Electronic Military & Defense magazine was developed for engineers, program managers, project managers, and those involved in the design and development of electronic and electro-optic systems for military, defense, and aerospace applications.
Issue link: https://electronicsmilitarydefense.epubxp.com/i/350588
Feature Developing Wearable Antennas For Military Applications Design considerations for wireless body area networks By Smail Tedjini, Pierre Lemaitre-Auger, and Tsitoha Andriamiharivolamena, LCIS Laboratory – Grenoble Institute of Technology; Franck Tirard, Safran Sagem; and Christophe Mercier, Ardeje W ireless and wearable technologies have been continuously evolving since the beginning of this century [1]. Commonly known as wire- less body area networks (WBANs), they have numerous applications in a variety of domains — especially in military communications. There are various categories of WBANs, including the off- body link that aims to connect wearable clothing, such as a vest, to another item of wearable clothing or a base station. In both situations, the integration of an antenna into the clothing is required. It is worth noting that the proximity of the human body must be taken into account for the design of the wearable antenna. Moreover, the requested radiation features of wearable antennas are closely related to the type and properties of communication they will provide. Thus, a successful design should consider the following parameters: 1. Operating Frequency And Bandwidth Even if the distinction between narrow band and ultra- wideband antennas is made, both cases require the study of the bending and cramping effects [3] that are generated by the natural movement of the body. In addition, the detuning effect must be compliant with the target bandwidth. 2. Radiation Pattern, Space Coverage, and Polarization In most cases, a quasi-omnidirectional operation is required in order to ensure the maximum space coverage of the com- munication. Therefore, a multi-antenna configuration can be used to satisfy this objective. 3. Specific Absorption Rate (SAR) As is the case for radio frequency (RF) wireless devices, the level of electromagnetic power absorbed by the body must respect the limits imposed by the regulations. In several cases, a specific protection device should be added, which results in a complex antenna integration. 4. Realization Approach And Constraints Depending on the technology process used, specific con- straints should be considered. Tissue properties, metallic parts thickness, conductivity, and deposition features can introduce additional constraints in terms of geometrical sizes and shapes. Sample WBAN Design: The Giante Concept The Giante concept was developed in order to satisfy SAR requirements while allowing a simple realization process, particularly with printed technology. The basic principle involved creating a region in which the radiated electromag- netic field was dramatically reduced. It is worth noting that putting any object in a region where the electromagnetic Electronic Military & Defense Annual Resource, 4th Edition 32 Figure 1: The concept of the Giante WBAN requires the placement of the antennas to create a region with a low-level electromagnetic field. Figure 2: Mapping of the electric field of two antenna groups obtained by simulation using the CST Microwave Studio 3D electromagnetic simulator. Two groups of three antennas are used. The type of antenna used is a dipole. Each dipole is fed by a discrete port. The total injected power value is 1 W. The calculated SAR value is 0.62 W/kg.