Energy-optimized design techniques for wireless communication and ubiquitous sensing nodes
Kim, Stephen T.
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The objective of the proposed research is to analyze and develop energy optimized design techniques that can improve the operating efficiency for a wireless sensor device. To enhance the operating efficiency, all active functional blocks in a system should focus on energy conservation while achieving the required tasks. In addition, variations in the operating condition should be properly observed and compensated. Otherwise, a wireless sensor device would consume unnecessary energy for a given task or too little energy to meet the requirements. In this research, design strategies and some new circuit topologies are discussed in terms of ultra-low energy constraints. In particular, the signal processing unit, the memory unit, and the power unit in a conventional wireless sensor device will be main focus. As an example of the signal processing unit, a subthreshold current mode computation system has been designed and tested to prove the "low power consumption" feature of analog signal processing. For the memory unit, conventional SRAM cells are compared to a new fully-gated 10T-SRAM cell. For the power unit, a semi-active high-efficient CMOS rectifier with a reverse leakage control has been developed. It employs a cross-coupled NMOS pair and two leakage control comparators to reduce reverse charge leakage currents. In addition, the adaptive body bias control technique is utilized to improve the reliability of the rectifier. In addition, a novel link-variation sensing technique is proposed. The proposed technique can evaluate operational disturbances such as component mismatches and displacement variations so that the performance of a wireless sensor device in the actual environment can be close to the optimum without wasting an excessive amount of energy.