Delta-Sigma Receiver Circuit for Compact Touch Input Sensing
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Solution Overview
Problem
As input devices become more complex with increasing numbers of sensor electrodes, the processing demands on the processing system increase, requiring more area, reduced-size processing circuitry, or more time for signal processing, which is not feasible due to space and cost constraints, especially in devices with integrated display devices.
Innovation Solution
A processing system comprising a delta-sigma modulator with an integrator, quantizer, feedback digital-to-analog converter, and common-mode feedback arrangement, integrated within an analog front-end or receiver circuitry, resulting in a significantly smaller size than conventional systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pulse code modulation (PCM) is used to achieve high signal quality, then signal-to-noise ratio is improved, but power consumption increases and battery life decreases
Solution Approach 1:
The patent replaces traditional PCM encoding with a delta-sigma modulation scheme that uses 1-bit quantization instead of multi-bit quantization. This substitution fundamentally changes the encoding mechanism to reduce computational complexity and power consumption while maintaining acceptable signal quality through oversampling and noise shaping techniques.
Solution Approach 2:
The patent changes the sampling rate parameter significantly by using oversampling (sampling at rates much higher than the Nyquist rate). This parameter change allows the system to achieve high signal-to-noise ratio through averaging effects while using simpler 1-bit quantization, thereby reducing power consumption compared to traditional PCM with lower sampling rates.
2Reliability
If direct sequence spread spectrum (DSSS) is used to achieve robust communication, then resistance to interference is improved, but signal attenuation increases
Solution Approach 1:
The patent introduces a time dimension by using code division multiplexing where multiple users share the same frequency spectrum but are separated by unique temporal codes. This dimensional change allows the system to achieve robust communication through code correlation while managing signal attenuation through proper code design and synchronization.
3Measurement precision
If oversampling is used to improve signal quality, then signal-to-noise ratio is improved, but data rate increases and power consumption increases
Solution Approach 1:
The patent extracts only the essential signal information using 1-bit quantization, discarding higher-order bits that contribute minimally to signal quality. This extraction approach allows oversampling to be used effectively for noise reduction without proportionally increasing the data rate, as each sample requires only 1 bit rather than multiple bits.
4Use of energy by moving object
If 1-bit quantization is used to reduce power consumption, then power consumption is reduced, but signal quality decreases
Solution Approach 1:
The patent uses periodic oversampling combined with noise shaping to distribute quantization errors in a controlled manner. By sampling at rates much higher than the signal bandwidth and shaping the quantization noise spectrum, the system achieves high effective signal-to-noise ratio despite using simple 1-bit quantization, thereby maintaining signal quality while reducing power consumption.
Data Source
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AI summary
A processing system, and associated input device and method are disclosed suitable for reducing a receiver size within the input device. The processing system comprises a delta-sigma modulator comprising one or more input nodes configured to receive a signal based on a sensor signal received from at least a first sensor electrode of the plurality of sensor electrodes. The delta-sigma modulator further comprises an integrator coupled with the one or more input nodes and configured to produce an integration signal, a quantizer coupled with an output of the integrator and configured to quantize the integration signal, and a feedback digital-to-analog converter (DAC) controlled based by the quantizer. The processing system further comprises a digital filter coupled with an output of the delta-sigma modulator and configured to mitigate a quantization noise of the quantizer.