Phase-Encoded LiDAR Processing for Doppler Sign and Range SNR
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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-valued 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, and an asynchronous processing arrangement where the Doppler frequency shift and time delay are measured over different coherent processing intervals, enhancing velocity resolution and signal-to-noise ratio.
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 poor
Solution Approach 1:
The patent segments the processing of Doppler frequency shift and range signal into separate coherent processing intervals. The Doppler frequency shift is measured over a first coherent processing interval while the range signal is measured over a second coherent processing interval, allowing independent optimization of each measurement without requiring complex simultaneous processing of both signals
Solution Approach 2:
The patent transitions from conventional single-interval processing to a two-dimensional processing approach by measuring Doppler frequency shift and range signal over different coherent processing intervals. This dimensional separation in the time-frequency domain enables enhanced velocity resolution and signal to noise ratio without proportionally increasing system complexity
2Measurement precision
If real-valued signals are used for Doppler measurement, then the signal processing is simpler, but the sign of Doppler velocity cannot be accurately determined
Solution Approach 1:
The patent introduces complex-valued signal processing as an intermediary step between signal reception and velocity determination. By using complex-valued signals during the coherent processing interval, the system can accurately determine the sign of Doppler velocity through phase information, while still providing real-valued velocity output for practical applications
Solution Approach 2:
The patent changes the mathematical representation of the signal from real-valued to complex-valued during processing. This parameter change enables the extraction of phase information necessary for accurate Doppler velocity sign determination, while the final velocity output remains in the practical real-valued domain
3Measurement precision
If synchronous processing arrangement is used, then the processing is more efficient, but range signal noise due to inconsistent phases cannot be eliminated
Solution Approach 1:
The patent segments the coherent processing interval into separate measurement periods for Doppler frequency shift and range signal. This segmentation allows the range signal to be processed during intervals optimized for range measurement, eliminating noise from inconsistent phases while maintaining overall processing efficiency through structured time division
Solution Approach 2:
The patent implements periodic measurement cycles where Doppler frequency shift and range signal are measured alternately over different coherent processing intervals. This periodic action pattern enables consistent phase relationships during range signal measurement while maintaining efficient overall system operation through regular, structured processing cycles
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 improves target velocity resolution, eliminates range signal noise due to inconsistent phases, and accurately determines the sign of Doppler velocity, addressing the limitations of existing phase-encoded LIDAR systems for autonomous vehicle applications.
Implementation Method 1
transmitting the first optical signal toward an object... 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.