Servo Signal Recording on Magnetic Tape Using AC Erasing
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Solution Overview
Problem
Existing methods for recording servo signals on magnetic tapes, such as DC-erasing, fail to control the output level of servo signals effectively, leading to saturation or inadequate signal-to-noise ratios, and require complex apparatus configurations, which hinder normal reproduction and reduce data track signal quality.
Innovation Solution
A servo signal recording method using an AC erasing head with a pulse having a varied duty ratio, where the driving time for one polarity is longer than the other, allowing for enhanced servo signal reproduction output without compromising data signal quality, and a simplified apparatus configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If DC-erasing is performed to enhance servo signal output level, then the servo signal output level increases, but the output level cannot be controlled and becomes fixed at 2Vo
Solution Approach 1:
The patent applies dynamics by making the erasure method adaptable and controllable. Instead of fixed DC-erasing, the system uses AC-erasing with variable duty ratios that can be dynamically adjusted to control the servo signal output level according to different reproduction requirements, transforming a static process into a dynamic one.
Solution Approach 2:
The patent changes the parameter of erasure method from DC-erasing to AC-erasing with variable duty ratios. By adjusting the duty ratio parameter of the AC erasing pulse, the system can control the degree of magnetization reversal and thereby control the servo signal output level, achieving adaptability across different specifications.
2Power
If servo signal output level is increased beyond specification, then signal strength improves, but magnetic head saturation occurs
Solution Approach 1:
The patent implements feedback control by measuring the reproduction output level of the servo signal and adjusting the AC erasing duty ratio accordingly. When the output level exceeds the specification range, the system reduces the duty ratio to lower the magnetization strength, thereby preventing head saturation and ensuring reliable reproduction.
Solution Approach 2:
The system dynamically adjusts the AC erasing duty ratio based on the measured reproduction output level, creating a closed-loop control mechanism that adapts the servo signal strength to match specification requirements, preventing both saturation and insufficient signal levels.
3Power
If servo signal output level is decreased below specification, then head saturation is avoided, but signal-to-noise ratio becomes inadequate
Solution Approach 1:
The feedback mechanism monitors the reproduction output level and adjusts the AC erasing duty ratio to maintain the servo signal within the specification range, ensuring the signal-to-noise ratio remains adequate for reliable reproduction while avoiding head saturation.
Solution Approach 2:
By precisely controlling the AC erasing duty ratio parameter, the system optimizes the magnetization strength to achieve the minimum required servo signal output level that maintains adequate signal-to-noise ratio without exceeding specification limits.
4Power
If entire tape including data track is DC-erased to enhance servo signal, then servo signal output increases, but data track signal-to-noise ratio decreases
Solution Approach 1:
The patent applies local quality by performing AC-erasing selectively on the servo band rather than the entire tape including data tracks. This localized erasure enhances the servo signal output while leaving the data track magnetization intact, thereby maintaining the signal-to-noise ratio of recorded data.
Solution Approach 2:
The system extracts the servo band from the data track for selective AC-erasing treatment. By isolating and treating only the servo band with AC-erasing at appropriate duty ratios, the system enhances servo signal output without adversely affecting the data track signal quality.
5Adaptability or versatility
If AC erasing head is rotated to control DC erasure as disclosed in JP 2005-63623 A, then servo signal output level can be controlled, but apparatus size increases
Solution Approach 1:
The patent replaces the mechanical rotation system of the AC erasing head with an electrical control system that adjusts the duty ratio of AC erasing pulses. This substitution eliminates the need for mechanical rotation mechanisms while achieving the same goal of controlling servo signal output level, thereby reducing apparatus size.
Solution Approach 2:
Instead of changing the physical orientation of the erasing head through rotation, the system changes the electrical parameter of the erasing pulse (duty ratio) to control the degree of magnetization reversal. This parameter-based control achieves adaptability without requiring mechanical movement or rotation mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method allows for adjustable servo signal reproduction output levels within specified ranges, ensuring normal reproduction and maintaining high signal-to-noise ratios for data tracks, while simplifying the apparatus configuration and reducing its size.
Implementation Method 1
an AC erasing head for AC-erasing an information recording signal recorded on a magnetic layer
Implementation Method 2
a pulse having a duty ratio varied so that a driving time of the AC erasing head with respect to one polarity is longer than a driving time thereof with respect to the other polarity
Implementation Method 3
a servo signal is recorded in the servo band so that magnetization is formed in a direction opposite to a direction of residual magnetization caused by the erasure
Data Source
AI summary
The present invention is a servo signal recording method for recording a servo signal on a magnetic tape having a data band and a servo band, wherein erasure is performed based on a pulse having a duty ratio varied so that a driving time of the AC erasing head with respect to one polarity is longer than a driving time thereof with respect to the other polarity, and then, the servo band is magnetized so as to have a magnetization direction opposite to magnetization direction caused by the erasure to record a servo signal in the servo band. According to this configuration, the influence of an information recording signal recorded on the surface of a magnetic recording medium on a reproduction output is reduced, whereby the reproduction output of a servo signal can be enhanced easily.