FMCW LiDAR Amplitude Modulation for Simultaneous Range and Velocity
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Solution Overview
Problem
Frequency-modulated continuous-wave (FMCW) LIDAR systems face limitations in quickly obtaining target information due to the need to wait for upchirp and downchirp signals, and they can alias short-range targets, leading to disambiguation issues.
Innovation Solution
The implementation of a LIDAR system that applies amplitude modulation (AM) or time of flight (TOF) signaling to frequency-modulated (FM) signals, enabling simultaneous range and velocity measurement by processing reflection signals with active or passive modulation, and using combined FM and AM signals to distinguish between range and Doppler information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If FMCW LIDAR systems use upchirp and downchirp signals to capture target information, then measurement precision can be achieved, but the system cannot quickly obtain target information due to waiting for signal transmission and reception
Solution Approach 1:
The patent applies periodic amplitude modulation to the FMCW signal, creating distinct modulation patterns during different phases of the chirp cycle. This periodic action enables the system to extract multiple types of target information (range, velocity, etc.) from differently modulated signal portions, thereby improving data acquisition efficiency without sacrificing measurement precision
Solution Approach 2:
The patent segments the FMCW signal into different functionally-modulated portions (e.g., upchirp with AM, downchirp with AM, or different TOF signaling intervals). Each segment carries specific information types, allowing parallel processing and simultaneous extraction of multiple target parameters, thus resolving the contradiction between precision and speed
2Measurement precision
If FMCW LIDAR systems use traditional upchirp and downchirp signaling, then velocity and range can be measured, but short-range targets are aliased leading to disambiguation issues
Solution Approach 1:
The patent introduces amplitude modulation or time-of-flight signaling as an intermediary mechanism that adds a distinct temporal or amplitude signature to signals reflected from different target ranges. This intermediary encoding allows the system to disambiguate short-range targets from longer-range targets by their unique modulation patterns, eliminating aliasing issues while maintaining measurement precision
Solution Approach 2:
The patent changes the signal parameters by applying amplitude modulation or TOF signaling to the FMCW waveform. This parameter change creates distinguishable signal characteristics for different target ranges, allowing the system to reliably differentiate between short-range and long-range targets without aliasing, thus improving both measurement precision and reliability
3Measurement precision
If FMCW LIDAR systems wait for upchirp and downchirp signal completion, then accurate target information can be obtained, but the system efficiency is reduced
Solution Approach 1:
The patent applies preliminary amplitude modulation or TOF signaling to the FMCW chirp signals before transmission. This preliminary action embeds timing and range information directly into the transmitted signal structure, allowing the receiver to extract target information more quickly without waiting for complete upchirp and downchirp cycles, thereby reducing time loss while maintaining measurement accuracy
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 efficient and accurate simultaneous measurement of range and velocity, reducing aliasing issues and improving the speed of data acquisition in LIDAR systems.
Implementation Method 1
applying an amplitude modulation (AM) or time of flight (TOF) signal to a frequency modulation (FM) modulated light signal
Implementation Method 2
frequency-modulated continuous-wave (FMCW) LIDAR systems utilize upchirp (or up sweep) and downchirp (or down sweep) signals
Implementation Method 3
combined FM and AM signals to distinguish between range and Doppler information
Data Source
AI summary
A light detection and ranging (LIDAR) system has an active modulator to modulate a light signal from an optical source with a low-power mode at a section of a sweep signal to generate a pulsed light signal transmitted towards a target. The LIDAR system has a photodetector to receive a return beam from the target with an amplitude modulated (AM) signal portion and a frequency modulated (FM) signal portion. The LIDAR system determines a target range value for the target based on the AM signal portion and determines a target velocity value for the target based on the FM signal portion.