A microstrip antenna system operating in the 2.4 GHz WLAN band is presented for in-band full-duplex operation. The design includes a patch antenna fed by a 180° hybrid. Two feeding methods are presented, probe and aperture. The measured bandwidths are 2.5% (60 MHz) and 2.1% (50 MHz) for the probe fed and aperture fed, respectively. The probe fed system reaches measured isolation (S21) < -50 dB and the aperture fed < -45 dB in a reflective environment. The design also has an omnidirectional radiation pattern, reasonable gain values, and a very low envelope correlation coefficient (<0.01).
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