Non-linear resonating sensor and a method
Described herein is a passive wireless resonating non-linear sensor that is typically based on a ferroelectric varactor. The sensor replies its data at an intermodulation frequency when a reader device illuminates it at two closely-located frequencies. Furthermore, described herein is a general intermodulation read-out principle for passive wireless sensors. A sensor utilizes a mixing element, such as a varactor and it can be equipped with a capacitive, inductive, or resistive sensor element. When the sensor is illuminated with signals with two frequencies it replies the sensor data at an intermodulation frequency.
1. A reflector element adapted to operate in an area having electromagnetic radiation, comprising:
an antenna for sending reflected electromagnetic energy to a target,
a non-linear element electrically coupled to the antenna, and
a sensor for measuring sensor data, wherein the sensor is operable to provide the sensor data at an intermodulation frequency that is produced in the non-linear element when the sensor detects signals at two frequencies, and
wherein the sensor has an impedance that is sensitive to a measured quantity and a resonance frequency and a quality factor of the sensor is determined based on an intermodulation response, whereby the resonance frequency and the quality factor are related to the impedance that is sensitive to the measured quantity.
2. A reflector element in accordance with claim 1 , wherein the non-linear element is a ferroelectric varactor.
3. A reflector element in accordance with claim 1 , wherein the non-linear element is a paraelectric element.
4. A reflector element in accordance with claim 1 , wherein the non-linear element is a micromechanical resonator.
5. A reflector element in accordance with claim 1 , wherein the non-linear element is a diode.
6. A reflector element in accordance with claim 1 , wherein the reflector element further comprises a directional antenna.
7. A reflector element in accordance with claim 1 , wherein said measured quantity is a temperature.
8. A reflector element in accordance with claim 1 , wherein the target is integrated in an article of clothing or in a bumper of a vehicle.
9. A reflector element in accordance with claim 1 , wherein the sensor is configured to detect an intermodulation frequency reflected signal and/or intermodulation frequency backscatter from the target.
10. A reflector element in accordance with claim 1 , wherein the sensor is configured to detect harmonic reflected signal components and/or harmonic components backscatter from the target.
11. A reflector element in accordance with claim 1 , wherein the reflector element is located in or on a vehicle.