NFC Synchronization Circuit for Spurious Tone Suppression
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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, counter-divider, frequency matching circuit, and sigma-delta modulation, clocked by a higher frequency clock signal to reduce spurious tones and improve oscillator control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the oscillator is controlled analogically or digitally with comparison clocked by reference frequency, then the device can generate synchronized carrier signals, but spurious tones appear in the output signal degrading communication quality
Solution Approach 1:
The patent applies dynamics by making the comparison clock frequency variable rather than fixed. The comparison clock is derived from the oscillator signal itself through a frequency divider, creating a dynamic relationship where the comparison frequency adapts to the oscillator frequency. This dynamic approach eliminates the fixed-frequency spurious tones that occur when using a static reference frequency for comparison, thereby improving communication quality by removing harmful spectral components.
2Reliability
If the oscillator frequency is varied with each clock stroke of the reference frequency signal, then synchronization is achieved, but the output signal becomes noisy with spurious tones
Solution Approach 1:
The patent introduces an intermediary element: a frequency divider that derives the comparison clock from the oscillator signal itself rather than using the external reference frequency directly. This intermediary transformation creates a comparison clock that is phase-related to the oscillator but at a different frequency, allowing synchronization to be achieved without directly modulating the oscillator with the reference frequency, thereby eliminating spurious tones while maintaining synchronization.
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, enhancing signal readability and responsiveness, resulting in a cleaner and more efficient near-field communication.
Implementation Method 1
A synchronization circuit with a phase-locked loop that includes a digitally controlled oscillator, counter-divider, frequency matching circuit, and sigma-delta modulation
Implementation Method 2
counter-divider
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.