ABSTRACT
This chapter explores different localization techniques where the sensors are randomly distributed. Wired sensor arrays of this type are usually small, with a limited number of sensors strategically placed surrounding a target of interest. As in a regular sensor array, one can think of directivity or the beam pattern of a Distributed Sensor Array (DSA). To achieve milliradian collimation at 1 GHz, as in an inexpensive laser pointer, would require a 100 m antenna, which is indeed impossible in any tiny sensor used in a wireless sensor network (WSN). Thermal sensors utilize the Seebeck effect in which thermoelectric force is generated due to the temperature difference at the contact points between two different metals. The modern micro-electromechanical system (MEMS) microphone is basically a variable capacitor, and its transduction principle is the change of coupled capacitance between a fixed plate and a movable plate, caused by the incoming sound wave.
