Nuclear quadrupole resonance system
First Claim
1. A Nuclear Quadrupole Resonance (NQR) measurement system for detecting at least one material under test (MUT), the system comprising:
- a waveform generator configured to generate a continuous wave (CW) input signal comprising one or more frequencies;
a chamber configured to receive the at least one MUT when carried by a person passing through the chamber;
a probe configured to excite the MUT and then detect NQR RF emissions from the MUT;
a bridge circuit configured to subtract a signal representing the CW input signal in the chamber from a response signal that includes the CW input signal and the NQR RF emissions to generate output NQR RF emissions;
a detector configured to detect the MUT based, at least in part, on the NQR RF emissions; and
a signal generator configured to generate the CW input signal;
wherein the bridge circuit further comprises;
a reference impedance; and
a resistor connected between the signal generator and the reference impedance, wherein the signal representing the CW input signal is generated at a node between the signal generator and the reference impedance.
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Abstract
A system and method for detecting at least one material under test (MUT) is presented. A Nuclear Quadrupole Resonance (NQR) measurement system includes a waveform generator configured to generate a continuous wave (CW) input signal comprising one or more frequencies. An RF shielded chamber receives the at least one MUT that is carried by a person walking through the chamber. A probe within the chamber illuminates the MUT with the CW signal and simultaneously receives possible NQR emissions from the at least one MUT. A bridge circuit is utilized to cancel the strong excitation CW signal from the generator which would otherwise mask the weak NQR emissions from the MUT that are received and detected by the measurement system. A detector can then detect the MUT based, at least in part, on the resonance signal.
89 Citations
18 Claims
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1. A Nuclear Quadrupole Resonance (NQR) measurement system for detecting at least one material under test (MUT), the system comprising:
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a waveform generator configured to generate a continuous wave (CW) input signal comprising one or more frequencies; a chamber configured to receive the at least one MUT when carried by a person passing through the chamber; a probe configured to excite the MUT and then detect NQR RF emissions from the MUT; a bridge circuit configured to subtract a signal representing the CW input signal in the chamber from a response signal that includes the CW input signal and the NQR RF emissions to generate output NQR RF emissions; a detector configured to detect the MUT based, at least in part, on the NQR RF emissions; and a signal generator configured to generate the CW input signal; wherein the bridge circuit further comprises; a reference impedance; and a resistor connected between the signal generator and the reference impedance, wherein the signal representing the CW input signal is generated at a node between the signal generator and the reference impedance. - View Dependent Claims (2, 3, 4, 5)
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6. An NQR measurement system for detecting a material comprising:
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an NQR measurement chamber that is shielded from external RF noises and that is configured to receive the material, wherein an NQR signal is emitted by the material in response to a CW excitation signal transmitted into the chamber and the material; a subtractor configured to generate a difference signal by subtracting a reference signal from response signal to generate a difference signal, wherein the reference signal represents a CW signal transmitted into the chamber when the chamber is lacking the material; and a detector configured to detect the material is present in the chamber based, at least in part on the difference signal. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method of detection using Nuclear Quadrupole Resonance (NQR) comprising:
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inputting a continuous wave (CW) signal into an NQR chamber; determining a reference signal representative of the CW signal in the chamber without a material under test (MUT) in the chamber; receiving a response signal from the chamber that includes the CW signal and at least one frequency responsive to the MUT; removing the reference signal from the response signal to generate a difference signal; and detecting the material based, at least in part, on whether the difference signal exceeding a threshold value; and periodically updating a reference impedance value with a new value, wherein the reference signal is based, at least in part, on the reference impedance value. - View Dependent Claims (18)
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Specification