This paper presents the analysis and design of a two-probe excited circular ring antenna. The analysis is conducted by using induced emf method and transmission line model. The design process is to choose a suitable radius of the ring for a single probe antenna. Then, the suitable probe length and ring length are determined for the two-probe antenna. Finally, isolation between the two probes is enhanced by insertion of an inductor coil between the probes. The operational characteristics of the prototype antenna at the frequency of 5.2 GHz are measured and compared with calculation results. It is evident that these results are in good agreement. The antenna achieved isolation in excess of 20 dB and VSWR less than 2:1 over the desired bandwidth and a bidirectional radiation pattern with 4 dBi gain. This antenna is suitable for Multiple-Input Multiple-Output (MIMO) system covering a long and narrow environment.
2. Jensen, M. A. and J. W. Wallace, "A review of antennas and propagation for MIMO wireless communications," IEEE Trans. Antennas Propag., Vol. 52, 2810-2824, 2004.
3. Kyritsi, P., D. C. Cox, R. A. Valenzuela, and P. W. Wolniansky, "E®ect of antenna polarization on the capacity of a multiple element system in an indoor environment ," IEEE J. Sel. Areas Commun., Vol. 20, 1227-1239, 2002.
4. Svantesson, T., M. A. Jensen, and J. W. Wallace, "Analysis of electromagnetic field polarizations on multiantenna systems," IEEE Trans. Wireless Commun., Vol. 3, 641-646, 2004.
5. Dong, L., H. Choo, R. W. Heath, Jr., and H. Ling, "Simulation of MIMO channel capacity with antenna polarization diversity," IEEE Trans. Wireless Commun., Vol. 4, 1869-1873, 2005.
6. Waldschmidt, C., S. Schulteis, and W. Wiesbeck, "Complete RF system model for analysis of compact MIMO arrays," IEEE Trans. Veh. Technol., Vol. 53, 579-586, 2004.
7. Waldschmidt, C. and W. Wiesbeck, "Compact wide-band multimode antennas for MIMO and diversity," IEEE Trans. Antennas Propag., Vol. 52, 1963-1969, 2004.
8. Wong, M. T. and C. L. Law, "Influence of microstrip patch antenna heights on wideband channel parameters in a static indoor channel," International Journal of Electronics, Vol. 81, 677-698, 1996.
9. Kalis, A., T. Antonakopoulos, C. Soras, and V. Makios, "A switched dual antenna array for mobile computing networks," International Journal of Electronics, Vol. 89, 325-335, 2002.
10. Kosulvit, S., M. Krairiksh, C. Phongcharoenpanich, and T. Wakabayashi, "A simple and cost-effective bidirectional antenna using a probe excited circular ring," IEICE Trans. Electron., Vol. E84-C, 443-450, 2001.
11. Keowsawat, P., C. Phongcharoenpanich, S. Kosulvit, J. Takada, and M. Krairiksh, "Mutual information of MIMO system in a corridor environment based on double directional channel measurement," Journal of Electromagnetic Waves and Applications, Vol. 23, No. 8-9, 1221-1233, Jun. 2009.
12. Balanis, C. A., Antenna Theory Analysis and Design, John Wiley, New York, 1997.
13. Marcuvitz, N., Waveguide Handbook, Peter Peregrinus, London, 1986.
14. Balanis, C. A., Advanced Engineering Electromagnetics, John Wile, New York, 1989.
15. Harrington, R. F., Time-harmonic Electromagnetic Fields, McGraw-Hill, New York, 1961.
16. Elliott, R. S., An Introduction to Guided Waves and Microwave Circuits, Prentice-Hall, Inc., London, 1993.
17. Ludwig, R. and P. Bretchko, RF Circuit Design, Upper Saddle River, Prentice-Hall, NJ, 2000.