Satellite navigation receiver with fixed point sigma RHO filter

• US 10,048,385 B2
• Filed: 10/12/2015
• Issued: 08/14/2018
• Est. Priority Date: 10/12/2015
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Yu, Wei, Keegan, Richard G., Hatch, Ronald R.
• Primary Examiner(s): Nguyen, Chuong P
• Application Number:
  US14/880,852
• Publication Number:
  US 20170102465A1
• Time in Patent Office: 1,037 Days
• Field of Search: 34235768, 34235769, 34235776, 34235777
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/36 relating to the receiver frond end
• CPC Class Codes: G01S 19/37 Hardware or software details of the signal processing chain

Abstract

A multi-band satellite navigation receiver for carrier and code tracking using a fixed point sigma rho filter with improved stability is described. The receiver simplifies and speeds up the data processing in the filter to adaptively accommodate common information from aggregate bands and obtain the accurate position of the receiver in real time. The filter may utilize a standard deviation function and a cross correlation function while determining adaptive scale factors to ensure that the filter is stable and reliable.

Claims

1. A satellite navigation receiver comprising:

a receiver front end for down-converting a composite received signal comprising a plurality of carrier signals;

an analog-to-digital converter for converting the down-converted composite received signal to a digital composite received signal;

a plurality of signal generators each for generating a local reference carrier signal and a local reference ranging code based on carrier corrective control data and code corrective control data based on feedback from an aggregate predictive filter, wherein the local reference carrier signal and the local reference ranging code are associated with one of the plurality of carrier signals;

a plurality of receiver modules each comprising a correlator for determining one of a plurality of correlations of the digital composite received signal to the local reference carrier signal and the local reference ranging code, wherein each of the plurality of correlations comprises an in-phase correlation and a quadrature correlation and is associated with one of the plurality of carrier signals; and

the aggregate predictive filter in communication with the plurality of signal generators, the aggregate predictive filter for estimating the carrier corrective control data and the code corrective control data based on the plurality of correlations.

2. The satellite navigation receiver of claim 1, wherein the aggregate predictive filter estimates the carrier corrective control data and the code corrective control data at a reference frequency based on the plurality of correlations, and wherein the carrier corrective control data and the code corrective control data represent a correction to a range estimation between the receiver and a satellite.

3. The satellite navigation receiver of claim 2:

further comprising a plurality of scaling modules in communication with the aggregate predictive filter, each of the plurality of scaling modules for respectively scaling the carrier corrective control data and the code corrective control data at the reference frequency to scaled carrier corrective control data and scaled code corrective control data at a frequency of each of the plurality of carrier signals;

wherein the plurality of signal generators is for generating the local reference carrier signal and the local reference ranging code based on the scaled carrier corrective control data and the scaled code corrective control data.

4. The satellite navigation receiver of claim 2, wherein:

each of the plurality of correlations is for a frequency of each of the plurality of carrier signals;

the aggregate predictive filter is further for weighting each of the plurality of correlations based on a signal quality metric.

5. The satellite navigation receiver of claim 4, wherein the signal quality metric comprises one or more of a signal-to-noise ratio or a moving average of the signal-to-noise ratio over a sliding window.

6. The satellite navigation receiver of claim 2, wherein:

the carrier corrective control data comprises carrier corrective control data at the reference frequency and carrier corrective control data at a frequency of each of the plurality of carrier signals;

the code corrective control data comprises code corrective control data at the reference frequency and code corrective control data at a frequency of each of the plurality of carrier signals; and

the aggregate predictive filter comprises;

a carrier loop discriminator determining a carrier tracking error at the reference frequency from the plurality of correlations;

a code loop discriminator for determining a code tracking error at the reference frequency from the plurality of correlations; and

a joint estimator for;

determining the carrier corrective control data at the reference frequency and the code corrective control data at the reference frequency, based on the carrier tracking error and the code tracking error; and

estimating the carrier corrective control data at a frequency of each of the plurality of carrier signals and the code corrective control data at a frequency of each of the plurality of carrier signals, based on the carrier tracking error and the code tracking error.

7. The satellite navigation receiver of claim 1, further comprising a navigation estimator for estimating one or more of a position or a velocity based on a phase of local reference carrier signal and a phase of the local reference ranging code.

8. The satellite navigation receiver of claim 1, wherein the aggregate predictive filter comprises a fixed-point sigma-rho filter for estimating the carrier corrective control data and the code corrective control data, wherein the carrier corrective control data and the code corrective control data comprise one or more of an estimated code phase, an estimated carrier phase at a reference frequency, a Doppler shift, a rate of change of the Doppler shift, a strength of the plurality of carrier signals, or an amplitude of the plurality of carrier signals.

9. The satellite navigation receiver of claim 1, wherein the aggregate predictive filter comprises a fixed-point sigma rho filter for estimating the carrier corrective control data and the code corrective control data using a dynamic propagation stage and a measurement update stage, based on a standard deviation function (sigma) and a cross-correlation function (rho).

10. The satellite navigation receiver of claim 9, wherein the fixed-point sigma-rho filter estimates the carrier corrective control data and the code corrective control data by dynamically selecting an adaptive scale factor η

to bound coefficients of the cross-correlation function within one during the dynamic propagation stage, based on previous coefficients of the cross-correlation function.

11. The satellite navigation receiver of claim 9, wherein the fixed-point sigma-rho filter estimates the carrier corrective control data and the code corrective control data by selecting a rescale parameter γ

to limit a parameter β

to less than one during the measurement update stage, based on a predetermined upper limit.

12. The satellite navigation receiver of claim 9, wherein the fixed-point sigma-rho filter estimates the carrier corrective control data and the code corrective control data by determining an adaptive scale factor μ

to limit coefficients of the cross-correlation function within one during the measurement update stage, wherein the adaptive scale factor is selected from a plurality of predetermined scale factors stored in a lookup table, based on indices of β

_i and β

_j.

13. The satellite navigation receiver of claim 9, wherein the fixed-point sigma-rho filter estimates the carrier corrective control data and the code corrective control data by determining an adaptive scale factor μ

to limit coefficients of the cross-correlation function within one during the measurement update stage, wherein the adaptive scale factor is determined by;

doubling the adaptive scale factor until a predetermined maximum value is reached, if a maximum coefficient of the cross-correlation function is greater than a predetermined upper threshold; and

halving the adaptive scale factor, if the maximum coefficient of the cross-correlation function is less than a predetermined lower threshold.

14. The satellite navigation receiver of claim 9, wherein the fixed-point sigma-rho filter is implemented as a phase-locked loop (PLL).

15. The satellite navigation receiver of claim 1, wherein the plurality of carrier signals comprises a first carrier (L1), a second carrier (L2), and a third carrier (L5).

16. The satellite navigation receiver of claim 1:

further comprising a band pass filter for filtering the digital composite received signal into a plurality of filtered carrier signals that are each associated with a different carrier signal within the digital composite received signal;

wherein the correlator of each of the plurality of receiver modules is for determining the correlation of one of the plurality of filtered carrier signals to the local reference carrier signals and the local reference ranging code.