A multiple-input-multiple-output (MIMO) antenna system for mobile handsets is presented. The proposed MIMO system consists of four identical box-folded planar inverted-F antenna. A broad operating band (1.84-2.69 GHz) with overall MIMO system dimensions of 136 × 68.8 × 6 mm 3 and an element size of only 10 × 10 × 5 mm 3 can be achieved. Lower than −14.2 dB isolation between any two of the elements has been obtained at the whole operating band. The correlation coefficient, radiation pattern and antenna gain are also studied.

In this paper, a flexible antenna with a simple structure, small size (15mm×17mm×1mm), and light weight for medical wearable applications is proposed. The antenna consists of slot radiation elements fed by a coplanar waveguide structure and a floating ground. Flexible conductive cloth MKKTN260 is used to fabricate the antenna, while felt with good insulation is used as the substrate. The measured impedance matching bandwidth (|S 11 |less than -10dB) of the antenna is from 5.578 to 5.898GHz, which can cover the whole ISM 5.8GHz band (5.725-5.825GHz) and perform good wearable radiation characteristics. The floating ground structure and the interaction between slots make the antenna radiated efficiently (the measured peak realized gain is 4.85dBi at 5.8GHz) to the +Z direction, which is away from the human body. Meanwhile, without any specially designed reflecting structures, the specific absorption rate value is below the criterion set by the FCC and ICNIPR. The bending configurations are also studied for this antenna.INDEX TERMS Wearable antenna, floating ground, slot antenna, coplanar waveguide, SAR.

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Planar monopole antenna is proposed as the antenna element to form a compact dual-element multiple-input-multiple-output (MIMO) antenna system for LTE2300 (used in Asia and Africa) and ISM band operation. The system can cover a 310 MHz (2.20-2.51 GHz) operating bandwidth, with the total size of 15.5 mm × 18 mm × 1.6 mm. Measured isolation higher than 16 dB is obtained without any specially designed decoupling structures, while the edge-to-edge element spacing is only 7.8 mm (0.08 at 2.20 GHz). Radiation characteristics, correlation coefficient, and the performance of the whole system with a metal sheet and a plastic housing show this system is competitive for practical MIMO applications. The antenna element is further used to build an eight-element MIMO antenna system; also good results are achieved.

A four element multiple input multiple output (MIMO) antenna system for UWB applications is presented. The system consists of two identical slot dipoles and two identical planar monopoles. Polarization diversity between different kinds of antennas can realize lower coupling between antenna elements, and by using a couple of inverted L-shaped stubs and an inverted Z-shaped stub as decoupling structures, isolation can be further improved. For both simulation and measurement, higher than 17 dB isolation between antenna elements can be obtained through the whole UWB band (3.1-10.6 GHz). The envelope correlation coefficient, antenna gain, efficiency and other performances are also provided.