A Compact Wireless Sensor Node with Bidirectional Power Transfer and Optimal Power Efficiency

A compact sensor system with bidirectional power information for optimal power efficiency is designed and implemented in this work. Through the use of bidirectional reconfigurable device-to-device wireless power transmission technology, the transmitting power of the transmitter can be optimized through the energy information fed back from the receiver. For various wireless sensor systems, the required power ranges from nano-Watt to milli-Watt when the sensor nodes operate in different modes. Typically, large-size voltage regulators (DC-DC converters or low-dropout regulators) are required. In this work, a wireless power system that uses bidirectional wireless power transmission is proposed. Energy is transmitted to the sensor node only under the condition where the main control terminal has received the requests. The wireless energy transceiver is designed in TSMC $0.35 \mu \text{m}$ CMOS process, with a total area of 2.07 mm ². The maximum energy transmission is 2W, with peak receiver mode conversion efficiency and overall transmission efficiency of 88% and 67%, respectively.