Compact Electromagnetic Bandgap Structure for PCB Noise Shielding
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Solution Overview
Problem
The existing electromagnetic bandgap structures are ineffective in preventing mixed signal interference between analog and digital circuits, particularly in mobile communication terminals, due to their large size and high bandgap frequency, which fails to adequately shield noise in the 0.8 to 2.0 GHz operation frequency band.
Innovation Solution
A compact electromagnetic bandgap structure is designed with a serial connection of an odd number of vias through a metal line between a metal plate and a metal layer, providing sufficient inductance in a small space, thereby lowering the bandgap frequency and preventing signal transmission within the desired frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional electromagnetic bandgap structures are used, then noise shielding function is provided, but the structure size is large and bandgap frequency is high
Solution Approach 1:
The electromagnetic bandgap structure is divided into multiple unit structures arranged in an array. Each unit structure contains via holes penetrating the ground layer and power layer, with metal plates formed between adjacent via holes. This segmentation allows the overall noise shielding function to be achieved through repeated small units rather than a single large structure, enabling compact integration while maintaining effective noise blocking in the 0.8 to 2.0 GHz frequency range.
2Object-affected harmful factors
If conventional electromagnetic bandgap structures are used, then noise shielding function is provided, but the bandgap frequency is too high for the desired 0.8 to 2.0 GHz range
Solution Approach 1:
The bandgap frequency is adjusted by modifying key parameters of the unit structures: the diameter and spacing of via holes, the size and position of metal plates, and the thickness of dielectric layers. By optimizing these parameters, the bandgap frequency is tuned to fall within the 0.8 to 2.0 GHz range, matching the operating frequencies of mobile communication terminals. The inductance of via holes and capacitance of metal plates are specifically controlled to achieve the desired resonant frequency.
3Area of stationary object
If the size of bandgap structure is reduced, then compact integration is achieved, but sufficient inductance cannot be obtained
Solution Approach 1:
The via holes are designed to penetrate through multiple layers (ground layer and power layer) in the vertical dimension, creating three-dimensional current paths. This vertical extension compensates for the reduced horizontal footprint, allowing sufficient inductance to be achieved within a compact planar area. The metal plates between adjacent via holes further enhance the inductive effect by extending the current path through the dielectric layer, ensuring adequate inductance values even with small unit structure dimensions.
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 the size of the bandgap structure while maintaining or improving noise shielding performance, specifically achieving a bandgap frequency below 1.7 GHz in a smaller size, effectively blocking electromagnetic waves in the 0.8 to 2.0 GHz range, thus addressing the mixed signal problem in mobile communication terminals.
Implementation Method 1
the repeated formation of the mushroom type structure 230 results in a bandgap structure preventing a signal having a certain frequency band from being penetrated
Implementation Method 2
The function of preventing a signal having a certain frequency band from being penetrated, which is based on resistance RE and RP, inductance LE and LP, capacitance CE, CP and CG and conductance GP and GE
Implementation Method 3
The function of preventing a signal having a certain frequency band from being penetrated, which is based on resistance RE and RP, inductance LE and LP, capacitance CE, CP and CG and conductance GP and GE
Data Source
AI summary
An electromagnetic bandgap structure and a printed circuit board that can solve a mixed signal problem between an analog circuit and a digital circuit are disclosed. In accordance with an embodiment, an electromagnetic bandgap structure is stacked with a first metal layer, a first dielectric layer, a metal plate, a second dielectric layer and a second metal layer, and an odd number of vias can be serially connected through a metal line between the first metal layer and the metal plate. This electromagnetic bandgap structure can have a small size and a low bandgap frequency.