FMCW LiDAR Amplitude Modulation for Distant Object Detection
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Solution Overview
Problem
FMCW LiDAR systems struggle to accurately detect distant objects due to significant amplitude loss in scattered beams, affecting the comprehensive representation of vehicle surroundings and overall safety.
Innovation Solution
The FMCW LiDAR system modulates the amplitude of the scattered signal based on the distance from the object, amplifying it as a function of distance to enhance detection of distant objects, using a threshold ranging distance to determine the amplitude modulation period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If FMCW LiDAR systems use standard detection methods, then the system structure remains simple, but the detection capability for distant objects deteriorates due to significant amplitude loss
Solution Approach 1:
The patent applies preliminary action by modulating the amplitude of the transmitted FMCW signal in advance based on the distance to the target object. The amplitude modulation is performed before the signal reaches the distant object, ensuring that even after significant propagation loss, the reflected signal maintains sufficient amplitude for accurate detection. This pre-compensation approach resolves the contradiction by improving distant object detection capability without requiring complex post-detection processing or additional hardware components.
2Length of stationary object
If the LiDAR system increases transmission power to detect distant objects, then the detection range improves, but the eye safety standards are violated
Solution Approach 1:
The patent applies parameter changes by modifying the amplitude parameter of the transmitted FMCW signal dynamically. Instead of using high constant power, the system varies the amplitude of the transmitted signal based on the distance to the target. For distant objects, the amplitude is increased proportionally to compensate for propagation loss, while for closer objects, the amplitude is reduced. This allows the system to extend detection range while maintaining eye safety standards by ensuring the peak power remains within safe limits.
3Measurement precision
If the LiDAR system uses amplitude modulation to compensate for distance, then the detection accuracy for distant objects improves, but the signal processing complexity increases
Solution Approach 1:
The patent applies feedback by using the distance information obtained from Time of Flight calculations to adjust the amplitude modulation of the transmitted signal. The system measures the distance to the target, uses this information to determine the appropriate amplitude compensation factor, and applies this factor to subsequent transmissions. This closed-loop approach improves detection accuracy for distant objects while keeping signal processing manageable, as the feedback mechanism uses straightforward distance-based amplitude adjustment rather than complex signal processing algorithms.
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 allows for a more comprehensive and accurate 3D representation of the vehicle's surroundings, improving detection range and safety by registering distant objects effectively.
Implementation Method 1
a frequency modulator configured to modulate a frequency of the continuous wave, thereby producing a Frequency-Modulated-Continuous-Wave (FMCW) signal
Implementation Method 2
an amplitude modulator configured to modulate an amplitude of the FMCW signal, thereby producing an Amplitude-Frequency-Modulated-Continuous-Wave (AFMCW) signal
Implementation Method 3
the first AFMCW signal to be outputted by the LiDAR system for reflecting off the object, thereby producing a reflected signal
Implementation Method 4
The position and distance of the object can be computed using Time of Flight calculations of the emitted and detected light beam
Implementation Method 5
a detector configured to amplify the reflected signal based on the second AFMCW signal by increasing amplification of the reflected signal as a function of a distance of the object from the LiDAR system
Implementation Method 6
The position and distance of the object can be computed using Time of Flight calculations of the emitted and detected light beam
Implementation Method 7
by superimposing the scattered FMCW signal with the initial one (i.e., the one that initially has been produced by the local oscillator), based on a Doppler effect, a current velocity of the surrounding object relative to the LiDAR system may be yielded
Data Source
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AI summary
A LiDAR system and a method for operation thereof are provided. The LiDAR system comprises: a frequency-modulated continuous wave (FMCW) light source configured to produce an FMCW signal; and an amplitude modulator configured to modulate an amplitude of at least a portion of the FMCW signal, thereby producing an Amplitude-Frequency-Modulated-Continuous-Wave (AFMCW) signal; a splitter configured to split one of the FMCW signal and the AFMCW signal into a first portion and a second portion, the first portion being an output signal for reflecting off the object, thereby producing a reflected signal, and the second portion being a reference signal for amplifying the reflected signal; and a detector configured to amplify the reflected signal based on the reference signal as a function of a distance from the LiDAR system to an object, thereby generating an amplified reflected signal for determining the distance to the object.