A novel analytical model for a circularly-polarized, ferrite-based slot antenna by solving an integral equation for the electric field on the circular slot

Abstract

We propose and analyze a circularly polarized slot antenna built on a ferrite substrate which is saturated normal to its plane and metalized on both sides. The antenna is built by etching a circular slot in the top metal layer. The antenna operates in the frequency range where the effective permeability of ferrite is negative. An accurate analytical model is derived for the antenna by solving the integral equation for the electric field on the circular slot. The results obtained are in good agreement with numerical simulations. Using the analytical results, a practical antenna is designed that uses a microstrip feed line. For an antenna with inner and outer radii of 4.9 and 5.9 mm, the results show a 3 dB axial ratio (AR) beam width of 200⁰ which is highly desirable in mobile or fixed satellite communication systems such as GPS. Furthermore, the operating frequency can be tuned in the 3.78–3.98 GHz range by changing the magnetic bias field from 15 to 30 kA/m. Compared to other CP antennas, our proposed antenna is compact, has at least twice 3-dB AR beamwidth (200⁰), and is tunable.

KEYWORDS:

• Circular polarization
• analytical model
• ferrite substrate
• integral equation
• tunable antenna
• magnetic permeability tensor
• wide-angle axial ratio

Disclosure statement

No potential conflict of interest was reported by the author(s).