A self-calibrating sensor app note from ON Semiconductors. Link is here
ON Semiconductor’s Smart Passive Sensors powered by a Magnus®−S integrated circuit (IC) family offers the industry’s only self-tuning capability, called Chameleon technology. Implemented in an on-chip analog signal processing circuit, Chameleon technology automatically adjusts the input impedance of the IC to optimally tune the tag every time it is accessed.
Sensor tags based on conventional ICs can be detuned by a variety of external factors, most commonly by proximity to liquids or metals. Such factors can change the impedance characteristics of a tag’s antenna. When the tag’s sensor IC has a fixed impedance, a mismatch between the IC and the antenna results thus reducing the tag’s performance. Chameleon technology maintains the IC-antenna match as conditions change, resulting in more consistent sensor tag performance.