PASSIVE WIRELESS SENSOR

• US 20160328637A1
• Filed: 12/30/2013
• Published: 11/10/2016
• Est. Priority Date: 12/30/2013
• Status: Active Grant

• Current Assignee: Metso Outotec Finland OY (Metso Outotec Oyj)
• Original Assignee: Metso Flow Control Oy (Neles Oyj)
• Inventors: VIIKARI, Ville
• Granted Patent: US 10,140,566 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06K 19/0717 the sensor being capable of sensing environmental conditions such as temperature history or pressure
• 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: G06K 19/07796 arrangements on the record carrier to allow stacking of a plurality of similar record carriers, e.g. to avoid interference between the non-contact communication of the plurality of record carriers
• CPC Class Codes: H04Q 2209/47 using RFID associated with sensors
• CPC Class Codes: H04Q 9/00 Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom

Abstract

The RFID sensor tag may include normal RFID circuits and functions (such as rectifier, modulator, logic and memory) as well as a resonator-based clock generator or oscillator. The oscillator is a stable resonator-based oscillator having a high Q value. The resonator-based oscillator is loaded with a sensor element which tunes the oscillation frequency, i.e. the oscillation frequency is sensitive to the measured quantity. Thereby, a passive RFID sensor with a resonator-based oscillator and a sensor element is provided, wherein the oscillation frequency can be made dependent on the sensor element if sensing is required. The concept is compatible for existing RFID tags and can enable the possibility to measure external quantities with-out reducing the read-out distance.

Claims

1. A passive wireless transponder, comprising an antenna, a rectifier, an oscillator and a modulator for communication with a backscattering principle to provide radio frequency identification (RFID) features, and a sensing element for sensing a predetermined variable, wherein the oscillator is based on a resonator, and the sensing element is connected to the oscillator, and a modulation frequency output from the oscillator is arranged to be dependent on a sensed value of the predetermined variable.

2. A passive wireless transponder according to claim 1, wherein the sensing element further comprises a control logic and/or a memory for radio frequency identification (RFID) features, such as identification and anti-collision.

3. A passive wireless transponder according to claim 1 or 2, wherein major part of the transponder is implemented with integrated circuit technique, and wherein the sensing element is an external component.

4. A passive wireless transponder according to any one of claims 1-3, wherein the transponder comprises a plurality of sensing elements selectively, one at a time, enabled to load the oscillator such that the modulation frequency output from the oscillator is dependent on a sensed value of the predetermined variable of the enabled sensing element.

5. A passive wireless transponder according to claim 4, wherein the transponder comprises a selection means arranged to selectively enable one and disable the remaining ones of the plurality of sensing elements according to a predetermined sequence or according to a command received from a reader device.

6. A passive wireless transponder according to any one of claims 1-5, wherein major part of the transponder is implemented with an integrated circuit technique, and wherein at least part of the oscillator comprises an external component, such as an external resonator.

7. A passive wireless transponder according to any one of claims 1-6, wherein major part of the transponder is implemented with an integrated circuit technique, and wherein the sensing element and a resonator part of the oscillator are implemented with a resonant sensor or a MEMS resonant sensor.

8. A passive wireless transponder according to any one of claims 1-7, wherein the oscillator based on a resonator comprises one of a LC oscillator, a RLC oscillator, a crystal oscillator, and an oscillator based on a MEMS (microelectromechanical systems) resonator, a SAW (surface acoustic wave) resonator, or a BAW (bulk acoustic wave) resonator.

9. A passive wireless transponder according to claim any one of claims 1-8, wherein the oscillator is one of Collpitts oscillator, Meissner oscillator, Armstrong oscillator, and Hartley oscillator.

10. A passive wireless transponder according to claim any one of claims 1-9, wherein the oscillator is a Collpitts LC or RLCoscillator which comprises an active amplifying device, a capacitive divider, and a feedback inductance.

11. A passive wireless transponder according to claim 10, wherein a voltage level of the modulation frequency output from the LC or RLC oscillator is dependent of a capacitive divider ratio of the capacitive divider.

12. A passive wireless transponder according to claim any one of claims 1-11, comprising one or more of a high pass filter between the antenna and the rectifier, a low pass filter between a DC output of the rectifier and an input of the oscillator, and a band pass filter between an output of the oscillator and an input of the modulator.

13. A passive wireless transponder according to claim any one of claims 1-12, wherein the rectifier comprises a rectifier diode D1, and wherein the rectifier diode also provides a mixer of the modulator.

14. A passive wireless transponder according to claim any one of claims 1-12, wherein the modulated backscattered signal comprises sidebands that are offset from an interrogation frequency by the oscillation frequency which is dependent on the sensed value of the predetermined variable.

15. A system comprising an RFID reader and at least one passive wireless transponder according to any one of claims 1-14.