Low-profile Capacitively Fed steerable Square Loop Antenna

A Capacitively Fed Square Loop Antenna (CFSLA) is presented for switched beam application. The feed mechanism introduces capacitance into the antenna input impedance which cancels out the high dominant inductance due to the probe and the ground plane and makes the SLA low profile. At the operating frequency of 5.2 GHz the net height of the antenna is 3.04 mm (λ₀/19). The antenna has four feeding ports and when one of the ports is excited and the three remaining ports are open circuited the antenna generates a linearly polarized tilted beam directed away from the excited port. Therefore, by exciting one port at a time and open circuiting the other three the antenna can steer the beam in four different quadrants and scan the entire space in front of antenna. The designed antenna has an impedance bandwidth of 350 MHz and a maximum directivity of 9.1 dB at the operating frequency of 5.2 GHz.