Line-Rate Spread Spectrum Clocking for EMI-Safe Line Imaging
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Solution Overview
Problem
Spread spectrum clocking in imaging systems reduces electromagnetic interference (EMI) but often degrades image quality due to variations in exposure and sampling times, causing line-to-line intensity variations and image artifacts.
Innovation Solution
A line rate spread spectrum clock generator synchronizes the spread spectrum clock signal with the line rate of the imaging device, ensuring consistent exposure and sampling times across lines, and a mixed domain spread spectrum clocking scheme applies spread spectrum clocking only to data output to reduce EMI while maintaining image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If spread spectrum clocking is applied to reduce EMI, then electromagnetic interference is reduced, but image quality degrades due to exposure time and sampling time variations
Solution Approach 1:
The patent segments the clock signal application by implementing spread spectrum clocking only for the data output clock domain while maintaining a stable clock for the imaging/sampling clock domain. This segmentation allows EMI reduction in data transmission without affecting image quality in the imaging process.
Solution Approach 2:
The patent applies different clocking strategies to different functional domains: spread spectrum clocking is applied locally to the data output domain where EMI is problematic, while a stable unmodulated clock is maintained locally in the imaging/sampling domain where precision is critical. This local differentiation resolves the contradiction between EMI reduction and image quality.
2Object-generated harmful factors
If spread spectrum clocking is applied to the imaging clock, then EMI is reduced, but exposure time varies causing line-to-line intensity variations
Solution Approach 1:
The patent segments the clocking architecture into separate domains: the imaging clock domain uses a stable unmodulated clock to ensure consistent exposure time, while the data output clock domain uses spread spectrum clocking for EMI reduction. This segmentation prevents exposure time variation while still achieving EMI reduction.
Solution Approach 2:
The patent applies spread spectrum modulation only to the data output clock domain where it provides EMI reduction without affecting imaging stability. The imaging clock domain maintains local quality with a stable frequency to ensure consistent exposure time across all lines.
3Object-generated harmful factors
If spread spectrum clocking is applied to the sampling clock, then EMI is reduced, but sampling time varies causing image artifacts
Solution Approach 1:
The patent segments the clocking system into distinct functional domains: sampling clock domain uses a stable frequency for consistent sampling timing, while data output clock domain uses spread spectrum for EMI reduction. This segmentation eliminates sampling time variation artifacts while maintaining EMI reduction benefits.
Solution Approach 2:
The patent applies spread spectrum clocking locally only to the data output domain where EMI is generated, while maintaining a stable clock frequency locally in the sampling domain to ensure consistent sampling timing and prevent image artifacts.
Data Source
AI summary
A method of generating a spread spectrum clock signal for a line imaging device including receiving a line length value of the line imaging device, receiving a first clock signal indicative of a system timing signal in the line imaging device, generating a spreading waveform having a frequency as a function of the line length value and having a total number of clock cycles matching the line length value, and modulating the first clock signal using said spreading waveform to generate the spread spectrum clock signal where the spread spectrum clock signal is used for driving the imaging, data sampling and digitizing, and data transfer operation of the line imaging device. The spread spectrum clock has the same clock frequency variation for each scan line of the line imaging device.