Bistatic Lidar Ranging via Transmitter State Encoding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Pulsed laser radar sensors, or lidars, face challenges in accurately determining target characteristics due to complex light scattering, imperfect detection, ambient light interference, and target motion, especially when the transmitter and receiver lack direct communication.
Innovation Solution
A bistatic lidar system that encodes a long ranging code with the transmitter's dynamical state, allowing the receiver to decode and estimate target range without direct communication, using a processor to control photon emission and a photodetector to record and decode incoming photons, enabling accurate target localization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the transmitter and receiver have no direct communication, then the system complexity is reduced, but the ability to accurately determine target characteristics deteriorates
Solution Approach 1:
The transmitter encodes its own dynamical state information (location, pointing vector, transmission time) directly into the ranging code, allowing the receiver to self-determine target characteristics without external communication assistance. The ranging code carries all necessary reference information for the receiver to calculate target range and characteristics independently.
Solution Approach 2:
The transmitter pre-encodes its dynamical state information into the ranging code before transmission. This preliminary encoding ensures that when the receiver detects the reflected light, all necessary reference information is already embedded in the signal, enabling accurate target characteristic determination without real-time communication.
2Measurement precision
If a long ranging code is used, then the range determination accuracy is improved, but the time required for complete code transmission increases
Solution Approach 1:
The long ranging code is divided into multiple sub-codes, each representing a portion of the complete code. The transmitter can transmit different sub-codes in sequence or simultaneously using different resources, allowing the receiver to process and correlate received photons with appropriate sub-codes to determine range without waiting for the entire long code to be transmitted.
Solution Approach 2:
The ranging code is transmitted periodically or in repeating sequences, allowing the receiver to accumulate photons over multiple code periods. This periodic transmission enables the receiver to achieve sufficient signal-to-noise ratio for accurate range determination faster than waiting for a single complete long code transmission.
3Loss of information
If the transmitter encodes dynamical state information into the ranging code, then the receiver can determine target characteristics without communication, but the code complexity increases
Solution Approach 1:
The transmitter's dynamical state information (location, pointing vector, transmission time) is merged with the ranging code into a single encoded signal. This combination allows the receiver to extract both the range information and the transmitter state information from the same detected signal, eliminating the need for separate communication channels while preserving all necessary information.
4Speed
If photons are emitted at high frequency, then the ranging speed is improved, but the interference from ambient light and electrical noise increases
Solution Approach 1:
The system continuously emits laser photons at high frequency, maintaining a continuous stream of useful signal photons. This continuous emission ensures that sufficient photons are always available for detection and range calculation, while the encoded nature of the signal allows the receiver to distinguish the useful photons from ambient light and noise through correlation processing.
Solution Approach 2:
The receiver uses correlation processing with the known encoded ranging code to provide feedback discrimination. By comparing the detected photon arrival times with the expected pattern from the encoded code, the receiver can identify and count only the useful signal photons while rejecting ambient light and electrical noise, enabling high-speed ranging despite interference.
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
Enables accurate target ranging and localization even in complex environments with minimal communication between the transmitter and receiver, improving range determination and reducing interference from ambient light and noise.
Implementation Method 1
Pulsed laser radar sensors, also known as lidars or ladars, are active sensing systems that determine the range to a target by measuring the time of flight of short laser pulses reflected off of the target
Implementation Method 2
The receiver includes an optical system capable of collecting light reflected from the target, and a photodetector that can record the arrival of reflected light
Implementation Method 3
Pulsed laser radar sensors, also known as lidars or ladars, are active sensing systems that determine the range to a target by measuring the time of flight of short laser pulses reflected off of the target
Data Source
AI summary
A transmitter for communication-less bistatic ranging includes a photon emitter configured to emit a plurality of photons at particular times in a pointing direction, and a processor configured to identify a particular sub-code of a plurality of sub-codes based on a dynamic state of the transmitter, each one of the plurality of sub-codes including a portion of a long optimal ranging code, generate a plurality of encoded pulse timings by dithering pulse timings from a nominal repetition frequency based on the particular sub-code, and control the photon emitter to emit the plurality of photons at the plurality of encoded pulse timings.