NFC Clock Recovery with LC Tank Energy Neutralization
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Solution Overview
Problem
In Near Field Communication (NFC) Card Emulation Mode, especially with Active Load Modulation, the residual power in the LC tank after transmission disturbs clock recovery, leading to stability issues due to phase errors and frequency drift, affecting communication distance and reliability.
Innovation Solution
The system employs an equalizer or neutralizer to dissipate or neutralize the residual energy in the LC tank by short-circuiting or injecting a signal with a different phase at the end of the modulation period, ensuring no phase error is introduced during clock recovery, thereby stabilizing the phase-locked loop and maintaining accurate frequency and phase locking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If active load modulation is used to transmit data in NFC Card Emulation Mode, then data transmission capability is improved, but residual power in the LC tank causes phase errors and frequency drift during clock recovery
Solution Approach 1:
The patent extracts and removes the harmful residual power from the LC tank by introducing a neutralizer circuit that generates an opposing signal to cancel out the residual energy, thereby eliminating the source of phase errors and frequency drift while maintaining data transmission capability
Solution Approach 2:
The patent applies preliminary anti-action by using an equalizer circuit to pre-dissipate or equalize the residual power in the LC tank before clock recovery begins, preventing phase errors and frequency drift from occurring in the first place
2Use of energy by moving object
If residual power is allowed to remain in the LC tank after transmission, then energy efficiency is improved, but phase errors and frequency drift occur during clock recovery
Solution Approach 1:
The patent converts the harmful residual power into a beneficial state by using the neutralizer to cancel it out, transforming what would be a source of error into a clean state that enables accurate clock recovery while maintaining reasonable energy efficiency through controlled dissipation
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 approach effectively reduces residual energy in the LC tank, preventing phase errors and maintaining stable clock recovery, which enhances communication reliability and extends communication distance by ensuring proper phase and frequency alignment with the reader.
Implementation Method 1
NFC uses magnetic induction between two loop antennas located within each other's near field, effectively forming an air-core transformer
Implementation Method 2
The system employs an equalizer or neutralizer to dissipate or neutralize the residual energy in the LC tank by short-circuiting or injecting a signal with a different phase at the end of the modulation period
Data Source
AI summary
A system includes a tank circuit, a synchronization circuit, a transmitter, and a control circuit. The tank circuit is configured to receive a first signal transmitted from a near field communication reader. The synchronization circuit is configured to synchronize a clock to the first signal. The transmitter is configured to transmit data using the clock from the tank circuit to the near field communication reader using active load modulation. The control circuit is configured to disable the synchronization circuit during a modulation period of the active load modulation and to reduce energy remaining in the tank circuit at an end of the modulation period.