Circularly Polarized Square Slot Antenna With a Largely Enhanced Axial-Ratio Bandwidth

Abstract

A new easy-to-apply design procedure is proposed in this letter for constructing small wideband circularly polarized (CP) bidirectional and unidirectional square slot antennas. With an asymmetric T-shaped strip protruded from the signal line of the feeding coplanar waveguide (CPW) into the square slot, a reference antenna with a fractional 3-dB axial-ratio bandwidth (abbreviated as CPBW) of about 11% can be obtained. The proposed bidirectional CP slot antenna (BICPSA) can be modified from the reference antenna by stretching the left end of the T-shaped strip upward, by embedding a rectangular metal patch in the square slot, and by implanting a grounded metal strip from the right edge of the slot. The resulting BICPSA has a much larger CPBW of 39.1%, which is about 3.55 times that of the reference antenna. Finally, by placing a simple reflector underneath this BICPSA without changing its structural dimensions, one can obtain unidirectional radiation patterns with a greatly increased gain of 7.6 dBic, but with only a slightly decreased CPBW of 34.3%.

Analysis and Design of Broadband Simultaneous Wireless Information and Power Transfer (SWIPT) System Considering Rectifier Effect

“…The challenge of designing TX antenna is a broadband axial ratio. In order to have a broadband CP antenna, square slot antennas with coplanar waveguide (CPW) fed is recommended [27][28][29]. Not only do these structures enhance the axial ratio bandwidth, but also the impedance bandwidth would be increased.…”

Bandwidth enhancement of circularly polarised slot global navigation satellite systems antenna using an integrated filter‐antenna approach

“…A wide range of CP antennas have been reported to have a wide axial ratio bandwidth (ARBW) to cope with the high channel capacity demanded by modern wireless systems. For example, this can be realised using slot antennas with L-shaped feedlines [3], vertical Lshaped ground planes [4], cross dipoles in the presence of phase delay lines [5][6][7] or asymmetric T-strips fed via coplanar waveguides [8]. Monopole antennas are also a common approach to achieve wideband CP antennas [9][10][11].…”

“…Single-feed slot antennas are simple to fabricate and have a low profile, but usually with a narrow bandwidth and low gain values for being bidirectional. Metal reflectors are traditionally placed at a quarter wavelength to increase directivity [8,13,15] at the expense of reduced bandwidth.…”

Analysis of wideband circularly polarized ring slot antenna using characteristics mode for bandwidth enhancement

“…In Ref. , horizontal stub is connected to enhance the impedance bandwidth while in Ref. , a strip adjacent to the rectangular parasitic element is used to enhance the axial ratio performance.…”