One of the major limiting factors preventing wide use of wireless sensor networks in practical scenarios is power consumption. Battery-less or passive sensors promise to alleviate this issue and enable a wide variety of embedded sensor applications such as structural health and vehicular monitoring, biomedical applications, smart homes, and smart grids. Embedding these sensors in structures without the need for changing batteries, their rugged design to withstand harsh environments, and coded communication with multiple access features makes this technology a desirable candidate for a variety of applications. Design and analysis of these sensors from a cross layer point of view is studied in this book chapter. State of the art in fabrication and test of this new class of wireless sensor systems is also reviewed. Interactions between lower layer with passive sensors and upper layer with active sensors—a different perspective on cross layer—is exploited to achieve significant performance gains in terms of signal to noise and interference ratio, correlation peak to side-lobe ratio, operation range, and data rate.
Multi-frequency vibration-driven electret generator for wireless sensor applications