Capacitive Touch Pad Shield Layout for RF Antenna Transmission
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Solution Overview
Problem
Existing capacitance modules in touch pads face challenges with radio frequency interference, where electrical shielding necessary to prevent noise from processor-based devices can hinder the transmission and reception of radio frequencies.
Innovation Solution
The implementation of a stack of layers including a capacitive sensor layer with electrodes, an antenna on the same layer, and a shield feature, such as a ground ring, positioned between the electrodes and the antenna to prevent electrical interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrical shielding is added to prevent noise from interfering with touch pad functions, then touch pad reliability is improved, but radio frequency transmission and reception are blocked
Solution Approach 1:
The shield feature is divided into multiple discrete sections rather than forming a continuous enclosure. These segmented shield sections are positioned between the antenna and electrodes to block electrical interference while leaving gaps that allow radio frequency signals to pass through, thus resolving the contradiction between shielding effectiveness and RF transmission
Solution Approach 2:
The shield feature acts as an intermediary element positioned between the antenna and the electrodes/capacitive sensor. It mediates the interaction by blocking electrical noise from reaching the sensitive capacitive components while its segmented structure and positioning allow RF signals to penetrate through, thus protecting touch pad functions without blocking communication
2Object-affected harmful factors
If the antenna is placed near the touch pad to allow radio frequencies through shielding, then radio frequency transmission is improved, but antenna tuning becomes difficult and manufacturing complexity increases
Solution Approach 1:
The segmented shield feature serves as a mediator that enables the antenna to be positioned close to the touch pad components without requiring complex tuning. The shield's specific configuration (sections with gaps) automatically provides the necessary RF penetration while blocking electrical interference, simplifying the antenna design and manufacturing process
Solution Approach 2:
The shield feature has different properties in different locations - solid conductive sections for blocking electrical interference and gaps between sections for allowing RF transmission. This local variation in shielding quality enables simultaneous achievement of EMI protection and RF transmission without complex tuning
3Object-affected harmful factors
If the antenna is positioned to transmit signals around touch pad components, then radio frequency communication is maintained, but power consumption increases
Solution Approach 1:
The segmented shield acts as an intermediary that provides a direct transmission path for RF signals through its gaps, eliminating the need for the antenna to transmit signals around the touch pad components. This direct path reduces transmission distance and power consumption while maintaining communication functionality
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 configuration allows for effective radio frequency transmission and reception while maintaining the integrity of the capacitive touch pad functions, reducing manufacturing complexities, and optimizing power usage.
Implementation Method 1
capacitive touch pads often require electrical shielding to prevent noise from the processor-based device from interfering with normal touch pad functions
Data Source
AI summary
An apparatus may include a substrate including a capacitance sensing electrode, an antenna on the substrate, and a shield feature between the electrodes and the antenna.