Circular Ring Fractal UWB Antenna for Microwave Imaging Applications

In this work, an ultra-wideband (UWB) planar antenna design is presented that is suitable for microwave imaging applications. The radiating element is comprised of three connected rings connected through thin metallic strips that correspond to fractal geometry. The antenna’s bottom side utilizes a stair-shaped slot-based partial ground plane to achieve UWB response. The use of a stair-shaped slot also helps in achieving good impedance matching in the UWB frequency range. The proposed antenna design exhibits a total dimension of 18×20 mm
²
. An impedance bandwidth of ≈31.68 GHz is observed within the frequency range of 3.32 GHz ≈ to beyond 35 GHz. Furthermore, the proposed UWB antenna shows a fractional bandwidth (FBW) of 165.35% and a peak gain of ≈8.5 dBi within the desired operating range. It is evident from the results that the proposed antenna exhibits exceptional low-dispersive characteristics across a broad frequency spectrum, which makes it highly suitable for microwave imaging applications.