Multilayer Circularly Polarized Circular Annular Ring Patch

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 50Ω 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.