Magnetoresistive Sensor Amplitude Decoding for Magnetic Stripe Readers
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Solution Overview
Problem
Conventional magnetic stripe readers face limitations in decoding magnetic stripes due to size and cost constraints, frequency-based decoding algorithms' sensitivity to speed and acceleration changes, and variability in magnet sizes, leading to reduced accuracy and reliability, especially when handling cards with variable data bit pitch and non-uniform magnet sizes.
Innovation Solution
A magnetic stripe reader utilizing a magnetoresistive sensor with amplitude-based decoding, capable of measuring magnetic field direction and amplitude, allowing for variable speed and acceleration during reading, and incorporating a processing module for extracting binary data using a combination of amplitude and frequency-based decoding methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If frequency-based decoding algorithm is used, then decoding can be performed with conventional magnetic reader head, but decoding accuracy deteriorates when card is swept at variable speeds or with acceleration changes
Solution Approach 1:
The patent changes the decoding parameter from frequency-based to amplitude-based. Instead of relying on the frequency of magnetic transitions which varies with sweep speed, the system measures the amplitude of the magnetic field signal. This amplitude measurement remains consistent regardless of sweep speed or acceleration, thereby resolving the contradiction between ease of operation and decoding reliability.
2Measurement precision
If conventional magnetic reader head with coil is used, then magnetic field can be detected, but device size and cost increase
Solution Approach 1:
The patent replaces the mechanical coil-based magnetic reader head with a magnetoresistive sensor. Instead of using electromagnetic induction through a coil and ferrite core, the system uses a solid-state magnetoresistive element that changes resistance in response to magnetic field strength. This substitution dramatically reduces device size and complexity while maintaining measurement precision.
3Power
If high number of copper wire turns is used in coil, then voltage output increases, but manufacturing complexity and cost increase
Solution Approach 1:
The patent eliminates the coil winding process entirely by replacing it with a magnetoresistive sensor. The voltage output is generated through changes in resistance of the magnetoresistive element rather than through electromagnetic induction requiring multiple wire turns. This substitution simplifies manufacturing while maintaining adequate signal output levels.
4Power
If tight gap control of 10μm is maintained in flux guide, then voltage output increases, but manufacturing precision requirements and cost increase
Solution Approach 1:
The patent replaces the flux guide and gap control mechanism with a magnetoresistive sensor that can be positioned closer to the magnetic stripe without requiring precise gap control. The solid-state sensor eliminates the need for complex flux guide structures and tight dimensional tolerances, thereby reducing manufacturing precision requirements while maintaining voltage output.
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 solution enhances decoding accuracy and reliability by enabling reading at variable speeds, recovering from stops, and tolerating magnetic stripe variations, resulting in improved performance and reduced failure rates, and enables the development of smaller, thinner, and more portable card readers.
Implementation Method 1
a magnetoresistive sensor (20) including a plurality of magnetoresistive elements (21)
Implementation Method 2
The MRH 100 typically comprises a coil 101, usually made of copper, a ferrite core 102, usually made of stacked sheets of iron (Fe)
Implementation Method 3
the coil output voltage V follows Faraday's law as shown by Equation (1): Where A is the area of the coil 101, B is the magnetic field
Data Source
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Figure 6~7
AI summary
The present disclosure concerns a reader device (10) for reading information stored on a magnetic strip containing a plurality of polarized magnets, each providing a magnetic flux, said reader device (10) comprising: a magnetoresistive sensor (20) including a plurality of magnetoresistive elements (21) and configured for reading the information stored on the magnetic strip and outputting a read signal (22); a processing module (12) configured for decoding the read signal (22) and extracting binary data (30); wherein the read signal (22) comprises amplitude information of the magnetic flux; and wherein the processing module (12) is further configured for decoding the read signal (22) using the amplitude information of the read signal (22). The present disclosure further concerns an amplitude decoding method for decoding the read signal (22) outputted by the reader device (10).