This paper presents two compact ring slot antennas which are suitable for the PCS-1900 and the 2.4/5-GHz triple-band operations. The first antenna consists of three annular ring slots. The outer ring is responsible for exciting the first resonant mode where the middle ring excites the second resonant mode. The inner most rings, through their Y-shape-like slots, create a wide upper operating band by combining the third and fourth resonant modes. To improve this antenna, we have employed circular Photonic Bandgap (PBG) structures in order to obtain a smaller slot antenna with better radiation characteristics. In this design, the cross-polarization level in the E-plane has reduced compared to the first antenna by 5.5 dB, 0.3 dB and 4 dB in three resonant bands. Also, the cross-polarization in H-plane has reduced by an amount of 3 dB. In addition, the obtained results show that the co-polarization patterns are very similar in all three frequency bands. In both cases we have reduced the size of antennas to 56% and 42% respectively, of conventional microstrip slot antennas. The simulation results are verified by measurements.
2. Hosseini, S. A., Z. Atlasbaf, and K. Forooraghi, "A new compact ultra wide band (UWB) planar antenna using glass as substrate," Journal of Electromagnetic Waves and Applications, Vol. 22, No. 1, 47-59, 2008.
3. Hosseini, S. A., Z. Atlasbaf, and K. Forooraghi, "Two new loaded compact palnar ultra-wideband antennas using defected ground structures," Progress In Electromagnetics Research B, Vol. 2, 165-176, 2008.
4. Danideh, A., R. S. Fakhr, and H. R. Hassani, "Wideband coplanar microstrip patch antenna," Progress In Electromagnetics Letters, Vol. 4, 81-89, 2008.
5. Abbaspour, M. and H. R. Hassani, "Wideband star-shaped microstrip patch antenna," PIER Letters, Vol. 1, 61-68, 2008.
6. Boisbouvier, N., F. Le Bolzer, A. Louzir, A.-C. Tarot, and K. Mahdoubi, "Harmonic-less annular slot antenna (ASA) using a novel pbg structure for slot-line printed devices," IEEE Antenna and Propagation Society International Symposium, Vol. 4, 859-862, 2003.
7. Seo, J. and B. Lee, "A performance enhancement of antennas using pbg structures," IEEE Antenna and Propagation Society International Symposium, Vol. 2, 553-556, 2003.
8. Chen, B., B. L. Ooi, M. S. Leong, and F. Hong, "Bandwidth enhancement for multi-band slot antenna by PBG feed," IEEE Antenna and Propagation Society International Symposium, Vol. 2, 2079-2082, 2004.
9. Yang, L., Zh. Feng, F. Chen, and M. Fan, "A novel compact electromagnetic band-gap (EBG) structure and its application in microstrip antenna arrays," Microwave Symposium Digest, 2004 IEEE MTT-S International, Vol. 3, 1635-1638, June 2004.
10. Sung, Y. J. and Y.-S. Kim, "An improved design of microstrip patch antennas using photonic bandgap structure," IEEE Transactions on Antennas and Propagation, Vol. 53, No. 5, 1799-1804, May 2005.
11. Pavlickovski, D. and R. B. Waterhouse, "Shorted microstrip antenna on a photonic bandgap substrate," IEEE Transactions on Antennas and Propagation, Vol. 51, No. 9, 2472-2475, September 2003.
12. Li, R. L., G. DeJean, M. M. Tentzeris, and J. Laskar, "Novel multi-band broadband planar wire antennas for wireless communication handheld terminals," IEEE Antennas and Propagation Society International Symposium, Vol. 3, 44-47, 2003.
13. John, M., M. J. Ammann, and R. Farrell, "Printed triband terminal antenna," IEE Wideband and Multi-band Antennas and Arrays, 19-23, 2005.
14. Brissos, J. and C. Peixeiro, "Triple-band microstrip patch antenna element for GSM1800, UMTS and HiperLAN2," IEEE Antennas and Propagation Society International Symposium, Vol. 4, 130-133, 2003.
15. Behdad, N. and K. Sarabandi, "A compact dual-/multi-band wireless LAN antenna," IEEE Antennas and Propagation Society International Symposium, Vol. 2B, July 2005.
16. Gandara, T. and C. Peixeiro, "Compact double U-slotted microstrip patch antenna element for GSM1800, UMTS and HIPERLAN2," IEEE Antennas and Propagation Society International Symposium, Vol. 2, 1459-1462, 2004.
17. Liu, J.-C., B.-H. Zeng, C.-Y. Wu, and D.-C. Chang, "Synthesis technique of double-ring slot antenna with tree-shaped coupling strip for dual broadband applications," IEE Proc.-Microw. Antennas Propag., Vol. 153, No. 6, December 2006.
18. Chen, J.-S., "Dual-frequency annular-ring slot antennas fed by CPW feed and microstrip line feed," IEEE Transaction on Antennas and Propagation, Vol. 53, No. 1, January 2005.
19. Si, L.-M. and X. Lv, "CPW-FED multi-band omni-directional planar ," Progress In Electromagnetics Research, Vol. 83, 133-146, 2008.
20. Ansoft Corporation, Ansoft HFSS Ver. 10.