Multiplexing Read and Fly Height Signals to Shared Transmission Line
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Solution Overview
Problem
Current disk drive technologies face challenges in accurately detecting defects on disk surfaces, particularly thermal asperities, due to limitations in fly height signal processing and multiplexing, which affects the reliability of data storage and retrieval operations.
Innovation Solution
The integration of a fly height sensor and multiplexer within the control circuitry allows for multiplexing of read and fly height signals over a single transmission line, enabling the use of a sampling device and buffer to process both signals, and employing techniques such as threshold comparison, slope detection, and defect filtering to identify defects, while also adjusting dynamic fly height settings for optimal defect scanning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate transmission lines are used for read signal and fly height signal, then signal transmission reliability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines the read signal transmission line and fly height signal transmission line into a single shared transmission line. A multiplexer is implemented to time-division multiplex the two signals, allowing them to share the same physical transmission medium. This reduces the number of transmission lines required, simplifying the overall device structure and reducing manufacturing complexity while maintaining signal transmission reliability through proper signal isolation and timing management.
Solution Approach 2:
The transmission line is designed to serve dual purposes: transmitting both the read signal from the read element and the fly height signal from the fly height sensor. The multiplexer enables this universal transmission line to dynamically switch between carrying different signal types based on operational requirements, thereby reducing the total number of dedicated transmission lines needed in the system.
2Measurement precision
If multiple separate circuits are used for read signal processing and fly height signal processing, then signal processing accuracy is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent merges the read signal processing circuit and fly height signal processing circuit into a single integrated control circuitry block. A multiplexer is implemented within the control circuitry to time-division multiplex the two input signals, allowing a single set of processing resources to handle both signal types. This integration reduces the number of separate circuits required, simplifying the control architecture while maintaining processing accuracy through dedicated processing paths for each signal type within the unified circuitry.
3Reliability
If dedicated transmission lines are used for each signal, then signal interference is reduced, but manufacturing cost and device complexity increase
Solution Approach 1:
The patent consolidates multiple dedicated transmission lines into a single shared transmission line using time-division multiplexing. The multiplexer switches between connecting the read element and the fly height sensor to the same transmission line at different time intervals. This approach maintains signal integrity by ensuring that only one signal is present on the transmission line at any given time, thereby preventing interference, while simultaneously reducing manufacturing complexity and cost by requiring fewer physical transmission lines.
Data Source
AI summary
A disk drive is disclosed comprising a disk comprising a plurality of servo tracks defined by servo sectors, and a head actuated over the disk, wherein the head comprises a read element operable to generate a read signal. The disk drive further comprises a fly height sensor operable to generate a fly height signal for the head, and control circuitry comprising a multiplexer operable to multiplex the read signal and the fly height signal to a transmission line. The multiplexer is configured to select the read signal when reading the servo sectors of a servo track, and configured to select the fly height signal when reading a segment of the servo track between consecutive servo sectors.