RADIO FREQUENCY IDENTIFICATION TAG

• US 20110068901A1
• Filed: 11/06/2009
• Published: 03/24/2011
• Est. Priority Date: 09/18/2009
• Status: Active Grant

• Current Assignee: National Taiwan University of Science and Technology
• Original Assignee: National Taiwan University of Science and Technology
• Inventors: Liu, Hsin-Chin, Peng, Jhih-Guo
• Granted Patent: US 8,085,130 B2
• Time in Patent Office: Days
• US Class Current: 340/10.1
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs

Abstract

A battery-assisted radio frequency identification (RFID) tag having a battery-assisted circuit and a filter is provided. The battery-assisted circuit generates a radio frequency signal whose frequency is outside an operating frequency band of the RFID tag to supply additional power to the RFID tag. The filter filters the radio frequency signal output from the battery-assisted circuit before the RFID tag demodulates a reader command, so that a modulation depth of the read command is less affected by multi-carrier. By using the battery-assisted circuit and the filter, the RFID tag has a longer read range and is less affected by multipath fading effects.

Claims

1. A radio frequency identification (RFID) tag, comprising:

a signal port, having a first port and a second port;

an antenna, coupled to the signal port for receiving a first radio frequency (RF) signal and transmitting the first RF signal to the signal port;

a battery-assisted circuit, coupled to the signal port, and generating a second RF signal to the signal port, wherein a frequency of the second RF signal is different to that of the first RF signal;

a modulator, coupled between a controller and the signal port;

a power harvester, coupled between the signal port and the controller for converting a synthesized signal received by the signal port, so as to generate an operating power to the controller, wherein the synthesized signal comprises the first RF signal and the second RF signal; and

a filter, coupled between the signal port and a demodulator for filtering the second RF signal in the synthesized signal and transmitting the filtered synthesized signal to the demodulator,

wherein the demodulator down-converts the filtered synthesized signal to generate a base band signal, and transmits the base band signal to the controller.

2. The RFID tag as claimed in claim 1, wherein the battery-assisted circuit comprises:

a battery;

a voltage-controlled oscillator (VCO), coupled to the battery, and generating an oscillating signal; and

a transmitting unit, coupled between the VCO and the signal port for converting the oscillating signal into a first signal and a second signal to form the second RF signal, wherein the second signal is inverted to the first signal.

3. The RFID tag as claimed in claim 1, wherein an operating frequency band of the antenna is between 860 MHz to 960 MHz.

4. The RFID tag as claimed in claim 1, wherein a frequency of the second RF signal is 800 MHz.

5. The RFID tag as claimed in claim 1, wherein the controller has a storage unit.

6. The RFID tag as claimed in claim 5, wherein the storage unit is an electrically erasable and programmable read only memory (EEPROM).

7. The RFID tag as claimed in claim 1, wherein the modulator, the controller, the power harvester, the filter, the demodulator and the signal port are integrated into a RF tag chip.

8. A signal processing circuit for a RFID tag, adapted to be connected to an antenna and receive a first RF signal through the antenna, the signal processing circuit comprising:

a signal port, having a first port and a second port;

a battery-assisted circuit, coupled to the signal port, and generating a second RF signal to the signal port, wherein a frequency of the second RF signal is different to that of the first RF signal;

a modulator, coupled between a controller and the signal port;

a power harvester, coupled between the signal port and the controller for converting a synthesized signal received by the signal port, so as to generate an operating power to the controller, wherein the synthesized signal comprises the first RF signal and the second RF signal; and

a filter, coupled between the signal port and a demodulator for filtering the second RF signal in the synthesized signal and transmitting the filtered synthesized signal to the demodulator,

wherein the demodulator down-converts the filtered synthesized signal to generate a base band signal, and transmits the base band signal to the controller.

9. The signal processing circuit as claimed in claim 8, wherein the battery-assisted circuit comprises:

a battery;

a VCO, coupled to the battery, and generating an oscillating signal; and

a transmitting unit, coupled between the VCO and the signal port for converting the oscillating signal into a first signal and a second signal to form the second RF signal, wherein the second signal is inverted to the first signal.

10. The signal processing circuit as claimed in claim 8, wherein an operating frequency band of the antenna is between 860 MHz to 960 MHz.

11. The signal processing circuit as claimed in claim 8, wherein a frequency of the second RF signal is 800 MHz.

12. The signal processing circuit as claimed in claim 8, wherein the controller has a storage unit.

13. The signal processing circuit as claimed in claim 12, wherein the storage unit is an EEPROM.

14. The signal processing circuit as claimed in claim 8, wherein the modulator, the controller, the power harvester, the filter, the demodulator and the signal port are integrated into a RF tag chip.