Patent US6388739B1 successfully refreshed from Google Patents.
US6388739B1
Expired / Lapsed
US
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Self-referencing microdoppler ladar receiver and associated detection method
Assignee: Boeing Co
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Filing: 2001-01-18
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Granted: 2002-05-14
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Expires: 2021-01-18
Abstract
Abstract A self-referencing microdoppler ladar receiver is provided for detecting the vibration of a target based upon an analysis of backscattered signals without a local reference derived from the transmitter. The self-referencing microdoppler ladar receiver includes a frequency shifter for receiving a backscattered signal from the target and for controllably shifting the frequency of the backscattered signal. The self-referencing microdoppler ladar receiver also includes an interferometer, such as a Mach Zender interferometer, for directing portions of the frequency shifted signals along first and second paths of unequal length and for combining the portions of the frequency shifted signals to produce first and second output signals. The self-referencing microdoppler ladar receiver also includes a signal processor for providing a feedback signal to control the frequency shifter based upon differences in the respective power levels of the first and second output signals. In particular, the signal processor provides the feedback signal to control the frequency shifter in order to drive the interferometer towards quadrature. Since the feedback signal provided by the signal processor is proportional to the instantaneous frequency of the backscattered signal which, in turn, includes frequency contributions due to the vibrational velocity of the target, the vibration of the target is detectable without locally referencing the primary laser beam generated by the transmitter. A microdoppler ladar system including a self-referencing microdoppler ladar receiver and an associated detection method are also provided.
Inventors
- 👤 Robert Rex Rice
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 20:29
CPC Classifications
G; G01; G01S; G01S7/00; G01S7/48; G01S7/481; G01S7/4818; G01H; G01H9/00; G01P; G01P3/00; G01P3/36; G01P3/366; G01S17/00; G01S17/003; G01S17/02; G01S17/50; G01S17/58; G01S7/4802; G01S7/491; G01S7/4912; G01S7/4917
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
153 words
A self-referencing microdoppler ladar receiver comprising: a frequency shifter for receiving a backscattered signal from a target that has been illuminated by a transmitter and for controllably shifting the frequency of the backscattered signal; an interferometer for directing portions of the frequency shifted signal along first and second paths of unequal length and for combining the portions of the frequency shifted signal to produce first and second output signals; and a signal processor for providing a feedback signal to control said frequency shifter based upon differences in the respective power levels of the first and second output signals such that said interferometer is driven towards quadrature, wherein the feedback signal provided by said signal processor is proportional to an instantaneous frequency of the backscattered signal including frequency contributions due to a vibrational velocity of the target such that the vibration of the target is detectable without a local reference derived from the transmitter.
Claim 2
Dependent Claim
153 words
A self-referencing microdoppler ladar receiver comprising: a frequency shifter for receiving a backscattered signal from a target that has been illuminated by a transmitter and for controllably shifting the frequency of the backscattered signal; an interferometer for directing portions of the frequency shifted signal along first and second paths of unequal length and for combining the portions of the frequency shifted signal to produce first and second output signals; and a signal processor for providing a feedback signal to control said frequency shifter based upon differences in the respective power levels of the first and second output signals such that said interferometer is driven towards quadrature, wherein the feedback signal provided by said signal processor is proportional to an instantaneous frequency of the backscattered signal including frequency contributions due to a vibrational velocity of the target such that the vibration of the target is detectable without a local reference derived from the transmitter.
Claim 3
Dependent Claim
44 words
A self-referencing microdoppler ladar receiver according to claim 1 wherein the first path of said interferometer comprises a delay loop for delaying a respective portion of the frequency shifted signal by a predetermined time relative to the other portion of the frequency shifted signal.
Claim 4
Dependent Claim
39 words
A self-referencing microdoppler ladar receiver according to claim 1 wherein said interferometer comprises a coupler for combining the portions of the frequency shifted signal following propagation along the first and second paths to produce first and second output signals.
Claim 5
Dependent Claim
17 words
A self-referencing microdoppler ladar receiver according to claim 1 wherein said interferometer comprises a Mach Zender interferometer.
Claim 6
Dependent Claim
71 words
A self-referencing microdoppler ladar receiver according to claim 1 further comprising a balanced coherent receiver disposed between said interferometer and said signal processor, said balanced coherent receiver comprising: first and second detectors for detecting the first and second output signals, respectively; and a differential amplifier for combining outputs of said first and second detectors to thereby amplify the differences in the respective power levels of the first and second output signals.
Claim 7
Dependent Claim
27 words
A self-referencing microdoppler ladar receiver according to claim 1 wherein said frequency shifter comprises an acoustooptic frequency shifter for shifting the frequency spectrum of the backscattered signals.
Claim 8
Dependent Claim
29 words
A self-referencing microdoppler ladar receiver according to claim 1 further comprising a preamplifier for amplifying the backscattered signal prior to providing the amplified backscattered signal to said frequency shifter.
Claim 9
Dependent Claim
18 words
A self-referencing microdoppler ladar receiver according to claim 1 wherein said signal processor comprises a voltage controlled oscillator.
Claim 10
Dependent Claim
140 words
A microdoppler ladar system comprising: a transmitter for producing signals to illuminate a target; and a self-referencing receiver for receiving a backscattered signal from the target, said self-referencing receiver comprising: a frequency shifter for controllably shifting the frequency of the backscattered signal; an unequal path length interferometer for receiving the frequency shifted signal and for producing first and second output signals; and a signal processor for providing a feedback signal to control said frequency shifter based upon differences in the respective power levels of the first and second output signals such that said interferometer is driven towards quadrature, wherein the feedback signal is proportional to an instantaneous frequency of the backscattered signal including frequency contributors due to a vibrational velocity of the target such that the vibration of the target is detectable without a local reference derived from said transmitter.
Claim 11
Dependent Claim
140 words
A microdoppler ladar system comprising: a transmitter for producing signals to illuminate a target; and a self-referencing receiver for receiving a backscattered signal from the target, said self-referencing receiver comprising: a frequency shifter for controllably shifting the frequency of the backscattered signal; an unequal path length interferometer for receiving the frequency shifted signal and for producing first and second output signals; and a signal processor for providing a feedback signal to control said frequency shifter based upon differences in the respective power levels of the first and second output signals such that said interferometer is driven towards quadrature, wherein the feedback signal is proportional to an instantaneous frequency of the backscattered signal including frequency contributors due to a vibrational velocity of the target such that the vibration of the target is detectable without a local reference derived from said transmitter.
Claim 12
Dependent Claim
52 words
A microdoppler ladar system according to claim 9 for detecting the target at a distance from said transmitter, wherein said transmitter is selected such that the signals produced thereby have a coherence length less than the cumulative distance from said transmitter to the target and from the target to said self-referencing receiver.
Claim 13
Dependent Claim
15 words
A microdoppler ladar system according to claim 9 wherein said transmitter comprises a master oscillator.
Claim 14
Dependent Claim
63 words
A microdoppler ladar system according to claim 9 wherein said interferometer comprises first and second paths having unequal path lengths for receiving portions of the frequency shifted signal, wherein the first path of said interferometer comprises a delay loop for delaying a respective portion of the frequency shifted signal by a predetermined time relative to the other portion of the frequency shifted signal.
Claim 15
Dependent Claim
16 words
A microdoppler ladar system according to claim 9 wherein said interferometer comprises a Mach Zender interferometer.
Claim 16
Dependent Claim
74 words
A microdoppler ladar system according to claim 9 wherein said self-referencing receiver further comprises a balanced coherent receiver disposed between said interferometer and said signal processor, said balanced coherent receiver comprising: first and second detectors for detecting the first and second output signals, respectively; and a differential amplifier for combining outputs of said first and second detectors to thereby amplify the differences in the respective power levels of the first and second output signals.
Claim 17
Dependent Claim
26 words
A microdoppler ladar system according to claim 9 wherein said frequency shifter comprises an acoustooptic frequency shifter for shifting the frequency spectrum of the backscattered signals.
Claim 18
Dependent Claim
18 words
A microdoppler ladar system according to claim 9 wherein said self-referencing receiver is positioned remote from said transmitter.
Claim 19
Dependent Claim
35 words
A microdoppler ladar system according to claim 16 further comprising a plurality of self-referencing receivers disposed at respective positions such that each self-referencing receiver is remote from said transmitter and from the other self-referencing receivers.
Claim 20
Independent Claim
160 words
A method of detecting vibration of a target without a local reference derived from a transmitter that illuminates the target, the method comprising: controllably shifting the frequency of a signal backscattered from the target; directing portions of the frequency shifted signal along first and second paths defined by an interferometer, wherein the first and second paths are of unequal length; combining the portions of the frequency shifted signal to produce first and second output signals; and providing a feedback signal to control the frequency shift imparted upon the backscattered signal, wherein the feedback signal is based upon differences in the respective power levels of the first and second output signals such that the interferometer is driven towards quadrature, wherein the feedback signal is proportional to an instantaneous frequency of the backscattered signal including frequency contributions due to a vibrational velocity of the target such that the vibration of the target is detectable without a local reference derived from the transmitter.
Claim 21
Independent Claim
160 words
A method of detecting vibration of a target without a local reference derived from a transmitter that illuminates the target, the method comprising: controllably shifting the frequency of a signal backscattered from the target; directing portions of the frequency shifted signal along first and second paths defined by an interferometer, wherein the first and second paths are of unequal length; combining the portions of the frequency shifted signal to produce first and second output signals; and providing a feedback signal to control the frequency shift imparted upon the backscattered signal, wherein the feedback signal is based upon differences in the respective power levels of the first and second output signals such that the interferometer is driven towards quadrature, wherein the feedback signal is proportional to an instantaneous frequency of the backscattered signal including frequency contributions due to a vibrational velocity of the target such that the vibration of the target is detectable without a local reference derived from the transmitter.
Claim 22
Dependent Claim
53 words
A method according to claim 18 wherein directing portions of the frequency shifted signal along the first and second paths comprises delaying the portion of the frequency shifted signal propagating along the first path by a predetermined time relative to the other portion of the frequency shifted signal propagating along the second path.
Claim 23
Dependent Claim
22 words
A method according to claim 18 further comprising separately detecting the first and second output signals prior to providing the feedback signal.
Claim 24
Dependent Claim
23 words
A method according to claim 20 further comprising amplifying differences between the first and second output signals prior to providing the feedback signal.
Claim 25
Dependent Claim
23 words
A method according to claim 18 further comprising amplifying the backscattered signal prior to controllably shifting the frequency of the amplified backscattered signal.
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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) | 2005-05-13 | 2005-11-12 | 2006-05-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2009-05-13 | 2009-11-12 | 2010-05-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2013-05-13 | 2013-11-12 | 2014-05-14 | $7700.00 | Window Closed / Lapsed |