Spread-Spectrum Clock Generator With Controlled Phase Synchronization
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Solution Overview
Problem
Conventional spread-spectrum clock signals have uncontrollable phase relationships, leading to unreliable data transmission as they cannot ensure consistent data-establishing and data-maintaining times, making the system insecure for data transmission.
Innovation Solution
A circuit and method utilizing a frequency locked loop with a digitally controlled oscillator and phase-shift controller to generate a spread-spectrum synchronous clock signal, ensuring the phases remain within a broadened boundary, thereby maintaining synchronization and security in data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional spread-spectrum clock signals are used, then electromagnetic interference resistance is improved, but data transmission reliability deteriorates due to uncontrollable phase relationships
Solution Approach 1:
The patent changes the phase parameter of the clock signal by introducing a phase-shifting mechanism that randomly selects from multiple predefined phase states (0, Δ, 2Δ, ..., (K-1)Δ). This random phase selection spreads the spectral energy while maintaining synchronization through controlled phase relationships, resolving the contradiction between EMI resistance and data transmission reliability
Solution Approach 2:
The patent implements a feedback mechanism where the receiver detects the phase-shifted clock signal and generates synchronization information that is fed back to maintain phase alignment. This feedback loop ensures that even with random phase shifts, the transmitter and receiver remain synchronized, preserving data transmission reliability while benefiting from spread-spectrum EMI resistance
2Object-affected harmful factors
If clock signal phases are spread randomly, then electromagnetic interference is reduced, but data alignment capability deteriorates
Solution Approach 1:
The patent makes the phase parameter dynamic by introducing time-varying random phase shifts that change according to a predetermined sequence known to both transmitter and receiver. This dynamic phase modulation spreads the spectrum to reduce EMI while the predetermined sequence maintains data alignment capability through synchronized phase reconstruction at the receiver
Solution Approach 2:
The patent applies preliminary action by pre-establishing the phase-shifting sequence at both transmitter and receiver before data transmission begins. This preliminary synchronization ensures that when random phase shifts are applied, both ends can correctly interpret the phase information and maintain proper data alignment, preventing EMI-related errors
3Object-affected harmful factors
If spread-spectrum technique is applied to clock signal, then power flux density is limited, but clock signal strength deteriorates
Solution Approach 1:
The patent employs periodic action by cycling through a predetermined sequence of phase shifts rather than using continuous random phase modulation. This periodic structure maintains the spread-spectrum benefit of limiting power flux density while the regular pattern preserves clock signal strength through predictable, synchronized phase transitions that can be efficiently tracked by the receiver
Data Source
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.