Method and apparatus for sensing environment using a wireless passive sensor

A method for execution by a radio frequency identification (RFID) tag, the method comprises:

• receiving, by an antenna of the RFID tag, a radio frequency (RF) signal from an RFID reader, wherein the RF signal has a carrier frequency of a plurality of carrier frequencies, wherein the plurality of carrier frequencies spans a broad frequency band;
• determining, by a tuning circuit of the RFID tag, a received power level of the RF signal at the carrier frequency;
• determining, by the tuning circuit, whether the received power level is lower than a power level threshold;
• and
• when the received power level is lower than the power level threshold:
• increasing, by the tuning circuit, the input impedance of the RFID tag by adjusting the tank circuit to produce an adjusted input impedance;
• determining, by the tuning circuit, a most recent power level of the received RF signal based on the adjusted input impedance;
• comparing, by the tuning circuit, the most recent power level with the received power level;
• and
• when the most recent power level is greater than the received power level:
• incrementally increasing, by the tuning circuit, the input impedance of the RFID tag by adjusting the tank circuit until the received power level is substantially equal to the power level threshold.