Differential PCB Traces With Tuned Rejection Paths for CM Noise
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Solution Overview
Problem
Existing information handling systems face challenges in accurately measuring and reducing wide-band common mode noise in high-speed differential traces due to imperfections in implementation, which can cause electromagnetic interference and disturb receiver timings.
Innovation Solution
Incorporating CM detection and rejection blocks on the PCB that include positive and negative signal directional couplers and feedback traces to measure and reduce CM noise, with tunable frequency settings to improve coupling performance and impedance matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional single-frequency CM noise reduction methods are used, then narrow-band CM noise can be reduced, but wide-band CM noise cannot be effectively reduced
Solution Approach 1:
The patent divides the wide-band CM noise reduction into multiple narrow-band rejection traces, each tuned to a specific frequency. This segmentation allows each trace to effectively reduce CM noise at its designated frequency while collectively covering a wide frequency range, resolving the contradiction between narrow-band effectiveness and wide-band coverage.
2Reliability
If multiple rejection traces for different frequencies are added, then wide-band CM noise reduction is achieved, but device complexity increases
Solution Approach 1:
The rejection traces are designed to serve multiple purposes: they detect CM noise, provide frequency-selective filtering, and reduce EM interference across wide frequency bands. By making each trace multi-functional, the patent achieves wide-band noise reduction without proportionally increasing overall system complexity.
3Object-affected harmful factors
If rejection traces are added to reduce CM noise, then EM interference is reduced, but PCB area increases
Solution Approach 1:
The rejection traces are strategically positioned between the differential signal traces, utilizing the existing spatial arrangement. Each rejection trace is localized to specific frequency ranges and placed where it can most effectively intercept CM noise without requiring extensive PCB real estate, thus reducing EM interference while minimizing area increase.
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
Enables real-time measurement and effective reduction of CM noise across various frequencies, enhancing signal integrity and reducing electromagnetic interference in high-speed data communication.
Implementation Method 1
The first rejection trace may detect a first common mode (CM) signal present on the differential signal traces
Implementation Method 2
reduce the first CM signal on the differential signal traces
Data Source
AI summary
A printed circuit board includes a pair of differential signal traces, a first rejection trace between the positive signal trace and the negative signal trace, and a second rejection trace between the positive signal trace and the negative signal trace. The differential signal traces include a positive signal trace and a negative signal trace. The first rejection trace detects a first common mode (CM) signal present on the differential signal traces, and reduces the first CM signal on the differential signal traces. The second rejection trace detects a second CM signal present on the differential signal traces, and reduces the second CM signal on the differential signal traces. The first CM signal is centered at a first frequency, and the second CM signal is centered at a second frequency.