RF Signal Time of Flight Distance Measurement
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Solution Overview
Problem
Existing methods for distance measurement using radio frequency signals are inaccurate due to high signal velocity errors, environmental interference, and lack of modulation capability, especially in the 2.4 GHz band, making it difficult to determine reliable distances and locations in 2D and 3D spaces.
Innovation Solution
The method synchronizes local timers of devices to calculate time of flight for RF signals, allowing for accurate distance measurement without additional signals, and uses phase modulation and phase sequence analysis to derive arrival times, even when timers are not synchronized, and incorporates modulated carriers for secure data transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If time of flight measurement is used for distance calculation, then distance can be computed, but small offsets in time of flight result in large errors due to high signal velocity
Solution Approach 1:
The patent performs preliminary time offset calibration between transmitter and receiver clocks before actual distance measurement. This preliminary action compensates for clock synchronization errors, ensuring that subsequent time of flight measurements are accurate despite the high velocity of RF signals.
Solution Approach 2:
The patent implements a feedback mechanism where the receiver measures the time of flight and feeds back this information to the transmitter. The transmitter uses this feedback to adjust its transmission timing, creating a closed-loop system that continuously improves measurement accuracy.
2Measurement precision
If received signal strength is used for distance indication, then distance can be estimated, but accuracy is poor due to environmental interference and propagation model limitations
Solution Approach 1:
The patent replaces the indirect and environmentally-sensitive signal strength measurement method with a direct time-based measurement method. By measuring the time of flight of RF signals and multiplying by the speed of light, the system achieves accurate distance measurement that is immune to environmental factors like human bodies and metal objects.
Solution Approach 2:
The patent changes the measurement parameter from signal strength (amplitude) to time of flight (temporal characteristic). This parameter change fundamentally eliminates the problem of environmental interference affecting distance measurement, as time measurement is not influenced by RF propagation conditions.
3Measurement precision
If additional signals are transmitted for distance measurement, then time of arrival can be measured, but power consumption increases
Solution Approach 1:
The patent makes the RF signal serve multiple functions simultaneously: it carries useful data from the transmitter to the receiver, and also enables time of flight measurement for distance calculation. This multi-functionality eliminates the need for separate measurement signals, reducing power consumption while maintaining measurement accuracy.
Solution Approach 2:
The patent merges the data transmission function with the distance measurement function into a single RF signal. By embedding timing information within the data signal itself, the system achieves both communication and ranging purposes without requiring additional signal transmissions.
4Measurement precision
If unmodulated carriers or impulses are used for distance measurement, then time of arrival can be determined, but modulation cannot accompany the measurement signals
Solution Approach 1:
The patent enables the RF signal to simultaneously perform data transmission through modulation and time of flight measurement. By using modulated carriers with embedded timing information, the system achieves both communication versatility and accurate distance measurement, resolving the contradiction between these two requirements.
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 enhances the accuracy of distance measurement, reduces power consumption, and provides secure data communication by leveraging synchronized and unsynchronized timer methods, and supports modulation for efficient data transfer, suitable for IoT applications.
Implementation Method 1
The distance between two devices may be measured by the arrival time of a radio frequency (RF) signal transmitted by a device to another device
Implementation Method 2
uses phase modulation and phase sequence analysis to derive arrival times
Data Source
AI summary
Methods and devices for distance measuring/ranging, as well as location measurements both in 2D and 3D are presented. More specifically, the methods and devices are for determining the time of arrival of a radio frequency signal. A method of determining a time of arrival of a radio frequency signal in a receiving device as received from a transmitting device includes receiving a radio frequency signal, determining a first phase. The first phase is defined as a phase of the received radio frequency signal. The method also includes obtaining a second phase. The second phase is defined as a phase of a reference radio frequency signal. The method also includes determining the time of arrival of the radio frequency signal based on comparing the first and second phases.