Impedance Ratio Current Conveyor for Touch Sensor Linearity
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Solution Overview
Problem
Proximity sensor devices face challenges in maintaining linearity due to increasing background capacitance, which leads to device noise and interference, affecting the accuracy of touch sensor signals.
Innovation Solution
The implementation of an impedance ratio-based current conveyor with a staging circuit and current mirrors to generate scaled signals, reducing interference and noise by attenuating the input signal using a ratio of impedances, and an auxiliary component to process the scaled signal for output generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If auxiliary circuits are used to offset large sensor background capacitance, then the background capacitance is reduced, but device noise increases
Solution Approach 1:
The patent introduces an impedance ratio-based current conveyor as an intermediary component between the sensor electrode and auxiliary circuits. This current conveyor uses a staging circuit with impedance ratios to generate an attenuated input signal that is then processed by current mirrors to produce a scaled signal. This intermediary approach allows the auxiliary circuits to offset background capacitance while operating on a reduced-signal-level that generates less noise, thus resolving the contradiction between capacitance offset and noise generation.
2Quantity of substance
If background capacitance increases, then the sensor can detect larger objects, but linearity maintenance becomes difficult
Solution Approach 1:
The patent changes the signal processing parameters by introducing impedance ratios in the staging circuit. The current conveyor transforms the resulting signal through a series of impedance transformations, where the input signal is attenuated by a factor determined by the impedance ratio (Z1/Z2). This parameter change allows the system to process signals from sensors with large background capacitance while maintaining linearity in the processing stages, as the transformed signal operates in a linear regime despite the large original capacitance.
3Object-affected harmful factors
If the input signal is attenuated using impedance ratios, then interference and noise are reduced, but signal processing complexity increases
Solution Approach 1:
The patent replaces complex digital signal processing mechanisms with an analog impedance-based attenuation system. The staging circuit uses passive impedance elements (resistors, capacitors) arranged in a specific configuration to achieve signal attenuation through natural electrical impedance ratios. This mechanical/electrical substitution eliminates the need for complex digital algorithms or active control mechanisms, reducing overall system complexity while effectively attenuating interference and noise through the inherent properties of the impedance network.
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 solution effectively reduces interference and device noise, allowing for improved usability and accuracy in detecting input objects within the sensing region by maintaining linearity in processing stages.
Implementation Method 1
a set of current mirrors configured to generate the scaled signal from the input signal
Implementation Method 2
generating an input signal from the resulting signal using a ratio of a first impedance to a second impedance
Data Source
AI summary
An input device associated with a sensing region is disclosed. The input device includes: a first sensor electrode associated with the sensing region and configured to propagate a resulting signal; an first auxiliary component configured to generate an output using a scaled signal; and a first impedance ratio-based current conveyor coupled to the first sensor electrode and including: a staging circuit configured to generate an input signal using the resulting signal and a ratio of a first impedance to a second impedance; and a set of current mirrors configured to generate the scaled signal from the input signal.