FMCW LiDAR Chirp Segmentation for Range Resolution
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Solution Overview
Problem
Existing optical measurement techniques, such as FMCW LiDAR systems, face challenges with degraded signal strength and less frequent update rates, particularly at longer ranges, due to nonlinearities and reduced temporal overlap between local oscillator and return beams near chirp turn-around times, which limit the measurable range and resolution.
Innovation Solution
The method involves segmenting a broader bandwidth frequency chirp into multiple temporal segments with smaller bandwidths, processing each segment to determine distance, and combining results to compensate for noise and improve duty cycle, allowing for faster update rates and longer range measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a broader bandwidth frequency chirp is used to achieve high range resolution, then range resolution is improved, but chirp nonlinearities and reduced temporal overlap near turn-around times degrade signal strength and measurement reliability
Solution Approach 1:
The patent divides a broad bandwidth frequency chirp into multiple temporal segments, each with a smaller effective bandwidth. By processing each segment separately and combining results, the system achieves the range resolution of a broad bandwidth chirp while avoiding the nonlinearities and temporal overlap issues that occur in the full chirp cycle, particularly near turn-around times.
2Measurement precision
If the chirp bandwidth is increased to improve range resolution, then range resolution is improved, but the duty cycle and update rate are reduced
Solution Approach 1:
By segmenting the chirp into multiple temporal portions that can be processed independently and in parallel, the system achieves high range resolution equivalent to a broad bandwidth chirp while maintaining a higher duty cycle and update rate, as each segment can be processed more quickly than a full broad bandwidth chirp.
3Reliability
If temporal segments are processed separately with smaller bandwidths, then noise is reduced and signal strength is improved, but the effective bandwidth is reduced
Solution Approach 1:
The patent combines the distance measurement results from multiple temporal segments processed with smaller bandwidths. By merging these results through averaging or other combination techniques, the system achieves the signal strength benefits of narrow bandwidth processing while recovering the effective broad bandwidth range resolution through the combined information from all segments.
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 duty cycle and range resolution of FMCW ladar systems, enabling more robust and accurate distance measurements at longer ranges with higher update rates, overcoming limitations of chirp nonlinearities and reduced temporal overlap.
Implementation Method 1
FMCW ladar uses optical heterodyne detection, which can provide quantum-noise-limited measurement signals
Implementation Method 2
producing an interference signal from a frequency-modulated continuous wave (FMCW) laser radar system
Implementation Method 3
The processor may be configured to determine a distance to at least a portion of an object based on an optical beat frequency of the interference signal
Data Source
AI summary
Examples of FMCW laser radar systems and methods described herein may segment the processing of a broader bandwidth frequency chirp into multiple shorter-duration (e.g., lower bandwidth) frequency chirps. This segmentation may have the benefits in some examples of improving the measurement duty cycle and range resolution, and/or allowing for more flexible processing, and/or enabling improved detection of more distant objects.