FMCW LiDAR ADC Disambiguation for Extended Range
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Solution Overview
Problem
Existing optical measurement techniques, such as LiDAR systems, face challenges with complexity, ambiguous range measurements, and increased processing time, particularly when dealing with high-resolution distance measurements that exceed the Nyquist frequency of analog-to-digital converters (ADCs), leading to aliasing issues.
Innovation Solution
The use of multiple ADCs with different Nyquist frequencies to digitize interference signals from frequency-modulated continuous-wave (FMCW) laser radar systems, allowing for the selection of the actual beat frequency and determination of object distance even in the presence of aliasing, thereby disambiguating range returns and reducing processing demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single ADC with high Nyquist frequency is used to measure high beat frequencies, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent divides the measurement task into multiple segments by using multiple ADCs with different Nyquist frequencies. Each ADC handles a specific frequency range, and the results are combined to achieve the overall measurement goal. This segmentation allows the system to measure high beat frequencies without requiring a single high-performance ADC, thereby reducing device complexity and cost while maintaining measurement precision.
Solution Approach 2:
The patent transforms the single-dimension problem of measuring high frequencies into a multi-dimensional solution by introducing multiple ADCs with different sampling characteristics. By measuring the same signal with multiple ADCs having different Nyquist frequencies and then processing the results together, the system achieves accurate measurement of high beat frequencies without requiring any single ADC to have excessively high sampling rate, thus reducing overall system complexity.
2Measurement precision
If a single ADC with high Nyquist frequency is used to measure high beat frequencies, then measurement precision is improved, but cost increases
Solution Approach 1:
The measurement function is segmented across multiple ADCs with different Nyquist frequencies. Instead of purchasing one expensive high-performance ADC, the system uses multiple lower-cost ADCs that collectively cover the required frequency range. This segmentation strategy significantly reduces the overall system cost while maintaining the ability to measure high beat frequencies with the required precision.
Solution Approach 2:
The patent employs multiple relatively inexpensive ADCs rather than a single expensive high-performance ADC. By using multiple lower-cost components that can be easily replaced or upgraded, the system achieves the same measurement capability at a lower overall cost, making the FMCW LiDAR system more economically viable for production.
3Measurement precision
If FMCW LiDAR measures extended range with high resolution, then measurement precision is improved, but processing time increases
Solution Approach 1:
The patent performs preliminary frequency disambiguation by using multiple ADCs to capture the beat frequency signal at different sampling rates before full range processing. This preliminary measurement step allows the system to quickly identify the correct frequency range and apply appropriate processing only to the relevant data, significantly reducing the overall processing time while maintaining high measurement precision for extended range detection.
Solution Approach 2:
The signal processing is segmented into multiple stages: initial frequency estimation using multiple ADCs, disambiguation of the correct frequency range, and then focused processing on the identified range. This segmentation avoids the need to process all possible frequency ranges at full resolution, thereby reducing processing time while maintaining the ability to achieve high measurement precision for extended range targets.
4Adaptability or versatility
If FMCW LiDAR measures extended range, then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent segments the frequency measurement range by using multiple ADCs with different Nyquist frequencies. Each ADC is responsible for capturing signals within its specific frequency range, and the system combines these segmented measurements to achieve extended unambiguous range. This segmentation approach allows the system to adapt to a wider measurement range without requiring a single overly complex high-speed ADC, thereby managing device complexity effectively.
Solution Approach 2:
The multi-ADC system provides universal measurement capability across multiple frequency ranges. By configuring ADCs with different Nyquist frequencies, the system can adaptively measure both short-range and long-range targets using the same hardware platform, enhancing versatility without proportionally increasing complexity. The system automatically selects and processes data from the appropriate ADC based on the detected signal characteristics.
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 extended-range, high-resolution, and lower-cost FMCW laser radar systems with faster data processing capabilities, suitable for applications like automotive LiDAR, by accurately measuring distances beyond the Nyquist frequency without compromising resolution or update rate.
Implementation Method 1
FMCW ladar uses optical heterodyne detection, which can provide quantum-noise-limited measurement signals
Implementation Method 2
a detector to combine the at least one chirped laser beam with the reflected laser beam to provide an interference signal
Implementation Method 3
a frequency-modulated continuous-wave (FMCW) laser radar system, the interference signal based in part on a laser beam reflected from an object
Data Source
AI summary
Examples are provided that use multiple analog-to-digital converters (ADCs) to disambiguate FMCW ladar range returns from one or more targets that may be greater than the Nyquist frequencies of one or more of the ADCs. Examples are also provided that use a first and a second laser FMCW return signal (e.g., reflected beam) in combination with two or more ADCs to disambiguate one or more target ranges (e.g., distances to one or more objects).