A Non-Interruptive Link-Variation Monitoring Circuit for Wireless Sensor Applications

As wireless sensor devices are usually deployed where the operating environment changes unpredictably, the ability to evaluate the variation in the wireless link is required for reliable and efficient operations. In this paper, a novel link-variation-to-digital-converter (LDC) that provides real-time assessments on the link variations is proposed. Due to its unique structure, the proposed LDC can adjust the resolution of the output data and does not interrupt the original system functionality. A wireless power receiver prototype with a proposed circuit is implemented in CMOS 0.18 μm with an active area of 500 μm-by-20 μm. Measurements of the prototype show that link-variations due to mismatches in the resonant matching condition as well as physical misalignments can be successfully evaluated with the proposed LDC.