Near-field Investigations for the Optimization of Human Body Communication

• Applicants: Professor Dr. Jens Förstner; Dr.-Ing. Christian Hedayat
• Subject Area: Measurement Systems ; Communication Technology and Networks, High-Frequency Technology and Photonic Systems, Signal Processing and Machine Learning for Information Technology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 545904804

The overall goal of this project is to research a methodology to assess the specific absorption rate (SAR) of electronic devices close to the human body, demonstrated on the use-case of human body communication (HBC) and its optimization. The goal is that SAR will be made visible and assessed using EM-field simulations combined with measured near-field sources of the device under test (DUT). Today, HBC is growing due to the significant increase in monitoring applications in the healthcare, sports, entertainment and the progress of connected devices, as it is an energy-efficient and secure solution for exchanging information between these devices. With HBC the human tissue is used as a propagation medium for data transmission. A very restrictive spectral mask is defined to greatly limit the risk of interference with medical devices (pacemakers, etc.). Hence, the radiated power levels are very restricted to limit the exposure of the human body to electric fields. Therefore, one objective of the project is to link the SAR level on a human body induced by a HBC transmitter to its output level. The HBC signals are strongly influenced by the environment and so HBC emitters must continuously adjust their output level to maintain an acceptable bit error rate. So the aim is to design a HBC transmitter with an electronic control and evaluation system of the emitted levels and a HBC receiver designed with the ability to evaluate the strength of the received signal. A further goal is the design and testing of meta-surfaces to improve the electromagnetic coupling efficiency between the devices. Depending on the efficiency improvement, it is expected to reduce the power consumption of devices thus improving safety related metrics. On the other hand, HBC is a complex mix of several coupling channels that are highly dispersive and dissipative due to the conductivity of the human tissue. Here, we propose to introduce meta-surface supporting new coupling channels that will allow to improve the information transmission between on-body emitter and receiver. Finally, a test method for SAR evaluation will be developed, which is based on a near-field source determined from near-field scanning results (Huygens-Box method). For an accurate data, new smaller probes will be developed with an enhanced spatial resolution. The resulting effects with regard to noise and basic measurement effects shall be investigated. In addition, near-field scanners usually have a metallic base plate for determined measurement conditions. As a negative effect, this plane can influence the DUT and its near-field and leads to the fact that the field on the back cannot be measured. Accordingly, strategies and methods are to be developed to derive a free-space near-field source from real near-field scans. At the final stage of the project, the optimized HBC system will be evaluated regarding SAR with the newly developed near-field scanning method.

• DFG Programme: Research Grants
• International Connection: France
• Partner Organisation: Agence Nationale de la Recherche / The French National Research Agency
• Cooperation Partners: Professor Redha Abdeddaim, Ph.D.; Professor Dr.-Ing. Remy Vauche, Ph.D.