In this paper, design of a coplanar capaciπtive coupled probe fed microstrip ring antenna for dual frequency operation is presented. The proposed antenna is excited by a single probe feed connected to a capacitive feed strip placed along one of the radiating edges of the ring antenna. The coplanar capacitive feed strip is modified to obtain the best possible match with the antenna input impedance and to tune out the excessive capacitive reactance due to feed strip. It is also demonstrated that the modified feed strip can be placed either inside or outside the ring and similar radiation characteristics can be obtained at both the resonant frequencies. Ring dimensions decide the resonant frequencies values and their separation. Measured data fairly agree with the simulated characteristics.
2. Kumar, G. and K. P. Ray, Broadband Microstrip Antennas, Artech House, 2003.
3. Bahl, I. J. and P. Bhartia, Microstrip Antennas, Artech House, 1980.
4. Anguera, J., C. Puente, and C. Borja, "Dual frequency broadband microstrip antenna with a reactive loading and stacked elements," Progress In Electromagnetic Research Letters, Vol. 10, 1-10, 2009.
5. Mayhew-Rydgers, G., J. W. Avondale, and J. Joubert, "New feeding mechanism for annular-ring microstrip antenna," Electronics Letters, Vol. 36, 605-606, 2000.
6. Sze, J. Y., T. H. Hu, and T. J. Chen, "Compact dual-band annular-ring slot antenna with meandered grounded strip," Progress In Electromagnetic Research, Vol. 95, 299-308, 2009.
7. Lee, B. M. and Y. J. Yoon, A dual fed and a dual frequency slots loaded triangular microstrip antenna, IEEE Antenna and Propagation Society Int. Symp., Vol. 3, 1600-1603, 2000.
8. Ren, W., "Compact dual-band slot antenna for 2.4/5 GHz WLAN applications," Progress In Electromagnetic Research B, Vol. 8, 319-327, 2008.
9. Su, C. W., J. S. Row, and J. F. Wu, "Design of a single feed dual-frequency microstrip antenna," Microw. Opt. Technol. Letters, Vol. 47, No. 2, 114-116, 2005.
10. Liao, W. and Q.-X. Chu, "Dual-band circularly polarized microstrip antenna with small frequency ratio," Progress In Electromagnetic Research Letters, Vol. 15, 145-152, 2010.
11. Alkanhal, M. A. S. and A. F. Sheta, "A novel dual-band reconfigurable square-ring microstrip antenna," Progress In Electromagnetic Research, Vol. 70, 337-349, 2007.
12. Chen, H.-M., "Single-feed dual-frequency rectangular microstrip antenna with a π-shaped slot," IEE Proc. --- Microw. Antennas Propag., Vol. 148, No. 1, 60-64, 2001.
13. Ramirez, M. and J. Parron, "Circularly polarized stacked annular-ring microstrip antenna," Progress In Electromagnetic Research Letters, Vol. 23, 99-107, 2011.
14. Kasabegoudar, V. G. and K. J. Vinoy, "A broadband suspended microstrip antenna for circular polarization," Progress In Electromagnetics Research, Vol. 90, 353-368, 2009.
15. Verma, A. K., N. V. Tyagi, and D. Chakraverty, "Input impedance of probe fed multilayer rectangular microstrip patch antenna using the modifiedWolff model," Microw. Opt. Technol. Lett., Vol. 31, No. 3, 237-239, 2001.
16. Abboud, F., J. P. Damiano, and A. Papiernik, "Simple model for the input impedance of the coax-feed rectangular microstrip patch antenna for CAD," Proc. Inst. Elect. Eng., Vol. 135, No. 5, 323-326, 1988.
17. Kasabegoudar, V. G., D. S. Upadhyay, and K. J. Vinoy, "Design studies of ultra wideband microstrip antennas with a small capacitive feed," Int. J. Antennas Propagat., 1-8, 2007.