Reference Plane Control for Transmission Line Impedance
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Solution Overview
Problem
Existing methods for controlling the characteristic impedance of transmission lines in ASICs often result in higher insertion loss and increased signal crosstalk, failing to achieve the desired impedance efficiently.
Innovation Solution
The use of a constant thickness reference plane proximate to the signal trace allows for precise control of transmission line characteristic impedance, enabling a wider trace width with lower insertion loss and reduced crosstalk by adjusting the dimensions and structure of the reference plane, such as using non-continuous or non-solid reference planes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If line width is reduced to achieve high characteristic impedance, then characteristic impedance is improved, but insertion loss increases and signal crosstalk likelihood increases
Solution Approach 1:
The patent changes the geometric parameters of the reference plane (thickness, width, position) rather than the signal trace parameters to achieve impedance control. By adjusting the reference plane thickness and width, the characteristic impedance can be optimized without compromising signal trace width, thereby reducing insertion loss while maintaining desired impedance values.
Solution Approach 2:
The patent moves the control mechanism from the horizontal plane (trace width) to the vertical dimension (reference plane thickness and positioning). By controlling the distance between the signal trace and reference plane,以及the reference plane thickness, the characteristic impedance is adjusted without affecting the signal trace width, thus avoiding increased insertion loss and crosstalk.
2Manufacturing precision
If line width is reduced to achieve high characteristic impedance, then characteristic impedance is improved, but signal crosstalk likelihood increases
Solution Approach 1:
The patent changes the reference plane parameters (thickness, width, position) to control characteristic impedance. By optimizing these parameters, the desired impedance is achieved while maintaining adequate spacing between signal traces, thereby reducing signal crosstalk without compromising impedance precision.
Solution Approach 2:
The reference plane serves as an intermediary element between signal traces. By properly designing the reference plane's thickness, width, and position, it provides electromagnetic shielding and establishes controlled impedance pathways, reducing crosstalk between adjacent signal traces while maintaining the required characteristic impedance.
3Manufacturing precision
If dielectric thickness is increased to achieve high characteristic impedance, then characteristic impedance is improved, but insertion loss increases
Solution Approach 1:
The patent provides comprehensive parameter optimization including dielectric thickness, reference plane thickness, reference plane width, and reference plane position. By jointly optimizing these parameters rather than solely increasing dielectric thickness, the characteristic impedance is achieved with minimal impact on insertion loss, as the reference plane geometry can be tuned to compensate for dielectric changes.
Data Source
AI summary
A system for using a reference plane to control transmission line characteristic impedance includes a signal trace located in a multi-layer structure and at least one constant thickness reference plane proximate to the signal trace, the constant thickness reference plane located with respect to the signal trace so as to provide a desired characteristic impedance between the signal trace and the constant thickness reference plane.