Impedance-change mitigation in RFID tags

A method of adjusting an operating point of a rectifier coupled to an input of a Radio Frequency Identification (RFID) integrated circuit (IC) to mitigate intrinsic impedance changes at the IC input associated with RF voltage changes at the IC input, the method comprising:

• at a circuit initialization:
• developing a parameter from an RF input voltage present at the IC input;
• and
• setting the operating point of the rectifier based on the parameter, and subsequent to the circuit initialization;
• detecting a change in the parameter corresponding to a change in the RF input voltage, wherein the change in the RF input voltage also reduces an intrinsic impedance at the IC input;
• and
• increasing the intrinsic impedance by adjusting the operating point of the rectifier based on the detected parameter change to compensate for the reduction.

A method of adjusting an operating point of a rectifier coupled to an input of a Radio Frequency Identification (RFID) integrated circuit (IC) to mitigate intrinsic impedance changes at the IC input associated with RF voltage changes at the IC input, the method comprising:

• developing a parameter from an RF input voltage present at the IC input;
• determining a first value from the parameter at a first time;
• setting an operating point of the rectifier based on the first value;
• determining a second value from the parameter at a second time after the first time;
• detecting, based on the first and second values, a change in the parameter corresponding to a change in the RF input voltage, wherein the change in the RF input voltage also reduces an intrinsic impedance at the IC input;
• and
• increasing the intrinsic impedance by adjusting the operating point of the rectifier based on the second value, to compensate for the reduction.