FMCW Radar Fill Level Calibration via Oscillating Reference Reflector
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Solution Overview
Problem
FMCW radar fill-level measuring devices face accuracy degradation due to factors like accretion, temperature effects, and environmental conditions, making it difficult to identify and distinguish reference reflectors in echo functions, especially when other reflectors are present.
Innovation Solution
Introducing a reference reflector that oscillates at a frequency less than half the repetition frequency, allowing for the identification of its position through time changes in echo functions and movement spectra, enabling reliable calibration and monitoring of the fill-level measuring device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a static reference reflector is used for calibration, then the calibration process can be performed, but the reference reflector cannot be reliably identified when other reflectors are present in the environment
Solution Approach 1:
The reference reflector is transformed from a static object to a dynamic one by making it oscillate at a specific frequency. This dynamic behavior creates a distinctive temporal signature in the echo function that allows reliable identification even when multiple reflectors are present. The oscillation frequency serves as a unique identifier that distinguishes the reference reflector from other stationary reflectors in the environment.
Solution Approach 2:
The reference reflector executes periodic oscillations at a frequency less than half the repetition frequency of the transmission signals. This periodic motion creates corresponding periodic variations in the echo function at the known distance position, enabling reliable detection and identification through frequency analysis. The periodic action transforms a static calibration target into a dynamically identifiable reference.
2Reliability
If reference reflectors are placed at known distances for calibration, then calibration can be performed, but the position cannot be uniquely determined due to interference from other reflectors
Solution Approach 1:
By making the reference reflector oscillate, the system creates a time-varying signal signature that encodes the position information. The oscillation creates periodic modulations in the echo function that can be analyzed to extract unique position information, preventing confusion with other stationary reflectors that do not produce such temporal variations.
Solution Approach 2:
The system uses the oscillation frequency as a feedback mechanism to identify and confirm the position of the reference reflector. By analyzing the temporal variations in the echo function at the known distance and comparing them against the expected oscillation frequency, the system can reliably confirm the presence and position of the reference reflector despite the presence of other reflectors.
3Adaptability or versatility
If multiple reflectors are present in the container, then the measurement environment is realistic, but the echo function contains multiple maxima that cannot be distinguished
Solution Approach 1:
The oscillating reference reflector introduces a dynamic element that creates temporal variations in the echo function. This allows the system to distinguish the reference reflector from other stationary reflectors by analyzing the time-dependent behavior of the echo signals, even when multiple reflectors are present in a realistic measurement environment.
Solution Approach 2:
The reference reflector is made to vibrate mechanically at a specific frequency, creating characteristic modulations in the reflected signal. This mechanical vibration transforms the static reflection problem into a dynamic signal processing problem, where frequency analysis can separate the reference reflector signal from other stationary reflector signals in the mixture.
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 method enhances the accuracy of fill-level measurements by reliably identifying the reference reflector position, even in the presence of other reflectors, and allows for real-time monitoring and calibration, improving the device's operational stability and precision.
Implementation Method 1
coherent frequency modulation, continuous wave radar (FMCW radar, fill-level measuring device) for measuring a fill level
Implementation Method 2
receives as received signals their fractions reflected on reflectors located in the beam path of the transmission signals back to the fill-level measuring device
Implementation Method 3
a reference reflector executing oscillations toward the fill-level measuring device with an oscillation frequency amounting to less than half the repetition frequency
Data Source
AI summary
A method is based on measuring a distance to a reference reflector arranged at a known distance, in order to calibrate and/or monitor a coherent frequency modulation, continuous wave radar, fill-level measuring device, wherein the reference reflector can be reliably identified. To this end, a reference reflector executing oscillations toward the fill-level measuring device with an oscillation frequency is used, which is inserted in the beam path of periodically linearly frequency modulated transmission signals transmitted from the fill-level measuring device. The fill-level measuring device receives fractions of the transmission signals reflected back on reflectors in the container and records based on these received signals and their time correlation relative to the respectively associated transmission signal for each received signal an echo function, which shows the amplitudes of the received signal as a function of the associated position of the associated reflector. Based on the time change of a plurality of sequentially recorded echo functions and the oscillation frequency of the reference reflector, the position of the reference reflector in the echo functions is identified and its reference reflector position determined.