Semi doughnut pattern Square Loop Antenna for vehicular and wireless applications

Recently, a planar Square Loop Antenna (SLA) with four ports over a Hybrid High Impedance (HHIS) surface was reported which can steer its beam in four different quadrants in front of antenna. This is achieved by exciting one of the four input ports of the antenna and open circuiting the other three. In this work it is shown that the same SLA can be used to generate a semi-doughnut radiation pattern if all of its four ports are excited simultaneously with a signal of the same phase and amplitude. The SLA over HHIS is designed to operate at a frequency of 5.2 GHz and has an impedance bandwidth of 780 MHz for 50 Ω input impedance. The semi doughnut pattern has a maximum directivity of 4.3 dBi over a wide radiation pattern bandwidth of 1 GHz, covering the frequency range from 4.4 GHz to 5.4 GHz.