Quadrature processed LIDAR system
First Claim
1. A method of generating in-quadrature signals, the method comprising:
- receiving a Doppler frequency-shifted signal;
phase shifting the Doppler frequency-shifted signal generating thereby a phase-shifted Doppler frequency-shifted signal and an unphase-shifted Doppler frequency-shifted signal;
receiving a local oscillator signal;
phase shifting the local oscillator signal generating thereby a phase-shifted local oscillator signal and an unphase-shifted local oscillator signal;
further phase shifting the local oscillator signal;
mixing the phase-shifted Doppler frequency-shifted signal and the further phase-shifted local oscillator signal generating thereby a signal that includes the phase-shifted Doppler frequency-shifted signal and the further phase-shifted local oscillator signal; and
mixing the unphase-shifted Doppler frequency-shifted signal and the unphase-shifted local oscillator signal generating thereby a signal that includes the unphase-shifted local oscillator signal and the phase-shifted Doppler frequency shifted signal.
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Abstract
A method of generating in-quadrature signals is disclosed. The method comprises phase shifting a Doppler frequency-shifted signal; phase shifting a local oscillator signal; mixing the phase shifted Doppler frequency-shifted signal and the phase-shifted local oscillator signal generating thereby a signal which includes the phase-shifted Doppler frequency-shifted signal and a further phase-shifted local oscillator signal; and mixing the unphase-shifted Doppler frequency-shifted signal and the unphase-shifted local oscillator signal generating thereby a signal which includes the unphase-shifted local oscillator signal and a further phase-shifted Doppler frequency-shifted signal. A method of determining the velocity of an object is also disclosed. The method comprises receiving a Doppler frequency-shifted signal reflected or backscattered from the object; generating a local oscillator signal; based upon the received Doppler frequency-shifted signal and the local oscillator signal, generating an in-phase signal; based upon the received Doppler frequency-shifted signal and the local oscillator signal generating an in-quadrature signal; summing the in-phase signal and the in-quadrature signal; and transforming the summation of the in-phase signal and the in-quadrature signal. A lidar is disclosed comprising an optical system for transmitting an output signal to an object and receiving thereby a Doppler frequency-shifted signal reflected or backscattered from the object; a signal mixing assembly receptive of the Doppler frequency-shifted signal and a local oscillator signal generating thereby an in-phase signal and an in-quadrature signal; and a signal transformer for transforming the in-phase signal and an in-quadrature signals. A signal mixing system is disclosed comprising an array of signal couplers receptive of a Doppler frequency-shifted signal and a local oscillator signal generating thereby an in-phase signal which includes the unphase-shifted local oscillator signal and a phase-shifted Doppler frequency-shifted signal and an in-quadrature signal which includes the phase-shifted Doppler frequency-shifted signal and a further phase-shifted local oscillator signal; and a plurality of signal detectors receptive of the in-phase and in-quadrature signals.
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Citations
30 Claims
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1. A method of generating in-quadrature signals, the method comprising:
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receiving a Doppler frequency-shifted signal;
phase shifting the Doppler frequency-shifted signal generating thereby a phase-shifted Doppler frequency-shifted signal and an unphase-shifted Doppler frequency-shifted signal;
receiving a local oscillator signal;
phase shifting the local oscillator signal generating thereby a phase-shifted local oscillator signal and an unphase-shifted local oscillator signal;
further phase shifting the local oscillator signal;
mixing the phase-shifted Doppler frequency-shifted signal and the further phase-shifted local oscillator signal generating thereby a signal that includes the phase-shifted Doppler frequency-shifted signal and the further phase-shifted local oscillator signal; and
mixing the unphase-shifted Doppler frequency-shifted signal and the unphase-shifted local oscillator signal generating thereby a signal that includes the unphase-shifted local oscillator signal and the phase-shifted Doppler frequency shifted signal.
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2. A method of determining the sign of the velocity vector associated with the velocity of an object, the method comprising:
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receiving a Doppler frequency-shifted signal reflected or backscattered from the object;
generating a local oscillator signal;
based upon the received Doppler frequency-shifted signal and the local oscillator signal, generating an in-phase signal;
based upon the received Doppler frequency-shifted signal and the local oscillator signal, generating an in-quadrature signal;
summing the in-phase signal and the in-quadrature signal;
Fourier transforming the summation of the in-phase signal and the in-quadrature signal; and
yielding a power spectral density from the Fourier transform representative of the sign of the velocity vector.
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3. A lidar comprising:
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an optical system for transmitting an output signal to an object and receiving thereby a Doppler frequency-shifted signal reflected or backscattered from the object;
wherein the optical system comprises;
a laser generating a laser beam at a prescribed wavelength, a signal coupler receptive of the laser beam and adapted to divide the laser beam into a local oscillator signal and a coupler output signal, a circulator receptive of the coupler output signal and adapted to provide a circulator output signal to the object, to receive the Doppler frequency-shifted signal from the object, and to output the Doppler frequency-shifted signal, and a telescope receptive of the circulator output signal and adapted to direct the circulator output signal to the object and to receive the Doppler frequency-shifted signal from the object, wherein the circulator is adapted to receive the Doppler frequency-shifted signal from the telescope;
a signal mixing assembly including;
a plurality of signal phase shifting devices being adapted to receive the Doppler frequency-shifted signal from the circulator and a local oscillator signal from the signal coupler, and being adapted to generate an in-phase signal, said in-phase signal including an unphase-shifted local oscillator signal, and an in-quadrature signal, said in-quadrature signal including a phase-shifted Doppler frequency-shifted signal and a further phase-shifted local oscillator signal, the signal mixing assembly including a waveguide system adapted to guide the laser beam, the local oscillator signal, the various output signals and the Doppler frequency-shifted signal therealong; and
a signal processing system adapted to Fourier transform the in-phase and in-quadrature signals. - View Dependent Claims (4, 5, 6, 7, 8, 9)
the first directional coupler is adapted to receive the local oscillator signal and to generate an unphase-shifted local oscillator signal and a first phase-shifted local oscillator signal;
the second directional coupler is adapted to receive the first phase-shifted local oscillator signal and to generate a further phase-shifted local oscillator;
the third directional coupler is adapted to receive the Doppler frequency-shifted signal and to generate an unphase-shifted Doppler frequency-shifted signal and a phase-shifted Doppler frequency-shifted signal;
the fourth directional coupler is adapted to receive the phase-shifted Doppler frequency-shifted signal and the further phase-shifted local oscillator signal and to generate the in-quadrature signal; and
the fifth directional coupler is adapted to receive the unphase-shifted Doppler frequency-shifted signal and the unphase-shifted local oscillator signal and to generate the in-phase signal.
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6. The signal mixing assembly as set forth in claim 3 further comprising a plurality of signal detectors adapted to receive the in-phase and in-quadrature signals and adapted to generate output electrical signals indicative of the intensities of the in-phase and in-quadrature signals.
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7. The lidar as set forth in claim 3 wherein the signal transformer comprises a Fourier transformer receptive of the in-phase signal and in-quadrature signal and operative thereby to Fourier transform the complex sum of the in-phase signal and in-quadrature signal.
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8. The lidar as set forth in claim 3 further comprising a signal modulator adapted to receive the local oscillator signal and to shift the local oscillator signal to a prescribed frequency.
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9. The lidar as set forth in claim 8 wherein the modulator comprises an acousto-optic modulator.
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10. A signal mixing system comprising:
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a plurality of signal couplers in signal communication by a plurality of waveguides being adapted to receive a Doppler frequency-shifted signal, a local oscillator signal, a phase-shifted Doppler frequency-shifted signal, a phase-shifted local oscillator signal, and a further phase-shifted local oscillator signal, and being adapted to generate an in-phase signal that includes an unphase-shifted local oscillator signal and the phase-shifted Doppler frequency-shifted signals, and an in-quadrature signal that includes the phase-shifted Doppler frequency-shifted signal and the further phase-shifted local oscillator signal; and
a plurality of signal detectors adapted to receive the in-phase and in-quadrature signals.
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11. A coherent optical system comprising:
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an optical system for transmitting an output signal to an object and receiving thereby a Doppler frequency-shifted signal reflected or backscattered from the object;
a signal mixing assembly receptive of the Doppler frequency-shifted signal and a local oscillator signal generating thereby an in-phase signal and an in-quadrature signal, the signal mixing assembly comprising;
a plurality of signal couplers adapted to receive a Doppler frequency-shifted signal, a local oscillator signal, a phase-shifted Doppler frequency-shifted signal, a phase-shifted local oscillator signal, and a further phase-shifted local oscillator signal, and adapted to generate the in-phase signal, said in-phase signal including an unphase-shifted local oscillator signal and the phase-shifted Doppler frequency-shifted signal, and the in-quadrature signal, said in-quadrature signal including the phase-shifted Doppler frequency-shifted signal and the further phase-shifted local oscillator signal, and a plurality of signal detectors adapted to receive the in-phase and in-quadrature signals; and
a signal processing system adapted to Fourier transform the in-phase and in-quadrature signals.
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12. A signal mixing system comprising:
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an array of signal phase shifting devices adapted to receive a Doppler frequency-shifted signal and a local oscillator signal, and adapted to generate thereby;
an in-phase signal that includes an unphase shifted local oscillator signal and a phase shifted Doppler frequency-shifted signal; and
an in-quadrature signal that includes the phase shifted Doppler frequency-shifted signal and a further phase-shifted local oscillator signal;
wherein the array of phase shifting devices comprise a plurality of single mode directional couplers in signal communication by a plurality of waveguides. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
the first directional coupler is adapted to receive the local oscillator signal and to generate an unphase-shifted local oscillator signal and a first phase-shifted local oscillator signal;
the second directional coupler is adapted to receive the first phase-shifted local oscillator signal and to generate a further phase-shifted local oscillator;
the third directional coupler is adapted to receive the Doppler frequency-shifted signal and to generate an unphase-shifted Doppler frequency-shifted signal and a phase-shifted Doppler frequency-shifted signal;
the fourth directional coupler is adapted to receive the phase-shifted Doppler frequency-shifted signal and the further phase-shifted local oscillator signal and to generate the in-quadrature signal; and
the fifth directional coupler is adapted to receive the unphase-shifted Doppler frequency-shifted signal and the unphase-shifted local oscillator signal and to generate the in-phase signal.
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15. The signal mixing system as set forth in claim 12 further comprising a plurality of signal detectors adapted to receive the in-phase and in-quadrature signals and adapted to generate output electrical signals indicative of the intensities of the in-phase and in-quadrature signals.
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16. The signal mixing system as set forth in claim 14 wherein the phase-shifted local oscillator signal and the unphase-shifted local oscillator signal have an amplitude ratio of 2:
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17. The signal mixing system as set forth in claim 14 wherein the second directional coupler comprises a quarter wave retarder.
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18. The signal mixing system as set forth in claim 14 further comprising:
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a first amplifier receptive of the Doppler frequency-shifted signal for amplification thereof;
a second amplifier receptive of the in-phase signal for the amplification thereof; and
a third amplifier receptive of the in-quadrature signal for amplification thereof.
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19. The signal mixing system as set forth in claim 18 wherein the first second and third amplifiers comprise rare earth doped fiber amplifers.
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20. The signal mixing system as set forth in claim 14 further comprising:
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a first isolator receptive of the Doppler frequency-shifted signal for isolation thereof;
a second isolator receptive of the in-phase signal for the isolation thereof; and
a third isolator receptive of the in-quadrature signal for isolation thereof.
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21. A method of generating in-phase and in-quadrature lidar signals, the method comprising:
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phase-shifting the Doppler frequency-shifted signal to generate a phase-shifted Doppler frequency-shifted signal and an unphase-shifted Doppler frequency-shifted signal;
phase-shifting the local oscillator signal to generate a phase-shifted local oscillator signal and an unphase-shifted local oscillator signal;
further phase-shifting the phase-shifted local oscillator signal to generate a further phase-shifted local oscillator signal;
mixing the phase-shifted Doppler frequency-shifted signal and the further phase-shifted local oscillator signal generating thereby an in-quadrature signal that includes the phase-shifted Doppler frequency-shifted signal and the further phase-shifted local oscillator signal; and
mixing the unphase-shifted Doppler frequency-shifted signal and the unphase-shifted local oscillator signal generating thereby an in-phase signal that includes the unphase-shifted local oscillator signal and the unphase-shifted Doppler frequency-shifted signal. - View Dependent Claims (22, 23)
phase-shifting the local oscillator signal comprises phase-shifting the local oscillator signal by ninety degrees; and
further phase-shifting the local oscillator signal comprises phase-shifting the local oscillator signal by one hundred and eighty degrees.
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24. A method of determining the velocity of an object, the method comprising:
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generating an output signal directed at the object;
receiving a Doppler frequency-shifted signal reflected or backscattered from the object;
generating a local oscillator signal;
based upon the received Doppler frequency-shifted signal and the local oscillator signal, generating an in-phase signal;
based upon the received Doppler frequency-shifted signal and the local oscillator signal, generating an in-quadrature signal;
summing the in-phase signal and the in-quadrature signal;
Fourier transforming the summation of the in-phase signal and the in-quadrature signal; and
yielding a computational result from the Fourier transform representative of both the velocity magnitude and the velocity direction. - View Dependent Claims (25, 26, 27, 28, 29, 30)
phase-shifting the Doppler frequency-shifted signal;
phase-shifting the local oscillator signal;
further phase-shifting the local oscillator signal;
mixing the phase-shifted Doppler frequency-shifted signal and the further phase-shifted local oscillator signal generating thereby an in-quadrature signal that is ninety degrees out of phase with the in-phase signal.
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29. The method as set forth in claim 28 wherein phase shifting the Doppler frequency-shifted signal comprises phase shifting the Doppler frequency-shifted signal by ninety degrees.
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30. The method as set forth in claim 28 wherein further phase-shifting the local oscillator signal comprises phase-shifting the local oscillator signal by one hundred and eighty degrees.
Specification