A low-profile switched-beam dual-band capacitively coupled Square Loop Antenna

A dual band Square Loop Antenna (SLA) with capacitively coupled feeds is presented for switched beam steering application. Two concentric square loops are capacitively coupled by four rectangular feeding patches. The capacitively coupled feeding mechanism introduces capacitance into the antenna input impedance and cancels the high inductance due to close proximity of the ground plane and helps in the realization of a low profile SLA. The antenna has a height of 3 mm; i.e. λ₀/24 for the operating frequency of 4.1 GHz. The Antenna is designed for operating in 4.1 GHz and 5.2 GHz frequency bands and exhibits an impedance bandwidth of 130 MHz and 160 MHz, respectively. In both frequency bands when any of the four ports is excited, keeping other ports open circuited, the antenna generates a radiation beam tilted (approximately 37°) from the broadside and directed away from the excited port. The antenna has the directivity of 9.2 dBi in the direction of maximum radiation at both the operating frequency. Thus by exciting one port at a time, the antenna can steer its tilted beam in four different quadrants to scan the entire space in front of the antenna.