Radio frequency identification (RFID) moisture tag(s) and sensors with extended sensing via capillaries
A wireless sensor includes environment sensing structure, a radio frequency (RF) front-end, and a processing module. When the wireless sensor is positioned proximal to an object, a portion of the environment sensing structure senses an environmental condition in a remote area of the object that effects a characteristic of the RF front-end. The processing module generates a reference value representative of a known environmental condition in the remote area based on the effect on the characteristic of the RF front-end. The processing module generates a sensed value representative of an unknown environmental condition in the remote area based on the effect on the characteristic of the RF front-end when the environment sensing structure is sensing the unknown environmental condition. The processing module transmits, via the RF front-end, at least one of the reference value, the sensed value, or a difference between the reference value and the sensed value.
1. A wireless sensor for monitoring environmental conditions, the wireless sensor comprises:
an environment sensing structure having a collecting section and a transporting section, wherein, when the wireless sensor is positioned proximal to an object, a portion of the environment sensing structure senses an environmental condition in a remote area of the object;
a radio frequency (RF) front-end operable to receive an inbound RF signal and to transmit an outbound RF signal, wherein the RF front-end is coupled to the environment sensing structure, wherein, when the wireless sensor is positioned proximal to the object, the RF front-end is at a distance from the remote area, and wherein the environment sensing structure effects a characteristic of the RF front-end when the environmental sensing structure is sensing the environmental condition; and
a processing module operably coupled to:
generate a reference value representative of a known environmental condition in the remote area based on the effect on the characteristic of the RF front-end when the environment sensing structure is sensing the known environmental condition;
generate a sensed value representative of an unknown environmental condition in the remote area based on the effect on the characteristic of the RF front-end when the environment sensing structure is sensing the unknown environmental condition; and
transmit, via the RF front-end, at least one of the reference value, the sensed value, or a difference between the reference value and the sensed value.
2. The wireless sensor of claim 1 , wherein the environment sensing structure further comprises:
when the wireless sensor is positioned proximal to the object, at least a portion of the collecting section is within the remote area of the object, wherein, when the collecting section is subjected to moisture as the environmental condition, the collecting section collects the moisture, which is transported to the RF front-end via the transporting section to effect the characteristic of the RF front-end.
3. The wireless sensor of claim 1 , wherein the environment sensing structure further comprises:
when the wireless sensor is positioned proximal to the object, at least a portion of the transporting section is within the remote area of the object, wherein, when the transporting section is subjected to moisture as the environmental condition, the transporting section transports the moisture to the collecting section, which collects the moisture and effects the characteristic of the RF front-end.
4. The wireless sensor of claim 1 further comprises:
the object being a car and the remote area being an area within a trunk.
5. The wireless sensor of claim 1 further comprises:
the object is a building material and the remote area is within the building material, wherein the building material includes one or more of: drywall, wood, foam, and glass.
6. The method of claim 1 , wherein the collecting section comprises:
a Wheatstone bridge for detecting minor variations in the environmental condition.
7. The wireless sensor of claim 1 further comprises:
the environment sensing structure permanently effects the characteristic of the RF front-end when the environmental sensing structure senses the environmental condition and a level of the environmental condition is at or above a threshold level.
8. The wireless sensor of claim 1 , wherein the RF-front end comprises:
an antenna;
a tuning circuit coupled to the antenna;
a receiver section coupled to the antenna; and
a transmitter section coupled to the antenna, wherein the processing module is further operable to:
adjust the tuning circuit when the environment sensing structure is sensing the known environmental condition;
correlate an amount of adjusting of the tuning circuit when the environment sensing structure is sensing the known environmental condition to the reference value;
further adjust the tuning circuit when the environment sensing structure is sensing the unknown environmental condition; and
correlate an amount of adjusting of the tuning circuit when the environment sensing structure is sensing the unknown environmental condition to the sensed value.
9. The wireless sensor of claim 1 further comprises:
a power harvesting circuit to generate a power supply voltage from the inbound RF signal.