NFC Chip Phase Synchronization for Small-Antenna Load Modulation
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Solution Overview
Problem
Near-field communication (NFC) devices face challenges in synchronizing transmitted signals with carrier signals due to differences in clock signal sources, especially with smaller antennas and weaker coupling, which affects amplitude modulation and signal strength.
Innovation Solution
A near-field communication chip with a processing circuit, phase-locked loop, and phase alignment circuit that determines carrier frequency offsets and generates frequency control words to align clock signals, ensuring phase synchronization through active load modulation, even with smaller antennas and weaker coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive load modulation is used with larger antennas, then reliable amplitude modulation can be generated, but the antenna size cannot be reduced to adapt to limited space in mobile devices
Solution Approach 1:
The patent changes the modulation method from passive load modulation to active load modulation, where the NFC card device actively transmits synchronized signals instead of passively modulating the carrier. This parameter change allows smaller antennas to achieve sufficient modulation amplitude by using active transmission with power compensation
Solution Approach 2:
The patent introduces a phase synchronization mechanism as an intermediary between the NFC card reader's carrier signal and the NFC card device's transmitted signal. The synchronization circuit aligns the phase of transmitted signals with the carrier, enabling effective active load modulation with smaller antennas
2Area of moving object
If active load modulation is used with smaller antennas, then antenna size can be reduced, but phase synchronization between transmitted signal and carrier becomes difficult due to different clock signal sources
Solution Approach 1:
The patent implements a feedback-based phase synchronization mechanism where the NFC card device monitors the carrier signal from the NFC card reader and adjusts its transmitted signal phase accordingly. The synchronization circuit uses feedback from the carrier signal to maintain phase alignment despite different clock sources
Solution Approach 2:
The patent performs phase synchronization as a preliminary action before active load modulation transmission. The synchronization circuit pre-aligns the phase of the transmitted signal with the carrier signal, ensuring that when transmission begins, the phases are already synchronized, simplifying the overall process
3Reliability
If active load modulation is used to compensate for weaker coupling, then signal strength can be maintained, but power consumption increases
Solution Approach 1:
The patent applies partial active load modulation by transmitting synchronized signals only when necessary to maintain signal strength with smaller antennas. The system dynamically adjusts the transmission power level based on coupling conditions, using excessive power only when needed rather than continuously
Solution Approach 2:
The patent optimizes power consumption by changing transmission parameters such as power level and modulation depth based on detected coupling conditions. The system adjusts these parameters dynamically to maintain signal strength while minimizing power consumption during active load modulation
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 fast and precise synchronization of transmitted signals with carrier signals, improving signal strength and modulation amplitude, particularly in mobile devices with limited space and metal interference.
Implementation Method 1
The phase-locked loop is configured to generate a first clock signal based on the local clock signal and the first frequency control word FCW
Implementation Method 2
the ALM means that the NFC card device synchronously superimposes a transmitted signal (an active load modulation signal of the NFC card device) onto a carrier of the NFC card reader to generate amplitude modulation
Implementation Method 3
The NFC is actually a radio frequency identification (RFID) technology that operates at a high frequency of 13.56 MHz
Data Source
AI summary
The present disclosure relates to the field of communication technologies, and provide a near-field communication (NFC) chip, a phase synchronization method, and an electronic device, to quickly synchronize a transmitted signal of an NFC card device with a carrier of an NFC card reader. The NFC chip includes a processing circuit configured to: determine a first carrier frequency offset between a local clock signal and a carrier clock signal, and generate a first frequency control word based on the first carrier frequency offset. The carrier clock signal is determined based on a received signal received by the NFC chip. The NFC chip further includes a phase-locked loop configured to generate a first clock signal based on the local clock signal and the first frequency control word. The NFC chip also includes a phase alignment circuit configured to perform phase selection on the first clock signal based on the carrier clock signal to obtain a second clock signal, and send the second clock signal to a transmitter circuit.