Computing device for processing environmental sensed conditions
A passive wireless temperature sensor includes a radio frequency (RF) front end having a variable input impedance. The RF front end includes an antenna operable to receive an RF signal having a particular carrier frequency and a tuning circuit having a resonant frequency corresponding to the particular carrier frequency. The passive wireless temperature sensor further includes one or more temperature sensing elements coupled to the RF front end. When sensing a temperature, the one or more temperature sensing elements cause a change in the variable input impedance. The passive wireless temperature sensor further includes a processing module operably coupled to the RF front end operable to adjust the resonant frequency of the tuning circuit to compensate for the change in the variable input impedance and generate a coded value representative of the change. The coded value representative of the change corresponds to the sensed temperature.
1. A passive wireless temperature sensor comprises:
a radio frequency (RF) front end having a variable input impedance, wherein the RF front end includes:
an antenna operable to receive an RF signal having a particular carrier frequency; and
a tuning circuit operable to adjust a resonant frequency of the RF front end based on tuning signal such that resonant frequency of the RF front end corresponds to the particular carrier frequency;
a temperature sensing element operable to sense a temperature; and
a processing module operably coupled to the RF front end, wherein the processing module is operable to:
generate the tuning signal based on variances of input impedance of the RF front end; and
generate a coded value to represent the temperature.
2. The passive wireless temperature sensor of claim 1 , wherein the tuning circuit comprises:
an inductor; and
a variable capacitor, wherein the processing module is operable to adjust the variable capacitor to adjust the resonant frequency.
3. The passive wireless temperature sensor of claim 1 , wherein the tuning circuit comprises:
a capacitor; and
a variable inductor, wherein the processing module is operable to adjust the variable inductor to adjust the resonant frequency.
4. The passive wireless temperature sensor of claim 1 further comprises:
memory coupled to the processing module, wherein the processing module is operable to store the coded value in the memory.
5. The passive wireless temperature sensor of claim 1 , wherein the RF front end further includes:
a transmitter section operable to output the coded value using back-scattering.
6. The passive wireless temperature sensor of claim 1 further comprises:
a power detection circuit coupled to the processing module and the RF front end, wherein the power detection circuit is operable to detect a power level of the RF signal.
7. The passive wireless temperature sensor of claim 6 , wherein the processing module is operable to:
transmit the detected power level and the coded value to a reader.
8. A method comprises:
detecting, by a processing module of a passive wireless temperature sensor, a change in a variable input impedance of a radio frequency (RF) front end of the passive wireless temperature sensor, wherein the RF front end has a resonant frequency that is adjustable to correspond to a particular carrier frequency of an RF signal received via an antenna of the RF front end;
adjusting, by the processing module, the resonant frequency of the RF front end to compensate for the change in the variable input impedance;
receive, by the processing module, a sensed temperature from a temperature sensor of the passive wireless temperature sensor; and
generating, by the processing module, a coded value to represent the sensed temperature.
9. The method of claim 8 , wherein the adjusting the resonant frequency of the RF front end comprises:
adjusting, by the processing module, a variable capacitor of a tuning circuit of the RF front end, wherein the tuning circuit includes the variable capacitor and an inductor.
10. The method of claim 8 , wherein the adjusting the resonant frequency of the RF front end comprises:
adjusting, by the processing module, a variable inductor of a tuning circuit of the RF front end, wherein the tuning circuit includes the variable inductor and a capacitor.
11. The method of claim 8 further comprises:
storing, by the processing module, the coded value in memory of the passive wireless temperature sensor.
12. The method claim 8 further comprises:
transmitting, by the processing module via a transmitter section of the passive wireless temperature sensor, the coded value using back-scattering.
13. The method of claim 8 further comprises:
transmitting, by the processing module, a detected power level of the RF signal and the coded value to a reader.