Low-profile Dual-Band Circularly Polarized Antenna for ISM Applications

In this paper, a low-profile dual-band omnidirectional circularly polarized (CP) antenna is presented. This round-sandwich-shaped antenna has optimized size of 0.24λ × 0.24λ × 0.06λ (λ is the wavelength in free space at lowest operating frequency). The horizontal polarization of the antenna is produced by groups of arc-shaped radiation patches placed on the top FR4 substrate which specify two operating frequency bands: 2.4-2.48 GHz and 5.725-5.875 GHz, while a ground plane is mounted over the bottom FR4 substrate and contacts three shorting pins connected to the arcs. By combining with a disk-loaded capacitive coupling feeding pin at the antenna's center generating vertical polarization, the omnidirectional CP radiation is achieved. Moreover, the antenna operates at high radiation efficiency of -1.6 dB at the lower band and -0.6 dB at the upper band, which concludes that this antenna is effectively suitable for the Industrial, Scientific and Medical (ISM) telecommunications and applications.