Quadrature processed lidar system

• US 20020105632A1
• Filed: 09/20/2001
• Published: 08/08/2002
• Est. Priority Date: 09/22/2000
• Status: Active Grant

• Current Assignee: Virginia Tech Intellectual Properties, Inc.
• Original Assignee: Virginia Tech Intellectual Properties, Inc.
• Inventors: Holton, Carvel E.
• Granted Patent: US 6,608,669 B2
• Time in Patent Office: Days
• US Class Current: 356/28.5
• CPC Class Codes: G01S 17/58 Velocity or trajectory determination systems; Sense-of-movement determination systems
• CPC Class Codes: G01S 7/4818 using optical fibres
• CPC Class Codes: G01S 7/491 Details of non-pulse systems
• CPC Class Codes: G01S 7/4917 superposing optical signals in a photodetector, e.g. optical heterodyne detection
• CPC Class Codes: H04B 10/63 Homodyne , i.e. coherent receivers where the local oscillator is locked in frequency and phase to the carrier signal
• CPC Class Codes: H04B 10/64 Heterodyne , i.e. coherent receivers where, after the opto-electronic conversion, an electrical signal at an intermediate frequency [IF] is obtained
• CPC Class Codes: H04L 27/1525 using quadrature demodulation
• CPC Class Codes: H04L 27/206 using a pair of orthogonal carriers, e.g. quadrature carriers
• CPC Class Codes: H04L 27/26 Systems using multi-frequency codes H04L27/32 takes precedence

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 of 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.

Claims

1. A method of generating in-quadrature signals, the method comprising:

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.

2. A method of determining the velocity of an object, the method comprising:

receiving a Doppler frequency-shifted signal reflected of 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.

3. A lidar 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.

4. A signal mixing system 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.

5. A coherent optical system 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.