Compact Differential Band-Notched Stepped-Slot UWB-MIMO Antenna With Common-Mode Suppression

A compact printed differential multiple-input–multiple-output (MIMO) antenna is presented for ultrawideband system applications with band-notched characteristic. The proposed MIMO antenna element consists of a differential U-shaped microstrip feedline and a stepped-shaped slot, printed on the bottom and top of the substrate, respectively. A half-wavelength resonant stub embedded in the stepped-shaped slot is exploited to obtain notched band, whose center frequency can be adjusted by the length of the stub. The staged slots among antenna elements are introduced to enhance the differential isolation. The final antenna has a compact size of $44 \times 44\; \text{mm}^{2}$. Measured results show that the proposed MIMO antenna achieves −10-dB impedance bandwidth from 2.95 to 10.8 GHz, isolation better than 15.5 dB over the whole operating band, and a notched band from 5.10 to 5.95 GHz.