Bit Synchronizer Using Trajectory Mid-Point Rotation

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Solution Overview

Problem

Higher order modulations in digital communication systems require oversampling, leading to reduced symbol rates and performance, as existing technologies struggle to accurately detect symbol timing errors without increasing sample rates.

Innovation Solution

A communications device with a bit synchronization circuit that uses trajectory mid-point rotation to detect symbol timing errors, allowing for symbol timing error detection with only two samples per symbol, applicable to any order modulation, and combining a generic carrier phase error detection circuit for improved performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If oversampling is used for higher order modulations, then symbol timing error detection accuracy is improved, but symbol rate decreases and system performance deteriorates

Engineering Contradiction:

Improvesymbol timing error detection accuracyVSAvoidsymbol rate

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent changes the parameter of sampling rate from oversampling to two samples per symbol, and introduces a new parameter - trajectory mid-point rotation - to maintain detection accuracy at the lower sampling rate

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent focuses computational effort on critical points (mid-points of trajectories between constellation points) rather than uniformly processing all samples, achieving accurate timing error detection at specific locations without requiring high overall sampling rates

Inventive Principle:

Principle #3Local quality

2Device complexity

If two samples per symbol are used, then device complexity is reduced, but symbol timing error detection accuracy for higher order modulations deteriorates

Engineering Contradiction:

Improvesampling circuit complexityVSAvoidsymbol timing error detection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent moves from time-domain sampling analysis to geometric trajectory analysis in the complex plane, using rotational transformation to extract timing information from the mid-points of constellation point trajectories

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent introduces trajectory mid-point rotation as an intermediary computational step that transforms the relationship between two samples and the timing error, enabling accurate detection without requiring additional samples

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS8976907B2Bit synchronizer for detecting symbol timing error for high order modulation using a trajectory mid-point rotation and related methods

Publication Date: 2015.03.10 HARRIS CORP

AI summary

A communications device includes an input that receives a communications signal having in-phase (I) and Quadrature (Q) signal components. A bit synchronization circuit detects the symbol timing error in the communications signal and includes a symbol mapper circuit configured to receive I and Q signal components and determine transition samples of vectors within the signal constellation. A rotation generator circuit is coupled to the symbol mapper circuit and configured to rotate the trajectory of the transition samples at their midpoints to determine the symbol timing error.