Method and apparatus for sensing environmental parameters using wireless sensor(s)
A passive radio frequency identification (RFID) sensor includes at least one antenna. The least one antenna has an antenna impedance operable to vary within an environment in which the antenna is placed. The RFID sensor further includes a processing module coupled to the antenna comprising a tuning module coupled to the antenna. The tuning module is operable to vary a reactive component impedance coupled to the antenna in order to change a system impedance, the system impedance includes the antenna impedance and the reactive component's impedance, to produce an impedance value representative of the reactive component's impedance. The RFID sensor further includes a memory module operable to store the impedance value representative of the reactive component's impedance, and a wireless communication module coupled to the processing module, operable to communicate with an RFID reader and to exchange the impedance value representative of the reactive component's impedance with the RFID reader.
1. A passive radio frequency identification (RFID) sensor, comprising:
at least one antenna, wherein each at least one antenna has an antenna impedance, the antenna impedance operable to vary within an environment in which the antenna is placed;
a processing module coupled to the antenna, the processing module comprising:
a tuning module coupled to the antenna, the tuning module operable to:
vary a reactive component impedance coupled to the antenna in order to change a system impedance, the system impedance comprising the antenna impedance and the reactive component's impedance, to produce an impedance value representative of the reactive component's impedance;
a memory module operable to store the impedance value representative of the reactive component's impedance; and
a wireless communication module coupled to the processing module, the wireless communication operable to communicate with an RFID reader, the wireless communication module operable to exchange the impedance value representative of the reactive component's impedance with the RFID reader.
2. The passive RFID sensor of claim 1 , wherein the RFID reader communicates the impedance value representative of the reactive component's impedance to a processing unit, the processing unit operable to determine at least one environmental condition at the antenna from the impedance value representative of the reactive component's impedance.
3. The passive RFID sensor of claim 1 , wherein the antenna impedance changes with one or more of pressure, temperature, humidity, wetness, and proximity.
4. The passive RFID sensor of claim 1 , wherein the reactive component impedance comprises a varactor driven by an analog signal from the tuning module, the analog signal enabling a continuous reactive component impedance response.
5. The passive RFID sensor of claim 1 , further comprising:
at least one additional antenna, the at least one additional antenna having a second impedance, the second impedance operable to vary with an environment in which the sensor is placed;
the tuning module coupled to the at least one additional antenna, the tuning module further comprising:
at least one additional variable reactive component coupled to the at least one additional antenna in order to change a new system impedance, the new system impedance comprising the at least one additional antenna impedance and the at least one additional variable reactive component's impedance, the tuning module operable to:
vary the at least one additional reactive component's impedance;
produce an impedance value representative of the variable reactive component's impedance; and
store the impedance value representative of the variable reactive component's impedance.
6. The passive RFID sensor of claim 5 , wherein the at least one antenna are proximate to an external surface of a sensor tube, the sensor tube operable to contain a fluid having at least one of a variable level and variable conductivity.
7. A passive radio frequency identification (RFID) sensor, comprising:
a first inductive loop, wherein the first inductive loop has a first impedance, the first impedance operable to vary in response to an environmental parameter proximate to the first inductive loop;
a processing module coupled to the first inductive loop, the processing module comprising:
a tuning module coupled to the first inductive loop, the tuning module operable to:
vary a first reactive component impedance coupled to the first inductive loop in order to change a system impedance, the system impedance comprising the first inductive loop impedance and the first reactive component's impedance, to produce a first impedance value representative of the first reactive component's impedance;
a memory module operable to store the first impedance value representative of the reactive component's impedance; and
a wireless communication module coupled to the processing module, the wireless communication operable to communicate with an RFID reader, the wireless communication module operable to exchange the first impedance value with the RFID reader.
8. The passive RFID sensor of claim 7 , further comprising:
a second inductive loop, wherein the second inductive loop has a second impedance, the second impedance operable to vary in response to an environmental parameter proximate to the second inductive loop; and
the processing module coupled to the second inductive loop, the processing module operable to report the second impedance value representative of the reactive component's impedance.
9. The passive RFID sensor of claim 7 , wherein the first inductive loop impedance changes with one or more of pressure, temperature, humidity, wetness, and proximity.
10. The passive RFID sensor of claim 7 , wherein first reactive component impedance comprises a varactor.
11. A passive radio frequency identification (RFID) sensor, comprising:
a first inductive loop, wherein the first inductive loop has a first impedance, the first impedance operable to vary in response to one or more environmental parameter proximate to the first inductive loop;
a second inductive loop, wherein the second inductive loop has a second impedance, the second impedance operable to vary in response to one or more environmental parameter proximate to the second inductive loop;
a processing module coupled to the first inductive loop and the second inductive loop, the processing module comprising:
a tuning module coupled to the first inductive loop and the second inductive loop, the tuning module operable to:
vary a reactive component impedance coupled to each inductive loop in order to change a system impedance, the system impedance comprising each inductive loop impedance and the reactive component's impedance, to produce an impedance value representative of each reactive component's impedance;
a memory module operable to store the impedance value representative of the reactive component's impedance; and
a wireless communication module coupled to the processing module, the wireless communication operable to communicate with an RFID reader, the wireless communication module operable to exchange the impedance values with the RFID reader.
12. The passive RFID sensor of claim 11 , wherein the RFID reader communicates the impedance value representative of the reactive component's impedance to a processing unit, the processing unit operable to determine at least one environmental condition at each inductive loop from the impedance value representative of the reactive component's impedance.
13. The passive RFID sensor of claim 11 , wherein each loop inductance impedance changes with one or more of pressure, temperature, humidity, wetness, and proximity.
14. The passive RFID sensor of claim 11 , wherein the reactive component impedance comprises a multiplexed impedance.
15. The passive RFID sensor of claim 11 , wherein the reactive component impedance comprises a variable capacitance coupled to each inductive loop.
16. The passive RFID sensor of claim 11 , wherein the reactive component impedance comprises a varactor coupled to each inductive loop.
17. The passive RFID sensor of claim 11 , wherein the reactive component impedance comprises a varactor coupled to each inductive loop, the varactor driven by an analog signal from the tuning module, the analog signal enabling a continuous reactive component impedance response.
18. The passive RFID sensor of claim 11 , wherein the inductive loop comprises an interdigitated capacitor, wherein the interdigitated capacitor's impedance changes in response to moisture proximate to the interdigitated capacitor.
19. The passive RFID sensor of claim 11 , wherein the inductive loop comprises a conductive plate proximate to a tuning circuit, wherein an external pressure applied to the conductive plate changes an impedance of the tuning circuit.
20. The passive RFID sensor of claim 11 , wherein the inductive loop comprises an interdigitated capacitor, wherein the interdigitated capacitor's impedance changes in response to a change in an environmental dielectric constant proximate to the interdigitated capacitor.