WIRELESS TEMPERATURE SENSOR

• US 20100040191A1
• Filed: 10/09/2006
• Published: 02/18/2010
• Est. Priority Date: 10/09/2006
• Status: Active Grant

• Current Assignee: Incide SA (Littelfuse Incorporated)
• Original Assignee: Incide SA (Littelfuse Incorporated)
• Inventors: Hernández De Miguel, Javier, Berenguer-Pérez, Roc, Egurrola López, Daniel, Ubarretxena Belandia, Aritz, Antón, César Matinez
• Granted Patent: US 8,573,840 B2
• Time in Patent Office: Days
• US Class Current: 377/25
• CPC Class Codes: G01K 1/024 for remote indication
• CPC Class Codes: G01K 7/32 using change of resonant frequency of a crystal
• CPC Class Codes: G01K 7/346 for measuring temperature based on the time delay of a signal through a series of logical ports

Abstract

The invention relates to an integrated temperature sensor (1) comprising: means (2000) for generating a pulse train (DATA_IN) at an oscillation frequency, means (3000) for counting the number of pulses during a fixed period of time independent of a temperature to be measured (T) and for generating a plurality of bits (b₁₁, b₁₀, . . . , b₀) indicating the number of pulses in the pulse train (DATA_IN), and means (4000) for generating a serial digital signal (DATA_OUT) from said bits (b₁₁, b₁₀, . . . , b₀), in which the means (2000) for generating a pulse train (DATA_IN) include a plurality of logic gates (2410, 2420, 2430, 2440, 2450) which can introduce a delay dependent on the temperature to be measured (T), said means (2000) generating a pulse train (DATA_IN) the oscillation frequency of which is dependent on said temperature to be measured (T). The invention also relates to a temperature measurement method and to a transponder for a wireless system.

Claims

1. Integrated temperature sensor comprising:

means for generating a pulse train, DATA_IN, at a certain oscillation frequency;

means for counting the number of pulses of the pulse train, DATA_IN, during a fixed time independent of a temperature to be measured, T, and for generating a plurality of bits, b₁₁, b₁₀, . . . , b₀, indicating the number of pulses comprised in the pulse train, DATA_IN;

means for generating a serial digital signal, DATA_OUT, DATA_OUT@T, from the plurality of bits, b₁₁, b₁₀, . . . , b₀;

wherein the means for generating a pulse train, DATA_IN, comprise a plurality of logic gates which are capable of introducing a delay dependent on the temperature to be measured, T, the means generating a pulse train, DATA_IN, the oscillation frequency of which is dependent on the temperature to be measured, T.

2. Sensor according to claim 1, wherein the sensor further comprises control means for coordinating the rest of the means of the sensor from at least one reference signal, CLK, independent of the temperature to be measured, T.

3. Sensor according to claim 1, wherein the means generate the pulse train, DATA_IN, from a reference signal, OSC_ENABLE, independent of the temperature to be measured.

4. Sensor according to claim 1, wherein the means for generating a pulse train, DATA_IN, are a ring oscillator.

5. Sensor according to claim 1, wherein the means for generating a pulse train, DATA_IN, comprise:

a power supply voltage activation and deactivation circuit;

a current source;

a startup circuit for the current source;

a pulse generator.

6. Sensor according to claim 5, wherein the current source comprises means for protecting the pulse generator against variations of the power supply voltage, V_DD.

7. Sensor according to claim 5, wherein the pulse generator comprises a plurality of logic gates.

8. Sensor according to claim 7, wherein the plurality of logic gates comprises an odd number of negated logic gates.

9. Sensor according to claim 1, wherein the delay dependent on the temperature which is introduced by the logic gates is due to the fact that when the temperature increases, the mobility of electrons and holes of the transistors forming the logic gates decreases, whereas when the temperature decreases, the mobility increases.

10. Sensor according to claim 1, wherein the means for generating a serial digital signal, DATA_OUT, DATA_OUT@T, from a plurality of bits, b₁₁, b₁₀, . . . , b₀, comprise a parallel-to-serial converter for converting the plurality of bits, b₁₁, b₁₀, . . . , b₀, into a serial digital signal, DATA_OUT, DATA_OUT@T.

11. Sensor according to claim 1, wherein the control means coordinate the rest of the means from a second signal, the signal being an initialization signal, START.

12. Sensor according to claim 1, wherein the sensor is manufactured on a substrate which is chosen from among:

silicon, silicon on insulator, SOI, silicon-germanium, indium phosphide and gallium arsenide.

13. Transponder for a wireless temperature identification system comprising:

means for storing a unique identification code for the transponder;

an antenna which is capable of receiving a temperature request signal from a reader and transmitting to that reader a signal, DATA_OUT, DATA_OUT@T, representing the measured temperature, T;

characterized by comprising an integrated temperature sensor according to claim 1.

14. Transponder according to claim 13, wherein the transponder comprises means for extracting, from a temperature request signal from a reader, a reference signal, CLK, independent of the temperature to be measured, T, in order to be used by the control means of the sensor to coordinate the rest of the means of the sensor.

15. Transponder according to claim 13, wherein the transponder further comprises means for storing the serial digital signal, DATA_OUT, DATA_OUT@T, representing the measured temperature, T.

16. Transponder according to claim 13, wherein the transponder further comprises means for storing a reference digital signal, DATA_OUT@T_REF, representing a reference temperature, T_REF.

17. Transponder according to claim 16, wherein the antenna is capable of transmitting, together with the digital signal, DATA_OUT, DATA_OUT@T, representing the measured temperature, T, the reference digital signal, DATA_OUT@T_REF.

18. Transponder according to claim 13, wherein the transponder is an integrated radio frequency transponder.

19. Wireless temperature identification system comprising:

at least one reader which can transmit a temperature request signal through an antenna and receive through the antenna a signal, DATA_OUT, DATA_OUT@T, representing a measured temperature, T;

characterized by comprising at least one transponder according to claim 13.

20. System according to claim 19, wherein the system is a radio frequency identification, RFID, system.

21. System according to claim 19, wherein the transponder is designed to be implanted in an animal to measure its body temperature.

22. Temperature measurement method comprising the following steps:

generating a pulse train, DATA_IN, at a certain oscillation frequency;

counting the number of pulses of the pulse train, DATA_IN, during a fixed time independent of the temperature to be measured, T, and generating a plurality of bits, b₁₁, b₁₀, . . . , b₀, indicating the number of pulses comprised in the pulse train, DATA_IN;

generating a serial digital signal, DATA_OUT, DATA_OUT@T, from the plurality of bits, b₁₁, b₁₀, . . . , b₀;

wherein the pulse train, DATA_IN, is generated by means of an oscillator comprising a plurality of logic gates which are capable of introducing a delay dependent on the temperature to be measured, T, the oscillation frequency of the pulse train, DATA_IN, being dependent on the temperature to be measured, T.

23. Method according to claim 22, characterized by the step of controlling the previous steps from at least one reference signal, CLK, independent of the temperature to be measured, T.

24. Method according to claim 22, wherein the delay dependent on the temperature which is introduced by the logic gates is due to the fact that when the temperature increases, the mobility of electrons and holes of the transistors forming the logic gates decreases, whereas when the temperature decreases, the mobility increases.

25. Method according to claim 22, wherein the method further comprises the steps of:

before generating the pulse train, DATA_IN, receiving a temperature request from a remote reader;

after generating a serial digital signal, DATA_OUT, DATA_OUT@T, storing that signal, DATA_OUT, DATA_OUT@T, in a memory register and transmitting the signal, DATA_OUT, DATA_OUT@T, to a remote reader through free space.

26. Calibration method of an integrated temperature sensor characterized by the steps of:

performing the temperature measurement method of claim 22 in which the temperature to be measured is a known reference temperature, T_REF;

storing the obtained reference digital signal, DATA_OUT@T_REF, in a memory register.

27. Calibration method according to claim 26, wherein the calibration method comprises a step of transmitting the obtained reference digital signal, DATA_OUT@T_REF, to a remote reader through free space.