Analog Demodulation of PMCW LiDAR Signals
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Solution Overview
Problem
Existing PMCW LiDAR systems require high-speed digitalization and complex digital processing, leading to increased circuit complexity, power consumption, and cost, while also losing frequency spectra due to upstream digitization.
Innovation Solution
Analog processing circuitry is used to perform doppler component extraction and encoding correlation before digitalization, allowing for reduced ADC speeds and enhanced processing speed, resolution, and bandwidth, with the option to feed results into digital processing for further analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-speed digitalization is used to process PMCW LiDAR signals, then measurement precision is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent extracts and performs specific signal processing functions (doppler component extraction and encoding correlation) in the analog domain before digitalization. This separates the critical frequency analysis from the digitization process, allowing high precision range measurement while avoiding the need for complex high-speed digital processing circuits.
Solution Approach 2:
The patent replaces digital signal processing operations with analog circuit implementations. The analog processing circuit performs multiplication, integration, and correlation operations that would otherwise require complex digital processors, thereby reducing device complexity while maintaining measurement precision.
2Measurement precision
If high-speed digitalization is used to process PMCW LiDAR signals, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent extracts critical signal processing functions from the digital domain and implements them in analog circuits. This reduces the burden on high-power ADCs and digital processors, thereby lowering overall power consumption while preserving the precision needed for accurate range information extraction.
Solution Approach 2:
The patent substitutes power-intensive digital processing operations with lower-power analog circuit operations. The analog processing circuit performs signal correlation and doppler extraction using continuous voltage operations rather than high-speed digital computation, significantly reducing power consumption.
3Productivity
If upstream digitization is performed, then processing capability is improved, but frequency spectra are lost
Solution Approach 1:
The patent performs frequency spectrum analysis and doppler component extraction before the digitization process. By conducting these operations in the analog domain while the signal still contains complete frequency information, the system preserves the full spectrum for accurate processing before conversion to digital form.
Solution Approach 2:
The patent introduces an analog processing circuit as an intermediary between the optical signal and the ADC. This intermediary performs necessary signal processing operations on the analog signal, extracting doppler and range information before digitization, thereby preventing loss of frequency spectral information that would occur with direct digitization.
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 reduces ADC speeds from hundreds of MHz to tens of MHz, enhances processing speed and resolution, and decreases circuit complexity and power consumption, while maintaining accurate range information extraction.
Implementation Method 1
a local oscillator generating a reference signal at a frequency close to the carrier frequency
Implementation Method 2
analog extraction of a doppler component
Data Source
AI summary
Method and apparatus for generating and processing pulses in a light detection and ranging (LiDAR) system. In some embodiments, an emitter outputs phase modulated continuous wave (PMCW) light sequences encoded with a selected encoding scheme such as a pseudo-random bit sequence (PRBS). An analog processing circuit processes reflected light sequences from a target illuminated by the PMCW light sequences by performing analog extraction of a doppler component and analog encoding correlation prior to digitalization of the received signal. The analog processing circuit can include a plurality of demodulation stages each multiplying the input signals by positive and negative magnitudes of a scalar value at times corresponding to signal transitions of different associated doppler clock frequencies. A threshold circuit applies suitable thresholding, after which the signals can be digitized by an analog-to-digital converter (ADC) for further processing in the digital domain to obtain range information associated with the detected target.