Capacitive Sensor Electrode Assembly With Filtered Drive Signal
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Solution Overview
Problem
Capacitive sensor devices in vehicles face interference issues due to unfavorable frequency spectra, particularly from radio signals in the AM band, leading to complex and costly measures to reduce interference.
Innovation Solution
An arrangement with a transmission arrangement that includes a filter component to adapt the input signal frequency, using a filter component to suppress harmonics and convert the input signal into a sinusoidal output, reducing interference by shaping the output signal with a Sallen-Key filter or RC low-pass filter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a rectangular signal is used for recharging the sensor element, then the sensor device can be operated with a simple charging mechanism, but the signal produces unfavorable frequencies that cause electromagnetic interference with radio signals
Solution Approach 1:
The patent applies parameter changes by transforming the signal waveform from a rectangular shape to a sinusoidal shape. This changes the frequency spectrum characteristics, eliminating the harmful harmonic frequencies present in rectangular waves while maintaining the essential charging function. The sinusoidal signal at 510 kHz matches the medium wave radio frequency, avoiding interference through parameter optimization.
Solution Approach 2:
The patent converts the potentially harmful rectangular signal with its broad frequency spectrum into a beneficial sinusoidal signal with a narrow frequency spectrum. By using a bandpass filter, the harmful harmonics are eliminated, and only the desired 510 kHz frequency remains, which coincidentally matches the radio frequency range, thereby avoiding interference rather than causing it.
2Object-generated harmful factors
If complex measures are taken to reduce interference from sensor device signals, then electromagnetic interference is reduced, but the device complexity and cost increase
Solution Approach 1:
The patent applies preliminary action by pre-shaping the signal waveform before it is transmitted to the sensor element. The bandpass filter is used in advance to generate a sinusoidal signal with the exact frequency needed (510 kHz), preventing the generation of harmful harmonics from the start. This proactive approach eliminates interference without requiring complex post-processing or additional shielding measures.
3Object-generated harmful factors
If a sinusoidal signal is generated directly by a voltage source, then the frequency spectrum is optimized to avoid interference, but the transmission arrangement complexity increases
Solution Approach 1:
The patent uses a bandpass filter as an intermediary component between the voltage source and the sensor element. This intermediary transforms the simple rectangular voltage signal into a sinusoidal signal with the desired frequency characteristics. The bandpass filter acts as a mediator that reconciles the simplicity of the voltage source with the requirements for a clean sinusoidal output, adding minimal complexity while achieving the desired signal quality.
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
The solution effectively filters out unwanted frequencies, preventing electromagnetic interference and ensuring reliable detection of activation actions near the vehicle, such as opening doors or tailgates, with a simple structural design.
Implementation Method 1
a transmission arrangement for providing an output signal by a frequency-dependent change in an electrical input signal of the transmission arrangement
Implementation Method 2
the transmission arrangement has at least one filter component in order to carry out the frequency-dependent change
Implementation Method 3
at least one sensor electrode for detecting a change in an environment of the vehicle
Data Source
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AI summary
The invention relates to an assembly (10) for a capacitive sensor device (20) of a vehicle (1), in particular for control and/or evaluation of the capacitive sensor device (20) for detection of an activation action in the vehicle (1), comprising: - at least one sensor electrode (20.1) for detecting a change in the surroundings of the vehicle (1), - a transmission assembly (30) for providing an output signal (A) by way of a frequency-dependent change of an electric input signal (E) of the transmission assembly (30), and - an output (30.2) of the transmission assembly (30) which is electrically connected to the sensor electrode (20.1) so as to operate the sensor electrode (20.1) with the output signal (A), the transmission assembly (30) having at least one filter component (30.4, 30.5) in order to carry out the frequency-dependent change.