To implement efficient isolation between units of a multi-input multi-output (MIMO) antenna, a defected ground structure (DGS) has been investigated. An antenna with two elements operating at 5.8 GHz and fed by coaxial is considered. To reduce mutual coupling between the elements, a zigzag groove is inserted into the center of two elements formed as a DGS. To verify this design, a scattering matrix was tested, such as reflection coefficient S11 and transmission coefficient S21 between two element ports. Meanwhile, radiation pattern, current distribution, envelope correlation coefficient (ECC), and diversity gain of the antenna were simulated and measured. The results showed that the mutual coupling was reduced by 28.8 dB when a DGS was used, and the ECC was less than 0.02. Owing to these good performances, each antenna element can operate almost independently, and this MIMO antenna can be efficiently applied to the narrow band Internet of Things system.

Pattern reconfigurable phased‐array antennas can implement the function of beam control and overcome the limited scanning angle of traditional phased‐array antennas without affecting the performance and operating frequency. In this article, a linear 1 × 4 phased‐array designed for wide‐angle scanning is presented. The unit includes an improved C‐type dipole antenna, an I‐typed resonator, and a ground. With the help of PIN diodes, the direction of the current on the patch is changed so that the unit can operate in two modes. The designed array has the advantages of a simple bias network, wide‐beam scanning coverage, high gain, and low‐sidelobe levels. Measurement results show that 2.85–3.66 GHz continuous beam scanning has been achieved in the range of −58° to 58°. Meanwhile, gain of up to 11 dBi is obtained, as well as in very good agreement with simulation. The results also verify the reconfigurability of the pattern and the feasibility of the design.

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