Radar Level Frequency Synthesizer With Low-Noise DDS Output
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Solution Overview
Problem
Existing frequency synthesizers for level measuring devices using radar principles face challenges in maintaining high measurement accuracy due to high circuitry costs and spectral interference from direct digital synthesizers, especially when producing frequency signals with small differences, which are necessary for accurate distance measurements.
Innovation Solution
A frequency synthesizer utilizing a single direct digital synthesizer is operated to minimize noise spectrum by maximizing digital/analog converter resolution, oversampling, and avoiding phase truncation noise lines, with optional bandpass filtering and frequency dividers to enhance signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If two separate direct digital synthesizers are used to generate the first and second frequency signals, then frequency generation capability is improved, but circuit complexity and cost increase significantly
Solution Approach 1:
The patent merges the functions of two separate direct digital synthesizers into a single direct digital synthesizer. The first frequency signal is generated by processing the reference frequency signal through the direct digital synthesizer, while the second frequency signal is derived by frequency division of the first frequency signal. This consolidation reduces circuit complexity and component count while maintaining the capability to generate both frequency signals with small frequency differences.
2Measurement precision
If direct digital synthesizer is used to generate frequency signals with small difference, then frequency precision is improved, but noise spectrum and spectral interference increase
Solution Approach 1:
The patent extracts the second frequency signal from the first frequency signal through frequency division, rather than generating it independently. This extraction approach removes the noise spectrum and spectral interference that would be generated by a second independent direct digital synthesizer, while still providing the required frequency precision for small frequency differences.
Solution Approach 2:
The first frequency signal acts as an intermediary between the reference frequency signal and the second frequency signal. The direct digital synthesizer generates the first frequency signal with high precision, and the frequency divider converts it to the second frequency signal, thereby avoiding direct generation of both signals from separate synthesizers and reducing overall noise.
3Measurement precision
If high sampling rate is used to detect reflected electromagnetic waves, then measurement accuracy is improved, but circuitry cost increases excessively
Solution Approach 1:
The patent employs periodic action through frequency division, where the second frequency signal is generated by dividing the first frequency signal by an integer factor. This periodic division approach allows accurate detection of reflected electromagnetic waves at lower sampling rates, as the frequency division creates a scaled-down version of the original signal that can be processed more economically while maintaining measurement accuracy.
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 reduces noise interference, allowing for accurate and stable generation of frequency signals with small differences, improving measurement accuracy and reducing circuit complexity and costs.
Implementation Method 1
a direct digital synthesizer (5) which is operated such that only a noise spectrum is produced which is at least partially minimized
Implementation Method 2
a frequency divider (6) which derives the second frequency signal from the first frequency signal
Implementation Method 3
optional bandpass filtering and frequency dividers to enhance signal-to-noise ratio
Data Source
AI summary
A frequency synthesizer for a time base generator of a level measuring device which works according to the radar principle, with at least one first output for output of a first frequency signal, with at least one second output for output of a second frequency signal, and with a reference oscillator for producing a reference frequency signal, the first frequency signal and the second frequency signal having a small difference frequency relative to one another, the first frequency signal being producible by interaction of the reference oscillator with a direct digital synthesizer. The first frequency signal and second frequency signal can be generated with especially low noise by the second frequency signal being derived from the reference oscillator without interconnection of a direct digital synthesizer and the direct digital synthesizer being operated such that only a noise spectrum is produced which is at least partially minimized.