FMCW Radar Level Gauge Timing Control for Low Power
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Solution Overview
Problem
Conventional FMCW radar level gauge systems are power hungry, making them less suitable for applications with limited power sources, such as field devices or wireless devices, due to the high energy consumption required for accurate and temperature-stable timing.
Innovation Solution
The radar level gauge system employs two different timing signal generating circuits: a high-performance, temperature-compensated crystal oscillator for measurement and sampling, and a less accurate RC-oscillator for signal processing, allowing the system to be controlled between a measurement state and a signal processing state to reduce energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-performance temperature-compensated crystal oscillator is used for timing, then timing accuracy and temperature stability are improved, but energy consumption increases
Solution Approach 1:
The system dynamically switches between two timing signal generating circuits based on operational state. During measurement state, the high-performance temperature-compensated crystal oscillator is enabled for accurate timing. During signal processing state, the system switches to a lower-power RC-oscillator, reducing energy consumption while maintaining necessary performance for each operational phase.
Solution Approach 2:
The timing signal generation function is segmented into two separate circuits: a high-performance temperature-compensated crystal oscillator for measurement operations requiring high accuracy, and a low-power RC-oscillator for signal processing operations where high precision is less critical. This segmentation allows the system to use only the necessary performance level for each task, optimizing energy consumption.
2Measurement precision
If continuous high-performance timing is maintained, then measurement accuracy is improved, but power consumption increases making the system unsuitable for battery-powered applications
Solution Approach 1:
The high-performance timing circuit is activated periodically only during measurement state rather than continuously. The system alternates between measurement state (using temperature-compensated crystal oscillator) and signal processing state (using RC-oscillator), achieving necessary measurement accuracy while significantly reducing average power consumption for battery-powered applications.
Solution Approach 2:
The system changes the timing performance parameter based on operational requirements. During measurement, high timing precision is maintained; during signal processing, the timing precision requirement is relaxed and a lower-power circuit is used. This parameter change allows the system to meet accuracy requirements only when necessary.
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 significantly reduces energy consumption, enabling the use of FMCW-type radar level gauge systems in locally energized or loop-powered applications, while maintaining the necessary accuracy and stability for filling level determination.
Implementation Method 1
a microwave signal source controllable to generate an electromagnetic transmit signal with a time-varying frequency; a propagation device connected to the microwave signal source and arranged to propagate the electromagnetic transmit signal towards a surface of the product in the tank, and to propagate an electromagnetic surface echo signal resulting from reflection of the transmit signal at the surface back from the surface
Implementation Method 2
a mixer connected to the microwave signal source and to the propagating device and configured to mix the transmit signal and the surface echo signal to form a mixer signal, having a frequency equal to the frequency change of the transmitted signal that has taken place during the time delay
Data Source
Figure 1~2
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AI summary
A radar level gauge system (1) controllable between a measurement state and a signal processing state. In the measurement state a first timing signal circuit (40) is enabled, a microwave signal source (20) generates a transmit signal (S_T) with a time-varying frequency being related to first timing signals from the first timing signal generating circuitry, and a sampler (34) samples a mixer signal at sampling times related to the first timing signals. In the signal processing state, the first timing signal circuit is disabled, and a signal processor (38) determines the filling level based on the sampled values of the mixer signal using second timing signals from a second timing signal generating circuit (36).