CORDIC Position Error Signal Demodulation
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Solution Overview
Problem
Current systems for position error signal demodulation in disc drives face challenges in accurately and efficiently demodulating phase and amplitude components from servo burst signals, particularly in noisy environments and varying burst lengths, which affects the precision and speed of track seeking and following.
Innovation Solution
A circuit and method utilizing a CORDIC (COordinate Rotation Digital Computer) with sine and cosine weight look-up tables to generate demodulated phase and amplitude components from position error signal bursts, enabling robust phase control and adaptation to burst phase offsets, supporting various burst rates and lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional demodulation methods are used for position error signals, then the system structure is simpler, but the precision and speed of track seeking and following deteriorates
Solution Approach 1:
The patent replaces traditional mechanical or analog demodulation methods with a digital CORDIC (COordinate Rotation DIgital Computer) algorithm implemented in firmware or software. This substitution enables precise phase and amplitude demodulation of position error signals through iterative coordinate rotation calculations, achieving high measurement precision for track seeking and following while maintaining manageable system complexity through software-based implementation.
2Reliability
If conventional demodulation circuits are used, then the device complexity is lower, but the noise resilience deteriorates
Solution Approach 1:
The patent replaces conventional analog demodulation circuits with a digital signal processing approach using the CORDIC algorithm. This digital implementation provides superior noise resilience through iterative calculations that can filter and correct errors in the position error signal, achieving reliable demodulation in noisy environments while managing system complexity through efficient firmware implementation.
3Adaptability or versatility
If simple demodulation methods are used, then the processing speed is faster, but the adaptability to varying burst lengths deteriorates
Solution Approach 1:
The patent implements a dynamic demodulation system using the CORDIC algorithm that can adapt to varying burst lengths and phase offsets. The iterative nature of the CORDIC calculations allows the system to dynamically adjust to different servo burst configurations while maintaining processing efficiency. The algorithm's ability to rotate coordinates through iterative steps enables it to handle variable input conditions without requiring complete redesign for each scenario.
4Measurement precision
If high-precision demodulation is implemented, then the positioning accuracy is improved, but the computational complexity increases
Solution Approach 1:
The patent replaces complex high-precision mathematical computations with the CORDIC algorithm, which achieves high positioning accuracy through iterative coordinate rotations using only shift and add operations. This substitution eliminates the need for complex multiplication and division units, reducing hardware computational complexity while maintaining high measurement precision for position error signal demodulation.
Data Source
AI summary
A method may generate a demodulated sine component for a sequence of samples of a servo burst window of a position error signal using a sine weight look up table and generate a demodulated cosine component for the sequence of samples of the servo burst window of the position error signal using a cosine weight look up table. The sine weight and the cosine weight look up tables may have indexes representing a phase range. The method may generate a demodulated phase component signal and a demodulated amplitude component signal for the sequence of samples of the servo burst window of the position error signal based on the demodulated sine component and the demodulated cosine component using a Coordinate Rotation Digital Computer at least in part by iteratively rotating a vector based on the demodulated sine component and the demodulated cosine component and summing angular changes in the vector.