Touch Screen Backplane Noise Mitigation Near NFC Circuitry
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Solution Overview
Problem
Electronic devices with touch screens and near-field communication (NFC) circuitry face noise interference issues due to the proximity of NFC circuitry to touch sensors and displays, degrading signal integrity and performance.
Innovation Solution
A chiplet architecture with a mesh of routing traces on a backplane, configured to repeat signals, minimize trace length, and optimize routing to reduce noise interference, including using alternating chiplets and twisted pair configurations to mitigate electromagnetic noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If NFC circuitry is placed in proximity to touch sensor panel and display, then wireless communication functionality is improved, but electromagnetic noise interference increases degrading signal integrity
Solution Approach 1:
A ground plane is introduced as an intermediary between the NFC circuitry and the touch sensor panel/display components. This ground plane acts as a shield to block electromagnetic noise from the NFC circuitry from interfering with the sensitive analog signals of the touch sensor and display, thus resolving the contradiction by allowing close proximity placement while maintaining signal integrity through the mediating ground plane structure.
2Reliability
If routing trace length is reduced by using chiplet architecture, then signal integrity is improved, but device complexity increases due to multiple chiplets and mesh routing
Solution Approach 1:
The display and touch sensor components are divided into multiple smaller chiplets arranged in a mesh pattern on the backplane. This segmentation reduces the routing trace length from each chiplet to the nearest ground plane and minimizes the area over which electromagnetic noise can accumulate, thereby improving signal integrity despite the increased structural complexity of having multiple discrete components.
Solution Approach 2:
The chiplets are arranged in a two-dimensional mesh pattern on the backplane rather than a linear or single-plane configuration. This dimensional arrangement optimizes the routing trace length by providing multiple short paths to ground plane references and allows for better spatial distribution of components, improving signal integrity while managing the complexity through systematic geometric organization.
3Object-affected harmful factors
If routing traces are optimized to minimize electromagnetic field exposure, then noise mitigation is improved, but routing complexity and design difficulty increase
Solution Approach 1:
Different regions of the backplane are designed with different routing characteristics optimized for their specific functions. Analog signal routes are positioned closer to ground planes with shorter trace lengths, while digital or less sensitive routes can have different configurations. This local optimization mitigates noise for critical signals without requiring complete redesign of the entire routing system, thus managing design complexity while improving noise mitigation where it matters most.
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
The solution effectively reduces noise-induced voltage drops, preserving signal integrity and improving touch sensing performance by minimizing electromagnetic interference between NFC circuitry and touch screens.
Implementation Method 1
a plurality of routing traces can be routed in a twisted pair configuration (e.g., to cancel open loop area)
Data Source
AI summary
Mitigation techniques can be used to reduce noise generated by wireless communication circuitry (e.g., near-field communication circuitry) in an electronic device including a display, touch, and wireless communication circuitry. In some examples, a touch screen can have a backplane including a mesh of routing traces connected to an array of chiplets. In some examples, the chiplets can repeat signals to prevent the accumulation of noise induced by an NFC coil. In some examples, the ratio between vertical and horizontal resistances of routing traces can be configured to mitigate noise induced by the coil. In some examples, the routing traces of the mesh can be configured to share a common geometric centroid. In some examples, a plurality of routing traces can be routed in a twisted pair configuration. In some examples, the routing traces and chiplets can be routed to minimize traversal through regions of relatively high electromagnetic field.