PTS Receiver Duty Cycle Modulation for Noise Reduction
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Solution Overview
Problem
Periodic time-synchronous receivers, such as those in capacitive touchscreens, are susceptible to noise at fundamental measurement frequencies and their harmonics, which existing noise reduction methods like shielding and filtering struggle to address effectively, especially in resource-constrained applications.
Innovation Solution
A duty cycle controller adjusts the duty cycle of a gating signal applied to a transmission gate within the receiver, selectively eliminating harmonic, sub-harmonic, and intra-harmonic noise components by varying the pulse duration, allowing the receiver to reduce or eliminate noise without the need for additional filtering techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If shielding, frequency hopping, spread spectrum, pre-selection filtering and signal amplification are used to reduce noise, then noise reduction is achieved, but device complexity and resource consumption increase
Solution Approach 1:
The patent changes the operating parameters of the periodic time-synchronous receiver, specifically varying the duty cycle of the gating signal and adjusting the measurement frequency. By modulating these parameters, the receiver can avoid noise at fundamental and harmonic frequencies without requiring complex filtering hardware or additional processing resources.
Solution Approach 2:
The patent employs periodic gating signals with variable duty cycles to sample the input signal. This periodic action, combined with frequency modulation, creates time-synchronous detection that inherently rejects periodic noise components while maintaining sensitivity to the desired signal, avoiding the need for complex continuous filtering systems.
2Object-affected harmful factors
If shielding, frequency hopping, spread spectrum, pre-selection filtering and signal amplification are used to reduce noise, then noise reduction is achieved, but power consumption increases
Solution Approach 1:
The receiver adjusts its measurement frequency and gating duty cycle parameters to operate in noise-free frequency windows. This parameter optimization allows the system to achieve noise reduction through intelligent parameter selection rather than continuous high-power signal processing, significantly reducing average power consumption while maintaining detection performance.
Solution Approach 2:
Instead of continuously applying strong filtering and amplification across all frequencies, the system applies partial action by selectively measuring only during optimal time windows when noise is minimized. The variable duty cycle gating applies detection only when conditions are favorable, reducing overall power consumption while achieving effective noise reduction.
3Object-affected harmful factors
If shielding, frequency hopping, spread spectrum, pre-selection filtering and signal amplification are used to reduce noise, then noise reduction is achieved, but physical space requirements increase
Solution Approach 1:
The patent achieves noise reduction through software-based parameter optimization (frequency and duty cycle adjustment) rather than physical filtering components. This virtual approach to noise rejection eliminates the need for additional physical space dedicated to shielding materials, filters, and other hardware-based noise reduction components.
4Measurement precision
If periodic time-synchronous receiver measures very small changes in capacitance, then measurement precision is improved, but susceptibility to external noise increases
Solution Approach 1:
The receiver uses periodic gating signals synchronized to the measurement frequency to sample capacitance changes. This time-synchronous periodic measurement approach integrates signal detection with noise rejection by capturing signals only during specific phases of the periodic cycle when noise interference is minimized, thereby maintaining high measurement precision while reducing noise susceptibility.
Solution Approach 2:
The system dynamically adjusts the measurement frequency and gating duty cycle parameters to optimize the signal-to-noise ratio for very small capacitance measurements. By varying these parameters, the receiver can maintain high measurement precision for minute capacitance changes while avoiding frequency ranges where noise interference is prominent.
Data Source
AI summary
Methods, systems and apparatus are provided that implement duty cycle modulation of periodic time-synchronous (PTS) receivers for noise reduction. For instance, when a composite signal is received at a PTS receiver, the composite signal includes an input signal and a noise signal. The composite signal is input to a transmission gate of the PTS receiver. The PTS receiver also receives a gating control input signal that turns the transmission gate on and off. A duty cycle controller adjusts a variable duty cycle of the gating control input signal applied to the transmission gate to output an output signal from the transmission gate such that one or more components of the noise signal present in the composite signal is/are reduced in the output signal that is output by the transmission gate.