Passive radio frequency identification chip with a variable-capacitance diode
View Patent ↗A passive radio frequency identification (RFID) chip with a protection function against high-intensity electromagnetic fields includes an antenna for receiving electromagnetic waves generated by an RFID reader and generating AC electrical signals to output to a power unit at an output of the antenna; an input/output circuit; a logic circuit; the power unit for rectifying the AC electrical signals into DC (direct current) voltage and outputting the DC voltage to the logic circuit and the input/output circuit at an output of the power unit; a variable-capacitance diode including an anode connected with the output of the antenna and a cathode connected to ground; and a diode including an anode connected with the output of the power unit and a cathode connected with the output of the antenna. The passive RFID chip prevents the inner logic circuit and the input/output circuit from being damaged when receives high-intensity electromagnetic waves.
1. A passive radio frequency identification (RFID) chip with a protection function against high-intensity electromagnetic fields comprising:
an antenna for receiving electromagnetic waves generated by an RFID reader and said antenna generating AC electrical signals to output to a power unit at an output of the antenna;
an input/output circuit;
a logic circuit;
the power unit for rectifying the AC electrical signals into DC (direct current) voltage and outputting the DC voltage to the logic circuit and the input/output circuit at an output of the power unit;
a variable-capacitance diode comprising an anode connected with the output of the antenna and a cathode connected to ground; and
a diode comprising an anode connected with the output of the power unit and a cathode connected with the output of the antenna.
2. The passive RFID chip according to claim 1 , wherein the passive RFID chip has a safe voltage and the variable-capacitance diode has a threshold voltage greater than the safe voltage of the passive RFID chip.
3. The passive RFID chip according to claim 2 , wherein the variable-capacitance diode is connected with the antenna in parallel and the connection accordingly decreases a quality factor of the antenna when the variable-capacitance diode switches on.
4. The passive RFID chip according to claim 3 , wherein the variable-capacitance diode switches on when the output DC voltage of the power unit is higher than the threshold voltage of the variable-capacitance diode.
5. The passive RFID chip according to claim 1 , wherein the variable-capacitance diode switches off when the output DC voltage of the power unit is lower than the threshold voltage of the variable-capacitance diode.