Spread Spectrum Clock Modulation for EMI Reduction
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Solution Overview
Problem
Existing spread spectrum clock technologies are ineffective in significantly reducing the maximum intensity of electromagnetic waves, which leads to electromagnetic interference (EMI) issues as communication speeds increase.
Innovation Solution
A method and device for spreading the frequency spectrum of a clock by frequency-modulating it using a non-repetitive modulation waveform, composed of modulation wave units with unique identifiers, to create a modulation profile that further disperses the energy spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a square wave clock of fixed frequency is used, then the clock signal is simple to generate and stable, but electromagnetic energy concentrates in a specific band causing EMI problems
Solution Approach 1:
The patent applies dynamics by making the clock frequency variable instead of fixed. The clock frequency is modulated around a nominal frequency F0 with a peak frequency deviation ΔF, creating a spread spectrum clock signal that dynamically changes frequency to disperse electromagnetic energy across a broader spectrum, thereby reducing EMI while maintaining signal integrity
Solution Approach 2:
The patent changes the frequency parameter of the clock signal from a fixed value to a dynamically varying value. By introducing frequency modulation with specific parameters (nominal frequency F0, peak deviation ΔF, modulation period TSSC), the clock signal's frequency spectrum is spread, which reduces peak electromagnetic energy density and mitigates EMI issues
2Productivity
If the communication speed is increased, then the data transmission efficiency is improved, but the electromagnetic energy becomes larger increasing EMI problems
Solution Approach 1:
The patent uses dynamic frequency modulation to allow higher communication speeds while controlling EMI. By continuously varying the clock frequency around F0 with deviation ΔF, the system can support higher data rates without concentrating electromagnetic energy in a single frequency band, thus improving productivity without proportionally increasing EMI harm
3Object-generated harmful factors
If the frequency of the clock is changed periodically around the nominal frequency, then the frequency spectrum is spread reducing peak energy, but the intensities of harmonic components only fluctuate without significant reduction in maximum intensity
Solution Approach 1:
The patent implements periodic frequency modulation where the clock frequency varies sinusoidally around the nominal frequency F0 with a modulation period TSSC. This periodic action creates a spread spectrum effect that distributes energy across multiple frequency components, and by optimizing the peak frequency deviation ΔF to be within a specific range (0.01-10% of F0), the patent achieves significant reduction in maximum electromagnetic intensity that overcomes the limitations of conventional spread spectrum approaches
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 lowers the maximum intensity of electromagnetic waves generated by the clock, reducing EMI and improving communication efficiency, even in systems with loop timing applied.
Implementation Method 1
a PLL (Phase-Locked Loop) configured to modulate and output a frequency of a clock used to synchronize communication data in accordance with a regulation signal applied thereto
Data Source
AI summary
A device according to the present disclosure includes: a PLL configured to modulate and output a frequency of a clock used to synchronize communication data in accordance with a regulation signal applied thereto, and a controller configured to generate the regulation signal according to a modulation waveform which is a successive form of a plurality of modulation wave units determined by a set modulation profiled, and apply the regulation signal to the PLL. The modulation wave unit is a signal whose sum of signal values during its time length becomes zero for the first time, and at least two successive modulation wave units among the plurality of modulation wave units differ from each other in at least one of the time length and the form of the signal.