FMCW Fill Level Sensor Power Peak Reduction

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Solution Overview

Problem

Fill level measuring devices using frequency-modulated continuous wave (FMCW) signals face power peaks in their mean power spectrum, which can exceed permissible transmission levels due to periods where the signal remains at a constant frequency during settling or warm-up times, violating regulatory limits.

Innovation Solution

The device operates by generating a transmission signal with a frequency ramp that only uses frequencies within a fundamental frequency interval, avoiding emission of constant frequency components during settling times, and utilizing a phase-locked loop to adjust frequencies, ensuring that only settled frequencies are used for measurement, thus eliminating or reducing power peaks in the mean power spectrum.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the transmission signal remains at a constant frequency during settling or warm-up times, then the device can stabilize its operation, but power peaks occur in the mean power spectrum exceeding permissible transmission levels

Engineering Contradiction:

Improvestability during settling timeVSAvoidmean power level

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The patent applies periodic action by implementing a frequency modulation scheme where the transmission signal alternates between frequency ramps and constant frequency periods. During settling time, instead of maintaining a constant frequency that causes power peaks, the system uses periodic frequency ramps that continuously sweep through the frequency range, thereby distributing the power spectrum and avoiding excessive mean power levels at any single frequency while still allowing the device to stabilize its operation.

Inventive Principle:

Principle #19Periodic action

2Power

If the transmission level is kept low to comply with regulatory limits, then power peaks are reduced, but the measurement signal strength decreases

Engineering Contradiction:

Improvemean power levelVSAvoidsignal strength

Core Design Contradiction:

PowerVSMeasurement precision

Solution Approach 1:

The patent applies parameter changes by dynamically modulating the frequency of the transmission signal through frequency ramps. By continuously varying the frequency parameter during settling time rather than maintaining a constant frequency, the system distributes the transmitted power across a broader frequency spectrum. This allows compliance with regulatory mean power limits while maintaining sufficient signal strength for accurate measurements, as the energy is spread out rather than concentrated at a single frequency.

Inventive Principle:

Principle #35Parameter changes

3Power

If frequency ramps are used to distribute power across a larger frequency range, then power peaks are reduced, but the settling time increases

Engineering Contradiction:

Improvepower peak distributionVSAvoidsettling time

Core Design Contradiction:

PowerVSLoss of time

Solution Approach 1:

The patent implements periodic action by using repetitive frequency ramps that cycle through the frequency range. During settling time, the system performs multiple rapid frequency sweeps rather than maintaining a single constant frequency. This periodic frequency modulation distributes power across the spectrum while completing the settling process more quickly, as the continuous sweeping prevents power accumulation at any single frequency and allows the system to stabilize faster.

Inventive Principle:

Principle #19Periodic action

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 effectively reduces power peaks in the mean power spectrum, maintaining compliance with regulatory limits while ensuring reliable level measurements by distributing power across a larger frequency range during settling times, thereby avoiding excessive mean power levels.

Implementation Method 1

utilizing a phase-locked loop to adjust frequencies, ensuring that only settled frequencies are used for measurement

Methodology Applied

Scientific EffectPhase-locked loop:

Data Source

PatentUS10557743B2Reduction of power peaks in the spectrum of the mean power of fill level measuring devices

Publication Date: 2020.02.11 VEGA GRIESHABER GMBH & CO

AI summary

A fill level measuring device designed for the generation and emission of a transmission signal, wherein the transmission signal includes at least one frequency ramp. In order to determine the level of a filling material in a vessel, only frequencies within a fundamental frequency interval are used. In this case, the minimal frequency of the fundamental frequency interval is greater than the minimal frequency of the frequency ramp and/or the maximal frequency of the fundamental frequency interval is smaller than the maximal frequency of the frequency ramp. The approach provides a reduction of power peaks in the frequency spectrum of the mean power of fill level measuring devices, which peaks result from times in which the fill level measuring device emits a constant frequency before the beginning of or after a frequency ramp.