Ultrasonic Sensor Notch Filtering for EMI-Robust Echo Reception
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Solution Overview
Problem
Ultrasonic sensors in vehicles are susceptible to electromagnetic interference, particularly from inductive charging of electric vehicles and keyless entry systems, which can lead to alias signals and reduced receive levels, complicating accurate distance detection.
Innovation Solution
Incorporation of an activatable notch filter in the ultrasonic sensor's connection circuitry that filters out interference at specific frequencies without affecting normal operation, using passive components like twin-T or twin-Pi filters, activated only when interference is detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If low-pass filters are used to remove electromagnetic interference, then interference is filtered out, but received ultrasonic echoes are also attenuated and maximum range is reduced
Solution Approach 1:
The patent applies a notch filter with a narrow stopband centered at the interference frequency (e.g., 150 kHz) rather than a broad low-pass filter. This localized filtering approach targets only the specific interference frequency while preserving the ultrasonic echo frequencies (e.g., 40-100 kHz), thus removing harmful interference without attenuating the desired signals and maintaining maximum detection range.
Solution Approach 2:
The patent changes the filtering parameters by using a notch filter with a specific center frequency and narrow bandwidth matched to the interference source, rather than using a low-pass filter with a cutoff frequency. This parameter optimization allows selective rejection of interference at 150 kHz while maintaining passband gain for ultrasonic frequencies, preserving receive level and detection range.
2Object-affected harmful factors
If high sampling frequencies are used to identify and process interference, then interference can be identified and processed, but costs increase
Solution Approach 1:
The patent applies analog notch filtering in the connection circuitry before the ADC sampling stage. This preliminary action removes the interference in the analog domain, so that subsequent digital sampling and processing operate on already-cleaned signals. This eliminates the need for high sampling rates specifically dedicated to interference identification, reducing system complexity and costs.
Solution Approach 2:
The notch filter acts as an intermediary component in the signal path, positioned between the piezoelectric element and the ADC. It mediates the signal by selectively removing interference frequencies before they reach the digital processing stage, allowing standard sampling rates to suffice and reducing overall system complexity.
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 notch filter effectively removes interference without attenuating the desired ultrasonic signals, ensuring reliable operation in environments with electromagnetic interference, particularly near electric vehicles or parking structures.
Implementation Method 1
a piezoelectric element that performs an electromechanical energy conversion and converts ultrasonic signals into electrical signals
Implementation Method 2
the connection circuitry comprises an activatable notch filter having a filter frequency, and the ultrasonic sensor is designed to activate the notch filter in the event of interference in the region of the filter frequency
Implementation Method 3
an ultrasound diaphragm for emitting ultrasonic pulses and for receiving ultrasonic echoes
Implementation Method 4
Ultrasonic sensors emit ultrasonic pulses, which are reflected as ultrasonic echoes by objects in the environment
Data Source
AI summary
The invention relates to an ultrasonic sensor (14) for emitting ultrasonic signals and for receiving ultrasonic echoes, in particular for use on a vehicle (10), having an ultrasound diaphragm, a piezoelectric element (26) mounted on the ultrasound diaphragm, an amplifier circuit (36), and connection circuitry (28), which electrically connects the piezoelectric element (26) and the amplifier circuit (36), wherein the connection circuitry (28) comprises an activatable notch filter (38) having a filter frequency (fF), and the ultrasonic sensor (14) is designed to activate the notch filter (38) in the event of interference in the region of the filter frequency (fF) during reception of the ultrasonic echoes. The invention also relates to an ultrasonic detection system (50) having a plurality of ultrasonic sensors (14) for detecting an environment (24), in particular an environment (24) of a vehicle (10), on the basis of sensor information provided by the ultrasonic sensors (14), having a plurality of ultrasonic sensors (14) that are connected to each other via a data link (18), wherein one of the ultrasonic sensors (14) is in the form of a master (M) in order to receive the sensor information from at least one further ultrasonic sensor (14), which is in the form of a slave(S), and to process this sensor information in order to detect the environment (24) of the vehicle (10), wherein the ultrasonic sensors (14) are embodied as specified above. In addition, the invention relates to a driving assistance system (12) having at least one ultrasonic sensor (14) for providing sensor information, and having a control unit (16), wherein the at least one ultrasonic sensor (14) and the control unit (16) are connected to each other via a data link (18), and the control unit (16) is designed to receive the sensor information from the at least one ultrasonic sensor (14) and to process this sensor information in order to detect the environment (24) of the vehicle (10), wherein the at least one ultrasonic sensor (14) is embodied as specified above.