Common-mode signal absorber for GHz EMI suppression
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Solution Overview
Problem
High-speed digital circuits with non-ideal structures convert differential-mode signals into common-mode noises, causing electromagnetic interference (EMI) that existing technologies, such as common-mode chokes and defective ground structures, fail to effectively suppress, especially at high frequencies above GHz.
Innovation Solution
A common-mode signal absorber comprising an impedance-matching network and a common-mode signal reflection circuit, where the impedance-matching network absorbs common-mode signals within a specific frequency band, and the reflection circuit reflects them, with bidirectional absorption achieved by configuring impedance-matching networks at both input and output ends of the reflection circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If common-mode choke (CMC) with electromagnetic material is used to suppress EMI, then EMI suppression is improved, but effectiveness deteriorates at high frequency (GHz or above) due to quick attenuation of permeability
Solution Approach 1:
The patent changes the operating parameters by designing a resonant cavity structure that operates at specific high frequency bands (GHz range). The resonant frequency is determined by the physical dimensions and configuration of the cavity, allowing effective common-mode suppression at high frequencies where traditional CMCs fail due to permeability attenuation.
Solution Approach 2:
The patent utilizes electromagnetic resonance within the cavities to create standing waves that effectively suppress common-mode signals. The resonant oscillation at specific frequencies creates high impedance paths for common-mode currents, achieving suppression without relying on frequency-dependent material permeability.
2Object-affected harmful factors
If common-mode reflection circuit is used to reflect common-mode signal, then common-mode signal suppression is improved, but electromagnetic interference still exists as reflected signals are transmitted to other radiating elements
Solution Approach 1:
The patent converts the harmful reflected common-mode signals into beneficial absorbed energy by placing lossy materials or resistive elements within the resonant cavities. The cavities that would normally reflect signals are modified to dissipate the common-mode energy as heat, transforming the harmful re-radiation effect into a beneficial absorption mechanism.
Solution Approach 2:
The resonant cavities act as intermediary structures between the common-mode signal sources and the external environment. Instead of directly reflecting signals back to radiating elements, the cavities capture and dissipate the common-mode energy through controlled resonance and loss mechanisms, preventing re-radiation.
3Object-affected harmful factors
If defective ground structure or mushroom structure is used to construct resonant cavity, then common-mode signal suppression is improved at high frequency, but device complexity increases
Solution Approach 1:
The patent divides the ground structure into multiple segments with different configurations to form separate resonant cavities. Each segment or cavity can be independently designed and optimized for specific frequency ranges, allowing modular complexity management while achieving broad-spectrum common-mode suppression.
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 achieves an absorption rate above 50% for common-mode signals within the specific frequency band, reducing EMI and preventing interference in communication systems, while maintaining low reflection coefficients to ensure effective signal transmission.
Implementation Method 1
the first impedance-matching network is impedance matched to the common-mode signal within the specific frequency band
Implementation Method 2
the first impedance-matching network is for absorbing the common-mode signal with the specific frequency band
Implementation Method 3
The defective ground structure or the mushroom structure constructs a resonant cavity in a symmetry plane of the common-mode reflection circuit to suppress the common-mode signal by using the resonant cavity
Data Source
AI summary
The present invention provides a common-mode signal absorber, which comprises an impedance-matching network and a common-mode signal reflection circuit. A differential-mode signal is inputted into input ends of the impedance-matching network, and outputted from output ends of the common-mode signal reflection circuit. When a common-mode signal is inputted into the common-mode signal absorber, the common-mode signal reflection circuit is for reflecting the common-mode signal within a specific frequency band. Afterward, the reflection of the common-mode signal within the specific frequency band will be absorbed by an impedance element of the impedance-matching network. Thus, the common-mode signal within the specific frequency band may be absorbed by the impedance-matching network so as to avoid to interfere signals transmitted on a communication system.