Calibrating Signal Time-of-Flight Distance Measurement
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Solution Overview
Problem
Current signal time-of-flight-based distance measurement systems, particularly those using Bluetooth apparatuses and chips, suffer from significant fluctuations, leading to inaccuracies in distance measurements, especially in the 2.4 GHz band, which can be as high as 1.5 meters without calibration, and up to 20 meters with frequency modulation, making precise calibration challenging.
Innovation Solution
A method is introduced to calibrate signal time-of-flight measurement systems using phase-based distance measurements, where phase measurements are used to calibrate signal time-of-flight measurements, especially in Ultra Wide Band 'Time Difference of Arrival' systems, by performing phase shifts and frequency changes to determine distance, thereby reducing errors and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signal time-of-flight-based distance measurement is used, then distance measurement capability is provided, but measurement precision deteriorates with significant fluctuations up to 1.5 meters without calibration
Solution Approach 1:
The patent applies preliminary action by performing calibration measurements before actual distance measurements. The system pre-determines calibration values by comparing phase-based distance measurements (which are stable) with signal time-of-flight measurements, storing these calibration values for subsequent use to correct measurement errors.
Solution Approach 2:
The patent uses phase-based distance measurement as an intermediary to calibrate the signal time-of-flight measurement. The phase measurement serves as a reference standard with high stability, allowing the system to determine correction factors that improve the accuracy of the time-of-flight measurements without directly modifying the physical measurement process.
2Measurement precision
If calibration is performed for each apparatus individually, then measurement precision improves, but device complexity and calibration effort increase
Solution Approach 1:
The patent applies universality by enabling a single calibration value to be used across multiple apparatuses of the same model or series. The calibration process determines a common calibration factor that can be applied to all devices in a group, eliminating the need for individual calibration of each apparatus while maintaining measurement precision.
Solution Approach 2:
The patent changes the calibration approach from individual apparatus-specific calibration to model-range-specific calibration. By identifying that apparatuses of the same model or series exhibit similar measurement characteristics, the system adjusts the calibration parameter scope to reduce the number of calibration operations required while maintaining accuracy.
3Adaptability or versatility
If frequency modulation is used for time-of-flight measurement, then measurement range is improved, but measurement precision deteriorates with error contributions around 20 meters
Solution Approach 1:
The patent applies feedback by using the stable phase-based distance measurement to provide correction information back to the frequency modulation time-of-flight measurement system. The system continuously compares the two measurement methods and applies calibration factors derived from the phase measurement to correct errors in the frequency modulation measurements.
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 measurement errors, achieving an accuracy of around one meter after calibration, even across different model ranges and series, and allows for easy and automatic calibration of multiple apparatuses, enhancing the reliability of distance and position-finding measurements.
Implementation Method 1
at least one first distance measurement to the first object is carried out by means of phase measurement, particularly phase shift and/or change of a phase shift with the frequency
Implementation Method 2
Determining a distance between two objects by means of radio signals over times-of-flight of the radio signal is known
Data Source
AI summary
The invention relates to calibrating a device or a system for signal-transit-time measurement or signal-transit-time-measurement-based distance measurement on the basis of at least one phase measurement. A method for calibrating at least one system for carrying out a signal-transit-time measurement where the system is designed, in cooperation with a first object, to carry out a distance measurement on the basis of a phase measurement, at least one first distance measurement to the first object being carried out by means of phase measurement, particularly by phase shifting and/or modifying a phase shift by the frequency, and at least one signal-transit-time measurement or a second distance measurement carried out on the basis of at least one signal-transit-time measurement to or via the first object. The system is calibrated on the basis of at least one signal-transit-time measurement by means of the at least one first phase measurement.