A CPW-fed slot antenna for achieving dual-band dual-sense circular polarization is introduced. The dual-band circularly polarized operations are generated by the slots loaded in the two opposite corners and the halberd-shaped strip connected at the end of the signal line of the CPW. The left-hand and right-hand circularly polarized performances can be achieved simultaneously for the lower and the upper band, respectively. The measured impedance bandwidth for 10-dB return loss at 2.5 and 3.5 GHz operating bands can be up to 1100 MHz and 260 MHz, respectively. The measured 3-dB axial ratio bandwidths are 30.8% for lower band (LHCP) and 3.1% for upper band (RHCP), which are completely inside their respective impedance bands. The designed antenna has a simple uniplanar structure and occupies a compact size of 40×40 mm2, including the finite ground CPW feeding mechanism. Moreover, the antenna gain variations across the two operating bands are less than 1 dB.
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