In this paper, a single layer 4×4 U-slot patch antenna array based on differential feed was developed to achieve a wide bandwidth and low cross polarization with a simple feeding network. A U-slot was cut on a radiation patch to realize a wideband performance, and a microstrip-line fed structure was adopted to make the patch and feed network placed in a single layer. In order to reduce extra cross-polarization level in the H-plane caused by cutting U-slot, differential feed is adopted, which also makes it easily integrated with differential devices (such as differential amplifier) directly without baluns. A single layer U-slot patch array based on differential feed and an array having the same structure but based on normal feed were made and compared with each other. The designed differentially-fed patch array has more than 12% measured impedance bandwidth and stable gain at 18-19 dBi across the operating band from 5.2 to 5.88 GHz. The measured result shows that a better asymmetry of radiation pattern in the E-plane and a lower than -40 dB cross-polarization level in the H-plane can be achieved compared with normally-feed array.
2. Liu, S., W. Wu, and D.-G. Fang, "Single-feed dual-layer dual-band E-shaped and U-slot patch antenna for wireless communication application," IEEE Antennas and Wireless Propagation Letters, 2015.
3. Weigand, S., G. H. Pan, and J. T. Bernhard, "Analysis and design of broad-band single-layer rectangular U-slot microstrip patch antennas," IEEE Trans. Antennas Propag., Vol. 51, No. 3, 457-468, Mar. 2003.
4. Lau, K. L., K. M. Luk, and K. F. Lee, "Wideband U-slot microstrippatch antenna array," Inst. Elect. Eng. Proc. — Microw. Antenns Propag., Vol. 148, No. 1, 41-44, 2001.
5. Wang, H., X. B. Huang, and D. G. Fang, "A single layer wideband U-slot microstrip patch antenna array," IEEE Antennas and Wireless Propagation Letters, Vol. 7, 9-12.
6. Zhang, Y. P. and J. J. Wang, "Theory and analysis of differentiallydriven microstrip antennas," IEEE Trans. Antennas Propag., Vol. 54, No. 4, 1092-1099, 2006.
7. Wong, W. and Y. P. Zhang, "0.18-mm CMOS push-pull power amplifier with antenna in IC package," IEEE Microwave Wireless Comp. Lett., Vol. 14, No. 1, 13-15, 2004.
8. Abele, P., E. Ojefors, K. B. Schad, E. Sonmez, A. Trasser, J. Konle, and H. Schumacher, "Wafer level integration of a 24GHz differential SiGe-MMIC oscillator with a patch antenna using BCB as a dielectric layer," Proc. 11th GAAS Symp., 419-422, Munich, Germany, 2003.
9. Xue, Q., X. Y. Zhang, and C.-H. K. Chin, "A novel differential-fed patch antenna," Antennas and Wireless Propagation Letters, Vol. 5, 471-474, 2006.
10. Brauner, T., R. Vogt, and W. Bachtold, "A differential active patch antenna element for array applications," IEEE T. Microw. Wireless Comp. Lett., Vol. 13, No. 4, 161-163, 2003.
11. Wang, D., K. B. Ng, C. H. Chan, and H. Wong, "A novel wideband differentially-fed higher-order mode millimeter-wave patch antenna," IEEE Trans. Antennas Propag., Vol. 63, No. 2, 466-473, Feb. 2015.
12. Jin, H. Y., C.-C. Chang, H.-J. Li, and Q. Xue, "Differential-fed patch antenna arrays with low cross polarization and wide bandwidths," Antennas and Wireless Propagation Letters, Vol. 13, 1069-1072, 2014.
13. Lin, S. M., J. P. Wang, and G. Zhang, "A new compact ultra-wideband balun for printed balanced antennas," Journal of Electromagnetic Waves and Applications, Vol. 29, No. 12, 1570-1579, 2015.