A CPW-fed printed square slot antenna (PSSA) based on characteristic modes (CMs) theory is investigated for broadband circular polarization (CP). It consists of an I-shaped patch and CPW ground plane loaded with a rectangular stub, a pair of asymmetric inverted-L grounded strips, and a spiral slot to get CP radiation over a wide-angle range. CMs of this strip and slot loaded PSSA show that the entire structure takes participation to excite magnetic and electric modes to provide broadband performance. First six characteristic modes are excited using CPW feeding to find resonating frequencies and radiating behavior. The proposed antenna is fabricated over RO-3003 substrate material with a floor area of 20×20 mm2. Experimental results showcase the broadband CP performance with wide 3-dB ARBW of 56 % (6.6-11.8 GHz) and impedance bandwidth (IBW) (|S11| ≤-10dB) about 115 % (4-11 GHz) which make it suitable for C-band and X-band wireless and satellite communication applications. The antenna has a peak gain about 5.5 dBi with good LHCP radiations in the broadside direction.
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