LiDAR Waveguide Dynamic Attenuation for Clipping Prevention
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Solution Overview
Problem
FMCW LiDAR sensors are susceptible to frequency clipping due to high-power return laser beams from close objects, leading to oversaturation of photodetectors or RF amplifiers, resulting in inaccurate distance calculations.
Innovation Solution
A waveguide redirects excess energy from the return laser beam to a beam dump when the amplitude exceeds a threshold, reducing the beam's amplitude and preventing oversaturation, while also allowing the reduced beam to be used for distance calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a high-power reference laser is used to improve detection range, then the detection range is extended, but frequency clipping occurs at close distances due to oversaturation of the photodetector or RF amplifier
Solution Approach 1:
The patent implements a dynamic attenuation mechanism where the waveguide's coupling ratio is adjusted based on the detected signal amplitude. When the return laser beam amplitude is high (close object), the waveguide redirects excess energy to the beam dump, preventing oversaturation. When the amplitude is low (distant object), the waveguide allows full signal throughput. This dynamic adaptation resolves the contradiction between using high power for extended range and preventing clipping for accurate close-range measurements.
2Measurement precision
If the amplifier operates at high amplitude to detect distant objects, then detection sensitivity is improved, but the amplifier becomes oversaturated when receiving high-power return beams from close objects
Solution Approach 1:
The patent introduces a waveguide as an intermediary element between the return laser beam and the amplifier. The waveguide acts as a dynamic mediator that selectively redirects excess energy to a beam dump based on the input signal amplitude. This intermediary mechanism protects the amplifier from oversaturation while allowing it to operate at high sensitivity for detecting distant objects, thus resolving the contradiction between detection sensitivity and oversaturation prevention.
3Adaptability or versatility
If a waveguide is added to redirect excess energy, then the dynamic range is increased and clipping is prevented, but the device complexity increases
Solution Approach 1:
The patent utilizes parameter changes in the waveguide's coupling ratio as a function of the input signal amplitude. By changing the operational parameter (coupling ratio) of an existing component (waveguide) based on signal conditions, the system achieves dynamic range extension without adding complex active control mechanisms. This approach increases adaptability while minimizing the increase in device complexity compared to using active attenuators or variable gain amplifiers.
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 solution increases the dynamic range of LiDAR sensors by preventing clipping and maintaining accurate distance measurements at close distances without reducing detection range or requiring initial clipping detection.
Implementation Method 1
As the tunable coupler heats up due to the electric current, it redirects energy from the return target laser beam to a beam dump
Implementation Method 2
an accumulation wave guide or a tunable coupler that: when the electric current is received from the amplifier, reduces the amplitude of the combined laser beam
Data Source
AI summary
In one embodiment, a waveguide is added to the LiDAR sensor that redirects some of a received target return laser beam to a first stage photodetector and amplifier. When the amplitude of the target return laser beam is high enough to oversaturate the amplifier, an electric current is generated by the amplifier and received by a tunable coupler. As the tunable coupler heats up due to the electric current, it redirects energy from the return target laser beam to a beam dump. The reduced return target laser beam is then received by a photodetector or RF amplifier and is used to calculate the distance between the LiDAR sensor and object that reflected the received target return laser beam. In addition, rather than redirect the energy to a beam dump, the energy may be redirected to another photodetector or amplifier and may be used to supplement the distance calculation.