Sensor Signal Processing for Autonomous Wireless Sensors

Wireless sensor networks are nowadays a reality. However, a wireless node must be a truly autonomous system, i.e. it must embed its own power source, generally a battery pack. For this reason, it is of main concern to limit every source of wasted power. In particular, nodes exploit low duty-cycle strategies to increase their life, spending most of their time in low power mode, turning off all devices within the system except a wakeup oscillator. However, in this way some time must be spent waiting for circuitries settling time, especially if a high accuracy measurement is required. In this paper an efficient implementation of a filtering algorithm that is able to reduce this time is discussed. It is based on a hybrid combination of median and mean filter, joining advantages of both linear and non-linear filtering. A well tailored implementation has been experimentally tested and discussed.