FMCW Lidar Simultaneous Up-Down Chirp Illumination

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Solution Overview

Problem

Existing FMCW Lidar technologies face challenges in achieving high angular resolution, strong signal to noise ratio, and simultaneous measurement of range and velocity, especially when dealing with a high quantity of pixels, due to time delays and ambiguity in processing reflected signals.

Innovation Solution

The method involves frequency modulating a laser signal in up and down-chirps, simultaneously illuminating the external scene with both chirps for at least one pixel, and amplitude modulating the laser signal of adjacent pixels to distinguish their reflected signals, allowing for fast scanning without waiting time or chirp reset.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If sequential up-chirp and down-chirp illumination is used for each pixel, then signal processing can avoid ambiguity, but time delays and waiting periods reduce scanning speed

Engineering Contradiction:

Improvesignal processing accuracyVSAvoidscanning speed

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent merges the illumination of up-chirp and down-chirp for the same pixel into a simultaneous process. The laser device illuminates the external scene with both up-chirp and down-chirp signals at the same time for each pixel, eliminating the sequential waiting period while maintaining the ability to distinguish signals through amplitude modulation coding.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent applies preliminary amplitude modulation to the laser signals before illumination. Each pixel's up-chirp and down-chirp signals are pre-coded with specific amplitude modulation patterns, allowing the calculating unit to distinguish between different pixels and chirp types without requiring sequential processing or waiting for signal separation.

Inventive Principle:

Principle #10Preliminary action

2Quantity of substance

If high pixel throughput is implemented for vast field of view, then more pixels can be processed, but time delays increase and scanning efficiency decreases

Engineering Contradiction:

Improvenumber of pixelsVSAvoidwaiting time

Core Design Contradiction:

Quantity of substanceVSLoss of time

Solution Approach 1:

The patent implements continuous illumination across all pixels simultaneously with both up-chirp and down-chirp signals. By eliminating sequential processing and waiting periods through simultaneous illumination and amplitude modulation coding, the system maintains continuous useful action across the entire pixel array, maximizing pixel throughput without time losses.

Inventive Principle:

Principle #20Continuity of useful action

3Productivity

If simultaneous up-chirp and down-chirp illumination is used for all pixels, then scanning speed increases, but signal ambiguity increases without amplitude modulation

Engineering Contradiction:

Improvescanning speedVSAvoidsignal distinction capability

Core Design Contradiction:

ProductivityVSLoss of information

Solution Approach 1:

The patent applies different amplitude modulation characteristics to different pixels and to up-chirp versus down-chirp signals. Each pixel receives a unique amplitude modulation code, and up-chirp and down-chirp signals have distinguishable amplitude modulation patterns. This local differentiation allows the calculating unit to distinguish between simultaneous signals from different pixels and different chirp types, preventing signal ambiguity while enabling simultaneous illumination.

Inventive Principle:

Principle #3Local quality

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 enables fast scanning of a single frame with high angular resolution and strong signal to noise ratio, while avoiding ambiguity in signal processing, thus improving the efficiency and accuracy of Lidar systems, especially for autonomous driving applications.

Implementation Method 1

frequency modulating with a first modulating unit a laser signal in up and down-chirps

Methodology Applied

Scientific EffectFrequency modulation: Phase Modulation

Implementation Method 2

amplitude modulating with a second modulating unit the frequency modulated laser signal of at least two adjacent pixels

Methodology Applied

Scientific EffectAmplitude modulation: Phase Modulation

Implementation Method 3

up and down beat signals can be determined due to a Doppler shift, if the relative velocity is unequal 0 m/s

Methodology Applied

Scientific EffectDoppler effect: Doppler Effect

Data Source

PatentUS12235394B2Method and system for processing laser signal taken by laser device

Publication Date: 2025.02.25 APTIV TECHNOLOGIES AG

AI summary

Described are techniques for processing a laser signal to illuminate an external scene that is sectored in pixels by a laser device. This includes frequency modulating a laser signal in up and down-chirps, illuminating the external scene, receiving a reflected laser signal, measuring an up-beat signal, measuring a down-beat signal, simultaneously illuminating the external scene with the up-chirp and with the down-chirp for at least one pixel, and amplitude modulating the modulated laser signal of at least two adjacent pixels, so that the calculating unit can distinguish the reflected laser signals of two adjacent pixels. This way, in order to allow for fast scanning of a single frame, up- and down-chirps are sent out simultaneously to scan a complete pixel row or line within one ramp without any waiting time and without any chirp reset on each pixel.