FMCW Radar Level Gauge Using Multi-Sweep Sampling for Low Power
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Solution Overview
Problem
Conventional frequency modulated continuous wave (FMCW) radar level gauges are power hungry, limiting their suitability for applications with restricted power sources, and face a tradeoff between measurement accuracy and power consumption, where increasing bandwidth reduces the measurable range unless the number of samples is increased, which in turn prolongs sweep time.
Innovation Solution
A level gauge system that combines two or more frequency sweeps to increase bandwidth without extending sweep time, allowing for a greater number of samples while maintaining power efficiency by spreading the measurement cycle over multiple sweeps, with processing circuitry updating the combined sample vector after each sweep to determine the distance to the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the bandwidth is increased to improve measurement accuracy, then the measurable range is reduced unless the number of samples is increased
Solution Approach 1:
The frequency sweep is divided into multiple segments (first frequency sweep and second frequency sweep with different center frequencies). Each segment provides a portion of the total bandwidth, allowing the system to achieve high measurement accuracy through combined bandwidth while maintaining the ability to measure long distances by processing segments separately and combining results.
Solution Approach 2:
The patent introduces a frequency domain dimension by using multiple frequency bands (first and second frequency sweeps with different center frequencies). This additional frequency dimension allows the system to increase effective bandwidth for accuracy without sacrificing range, as each frequency band can independently contribute to distance measurement across the full range.
2Measurement precision
If the number of samples is increased to maintain range with higher bandwidth, then the sweep time is prolonged
Solution Approach 1:
The total number of required samples is segmented across multiple frequency sweeps. Instead of requiring one long sweep with many samples, the system performs multiple shorter sweeps at different center frequencies, each contributing a subset of samples. This reduces the time commitment per sweep while achieving the same total sample count for accuracy.
Solution Approach 2:
The system uses periodic frequency sweeps at different center frequencies to collect samples. By repeating the sweeping process multiple times with different frequency centers and combining the samples, the system achieves high accuracy without requiring each individual sweep to be extremely long, thus reducing overall measurement time.
3Use of energy by moving object
If the sweep time is reduced to lower power consumption, then the number of samples is reduced which affects accuracy
Solution Approach 1:
The sampling process is segmented across multiple short frequency sweeps instead of one long sweep. Each short sweep consumes less power individually, but collectively they provide sufficient samples for accurate measurement. The power consumption is distributed over time rather than concentrated in a single long sweep.
Solution Approach 2:
The system uses periodic, short duration frequency sweeps to collect samples efficiently. By performing multiple brief sweeps at different frequencies and combining their samples, the system achieves the required measurement accuracy while keeping each individual sweep short enough to maintain low power consumption levels.
4Use of energy by moving object
If the microwave module active period is limited to reduce power consumption, then the sweep duration must be reduced
Solution Approach 1:
The total sweep duration is segmented into multiple shorter sweeps at different center frequencies. Each short sweep has a limited active period that consumes less power, but the combination of multiple segmented sweeps provides sufficient data for accurate measurement over the desired range.
Solution Approach 2:
The microwave module operates in periodic short bursts corresponding to individual frequency sweeps rather than continuous operation. This periodic activation with limited duration per cycle reduces average power consumption while maintaining measurement capability through multiple cycles at different frequencies.
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 a higher bandwidth for a given range without increasing sweep time, maintaining low power consumption and providing accurate distance measurements, while allowing for frequent updates of the measurement value.
Implementation Method 1
a microwave source arranged to generate a measurement signal comprising a first frequency sweep and a second frequency sweep
Implementation Method 2
receives microwaves reflected by said surface
Implementation Method 3
a mixer connected to the microwave source and the signal propagation device, and arranged to mix the measurement signal with the echo signal to form a first IF signal based on the first frequency sweep, and a second IF signal based on the second frequency sweep
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
A level gauge (1) using microwaves to determine a distance to a surface of a product in a tank, wherein a measurement signal comprises a first frequency sweep, and a second frequency sweep, and a mixer (25) is arranged to mix the measurement signal with an echo signal to form a first IF signal based on the first frequency sweep, and a second IF signal based on the second frequency sweep. Processing circuitry (11) is adapted to sample the first IF signal and the second IF signal, to form a combined sample vector including samples from each tank signal, and to determine the distance based on the combined sample vector. By combining the samples from two (or more) different sweeps, the number of samples and the bandwidth can both be increased, thus maintaining the range L. However, as the samples are obtained from two separate sweeps, the sweep time for each individual sweep does not need to be increased, and the average power consumption can be maintained.