Triangular Routing for Differential Pair Length Matching

Solution Overview

Problem

In high-speed differential signaling, ensuring equal lengths of conductive paths is challenging due to design constraints, leading to phase shifts and increased bit error rates caused by length mismatches in routing paths.

Innovation Solution

The triangular routing technique modifies one signal trace by replacing sections with two line segments of equivalent length, forming a vertex, to match the length of the other trace, while maintaining impedance and phase matching, thereby minimizing insertion loss and transmission delays.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If straight line routing is used from source to destination, then the routing path is simple and direct, but design constraints make it impossible to achieve equal lengths for differential pair traces

Engineering Contradiction:

Improverouting simplicityVSAvoidtrace length matching

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The routing path is divided into multiple straight line segments connected by vertices. Instead of using complex curved paths, the trace is segmented into linear sections that are easier to manufacture and align with PCB trace routing capabilities, while still achieving the required length through multiple segments rather than a single straight line.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The routing problem is solved by transitioning from one-dimensional straight line routing to two-dimensional angular routing with vertices. By introducing angular deviations and multiple segments in the spatial domain, the patent achieves precise length control while maintaining manufacturing simplicity through straight line segments connected at defined angles.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Manufacturing precision

If the conductive path length is extended to match the other trace, then length matching is achieved, but phase shifts and insertion loss increase

Engineering Contradiction:

Improvetrace length matchingVSAvoidsignal integrity

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent systematically varies routing parameters including the number of vertices, angular deviations, lateral offsets, and segment lengths to optimize the balance between achieving length matching and minimizing signal degradation. By changing these geometric parameters, the routing path achieves equal trace lengths while controlling phase shifts and insertion loss within acceptable limits.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If multiple routing segments with vertices are introduced to match lengths, then trace length equality is achieved, but routing complexity increases

Engineering Contradiction:

Improvetrace length matchingVSAvoidrouting path complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The routing path is divided into multiple straight line segments connected by vertices. Instead of using complex curved paths, the trace is segmented into linear sections that are easier to manufacture and align with PCB trace routing capabilities, while still achieving the required length through multiple segments rather than a single straight line.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The routing problem is solved by transitioning from one-dimensional straight line routing to two-dimensional angular routing with vertices. By introducing angular deviations and multiple segments in the spatial domain, the patent achieves precise length control while maintaining manufacturing simplicity through straight line segments connected at defined angles.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS10325053B2Triangular routing for high speed differential pair length matching

Publication Date: 2019.06.18 CISCO TECHNOLOGY INC

AI summary

A method and apparatus for matching the lengths of traces of differential signal pairs. The method includes determining that a first trace is longer than a second trace and modifying the second trace so that the length is substantially equal to the length of the first trace. In some implementations, the second trace can be modified by replacing one or more sections of the trace with two line segments that are substantially equal in length and meet at a vertex that is less than 180 degrees.