A Compact Ultrawideband MIMO Antenna Using QSCA for High Isolation

In this letter, a compact ultrawideband (UWB) multiple-input-multiple-output (MIMO) antenna with lower wireless local area network (WLAN) coverage is proposed. The proposed MIMO antenna consists of two quasi-self-complementary monopoles, which are easy to achieve ultrawideband operation. By arranging two monopoles symmetrically, with their main radiation directions oppositely oriented, a UWB MIMO antenna with high isolation is proposed. This high isolation is achieved without using any other decoupling methods, which, totally, benefits from the monopoles' complementary and asymmetrical structures. The measured |S11| has the band of mainly covering 2.19-11.07 GHz except a little higher than -10 dB at 2.86-3.28 GHz, and with |S21| ≤ - 20 dB at most of the band. Since the proposed monopole has excellent inherent properties, a four-element UWB MIMO antenna with good isolation is also discussed.