Multi-Channel Transmitter EMI Reduction via Phase Rotator Clock Offsets
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Solution Overview
Problem
Multi-channel transmission devices with multiple transmitters experience high electromagnetic interference (EMI) due to synchronous operation, exceeding Federal Communications Commission (FCC) regulations, as the power radiation of EMI increases with the number of transmitters.
Innovation Solution
A multi-channel transmission device is designed with a clock generator producing multiple input clocks, which are used by transmitters to generate spread spectrum clocks with varying frequency offsets through phase rotators, ensuring that transmitters do not operate synchronously, thereby reducing EMI power radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple transmitters perform data transmission based on the same clock, then data transmission efficiency is improved, but electromagnetic interference power radiation increases
Solution Approach 1:
The patent applies parameter changes by modifying the clock frequency parameters for each transmitter. Specifically, each transmitter is assigned a different clock frequency (e.g., Tx1 uses f1, Tx2 uses f2, etc.), transforming the uniform clocking scheme into a diversified frequency scheme. This parameter differentiation ensures that transmitters operate at different rates, preventing synchronous EMI while maintaining overall system productivity through coordinated but asynchronous data transmission.
2Stability of the object's composition
If transmitters operate synchronously based on the same clock, then coordination between transmitters is improved, but electromagnetic interference exceeds FCC regulation
Solution Approach 1:
The patent implements dynamics by introducing dynamic frequency adjustment mechanisms. Each transmitter operates with its own clock frequency that can be dynamically controlled and adjusted. This dynamic approach allows the system to maintain coordination through centralized control while avoiding fixed synchronous operation, thereby reducing EMI power radiation to levels compliant with FCC regulations.
3Device complexity
If multiple transmitters use the same clock timing, then system simplicity is maintained, but EMI power radiation sums up excessively
Solution Approach 1:
The patent applies segmentation by dividing the unified clocking system into separate, independent clocking subsystems for each transmitter. Instead of one shared clock source, each transmitter has its own clock generator producing distinct frequencies. This segmentation isolates the EMI sources, preventing their summation, while the overall system complexity remains manageable through modular architecture and centralized coordination.
Data Source
AI summary
A multi-channel transmission device is provided. The multi-channel transmission device includes a clock generator and a plurality of transmitters. The clock generator generates input clocks. The transmitters operate based on spread spectrum clocks respectively. Each of the transmitters comprises a phase rotator. The phase rotator provides a selection signal and an interpolation signal of multiple bits. The phase rotator selects two of the input clocks as a first selected input clock and a second selected input clock according to the selection signal, and generate a spread spectrum clock according to the interpolation signal, the first selected input clock and the second selected input clock.