Lidar Pulse Receiver Circuit With Current-Mirror Dynamic Range Compression
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Solution Overview
Problem
Existing lidar sensor receiver circuits suffer from limited dynamic range, inconsistent pulse shape, and issues like spikes, undershoot, and ringing due to the use of simple transimpedance amplifiers.
Innovation Solution
A receiver circuit for lidar sensors utilizing a current mirror for photocurrent pulse multiplication, combined with nonlinear current-to-voltage conversion, achieving high input dynamic range and consistent pulse shape by transitioning through linear, square root, and logarithmic conversion regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple transimpedance amplifier with a linear feedback resistor is used in the receiver circuit, then the circuit structure is simple, but the dynamic range is limited and pulse shape becomes inconsistent with spikes and ringing
Solution Approach 1:
The receiver circuit is segmented into multiple functional blocks: a transimpedance amplifier stage for initial signal conversion, a voltage buffer for isolation, and a logarithmic amplifier stage for dynamic range compression. This segmentation allows each stage to be optimized independently, achieving high dynamic range and consistent pulse shape while maintaining reasonable overall complexity
Solution Approach 2:
A voltage buffer is introduced as an intermediary element between the transimpedance amplifier and the logarithmic amplifier. This buffer isolates the two stages, preventing loading effects and ensuring that the transimpedance amplifier operates optimally while feeding a stable signal to the logarithmic stage, thereby improving pulse shape consistency
2Power
If the photocurrent pulse amplitude increases, then the signal strength is improved, but the voltage pulse shape becomes inconsistent with spikes and undershoot
Solution Approach 1:
The circuit employs a logarithmic amplifier whose gain varies with the input signal level. For small signals, the logarithmic amplifier provides high gain to amplify weak returns. For large signals, the gain automatically compresses to prevent saturation and distortion. This dynamic parameter change maintains consistent pulse shape across the full dynamic range while preserving signal strength information
3Device complexity
If linear current-to-voltage conversion is used, then the conversion is simple, but the dynamic range is limited for both small and large photocurrent pulses
Solution Approach 1:
The current-to-voltage conversion is made dynamic through the logarithmic amplifier stage. The conversion ratio is not fixed but adapts automatically based on the input photocurrent level. This dynamic conversion extends the input dynamic range by compressing large signals and amplifying small signals, whereas a static linear converter would saturate on large signals or amplify noise on small 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
The solution provides a high dynamic range with stable voltage pulse output, immune to noise and distortion, ensuring accurate distance and position determination in lidar systems.
Implementation Method 1
An optical receiver then receives the reflected pulse of light. The optical receiver may include one or more photodetectors.
Implementation Method 2
The receiver circuit includes a current mirror providing multiplication of the photocurrent pulse generated by the photodetector.
Data Source
AI summary
A lidar sensor includes an optical transmitter configured to generate a pulse of light. The lidar sensor also includes an optical receiver configured to receive the pulse of light generated by the optical transmitter and reflected off an object in a field of view. The optical receiver includes a photodetector configured to generate a photocurrent pulse corresponding to the received pulse of light. A receiver circuit is electrically connected to the photodetector. The receiver circuit includes a current mirror providing multiplication of the photocurrent pulse provided by the photodetector. The receiver circuit is also configured to convert the photocurrent pulse to a voltage pulse and provide the voltage pulse as an output.