Differential Pair Stub Matching for PCB Connector Impedance
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Solution Overview
Problem
High-frequency RF signals, such as those used in 5G mmWave applications, experience insertion and reflection losses due to impedance mismatches between PCBs and connectors, which are costly to tailor for high pin-count connectors.
Innovation Solution
Incorporating impedance matching stubs on each conductor of a differential pair to match the impedance of the connector pins with the PCB conductors, reducing insertion and return losses by adjusting the length, width, thickness, and shape of these stubs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If high pin-count back plane connectors are used for cost reasons, then connector cost is reduced, but impedance mismatch losses increase
Solution Approach 1:
Impedance matching stubs are introduced as intermediary elements between the connector pins and the PCB traces. These stubs act as mediators that transform the impedance from the connector pin impedance to the PCB trace impedance, enabling cost-effective high pin-count connectors to be used without suffering from severe impedance mismatch losses.
Solution Approach 2:
The impedance matching stubs utilize parameter changes in their physical dimensions (length, width, thickness, shape) to achieve the desired impedance transformation. By carefully controlling these geometric parameters, the stubs can match the impedance of the differential pair to the connector pins, thereby reducing insertion and reflection losses while using standard, cost-effective connectors.
2Loss of energy
If custom tailoring of conductor dimensions and dielectric constant is performed to match impedance, then impedance mismatch losses are reduced, but manufacturing complexity and cost increase
Solution Approach 1:
Instead of custom-tailoring the main conductor dimensions and dielectric properties, the patent introduces impedance matching stubs as intermediary elements. These stubs handle the impedance transformation function, allowing the main conductors to use standard, off-the-shelf dimensions and materials, thereby reducing manufacturing complexity while still achieving low insertion and reflection losses.
Solution Approach 2:
The impedance matching is achieved through parameter changes in the stub dimensions rather than in the main conductor or dielectric material. This approach allows the use of standard materials and conductor geometries, simplifying manufacturing while achieving the desired impedance matching through careful design of the stub parameters.
3Speed
If higher frequencies are used for 5G mmWave applications, then data transmission capability is improved, but impedance sensitivity and signal losses increase
Solution Approach 1:
The impedance matching stubs are designed with specific dimensional parameters (length, width, thickness, shape) that are optimized for high-frequency operation. These parameter changes enable the stubs to effectively match impedances at mmWave frequencies, reducing signal losses and enabling high-speed data transmission capabilities.
Solution Approach 2:
The stubs serve as intermediary impedance transformation elements that are particularly important at high frequencies where impedance mismatches cause severe signal degradation. By introducing these matching stubs, the system can effectively transmit high-frequency mmWave signals with minimal loss, enabling advanced 5G data transmission capabilities.
Data Source
AI summary
A printed circuit board (PCB), such as an antenna backplane, including a first conductor and a second conductor forming a differential pair, a first junction and a second junction connected to the first conductor and the second conductor, respectively, and a first impedance matching stub and a second impedance matching stub connected to the first conductor and the second conductor, respectively. The differential pair has a first impedance, the first junction and the second junction have a second impedance, and the first impedance matching stub and the second impedance matching stub match the second impedance to the first impedance. The PCB may have a connector that has differential pins joined to the first and second junctions, and the first impedance matching stub and the second impedance matching stub match an impedance of the junctions, pins, and a connector to the first impedance.