High Speed Bypass Cable for Backplane Signal Integrity
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Solution Overview
Problem
Conventional cable interconnection systems using FR-4 material for circuit boards suffer from significant signal losses at high speeds (above 10 Gbps), leading to increased costs and design complexities due to the need for expensive custom materials and amplifiers to maintain signal integrity.
Innovation Solution
A high-speed bypass cable assembly utilizing twin-ax wires with a consistent geometry and structure, terminated to maintain impedance and minimize crosstalk, which bypasses the circuit board to provide a separate signal path between chips and connectors, eliminating the need for complex routing and expensive materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If FR-4 material is used for circuit boards, then cost is reduced, but signal loss increases at high speeds
Solution Approach 1:
The patent extracts the high-speed signal transmission function from the FR-4 circuit board by introducing a separate bypass cable assembly. The cable assembly with controlled impedance traces carries the high-speed signals away from the lossy FR-4 board, while the board retains its low-cost FR-4 material for power and control signals.
Solution Approach 2:
The patent segments the signal transmission paths into two distinct systems: (1) high-speed data signals transmitted through the bypass cable assembly with low-loss characteristics, and (2) power and control signals transmitted through the FR-4 circuit board. This segmentation allows each system to be optimized for its specific function.
2Reliability
If custom materials are used to reduce signal losses, then signal integrity is improved, but cost increases significantly
Solution Approach 1:
The patent extracts the high-speed signal transmission function from the expensive custom material board and places it in a separate bypass cable assembly. This allows the main board to remain inexpensive FR-4 while the cable assembly handles the high-speed signals that require careful impedance control.
Solution Approach 2:
The patent applies local quality by providing high-performance low-loss transmission characteristics only where needed (in the bypass cable assembly for high-speed signals), while the rest of the system can use standard FR-4 material. The cable assembly includes controlled impedance traces and proper grounding to ensure signal integrity locally at the high-speed interface.
3Adaptability or versatility
If long transmission lines are used, then connection flexibility is improved, but signal loss and complexity increase
Solution Approach 1:
The patent introduces a bypass cable assembly as an intermediary component between the circuit board and external connectors. This cable assembly acts as a dedicated transmission line that simplifies the overall system by providing a direct, controlled-path connection without requiring complex trace routing through the board layers.
4Reliability
If complex trace routing is used to achieve consistent impedance, then signal integrity is improved, but manufacturing complexity increases
Solution Approach 1:
The patent extracts the impedance control and signal integrity functions from the complex FR-4 trace routing and consolidates them into a dedicated bypass cable assembly. The cable assembly provides controlled impedance traces with consistent geometry, eliminating the need for complex multi-layer board routing and impedance matching networks.
Solution Approach 2:
The patent changes the physical form factor of the transmission line from planar PCB traces to a three-dimensional cable assembly structure. This allows for consistent trace geometry and impedance control that is difficult to achieve on flat circuit boards, particularly for long connections requiring multiple layers and complex routing.
Data Source
AI summary
A cable bypass assembly is disclosed for use in providing a high frequency transmission line that connect a chip package on a circuit board to connector spaced apart from the chip package. The bypass cable assembly has a structure that allows for low loss between the chip package and the connector. Multiple cables can be used to provide a number of differentially coupled channels.