A Nesting-L Slot Antenna With Enhanced Circularly Polarized Bandwidth and Radiation

In this letter, a new coplanar waveguide (CPW)-fed circularly polarized (CP) antenna with enhanced bandwidth and radiation is proposed for IEEE 802.16 Worldwide Interoperability for Microwave Access (WiMAX) and IEEE 802.11a wireless local area network (WLAN) applications. By protruding a symmetric T-type strip from CPW feedline, a broad input impedance bandwidth is obtained. To widen CP radiation bandwidth, a nesting-L slot (NLS) structure is introduced in the ground. The NLS is formed by an L-shaped perturbation implanted in the corner of an initial L-slot. The CP radiation bandwidth is enhanced by merging the first and second bands. The first band is generated by the initial L-slot, whereas the second band is obtained by the L-shaped perturbation. According to the measured results, the 10-dB return-loss bandwidth is about 110%, and the 3-dB axial-ratio bandwidth (ARBW) is about 60.9%. Finally, by placing a reflector underneath the antenna, one can obtain unidirectional radiation patterns with greatly improved gains.