Sampling Frequency Offset Estimation via Multi-Frame Waveform Variation
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Solution Overview
Problem
Existing methods for estimating sampling frequency offset have limited estimation ranges, making it difficult to accurately correct sampling timing errors, especially when the offset exceeds the possible estimation range, leading to unreliable sampling timing recovery in broadcasting and communication systems.
Innovation Solution
A method and apparatus that estimate sampling frequency offset using a waveform characteristic variation quantity among frames, incorporating a waveform characteristic extraction unit, variation quantity calculation unit, and SFO estimator, which detect peaks in a training sequence period, calculate waveform characteristic variation, and correct sampling timing errors through a sampling timing recovery loop with an interpolator, loop filter, and controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional sampling frequency offset estimation methods are used, then the estimation process is simple, but the estimation range is limited and accuracy deteriorates when offset exceeds the estimation range
Solution Approach 1:
The patent transitions from single-frame waveform analysis to multi-frame waveform characteristic comparison. By analyzing waveform characteristics across multiple frames (current frame and previous frame) and calculating variation quantities between them, the system extends the estimation range beyond conventional single-frame methods while maintaining accuracy through inter-frame comparison.
Solution Approach 2:
The patent performs preliminary waveform characteristic extraction and storage for previous frames before calculating variation quantities. The waveform characteristic values from previous frames are stored and prepared in advance, enabling rapid and accurate SFO estimation when variation quantities are calculated by comparing with current frame characteristics.
2Reliability
If sampling frequency offset is not corrected, then the system operation is simple, but sampling timing error accumulates leading to digital data signal accuracy deterioration
Solution Approach 1:
The patent implements a feedback-based sampling timing recovery loop where the estimated SFO is fed back to adjust the sampling clock frequency. The controller receives SFO estimation results and generates control signals to adjust the sampling clock, creating a closed-loop system that continuously corrects sampling timing errors and maintains digital data signal accuracy.
Solution Approach 2:
The patent replaces direct hardware-based sampling clock adjustment with a software/control-based approach. The SFO estimator and controller use digital signal processing and control algorithms to calculate and apply frequency corrections, substituting complex hardware adjustment mechanisms with more flexible software-based control while achieving the same timing recovery function.
Data Source
AI summary
An apparatus for estimating a sampling frequency offset includes a waveform characteristic extraction unit, a variation quantity calculation unit, and a SFO (sampling frequency offset) estimator. The waveform characteristic extraction unit extracts a waveform characteristic of a training sequence period in one frame period of a sample data signal and outputs a waveform characteristic value corresponding to the waveform characteristic of the training sequence period. The variation quantity calculation unit calculates a waveform characteristic variation quantity representing a variation quantity in waveform characteristic between an m-th frame and an (m−k)-th frame based on a waveform characteristic value in the m-th frame and a waveform characteristic value in the (m−k)-th frame, where m and k are independently integers of 1 or more. The SFO estimator estimates an SFO of the sample data signal based on the waveform characteristic variation quantity.