Spread-Spectrum Clock Generator With Feedback Phase Tracking
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Solution Overview
Problem
Traditional spread-spectrum clock signals for data transmission suffer from uncontrollable phase relationships, leading to unreliable data-establishing and data-maintaining times, making the system insecure for data transmission.
Innovation Solution
A circuit and method for generating spread-spectrum synchronous clock signals using a frequency locked loop, which includes a frequency detector with a fraction controller and a phase-shift controller to introduce phase delays, ensuring the second frequency tracks the first frequency within a broadened frequency boundary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional spread-spectrum clock signals are used for data transmission, then resistance to interference and noise is improved, but phase control becomes uncontrollable leading to unreliable data transmission
Solution Approach 1:
The patent implements a feedback mechanism by comparing the spread-spectrum clock signal with a reference clock signal and using the comparison result to adjust the phase of the spread-spectrum signal. This feedback loop enables controllable phase adjustment while maintaining the interference resistance benefits of spread-spectrum techniques, directly resolving the contradiction between reliability improvement and phase control difficulty
Solution Approach 2:
The patent changes the phase parameter of the spread-spectrum clock signal in a controlled manner by introducing a phase shift that is determined by the comparison between the spread-spectrum signal and reference clock. This parameter change enables reliable data transmission by ensuring proper phase alignment at the receiver while preserving the spread-spectrum interference resistance
2Reliability
If spread-spectrum clock signals with wider bandwidth are employed, then resistance to interference and noise is improved, but power flux density increases
Solution Approach 1:
The patent modifies the frequency parameter of the clock signal by spreading it across a wider bandwidth while controlling the power distribution. The spread-spectrum technique distributes the power flux density across multiple frequencies, reducing peak power density while maintaining total energy levels, thus resolving the contradiction between interference resistance and radiated energy
3Reliability
If phase shifts are introduced for spread-spectrum signals, then interference resistance is improved, but data-establishing and data-maintaining times become unreliable
Solution Approach 1:
The patent uses feedback by comparing the phase of the spread-spectrum clock signal with a reference clock signal and adjusting the phase shift accordingly. This ensures that data-establishing and data-maintaining times remain reliable even with spread-spectrum phase shifts, resolving the contradiction between jamming resistance and timing precision
Solution Approach 2:
The patent performs preliminary phase alignment by comparing the spread-spectrum signal with the reference clock before data transmission. This preliminary action ensures that the phase relationship is established in advance, guaranteeing reliable data timing while maintaining the benefits of spread-spectrum jamming resistance
Data Source
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AI summary
The present application discloses a circuit for generating spread-spectrum synchronous clock signal. The circuit includes a frequency detector comprising a fraction controller configured to compare an input signal of a first frequency with a feedback signal of a second frequency in a loop of feedback to generate a first control signal and a second control signal alternately for determining a control word to track the first frequency and a phase-shift controller configured to register n levels for the first control signal and the second control signal to introduce n phase delays for changing a fraction part of the control word randomly to provide a broadened boundary. The circuit also includes a digitally controlled oscillator configured to generate a synthesized periodic signal based on a base time unit, the first frequency, and the control word, with the second frequency being locked within the broadened boundary of the first frequency.