Blanked Correlator Multipath Mitigation in GNSS Tracking
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Solution Overview
Problem
Global Navigation Satellite System (GNSS) receivers face significant errors due to multipath propagation, affecting both carrier and code measurements, which degrade position and navigation performance.
Innovation Solution
The use of a blanked correlator in conjunction with a full correlator within the GNSS receiver's tracking loop to mitigate carrier phase multipath errors, where the blanked correlator operates as a monitoring correlator to estimate and correct carrier phase multipath errors externally or internally within the tracking loop, utilizing a chip-edge accumulation process and running-sum filtering to reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a full correlator is used for carrier tracking, then tracking accuracy is improved, but multipath error estimation capability deteriorates
Solution Approach 1:
The patent divides the correlator function into two separate components: a full correlator for carrier tracking and a blanked correlator for multipath error estimation. The blanked correlator uses a segmented version of the full correlator where only specific portions of the code are processed, allowing independent optimization for error detection without compromising tracking accuracy.
Solution Approach 2:
The blanked correlator acts as an intermediary component that processes the same signal as the full correlator but with modified parameters (narrower spacing, blanked portions). This intermediary structure enables multipath error estimation while the full correlator maintains primary tracking functionality.
2Measurement precision
If correlator spacing is reduced for blanked correlator, then multipath error estimation precision is improved, but signal processing complexity increases
Solution Approach 1:
The patent applies parameter changes by using different correlator spacing values for the blanked correlator compared to the full correlator. The blanked correlator uses reduced spacing (e.g., 0.1 chips) to enhance multipath error estimation precision, while the full correlator maintains its standard spacing for optimal tracking performance.
Solution Approach 2:
The blanked correlator processes only partial portions of the signal (blanked portions of the code) rather than the entire signal. This partial action approach reduces the computational burden compared to processing the full signal with high precision, while still achieving accurate multipath error estimation.
3Measurement precision
If multipath mitigation is applied externally to tracking loop, then measurement accuracy is improved, but system response time increases
Solution Approach 1:
The patent implements feedback by using the multipath error estimates from the blanked correlator to correct the carrier phase measurements from the full correlator. The corrected measurements are then fed back into the tracking loop, creating a closed-loop system that continuously improves accuracy while maintaining real-time operation.
Solution Approach 2:
The blanked correlator performs preliminary error estimation before the final measurement is taken. By pre-processing the signal to estimate multipath errors, the system can then apply corrections to the full correlator measurements without significantly delaying the overall measurement process.
4Measurement precision
If blanked correlator operates independently of tracking loop, then measurement independence is improved, but integration complexity increases
Solution Approach 1:
The patent segments the signal processing functionality into independent modules: the full correlator for tracking and the blanked correlator for error estimation. This segmentation allows each module to operate independently with optimized parameters, while the results are combined through a coordination interface that manages the integration complexity.
Data Source
AI summary
Techniques are provided for GNSS carrier phase multipath mitigation using a blanked correlator in conjunction with a full correlator. A tracking loop may track a carrier of the GNSS signal utilizing the full correlator. A chip-edge accumulation (CEA) unit of the tracking loop may accumulate chip edges of a ranging code to generate CEA output. A blanked correlator may receive the CEA output to generate blanked correlator values. A running-sum filter may utilize the blanked correlator values to generate a running-sum value. A phase estimate may utilize the running-sum value to generate phase estimator output. In an exemplary embodiment, the blanked correlator operates as a monitoring correlator and the phases estimator output is the estimated carrier phase multipath error. In an exemplary embodiment, the blanked correlator provides input to the tracking loop and discriminator output is subtracted from the phase estimator output to generate the estimated carrier phase multipath error.