This paper presents the effect on circular polarization of multilayer circular annular ring patch (CARP). A CARP have been fabricated on FR4 substrate of dielectric constant 4.2 and thickness 1.52mm. Experimental resonant frequency impedance bandwidth and Axial ratio of simple CARP, covered CARP, spaced dielectric CARP and CARP with two superstrates have been measured and simulated using full wave analysis methods. The Simple CARP is fed diagonal to the radiating patch by a 50 coaxial probe for determining circular polarization (CP) and 3dB Axial Ratio (AR) bandwidth. The simple CARP has been designed and fabricated and found to have a CP-3 dB axial ratio bandwidth of 15MHz at the center fundamental resonant frequency of 1.5514GHz. Covering the simple CARP with various dielectric material of varying thickness shows a 4% increase in 3dB AR bandwidth. Covering the CARP with constant thickness material but with varying dielectric material, both the 10dB impedance bandwidth and 3dB AR bandwidth shows 1.9% and 15% increase with respect to the simple CARP. This type of study is useful for wideband, high gain antenna and to calculate the radome and environmental effect on resonant frequency.

1. Debatosh Guha, “Resonant frequency of circular Microstrip Antenna with and without Air gaps”, IEEE transactions on Antennas and Propagation, vol.49, No.1, pp. 55-59, January 2001.
2. I.J. Bahl and P. Bhartia, “Microstrip Antennas”, Dedham M. A.: Artech House, 1980.
3. J. R .James and P. S. Hall (Eds), “Handbook of Microstrip Antennas”, Peter Peregrinus IEE, London, (1989).
4. Jennifer T. Bernhard and C. J. Tousignant, “Resonant Frequencies of Rectangular Microstrip Antennas with Flush & Spaced Dielectric Superstrates”, IEEE transactions on Antennas and Propagation, Vol.47, No.2, pp.302-307, February 1999,
5. K. M. Luk, W. Y. Tam, C. L. Yip, “Analysis of circular Microstrip antenna with superstrate”, IEE Proceedings, Vol.136, No.3, pp. 261-263, June 1989.
6. K. F. Lee & J. S. Dahele, “The two layered annular ring microstrip antenna“, Int. Journal of Electronics, Vol.61 (2), pp. 207 – 217, 1986.
7. K. F. Lee and J. S. Dahele, “Mode Characteristics of annular-ring and circular-disc microstrip antenna with and without airgaps”, IEEE Antennas and Propagation Soc. Int. Symposium. 1983, pp. 55-58.
8. Raj Kumar and P. Malathi, “Effect of Superstrates on the Resonant frequencies of Rectangular Microstrip Antenna”, IJMOT, Vol. 49, No.12, pp. 2946-2950, Dec.2007.
9. Raj Kumar, P. Malathi and Y.B. Thakare, “On the Design of Four Layered Circular Microstrip Patch Antenna”, IJMOT, Vol.50, No.12, pp. 3206-3212, Dec.2008.
10. S. Sriram & T. S. Vedavathy, “Novel analysis Scheme to Analyze Multilayer dielectric microstrip antennas.” IEEE Digital Lib., DIN.0-7803-5761-2/99, pp. 924-927, 1999,
11. Shun-Shi Zhong, Gang Liu & Ghulam Qasim, “Closed Form expressions for resonant frequency of rectangular patch antennas with Multi-dielectric layers”, IEEE transaction on Antennas and Propagation, Vol.42, No.9, pp. 1360-1363, September 1994.
12. W. S. Chen, C. K. Wu, K. L. Wong, Novel Compact Circularly Polarized Square Microstrip Antenna, IEEE Trans. Antennas Propagation, Vol.49, No.3 , 2001, pp.340-342.
13. X. L. Bao and M. J. Ammann, Compact Annular-ring Embedded Circular Patch Antenna with a Cross-slot Ground Plane for Circular Polarization, Electronics Letters, 2006, 42, (4), 192-193

Circular Annular Ring patch Axial Ratio bandwidth Circular polarization Resonant Frequency Superstrate spaced dielectric