FMCW Radar Phase Analysis for Distance Drift Compensation
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Solution Overview
Problem
Conventional FMCW radar systems face challenges in accurately measuring small changes in distance due to frequency drift caused by aging components and temperature fluctuations, leading to instability in the transmission signal frequency, which results in relatively large relative errors in distance measurement, especially for slow changes in distance.
Innovation Solution
The method involves evaluating the phase of the mixed signal formed by the FMCW radar, separating it into time-dependent and time-independent components, and accounting for the frequency drift of the transmission signal to determine changes in distance with high precision, using a frequency analysis that considers the transit time and center frequency of the signals, thereby correcting for measurement errors caused by frequency deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If frequency-modulated continuous wave radar is used for distance measurement, then transmission power requirements are reduced and signal-to-noise ratio is improved, but distance measurement accuracy deteriorates due to frequency drift from component aging and temperature fluctuations
Solution Approach 1:
The patent implements a feedback mechanism by continuously monitoring the actual center frequency of the transmission signal and using this information to correct distance measurements. The system measures the frequency drift and compensates for its effect on the time-of-flight calculation, thereby maintaining measurement accuracy despite frequency variations over time and temperature changes
Solution Approach 2:
The patent changes the approach from assuming a fixed center frequency to dynamically tracking and adjusting for frequency drift. By treating the center frequency as a variable parameter that changes over time due to aging and temperature, the system adapts its measurement calculations to maintain accuracy while continuing to use low-power FMCW operation
2Reliability
If conventional FMCW radar measures distance based on frequency difference, then continuous transmission enables good signal-to-noise ratio, but small changes in distance cannot be measured accurately due to frequency drift
Solution Approach 1:
The system continuously monitors the actual center frequency during operation and feeds this information back into the distance calculation algorithm. This feedback loop allows the system to distinguish between frequency shifts caused by component drift and those caused by actual target movement, enabling accurate detection of small distance changes even in continuous wave operation
Solution Approach 2:
The patent replaces the conventional frequency-difference-based measurement method with a time-of-flight measurement approach that uses phase information. By substituting the frequency-difference mechanism with a phase-based time measurement that is corrected for frequency drift, the system achieves both continuous transmission benefits and accurate small displacement detection
3Device complexity
If the transmission signal frequency is allowed to drift due to component aging and temperature, then device complexity is reduced and operation is simpler, but relative error in distance measurement increases
Solution Approach 1:
The system performs self-characterization by automatically measuring its own frequency drift during normal operation and using this self-measured information to correct its measurements. This self-service approach eliminates the need for external frequency stabilization systems or calibration equipment, maintaining simplicity while improving accuracy
Solution Approach 2:
The patent substitutes complex frequency stabilization hardware with a software-based frequency tracking and compensation system. By replacing mechanical/physical frequency control mechanisms with digital signal processing and calculation corrections, the system maintains operational simplicity while achieving accurate measurements despite frequency drift
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 high-precision measurement of small changes in distance, such as 0.1 mm/h at 1000 m, with minimal equipment and energy requirements, and can detect changes of 0.01 mm/h by accounting for ambient air parameters like humidity and temperature, providing accurate distance measurements even in poorly accessible areas.
Implementation Method 1
a transmitting and a receiving unit (2, 3), wherein the transmitting unit (2) emits frequency-modulated, continuous electromagnetic microwaves as a transmission signal (4)
Implementation Method 2
the transmission signal (4) is reflected by the object to be measured (5), wherein an echo signal (5) reflected by the object to be measured is received
Implementation Method 3
the transmission signal (4) is mixed with the echo signal (5) in a mixer (6) to generate a mixed signal (6)
Implementation Method 4
the distance between the radar device and the object to be measured is determined from the temporal change in the phase of the mixed signal generated in this way
Data Source
Figure 1
Figure 2a~2d
Figure 3
AI summary
The invention relates to a device and a method for measuring a change in distance between a stationary initial point and an object, wherein frequency-modulated, continuous electromagnetic microwaves are emitted as an emitting signal (4) in the direction of the object such that the emitting signal (4) is reflected by the object and an echo signal (5) that is generated at the object following the reflection of the emitting signal (4) is received and evaluated. The method according to the invention or the FMCW radar apparatus designed according to the invention is based on a hardware extension of a standard FMCW radar apparatus and offers the possibility of evaluating a time-independent part of the mixed signal phase (6) by means of an evaluation electronics (18) while taking into account a propagation time of the emitting (4) and/or echo signal (5) between emitting unit (2) and object so that a change in distance between emitting unit (2) and object can be detected as a result of a change in propagation time.