GNSS Signal Loss-of-Lock Detection via Frequency Compensation

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Solution Overview

Problem

GNSS receivers face challenges in accurately tracking satellite signals in indoor and urban environments due to signal attenuation and multipath interference, leading to reduced positioning accuracy and difficulty in detecting loss-of-lock conditions.

Innovation Solution

A method involving multi-channel frequency compensation of I-channel and Q-channel signals after down-conversion and pseudo-code stripping, followed by coherent and non-coherent integration, with parabolic interpolation for frequency identification, and a ratio-based detection approach to determine loss-of-lock, balancing compensation range and accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If existing detection methods (carrier-to-noise ratio, correlator output power, phase-locked loop I/O output vector jitter, frequency-locked loop jitter) are used, then the receiver can detect loss-of-lock conditions, but these methods cannot effectively overcome the influence of signal attenuation and interference in indoor and urban environments

Engineering Contradiction:

Improveloss-of-lock detection accuracyVSAvoidsignal attenuation and interference

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent segments the detection process into multiple independent components: carrier frequency offset estimation, frequency compensation, coherent integration, non-coherent integration, and ratio-based detection. Each component processes specific aspects of the signal separately, allowing the system to handle attenuated and interfered signals more effectively by combining results from multiple processing stages rather than relying on a single detection metric

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces frequency compensation as an intermediary step between signal reception and loss-of-lock detection. By estimating and compensating for carrier frequency offset before performing integration and detection, the system eliminates a major source of detection error that plagues conventional methods, thereby improving reliability in challenging environments

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If multi-channel frequency compensation with parabolic interpolation is performed, then carrier tracking accuracy is improved, but computational complexity increases

Engineering Contradiction:

Improvecarrier tracking accuracyVSAvoidcomputational complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent performs frequency compensation on multiple channels (excessive action) to ensure accurate carrier frequency offset correction, then uses parabolic interpolation to precisely identify the peak frequency. This level of computational effort exceeds what a single-channel method would require, but it significantly improves carrier tracking accuracy by thoroughly searching the frequency domain and accurately locating the signal peak

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The system uses the results from frequency identification to guide subsequent tracking operations. The estimated carrier frequency offset feeds back into the tracking loop to adjust the local oscillator frequency, creating a closed-loop system that continuously refines carrier tracking accuracy based on detected signal characteristics

Inventive Principle:

Principle #23Feedback

3Measurement precision

If coherent integration and non-coherent integration are used to improve signal-to-noise ratio, then signal sensitivity is enhanced, but processing time increases

Engineering Contradiction:

Improvesignal sensitivityVSAvoidprocessing time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent employs periodic coherent integration over fixed time intervals, followed by non-coherent integration of multiple coherent integration results. This periodic structure allows the system to accumulate signal energy over time to improve sensitivity while maintaining a regular processing rhythm that prevents excessive delay. The method balances integration duration against real-time requirements by using standardized integration periods

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS11635525B2Method for detecting loss-of-lock of a GNSS signal tracking loop based on frequency compensation

Publication Date: 2023.04.25 NANJING LOW POWER IC TECH INST CO LTD

AI summary

A method is for detecting loss-of-lock of a GNSS (Global Navigation Satellite System) signal tracking loop based on frequency compensation, comprising the following steps of: performing multi-channel frequency compensation on I-channel and Q-channel signals after down-conversion, pseudo-code stripping and integration clearing; then, performing coherent integration and non-coherent integration for a fixed time, and taking a maximum value of non-coherent integration results as a signal value; performing parabolic interpolation frequency identification, and taking an average value of the non-coherent integration results with the frequency differences of +/−50 Hz and +/−100 Hz as a noise value; and finally, calculating a ratio of the signal value to the noise value, and performing loss-of-lock detection with the ratio as a detection volume.