Differential PCB Ground Plane Layout for Common-Mode Attenuation
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Solution Overview
Problem
Common mode signals interfere with antennas in electronic devices, causing interference with normal signal transmission, and existing solutions like common mode choke components increase power consumption, layout area, and design complexity.
Innovation Solution
A circuit board design with a ground plane featuring hollowed-out portions is used to attenuate common mode signals without affecting differential signal transmission, reducing parasitic capacitance and increasing parasitic inductance to reflect common mode signals back along the differential wires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If common mode choke components are added to attenuate common mode signals, then common mode signal interference is reduced, but power consumption, layout area, and design complexity increase
Solution Approach 1:
The patent extracts the harmful common mode signals from the differential signal transmission path by creating a separate ground reference path through hollowed-out portions in the ground plane. This allows common mode signals to be isolated and attenuated without requiring additional choke components, thereby reducing design complexity while maintaining interference reduction effectiveness
Solution Approach 2:
The hollowed-out portions in the ground plane act as an intermediary structure that provides a controlled impedance discontinuity. This intermediary feature creates parasitic capacitance and inductance that selectively attenuate common mode signals while allowing differential signals to pass through unaffected, eliminating the need for external choke components
2Object-affected harmful factors
If common mode choke components are added to attenuate common mode signals, then common mode signal interference is reduced, but power consumption increases
Solution Approach 1:
The ground plane structure with hollowed-out portions provides self-service attenuation of common mode signals through its inherent parasitic capacitance and inductance. The structure automatically reflects and attenuates common mode signals without requiring active components that consume power, achieving interference reduction with zero additional power consumption
3Object-affected harmful factors
If common mode choke components are added to attenuate common mode signals, then common mode signal interference is reduced, but layout area increases
Solution Approach 1:
The patent merges the common mode attenuation function with the existing ground plane structure by creating hollowed-out portions within it. This integration eliminates the need for separate choke components and their associated layout space, achieving common mode signal attenuation without increasing the overall layout area of the circuit board
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 attenuates common mode signals, reducing interference with antennas while maintaining normal differential signal transmission without increasing power consumption, layout area, or design complexity.
Implementation Method 1
the ground plane forms capacitance with all first differential wires and all second differential wires, respectively. Alternating current common mode signals may be coupled based on the capacitance
Implementation Method 2
parasitic inductance of the parts that are of the second part and the fifth part and that are corresponding to the first hollowed-out portion is increased. Because the parasitic capacitance is reduced and the parasitic inductance is increased, characteristic impedance R of the second part and the fifth part with respect to the ground plane is increased
Data Source
AI summary
A circuit board and an electronic device is provided. The circuit board includes: a signal layer, where the signal layer includes at least one set of differential wires, and the at least one set of differential wires includes a first differential wire and a second differential wire that are insulated from each other; the first differential wire includes a first part, a second part, and a third part that are arranged successively in an extension direction of the first differential wire; and the second differential wire includes a fourth part, a fifth part, and a sixth part that are arranged successively in an extension direction of the second differential wire; and a ground plane, where the ground plane is disposed on at least one side of the signal layer, and is insulated from the signal layer; and the ground plane is provided with a first hollowed-out portion.