Magnetic Write Head Dual Parallel Capacitor Impedance Compensation
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Solution Overview
Problem
The single capacitor design in write heads for magnetic hard disk drives leads to impedance misbalance, causing common-mode disturbances and crosstalk issues due to parasitic capacitance, which are harmful to the read element and limit data rate capabilities.
Innovation Solution
A dual parallel capacitor design is implemented, where two capacitors with balanced parasitic capacitance are connected in parallel with the write coil, each having a planar bottom and top plate with a dielectric layer in between, to balance the parasitic capacitance and reduce common-mode signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a single capacitor is added for transmission line compensation, then overshoot is provided to aid magnetization reversal speed, but impedance misbalance occurs causing common-mode disturbances and crosstalk
Solution Approach 1:
The single capacitor is segmented into two capacitors (first capacitor and second capacitor) that are electrically connected in parallel with the write coil. This segmentation balances the parasitic capacitance between the coil leads and substrate, eliminating common-mode disturbances and crosstalk while maintaining the overshoot effect for magnetization reversal speed enhancement.
2Speed
If write current overshoot is increased to overcome signal transmission losses, then magnetization reversal speed improves, but signal transmission losses and crosstalk problems worsen
Solution Approach 1:
The dual capacitor design provides a balanced parasitic capacitance that reduces common-mode signals and crosstalk, creating a more stable transmission environment. This feedback mechanism allows for more efficient signal transmission with reduced losses, enabling the magnetization reversal process to benefit from controlled overshoot without the detrimental effects of unbalanced parasitic capacitance.
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
The dual capacitor design effectively eliminates common-mode voltage spikes and crosstalk, enhancing the reliability and data rate capabilities of the write head by balancing the parasitic capacitance and improving signal transmission.
Implementation Method 1
a first capacitor and a second capacitor electrically connected in parallel with the write coil, wherein a parasitic capacitance between the bottom plate of each capacitor and a substrate positioned below the bottom plate exists during writing operations of the magnetic head, and wherein the parasitic capacitances of the capacitors are about balanced
Implementation Method 2
each capacitor including a planar bottom plate, a top plate positioned parallel to the bottom plate, and at least one dielectric layer positioned between the top plate and the bottom plate
Implementation Method 3
a write coil adapted for causing the write pole to emit a magnetic field upon excitation of the write coil
Implementation Method 4
Perpendicular magnetic recording, in which the recorded bits are stored in a perpendicular or out-of-plane orientation in the recording layer of a magnetic medium
Data Source
AI summary
In one embodiment, a magnetic head includes a write pole; a write coil adapted for causing the write pole to emit a magnetic field upon excitation of the write coil; and a first capacitor and a second capacitor electrically connected in parallel with the write coil, each capacitor including a planar bottom plate, a top plate positioned parallel to the bottom plate, and at least one dielectric layer positioned between the top plate and the bottom plate, wherein a parasitic capacitance between the bottom plate of each capacitor and a substrate positioned below the bottom plate exists during writing operations of the magnetic head, and wherein the parasitic capacitances of the capacitors are about balanced.