Broadband Circularly Polarized Stair-Shaped Slot Antenna

Abstract

This article is introducing a novel broadband circularly polarized slot antenna fed by a coplanar waveguide, with simple layer geometry. A simple design procedure, made of seven stages, is extended to achieve the required performances. The antenna consists of two linked rectangular slots and two asymmetrical L-shaped slots embedded in opposite corners of stair-shaped ground plane with two conducting rectangles that are added to the ground plane in conjunction with a U-shaped strip. This strip is protruded into the slot from the signal line of the coplanar waveguide. By using the U-shaped patch and two conducting rectangles, two orthogonal electric fields with quadrature phase difference, it is possible to excite a circularly polarized wave. The proposed antenna, with a size of 45 × 45 × 0.8 mm³ is enabled to operate across 1.9 to 4.5 GHz with a fractional impedance bandwidth of 81.25%; for S₁₁ less than –10 dB. The 3-dB axial ratio bandwidth is enclosed by the voltage standing wave ratio ≤ 2 impedance bandwidth, and can be up to 48.2% (2.33 to 3.81 GHz), which is appropriate for wireless local area network (2.4 to 2.484 GHz), digital multimedia broadcasting (2.605 to 2.655 GHz), and worldwide interoperability for microwave access (3.3 to 3.8 GHz) systems. The proposed design has been investigated by the simulated and measured results.

Keywords:

• slot antenna
• circular polarization
• coplanar waveguide
• broadband antenna