In this letter, a new wideband circularly polarized antenna for Radio Frequency Identification (RFID) readers is proposed. A prototype operating in the Ultra-High Frequency (UHF) band is successfully realized and tested using a defected Ground Structure (DGS). This antenna consists of an L-shaped metal strip and a DGS with four tuning stubs. The overall size covers 90*90*1.6 mm3. The measured -10 dB reflection coefficient S11 bandwidth is 27% (800-1020 MHz) and a good radiation pattern and suitable gain coefficient about 3.7 dB have been achieved. Also, an excellent agreement was noticed between simulation and measurement results demonstrating the good performance of the proposed antenna.
2. Chen, H.-M., K.-Y. Chiu, Y.-F. Lin, and S.-A. Yeh, "Circularly polarized slot antenna design and analysis using magnetic current distribution for RFID reader applications," Microwave and Optical Tech. Letters, Vol. 54, No. 9, 2016-2023, doi: 10.1002/mop, 2012.
3. Lee, D. H., P. J. Park, J. P. Kimand, and J. H. Choi, "Aperture-coupled UHF reader antenna for a handheld application," Micro. Opt. Technol. Lett., Vol. 50, 1261-1263, May 2008.
4. Chang, T. N. and J. M. Lin, "A novel circularly polarized patch antenna with serial multislot type loading," IEEE Trans. Antennas Propag., Vol. 55, 3345-3348, Nov. 2007.
5. Tang, Z. J. and Y. G. He, "Broadband microstrip antenna with U and T slots for 2.45/2.41 GHz RFID tag," Electronic Letters, Vol. 45, No. 18, 926-928, 2009, doi: 10.1049/el.2009.0387.
6. Nasimuddin, Z. N. Chen and X. Qing, "Slotted microstrip antennas for circular polarization with compact size," IEEE Antennas Propag. Mag., Vol. 55, No. 2, 124-137, 2013.
7. Oraizi, H. and S. Hedayati, "Miniaturized UWB monopole microstrip antenna design by the combination of Giuseppe Peano and Sierpinski Carpet fractals," Antennas Wirel. Propag. Lett., Vol. 10, 67-70, 2011.
8. Lamminen, A. E. I., A. R. Vimpari, and J. Saily, "UC-EBG on LTCC for 60-GHz frequency band antenna applications," IEEE Trans. Antennas Propag., Vol. 57, No. 10, 2904-2912, 2009.
9. Wong, K. L., Compact and Broadband Microstrip Antennas, 1st Ed., Wiley, NJ, 2002.
10. Kumar, C. and D. Guha, "Linearly polarized elliptical microstrip antenna with improved polarization purity and bandwidth characteristics," Microw. Opt. Technol. Lett., Vol. 54, No. 10, 2309-2314, 2012.
11. Prajapati, P. R., G. G. K. Murthy, A. Patnaik, and M. V. Kartikeyan, "Design of compact circular disc circularly polarized antenna with Koch curve fractal defected ground structure," Proc. of 31st Int. Union of Radio Science General Assembly and Scientific Symp., (URSI GASS 2014), Beijing, China, August 2014.
12. Zhang, C., J. Zhang, and L. Li, "Triple band-notched UWB antenna based on SIR-DGS and fork-shaped stubs," Electronics Letters, Vol. 50, No. 2, 67-69, 2014.
13. Chi, P.-L. and T. Itoh, "Antenna miniaturization using slow wave enhancement factor from loaded transmission line models," IEEE Trans. Antennas Propag., Vol. 59, No. 1, 48-57, 2011.
14. Kim, H.-M. and B. Lee, "Bandgap and slow/fast wave characteristics of defected ground structures including lefthanded features," IEEE Trans. Microw. Theory Tech., Vol. 54, No. 7, 3113-3120, 2006.
15. Biswas, S., D. Guha, and C. Kular, "Control of higher harmonics and their radiation in microstrip antennas using compact defected ground structures," IEEE Trans. Antennas Propag., Vol. 61, No. 6, 3349-3354, 2013.
16. Nashaat, D., H. A. Elsadek, E. Abdallah, H. Elhenawy, and M. F. Iskander, "Multiband and miniaturized inset feed microstrip patch antenna using multiple spiral-shaped defected ground structure (DGS)," Proc. Of IEEE Antennas and Propagation Society Int. Symp., (APSURSI’09), 164, Charleston, South Carolina, 2009.
17. Guha, D., S. Biswas, and C. Kumar, "Annular ring shaped DGS to reduce mutual coupling between two microstrip patches," Proc. of IEEE Applied Electromagnetics Conf. (AEMC), 1-3, Kolkata, India, 2009.
18. Cheng, K. S., E.-H. Lim, and Y.-N. Phua, "Circularly polarized suspended patch antenna fed by modified L-Probe for UHF RFID Reader," Radio Engineering, Vol. 26, No. 4, December 2017.
19. Pan, Y., L. Zheng, H. J. Liu, J. Y. Wang, and R. L. Li, "Directly-fed single-layer wideband RFID reader antenna," Electronic Letters, Vol. 48, No. 11, May 24, 2012.
20. Lin, S.-Y. and Y.-C. Lin, "Printed RFID Reader Antenna with circular polarization and optical technology Letters,", Vol. 000, No. 000, December 2012, DOI 10.1002/mop.