GNSS Doppler Compensation Using Delayed-Sample Frequency Estimation
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Solution Overview
Problem
GNSS signals are affected by significant Doppler frequency shifts due to the relative motion between ground-based receivers and satellites, which current GNSS receiver architectures struggle to accurately estimate and compensate for, especially in weak signal conditions or multipath interference.
Innovation Solution
A fine estimation architecture in the baseband processor that includes a sample delay circuitry, complex conjugate transformer, complex multiplier, and frequency estimator to calculate and remove Doppler frequency shifts by correlating and delaying samples, using repeating patterns in GNSS signals to mitigate multipath interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional GNSS receiver architectures are used, then the system can process GNSS signals, but the Doppler frequency estimation accuracy deteriorates under weak signal conditions or multipath interference
Solution Approach 1:
The patent applies preliminary action by using the known repeating pattern structure of GNSS signals to pre-establish correlation templates and delay parameters before signal processing. The correlator is configured with advance knowledge of the repeating pattern period, allowing the system to prepare correlation metrics and Doppler estimation parameters in advance, which improves estimation accuracy when actual signal processing occurs, especially under weak signal or multipath conditions
Solution Approach 2:
The patent implements feedback through the closed-loop Doppler estimation and compensation process. The frequency estimator continuously monitors the correlation output and adjusts the Doppler frequency estimate based on the received signal characteristics. This feedback mechanism allows the system to refine its Doppler estimation in real-time, improving accuracy under varying signal conditions including weak signals and multipath interference
2Manufacturing precision
If Doppler compensation is performed with high accuracy, then positioning precision improves, but the processing time and computational complexity increase
Solution Approach 1:
The patent applies segmentation by dividing the Doppler compensation process into distinct functional modules: correlation processing, Doppler estimation, and frequency compensation. Each module handles a specific aspect of the signal processing task independently, allowing for optimized performance. The correlation processor segments the signal into repeating pattern cycles, the frequency estimator processes the correlation metrics separately, and the compensator applies frequency adjustment in a final stage. This modular segmentation enables efficient processing while maintaining high positioning precision
Solution Approach 2:
The patent utilizes periodic action by leveraging the repeating pattern structure of GNSS signals. The system processes signals in periodic cycles corresponding to the repeating pattern duration, which allows for efficient batch processing and reduces computational overhead. By aligning the processing cycles with the natural periodicity of the signal, the system achieves high Doppler estimation accuracy without proportionally increasing processing time
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables rapid and accurate compensation of Doppler effects, improving GNSS signal processing in weak signal conditions and reducing the impact of multipath interference, thereby enhancing positioning accuracy and reliability.
Implementation Method 1
The sample delay circuitry is arranged operably to delay an output of each sample for a time period of a repeating pattern
Implementation Method 2
The complex conjugate transformer is arranged operably to perform a complex conjugate operation on a complex of a first sample output from the sample delay circuitry
Implementation Method 3
The complex multiplier is arranged operably to calculate a complex multiplication based on a first sample output from the sample delay circuitry and a second sample output from the correlator
Implementation Method 4
The frequency estimator is arranged operably to generate a Doppler frequency based on the complex multiplication, and output the Doppler frequency to a component of the apparatus for removing a Doppler effect from a received GNSS signal
Data Source
AI summary
The disclosure proposes an apparatus and a method for Global Navigation Satellite System (GNSS) Doppler compensation. A complex multiplication is generated based on a first sample and a second sample, where the first sample is a delayed sample. A Doppler frequency is generated based on the complex multiplication. The Doppler frequency is output to a component of a GNSS receiver to remove Doppler effect from a received GNSS signal.