Alliedsignal Inc.

Honeywell International Inc.

Robert A Kovacs

Walter P Hollinger

Kevin M Killian

Michael K Scruggs

Pei-hwa Lo

Peter A Wall

Ming-Hsing Yu

A signal conditioning circuit reduces an interferrometric fiber optic gyro (IFOG) noise, the IFOG including a light source, Integrated Optics Chips (IOC) and a coupler to output an optical power signal corresponding to a rotation-induced phase shift in a fiber coil of the IFOG. The signal conditioning circuit includes a photodiode that converts the optical power signal to a corresponding electrical compensation signal and one or more switched integrators that receive and process the electrical compensation signal by selectively switching between a plurality of modes of each one of the one or more switched integrators. A method of signal conditioning in the IFOG to reduce IFOG noise includes the steps of converting the optical power signal to a corresponding electrical compensation signal and selectively integrating a current of the electrical compensation signal using at least one switched integrator.

Apparatus and method using digitally controlled integration for signal detection with improved noise characteristics

A noise reducing thermal-electrically cooled photodetector for an Interferrometric Fiber Optic Gyro (IFOG) includes a photodiode that converts an optical power signal received from a coupler of the IFOG to an electrical compensation signal. The photodiode is in mechanical contact with one or more thermoelectric coolers (TEC) to lower an operating temperature of the photodiode. The photodetector also includes an amplifier circuit to amplify the electrical compensation signal. The amplifier circuit includes an operational amplifier having an input and an output, with a feedback resistor interposed between the input and output. The feedback resistor is also in mechanical contact with a TEC to lower an operating temperature of the feedback resistor. By reducing the operating temperature of the feedback resistor and the photodiode the thermal noise of the IFOG is reduced.

Thermal-electrically cooled photodetector

The linearity of a fiber optic gyroscope can be improved by dithering the gyroscope's feedback signal. An output signal can be taken over any time interval by sampling the feedback signal before dithering is applied.

Fiber optic gyroscope with variable output period

The linearity of a fiber optic gyroscope can be improved by dithering the gyroscope's feedback signal. Any undesirable effects introduced by the dithering signal are removed by processing the gyroscope data over an entire cycle of the dithering signal. A further improvement in linearity can be achieved by introducing a compensation signal.

Fiber optic gyroscope with reduced non-linearity at low angular rates

A system for tuning out an error signal in high performance fiber optic gyroscopes includes a compensation network having both active and passive filters which include the necessary pole and zero to cancel out the error signal. The entire system includes a fiber optic gyroscope connected to an amplifier, signal processor, square wave detector, modulator driver and the compensation network. The compensation network is connected between the modulator driver and the phase modulator of the fiber optic gyroscope.

Tuned integrated optic modulator on a fiber optic gyroscope

A fiber optic rate sensor includes an arrangement for suppressing transient spikes in a signal corresponding to the phase difference between light traveling in clockwise and counterclockwise directions around a fiber optic coil. The arrangement is such that the signal having the transient spikes is clamped or switched at the times the spikes are active.

Fiber optic angular rate sensor including arrangement for reducing

A closed loop fiber optic gyro features signal processing wherein square wave phase modulation is added to a modulation drive signal after overflow logic so that the square wave modulation will not cause a phase modulation ramp to exceed overflow/underflow logic limits. The arrangement is such that the phase modulation causes a retrace with each modulation period when the amplitude of the ramp is within predetermined limits. A variable time constant in a retrace correction loop gives better retrace limit correction performance when the gyro is first turned on as during a 'warm-up' period. The amplitude of the gyro square wave output is determined by taking the difference between the output of the first half cycle of the square wave modulation and the average of adjacent second half cycles thereof. An error signal for a retrace limit is developed by considering changes in the square wave amplitude and not the square wave amplitude itself. Corrections in the retrace limit are implemented via a variable digital retrace point. These features are effective for reducing gyro sensitivity to electronic drift.

Closed loop fiber optic gyroscope with reduced sensitivity to electronic

A closed loop fiber optic gyro features signal processing wherein square wave phase modulation is added to a modulation drive signal after overflow logic so that the square wave modulation will not cause a phase modulation ramp to exceed overflow/underflow logic limits. The arrangement is such that the phase modulation causes a retrace with each modulation period when the amplitude of the ramp is within predetermined limits. Corrections to the retrace limit are implemented so as to scale a digital output, which enables the determination of accumulated gyro angle with a finer resolution than simple output pulse accumulation as has heretofore been the case.

Closed loop fiber optic gyroscope with fine angle resolution

A closed loop fiber optic gyro features signal processing wherein square wave phase modulation is added to a modulation drive signal after overflow logic so that the square wave modulation will not cause a phase modulation ramp to exceed overflow/underflow logic limits. The arrangement is such that the phase modulation causes a retrace with each modulation period when the amplitude of the ramp is within predetermined limits. The square wave amplitude from a cycle immediately after a retrace is considered as errant data that should be excluded from a phase nulling loop. Thus, the phase nulling loop has more accurate input data so that feedback will be accomplished more effectively for improved gyro performance.

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West Orange, NJ, United States of America

Robert A Kovacs