A broadband circularly polarized (CP) slot antenna array fed by a coplanar waveguide (CPW) is proposed. A fan-shaped feed line and three L-shaped grounded strips are embedded in the square slot antenna element to enlarge the bandwidth. Simulated results show that the antenna element can obtain a wide impedance bandwidth with -10 dB reflection coefficient covering 1.7-6.3 GHz (about 115% relative bandwidth) and 3 dB axial ratio (AR) bandwidth covering 2.6-5.2 GHz (about 66%). Using four elements with sequential phase feed, the measured impedance bandwidth and axial ratio bandwidth of the antenna array can be enhanced to 105% (1.65-5.35 GHz) and 71.3% (2.3-4.85 GHz), respectively. Good radiation characteristics with the peak gain of 10.8 dBic over the operating band can be obtained.
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