Circularly polarized dual frequency band quasi-annular-ring slot antenna for wireless local area networks (WLAN) applications

A novel circularly polarized dual frequency band quasiannular-ring slot antenna is proposed and investigated. The dual frequency bands are obtained by a series microstrip-line-feed configuration electromagnetically coupling to the asymmetric quasi-annular ring slot and the asymmetry is introduced by adding dented structure at the corner of the ring slot (Φ = 45 ). The proposed dual-band CP antenna easily achieves 10 dB impedance bandwidth of 620/440 MHz and 3-dB axial-ratio bandwidth approximating 160/90 MHz at 2.4/5.5 GHz, respectively, indicating the antenna could be used for WLAN applications.