NFC Synchronization Circuit for Spurious-Tone-Free Carrier Lock
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Solution Overview
Problem
Existing near-field communication devices suffer from spurious tones in the output signal due to analog or digital control of oscillators, which degrade communication quality.
Innovation Solution
A synchronization circuit with a phase-locked loop that includes a digitally controlled oscillator and a frequency matching circuit, clocked by a higher frequency clock signal, to synchronize and control the oscillator, reducing spurious tones and improving signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an analog or digital controlled oscillator is used to generate the carrier signal, then the oscillator can be servo-controlled to match the reference frequency, but spurious tones appear in the output signal degrading communication quality
Solution Approach 1:
The patent divides the phase-locked loop into two separate domains: a first domain clocked by the reference frequency signal that generates the carrier signal and frequency information, and a second domain clocked by a higher frequency clock signal that performs the frequency comparison and control. This segmentation prevents spurious tones from appearing at the carrier frequency while maintaining precise frequency matching capability.
2Productivity
If the phase-locked loop is clocked by the reference frequency signal, then the system operates at the carrier frequency, but the loop speed and responsiveness are limited
Solution Approach 1:
The patent introduces a second domain that operates at a higher frequency dimension (clocked by a clock signal with frequency higher than the reference frequency) to perform the frequency comparison and control operations. This allows the phase-locked loop to respond faster and achieve synchronization more quickly, while the first domain continues to generate the carrier signal at the reference frequency without spurious tones.
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
The solution effectively removes spurious tones from the carrier signal, enhancing communication readability and responsiveness by using a higher frequency clock to improve the phase-locked loop's speed and efficiency.
Implementation Method 1
A synchronization circuit with a phase-locked loop that includes a digitally controlled oscillator and a frequency matching circuit, clocked by a higher frequency clock signal, to synchronize and control the oscillator
Implementation Method 2
a first domain including a digitally controlled oscillator configured to generate a signal at a given frequency
Data Source
AI summary
A device is configured to receive a first carrier signal, and deliver a second carrier signal, and has a phase-locked loop including a first domain including an oscillator configured to generate a signal at a given frequency, and a circuit configured to generate information representative of the frequency of the signal generated by the oscillator, and to generate the second carrier signal and a clock signal, the first domain being clocked by the first carrier signal, a second domain, clocked by the clock signal, including a circuit configured to compare the frequency of the signal generated by the oscillator with the frequency of the first carrier signal and to control the oscillator, a matching circuit configured to transfer information representative of the frequency of the signal generated by the oscillator from the first domain to the second domain.