Gnss correlation distortion detection and mitigation
AssigneeNovAtel Inc.
InventorAli Broumandan
Life of this patent
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Abstract
Structures and techniques are disclosed that can be used to reduce or remove code multipath error in GNSS receivers by implementing one or more monitoring correlators in a multipath-error estimation and correction (MEC) module. The MEC module detects and provides for correction of correlation peak distortion. In exemplary embodiments, a code tracking loop integrates all-chip-edges of a PRN, and a narrow-correlator is used to update the tracking loop rate while a multipath estimation module implements a blanked correlator to estimate and remove the multipath bias from the code tracking loop measurements.
Claims19
A GNSS-receiver multipath-correcting tracking loop structure comprising:
- (A) a code tracking loop configured as a delay lock loop (DLL), the code tracking loop including,
- (i) an integration unit, wherein the integration unit is operative to accumulate all the chip transitions of each PRN code of a received GNSS signal and produce a chip-edge accumulation (CEA),
- (ii) a code discriminator,
- (iii) a loop filter,
- (iv) a numerically controlled oscillator (NCO), and
- (v) a code generator;
- and
- (B) a multipath-error estimation and correction (MEC) module including,
- (i) a code multipath correlator unit operative to receive the CEA from the integration unit and implement a monitoring correlator and a prompt correlator to monitor the distortion of the correlation peak and produce a monitoring correlator output,
- (ii) a normalizing unit operative to receive the monitoring correlator output and normalize the monitoring correlator to the prompt correlator and thereby produce a normalized monitoring correlator output,
- (iii) a low pass filter operative to receive and filter the normalized monitoring correlator output, and
- (iv) a code multipath estimation unit operative to receive the normalized monitoring correlator output from the low pass filter, and to produce an estimate of multipath error.
A GNSS receiver comprising:
- a plurality of channels, each channel including,
- (A) a code tracking loop configured as a delay lock loop (DLL), the code tracking loop including,
- (i) an integration unit operative to accumulate all chip transitions of each PRN code of a received GNSS signal,
- (ii) a code discriminator,
- (iii) a loop filter,
- (iv) a numerically controlled oscillator (NCO), and
- (v) a code generator;
- and
- (B) a carrier tracking loop configured as a phase lock loop (PLL), the carrier tracking loop including,
- (i) an integration unit operative to accumulate a full PRN code of the received GNSS signal,
- (ii) a carrier discriminator,
- (iii) a loop filter,
- (iv) a numerically controlled oscillator (NCO), and
- (v) a carrier generator;
- and
- (C) a multipath-error estimation and correction (MEC) module including,
- (i) a code multipath correlator unit operative to receive the CEA from the integration unit and implement a monitoring correlator and a prompt correlator to monitor the distortion of the correlation peak, wherein the code multipath correlator unit is operative to produce a monitoring correlator output,
- (ii) a normalizing unit operative to receive the monitoring correlator output and normalize the monitoring correlator to the prompt correlator, and thereby produce a normalized monitoring correlator output,
- (iii) a low pass filter operative to receive and filter the normalized monitoring correlator output, and
- (iv) a code multipath estimation unit operative to receive the normalized monitoring correlator output from the low pass filter and to produce an estimate of multipath error.
Dependencies are inferred from the claim text.