Honeywell International Inc.

Norman Gerard Tarleton

Lee Kevin Strandjord

Glen Aaron Sanders

Chuck Croker

Marc Smiciklas

Darryl Busch

Gregory W Keith

Derek Mead

David A Doheny

Stephan Enzone

Tiequn Qiu

Steven J Sanders

Douglas Edward Smith

Jeffrey Earl Lewis

Austin Taranta

Sorin Mosor

Lower noise and complexity techniques are disclosed for compensating for time varying phase changes in fiber optics in a resonant fiber optic gyroscope (RFOG). Orthogonal components derived from an electrical beat note signal and a difference between clockwise and counterclockwise resonant frequencies of an optical resonator coil of the RFOG are determined. The orthogonal products are converted to a phase which is differentiated with respect to time to obtain a beat note correction signal.

Apparatus and method for enhanced beat note detection

Systems and methods are provided to reduce at least one differential harmonics of a resonance tracking modulation in a resonant fiber optic gyroscope (RFOG). The fundamental frequency of the resonance tracking modulation of each of the clockwise and counter clockwise optical signals is substantially identical; however, the amplitude and phase of the Nth harmonic of a clockwise (CW) resonance tracking modulation and the Nth harmonic of a clockwise (CCW) resonance tracking modulation may differ due to non-linearities in the RFOG. Embodiments of the invention diminish, e.g., reduce to zero such vectoral difference. Differential harmonics may be generated at one or more harmonics.

Systems and methods to reduce differential harmonics of resonance tracking modulation in a resonant fiber optic gyroscope

In one embodiment, a phase lock loop circuit includes a control circuit, wherein the control circuit is configured to input an estimation having a second frequency and a second phase. The second frequency is selected from a range of frequencies including a first frequency from an acquired signal. A numerically controlled oscillator is coupled to the control circuit, wherein the control circuit is configured to control an output response of the numerically controlled oscillator. The numerically controlled oscillator is configured to receive the estimation from the control circuit and generate an output signal in response to the estimation. A phase detector is coupled to the control circuit and the numerically controlled oscillator, wherein the phase detector is configured to compare the first signal and the output signal and produce a comparison output, the comparison output indicative of a phase difference between the first signal and the estimation.

High-bandwidth phase lock loop circuit with sideband rejection

Techniques are provided for correcting for time varying changes to a gyroscope incorporating a resonator and/or to an environment in which the gyroscope is located, and which affect the resonator. Free spectral range of the gyroscope, which varies with such changes, is determined and is used to correct at least one of gyroscope bias and scale factor.

Systems and methods for correcting errors in gyroscopes

A hyperbolic modulation offset reducer circuit for a resonator fiber optic gyro (RFOG) is provided. The circuit includes a first demodulation circuit that is configured to demodulate a received transmission signal from a resonator at twice a sideband heterodyne detection modulation frequency to reject signals due to backscatter. A slave resonance tracking loop of the circuit is coupled to an output of the first demodulation circuit. The slave resonance tracking loop is configured to create an offset frequency signal from the transmission signal that is applied to an optical phase lock loop of a RFOG. A hyperbolic modulator offset control loop is also coupled to the output of the first demodulation circuit. The hyperbolic modulator offset control loop is configured to create a subharmonic common modulation signal from the transmission signal that is coupled to a common phase module in a silicon photonics chip of the RFOG.

Hyperbolic modulation offset error reducer for an RFOG

A system comprising a fiber optic gyroscope and a mixed signal application specific integrated circuit (ASIC) connected to the gyroscope is provided. The mixed signal ASIC comprises a digital logic unit, a relative intensity noise (RIN) analog-to-digital converter (ADC) coupled to the digital logic unit and configurable to receive a signal from a RIN detector, and a rate ADC coupled to the digital logic unit and configurable to receive a signal from a rate detector. The mixed signal ASIC also includes a light source digital-to-analog converter (DAC) coupled to the digital logic unit, and a thermo-electric cooler DAC coupled to the digital logic unit, both of which are configurable to send control signals to a light source of the gyroscope. The mixed signal ASIC further includes an integrated optical chip DAC, an eigen-frequency servo DAC, and a heater servo DAC, all of which are coupled to the digital logic unit.

Fiber optic gyroscope mixed signal application specific integrated circuit

A spurious frequency attenuation servo comprises a first signal generated at a first frequency including at least one spur at at least one respective spurious frequency (spur). The signal is filtered by a first fixed filter. A single sideband (SSB) mixer is configured to output a SSB output signal that comprises a difference of frequencies of an output of the first fixed filter mixed with another signal. The SSB output signal includes a direct current component and the spur, and is received by a second fixed filter, which filters out the SSB output signal and outputs the spur. At least one spur attenuation controller is configured to accumulate error after reading an error term in the spur and to keep integrating until the error term is driven to zero. At least one spur killer is configured to remove the spur when the error term is driven to zero.

Spurious frequency attenuation servo without tuning filter

A spurious frequency attenuation servo is provided. The spurious frequency attenuation servo includes a first function generator that generates a first signal at a first frequency and at a spurious frequency; a second function generator that generates a second signal in-phase with the first signal and at the spurious frequency; a third function generator that generates a third signal ninety degrees out-of-phase with the first signal and at the spurious frequency; in-phase and quadrature-phase mixers to input a feedback signal and the second and third signals, respectively; in-phase and quadrature-phase error accumulators; an in-phase and quadrature-phase multiplier to multiply an output from the in-phase and quadrature-phase error accumulators with the second and third signals, respectively; and a summing node to sum the first signal with output from the in-phase and quadrature-phase multipliers to form an output signal that is fed back to the in-phase mixer and the quadrature-phase mixer.

Spurious frequency attenuation servo

Systems and methods for environmentally insensitive high-performance fiber-optic gyroscopes are provided. In one embodiment, a loop closure electronics apparatus for a fiber optic gyroscope having an optical phase modulator characterized by a transfer function that includes an error component of at least second order is provided. The apparatus comprises: a first digital circuit that generates a digital bias modulation signal; a second digital circuit that generates a digital feedback signal; at least one digital-to-analog converter that produces an electrical signal that drives the phase modulator from the digital bias modulation signal and the digital feedback signal; and a compensator that includes an analog filter of at least second order and a digital filter of at least second order, wherein the analog filter and the digital filter pre-filter the electrical signal to compensate for the error component.

Systems and methods for environmentally insensitive high-performance fiber-optic gyroscopes

Systems and methods for improved resonator fiber optic gyroscope intensity modulation control are provided. In one embodiment, a resonant fiber optic gyroscope (RFOG) having a residual intensity modulation (RIM) controller is provided. The controller includes an intensity modulator optically coupled to receive a light beam from a laser source modulated at a resonance detection modulation frequency, and an optical tap device optically coupled to the intensity modulator. The controller also includes a feedback servo coupled to the optical tap device and the intensity modulator, the demodulating feedback servo generating a sinusoidal feedback signal to the intensity modulator. The feedback servo adjusts an amplitude and phase of the sinusoidal feedback signal provided to intensity modulator based on a residual intensity modulation detected by the demodulating feedback servo.

Systems and methods for resonator fiber optic gyroscope intensity modulation control

A fiber optic gyroscope includes a light source, an optical coupler in optical communication with the light source, with the optical coupler configured to receive an optical signal from the light source, an optical modulator in optical communication with the optical coupler, and a fiber optic coil in optical communication with the optical modulator. A demodulator is configured to receive an optical signal from the optical coupler and convert the optical signal to an electrical signal. A loop closure electronics module is configured to receive the electrical signal from the demodulator. A bias modulator is responsive to an output from the loop closure electronics module and is configured to output a modulation signal to the optical modulator. A first crosstalk filter network is operatively coupled to the demodulator, and a second crosstalk filter network is operatively coupled to the bias modulator.

System to reduce gyroscopic errors with limited power supply quality in a fiber optic gyroscope

Systems and methods for improved resonator fiber optic gyroscope intensity modulation control are provided. In one embodiment, a resonant fiber optic gyroscope (RFOG) having a residual intensity modulation (RIM) controller comprises: an intensity modulator optically coupled to receive a light beam from a laser source modulated at a resonance detection modulation frequency; an optical tap device optically coupled to the intensity modulator; and a feedback servo coupled to the optical tap device and the intensity modulator, the demodulating feedback servo generating a sinusoidal feedback signal to the intensity modulator. The feedback servo adjusts an amplitude and phase of the sinusoidal feedback signal provided to intensity modulator based on a residual intensity modulation detected by the demodulating feedback servo.

A synchronous fiber optic gyroscope includes a light source, an optical coupler in optical communication with the light source, an optical modulator in optical communication with the coupler, and a fiber optic coil in optical communication with the modulator. A detector is configured to receive an optical signal from the coupler and convert the optical signal to an electrical signal. A loop closure signal processor has a first input configured to receive the electrical signal from the detector. A phase lock loop has an output operatively connected to a second input of the processor. A direct digital synthesizer is operatively coupled to an input of the phase lock loop, with the synthesizer configured to generate a low-frequency signal that is transmitted to the phase lock loop. The phase lock loop converts the low-frequency signal to a high-frequency signal that is transmitted to the second input of the processor, and the phase lock loop provides signal modulation that is synchronous with signal demodulation.

Synchronous radiation hardened fiber optic gyroscope

A resonator fiber optic gyroscope includes a first light source configured to generate a light signal. A resonator element is configured to generate an optical signal based on the light signal. A photodetector is configured to generate a first electrical signal based on the optical signal. The first electrical signal includes an oscillating signal, a direct-current (DC) signal, an even-harmonic signal including components at even harmonics of the oscillating signal, and an odd-harmonic signal including components at odd harmonics of the oscillating signal. A filtering element is configured to attenuate the DC signal, at least one even-harmonic component, and an odd-harmonic component to produce a second electrical signal. An amplifier is configured to amplify the second electrical signal. An analog-to-digital converter (ADC) is configured to digitize the amplified second electrical signal.

Signal conditioning to provide optimum gain and noise reduction for resonator fiber optic gyroscopes

A gyroscope for determining an angular rate output. The gyroscope includes a first demodulator configured to demodulate an angular rate measurement at a first bias modulation frequency to determine the angular rate signal and a second demodulator configured to demodulate the angular rate measurement at a second bias modulation frequency to provide a signal with ARW information. The gyroscope further includes an ARW estimator that provides an output that is proportional to ARW that is then stored in a memory. The second bias modulation frequency is an even order harmonic of the first bias modulation frequency.

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Glendale, AZ, United States of America

Norman Gerard Tarleton