Spread Spectrum Modulator for Imaging Reader EMI Suppression
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Solution Overview
Problem
Existing imaging readers face challenges with electromagnetic interference (EMI) during high-speed data transfer between the imager and controller due to the flexible cable, which radiates undesirable radiation, and existing solutions like spread spectrum clocking introduce noise or generate redundant data, degrading performance.
Innovation Solution
A suppression circuit is implemented, comprising a spread spectrum modulator and a FIFO buffer, which modulates the pixel clock signal to generate a variable spread spectrum frequency that varies above and below the pixel clock frequency, allowing the buffer to adjust storage of image data accordingly, thereby suppressing EMI without introducing noise or oversampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a flexible cable is used to transfer image data between the imager and controller, then the device structure becomes simple and easy to assemble, but electromagnetic radiation interference increases and degrades performance
Solution Approach 1:
The patent converts the harmful electromagnetic radiation from the flexible cable into a beneficial effect by using spread spectrum modulation. The high-frequency clock signal that causes EMI is transformed into a frequency-spread signal that reduces peak radiation levels while maintaining data transfer functionality, effectively turning the cable's antenna effect from a problem into a managed characteristic.
Solution Approach 2:
The patent changes the temporal and frequency parameters of the clock signal used for data transfer. By implementing spread spectrum modulation, the clock frequency is varied over time according to a pseudorandom sequence, which spreads the energy spectrum and reduces electromagnetic radiation intensity at any single frequency, thereby mitigating EMI while preserving data integrity.
2Object-affected harmful factors
If spread spectrum clocking is applied at the imager input, then electromagnetic radiation is suppressed, but noise is introduced into the image data
Solution Approach 1:
The patent applies spread spectrum modulation to the pixel clock signal before it is used to transfer image data from the imager. By pre-modulating the clock signal with a pseudorandom sequence, the EMI is suppressed at the source while the image data itself remains unaffected, as the modulation is applied to the timing signal rather than the data signal path.
3Object-affected harmful factors
If spread spectrum clocking is applied at the imager output, then electromagnetic radiation is suppressed, but redundant image data is generated and performance decreases
Solution Approach 1:
The patent implements spread spectrum modulation on the pixel clock signal at its source, before the image data transfer process begins. This preliminary modulation of the timing signal suppresses EMI without affecting the data stream, avoiding the need for oversampling and subsequent redundant data processing that would degrade performance.
Solution Approach 2:
The patent separates the clock signal path from the data signal path, applying spread spectrum modulation only to the clock signal. This segmentation allows independent optimization of EMI suppression for the timing signal while preserving the integrity and efficiency of the data transfer path, preventing redundant data generation.
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 suppresses electromagnetic radiation interference without degrading image data quality, preventing redundant data generation and maintaining performance by ensuring efficient data transfer.
Implementation Method 1
a spread spectrum modulator operatively connected to the imager for modulating the pixel clock signal to generate a variable spread spectrum frequency
Data Source
AI summary
An imager in an imaging reader captures light from a target, generates image data from the captured light, and generates a pixel clock signal having a pixel clock frequency in synchronism with the image data. A controller is connected via an electrical conductor to the imager, and controls the imager to transfer the image data, receives the image data, and processes the image data. A circuit suppresses electromagnetic radiation generated by the conductor during the image data transfer, and includes a spread spectrum modulator for modulating the pixel clock signal to generate a variable spread spectrum signal having a spread spectrum frequency that periodically varies above and below the pixel clock frequency, and a buffer having a plurality of registers for receiving and temporarily storing the image data, and for varying as a function of the spread spectrum frequency how much of the image data is being temporarily stored.