FMCW LiDAR Beat Signal Processing for Lower ADC Sampling
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Solution Overview
Problem
The high sampling rates required by Analog-to-Digital Converters (ADCs) in LIDAR systems make commercialization impractical and expensive due to the high demands of LIDAR applications.
Innovation Solution
A LIDAR system that reduces the effects of radial velocity and distance between the LIDAR chip and reflecting objects by generating LIDAR data in series of cycles, where each cycle corresponds to a different region in the field of view, and uses electronics to generate LIDAR output signals with frequency shifts that minimize the contribution of radial velocity to the frequency shift, allowing for reduced ADC sampling rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high sampling rates are used by ADCs in LIDAR systems, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent changes the operational parameters of the LIDAR system by using frequency-modulated continuous wave (FM-CW) modulation and phase-shift keying (PSK) to encode distance and velocity information. This allows the system to achieve precise measurements without requiring high sampling rates, as the information is embedded in the frequency and phase characteristics of the modulated signal rather than requiring high-rate analog-to-digital conversion
Solution Approach 2:
The patent replaces the traditional high-rate sampling approach with a signal processing approach that uses frequency modulation and phase detection. Instead of relying on high-speed ADCs to capture rapid signal changes, the system uses the frequency shift and phase information from the modulated signal to extract distance and velocity data, substituting a mechanical/electronic sampling system with an optical/signal-processing-based system
2Measurement precision
If high sampling rates are used by ADCs in LIDAR systems, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent changes the sampling rate parameter from high to low by using frequency-modulated continuous wave (FM-CW) modulation. The system encodes distance information in the frequency shift of the modulated signal, allowing standard ADCs to capture the signal at much lower rates while still achieving precise distance measurements through frequency analysis rather than high-rate time-domain sampling
Solution Approach 2:
The patent employs standard, off-the-shelf electronic components and signal processing techniques that can be implemented with conventional hardware. By avoiding the need for expensive high-speed ADCs and specialized high-rate sampling electronics, the system can be manufactured using standard manufacturing processes and cost-effective components, making the LIDAR system more suitable for commercialization
3Device complexity
If frequency shift is minimized in LIDAR output signal, then radial velocity contribution to frequency shift is reduced, but measurement precision may be affected
Solution Approach 1:
The patent uses feedback from the received signal to determine both distance and radial velocity. By analyzing the frequency shift and phase information from the modulated signal that returns to the LIDAR system, the electronics can simultaneously extract both parameters. The feedback mechanism allows the system to compensate for any frequency shifts and maintain measurement precision while using practical sampling rates
Solution Approach 2:
The patent moves the measurement from a single-dimensional high-rate time-domain sampling approach to a multi-dimensional frequency and phase domain analysis. By modulating the signal in frequency and phase and analyzing these dimensions in the received signal, the system can extract both distance and velocity information without relying on high sampling rates, effectively adding dimensional complexity to the measurement process
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
The solution effectively reduces the required sampling rate to practical and affordable levels by minimizing the frequency shift contribution from radial velocity and distance, enabling cost-effective implementation of LIDAR systems.
Implementation Method 1
The LIDAR chip is configured to combine the LIDAR input signal with a reference signal so as to produce a beating signal
Implementation Method 2
the LIDAR input signal has a frequency shift relative to a frequency of the LIDAR output signal but a contribution of the relative motion to the frequency shift is less than 10% of the Doppler shift from two objects moving at the same radial velocity
Data Source
AI summary
A LIDAR system includes a LIDAR chip that is configured to output a LIDAR output signal such that the LIDAR output signal can be reflected by an object located off the LIDAR chip. The LIDAR chip is also configured to receive a LIDAR input signal that includes light from the reflected LIDAR output signal. The LIDAR chip is configured to combine the LIDAR input signal with a reference signal so as to produce a beating signal. The electronics operate the LIDAR chip such that the effects of radial velocity between the reflecting object are reduced or removed from the beating signal while measuring the distance between the LIDAR chip and the reflecting object. The electronics operate the LIDAR chip such that the effects of the distance between the reflecting object are reduced or removed from the beating signal while measuring the radial velocity between the LIDAR chip and the reflecting object.