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This paper presents a multi-polarization reconfigurable antenna with four dipole radiators for biomedical applications in body-centric wireless communication system (BWCS). The proposed multi-dipole antenna with switchable 0°, +45°, 90° and -45° linear polarizations is able to overcome the polarization mismatching and multi-path distortion in complex wireless channels as in BWCS. To realize this reconfigurable feature for the first time among all the reported antenna designs, we assembled four dipoles together with 45° rotated sequential arrangements. These dipoles are excited by the same feeding source provided by a ground tapered Balun. A metallic reflector is placed below the dipoles to generate a broadside radiation. By introducing eight PIN diodes as RF switches between the excitation source and the four dipoles, we can control a specific dipole to operate. As the results, 0°, +45°, 90° and -45° linear polarizations can be switched correspondingly to different operating dipoles. Experimental results agree with the simulation and show that the proposed antenna well works in all polarization modes with desirable electrical characteristics. The antenna has a wide impedance bandwidth of 34% from 2.2 to 3.1 GHz (for the reflection coefficient ≤ -10 dB) and exhibits a stable cardioid-shaped radiation pattern across the operating bandwidth with a peak gain of 5.2 dBi. To validate the effectiveness of the multi-dipole antenna for biomedical applications, we also designed a meandered PIFA as the implantable antenna. Finally, the communication link measurement shows that our proposed antenna is able to minimize the polarization mismatching and maintains the optimal communication link thanks to its polarization reconfigurability.

International audienceWe report the concept of a frequency tunable antenna device operating in the millimeter wavefrequency domain. The ability of the antenna to switch between two frequency states is achievedby the monolithic integration of a metal-insulator transition material (vanadium dioxide, VO2). TheVO2 material is an insulator at room temperature but can be driven in a high conductivity metallicstate when it is electrically activated using a continuous (DC) voltage. The antenna design is basedon a slot antenna excited by a microstrip line having a length that can be conveniently varied usinga VO2-based switch. Following the high-frequency VO2 material characterization, we present itsmonolithic integration in the device prototype along with the comparison between the measuredand the simulated performances of the agile antenna. Thus, depending on the VO2 material state,the antenna device can be conveniently switched between 33 and 37 GHz operating frequencybands presenting stable radiation patterns with 5.28 dBi and 5.41 dBi maximum gains, respectively

Ultrafast reconfigurable devices with high‐speed responses, high‐resolution capabilities, and ultracompact sizes will be essential for future real‐time terahertz imaging, chemical detection, nondestructive biosensing, and communication systems. Multifunctional terahertz metasurfaces with active, programmable controls have enabled conspicuous functionalities of subwavelength planar devices and components for manipulating electromagnetic (EM) waves such as beam focusing, polarization modification, generation of exotic EM modes, or multibeam scanning applications. However, active metasurface technologies for EM beam manipulation, capable of dynamical topology change, or induced‐phase reconfiguration are usually requiring various semiconductor‐based controlling elements (e.g., PN diodes and transistors), which are difficult to implement in the high‐frequency spectrum of terahertz waves. In this work, a coding metasurface is introduced integrating patterned GeTe phase‐change materials as command elements, which allows the optical control of terahertz wave propagation. The suggested metasurface design brings plentiful of remarkable functionalities through different coding patterns and is highly effective to control beam tilting, directivity, and splitting of terahertz beams. The proposed concepts of coding metasurfaces integrating optically active phase‐change materials are successfully confirmed by experimental demonstration and can be extended to more complex terahertz systems for imaging, tomography, sensing, and 6G communication applications.