Common-Mode Filter Delay Tuning for Differential Signal Line Matching
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Solution Overview
Problem
In mobile phone camera modules, unequal lengths of differential signal lines cause delays, leading to abnormal display issues during photo preview, with existing solutions requiring significant PCB space, material changes, or high-cost delay circuits.
Innovation Solution
Implementing common-mode filters with varying group delays to equalize signal transmission delays across differential signal lines, where shorter lines are connected to filters with longer group delays and longer lines to those with shorter group delays, without adding new components or increasing PCB space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If lengthening the lines and arranging them in a snaky shape to achieve equal lengths, then the equal-length matching is achieved, but the PCB space requirement increases significantly
Solution Approach 1:
The patent changes the parameter of delay time by selecting common-mode filters with different group delays to match different line lengths, rather than changing the physical length of the lines themselves. This allows equal-length matching without modifying the physical layout.
Solution Approach 2:
The patent introduces common-mode filters as intermediary components between the differential signal lines and the receiver. These filters serve as delay compensation elements that equalize the signal arrival times without requiring physical line length adjustment.
2Manufacturing precision
If adjusting the relative dielectric constant to achieve delay adjustment, then the equal-length matching purpose is achieved indirectly, but different media need to be adopted in different areas of the same PCB board which is very difficult for manufacturing
Solution Approach 1:
Instead of changing the dielectric constant parameter of the PCB material, the patent changes the electrical parameter (group delay) of the common-mode filters. This approach maintains uniform PCB material while achieving delay equalization through component selection.
3Manufacturing precision
If adding a phase delay circuit in the form of an amplifier to a short line, then the requirement of equal-length within the same set of differential lines is met, but the cost is high and a considerable layout area is occupied
Solution Approach 1:
The patent uses common-mode filters which are relatively simple and inexpensive components compared to operational amplifier-based delay circuits. These filters occupy minimal layout area while providing the necessary delay equalization function.
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
This approach effectively equalizes signal delays across differential signal lines, preventing abnormal displays during photo preview, while being cost-effective and easy to implement, without occupying extra PCB space or requiring material changes.
Implementation Method 1
a group delay of the each common-mode filter is adopted for adjusting a delay of signal transmission on the one set of differential signal lines connected to the common-mode filter
Data Source
AI summary
Provided are a device, a differential signal line processing method and a differential signal line processing apparatus. The device includes a first component and a second component; the first component and the second component perform signal transmission via multiple sets of differential signal lines; the device further includes at least one common-mode filter, each common-mode filter of the at least one common-mode filter being serially connected between the first component and the second component via one set of differential signal lines, and a group delay of the each common-mode filter being adopted for adjusting a delay of signal transmission on the one set of differential signal lines connected to the common-mode filter.