A very compact and small sized 2-element planar Ultra Wide band (UWB) antenna having high isolation with band rejection characteristics designed on a FR4 substrate (23 × 26 × 0.8 mm 3 ) is presented in this paper. Each antenna element have a rectangular stepped-slot and a z-shaped slot, both etched in ground plane. The rectangular slot, proximity fed by a 50 micro-strip transmission line, acts as a main radiator while z-shaped slot acts as a filter for rejecting the full WLAN band (5.15-5.85 GHz). Use of an inverted T-shaped slot near top end of ground plane improves isolation more than 24.5 dB in lower UWB band i.e. 3-5 GHz, while the rectangular vertical slot etched at center of the ground plane near the bottom edge reduces the mutual coupling at lower as well as at higher UWB band i.e. 5 -10.6 GHz. Both measured and simulated results are presented which are found generally in good agreement.INDEX TERMS UWB, isolation, ultra-wide band (UWB), MIMO, WLAN, transmission line, FR4.

In this paper, a 2‐element UWB‐MIMO antenna system is proposed for imaging applications. Each antenna element consists of semi‐circular slot excited by 50 Ω microstrip transmission lines. Two small stubs are used on both sides of the microstrip lines for better impedance matching at higher frequencies. The band‐rejection at WLAN (5.15–5.825 GHz) band is achieved through a U‐shaped slot in the feeding transmission line. The antenna works efficiently from 3.1 to 10.6 GHz, covering the entire standard UWB. Slots in the ground plane are introduced to improve the isolation level between the antenna elements. A minimum isolation of 20 dB is attained in the entire operating band. The proposed antenna has a size of 58 × 27  mm2. Good agreement is obtained between simulated and measured results for reflection coefficient, isolation and consistent radiation patterns over the entire operating band that makes it promising candidate for medical imaging application in UWB.

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