Wireless low-cost interface

Type: Semester Thesis

Student: Detlef Conradin

Advisor: Ivo Locher

To interconnect the individual components like sensors, information processing systems and output devices a wearable system is also in need of communication channels. Beside wire based communication wireless transmission is desired. For short distances a wireless interface can be implemented by taking advantage of the magnetic induction. The inductive approach has several benefits over a radio solution. Instead of antennas small coils can be used. Compared to the wavelength small antennas have low efficiency. The coils however don't need to radiate waves, the communications takes part in the near field. Such a system can thus be operated from relatively low frequency. This results in very low power consumption. As there are almost no waves radiated there are no multipath  propagation phenomena like fading or inter-symbol interference. This means that there are less complex data processing steps necessary, which reduces cost and power consumption. The goal of the thesis was to implement a simple low speed communication system. In a first step a coil that can be sewed on textiles was investigated. In a next step a very simple detector based ASK Transceiver was implemented, which is shown in the picture above. The resulting system was capable to transmit data over a distance of 10cm. The achieved data rate was only approximately 20 kBit/s, but the power consumption was less than 13mW during sending and less than 1.3mW during reception. With some optimization a higher data rate would be possible.