Multilayer Common Mode Filter Tuning for Flexible Optical Transceivers
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Solution Overview
Problem
Existing common mode filters in high-speed data communication systems have a wide bandwidth for common mode suppression, which can lead to reduced design flexibility and increased size of the optical transceivers.
Innovation Solution
A common mode filter integrated into a multilayer substrate, featuring a pair of differential signal lines, a ground conductor, a resonant conductor pattern, and a cover conductor pattern, with specific geometric and connection configurations to reduce the suppression bandwidth and ratio, enhancing design flexibility and downsizing the optical transceiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a common mode filter with wide bandwidth suppression is used, then common mode noise suppression is improved, but design flexibility is reduced and device size increases
Solution Approach 1:
The common mode filter is divided into multiple resonant conductor patterns (first, second, third patterns) with different resonant frequencies. Each pattern targets a specific frequency band, allowing the filter to suppress common mode noise across a wide bandwidth without requiring a single wide-bandwidth filter structure that would constrain design flexibility and increase size.
Solution Approach 2:
Different resonant conductor patterns are positioned at specific locations relative to the differential signal lines to optimize suppression at different frequency bands. The first resonant conductor pattern is positioned to suppress lower frequencies, while the second and third patterns target higher frequencies, creating localized suppression zones that maintain design flexibility.
2Reliability
If a common mode filter with wide bandwidth suppression is used, then common mode noise suppression is improved, but device size increases
Solution Approach 1:
The filter uses multiple compact resonant conductor patterns instead of a single large wide-bandwidth filter structure. This segmentation allows the filter to achieve wide bandwidth suppression through multiple narrow-band patterns that can be densely packed, reducing the overall volume required in the optical transceiver.
Solution Approach 2:
The resonant conductor patterns are arranged in a nested or overlapping configuration where the second and third resonant conductor patterns are positioned to utilize the same spatial region as the first pattern but at different vertical or horizontal levels. This nesting allows multiple filter functions to coexist in a compact volume.
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 proposed common mode filter achieves a reduced suppression bandwidth and ratio, thereby enhancing the design flexibility of differential transmission lines and downsizing optical transceivers while maintaining effective common mode noise suppression.
Implementation Method 1
a resonant conductor pattern formed in one of the same layer as the ground conductor or a layer above the ground conductor, the resonant conductor pattern covering partial regions of the pair of differential signal lines in plan view and being connected to the ground conductor; and a cover conductor pattern formed in a layer above the pair of differential signal lines, the cover conductor pattern covering the resonant conductor pattern in plan view and being connected to the ground conductor
Implementation Method 2
a resonant conductor pattern formed in one of the same layer as the ground conductor or a layer above the ground conductor, the resonant conductor pattern covering partial regions of the pair of differential signal lines in plan view and being connected to the ground conductor
Data Source
AI summary
Provided are a common mode filter in which a suppression bandwidth and a suppression ratio of a common mode are reduced, thereby enhancing a design flexibility of a differential transmission line and downsizing the common mode filter, and an optical transceiver which uses the common mode filter. The common mode filter includes: a pair of differential signal lines formed in a multilayer substrate including a dielectric layer; a ground conductor formed in a layer below the pair of differential signal lines; a resonant conductor pattern formed in one of the same layer as the ground conductor or a layer above the ground conductor, the resonant conductor pattern covering partial regions of the pair of differential signal lines in plan view; and a cover conductor pattern formed in a layer above the pair of differential signal lines, the cover conductor pattern covering the resonant conductor pattern in plan view.