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Radio-frequency identification systems used for the remote diagnostics of diseases and contactless monitoring and assessment of human health are reviewed. The propagation of electromagnetic waves inside a biological medium and along interfaces between different media, as well as the problem of telemetry data acquisition from implanted systems or system on the human body surface using wireless sensors, is considered. Emphasis is on radio-frequency identification systems that use far-field electromagnetic radiation, since they are necessary in emergency situations to find injured people in hard-to-reach places and assess the state of emergency response workers.

An original structure of tiled transmitarray is presented, comprising a number of topologically similar unit cells arranged in arbitrary pattern within a planar array frame. Each unit cell represents a passive receiver-transmitter structure with integrated phase-shifter, fabricated in commercial 5-layer printed circuit board process, which can take either of two coding states corresponding to 0° or 180° phase shift imparted to the signal transmitting through the device. The unit cell design supports two orthogonal linear polarizations. An example of a 10x10 element 1-bit beam steering transmitarray operated in C-band is demonstrated by simulations and measurements. The proposed structure represents a cost-efficient solution for scalable transmitarrays and also for proof-of-concept experiments in research and education.

A new implementation of a beam-steering transmitarray is proposed based on the tiled array architecture. Each pixel of the transmitarray is manufactured as a standalone unit which can be hard-wired for specific transmission characteristics. A set of complementary units, providing reciprocal phase-shifts, can be assembled in a prescribed spatial phase-modulation pattern to perform beam steering and beam forming in a broad spatial range. A compact circuit model of the tiled unit cell is proposed and characterized with full-wave electromagnetic simulations. Waveguide measurements of a prototype unit cell have been carried out. A design example of a tiled 10 × 10-element 1-bit beam-steering transmitarray is presented and its performance benchmarked against the conventional single-panel, i.e., unibody, counterpart. Prototypes of the tiled and single-panel C-band transmitarrays have been fabricated and tested, demonstrating their close performance, good agreement with simulations and a weak effect of fabrication tolerances. The proposed transmitarray antenna configuration has great potential for fifth-generation (5G) communication systems.

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An original approach of a transmitarray which consists of the tiled unit cells placed in a plastic holder is considered. Each unit cell represents a passive receiver-transmitter structure with integrated phase-shifter, which can take either of two coding states corresponding 180° phase difference between the states. The transmitarray design supports two orthogonal linear polarizations. An example of a 10x10 element 1-bit beam steering transmitarray operated in C-band is presented. The results of radiation pattern measurements with single and multifeed excitation are shown. The proposed structure represents a cost-efficient solution for scalable transmitarrays.