Satellite navigation receiver with aggregate channel digital baseband processing
A demodulator comprises a first-stage carrier demodulator and a second-stage carrier demodulator. The first-stage carrier demodulator is configured to remove or compensate for the tracking error in the baseband signal, where the tracking error comprises aggregate, channel tracking error of carrier phase for the same received band, sub-band, (baseband) GNSS satellite channel, or set GNSS channels. The second stage carrier demodulator is configured to remove or strip a carrier signal component without any unwanted image or carrier-related frequency artifacts and to prepare for correlation-based decoding or demodulation of the encoded baseband signal by the correlators. First correlators are configured to determine correlations for code phase tracking loop, where the code phase tracking loop is configured to estimate a corresponding code error component of the tracking error for the code local oscillator for a respective channel. Secondary correlators are configured to determine correlations for a carrier phase tracking loop, where the carrier phase tracking loop configured to estimate a corresponding aggregate feedback error for multiple channels or a set of channels.
1. A receiver system having a digital baseband data processing system, the receiver system comprising:
a receiver front-end module comprising an analog-to-digital converter for providing a baseband signal derived from a received satellite GNSS signal;
a baseband tracking loop module for tracking carrier phase and code phase of a band, a sub-band, a channel or a set of channels, the baseband tracking loop module being configured to derive correction or control signals to control one or more local oscillators and to provide an aggregate code and carrier component, of the channel tracking error of the respective band, sub-band, channel or set of channels;
a clock tracking loop for tracking clock error, the clock error having a clock error component comprising a clock bias between a GNSS receiver clock and a respective satellite clock associated with the baseband signal of the band, the sub-band, the channel, or the set of channels;
a frequency scaler for adjusting the frequency of the clock error component with respect to the frequency of channel tracking error of the carrier phase, code phase or both of the baseband signal based on the band, the sub-band, the channel or the set of channels;
a summer for determining a tracking error based on the aggregate, channel code and carrier component and the clock error component;
a demodulator comprising a first-stage carrier demodulator and a second-stage carrier demodulator;
the first-stage carrier demodulator configured to (i) receive the baseband signal from the baseband tracking loop module, (ii) remove or compensate for the tracking error in the baseband signal, where the tracking error comprises aggregate, channel tracking error of carrier phase and code phase for the same received band, sub-band, GNSS satellite channel, or set of GNSS channels, and (iii) output a partially demodulated baseband signal;
the second stage carrier demodulator configured to (i) receive the partially demodulated baseband signal from the first stage carrier demodulator and (ii) remove or strip a carrier signal component without any unwanted image or carrier-related frequency artifacts and to prepare for correlation-based decoding or demodulation of the encoded baseband signal by the correlators;
a first plurality of first correlators configured to determine correlations for code phase tracking loop and the carrier phase tracking loop, the code phase tracking loop configured to estimate a corresponding code error component of the tracking error for the code local oscillator for a respective band, sub-band, channel or set of channels, the carrier tracking loop configured to estimate a carrier phase error component of the tracking error for a carrier local oscillator for the same respective band, sub-band, channel or set of channels; and
a second plurality of correlators configured to determine correlations for clock tracking loop and the clock error component of the tracking error.
2. The receiver according to claim 1 wherein for the clock tracking loop, the receiver further comprises a navigation, control and interface module configured to estimate a pseudo-range measurements and carrier phase measurements and other related information from satellites that transmit the received GNSS signals to generate the positioning solution, which is used as a feedback to estimate clock error component to align the receiver crystal-grade clock that provides a reference clock input to the code local oscillator and the carrier local oscillator for a corresponding satellite and a selected band, sub-band, channel or set of channels of the baseband signal.
3. The receiver according to claim 1 further comprising:
a Line-of-Sight (LOS) estimation module is coupled to provide input to the baseband tracking module, the LOS estimation module configured to estimate pseudo-range measurements and carrier phase measurements from satellites that transmit the received GNSS signals;
an external sensor configured to provide navigation augmentation data to the LOS module, the external sensor comprising one or more of the following: an inertial measurement unit, an accelerometer, a gyroscope, a skyward-facing or upward-facing imaging device, a monocular camera, a stereo vision camera, radar system, a LIDAR system, received or stored satellite almanac and/or satellite ephemeris data of the GNSS receiver, and received or stored satellite rising time and setting times for geographic coordinates of a mobile GNSS receiver at particular date and time.
4. The receiver according to claim 3 wherein the LOS estimation module is configured to determine blocked or materially attenuated signals of GNSS satellites that would otherwise be in view or reception range based on observations of a skyward-facing or upward-facing imaging device, a monocular camera, a stereo vision camera, radar system, a LIDAR system, or based on stored satellite data indicative of excluded/blocked/attenuated satellites at or below a threshold low elevation angle.
5. The receiver according to claim 3 wherein the LOS estimation module is configured to estimate: (a) LOS data comprising pseudo-range measurements and carrier phase measurements from satellites that transmit the received GNSS signals, and (b) motion-corrected LOS data, or Doppler-corrected LOS data based on observations of an inertial measurement unit, an accelerometer, or a gyroscope applied to the LOS data.
6. The receiver according to claim 5 wherein the Doppler-corrected LOS data comprises Doppler-effect smoothed pseudoranges, clock frequency estimation of GNSS receiver clock based on Doppler shift, estimated position, attitude, velocity, acceleration, motion data and GNSS time for a corresponding GNSS receiver.
7. The receiver according to claim 3 wherein the LOS estimation module is configured to estimate a compensating adjustment or time offset to the clock local oscillator of the clock tracking loop for application to the carrier local oscillator of the channel baseband tracking loop to adjust the generated local code signal or code replica based on a Doppler shift of the received GNSS signal at the rover or mobile GNSS receiver.
8. The receiver according to claim 3 further comprising:
a vector tracking module configured to communicate with the channel baseband tracking loop module and the clock tracking loop module, the vector tracking module and the LOS estimation module combine a bank of correlations from a first channel with the signal from a mth channel to produce the estimated LOS data for the first channel and up to the mth channel;
the LOS estimation module, alone or in combination with the external data sensor, is configured to produce the estimated LOS data for the first channel and up the mth channel for each applicable satellite and corresponding GNSS receiver; and
a baseband tracking loop of the first channel uses a correlation signal to produce the residual frequency for input to the second-stage carrier demodulator.
9. The receiver according to claim 3 wherein:
a baseband tracking loop of a first channel is configured to use a correlation signal to produce the residual frequency for input to the second-stage demodulator; and the baseband tracking loop module is configured to receive the derived satellite LOS or other data signals from the LOS estimation module and a vector tracking module to produce the LOS-affiliated carrier frequency that comprises an LOS frequency or carrier frequency associated with LOS data.
10. The receiver according to claim 3 wherein:
the LOS estimation module is configured for communication to the channel baseband module;
the channel baseband module is configured to determine the LOS carrier-removed signal or local code replica signal based on the LOS data from the LOS estimation module; the local code replica being generated by a matched filter with an impulse response that is reversed in time.
11. The receiver according to claim 1 further comprising:
the local code oscillator comprising a code numerically controlled oscillator (NCO) of the baseband tracking loop module for the band, sub-band, channel, or set of channels, the code NCO being configured to provides an estimated replica or an estimated local code signal for the first plurality of correlators;
the local carrier oscillator comprising a carrier NCO of the baseband tracking loop module for the band, sub-band, channel, or set of channels, the carrier NCO being configured to provide an estimated local replica or an estimated aggregate local code signal for a corresponding set of GNSS signals for the second-stage carrier demodulator;
the clock local oscillator comprising a clock NCO of the clock tracking loop module for the band, sub-band, channel, or set of channels for the to provide an estimated local replica or an estimated aggregate local clock signal for the second plurality of correlators for clock tracking.
12. The receiver according to claim 11 wherein the carrier NCO of the channel baseband tracking loop is configured to provide an estimated local replica or an estimated aggregate local code signal for a corresponding set of GNSS signals for the second-stage carrier demodulator and the channel baseband tracking loop to maintain the synchronization between the received signal in the channel and the local replica of that channel with respect to code phase, carrier phase, or both based on accumulations or correlations associated with the first plurality of the correlators and the second plurality of correlators.
13. The receiver according to claim 1 further comprising:
a vector tracking module configured to communicate with the channel baseband tracking loop module and the clock tracking loop module, the vector tracking module configured to provides estimated carrier frequency and phase and estimated code frequency and phase, consistent with input from a navigation module that may comprise an extended Kalman filter or Kalman filter that processes one or more demodulated/decoded GNSS channels from correlators or accumulators associated with the output of the first correlators and second correlators, for clock tracking, to reduce tracking error in the decoded data of the each GNSS output channel.
14. The receiver according to claim 3 wherein the second correlators are configured to generate in-phase and quadrature-phase correlation for one or more channels based on a local code replica being generated by a matched filter with an impulse response that is reversed in time.
15. The receiver according to claim 1 further comprising:
a vector tracking module configured to communicate with the channel baseband tracking loop module and the clock tracking loop module, the vector tracking module configured to provide feedback or tracking error data to numerically controlled oscillators of the channel baseband tracking loop module and the clock tracking loops to replicate or determine a local estimation of one or more of the following: each carrier phase of corresponding GNSS channel, or set of corresponding GNSS channels, or a collective representative aggregate or super GNSS channel that represents a set of corresponding GNSS channels; each code phase of a corresponding encoded GNSS signal or a set of corresponding GNSS channels, or a collective representative aggregate or super GNSS channel that represents a set of corresponding GNSS channels; and each clock phase and clock frequency of a corresponding encoded GNSS signal or set of corresponding GNSS channels, or a collective representative GNSS channel that represents a set of corresponding GNSS channels.
16. A receiver system having a digital baseband data processing system, the receiver system comprising:
a receiver front-end module comprising an analog-to-digital converter for providing baseband signal derived from a received satellite GNSS signal;
a baseband tracking loop module for tracking carrier phase and code phase of a band, a sub-band, a channel or a set of channels, the baseband tracking loop module being configured to derive correction or control signals to control one or more local oscillators and to provide an aggregate code and carrier component, of the channel tracking error of the respective band, sub-band, channel or set of channels;
a clock tracking loop for tracking clock error for the receiver system, the clock error having a clock error component comprising a clock bias between a GNSS receiver clock and a respective satellite clock associated with the baseband signal of the band, the sub-band, the channel, or the set of channels;
a frequency scaler for adjusting the frequency of the clock error component with respect to the frequency of channel tracking error of the carrier phase, code phase or both of the baseband signal based on the band, the sub-band, the channel or the set of channels;
a summer for determining a tracking error based on the aggregate, channel code and carrier component and the clock error component;
a demodulator comprising a first-stage carrier demodulator and a second-stage carrier demodulator;
the first-stage carrier demodulator configured to (i) receive the baseband signal from the baseband tracking loop module, (ii) remove or compensate for the tracking error in the baseband signal, where the tracking error comprises aggregate, channel tracking error of carrier phase for the received band, sub-band, GNSS satellite channel, or set of GNSS channels, and (iii) output a partially demodulated baseband signal;
the second stage carrier demodulator configured to (i) receive the partially demodulated baseband signal from the first stage carrier demodulator and (ii) remove or strip a carrier signal component without any unwanted image or carrier-related frequency artifacts and to prepare for correlation-based decoding or demodulation of the encoded baseband signal by the correlators;
a first plurality of first correlators configured to determine correlations for code phase tracking loop, the code phase tracking loop configured to estimate a corresponding code error component of the tracking error for the code local oscillator for a respective channel;
a plurality of secondary correlators configured to determine correlations for carrier phase tracking loop, the carrier phase tracking loop configured to estimate a corresponding aggregate feedback error for multiple channels or a set of channels, where the aggregate feedback error comprises a carrier phase error component of the tracking error for a carrier local oscillator for the same respective band, sub-band, channel or set of channels; and
a second plurality of correlators configured to determine correlations for clock tracking loop and the clock error component of the tracking error.
17. The receiver system according to claim 16 wherein the carrier local oscillator comprises a numerically controlled oscillator for the L 1 -C/A channel or the L 1 C channel of a given satellite that provides or that is used to derive a local carrier frequency signal, or IF frequency signal, which is aligned with the L 1 P carrier phase of a received GNSS signal of the given satellite.
18. The receiver system according to claim 17 wherein the carrier tracking loop comprises an aggregate or multi-channel carrier tracking loop for channels of a given satellite with the secondary correlators that accept samples of the carrier local oscillator signal and samples of the received GNSS signal of the same satellite to be aligned to provide candidate correlations.
19. The receiver system according to claim 18 wherein the carrier tracking loop comprises a carrier loop discriminator for the L 1 -C/A channel or L 1 C channel of a given satellite, together with a carrier loop filter, for evaluating L 1 -C/A or L 1 C carrier phase plane alignment of a given satellite.
20. The receiver system according to claim 16 wherein the carrier local oscillator comprises a shared numerically controlled oscillator for an L 2 C complex channel of a given satellite that provides, or that is used to derive, a local carrier frequency signal, or IF frequency signal, which is aligned with the L 2 P carrier phase of a received GNSS signal of the given satellite.
21. The receiver system according to claim 20 wherein the carrier tracking loop comprises an aggregate or multi-channel carrier tracking loop for the L 2 C complex channel of a given satellite with the secondary correlators that accept samples of the carrier local oscillator signal and samples of the received, evaluated GNSS signal of the same satellite to be aligned to provide candidate correlations.
22. The receiver system according to claim 21 wherein the carrier tracking loop comprises a carrier loop discriminator for the L 2 C channel of a given satellite, together with a carrier loop filter, for evaluating L 2 C carrier phase plane alignment of a given satellite.
23. The receiver system according to claim 16 wherein the code local oscillator for a respective channel comprises a common numerically controlled oscillator that provides a derivative signal to another numerically controlled oscillator for a complex L 1 C channel.
24. The receiver system according to claim 23 wherein L 1 C is multiplexed with L 1 C/A for backwards compatibility of L 1 C/A and is modulated or encoded with Alternate BOC (Binary Offset Carrier) or Multiplexed Binary Offset Carrier (MBOC) spread signal to form a complex encoded channel.