FMCW Lidar Chirp Segmentation for Distance-Dependent Range Resolution
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Solution Overview
Problem
Conventional lidar systems in autonomous vehicles are inefficient as they require multiple sensors to achieve different range resolutions, adding complexity and expense, and existing FMCW lidar systems provide invariant resolution across their sensing range.
Innovation Solution
A lidar system employing a piecewise linear modulation scheme with a frequency-modulated chirp, allowing it to compute distances with varying resolutions based on the object's distance, using multiple linear segments with different slopes in the up-chirp and down-chirp, enabling granular resolution for close objects and coarse resolution for distant ones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple sensor systems are employed to compute distances at different resolutions, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent divides the frequency modulation waveform into multiple linear segments with different slopes. Each segment corresponds to a specific distance range and provides a specific range resolution. This segmentation allows a single sensor to achieve multiple resolution levels that would otherwise require multiple sensors.
Solution Approach 2:
The patent makes a single lidar sensor system capable of performing multiple functions by enabling it to compute distances at different resolutions across different ranges. The piecewise linear modulation scheme allows the same hardware to adaptively provide high resolution for close objects and low resolution for distant objects, eliminating the need for multiple specialized sensors.
2Measurement precision
If multiple sensor systems are employed to compute distances at different resolutions, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The frequency modulation waveform is segmented into multiple linear portions with different slopes, allowing a single sensor to provide multiple resolution levels. This eliminates the need to manufacture and integrate multiple separate sensor systems, thereby reducing manufacturing costs.
Solution Approach 2:
A single lidar sensor is designed to perform multiple resolution computations, making the system more manufacturable and cost-effective compared to deploying multiple specialized sensors for different distance ranges.
3Device complexity
If conventional FMCW lidar system uses fixed modulation scheme, then device complexity is reduced, but adaptability decreases
Solution Approach 1:
The patent introduces dynamic adaptability into the FMCW lidar system by using a piecewise linear modulation scheme where the slope changes at different segments. This allows the system to adapt its resolution characteristics based on the distance to the target, moving from a static single-resolution system to a dynamic multi-resolution system.
Solution Approach 2:
The patent changes the modulation parameter (frequency slope) across different time segments to achieve different range resolutions. By varying the slope of the frequency modulation in different linear segments, the system can optimize resolution for different distance ranges without changing the 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
Enables the lidar system to compute distances with varying resolutions depending on the object's distance, reducing the need for multiple sensors and improving efficiency and accuracy in autonomous vehicle applications.
Implementation Method 1
a frequency-modulated continuous wave (FMCW) lidar system
Implementation Method 2
the lidar system employs a coherent detection method
Implementation Method 3
a modulator that is configured to frequency-modulate radiation emitted from the laser source to cause the lidar signal to include a chirp, wherein the chirp comprises piecewise linear up-chirp
Implementation Method 4
the return reflection constructively interferes with the LO, and a sensor outputs an analog sensor signal that is indicative of such interference
Implementation Method 5
An analog-to-digital converter (ADC) converts the analog signal to a digital signal
Implementation Method 6
processing circuitry of the lidar system performs a Fast Fourier Transform (FFT) over a portion of the digital signal that corresponds to a period of the chirp, thereby forming a frequency signal that identifies one or more beat signals
Implementation Method 7
An FMCW lidar system employs a coherent detection method
Data Source
AI summary
A lidar system is described herein. The lidar system includes a transmitter that is configured to emit a frequency-modulated lidar signal. The lidar system further includes processing circuitry that is configured to compute a distance between the lidar system and an object based upon the frequency-modulated lidar signal, the processing circuitry configured to compute the distance with a first resolution when the distance is at or beneath a predefined threshold, the processing circuitry configured to compute the distance with a second resolution when the distance is above the predefined threshold, wherein the first resolution is different from the second resolution.