A novel multiband MIMO antenna for smartphones with a non-slit metal frame

We propose a novel MIMO antenna which uses the metal frame of smartphones. A metal frame surrounds the housing case. The proposed antenna consists of a metal frame, a feeding plate and three grounding points. The feeding plate does not connect to the metal frame, and it is excited as an electromagnetic coupling. The antenna can generate a multi resonant mode (loop and monopole antenna mode) at around the 0.8 GHz band and the 1.6 to 2.7 GHz bands as well as the 3.5 GHz band. The isolation of the proposed MIMO antenna is below −10dB from 0.7 to 4.0 GHz, which is small. The total efficiency of the antenna shows good performance with −5 dB at 0.8 GHz band, −2.5 dB at 1.6 to 2.7 GHz and 3.5 GHz band (LTE/WWAN/GPS). Also, the advantages of this antenna are a simple structure and its resonant frequency can be controlled easily.