Spread Spectrum Clock Modulation With Variable Frequency Shift Slope
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Solution Overview
Problem
Existing spread spectrum clock generators cannot perform SSC modulation with a variable slope of frequency shift, which is required for standards like USB4 during the training state, leading to incorrect link training due to large input frequency fluctuations in clock recovery circuits.
Innovation Solution
A spread spectrum clock generator with a modulation unit that can arbitrarily control the frequency shift and slope of the modulation waveform in any time section, allowing for SSC modulation of any frequency shift corresponding to specific standards, including USB4, by changing the slope over time and applying different spread methods like down spread, center spread, or upper spread.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed slope modulation waveform is used for SSC modulation, then the device structure is simple, but it cannot meet the USB4 standard requirement for variable slope during training state
Solution Approach 1:
The patent implements dynamic control of the modulation waveform by introducing a control signal that adjusts the slope of the triangular wave in real-time. The modulation waveform generation unit changes from a fixed structure to a dynamic one where the slope can be adjusted based on operational state (training vs steady-state), thereby meeting USB4 standard requirements without excessive complexity
Solution Approach 2:
The patent changes the parameter of the modulation waveform (slope of frequency shift) dynamically. During training state, the slope is set to a first value, and during steady-state, it switches to a second value. This parameter change approach enables compliance with USB4 standard while maintaining a relatively simple overall structure by only modifying the waveform parameters rather than the entire generation mechanism
2Reliability
If constant frequency shift is applied during training, then the modulation is simple, but it causes large input frequency fluctuations in clock recovery circuit
Solution Approach 1:
The patent applies dynamic frequency control where the frequency shift is not constant but varies according to the operational phase. During training, the frequency shifts with a controlled slope that is different from steady-state operation. This dynamic approach reduces abrupt frequency changes and prevents large fluctuations in the clock recovery circuit, improving link training reliability
Solution Approach 2:
The patent prepares the frequency modulation in advance by setting appropriate slope values before training begins. The system pre-configures the modulation waveform with a suitable slope that will gradually adjust the frequency during training, preventing sudden large fluctuations when training starts, thus easing the operational burden on the clock recovery circuit
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 accurate SSC modulation according to various standards, reducing input frequency fluctuations and ensuring correct link training by dynamically controlling the frequency shift and slope of the modulation waveform, and can be applied to future high-speed serial bus standards beyond USB4.
Implementation Method 1
a modulation unit configured to frequency-modulate the reference signal with the modulation waveform to generate a spread spectrum clock signal having any frequency shift and a slope of the frequency shift
Data Source
AI summary
Provided are a spread spectrum clock generator and a spread spectrum clock generation method, a pulse pattern generator and a pulse pattern generation method, and an error rate measuring device and an error rate measuring method capable of performing SSC modulation of any frequency shift according to a standard. Included are a reference signal generator 10 that generates a reference signal, a modulation waveform generator 20 that generates a modulation waveform, a modulation unit 30 that frequency-modulates the reference signal with the modulation waveform to generate an SSC modulated signal, and a modulation control unit 42a capable of arbitrarily controlling the frequency shift of the modulation waveform and a slope of the frequency shift in any time section.