PASSIVE WIRELESS ANTENNA SENSOR FOR STRAIN, TEMPERATURE, CRACK AND FATIGUE MEASUREMENT
First Claim
1. A method of monitoring a condition of a structure, comprising:
- transmitting, at a first time, an interrogation signal to a passive wireless antenna sensor mounted on the structure, wherein the interrogation signal includes frequencies in a frequency range, wherein the frequency range includes a resonant frequency of the passive wireless antenna sensor, wherein the passive wireless antenna sensor is configured such that a change in the condition of the structure will change the resonant frequency;
receiving a first backscattered signal, wherein the first backscattered signal comprises an antenna backscattered signal from the passive wireless antenna sensor and a structure backscattered signal from the structure, wherein the antenna backscattered signal is modulated by the passive wireless antenna sensor at a modulated frequency;
detecting a first envelope of the first backscattered signal;
normalizing the first envelope;
selecting a reference amplitude;
determining a first frequency of the first envelope that is associated with the reference amplitude;
transmitting, at a second time, the interrogation signal to the passive wireless antenna sensor mounted on the structure;
receiving a second backscattered signal, wherein the second backscattered signal comprises an antenna backscattered signal from the passive wireless antenna and a structure backscattered signal from the structure, wherein the antenna backscattered signal is modulated by the passive wireless antenna sensor at a modulated frequency;
detecting a second envelope of the second backscattered signal;
normalizing the second envelope;
determining a second frequency of the second envelope that is associated with the reference amplitude;
determining a frequency shift based on a difference between the first frequency and the second frequency; and
determining the condition of the structure based on the frequency shift.
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Accused Products
Abstract
An apparatus and method is provided for monitoring a condition of a structure using a passive wireless antenna sensor having a known resonant frequency when mounted on the structure. A signal is transmitted with sweeping frequencies around a known resonant frequency to the passive wireless antenna sensor. A signal is received from the passive wireless antenna sensor and a resonant frequency of the passive wireless antenna sensor is determined based on the received signal. The determined resonant frequency is then compared to the known resonant frequency, whereby a change in the resonant frequency indicates a change in the condition of the structure.
23 Citations
20 Claims
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1. A method of monitoring a condition of a structure, comprising:
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transmitting, at a first time, an interrogation signal to a passive wireless antenna sensor mounted on the structure, wherein the interrogation signal includes frequencies in a frequency range, wherein the frequency range includes a resonant frequency of the passive wireless antenna sensor, wherein the passive wireless antenna sensor is configured such that a change in the condition of the structure will change the resonant frequency; receiving a first backscattered signal, wherein the first backscattered signal comprises an antenna backscattered signal from the passive wireless antenna sensor and a structure backscattered signal from the structure, wherein the antenna backscattered signal is modulated by the passive wireless antenna sensor at a modulated frequency; detecting a first envelope of the first backscattered signal; normalizing the first envelope; selecting a reference amplitude; determining a first frequency of the first envelope that is associated with the reference amplitude; transmitting, at a second time, the interrogation signal to the passive wireless antenna sensor mounted on the structure; receiving a second backscattered signal, wherein the second backscattered signal comprises an antenna backscattered signal from the passive wireless antenna and a structure backscattered signal from the structure, wherein the antenna backscattered signal is modulated by the passive wireless antenna sensor at a modulated frequency; detecting a second envelope of the second backscattered signal; normalizing the second envelope; determining a second frequency of the second envelope that is associated with the reference amplitude; determining a frequency shift based on a difference between the first frequency and the second frequency; and determining the condition of the structure based on the frequency shift. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An apparatus for monitoring a condition of a structure, comprising:
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a transmitting device that is configured to transmit an interrogation signal to a passive wireless antenna sensor mounted on the structure, wherein the interrogation signal includes frequencies in a frequency range, wherein the frequency range includes a resonant frequency of the passive wireless antenna sensor, wherein the passive wireless antenna sensor is configured such that a change in the condition of the structure will change the resonant frequency; a receiving device that is configured to; receive a backscattered signal, wherein the backscattered signal comprises an antenna backscattered signal from the passive wireless antenna sensor and a structure backscattered signal, wherein and the antenna backscattered signal is modulated by the passive wireless antenna sensor at a modulated frequency; detect a an envelope of the backscattered signal; normalize an envelope; determine a frequency of a normalized envelope that is associated with a reference amplitude; determine a frequency shift based on a difference between frequencies of normalized envelopes at different times at the reference amplitude; and determine the condition of the structure based on the frequency shift. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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18. An system for monitoring a condition of a structure, comprising:
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a transmitting device that is configured to transmit an interrogation signal, wherein the interrogation signal includes frequencies in a frequency range; a network of passive wireless antenna sensors mounted on the structure, wherein each of the wireless antenna sensors has a different resonant frequency, wherein the frequency range includes each of the different resonant frequencies, wherein each of the passive wireless antenna sensors is configured such that a change in the condition of the structure will change the resonant frequency; a receiving device that is configured to receive a backscattered signal, wherein the backscattered signal includes an antenna backscattered signal from at least one of the network of passive wireless antenna sensors and a structure backscattered signal; and a processing device configured to; identify a resonant frequency and a resonant frequency shift for each of the network of passive wireless antenna sensors from the backscattered signal; and determine the condition of the structure based on a resonant frequency shift. - View Dependent Claims (19, 20)
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Specification