A Dual Circularly Polarized CPW-fed Square Slot Antenna for WLAN Applications

A dual circularly polarized (DCP) slot antenna with the coplanar waveguide (CPW)-fed structure is introduced in this paper. The antenna is constitutive of a foursquare slot, two inverted L-shaped earthed strips in one diagonal of ground plane, a couple of protruded strips in another diagonal of ground plane, a nearly square radiator and double excitation ports. These inverted L-shaped strips are the key point to get the circular polarization. The pair of protruded strips improve the performance of axial ratio and impedance matching. Under the condition of port 1 fed and port 2 terminal-matched, the polarization of the antenna is left-hand along the +z-axis. The experiment impedance bandwidth is up to 65.1% (1.73-3.4GHz) and the measured circular polarized bandwidth is 46.3% (1.94-3.11GHz). The isolation band between double ports (S21<-10dB) is 18% (2.28-2.73GHz), in which antenna gain is better than 2.5dB.