FMCW Distance Measurement Accuracy via Mixed Signal Period Optimization
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Solution Overview
Problem
FMCW distance measurement methods face limitations in measurement accuracy due to the difficulty in increasing the optical bandwidth, which affects the resolution and quality of the mixed frequency signal, making it challenging to achieve precise distance measurements.
Innovation Solution
The method involves selecting a measurement period for the mixed signal such that it has fewer than ten periods, allowing for a steeper ramp in frequency modulation, and determining the mixing frequency based on the ratio of absolute values of two measuring points, which can be used to estimate the beat frequency, even when it lies between resolved frequencies, thereby improving measurement accuracy without increasing the optical bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the optical bandwidth is increased to improve measurement accuracy, then the resolution and quality of the mixed frequency signal improve, but the implementation becomes technically difficult and complex
Solution Approach 1:
The patent changes the parameter of measurement time duration to optimize the mixed signal characteristics. By selecting a specific measurement time that results in fewer than ten periods of the mixed signal, the system achieves improved measurement accuracy without requiring increased optical bandwidth, thus avoiding the technical implementation difficulties associated with bandwidth expansion.
Solution Approach 2:
The patent applies partial action by using only the necessary portion of the frequency spectrum required for accurate measurement. Instead of increasing the full optical bandwidth, the method achieves sufficient measurement accuracy by optimizing the measurement time and utilizing the mixed signal characteristics within the existing bandwidth constraints.
2Reliability
If the measurement time is increased to improve the height of the signal peak relative to background noise, then the signal-to-noise ratio improves, but the measurement accuracy is limited by the optical bandwidth
Solution Approach 1:
The patent optimizes the measurement time parameter to achieve a balance between signal-to-noise ratio and measurement accuracy. By selecting a measurement time that produces fewer than ten periods of the mixed signal, the system achieves both sufficient signal peak height for reliable detection and maintains measurement accuracy within the existing optical bandwidth constraints.
3Measurement precision
If a steeper ramp is used to increase the frequency difference between transmitted and received signal, then the measurement accuracy improves, but the measurement time must be reduced which lowers the signal peak height
Solution Approach 1:
The patent simultaneously optimizes two parameters: the ramp steepness and the measurement time duration. By selecting a measurement time that results in fewer than ten periods of the mixed signal, the system can use a steeper ramp for improved accuracy while maintaining sufficient signal peak height through the optimized time selection, resolving the trade-off between these two parameters.
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 measurement accuracy by allowing a larger mixing frequency and robustness in determining the mixing frequency, even for intermediate frequencies, without the need for increased optical bandwidth, thus improving the reliability of distance measurements.
Implementation Method 1
at least a portion of the transmitted signal is mixed with the received signal to generate a mixed signal, wherein the mixed signal is generated based on a predetermined measuring time period
Data Source
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Figure 3A~3B
AI summary
A method for measuring distance using an FMCW distance measuring device comprises generating a frequency-modulated transmitted light beam from a transmitted signal and sending it into a measuring area, wherein the transmitted signal has a predetermined frequency deviation. The method further comprises receiving light reflected from objects in the measuring area as a received signal. The method further comprises mixing at least a portion of the transmitted signal with the received signal to generate a mixed signal, wherein the mixed signal is generated based on a predetermined measurement duration, the measurement duration being selected such that the mixed signal preferably has fewer than ten periods. The method further comprises transforming the mixed signal into a mixed-frequency signal in the frequency domain and determining a distance to the object based on a maximum of two measurement points of the mixed-frequency signal.