Enhanced directivity and bandwidth of a stepped open-slot antenna with L-shaped slots and parasitic strip

In this study, a printed stepped open-slot antenna with unidirectional radiation characteristics is presented. Using a stepped feeding slot and a parasitic metal strip, the impedance matching is improved and a wide bandwidth is achieved. Additionally, by modifying the ground plane with a pair of L-shaped slots, the radiation directivity of the proposed antenna is significantly enhanced and good unidirectional radiation characteristics are obtained. To demonstrate the effectiveness of the design, a prototype antenna is fabricated and tested. Experimental results show that the antenna provides a fractional bandwidth of 101%, ranging from 3.65 to 11.1 GHz with a compact size (30 mm × 30 mm). A moderate gain, which is better than 4 dBi, is also obtained. In addition, a stable radiation directivity, which is fixed in the endfire direction (y-axis direction) is achieved. The measured front-to-back ratio is larger than 9.5 dB within the effective bandwidth.