FMCW LiDAR Reference Beat Signal for Long-Range Target Capture
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Solution Overview
Problem
Lidar systems face challenges in efficiently capturing targets at both short and long ranges due to limitations in integration time and signal strength, particularly when using a single modulator, which compromises the detection of long-range targets.
Innovation Solution
Implementing a dual-modulator system where a first frequency-modulated continuous-wave (FMCW) signal is transmitted directly to a Lidar scanner, while a second FMCW signal is delayed by a fixed time to serve as a reference beat frequency signal, enhancing integration time for long-range targets without compromising short-range detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single modulator is used in the Lidar system, then the device complexity is reduced, but the signal-to-noise ratio and integration time for long-range targets deteriorate
Solution Approach 1:
The patent divides the single modulator function into two separate modulators: a first modulator that processes the optical signal for scanning, and a second modulator that generates a delayed reference beat frequency signal. This segmentation allows each modulator to perform specialized functions, improving the signal-to-noise ratio for long-range targets while maintaining manageable system complexity through functional separation.
2Reliability
If integration time is increased to improve long-range target detection, then the signal level of captured targets improves, but the detection speed and productivity deteriorate
Solution Approach 1:
The patent employs periodic frequency modulation through FMCW (Frequency Modulated Continuous Wave) signals with specific sweep patterns. The first FMCW signal is modulated by the first modulator, and a delayed version is generated by the second modulator. This periodic modulation structure enables coherent integration over extended periods, improving signal level for long-range targets while maintaining detection throughput through efficient signal processing of the periodic waveforms.
3Measurement precision
If a delayed reference signal is introduced to improve long-range detection, then the measurement precision for distance improves, but the device complexity increases
Solution Approach 1:
The patent introduces a delayed reference signal as an intermediary element that mediates between the transmitted optical signal and the received echo signal. The second modulator creates this delayed version of the first FMCW signal, which then serves as a reference beat frequency signal mixed with the received signal. This intermediary reference signal enables precise distance measurement through beat frequency analysis while the modular architecture keeps the increased complexity manageable.
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 dual-modulator system improves signal-to-noise ratio and integration time for long-range targets, allowing for effective detection and navigation actions such as yielding, swerving, or turning, while maintaining robust performance for close-range objects.
Implementation Method 1
a processor that generates a first frequency modulated continuous wave (FMCW) signal and a second FMCW signal to modulate the first signal and the second signal, respectively
Implementation Method 2
the second FMCW signal comprises a reference beat signal that beats with a signal reflected from the target
Data Source
AI summary
A laser source generates an optical signal. A splitter splits the optical signal into a first signal and a second signal. A first modulator modulates the first signal. A second modulator modulates the second signal. A scanner scans the first signal following the modulation by the first modulator. A coupler combines the modulated second signal and the modulated first signal following the scanning of the first signal. A detector detect an attribute corresponding to the combined modulated second signal and the modulated first signal and captures a target based on the combined modulated second signal and the modulated first signal.