Ultrasonic Parking Sensor Variable Bandwidth Filtering
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Solution Overview
Problem
Ultrasonic measuring systems for vehicles experience incorrect distance measurements due to signal dips caused by the oscillating element's decay frequency falling outside the bandpass filter's range after transmission, leading to false detection of obstacles.
Innovation Solution
Implementing a bandpass filter with a variable bandwidth that switches from a larger to a smaller value during the decay interval, accompanied by a low-pass filter with a switchable corner frequency, to filter signals at the ultrasonic transducer's output, ensuring accurate signal processing and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed bandpass filter with narrow bandwidth is used during the decay interval, then the signal-to-noise ratio is improved, but signal dips occur at the measurement output due to frequency mismatch
Solution Approach 1:
The bandpass filter's bandwidth is made dynamically adjustable rather than fixed. During the decay interval, the system automatically selects between a first bandwidth (wider) and a second bandwidth (narrower) based on the signal characteristics, allowing the filter to adapt to changing conditions and eliminate signal dips while maintaining signal-to-noise ratio
Solution Approach 2:
The filter's bandwidth parameter is changed based on the signal level detected during the decay interval. When the signal level exceeds a threshold, the system switches to the first bandwidth; otherwise, it uses the second bandwidth. This parameter change resolves the contradiction by selecting the appropriate bandwidth dynamically
2Reliability
If the ultrasonic transducer is muted or signal is disregarded during the decay interval, then false echo detection is prevented, but functional testing of the transducer becomes impossible
Solution Approach 1:
Instead of permanently muting the transducer during the decay interval, the system dynamically adjusts the filter bandwidth to accommodate the oscillating signal. This allows the transducer to remain functional and testable while preventing false echo detection through intelligent signal processing
3Reliability
If a wider bandwidth bandpass filter is used, then signal dips are eliminated, but the signal-to-noise ratio decreases and interference susceptibility increases
Solution Approach 1:
The system dynamically switches between different bandwidth settings based on real-time signal analysis. When the oscillating signal is detected (via threshold comparison), the wider first bandwidth is used to eliminate signal dips. When the signal decays below the threshold, the narrower second bandwidth is applied to maximize signal-to-noise ratio
Solution Approach 2:
The system continuously monitors the signal level during the decay interval and uses this feedback to determine which bandwidth setting to apply. This feedback mechanism ensures optimal performance by selecting the appropriate bandwidth based on actual signal conditions
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
This solution prevents signal dips at the measurement output, allowing for reliable echo detection and maintaining a good signal-to-noise ratio, enabling accurate distance measurement without suppressing the signal during the decay interval.
Implementation Method 1
exciting the vibrating element of the ultrasonic transducer to emit ultrasonic waves
Implementation Method 2
deactivating the vibrating element of the ultrasonic transducer to receive ultrasonic waves
Implementation Method 3
the transmit control and receive signal processing unit includes a bandpass filter for filtering the signals present at the measurement output of the ultrasonic transducer
Implementation Method 4
a low-pass filter with a switchable corner frequency is connected upstream of the signal level comparator
Implementation Method 5
the oscillator element of the ultrasonic transducer continues to oscillate for a certain period (settling interval), at a different, usually slightly higher frequency than the transmission frequency
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The invention relates to an ultrasonic measurement system (10) for parking assistance for vehicles, having an ultrasonic measuring transducer (12) comprising an oscillation element (14), which can be operated selectively both as an ultrasonic sensor and as an ultrasonic receiver. The ultrasonic measuring transducer (12) is connected to a transmitting actuation and receiving signal processing unit (18) for exciting the oscillating element (14) of the ultrasonic measuring transducer (12) in order to transmit ultrasonic waves for operating as an ultrasonic transmitter during a transmitting interval, and for subsequently deactivating the oscillating element (14) of the ultrasonic measuring transducer (12) in order to receive ultrasonic waves for operating same as an ultrasonic receiver during a receiving interval and for processing signals present at a measurement output (16) of the ultrasonic measuring transducer (12), wherein the oscillating element (14) settles to a stop after the excitation thereof ends during a settling interval. The transmitting actuation and receiving signal processing unit (18) comprises a band pass filter (30) for filtering the signals present at the measurement output (16) of the ultrasonic measuring transducer (12) during the settling interval and the receiving interval. The bandwidth of the band pass filter (30) can be switched from a larger first value to a smaller second value, starting from the beginning of a settling interval during at least one first phase of the settling interval to at least the end of the receiving interval following the settling interval.