FMCW LiDAR Frequency-Sweeping Method for High Resolution
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Solution Overview
Problem
Conventional FMCW LiDAR systems face challenges in achieving high distance resolution due to the inverse proportionality of distance resolution to frequency-modulation bandwidth, requiring large frequency-modulation bandwidths that are difficult to generate, and have limitations in measurement point density and system complexity.
Innovation Solution
The FMCW frequency-sweeping method involves generating a frequency-sweeping light beam with multiple continuous chirps within preset measurement periods, splitting it into transmitted and local-oscillation beams, and detecting the beat frequency to determine distance and speed, with each chirp having a frequency-ascending and descending stage, and recombining frequency-mixing signals to increase measurement point density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If large frequency-modulation bandwidth is used to improve distance resolution, then distance resolution is improved, but system complexity and difficulty of generating the signal increase
Solution Approach 1:
The patent divides the frequency-modulation bandwidth into multiple smaller chirps within a single measurement period. Each chirp has a smaller bandwidth (fs = fBw/N), but by combining N chirps, the system achieves the equivalent resolution of using the full bandwidth. This segmentation reduces the complexity of generating each individual chirp while maintaining the overall measurement precision through signal combination.
Solution Approach 2:
The patent employs periodic frequency-sweeping measurement periods where multiple chirps are sequentially transmitted and received. By using periodic action with multiple smaller chirps instead of one large bandwidth signal, the system achieves the same distance resolution while reducing the instantaneous bandwidth requirement and associated system complexity.
2Measurement precision
If large frequency-modulation bandwidth is used to improve distance resolution, then distance resolution is improved, but signal generation difficulty increases
Solution Approach 1:
The patent segments the large frequency-modulation bandwidth into multiple smaller chirps. Each chirp has a bandwidth of fs = fBw/N, which is easier to generate using standard laser modulation techniques. The signal generation difficulty is reduced for each individual chirp, and the overall resolution is maintained by combining the information from all N chirps.
3Productivity
If multiple chirps are used to increase measurement point density, then measurement point density is improved, but processing complexity increases
Solution Approach 1:
The patent merges the frequency-mixing signals from multiple chirps to create a recombined signal that represents the complete frequency-sweeping measurement period. By combining the signals from N chirps, the system achieves higher measurement point density while the processing complexity is managed through systematic combination of the individual chirp signals.
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 improves the measurement point density and resolution of the FMCW LiDAR system while reducing system complexity and power consumption by using smaller frequency-sweeping bandwidths, making it more feasible and cost-effective.
Implementation Method 1
each of the N chirps includes one frequency-ascending stage having a preset frequency-ascending slope and one frequency-descending stage having a preset frequency-descending slope
Implementation Method 2
a reflected light beam is generated after the transmitted light beam encounters an obstacle
Implementation Method 3
detecting a beat frequency between the local-oscillation light beam and the reflected light beam to determine a distance and/or a speed of the obstacle
Data Source
AI summary
A FMCW frequency-sweeping method and a FMCW LiDAR system. The method includes: obtaining a frequency-sweeping light beam, wherein the frequency-sweeping light beam periodically implements N continuous chirps within a plurality of preset frequency-sweeping measurement periods, N is a positive integer, and N≥2, each chirp includes one frequency-ascending stage having a preset frequency-ascending slope and one frequency-descending stage having a preset frequency-descending slope (S201), and a frequency-sweeping bandwidth of each chirp and a preset frequency-sweeping total bandwidth satisfy following relationship: fs=fBw/N, few is the preset frequency-sweeping total bandwidth, fs is the frequency-sweeping bandwidth, a duration of each frequency-ascending stage or each frequency-descending stage and the preset frequency-sweeping measurement period satisfy the following relationship: Ts=T0/2N, wherein T0 is the preset frequency-sweeping measurement period, and Ts is the duration of each frequency-ascending stage or each frequency-descending stage.