Circuit Board Ground Plane Segmentation for Digital Noise Isolation
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Solution Overview
Problem
In high-density circuit board structures, particularly in SPECT scanners, the close proximity of high-speed digital signals to sensitive analog signals leads to digital noise interference, which can damage electronics and degrade signal quality.
Innovation Solution
A circuit board design with a grounded, conductive band interposed between high-speed digital and analog circuits, and a ground plane with separate analog and digital areas, where the digital area underlies only digital structures and the analog area underlies only analog structures, effectively shielding analog circuits from digital noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If high-speed digital circuits are placed in close proximity to sensitive analog circuits on a single board, then space utilization is improved, but digital noise interference increases
Solution Approach 1:
The circuit board is divided into separate analog and digital regions with distinct ground planes. The ground plane is segmented into analog ground and digital ground portions, each serving their respective circuit types. This segmentation prevents digital noise from coupling into analog circuits while maintaining high density integration.
Solution Approach 2:
A grounded guard band is introduced as an intermediary element between analog and digital circuits. This conductive ground barrier acts as a shield that intercepts and directs digital noise to ground, preventing it from reaching sensitive analog circuits. The guard band serves as a mediator that allows close proximity placement while maintaining signal integrity.
2Productivity
If multiple analog-to-digital converters are densely packaged on a single board, then conversion capacity is improved, but signal integrity deteriorates
Solution Approach 1:
Different regions of the circuit board are assigned different electrical characteristics. The analog region provides a low-noise environment for analog signals, while the digital region accommodates high-speed digital circuits. Each region has optimized ground plane connectivity and trace routing appropriate to its function, allowing high conversion capacity while maintaining signal integrity through localized environmental control.
Solution Approach 2:
The problem of noise interference is solved by adding the ground plane dimension to the board layout. By utilizing multiple board layers and creating three-dimensional ground structures with vertical via connections, the design provides noise isolation pathways that do not interfere with the planar signal routing, enabling high-density packaging without compromising signal integrity.
3Ease of manufacture
If digital and analog ground planes are combined into a single ground structure, then manufacturing simplicity is improved, but noise coupling increases
Solution Approach 1:
The ground plane is segmented into separate analog and digital portions that are electrically isolated except at controlled connection points. This segmentation prevents noise coupling while maintaining a relatively simple manufacturing process by using standard PCB ground plane techniques and via connections.
Solution Approach 2:
The potential harm of complex multi-layer ground structures is converted into benefit by using the manufacturing complexity to create well-defined ground isolation. The segmented ground planes with controlled via connections transform what could be a manufacturing burden into a noise-reduction feature, where the structured approach to ground plane creation directly serves the noise isolation objective.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design significantly reduces digital noise interference, ensuring the integrity of analog signals and allowing for fully digital acquisition electronics outside the tub enclosure, enhancing the reliability and accuracy of gamma ray detection in nuclear medicine applications.
Implementation Method 1
a grounded, conductive band interposed between them... effectively shielding analog circuits from digital noise
Implementation Method 2
a ground plane with two separate, grounded portions, with a first of the portions underlying the digital circuit and a second portion underlying the analog structure
Data Source
AI summary
A circuit board which has a high speed digital circuit in close proximity to a sensitive analog structure has a grounded, conductive band interposed between them and a ground plane with two separate, grounded portions, with a first of the portions underlying the digital circuit and a second portion underlying the analog structure. In an exemplary embodiment, the circuit board has a high density of analog-to-digital converter integrated circuits, each with two analog input signals and ten parallel high speed digital output signals corresponding to each input signal. A grounded, conductive band is placed on the board between the inputs and outputs of the integrated circuit, and a ground plane is provide which has separate, interleaved analog and digital areas, with the digital area underlying only portions of the board having digital signals and structures and the analog area underlying only portions of the board having analog signals and structures.