Modeling capacitive coupling systems for Body Coupled Communications

Abstract

With the exponential grow of personal wireless devices, issues like power consumption, communication security and interference immunity are gaining more and more importance. Body Area Networks (BAN), due to their reduced range, are by nature relatively low power, but as an answer to achieve even a more confined range, Near Field Communications (NFC) and Body Coupled Communications (BCC) have been proposed. While the first is used to link two devices that are physically very close, the BCC concept broadens the communication range to the region around the human body. One of the possible technologies supporting BCC is based upon relatively low frequency capacitive coupling between emitter and receiver. Understanding the connection between the physical layout of an electromagnetic system and its electrical model is important to understand its performance and critical aspects. However, although much information exists about antennas and their radiated energy, very few work has been done on how energy is transferred between the electrodes used in a capacitive communication system. In this paper we propose a simple model for estimating the gain of a capacitive coupling system. This model has been validated by 3D electromagnetic simulations and double checked with practical experiments performed in a controlled environment (faraday cage with only the minimum indispensable instrumentation equipment). The results are similar within an order of magnitude which, for the intended use of the model, proves to be accurate enough.