Radio tag and system

• US 8,111,138 B2
• Filed: 07/04/2006
• Issued: 02/07/2012
• Est. Priority Date: 10/02/2005
• Status: Active Grant

• Current Assignee: Visible Assets Incorporated (NOV, Inc.)
• Original Assignee: Visible Assets Incorporated (NOV, Inc.)
• Inventors: Stevens, John K, Waterhouse, Paul
• Primary Examiner(s): Wu, Daniel
• Assistant Examiner(s): Tang, Son M
• Application Number:
  US12/089,037
• Publication Number:
  US 20090027166A1
• Time in Patent Office: 2,044 Days
• Field of Search: 340/572.1, 340/572.7, 340 101- 1052, 340/825.56, 340/14.31, 340/13.26
• US Class Current: 340/10.1
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card

Abstract

Passive tags use two antennas with only limited mutual coupling one of which receives a power/clock field and the other of which receives a data signal. An area-reading antenna, or two or more antennas, are deployed to generate the power/clock field, from a base station. The base station, or active tags, or both, generate the data signals from time to time. This topology together with the use of low frequencies permits area reads, and permits small and economical passive tags, and further permits localization of a particular passive tag as being nearby to a particular active tag.

Claims

1. A method for use with a base station and with a plurality of tags, each tag lacking a battery, each tag having a respective unique identifier, each tag having digital logic, each tag defining a first state internal thereto, the method comprising the steps of:

at the base station, transmitting a radio-frequency power signal at a first frequency, the first frequency being below 1 MHZ;

at each tag among the plurality of tags, receiving the radio-frequency power signal by means of a first antenna, the first antenna comprising a high-Q circuit;

at each tag among the plurality of tags, deriving DC power from the radio-frequency power signal;

at each tag among the plurality of tags, developing a power-on-reset signal from the radio-frequency power signal;

at each tag among the plurality of tags, deriving a first clock signal from the radio-frequency power signal, the first clock signal being higher than the first frequency, the derivation of the first clock signal from the radio-frequency power signal being performed without use of a crystal and without use of a phase-locked loop and without use of a resonator;

at each tag among the plurality of tags, resetting the digital logic by the power-on-reset signal, and resetting the first state;

at the base station, transmitting a data signal at a second frequency, the data signal comprising a start signal followed by a serial digital message;

at each tag among the plurality of tags, receiving the data signal by means of a second antenna, the second antenna comprising a low-Q circuit;

at each tag among the plurality of tags, detecting the start signal of the data signal;

at each tag among the plurality of tags, comparing the serial digital message of the data signal with the respective unique identifier;

at each tag among the plurality of tags, in the event of a match between the serial digital message of the data signal and the respective unique identifier, transmitting a first message by means of the second antenna if the first state was not set, and transmitting a second message by means of the second antenna if the first state was set;

at each tag among the plurality of tags, in the event of a match between the serial digital message of the data signal and the respective unique identifier, setting the first state.

2. The method of claim 1 wherein the first clock signal is double the first frequency.

3. The method of claim 1 wherein the comparing step further comprises comparing the serial digital message of the data signal with a first number, the method further comprising:

at each tag among the plurality of tags, in the event of a match between the serial digital message of the data signal and the first number, transmitting the respective unique identifier by means of the second antenna.

4. The method of claim 3 further comprising the steps of:

at the base station, transmitting the first number;

at the base station, receiving a first respective unique identifier;

at the base station, transmitting the first respective unique identifier;

at the base station, receiving the first message;

at the base station, transmitting the first respective unique identifier;

at the base station, receiving the second message.

5. The method of claim 3 further comprising the steps of:

at the base station, transmitting the first number;

at the base station, receiving a first respective unique identifier;

at the base station, transmitting the first respective unique identifier;

at the base station, receiving the first message;

at the base station, transmitting the first number;

at the base station, receiving a second respective unique identifier;

at the base station, transmitting the second respective unique identifier;

at the base station, receiving the first message.

6. A method for use with a base station and with a plurality of tags, each tag lacking a battery, each tag having a respective unique identifier, each tag having digital logic, each tag comprising a fusible link, the method comprising the steps of:

at the base station, transmitting a radio-frequency power signal at a first frequency, the first frequency being below 1 MHZ;

at each tag among the plurality of tags, receiving the radio-frequency power signal by means of a first antenna, the first antenna comprising a high-Q circuit;

at each tag among the plurality of tags, deriving DC power from the radio-frequency power signal;

at each tag among the plurality of tags, developing a power-on-reset signal from the radio-frequency power signal;

at each tag among the plurality of tags, deriving a first clock signal from the radio-frequency power signal, the first clock signal being higher than the first frequency, the derivation of the first clock signal from the radio-frequency power signal being performed without use of a crystal and without use of a phase-locked loop and without use of a resonator;

at each tag among the plurality of tags, resetting the digital logic by the power-on-reset signal, and resetting the first state;

at the base station, transmitting a data signal at a second frequency, the data signal comprising a start signal followed by a serial digital message;

at each tag among the plurality of tags, receiving the data signal by means of a second antenna, the second antenna comprising a low-Q circuit;

at each tag among the plurality of tags, detecting the start signal of the data signal;

at each tag among the plurality of tags, comparing the serial digital message of the data signal with the respective unique identifier;

at each tag among the plurality of tags, in the event of a match between the serial digital message of the data signal and the respective unique identifier, transmitting a first message by means of the second antenna if the fusible link was intact, and transmitting a second message by means of the second antenna if the fusible link was blown.

7. The method of claim 6 wherein the first clock signal is double the first frequency.

8. The method of claim 6 wherein the comparing step further comprises comparing the serial digital message of the data signal with a first number in the event the fusible link is intact or with a second number in the event the fusible link is blown, the method further comprising:

at each tag among the plurality of tags, in the event of a match resulting from the comparison, transmitting the respective unique identifier by means of the second antenna.

9. A tag comprising:

a flip-flop storing a first unasserted state;

a first antenna, the antenna comprising a plurality of turns of wire, the first antenna and associated circuitry having high Q;

a rectifier connected with said first antenna, the rectifier developing DC power for use within the tag, the tag lacking a battery;

a doubler connected with the first antenna, the doubler developing a clock signal that is twice the frequency of RF energy received at the first antenna, the doubler lacking a phased-lock loop and lacking a crystal or resonator;

a second antenna, the antenna comprising a plurality of turns of wire, the second antenna and associated circuitry having low Q, the first and second antennas substantially decoupled with each other;

a receiver connected with the second antenna, the receiver demodulating RF energy received at the second antenna and deriving a serial data stream therefrom;

a driver connected with the second antenna;

a decoder connected with the receiver and receiving the serial data stream therefrom, and with the doubler and receiving the clock signal therefrom, and deriving a received data item as a function of the serial data stream and the clock signal;

logic comparing the received data item with a unique identifier associated with the tag and with a first predetermined number;

the logic responsive to a match between the received data item and the unique identifier for transmitting a message indicative of the match, and for storing an asserted state in the flip-flop, the transmission carried out with respect to the clock signal;

the logic responsive to a match between the received data item and the first predetermined number for transmitting a message indicative of the unique identifier, the transmission carried out with respect to the clock signal.

10. The tag of claim 9 wherein the message transmitted indicative of a match between the received data item and the unique identifier is a function of whether the flip-flop is asserted or unasserted.