Differential PCB Ground-Plane Cutout for Common-Mode Attenuation
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Solution Overview
Problem
Existing technologies face challenges in attenuating common mode signals on differential wires without affecting normal differential signal transmission, which can interfere with nearby antennas.
Innovation Solution
A circuit board design that includes a signal layer with differential wires and a ground plane with strategically formed hollowed-out portions, allowing for the attenuation of common mode signals by altering the characteristic impedance and reducing parasitic capacitance and inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a common mode filter is added to attenuate common mode signals, then the interference with antenna is reduced, but the device complexity and layout area increase
Solution Approach 1:
The patent combines the common mode filtering function with the existing ground plane structure by creating hollowed-out portions directly in the ground plane. This integration eliminates the need for separate common mode filter components, thereby reducing device complexity and layout area while still achieving effective common mode signal attenuation and interference reduction with the antenna.
2Object-affected harmful factors
If hollowed-out portions are formed in the ground plane, then parasitic capacitance is reduced and common mode signals are attenuated, but the manufacturing process becomes more complex
Solution Approach 1:
The patent modifies the ground plane structure by creating hollowed-out portions with specific geometric parameters (size, shape, position) to control parasitic capacitance values. By adjusting these parameters, the design achieves optimal common mode signal attenuation while maintaining compatibility with standard PCB manufacturing processes, thus balancing performance improvement with ease of manufacture.
3Object-affected harmful factors
If the hollowed-out portion overlaps with the differential wire projection, then common mode signal attenuation is enhanced, but the differential signal transmission may be affected
Solution Approach 1:
The patent strategically positions hollowed-out portions in the ground plane to create localized zones with modified electromagnetic characteristics. By carefully controlling the location, size, and shape of these hollowed-out portions, the design enhances common mode signal attenuation in specific areas while maintaining proper differential signal transmission pathways, thus achieving selective filtering without compromising signal integrity.
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
Effectively reduces the impact of common mode signals on antennas by attenuating them along the transmission path, while ensuring normal transmission of differential signals, thus improving the operational quality of electronic devices.
Implementation Method 1
an orthographic projection of the first hollowed-out portion on the signal layer overlaps with the second part and the fifth part
Implementation Method 2
a process of attenuating the common mode signal is implemented by forming a first hollowed-out portion on an existing ground plane
Data Source
Figure 1~2a
Figure 2b~4
Figure 5~7
AI summary
This application provides a circuit board and an electronic device, and relates to the field of signal transmission technologies, to attenuate a common mode signal on a differential wire without affecting normal transmission of a differential signal, so as to reduce impact on an antenna close to the differential wire. 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, and an orthographic projection of the first hollowed-out portion on the signal layer overlaps with the second part and the fifth part.