Capacitive Sensor Noise Estimation via Code Division Multiplexing
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Solution Overview
Problem
Capacitive sensing devices face performance degradation due to the need to temporarily suspend drive signals for noise estimation, which limits flexibility and user experience.
Innovation Solution
A capacitive input sensor system that uses code division multiplexing to simultaneously apply distinct transmitter signals and estimate noise using a dedicated noise descrambler, allowing for real-time noise estimation and adjustment of operational parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If drive signals are temporarily suspended to estimate system noise, then noise estimation accuracy is improved, but device performance and signal-to-noise ratio deteriorate
Solution Approach 1:
The patent applies preliminary action by continuously estimating noise using code division multiplexing before it significantly impacts performance. The system proactively monitors noise levels through dedicated noise estimation circuits that process spread spectrum signals, allowing the device to adjust operational parameters in advance rather than reactively suspending drive signals after performance degradation occurs.
Solution Approach 2:
The patent implements continuity of useful action by maintaining continuous drive signals to transmitter electrodes while simultaneously performing noise estimation through code division multiplexing. The spread spectrum technique allows noise estimation to occur continuously in the background without interrupting the primary sensing function, ensuring both measurement accuracy and device performance are maintained throughout operation.
2Measurement precision
If drive signals are suspended for noise estimation, then noise measurement precision is improved, but productivity and operational flexibility are reduced
Solution Approach 1:
The system performs preliminary noise estimation continuously using code division multiplexing, allowing the device to maintain high productivity by adjusting operational parameters proactively before noise becomes a limiting factor. This eliminates the need to suspend operations for noise measurements, thereby preserving operational flexibility and throughput.
Solution Approach 2:
The patent enables continuous useful action by implementing noise estimation that occurs simultaneously with normal sensing operations through code division multiplexing. The dedicated noise estimation circuits process signals in parallel with the primary sensing function, ensuring both noise measurement precision and operational productivity are maintained without interruption.
3Productivity
If code division multiplexing is used to simultaneously apply multiple transmitter signals, then signal utilization efficiency is improved, but signal interference and noise estimation difficulty increase
Solution Approach 1:
The patent applies segmentation by dividing the noise estimation function into a dedicated noise estimation circuit separate from the primary signal processing path. The code division multiplexing technique segments the signal space, allocating specific codes for transmitter signals and a dedicated code for noise estimation, thereby simplifying noise detection despite multiple simultaneous signals.
Solution Approach 2:
The patent uses an intermediary approach by introducing a dedicated noise estimation circuit that acts as a mediator between the multiple transmitter signals and the noise measurement function. This intermediary circuit processes signals through code division multiplexing, isolating noise components from the complex mixed signals and reducing the difficulty of noise estimation.
Data Source
AI summary
A processing system configured to sense an input object in a sensing region of a sensing device including a transmitter module coupled to a first transmitter electrode and a second transmitter electrode and configured to simultaneously apply a first transmitter signal to the first transmitter electrode and a second transmitter signal to the second transmitter electrode, wherein the first transmitter signal is based on a first one of a plurality of distinct codes and the second transmitter signal is based on a second one of the plurality of distinct codes. The processing system also includes a receiver module including receiver circuitry coupled to a first receiver electrode and configured to receive a first resulting signal with the first receiver electrode, the first resulting signal comprising effects corresponding to the first and second transmitter signals and a noise component. The processing system is configured to determine an estimate of the noise component using a third one of the plurality of distinct codes which is not associated with a transmitter signal.