US6291994B1
Expired / Lapsed
US
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Active Q-damping sub-system using nuclear quadrupole resonance and nuclear magnetic resonance for improved contraband detection
Assignee: Quantum Magnetics Inc
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Filing: 2000-01-14
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Granted: 2001-09-18
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Expires: 2020-01-14
Abstract
Abstract A Q-damping subsystem for either an NQR or NMR contraband detection receiver for effectively reducing the dead time and increasing sensitivity of the contraband detection system. The invention acts as an addition to the standard transmit circuits of NQR and NMR based scanners and spectrometers. The active Q-damping devices require additional circuitry for an NQR/NMR detection receiver and a programming for the control thereof. Typically, the detection receiver generates a high-voltage RF pulse on the order of 200-1000 V with normal operation of 100-300 microseconds in length to provide sufficient magnetic field characteristics to perturb the precessing nuclei. The NQR or NMR detection receiver electronics are very sensitive and have to detect a very weak nuclear induction pulse signal that is in the nano/micro-volt range. The invention encompasses several embodiments of the detection receiver with the Q-damping subsystem which include: a transformer coupled resistive damping circuit; an inductively coupled resistive damping circuit; a shunt capacitor/resistor damping circuit; a grounded shunt capacitor/resistor damping circuit; a common mode choke transient suppression damping circuit; a multi-stage Q-damping circuit; and a full-wave Q-damping circuit.
Inventors
- 👤 Yong-Wah Kim
- 👤 Erik E. Magnuson
- 👤 David C. Skvoretz
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 18:18
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/441; G01N; G01N24/00; G01N24/08; G01N24/084
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
190 words
A quality factor damping (Q-damping) subsystem for use in a system for detecting substances in a specimen placed in a cavity of the system by means of nuclear quadrupole resonance (NQR) or nuclear magnetic resonance (NMR), the subsystem comprising: a sequence controller having means for providing timing and programming pulses to the system; a variable frequency RF source to provide pulsed RF excitation at predetermined frequencies generally corresponding to resonant frequencies of the specimen; an RF coil shaped and configured to receive the specimen, the RF signal from the RF source being applied to the specimen through the RF coil, the RF coil also functioning as a pickup coil of NQR/NMR signals from the specimen and providing an output signal; and means for Q-damping the RF coil, which includes an isolated Q-damping coil that is controlled by the sequence controller, the sequence controller further including means for detecting a short spin-spin relaxation time (T 2 ) of the specimen compared to the unmodified receiver dead-time, thereby maximizing RF coil sensitivity and minimizing dead time of the output signal for increasing the signal sampling averaging provided by the short-spin relaxation time.
Claim 2
Dependent Claim
190 words
A quality factor damping (Q-damping) subsystem for use in a system for detecting substances in a specimen placed in a cavity of the system by means of nuclear quadrupole resonance (NQR) or nuclear magnetic resonance (NMR), the subsystem comprising: a sequence controller having means for providing timing and programming pulses to the system; a variable frequency RF source to provide pulsed RF excitation at predetermined frequencies generally corresponding to resonant frequencies of the specimen; an RF coil shaped and configured to receive the specimen, the RF signal from the RF source being applied to the specimen through the RF coil, the RF coil also functioning as a pickup coil of NQR/NMR signals from the specimen and providing an output signal; and means for Q-damping the RF coil, which includes an isolated Q-damping coil that is controlled by the sequence controller, the sequence controller further including means for detecting a short spin-spin relaxation time (T 2 ) of the specimen compared to the unmodified receiver dead-time, thereby maximizing RF coil sensitivity and minimizing dead time of the output signal for increasing the signal sampling averaging provided by the short-spin relaxation time.
Claim 3
Dependent Claim
21 words
The subsystem recited in claim 1 , wherein the means for Q-damping the RF coil comprises a transformer coupled circuit network.
Claim 4
Dependent Claim
21 words
The sub-system recited in claim 1 , wherein the means for Q-damping the RF coil comprises an inductively coupled circuit network.
Claim 5
Dependent Claim
21 words
The sub-system recited in claim 1 , wherein the means for Q-damping the RF coil comprises a shunt capacitor-resistor circuit network.
Claim 6
Dependent Claim
47 words
The sub-system recited in claim 4 , wherein the shunt capacitor-resistor circuit network includes a subnetwork selected from the group consisting of a) a series connected resistor and capacitor, b) a parallel connected resistor and capacitor, and c) a series-parallel combination consisting of resistor and capacitor components.
Claim 7
Dependent Claim
22 words
The sub-system recited in claim 1 , wherein the means for Q-damping the RF coil comprises a grounded shunt capacitor-resistor circuit network.
Claim 8
Dependent Claim
51 words
The sub-system recited in claim 6 , wherein the grounded shunt capacitor-resistor circuit network includes two subnetworks, each subnetwork is selected from the group consisting of a) a series connected resistor and capacitor, b) a parallel connected resistor and capacitor, and c) a series-parallel combination consisting of resistor and capacitor components.
Claim 9
Dependent Claim
24 words
The sub-system recited in claim 1 , wherein the means for Q-damping the RF coil comprises a common mode choke transient suppression circuit network.
Claim 10
Dependent Claim
21 words
The sub-system recited in claim 1 , wherein the means for Q-damping the RF coil comprises a multi-stage Q-damping circuit network.
Claim 11
Dependent Claim
55 words
The sub-system recited in claim 9 , wherein the multi-stage Q-damping circuit network includes at least two subnetworks, each subnetwork is selected from the group consisting of a) a series connected resistor and capacitor, b) a parallel connected resistor and capacitor; c) a series-parallel combination consisting of resistor and capacitor components; and d) phase-inverted pulse.
Claim 12
Dependent Claim
23 words
The sub-system recited in claim 9 , wherein the multi-stage Q-damping circuit network includes two subnetworks having means for tuning at different frequencies.
Claim 13
Dependent Claim
21 words
The sub-system recited in claim 1 , wherein the means for Q-damping the RF coil comprises a full-wave Q-damping circuit network.
Claim 14
Dependent Claim
49 words
The sub-system recited in claim 12 , wherein the full-wave Q-damping circuit network includes at least one subnetwork selected from the group consisting of a) a series connected resistor and capacitor, b) a parallel connected resistor and capacitor, and c) a series-parallel combination consisting of resistor and capacitor components.
Claim 15
Dependent Claim
26 words
The sub-system recited in claim 1 , and further comprising means for auto-tuning the system at multiple tuned frequencies for detecting different substances in the specimen.
Claim 16
Dependent Claim
23 words
The sub-system recited in claim 11 , wherein the multi-stage Q-damping circuit network includes a phase-inverted pulse circuit as one of the networks.
Claim 17
Dependent Claim
34 words
The sub-system recited in claim 4 , wherein the sequence controller generates control signals to a diode recovery time circuit, which in turn controls switching activity of the means for Q-damping the RF coil.
Claim 18
Dependent Claim
34 words
The sub-system recited in claim 6 , wherein the sequence controller generates control signals to a diode recovery time circuit, which in turn controls switching activity of the means for Q-damping the RF coil.
Claim 19
Dependent Claim
34 words
The sub-system recited in claim 8 , wherein the sequence controller generates control signals to a diode recovery time circuit, which in turn controls switching activity of the means for Q-damping the RF coil.
Claim 20
Dependent Claim
34 words
The sub-system recited in claim 9 , wherein the sequence controller generates control signals to a diode recovery time circuit, which in turn controls switching activity of the means for Q-damping the RF coil.
Claim 21
Dependent Claim
34 words
The sub-system recited in claim 12 , wherein the sequence controller generates control signals to a diode recovery time circuit, which in turn controls switching activity of the means for Q-damping the RF coil.
Claim 22
Dependent Claim
34 words
The sub-system recited in claim 15 , wherein the sequence controller generates control signals to a diode recovery time circuit, which in turn controls switching activity of the means for Q-damping the RF coil.
Claim 23
Dependent Claim
55 words
The sub-system recited in claim 1 , wherein the sequence controller generates control signals to a diode recovery time circuit, which in turn controls switching activity of the means for Q-damping the RF coil, the diode recovery circuit has two switching devices wherein the switching devices each connect to outputs from a y-connected resistor device.
Claim 24
Dependent Claim
33 words
The sub-system recited in claim 1 , wherein a lower dead time leads to increased effective characteristic decay time (T 2eff ), which increases the number of signal samples that can be averaged.
Claim 25
Independent Claim
157 words
A method for quality-factor (Q)-damping (Q-damping) an RF coil in a system for detecting target substances in a specimen by means of nuclear quadrupole resonance (NQR) or nuclear magnetic resonance (NMR) for improving the signal-to-noise ratio of the system and minimizing dead-time of a received RF coil signal, the method comprising the steps of: inserting the specimen within a cavity formed in the RF coil; providing RF pulses of predetermined frequencies to the RF coil for predetermined time; and selectively changing the quality factor “Q” of a circuit containing the RF coil to Q-damp the RF coil wherein changing of the Q-factor occurs after each RF pulse is generated and removed as soon as the ring down of a received pulse has decayed below a predetermined level wherein a short spin-spin relaxation time (T 2 ) of a received signal from the specimen occurs compared to the receiver dead-time thereby increasing the sampling signal to be averaged.
Claim 26
Independent Claim
157 words
A method for quality-factor (Q)-damping (Q-damping) an RF coil in a system for detecting target substances in a specimen by means of nuclear quadrupole resonance (NQR) or nuclear magnetic resonance (NMR) for improving the signal-to-noise ratio of the system and minimizing dead-time of a received RF coil signal, the method comprising the steps of: inserting the specimen within a cavity formed in the RF coil; providing RF pulses of predetermined frequencies to the RF coil for predetermined time; and selectively changing the quality factor “Q” of a circuit containing the RF coil to Q-damp the RF coil wherein changing of the Q-factor occurs after each RF pulse is generated and removed as soon as the ring down of a received pulse has decayed below a predetermined level wherein a short spin-spin relaxation time (T 2 ) of a received signal from the specimen occurs compared to the receiver dead-time thereby increasing the sampling signal to be averaged.
Claim 27
Dependent Claim
56 words
The method recited in claim 24 , wherein the system includes a controller that provides an algorithm for Q-damping of the RF coil, the Q-damping state being accomplished through a plurality of active switching components to which signals are applied from the controller, the switching components form part of a means for Q-damping the RF coil.
Claim 28
Dependent Claim
34 words
The method recited in claim 25 , wherein the algorithm includes steps for controlling the means for Q-damping the RF coil comprising a multi-stage Q-damping circuit network that incorporates a phase inverted pulse design.
Claim 29
Dependent Claim
39 words
The method recited in claim 25 , wherein the algorithm includes steps for controlling the means for Q-damping the RF coil comprising a multi-stage Q-damping circuit network which includes two subnetworks having means for tuning at different Q-damping frequencies.
Claim 30
Dependent Claim
83 words
The method recited in claim 25 , wherein the algorithm includes steps for controlling the means for Q-damping the RF coil further comprising a Q-switch that supplements the means for Q-damping the RF coil, wherein the algorithm includes steps for allowing the Q of the RF coil to be switched during a transmit pulse event, whereby the Q-switch lowers the Q of the RF coil during transmit to decrease pulse ring up time and reduce ring down time of the means for Q-damping.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2004-09-17 | 2005-03-19 | 2005-09-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2008-09-17 | 2009-03-19 | 2009-09-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2012-09-17 | 2013-03-19 | 2013-09-18 | $7700.00 | Window Closed / Lapsed |