In this article, an ultra-wideband printed flexible monopole antenna is proposed for indoor wireless communications. A flexible Rogers RO3003 is used as a substrate, and its performance is estimated for a flat state and when subject to bending along the y-axis. A 2.45 and 5.8 GHz dual-band textile artificial magnetic conductor (AMC) surface consisting of a 4 × 4 unit-cell array was integrated into antenna design with optimum separation distance to extend its potential applications to wearable on-body communications. The specific absorption rate (SAR) levels were numerically investigated using the Hugo human voxel model at both frequencies to evaluate the on-body safety level. Detailed analysis is presented for antenna designs of flat and bent states in free space and on the human body. The proposed UWB flexible antenna has the size of 41 × 38 × 0.25 mm (0.33λ0 × 0.31λ0 × 0.002λ0 at 2.45 GHz). It was added at a distance of 3 mm above a textile AMC surface of 99 × 99 mm. The integrated model is fabricated and experimentally characterized. Measured data and numerical results show that the impedance matching and radiation characteristics are slightly affected by introducing the bending and human body loading. With these remarkable features, the integrated model can be utilized for wireless indoor and wearable applications.

A printed multiband Multi-Input Multiple-Output (MIMO) antenna is proposed in this paper. This MIMO antenna system comprises two symmetric printed monopole antennas. Each antenna element consists of multiple bend lines, producing four resonant modes and covering the GSM900, PCS, LTE2300, and 5G bands. Simulated and measured results prove that the proposed MIMO antenna can be applied to traditional 2G, 3G, 4G, and present 5G mobile communication. By etching four inverted L-shaped grooves on its ground plate, mutual coupling between the adjacent antenna elements has been suppressed. This makes the |S21| at all four resonant modes is lower than −40 dB. In addition, its low coupling mechanism has been analyzed by surface current distribution. The designed multiband MIMO antenna provides an idea of reference to realize low mutual coupling between antenna elements, which is also realizable in infrared or optical regimes with appropriate designs.