A. Kishk, K. F. Lee, and C. E. Smith, "Unidirectional wideband slot aperture antennas," IEEE Antennas and Propagation Society International Symposium (APSURSI), 1875-1878, 2004.
4. Wang, C. J. and Y. Dai, "Enhancement of pattern directivity for the open slot antenna by utilizing array topology," Microwave Opt. Technol. Lett., Vol. 54, No. 5, 1273-1277, Mar. 2012.
5. Chen, W. Q., G. F. Ding, B. H. Li, and X. F. Li, "Design and simulation of broadband unidirectional CPW-fed rectangular slot antennas," IEEE International Conference on Microwave, Antennas, Propagation and EMC Technologies for Wireless Communications (MAPE), 632-635, 2007.
6. Chaimool, S., P. Akkaraekthalin, and M. Krairiksh, "Reflector shape optimization for wideband uni-directional of CPW-fed slot antenna," International Symposium on Antennas and Propagation, (ISAP), 1206-1209, 2007.
7. Zhang, Z. Y., S.-L. Zuo, and J. Y. Zhao, "Wideband folded bowtie antenna with Γ-shaped strip feed and tuning stubs," Microwave Opt. Technol. Lett., Vol. 55, No. 9, 2145-2149, Jun. 2013.
8. Govindanarayanan, I. and N. Rangaswamy, "Asymmetric folded dipole antenna with high front to back ratio for LTE base stations," IEEE Antennas Wireless Propag. Lett., Vol. 15, 869-872, 2016.
9. Wang, Z. D., X. L. Liu, Y. Z. Yin, and J. J. Wu, "Dual-element folded dipole design for broadband multilayered Yagi antenna for 2G/3G/LTE applications," Electron Lett., Vol. 50, No. 4, 242-244, Feb. 2014.
10. Fei, P., Y. H. Qi, and Y. C. Jiao, "Design of a wideband dual-element slot loop antenna array with adjustable back-reflector," IEEE Antennas Wireless Propag. Lett., Vol. 11, 1014-1017, 2012.
11. Gao, X. Y., Y. H. Qi, and Y. C. Jiao, "Design of multiplate back-reflector for a wideband slot antenna," IEEE Antennas Wireless Propag. Lett., Vol. 12, 773-776, 2013.