volume | PIER Journals

Abstract

A circular microstrip antenna (CMSA) cannot be fed directly with 50 Ω microstrip (MS) line, without an inset or an impedance transformer, as all around the periphery the impedance is equally high. The feeding technique such as inset fed or quarter wave transformer makes the antenna geometry asymmetrical. In this paper, a technique using single shorting post and a pair of shorting posts is proposed to match the peripheral impedance of the CMSA with that of the 50 Ω-MS-line feed for operation around 2.45 GHz. The shorting posts perturb the current distribution on the patch, altering the input impedance at the periphery. By selecting proper shorting posts positions a wide range of impedance has been adjusted without altering the patch geometry. Due to symmetric arrangement of the double shorting posts, the proposed antenna configuration has a very low cross-polarization ratio of better than -65 dB at the broadside direction for 2.45 GHz. The simulated results of the directly fed 50 Ω-MS-line CMSAs are experimentally validated with good agreement.

1. Waterhouse, R., "Small microstrip patch antenna," Electronics Letters, Vol. 31, No. 8, 604-605, 1995.
doi:10.1049/el:19950426

2. Kumar, G. and K. P. Ray, Broadband Microstrip Antennas, Artech House, 2003.

3. Wong, K. L., Compact and Broadband Microstrip Antennas, John Wiley & Sons, Inc., 2002.
doi:10.1002/0471221112

4. Satpathy, S. K., K. P. Ray, and G. Kumar, "Compact shorted variations of circular microstrip antennas," Electronics Letters, Vol. 34, No. 2, 137-138, 1998.
doi:10.1049/el:19980203

5. Wong, K. L. and W. S. Chen, "Compact microstrip antenna with dual-frequency operation," Electronics Letters, Vol. 33, No. 8, 646-647, 1997.
doi:10.1049/el:19970433

6. Deshmukh, A. A. and K. P. Ray, "Broadband shorted sectoral microstrip antenna," Progress In Electromagnetics Research C, Vol. 20, 55-65, 2011.
doi:10.2528/PIERC11010202

7. Podilchak, S. K., A. P. Murdoch, and Y. M. M. Antar, "Compact, microstrip-based folded-shorted patches: PCB antennas for use on microsatellites," IEEE Antennas Propag. Mag., Vol. 59, No. 2, 88-95, April 2017.
doi:10.1109/MAP.2017.2655581

8. Rezazadeh, N. and L. Shafai, "A compact microstrip patch antenna for civilian GPS interference mitigation," IEEE Antennas Wireless Propag. Lett., Vol. 17, No. 3, 381-384, March 2018.
doi:10.1109/LAWP.2018.2790958

9. Chakravarty, T. and A. De, "Design of tunable modes and dual-band circular patch antenna using shorting post," IEE Proc. --- Microw., Antennas Propag., Vol. 146, No. 3, 224-228, 1999.
doi:10.1049/ip-map:19990629

10. Porath, R., "Theory of miniaturized shorting-post microstrip antennas," IEEE Trans. Antennas Propag., Vol. 48, No. 1, 41-47, Jan. 2000.
doi:10.1109/8.827384

11. Row, J. S., "A simple impedance-matching technique for patch antennas fed by coplanar microstrip line," IEEE Trans. Antennas Propag., Vol. 53, No. 10, 3389-3391, Oct. 2005.
doi:10.1109/TAP.2005.856375

12. Schaubert, D., F. Farrar, A. Sindoris, and S. Hayes, "Microstrip antennas with frequency agility and polarization diversity," IEEE Trans. Antennas Propag., Vol. 29, No. 1, 118-123, Jan. 1981.
doi:10.1109/TAP.1981.1142546

13. Chapari, A., A. Zeidaabadi Nezhad, and Z. H. Firouzeh, "Analytical approach for compact shorting pin circular patch antenna," IET Microwaves Antennas Propag., Vol. 11, No. 11, 1603-1608, 2017.

14. Zhang, X. and L. Zhu, "An impedance-agile microstrip patch antenna with loading of a shorting pin," 2015 Asia-Pacific Microwave Conference (APMC), 1-3, 2015.

15. Zhang, X. and L. Zhu, "Patch antennas with loading of a pair of shorting pins toward °exible impedance matching and low cross polarization," IEEE Trans. Antennas Propag., Vol. 64, No. 4, 1226-1233, April 2016.
doi:10.1109/TAP.2016.2526079

16. Rathod, S. M., R. N. Awale, and K. P. Ray, "Analysis of a single shorted rectangular microstrip antenna for 50 microstrip line feed," 2016 International Symposium on Antennas and Propagation (APSYM), 1-4, Cochin, 2016.

Mr. Shivraj Mahadusing Rathod

Prof. Raval N. Awale

Professor Kamla Prasan Ray