Broadband High-Gain Circularly Polarized Antenna for Conformal Applications

Abstract

A broadband high gain circularly polarized (CP) antenna with low profile for conformal applications is proposed. The antenna is composed of a complete ground plane, a loop patch, a feeding patch and four parasitic patches. The loop patch with a sequential phase difference of 90 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> is designed to achieve circular polarization resonating in TM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{11}$</tex-math></inline-formula> mode. The four parasitic patches surrounding the loop patch are designed to excite another CP resonant mode, which will widen the bandwidth and improve the gain. To verify the conformal capability of the proposed antenna, the performance under different bending radii is compared and discussed. Finally, the proposed antenna with a profile of 0.054 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{0}$</tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{0}$</tex-math></inline-formula> is the free-space wavelength at the operation frequency of 5.5 GHz) is fabricated and measured. The measured -10 dB impedance bandwidth is 34.8%, 3 dB axial-ratio (AR) bandwidth is 20%, and peak gain is 11.2 dBic.