AC Coupling Circuit With Baseline Drift Cancellation for LiDAR
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Solution Overview
Problem
LiDAR systems experience reduced detection accuracy due to baseline drift caused by charge and discharge processes on AC coupling capacitance, leading to fluctuations in echo signals and impaired ranging and reflectivity detection.
Innovation Solution
An AC coupling circuit with an impedance matching circuit and a baseline drift reduction circuit, which includes DC blocking capacitors and cancellation circuits, is designed to block DC components and reduce baseline drift, thereby stabilizing the AC signal transmission and improving energy utilization and detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If AC coupling capacitance is used in the transmission line to transmit echo signals, then signal transmission is enabled, but baseline drift occurs due to charge and discharge processes, reducing detection accuracy
Solution Approach 1:
The AC coupling circuit is segmented into multiple functional modules: impedance matching circuit (first resistance circuit and second resistance circuit), DC blocking circuit (first DC blocking capacitor), and baseline drift reduction circuit (first cancellation circuit and second cancellation circuit). Each segment performs a specific function to collectively solve the baseline drift problem while maintaining signal transmission.
Solution Approach 2:
The first DC blocking capacitor acts as an intermediary element that blocks DC components while allowing AC signal transmission. The cancellation circuits serve as intermediary mechanisms that generate compensating signals to counteract baseline drift, effectively mediating between the signal transmission requirement and baseline stability.
2Use of energy by moving object
If impedance matching is performed using resistance circuits, then transmission efficiency is improved, but circuit complexity increases
Solution Approach 1:
The first resistance circuit and second resistance circuit serve multiple functions: they perform impedance matching to maximize power transmission efficiency, while also working in conjunction with the DC blocking capacitor and cancellation circuits to reduce baseline drift. This multi-functionality reduces the need for separate dedicated components for each function.
Solution Approach 2:
The impedance matching function is merged with the baseline drift reduction function within the same circuit architecture. The resistance circuits are integrated with the DC blocking capacitor and cancellation circuits, allowing simultaneous achievement of impedance matching and baseline stabilization without requiring entirely separate circuit paths.
3Measurement precision
If DC blocking capacitors are added to block DC components, then baseline drift is reduced, but device complexity and component count increase
Solution Approach 1:
The DC blocking capacitors are positioned in the signal path before the baseline drift occurs, performing preliminary DC component removal. The cancellation circuits are configured to anticipate and counteract baseline drift in advance, generating compensating signals that prevent drift accumulation rather than correcting it after the fact.
Solution Approach 2:
The cancellation circuits implement a feedback mechanism where the baseline drift is detected and compensating signals are generated in response to the drift condition. The first and second cancellation circuits provide feedback paths that continuously adjust to counteract baseline drift, maintaining baseline stability dynamically.
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 baseline drift, enhancing the ranging accuracy and reflectivity detection of LiDAR systems by stabilizing the AC signal transmission and minimizing signal distortion, leading to improved performance in complex environments with varying target distances and reflectivities.
Implementation Method 1
a first DC blocking capacitor, where the second terminal of the first resistance circuit is connected with the first terminal of the second resistance circuit through the first DC blocking capacitor, and the first DC blocking capacitor is configured to block the DC component in the first AC signal to form the second AC signal
Implementation Method 2
an impedance matching circuit having a signal input terminal for being accessed by the first AC signal, where the impedance matching circuit is configured to perform matching on transmission impedance of the AC coupling circuit
Implementation Method 3
the baseline drift reduction circuit uses the symmetry of a baseline drift in the AC coupling circuit to reduce the baseline drift in the AC coupling circuit
Implementation Method 4
a first cancellation circuit, where a first terminal of the first cancellation circuit is connected with the first reference node, and a second terminal of the first cancellation circuit is connected with the signal output terminal; and a second cancellation circuit, where a first terminal of the second cancellation circuit is connected with the second reference node, and a second terminal of the second cancellation circuit is connected with the signal output terminal
Data Source
AI summary
Embodiments of this application disclose an AC coupling circuit, a laser detection module, and a LiDAR. The AC coupling circuit is configured to be accessed by a first AC signal and block a DC component in the first AC signal to output a second AC signal, and the AC coupling circuit includes an impedance matching circuit and a baseline drift reduction circuit. The impedance matching circuit has a signal input terminal configured to be accessed by the first AC signal, and the impedance matching circuit is configured to perform matching on transmission impedance of the AC coupling circuit. The baseline drift reduction circuit is connected with the impedance matching circuit. The baseline drift reduction circuit uses the symmetry of a baseline drift in the AC coupling circuit to reduce the baseline drift in the AC coupling circuit.