PCB Differential Via Orientation for Crosstalk and Area Reduction
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Solution Overview
Problem
Existing printed circuit boards for optical transceivers face challenges in achieving high-density component arrangement and minimizing crosstalk, leading to increased area occupation and asymmetry in differential transmission lines, which hinders miniaturization and transmission integrity.
Innovation Solution
A printed circuit board design featuring differential signal vias arranged along a single direction through openings in ground conductor layers, with strategically placed ground conductor vias to reduce crosstalk and maintain equal transmission line lengths, thereby minimizing area occupation and ensuring transmission integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If differential signal vias are arranged in pairs with 90 degree orientation to suppress crosstalk, then crosstalk between neighboring pairs is reduced, but the differential transmission lines must detour around the via connection points, occupying significant area and increasing asymmetry
Solution Approach 1:
The patent applies asymmetry by arranging differential signal vias in pairs along the same direction (both vertical or both horizontal) rather than alternating 90-degree orientations. This asymmetric arrangement eliminates the need for detouring transmission lines, allowing straight-line connections that reduce area occupation while maintaining crosstalk suppression through proper via pairing and spacing.
Solution Approach 2:
The patent addresses the crosstalk issue by controlling the spatial arrangement and spacing of via pairs in the planar dimension, rather than relying on orthogonal orientation. The via pairs are positioned with controlled distances and alignments that suppress crosstalk through electromagnetic field management in the horizontal plane, eliminating the need for vertical orientation changes.
2Area of stationary object
If differential signal vias are arranged to reduce area occupation, then miniaturization is achieved, but asymmetry of differential transmission lines increases, converting differential mode to common mode
Solution Approach 1:
The patent uses asymmetric via pair arrangements where pairs are oriented along the same direction (all vertical or all horizontal) rather than alternating orientations. This allows compact, straight-line transmission line routing that minimizes area while maintaining symmetry within each differential pair, preventing differential-to-common mode conversion and ensuring reliable high-speed signal transmission.
Solution Approach 2:
The patent applies local quality by ensuring that each differential via pair maintains proper spacing and alignment characteristics specific to its location on the board. The via pairs are positioned with controlled distances from transmission lines and from each other, optimizing local electromagnetic field distribution to suppress crosstalk while maintaining transmission line symmetry and minimizing area occupation.
3Ease of manufacture
If four-channel differential transmission lines are drawn linearly on the first surface, then routing is simplified, but significant area is occupied by the transmission lines
Solution Approach 1:
The patent utilizes the vertical dimension by arranging differential signal vias in pairs with consistent orientation (all vertical or all horizontal). This allows transmission lines to connect directly to via pairs in a straight line without detours, achieving compact routing that minimizes area occupation while maintaining manufacturing simplicity through straightforward layer-to-layer alignment.
Data Source
AI summary
The present invention provides a printed circuit board comprising: a dielectric layer (130); N pairs of differential signal vias (2) which penetrate through the dielectric layer wherein N is an integer more than one; N pairs of first strip conductors (101,102) disposed on a first surface of the dielectric layer; a first ground conductor layer (103) disposed in the dielectric layer forming N first differential transmission lines (100) with the N pairs of first strip conductors and the dielectric layer; N pairs of second strip conductors (111,112) disposed on a second surface of the dielectric layer; a second ground conductor layer (113) disposed in the dielectric layer forming N of second differential transmission lines (110) with the N pairs of second strip conductors and the dielectric layer.