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The problem addressed in this study is how to design and test compact antenna arrays for portable Mulitple-Input Multiple-Output (MIMO) transceivers. Mutual coupling in an antenna array affects signal correlation and array radiation efficiency -both of which have dramatic consequences for MIMO channel capacity.Mutual coupling becomes more pronounced as array aperture shrinks and is therefore a critical issue in compact array design. Two novel compact arrays are designed and fabricated for use in MIMO enabled mobile devices.These arrays are extremely compact yet demonstrate acceptable mutual coupling and radiation efficiency because of the MIMO-specific criteria used during their design. An experimental methodology is presented for fair and meaningful characterization of MIMO arrays by field trial. This methodology addresses the issue of capacity normalization and quantifies how well an antenna array's radiation pattern interfaces with multipath propagation.Results are presented from an extensive measurement campaign in which a true MIMO transceiver testbed is outfitted with compact arrays and dipole arrays of various sizes. A comprehensive and fair comparison is made between the compact arrays and dipole arrays in a variety of indoor propagation scenarios. Design recommendations for compact MIMO arrays are given.

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With the recent development of wearable electronics and smart textiles, flexible sensor technology is gaining increasing attention. Compared to flexible film‐based sensors, multimaterial fiber‐based technology offers unique advantages due to the breathability, durability, wear resistance, and stretchability in fabric structures. Despite the significant progress made in the fabrication and application of fiber‐based sensors, none of the existing fiber technologies allow for fully distributed pressure or temperature sensing. Herein, the design and fabrication of thermally drawn multi‐material fibers that offer distributed temperature and pressure measurement capability is reported. Thermoplastic materials, thermoplastic elastomers, and metal electrodes are successfully co‐drawn in one fiber. The embedded electrodes inside the fibers form a parallel wire transmission line, and the local characteristic impedance is designed to change with the temperature or pressure. The electrical frequency domain reflectometry is used to interrogate the impedance change along the fiber and provides information with high spatial resolution. The two types of fibers reported in this manuscript have a pressure sensitivity of 4 kPa and a temperature sensitivity of 2 °C, respectively. This work can pave the road for development of functional fibers and textiles for pressure and temperature mapping.