Stacked Reader Elements for High Resolution and SNR
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Solution Overview
Problem
Current magnetic read heads face limitations in achieving improved signal-to-noise ratio (SNR) and resolution due to material constraints, particularly in the down-track and cross-track directions, as gains from film stack improvements and reduced shield-to-shield spacing are nearing material limits.
Innovation Solution
The implementation of two stacked reader elements within the same read gap, with asymmetric output waveforms from each element, combined using equalizer settings and waveform algorithms to enhance resolution and SNR, while maintaining a larger shield-to-shield spacing to accommodate both elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If shield to shield spacing is reduced to improve resolution, then reader resolution improves, but material limits are reached and further improvement is difficult
Solution Approach 1:
The read head is divided into multiple independent reader elements (first reader element and second reader element) that can be stacked vertically. Each reader element has its own sensor structure and shield layers, allowing independent optimization of each element while maintaining overall system performance. This segmentation enables continued improvement of resolution without being constrained by the material limits of a single reader element's film stack.
2Reliability
If multiple reader elements are stacked to improve SNR, then signal-to-noise ratio improves, but device complexity increases
Solution Approach 1:
Multiple reader elements are merged into a single read head structure, with the first reader element and second reader element positioned at different vertical locations between the same shield layers. The outputs of these elements are combined through signal processing to achieve noise averaging and improved SNR. This merging approach allows the system to benefit from multiple sensors without requiring separate independent read head assemblies.
3Measurement precision
If reader elements are placed closer together to improve resolution, then down-track resolution improves, but cross-track resolution and signal processing complexity increase
Solution Approach 1:
The reader elements are positioned asymmetrically within the read gap, with the first reader element located at a first position and the second reader element at a second position. This asymmetric placement creates asymmetric output waveforms that can be compensated for through equalizer settings in the signal processing circuit. The asymmetric configuration allows the elements to be closer together for improved down-track resolution while the signal processing algorithm handles the resulting waveform characteristics.
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 configuration achieves similar or better resolution and higher SNR compared to a single read element in a smaller gap, with up to 3 dB of SNR gain, by optimizing the distance between free layers and shields, thereby improving reading capabilities in magnetic recording.
Implementation Method 1
a first sensor element disposed between the first shield layer and the second shield layer; and a second sensor element, separate and distinct from the first sensor element, disposed between the first shield layer and the second shield layer
Data Source
AI summary
The present invention generally relates to a read head in a magnetic recording head. The read head utilizes two reader elements that are stacked in the down track direction within the same read gap to improve resolution and SNR by combining the signals from the two reader elements. The output waveform from each read element is asymmetric in the down track direction; however, by use of equalizer settings and waveform combining the algorithm in signal processing, the combined waveform has a similar or better resolution and higher SNR compared to a single read element in a smaller read gap.