PCB Electromagnetic Band-Gap Layout for SSN and Signal Integrity
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Solution Overview
Problem
Conventional methods for suppressing simultaneous switching noise (SSN) in high-speed digital systems, such as decoupling capacitors and embedded thin film capacitors, are ineffective in GHz bands and increase production costs, while existing electromagnetic band-gap (EBG) structures complicate the manufacturing process and affect high-speed signal lines.
Innovation Solution
An electromagnetic band-gap structure is arranged on portions of the power and ground planes in a multilayer PCB or package structure to suppress SSN, with the regions without the EBG used as return current paths for high-speed signals, allowing for improved signal integrity and electromagnetic interference characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If electromagnetic band-gap structure is applied to suppress SSN, then noise suppression is improved, but manufacturing complexity increases
Solution Approach 1:
The electromagnetic band-gap structure is divided into multiple unit cells that are periodically arranged on the power and ground planes. Each unit cell consists of simple conductive patterns that can be easily manufactured, while the collective periodic arrangement provides the noise suppression function. This segmentation allows complex electromagnetic functionality to be achieved through simple, repeatable manufacturing units.
Solution Approach 2:
The electromagnetic band-gap structure is selectively applied only in regions where noise suppression is needed, such as near high-speed digital circuits and interfaces, while leaving other regions as simple power and ground planes. This localized application maintains manufacturing simplicity in non-critical areas while providing noise suppression where required.
2Object-affected harmful factors
If electromagnetic band-gap structure is applied to suppress SSN, then noise suppression is improved, but signal integrity is degraded
Solution Approach 1:
The electromagnetic band-gap structure is segmented into periodic unit cells with specific geometric parameters that create frequency-selective noise suppression. The periodic structure provides stopband frequencies for noise while maintaining passband frequencies for signal transmission, thus suppressing SSN while preserving signal integrity through careful design of the unit cell dimensions and spacing.
Solution Approach 2:
The electromagnetic band-gap structure parameters (unit cell size, spacing, conductor width) are optimized to create frequency-selective suppression characteristics. By adjusting these parameters, the structure suppresses noise frequencies while allowing signal frequencies to pass through, thus resolving the contradiction between noise suppression and signal integrity.
3Ease of manufacture
If conventional noise suppression methods are used, then manufacturing is simpler, but noise suppression effectiveness is reduced
Solution Approach 1:
The electromagnetic band-gap structure uses segmented periodic unit cells that can be manufactured using standard PCB fabrication processes. Each unit cell is a simple conductive pattern that can be easily produced, yet the periodic arrangement of these simple segments creates complex electromagnetic noise suppression functionality that conventional methods cannot achieve.
Solution Approach 2:
The electromagnetic band-gap structure creates a composite electromagnetic environment by periodically arranging conductive patterns on the power and ground planes. This composite structure combines the simplicity of standard PCB materials with sophisticated electromagnetic noise suppression properties, achieving both ease of manufacture and noise suppression effectiveness.
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 solution effectively reduces SSN and enhances signal integrity and electromagnetic interference characteristics by using the EBG structure near noise sources and allowing high-speed signals to use regions without the EBG as return paths, thereby improving overall system performance.
Implementation Method 1
an electromagnetic band-gap is arranged in a portion of the power plane and/or ground plane to suppress noises generating in a power distribution network
Data Source
AI summary
An electromagnetic-wave suppression structure in a multilayer PCB or package structure is supplied with a power to be used therein by a power distribution network including a power plane and a ground plane. The multilayer PCB and package includes: an electromagnetic-wave suppression structure including an electromagnetic band-gap; and the electromagnetic-wave suppression structure is formed at a specific portion(s) of the power plane and/or the ground plane to suppress noises.