Hybrid Radar Fill Level Sensor Analog-Digital Correlation
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Solution Overview
Problem
Existing fill level measuring devices using continuous wave radar face challenges with analog circuit technology's precision issues and digital signal processing's signal-to-noise ratio and measurement time, particularly in achieving high-precision time integration and efficient sampling of high-frequency reflection signals.
Innovation Solution
A hybrid correlation receiver is implemented, combining analog circuit technology for mixing signals with digital integration, using an analog/digital converter to sample and quantify the mixer output signal, allowing for precise temporal integration and reducing sampling frequency requirements, thereby improving measurement accuracy and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If analog circuit technology is used for signal processing, then measurement precision is improved, but reliability deteriorates due to component tolerances, aging effects, and temperature dependence
Solution Approach 1:
The signal processing system is segmented into distinct functional blocks: analog mixing stage, analog-to-digital conversion stage, and digital integration stage. This segmentation allows each stage to be optimized independently, combining the precision benefits of analog circuitry with the stability of digital processing.
Solution Approach 2:
An analog-to-digital converter is introduced as an intermediary between the analog mixing stage and the digital integration stage. This intermediary enables the system to leverage the precision of analog signal mixing while transitioning to the reliability of digital signal processing for integration and evaluation.
2Reliability
If digital signal processing is used for correlation analysis, then reliability is improved, but measurement precision deteriorates due to reduced signal-to-noise ratio and increased measurement time
Solution Approach 1:
The correlation analysis process is segmented into analog mixing (for signal correlation) and digital integration (for precise measurement). This segmentation preserves the signal-to-noise ratio benefits of analog processing while achieving the precision and reliability of digital integration.
Solution Approach 2:
The analog-to-digital converter serves as a mediator that captures the correlated signal with high signal-to-noise ratio from the analog stage and transfers it to the digital stage for precise integration, thereby maintaining both signal quality and measurement precision.
3Measurement precision
If high-frequency reflection signals are sampled with high sampling frequency, then measurement precision is improved, but productivity deteriorates due to increased data processing requirements
Solution Approach 1:
The sampling process is segmented into essential sampling at moderate frequency followed by digital integration. This segmentation achieves sufficient measurement precision without requiring excessively high sampling frequencies, thereby maintaining system productivity.
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 approach enables high-precision fill level determination with reduced interference and measurement time, overcoming the limitations of purely analog or digital signal processing methods by leveraging the strengths of both technologies in a hybrid system.
Implementation Method 1
the electromagnetic waves are emitted into the space to be measured as a free-space wave via a transmitter designed as an antenna
Implementation Method 2
the transmit signal is at least partially reflected at the medium and is received by a receiver as a reflection signal
Implementation Method 3
the correlator has an analog mixer with which the reflection signal and the derived signal being derived from the transmit signal are mixed with the analog mixer into a mixer output signal
Implementation Method 4
the correlator has an analog/digital converter with which the mixer output signal is sampled and quantized into a digital mixer output signal
Implementation Method 5
the correlator has a digital integrator with which a sequence of digital mixer output signals is digitally integrated into the correlation outcome
Data Source
AI summary
A method for determining the fill level of a medium involves continuous wave radar measurement and a corresponding fill level measuring device. A coded transmit signal is emitted by a transmitter, reflected at the medium, and received by a receiver as a reflection signal. The reflection signal and a signal derived from the transmit signal are subjected to a correlation analysis, and a correlation outcome results. A control and evaluation unit determines the time offset of the correlated signals with the correlation outcome, and uses it to determine the fill level of the medium. The reflection signal and the derived signal are mixed with the analog mixer into a mixer output signal that is sampled and quantized to a digital mixer output signal. The correlator has a digital integrator with which a sequence of digital mixer output signals is digitally integrated into the correlation outcome.