Phase-Encoded LiDAR Processing for Doppler Sign and Range Accuracy
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Solution Overview
Problem
Phase-encoded LIDAR systems face challenges in providing suitable target velocity resolution for autonomous vehicle applications, particularly in accurately determining the sign of Doppler velocity from real-value signals.
Innovation Solution
The implementation of a LIDAR system with a synchronous processing arrangement that correlates the phases of the Doppler frequency shift signal and the range signal, allowing for improved compensation of multiple Doppler signals and determination of the sign of Doppler velocity. Additionally, an asynchronous processing arrangement is used, where the Doppler frequency shift and time delay are measured over different coherent processing intervals, enhancing target velocity resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase-encoded LIDAR systems use conventional processing arrangements, then the system structure is simpler, but the target velocity resolution is insufficient and the signal-to-noise ratio is reduced
Solution Approach 1:
The patent segments the processing of Doppler signals by separating the determination of Doppler frequency shift and time delay into distinct processing intervals. The first coherent processing interval is used for determining Doppler frequency shift with high precision, while the second coherent processing interval is used for determining time delay. This segmentation allows each processing interval to be optimized for its specific purpose, thereby improving velocity resolution without requiring a completely complex system redesign.
Solution Approach 2:
The patent introduces a temporal dimension to the processing arrangement by using different coherent processing intervals for different measurement purposes. By measuring Doppler frequency shift and time delay over different time intervals, the system achieves enhanced velocity resolution. This dimensional approach to processing allows the system to resolve velocities more accurately by exploiting the time-domain characteristics of the signals.
2Measurement precision
If the system measures Doppler frequency shift and time delay over the same processing interval, then the processing is simpler, but the velocity resolution is degraded
Solution Approach 1:
The patent divides the measurement process into two separate coherent processing intervals: the first interval is dedicated to measuring Doppler frequency shift, and the second interval is dedicated to measuring time delay. This segmentation allows each measurement to be performed with optimized processing parameters, improving velocity resolution. Although this approach requires more total processing time, the separation of concerns enables more precise velocity determination.
Solution Approach 2:
The patent performs preliminary measurement of Doppler frequency shift in the first coherent processing interval before proceeding to measure time delay in the second interval. This preliminary action allows the system to establish the Doppler characteristics early in the processing sequence, which can then be used to inform and improve the subsequent time delay measurement, ultimately enhancing velocity resolution.
3Measurement precision
If conventional mixing of optical signals is used, then the system is easier to implement, but the signal-to-noise ratio is reduced and velocity resolution is degraded
Solution Approach 1:
The patent segments the signal processing into distinct stages: first determining Doppler frequency shift from the mixed optical signals, then using this information to guide the determination of time delay. This segmentation allows the system to extract velocity information more effectively from the mixed signals, improving the signal-to-noise ratio for velocity measurements while maintaining a practical implementation approach.
Solution Approach 2:
The patent employs feedback by using the Doppler frequency shift information obtained in the first processing interval to inform and improve the time delay measurement in the second interval. This feedback mechanism allows the system to compensate for Doppler effects on the range measurement, thereby improving the overall signal-to-noise ratio and velocity resolution without requiring fundamentally more complex hardware.
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 velocity resolution and signal-to-noise ratio in optical phase-encoded range detection, enabling more accurate range determination and improved performance in autonomous vehicle applications.
Implementation Method 1
transmitting the first optical signal toward an object... wherein the second optical signal is received in response to transmitting the first optical signal toward an object
Implementation Method 2
determine a Doppler frequency shift of the second optical signal
Implementation Method 3
receiving an electrical signal generated by mixing a first optical signal and a second optical signal
Data Source
AI summary
An autonomous vehicle control system may include one or more processors configured to receive an electrical signal generated based on a returned optical signal that is reflected from an object. The one or more processors may determine a Doppler frequency shift of the returned optical signal over a first duration of the electrical signal. The one or more processors may generate a corrected electrical signal based on the Doppler frequency shift. The one or more processors may determine a range to the object based on the corrected electrical signal over a second duration that is shorter than the first duration. The one or more processors may control at least one of a steering system or a braking system based on the range.