PCB Capacitor Arrangement for Negative Mutual Inductance
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Solution Overview
Problem
Conventional differential signaling systems in electronic apparatuses face challenges in suppressing radiation noise due to common mode currents, which are not effectively returned to the semiconductor element, leading to increased electromagnetic interference.
Innovation Solution
A printed circuit board design featuring capacitor elements arranged such that their parasitic inductances have a negative mutual inductance, facilitating the return of common mode currents to the ground terminal, thereby reducing effective inductance and suppressing radiation noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional capacitor elements are used in the filter circuit, then the circuit can return common mode currents to the ground terminal, but the parasitic inductance of the capacitor elements increases the effective inductance, reducing filter effectiveness in high frequency bands
Solution Approach 1:
The capacitor elements are arranged asymmetrically with respect to the differential signal wirings, specifically positioning them such that the mutual inductance between the capacitor elements has a negative value. This asymmetric arrangement reduces the effective inductance for common mode currents, improving filter effectiveness at high frequencies and reducing radiation noise.
Solution Approach 2:
The invention changes the physical arrangement parameters of the capacitor elements to alter the mutual inductance value. By positioning the capacitor elements such that their parasitic inductances have a negative mutual inductance, the effective inductance is reduced, thereby improving the filter circuit's performance in suppressing radiation noise.
2Productivity
If the data transmission rate is increased to achieve higher printing speed and image quality, then the signal transmission frequency must be increased, but this increases radiation noise from common mode currents
Solution Approach 1:
The invention changes the physical parameters of the filter circuit, specifically the arrangement of capacitor elements, to reduce effective inductance. This allows the system to operate at higher frequencies required for increased printing speed while maintaining radiation noise suppression through improved filter effectiveness.
Solution Approach 2:
The filter circuit with optimized capacitor arrangement provides preliminary suppression of common mode currents before they can radiate noise. By reducing the effective inductance through strategic capacitor placement, the system preemptively counteracts the radiation noise issue that would otherwise increase with higher transmission frequencies.
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
The design effectively reduces radiation noise by minimizing effective inductance for common mode currents, improving filter characteristics in high frequency bands and maintaining signal quality.
Implementation Method 1
capacitor elements arranged such that their parasitic inductances have a negative mutual inductance, facilitating the return of common mode currents to the ground terminal
Implementation Method 2
capacitor elements arranged such that their parasitic inductances have a negative mutual inductance
Data Source
AI summary
A printed circuit board (e.g., 103) includes capacitor elements (e.g., 121 and 122). The capacitor element (e.g., 121) returns a common mode current included in a signal output from a signal output terminal (e.g., 111) of a semiconductor element (e.g., 102), to a ground terminal (e.g., 113) of the semiconductor element (e.g., 102). The capacitor element (e.g., 122) returns a common mode current included in a signal output from a signal output terminal (e.g., 112) of the semiconductor element (e.g., 102), to the ground terminal (e.g., 113) of the semiconductor element (e.g., 102). The capacitor elements (e.g., 121 and 122) are arranged such that the mutual inductance between a parasitic inductance of the capacitor element (e.g., 121) and a parasitic inductance of the capacitor element (e.g., 122) for the common mode currents is a negative value. Accordingly, the effective inductances of the first and second capacitor elements for the common mode currents are reduced, which suppresses radiation noise.