Cash Note Anti-Counterfeiting Signal Sampling with Interference Cancellation
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Solution Overview
Problem
Automatic teller machines and cash note counting/sorting machines face interference from power-frequency and low-frequency electromagnetic signals, leading to incorrect identification of anti-counterfeiting information due to susceptibility of high-sensitivity magnetic sensors, which complicates signal processing and increases resource consumption.
Innovation Solution
A sampling method and apparatus that calculates a response ratio coefficient to differentiate between effective and interference signals, allowing for common-mode signal elimination and restoration of accurate anti-counterfeiting information by multiplying interference signals with the coefficient, thereby eliminating spatially coupled electromagnetic interferences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-sensitivity magnetic sensors and fine amplifying circuits are used to detect weak magnetic anti-counterfeiting information, then measurement precision is improved, but the system becomes susceptible to power-frequency electromagnetic interference
Solution Approach 1:
The patent applies common-mode rejection technique to convert the harmful power-frequency interference signals into a useful cancellation mechanism. By treating identical interference signals received by multiple sensors as a common-mode component, the system subtracts these interference signals to extract the genuine anti-counterfeiting information, effectively converting the harmful interference into a removable common-mode component.
Solution Approach 2:
The patent introduces differential signal processing as an intermediary mechanism between the magnetic sensors and the detection system. By using differential amplifiers and signal subtraction operations, the system creates an intermediate processing stage that eliminates power-frequency interference while preserving the weak magnetic anti-counterfeiting signals.
2Object-affected harmful factors
If complicated software algorithm and FFT transform are used to eliminate power-frequency interference, then interference elimination capability is improved, but device complexity and resource consumption increase
Solution Approach 1:
The patent extracts the power-frequency interference component from the total signal by using multiple sensors to capture identical interference patterns. Through differential subtraction, the interference component is separated and removed, leaving only the genuine anti-counterfeiting magnetic signals without requiring complex FFT transforms or advanced software algorithms.
Solution Approach 2:
The patent combines signals from multiple magnetic sensors through differential addition/subtraction operations. By merging the sensor outputs in a differential configuration, the system achieves interference cancellation while maintaining simplicity, avoiding the need for complex individual signal processing for each sensor.
3Object-affected harmful factors
If shielding material is added to resist low-frequency electromagnetic interference, then interference resistance is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces the mechanical/physical shielding approach with an electronic signal processing solution. Instead of using shielding materials to block electromagnetic interference, the system uses differential signal processing and common-mode rejection techniques to electronically eliminate interference, avoiding the cost and complexity of physical shielding structures.
4Measurement precision
If power-frequency signals are extracted from mains supply for interference cancellation, then interference signal accuracy is improved, but circuit complexity increases due to phase compensation requirements
Solution Approach 1:
The patent enables the system to self-generate the reference interference signal by having multiple sensors naturally capture the power-frequency interference present in the environment. The system uses the actual captured interference signals from the sensors themselves as the reference, eliminating the need for external mains supply extraction and complex phase compensation circuits.
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 effectively eliminates power-frequency and low-frequency electromagnetic interferences, ensuring accurate identification of cash notes without significant impact on processing time or resource consumption, enhancing the reliability of financial equipment.
Implementation Method 1
a plurality types of magnetic sensors with high sensitivity to detect anti-counterfeiting information of bank notes
Implementation Method 2
a fine amplifying circuit with low noise and extremely high magnification is needed to detect the magnetic information
Implementation Method 3
interference signals coupled in the magnetic sensor by space coupling
Data Source
Figure 1~2
Figure 3
AI summary
Disclosed are a sampling method for anti-counterfeiting information about a cash note, and a sampling apparatus for anti-counterfeiting information about a cash note, which executes the method. The sampling method for anti-counterfeiting information about a cash note comprises: through differences collected between sensors, utilizing a law of the differences to restore spatially coupled power-frequency of low-frequency electromagnetic interference signals acquired by an effective signal sensor (21); and then performing common-mode signal elimination on voltage waveform data corresponding to the anti-counterfeiting information, thereby thoroughly elimination the spatially coupled power-frequency or low-frequency electromagnetic interferences that magnetic signal sensors suffer from during the collection of magnetic anti-counterfeiting signals.