RF Carrier Synchronization via Baseband Phase Offset Correction
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Solution Overview
Problem
Conventional synchronization techniques for base stations, such as GPS-based methods, are either too expensive or unavailable for microcell base stations, and Precision Time Protocol (PTP) requires Ethernet connectivity, which may not always be available, necessitating an alternative method for accurate RF carrier synchronization and phase alignment.
Innovation Solution
The proposed method involves generating a baseband information signal by mixing a received modulated carrier signal with a local oscillator signal, determining cumulative phase measurements, and applying correction signals to compensate for frequency offsets, utilizing the characteristics of quadrature modulated signals to achieve accurate synchronization without external sources like GPS or Ethernet, using coarse and wide-range synchronization methods and precise narrow-range techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS-based synchronization is used in microcell base stations, then synchronization accuracy is improved, but cost increases and availability decreases in environments without GPS access
Solution Approach 1:
The microcell base station performs self-synchronization by using its received RF signals to generate baseband signals, determine cumulative phase measurements, and apply correction signals to compensate for local oscillator frequency offsets. This eliminates the need for external GPS receivers, making the system self-sufficient and adaptable to environments without GPS access while maintaining synchronization accuracy of 0.1 parts per million for coarse synchronization and better than 1 part per billion for precise synchronization.
2Measurement precision
If PTP based on IEEE 1588 is used for carrier synchronization, then synchronization accuracy is improved, but dependency on wired Ethernet access increases
Solution Approach 1:
The invention extracts the synchronization function from the external Ethernet network infrastructure and implements it directly within the microcell base station using its received RF signals. By taking out the dependency on wired Ethernet access and implementing self-contained phase measurement and correction mechanisms, the system achieves IEEE 1588-level synchronization accuracy while eliminating the complexity of wired Ethernet infrastructure requirements.
3Measurement precision
If microcell base stations use separate GPS receivers for synchronization, then synchronization accuracy is improved, but cost and device complexity increase
Solution Approach 1:
The microcell base station's existing RF receiving infrastructure is made multi-functional by using it not only for communication but also for synchronization. The same received RF signals that carry communication data are also used to generate baseband information signals for phase measurement. This universal use of existing components eliminates the need for separate GPS receivers, reducing device complexity and cost while maintaining high synchronization accuracy.
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
This approach enables highly accurate RF carrier synchronization and phase alignment, achieving accuracy better than 1 part per billion, suitable for 4G LTE networks, and allows microcell base stations to serve as a primary clock and timing reference for connected networks, facilitating economical deployment of small-cell base stations.
Implementation Method 1
generating a baseband information signal by mixing a received modulated carrier signal with a local oscillator (LO) signal
Implementation Method 2
determining a cumulative phase measurement associated with baseband signal samples and applying a correction signal to compensate for an LO frequency offset of the LO frequency based on the cumulative phase
Data Source
AI summary
A method comprising generating a baseband information signal by mixing a received modulated carrier signal with a local oscillator (LO) signal having an LO frequency; obtaining baseband signal samples of the baseband information signal having a baseband signal magnitude and a baseband signal phase; determining a cumulative phase measurement associated with baseband signal samples having a baseband signal magnitude greater than a threshold; and, applying a correction signal to compensate for an LO frequency offset of the LO frequency based on the cumulative phase.