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.