Satellite positioning system receivers with microelectromechanical systems oscillators
First Claim
1. An apparatus comprising a global positioning satellite (GPS) receiver, the apparatus comprising:
- a microelectromechanical systems (MEMS) oscillator configured to generate a first clock signal as an output, the first clock signal having a phase noise with a first bandwidth;
a phase-locked loop that hasa bandwidth lower than the first bandwidth of the phase noise of the MEMS oscillator;
the phase-locked loop configured to;
receive the first clock signal from the MEMS oscillator as an input; and
generate an NCO clock signal that has less phase noise relative to the phase noise of first clock signal; and
a plurality of channel signal processors configured to despread GPS signals and configured to generate pseudo-range estimates to space vehicles, wherein a channel signal processor of the plurality of channel signal processors comprises at least one numerically controlled oscillator (NCO), wherein the at least one NCO is configured to receive the NCO clock signal that has less phase noise relative to the phase noise of first clock signal;
wherein one or more channel signal processors of the plurality of channel signal processors further comprise an extractor configured to extract vehicle range and carrier phase residual errors, the extractor comprising a discriminator configured to compute at least two nonlinear transformations to generate linear measurements of pseudorange and carrier phase errors, wherein the extractor further comprises an I and Q Noise Variance Estimator further comprising a running average filter configured to compute the I and Q noise variance using a separate outbound correlator channel for respective satellites that is sufficiently away from code that it contains substantially random noise; and
a navigation processor configured to extract at least position information based at least on the plurality of pseudo-range estimates.
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Abstract
Apparatus and methods permit the use of a microelectromechanical systems (MEMS) oscillator in a satellite positioning system receiver, such as a Global Positioning System (GPS) receiver. Techniques to ameliorate jitter or phase noise disadvantages associated with MEMS oscillators are disclosed. For example, a receiver can use one or more of the following techniques: (a) use another source of information to retrieve ephemeris information, (2) perform advanced tight coupling, and/or (3) use a phase-locked loop to clean up the jitter or phase noise of the MEMS oscillator. With respect to advanced tight coupling, an advanced tight coupling processor can include nonlinear discriminators which transform I and Q data into linear residual measurements corrupted by unbiased, additive, and white noise. It also includes an amplitude estimator configured to operate in rapidly changing, high power noise; a measurement noise variance estimator; and a linear residual smoothing filter for input to the navigation filter.
20 Citations
18 Claims
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1. An apparatus comprising a global positioning satellite (GPS) receiver, the apparatus comprising:
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a microelectromechanical systems (MEMS) oscillator configured to generate a first clock signal as an output, the first clock signal having a phase noise with a first bandwidth; a phase-locked loop that has a bandwidth lower than the first bandwidth of the phase noise of the MEMS oscillator; the phase-locked loop configured to; receive the first clock signal from the MEMS oscillator as an input; and generate an NCO clock signal that has less phase noise relative to the phase noise of first clock signal; and a plurality of channel signal processors configured to despread GPS signals and configured to generate pseudo-range estimates to space vehicles, wherein a channel signal processor of the plurality of channel signal processors comprises at least one numerically controlled oscillator (NCO), wherein the at least one NCO is configured to receive the NCO clock signal that has less phase noise relative to the phase noise of first clock signal; wherein one or more channel signal processors of the plurality of channel signal processors further comprise an extractor configured to extract vehicle range and carrier phase residual errors, the extractor comprising a discriminator configured to compute at least two nonlinear transformations to generate linear measurements of pseudorange and carrier phase errors, wherein the extractor further comprises an I and Q Noise Variance Estimator further comprising a running average filter configured to compute the I and Q noise variance using a separate outbound correlator channel for respective satellites that is sufficiently away from code that it contains substantially random noise; and a navigation processor configured to extract at least position information based at least on the plurality of pseudo-range estimates. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. An apparatus comprising a global positioning satellite (GPS) receiver, the apparatus comprising:
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a microelectromechanical systems (MEMS) oscillator configured to generate a first clock signal as an output, the first clock signal having a phase noise with a first bandwidth; a phase-locked loop that has a bandwidth lower than the first bandwidth of the phase noise of the MEMS oscillator; the phase-locked loop configured to; receive the first clock signal from the MEMS oscillator as an input; and generate an NCO clock signal that has less phase noise relative to the phase noise of first clock signal; and a plurality of channel signal processors configured to despread GPS signals and configured to generate pseudo-range estimates to space vehicles, wherein a channel signal processor of the plurality of channel signal processors comprises at least one numerically controlled oscillator (NCO), wherein the at least one NCO is configured to receive the NCO clock signal that has less phase noise relative to the phase noise of first clock signal; a navigation processor configured to extract at least position information based at least on the plurality of pseudo-range estimates; a strapdown inertial measurement unit (IMU); a navigation Kalman filter configured to process vehicle range and carrier phase residual signals to generate vehicle position, velocity, attitude, and time estimates along with IMU error estimates; a strapdown navigation processor configured to integrate the IMU measurements between the navigation Kalman filter processing intervals, wherein the strapdown navigation processor is configured to receive navigation state error estimates from the navigation Kalman filter, and wherein the strapdown navigation processor is configured to receive navigation data from the IMU; and a satellite navigation message decoder configured to provide satellite position, velocity, and acceleration (PVA) data to a processor-implemented satellite line of sight projection estimator and to the navigation Kalman filter; wherein the processor-implemented satellite line of sight projection estimator to project navigation data onto the satellite line of sight, generate range and range rate measurements, and provide these measurements to one or more Numerically Controlled Oscillators configured to provide code and carrier signals for GPS signal phase de-rotation and correlation.
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Specification