A VERY COMPACT MIMO ANTENNA WITH TRIPLE BAND-NOTCH FUNCTION FOR PORTABLE UWB SYSTEMS

A very compact triple band-notched multiple input multiple output antenna (MIMO) for ultra-wideband (UWB) communications is fabricated on an FR4 dielectric substrate having the overall size of 18×21×0.8mm3. The proposed antenna consists of two rectangular metal monopoles which are excited by 50-Ω microstrip lines on top of a substrate, and a common protrude ground is at the bottom. To achieve low mutual coupling between radiating elements, a T-shaped stub is protruded from the ground plane. By etching two C-shaped slots on the radiating patches, band-notched functions at 5.15– 6GHz and 7.8–8.4GHz are obtained. The third notch band from 3.3–3.7 GHz is realized by adding Ushaped metal strips to the ground. The measured and simulated results demonstrate that the proposed antenna offers good impedance bandwidth of |S11| ≤ −10 dB from 2.8–12.2 GHz covering whole UWB band except at the designed notch bands, while giving less mutual coupling (|S21|) of lower than −25 dB in the whole UWB band. The measured envelope correlation coefficient (ECC < 0.013), nearly constant gain and stable radiation patterns show that the proposed MIMO antenna is an appropriate candidate for portable UWB systems.