NFC Card Reader Low Frequency Magnetic Field Signal Control
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Solution Overview
Problem
Existing near field communication methods for mobile terminals require calibration due to varying RF signal attenuation across different devices, especially at 13.56 MHz frequency, making distance control and integration of NFC antennas into SIM or SD cards challenging.
Innovation Solution
A near field communication method using low frequency alternating magnetic signals with preset transmission parameters, allowing mobile RF devices to detect and amplify these signals to constant voltage thresholds, enabling effective distance control and transaction without calibration, by selecting a highest working frequency f0 that minimizes attenuation variance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If NFC technology uses 13.56 MHz frequency with inductance coil coupling mode, then data communication between card reader and card can be achieved, but the antenna area requirement increases and metal objects severely disturb receiving effect
Solution Approach 1:
The patent changes the operating frequency parameter from 13.56 MHz to lower frequencies (e.g., 6.78 MHz or below), which reduces the antenna area requirement while maintaining communication reliability. This parameter change fundamentally alters the relationship between frequency and antenna size, allowing compact card integration without sacrificing communication effectiveness.
Solution Approach 2:
The patent replaces the inductance coil coupling mode with magnetic field direct transmission mode. Instead of using complex coil coupling mechanisms that require large antenna areas, the system directly transmits magnetic fields from the card reader to the card, simplifying the mechanical structure and reducing antenna size requirements while eliminating metal object interference issues.
2Ease of manufacture
If NFC antenna is integrated into SIM or SD cards for mobile terminal payment, then terminal transformation is avoided, but the antenna size cannot be sufficient large for 13.56 MHz frequency
Solution Approach 1:
By changing the operating frequency to lower values, the patent enables sufficient magnetic field transmission with much smaller antenna areas that can fit within SIM or SD cards. This parameter change makes card integration feasible without requiring large antenna structures that would exceed card dimensions.
Solution Approach 2:
The patent replaces complex multi-turn antenna coils required for 13.56 MHz with simplified magnetic field transmission structures optimized for lower frequencies. This substitution enables direct integration into standard cards without requiring structural modifications to the card form factor.
3Reliability
If mobile terminals are calibrated to avoid RF signal attenuation variance, then communication range consistency is improved, but calibration complexity and time increase
Solution Approach 1:
The patent changes the operating frequency parameter to reduce sensitivity to terminal structural variations. By operating at lower frequencies with magnetic field direct transmission, the system achieves more consistent communication ranges across different terminals without requiring individual calibration, as the magnetic field penetration characteristics are more uniform across various terminal designs.
4Reliability
If card reader and card use 13.56 MHz frequency with load modulation mode, then signal transmission from card to card reader can be achieved, but the coupling coefficient requirement increases and antenna size increases
Solution Approach 1:
The patent replaces the load modulation mode with magnetic field direct transmission mode. Instead of requiring precise coil coupling and load modulation techniques that demand high coupling coefficients and complex circuit designs, the system directly transmits magnetic fields from the card to the card reader, simplifying the transmission mechanism and reducing device complexity while maintaining reliable signal transmission.
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
Enables reliable data communication distance control between mobile RF devices and card readers within a given scope without calibrating the terminals, ensuring consistent transaction performance across various mobile terminals.
Implementation Method 1
the card reader transmits low frequency alternating magnetic signals according to preset transmission parameters
Implementation Method 2
the mobile RF device receives and detects the low frequency alternating magnetic signals on every distance points
Data Source
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AI summary
The invention involves a method and system for short range communications. The method includes: a card reader transmitting a low-frequency time-varying magnetic field signal, the frequency of which is equal to or less than a highest frequency f0 at which the system does not require calibration for functioning, and the signal carrying identifier information of the card reader; a mobile radio frequency device receiving and detecting the low-frequency signal, and magnifying it to be a voltage signal, and determining whether a terminal enters an effective distance interval; if the voltage signal is greater than or equal to a voltage threshold Vt, then the terminal has entered the distance interval for effective card swiping, and obtaining the identifier information of the card reader, and transmitting its own identifier information together with the identifier information of the card reader to the card reader through a radio frequency channel; the card reader receiving the transmitted information, and comparing whether the identifier information in the transmitted information is consistent with the identifier information of its own, if it is consistent, then performing a card swiping transaction with the mobile radio frequency device through the radio frequency channel. This invention realizes that the data communicating distance between a radio frequency communication terminal including a mobile radio frequency device and a card reader can be controlled reliably within a specified range, and that the terminal needs not to be calibrated.