DSB-SC LiDAR Modulation for Unambiguous Velocity Direction Detection
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Solution Overview
Problem
Current Lidar technologies, such as TOF and FMCW, face limitations in detecting the velocity and direction of motion of targets, particularly at high speeds and short distances, due to interference and ambiguity in beatnote signals.
Innovation Solution
The implementation of DSB-SC modulation in coherent Lidar systems, which involves applying frequency and phase modulation to generate symmetric up-scanning and down-scanning directions, allowing for the determination of velocity and direction by analyzing frequency differences in reflected signals, and using a local oscillator shift to avoid detection ambiguity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional TOF or FMCW Lidar techniques are used, then the system can measure distance and velocity, but interference and ambiguity in beatnote signals prevent accurate detection of velocity and direction at high speeds and short distances
Solution Approach 1:
The patent applies asymmetry by intentionally creating asymmetric frequency modulation between up-scanning and down-scanning directions. By applying different frequency modulation slopes (differentiation of frequency modulation) in opposite directions, the system generates distinct beatnote frequencies for targets moving toward versus away from the Lidar, enabling unambiguous velocity and direction detection even at high speeds and short distances where conventional symmetric FMCW methods fail due to signal interference and ambiguity.
2Measurement precision
If frequency modulation is applied to generate symmetric up-scanning and down-scanning directions, then the system can detect velocity, but it cannot determine the direction of motion due to signal ambiguity
Solution Approach 1:
The patent resolves the direction detection problem by introducing asymmetric frequency modulation. The up-scanning direction applies a positive frequency modulation slope while the down-scanning direction applies a negative frequency modulation slope. This asymmetry causes the beatnote frequency to shift in opposite directions for targets moving toward versus away from the Lidar, thereby encoding direction information in the frequency shift that can be decoded without ambiguity.
Solution Approach 2:
The patent adds a new dimension to the measurement by utilizing the frequency modulation slope differentiation between up and down scanning directions. Instead of relying solely on the magnitude of frequency shift (as in conventional FMCW), the system exploits the directional dependence of the frequency modulation slope, creating an additional informational dimension that enables simultaneous determination of both velocity magnitude and direction.
3Reliability
If the carrier frequency is suppressed in DSB-SC modulation, then sideband interference is reduced, but the system requires complex frequency modulation application to maintain detection capability
Solution Approach 1:
The patent implements DSB-SC modulation by suppressing the carrier frequency component, which eliminates the strong carrier that causes interference with weak target return signals. To maintain detection capability without the carrier, the system applies differentiated frequency modulation to the sidebands, using the frequency modulation parameters (slope and direction) to encode target information. This parameter-based approach replaces carrier-dependent detection with sideband-based detection, reducing interference while maintaining functionality through careful parameter control.
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 accurate simultaneous detection of velocity and direction of targets up to 300 kilometers per hour, resolving issues of interference and ambiguity, and facilitating navigation applications such as vehicle control and obstacle avoidance.
Implementation Method 1
simultaneously determining a velocity and a direction of motion of the target with respect to the Lidar based on frequencies of a reflected signal from the target
Data Source
AI summary
Computing systems, methods, and non-transitory storage media are provided for obtaining a signal emitted from a Lidar, applying a frequency modulation to the signal to generate an up-scanning direction and a down-scanning direction of the signal, wherein the up-scanning direction and the down-scanning direction are symmetric, suppressing a carrier frequency of the signal in response to the applying of the frequency modulation, applying a frequency modulation to the carrier frequency by shifting a local oscillator to change a symmetry between the up-scanning direction and the down-scanning direction, or adding a phase modulation, directing the signal to a target, and simultaneously determining a velocity and a direction of motion of the target with respect to the Lidar based on frequencies of a reflected signal from the target in the up-scanning direction and in the down-scanning direction.