L5 GNSS Secondary Code Acquisition Without L1 Signal Aid
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Solution Overview
Problem
Conventional GNSS receivers face difficulties in acquiring secondary code phases of modern GNSS signals in the L5 band without first acquiring L1 signals, leading to duplication of radiofrequency components and limitations in coherent integration due to unknown secondary code phases.
Innovation Solution
A GNSS receiver architecture that acquires secondary code phases directly from L5 signals using an ADC, baseband sample memory, and a GNSS processing system, without relying on L1 signals, by detecting phase changes and averaging them to estimate frequency errors, and employing multiple discriminators for frequency lock loops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If L1 GNSS signals are acquired first to determine secondary code phase, then secondary code phase determination is reliable, but device complexity increases due to duplication of radiofrequency components
Solution Approach 1:
The patent extracts and removes the L1 signal acquisition requirement from the L5 signal processing chain. The receiver directly acquires L5 signals without needing L1 signals, eliminating the duplicate radiofrequency front end components while maintaining reliable secondary code phase determination through direct L5 correlation methods
Solution Approach 2:
The patent makes the L5 signal processing system self-sufficient by enabling it to perform both primary code acquisition and secondary code phase determination independently. The same radiofrequency front end that receives L5 signals is used for all processing functions, eliminating the need for separate L1 signal processing paths
2Device complexity
If secondary code phase is not determined, then hardware configuration is simplified, but coherent integration time is limited to 1 millisecond
Solution Approach 1:
The patent performs preliminary determination of secondary code phase through direct correlation of L5 signals with locally generated secondary code sequences. This preliminary action enables the system to establish the correct phase alignment before extending coherent integration beyond 1 millisecond, allowing longer integration times without requiring L1 signal assistance
Solution Approach 2:
The patent enables the L5 signal processing system to determine its own secondary code phase independently without external assistance from L1 signals. The system uses self-contained correlation methods that compare received L5 signals with locally generated references, allowing the receiver to autonomously achieve the phase information needed for extended coherent integration
3Device complexity
If L5 signals are acquired directly without L1 signals, then device complexity is reduced, but difficulty of detecting and measuring secondary code phase increases
Solution Approach 1:
The patent segments the L5 signal structure into primary code and secondary code components, processing them through separate but coordinated correlation paths. The primary code correlation provides initial signal detection and timing, while the secondary code correlation independently determines phase, breaking down the complex acquisition task into manageable segments that can be processed sequentially
Solution Approach 2:
The patent introduces an intermediary correlation process that bridges the gap between direct L5 signal reception and secondary code phase determination. The intermediary uses locally generated secondary code sequences as a reference to mediate the phase measurement, converting the difficult direct measurement problem into a manageable correlation-based detection process
Data Source
AI summary
Global navigation satellite systems and methods use L5 GNSS signals to acquire secondary code phases of those signals without using L1 GNSS signals to aid in the acquisition of secondary code phases. Various embodiments are described to perform this acquisition.