RF Carrier Phase Alignment via Baseband LO 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 Ethernet-based solutions like PTP are not always feasible due to environmental constraints, necessitating an alternative 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 achieve accurate RF carrier synchronization and phase alignment, utilizing the characteristics of quadrature modulated signals to compensate for frequency offsets, thereby eliminating the need for external synchronization sources like GPS or Ethernet connectivity.

Engineering Contradictions & Design Principles

VSEngineering 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

Engineering Contradiction:

Improvesynchronization accuracyVSAvoidcost and availability

Core Design Contradiction:

Measurement precisionVSDevice complexity

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, eliminating the need for external GPS receivers

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent uses the received RF carrier signal as an intermediary to transfer timing information from macro base stations to microcell base stations, enabling synchronization without direct GPS access

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If PTP-based synchronization is used, then synchronization accuracy is improved, but adaptability decreases due to wired Ethernet requirement

Engineering Contradiction:

Improvesynchronization accuracyVSAvoidenvironmental adaptability

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent replaces the mechanical/wired Ethernet connection requirement with a wireless RF-based synchronization method, allowing microcell base stations to achieve precise synchronization without physical wired access

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If local oscillator frequency is increased for better synchronization, then measurement precision is improved, but frequency offset errors increase

Engineering Contradiction:

Improvesynchronization accuracyVSAvoidfrequency stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent implements a feedback mechanism where cumulative phase measurements are continuously determined from baseband signals and used to generate correction signals that adjust for local oscillator frequency offsets, maintaining long-term frequency stability

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system performs preliminary frequency locking by determining cumulative phase measurements over time before applying correction signals, ensuring accurate frequency synchronization

Inventive Principle:

Principle #10Preliminary action

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 achieves carrier synchronization accuracy of 0.1 parts per million (100 ppb) for coarse synchronization and better than 1 part per billion (<1 ppb) for precise synchronization, enabling microcell base stations to serve as primary clock and timing references for connected networks, facilitating economical high-volume 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 having an LO frequency

Methodology Applied

Scientific EffectMixing:

Implementation Method 2

determining a cumulative phase measurement associated with baseband signal samples having a baseband signal magnitude greater than a threshold

Methodology Applied

Scientific EffectPhase measurement:

Implementation Method 3

applying a correction signal to compensate for an LO frequency offset of the LO frequency based on the cumulative phase

Methodology Applied

Scientific EffectFrequency correction:

Data Source

PatentUS9048980B2RF carrier synchronization and phase alignment methods and systems

Publication Date: 2015.06.02 PHASORLAB INC

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.