Contactless Device Signal Synchronization via Active Load Modulation
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Solution Overview
Problem
Current methods for synchronizing a reader carrier signal with a device carrier clock signal using active load modulation are inadequate when the device continuously generates its own electromagnetic field during transmission frames, leading to phase differences and increased power consumption.
Innovation Solution
A method involving a contactless communication device that processes the received reader signal to suppress the device's own carrier signal, allowing for synchronization between the processed signal and the device's carrier clock signal, using techniques like adaptive filtering and self-suppression algorithms to improve synchronization accuracy and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the device continuously generates its own electromagnetic field during transmission frames, then the signal strength is improved, but synchronization accuracy deteriorates due to phase differences
Solution Approach 1:
The patent extracts the device's own transmitted signal from the received signal using signal processing techniques. The received signal contains both the reader's carrier signal and the device's own modulated carrier signal. By detecting and removing the known transmitted signal components, the system isolates the reader's carrier signal for accurate synchronization, resolving the conflict between continuous transmission and synchronization accuracy.
Solution Approach 2:
The patent introduces an intermediary signal processing stage between signal reception and synchronization. This intermediary process uses adaptive filtering and signal subtraction to separate the reader's carrier signal from the composite received signal that includes the device's own transmission. This mediator enables accurate synchronization despite continuous electromagnetic field generation.
2Measurement precision
If synchronization is performed outside of transmission frames, then synchronization can be achieved, but power consumption increases due to external clock reference requirements
Solution Approach 1:
The patent implements self-service synchronization by using the device's own transmitted signal as a reference for synchronization. Instead of requiring an external clock reference during reception periods, the system uses its own modulated carrier signal, which is already being generated during transmission frames. This eliminates the need for continuous external clocking and reduces power consumption while maintaining synchronization accuracy.
Solution Approach 2:
The patent performs preliminary synchronization actions during transmission frames by continuously monitoring the phase relationship between the reader's carrier signal and the device's own carrier signal. This preliminary synchronization prepares the system for accurate demodulation and communication without requiring separate synchronization periods, thereby eliminating the need for external clock references during reception.
3Speed
If the device uses active load modulation to generate electromagnetic field, then communication range is improved, but signal interference increases making synchronization difficult
Solution Approach 1:
The patent converts the harmful effect of the device's own transmitted signal into a beneficial reference signal for synchronization. By using the known transmitted signal as a reference, the system can accurately determine the phase and frequency of the reader's carrier signal through comparison. The harmful interference becomes a useful synchronization aid, enabling accurate communication over extended ranges using 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
This approach enables effective synchronization of the reader and device carrier signals within transmission frames, reducing power consumption and maintaining synchronization accuracy despite continuous electromagnetic field generation by the device.
Implementation Method 1
an antenna configured to, during each reception period, receive a reader signal, and during each frame, receive a reader carrier signal and transmit to the reader a modulated device carrier signal
Implementation Method 2
a suppression processing of the modulated device carrier signal performed on an intermediate signal from that delivered by the antenna so as to obtain a processed signal
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The synchronization between the reader carrier signal (SA1) and the carrier clock signal (CLALM) generated within the device (CMP) includes within each transmission frame a suppression (5) of the modulated carrier signal (SPMR) transmitted to the reader.