Phase Offset Spectral Aliasing Compensation for Fly Height Control

Solution Overview

Problem

Existing methods for measuring fly height in storage devices are susceptible to errors due to inter symbol interference, leading to increased wear and potential crashes, as they require a larger operating range to account for measurement errors, resulting in excessive inter symbol interference.

Innovation Solution

The implementation of circuits and methods that utilize phase shifting and averaging of digital samples to mitigate spectral aliasing, allowing for more accurate fly height control by calculating the phase shift based on specific frequencies and using harmonic ratios to adjust fly height, thereby reducing spectral aliasing and improving sensitivity and resolution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the predetermined operating range of fly height is maintained sufficiently large to account for measurement errors, then measurement reliability is improved, but inter symbol interference becomes too high

Engineering Contradiction:

Improvemeasurement reliabilityVSAvoidinter symbol interference

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by pre-calculating and applying a phase shift to the analog input signal before ADC conversion. The phase shift amount is determined based on the sampling frequency and the frequency at which aliasing needs to be cancelled, as specified in the patent. This preliminary phase adjustment prevents spectral aliasing from occurring in the first place, rather than correcting it after the fact.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the phase parameter of the analog signal as a preprocessing step. By adjusting the phase of the analog input signal before conversion, the patent modifies the signal's spectral characteristics to eliminate aliasing components at specific frequencies, thereby improving measurement precision without requiring a larger operating range.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If spectral aliasing is fully eliminated through complex filtering, then measurement precision is improved, but device complexity increases

Engineering Contradiction:

Improvefly height measurement precisionVSAvoidanalog front-end circuit complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by pre-calculating and applying a phase shift to the analog input signal before ADC conversion. The phase shift amount is determined based on the sampling frequency and the frequency at which aliasing needs to be cancelled, as specified in the patent. This preliminary phase adjustment prevents spectral aliasing from occurring in the first place, rather than correcting it after the fact.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces complex mechanical/analog filtering systems with a simpler phase shift mechanism. Instead of using complex analog front-end filters to eliminate spectral aliasing, the patent uses a phase shift circuit that can be implemented with simpler electronics, followed by straightforward ADC conversion and digital processing.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If higher harmonic frequencies are used for measurement, then measurement precision is improved, but spectral aliasing increases

Engineering Contradiction:

Improveharmonic sensing precisionVSAvoidspectral aliasing

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary action by pre-calculating and applying a phase shift to the analog input signal before ADC conversion. The phase shift amount is determined based on the sampling frequency and the frequency at which aliasing needs to be cancelled, as specified in the patent. This preliminary phase adjustment prevents spectral aliasing from occurring in the first place, rather than correcting it after the fact.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the harmful effect of spectral aliasing into a beneficial outcome by using phase shifting to deliberately manipulate the spectral components. The phase shift causes aliasing components to cancel each other out at specific frequencies, transforming what would normally be a harmful interference into a useful cancellation effect that improves measurement accuracy.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS8345373B2Systems and methods for phase offset based spectral aliasing compensation

Publication Date: 2013.01.01 AVAGO TECHNOLOGIES INTERNATIONAL SALES PTE LTD

AI summary

Various embodiments of the present invention provide systems and methods for phase offset based spectral aliasing compensation. For example, a circuit for spectral aliasing reduction is disclosed that includes a phase shift circuit operable to phase shift an analog input signal and to provide a phase shifted analog signal; a first analog to digital converter circuit operable to provide a first series of digital samples corresponding to the analog input signal at a sampling frequency; a second analog to digital converter circuit operable to provide a second series of digital samples corresponding to the phase shifted analog signal at the sampling frequency; and an averaging circuit operable to average the first series of digital samples with the second series of digital samples to yield an average output.