In this paper, a slotted circular ultra‐wideband (UWB) microstrip patch antenna is reported. The antenna is designed, simulated, fabricated, and tested experimentally. The antenna operates over a 4.0‐40 GHz (164% fractional bandwidth) range with a return loss of 10 dB and voltage standing wave ratio (VSWR) < 2. The designed monopole antenna is of dimensions 28.1 mm × 17.1 mm with an electrical size of 0.37 λ × 0.23 λ at 4 GHz frequency. The antenna is fabricated on FR‐4 substrate with a dielectric permittivity of 4.4, loss tangent of 0.02, and a thickness of 1.4 mm. The designed antenna exhibits nearly omnidirectional radiation patterns over the entire impedance bandwidth with more than 2.8 dB peak gain for the entire frequency range and 75% of average radiation efficiency. The presented antenna can be used in UWB communications along with C‐band, X‐band, Ku‐band, K‐band, Ka‐band, WLAN, and future wireless applications.

A probe-fed patch antenna with 180°ring hybrid is proposed for in-band full-duplex applications. The proposed antenna consists of two substrate layers with the ground plane in between. A patch is printed on one substrate opposite the ground, and a ring hybrid is printed on a second substrate, which is designed to separate the receiving and transmitting signals, producing high isolation between the two. Simulated and fabricated prototype results show isolation of −58 dB covering the Industrial, Scientific and Medical (ISM) band of 2.4-2.5 GHz with a centre frequency of 2.45 GHz.

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