Patent attributes
A radio frequency identification (RFID) tag includes an antenna structure operable to receive a radio frequency (RF) signal, an RF signal circuit operable to, when enabled, produce the RF signal, a sensing element operably coupled to the antenna structure, a memory, and a processing module. When in a calibration mode, the processing module adjusts the input impedance until a measured power level is substantially equal to the desired input power level, and generates a first digital value based on the amount of the adjustment a power difference between a measured first input power level and a desired power level, and stores the first digital value in the memory, where the first digital value is representative of a known condition. In a sense mode, the processing module adjusts the input impedance until a second measured power level is substantially equal to the desired input power level, and generates a second digital value based on the amount of the adjustment a power difference between a measured first input power level and a desired power level, and the desired power level, and stores the second digital value in the memory, where the second digital value is representative of an unknown condition.
