Dual Servo Channel Gain Switching for Accurate Burst Positioning
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Solution Overview
Problem
Existing data storage devices face challenges in managing amplitude ratios across different portions of the servo pattern due to variations in read signal amplitudes, leading to ADC saturation or reduced resolution, and erroneous samples during gain switching in single-channel configurations.
Innovation Solution
Implementing dual channel burst gain switching, where different gain settings are used for different portions of the servo pattern, allowing parallel processing to combine signal values and reduce errors induced by gain switching settle time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single gain setting is used for the entire servo pattern, then the device complexity is reduced, but the measurement precision deteriorates due to ADC saturation or reduced resolution
Solution Approach 1:
The servo pattern is divided into multiple segments (preamble/sync region and burst region), and different gain settings are applied to each segment. This segmentation allows the ADC to operate at optimal resolution for each region, preventing saturation in high-amplitude burst regions while maintaining sufficient sensitivity in lower-amplitude preamble regions.
Solution Approach 2:
The gain setting is made dynamic by switching between different gain values at different time intervals during servo pattern reading. The system transitions from a static single-gain approach to a dynamic multi-gain approach, adjusting the gain based on the specific portion of the servo pattern being read.
2Measurement precision
If gain switching is implemented in a single channel, then the measurement precision is improved, but the reliability deteriorates due to erroneous samples during settle time
Solution Approach 1:
A dual-channel architecture is introduced where one channel serves as a backup and validator for the other. When one channel undergoes gain switching and experiences settle time errors, the other channel provides reliable samples. The system uses an intermediary validation mechanism where samples from both channels are compared and the reliable channel's data is selected.
Solution Approach 2:
The system changes the operational parameters of two parallel channels differently - one channel uses gain switching while the other maintains a fixed gain setting. This parameter differentiation allows the system to exploit the strengths of each configuration and compensate for their respective weaknesses.
3Measurement precision
If different gain values are used for different servo pattern portions, then the measurement precision is improved, but the device complexity increases due to multiple gain settings and switching control
Solution Approach 1:
The servo pattern is divided into multiple segments (preamble/sync region and burst region), and different gain settings are applied to each segment. This segmentation allows the ADC to operate at optimal resolution for each region, preventing saturation in high-amplitude burst regions while maintaining sufficient sensitivity in lower-amplitude preamble regions.
Solution Approach 2:
The gain setting is made dynamic by switching between different gain values at different time intervals during servo pattern reading. The system transitions from a static single-gain approach to a dynamic multi-gain approach, adjusting the gain based on the specific portion of the servo pattern being read.
4Measurement precision
If the ADC gain is increased to capture low amplitude signals, then the measurement precision for low amplitude signals is improved, but the reliability worsens due to saturation of high amplitude signals
Solution Approach 1:
The servo pattern is divided into multiple segments (preamble/sync region and burst region), and different gain settings are applied to each segment. This segmentation allows the ADC to operate at optimal resolution for each region, preventing saturation in high-amplitude burst regions while maintaining sufficient sensitivity in lower-amplitude preamble regions.
Solution Approach 2:
The system changes the operational parameters of two parallel channels differently - one channel uses gain switching while the other maintains a fixed gain setting. This parameter differentiation allows the system to exploit the strengths of each configuration and compensate for their respective weaknesses.
Data Source
AI summary
Example control circuitry, data storage devices, and methods to use dual servo channels for burst gain switching are described. The data storage device may include two servo channels, such as the dual channels in a two-dimensional magnetic recording channel, that receive read signals for the same servo sector in parallel. One channel is calibrated to use a gain value for a first portion of the servo pattern, such as the preamble and Gray code for the servo address mark, and the other channel is calibrated to use a different gain value for a second portion of the servo pattern, such as the burst pattern. The resulting signal values may then be combined to determine the position error signal. Both channels may be configured to use different gain values for different portions of the read signal with corresponding gain switching and combining them may use the most reliable portions of each signal.