Radio frequency data communication device in CMOS process

• US 20030231566A1
• Filed: 04/09/2003
• Published: 12/18/2003
• Est. Priority Date: 04/09/2002
• Status: Active Grant

• Current Assignee: Xueshan Technologies Inc. (Wi-LAN Inc.)
• Original Assignee: Henry Tin-Hang Yung, Sterling Smith
• Inventors: Smith, Sterling, Yung, Henry Tin-Hang
• Granted Patent: US 6,841,981 B2
• Time in Patent Office: Days
• US Class Current: 369/47.25
• CPC Class Codes: G06K 19/0713 the arrangement including a power charge pump
• 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
• CPC Class Codes: G11C 5/142 Contactless power supplies, e.g. RF, induction, or IR
• CPC Class Codes: H04B 5/0062 in RFID [Radio Frequency Identification] Systems
• CPC Class Codes: H04B 5/77 for interrogation
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

The present invention provides a passive RFID chip with on-chip charge pumps for generating electrical power for the chip from radio frequencies. The passive RFID chip comprises an analog portion and a digital portion. The analog portion primarily comprises a voltage sensor and an AM data detector. The digital portion comprises a state machine digital logic controller. Incoming RF signals enter the chip via external antennas. The RF signals are converted into regulated DC signals by RF-DC converters with the voltage sensor. The RF-DC converters provide power for all the on-chip components and hence the chip does not require external power supply. The incoming RF signals are demodulated by demodulators and enter the AM data detector where the envelope transitions are detected. A voltage alarm is provided to ensure the voltage level does not drop below an operational level of the chip. The logic signals and programming data are controlled by the state machine digital logic controller and the timing signals are provided by an on-chip oscillator.

Claims

1. A self-regulated power supply, comprising:

an RF-DC converter for converting an RF signal at an input node to a power signal at an output node;

a voltage sensor for monitoring said power signal to generate a control signal; and

a shunt element connected to said input node to attenuate said RF signal in response to said control signal;

wherein said voltage sensor drives said control signal at a first slew rate and a second slew rate while said second slew rate is greater than said first slew rate.

2. The self-regulated power supply as claimed in claim 1, wherein said voltage sensor comprises a filter for driving said control signal at a first slew rate and a second slew rate in response to said power signal and a mode control signal;

3. The self-regulated power supply as claimed in claim 2, wherein said filter comprises:

a first unit-gain buffer having a first input coupled to said power signal and a first output; and

a second unit-gain buffer having a second input coupled to said power signal, a second output connected to said first output to generate said control signal, and an enable input connected to said mode control signal;

wherein said second unit-gain buffer has a slew rate greater than that of said first unit-gain buffer, and said second unit-gain buffer is enabled when said mode control signal is asserted.

4. The self-regulated power supply as claimed in claim 3, wherein said filter further comprises a MOS transistor connected to said second unit-gain buffer in parallel and provided with a gate connected to said mode control signal.

5. The self-regulated power supply as claim in claim 1, wherein said RF-DC converter has a plurality of series-connected stages, each of which comprises:

a first diode having an anode connected to an input terminal and a cathode connected to a central terminal;

a second diode having an anode connected to said central terminal and a cathode connected to an output terminal;

a first capacitor connected between said central terminal and said input node;

a second capacitor connected between said output terminal and a reference node; and

a third diode having an anode connected to said output terminal and a cathode connected to said output node.

6. The self-regulated power supply as claimed in claim 5, wherein said first and second diodes are implemented by low threshold diode-connected MOS transistors.

7. The self-regulated power supply as claimed in claim 5, wherein said first and second capacitors are implemented by metal-insulator-metal (MIM) capacitors.

8. The self-regulated power supply as claimed in claim 5, wherein said RF-DC converter further comprises a switch connected between said output terminal of the next last stage and said output node while said switch is controlled by said output terminal of the last stage.

9. An AM data recovery circuit, comprising:

a demodulator for converting an incoming RF signal at an input node to a base-band signal at an output node;

a low pass filter for generating a reference signal that follows and approaches said base-band signal with a time constant;

a comparator for comparing said base-band signal and said reference signal so as to generate a digital data signal;

a reset for generating a reset signal in response to transitions of said digital data signal; and

a switch for resetting said reference signal in response to said reset signal.

10. The AM data recovery circuit as claimed in claim 9, wherein said filter comprises:

a resistor connected to said output node of said demodulator; and

a capacitor connected to said resistor to form a reference signal node at which said reference signal can be generated.

11. The AM data recovery circuit as claimed in claim 10, wherein said switch is a MOS transistor connected to said resistor in parallel while said MOS transistor has a gate controlled by said reset signal.

12. The AM data recovery circuit as claimed in claim 9, wherein said comparator has hysteresis.

13. The AM data recovery circuit as claimed in claim 9, said demodulator has a plurality of series-connected stages, each of which comprises:

a first diode having an anode connected to an input terminal and a cathode connected to a central terminal;

a second diode having an anode connected to said central terminal and a cathode connected to an output terminal;

a first capacitor connected between said central terminal and said input node;

a second capacitor connected between said output terminal and a reference node; and

a third diode having an anode connected to said output terminal and a cathode connected to said output node.

14. The self-regulated power supply as claimed in claim 13, wherein said first and second diodes are implemented by low threshold diode-connected MOS transistors.

15. The self-regulated power supply as claimed in claim 13, wherein said first and second capacitors are implemented by metal-insulator-metal (MIM) capacitors.

16. The self-regulated power supply as claimed in claim 13, wherein said demodulator further comprises a switch connected between said output terminal of the next last stage and said output node while said switch is controlled by said output terminal of the last stage.

17. An AM data recovery circuit, comprising:

a demodulator for converting an incoming RF signal at an input node to a voltage signal at an output node; and

a current-mode data detector for converting said voltage signal into a current source, said current-mode data detector having a current output proportional to the power at said output node of said demodulator such that a demodulated signal can be generated.

18. The AM data recovery circuit as claimed in claim 17, further comprising:

said current-mode data detector for generating a control signal;

a low pass filter for generating another signal in response to said control signal; and

a shunt element connected to said input node of said demodulator to attenuate said RF signal in response to said control signal.