Doppler Null Scanning for GNSS-Free Formation Station Keeping
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Solution Overview
Problem
Mobile Ad-hoc NETworks (MANETs) face challenges due to limited network awareness in highly dynamic, low-infrastructure communication systems, where Doppler frequency shifts limit receive sensitivity and conventional station keeping systems lack sufficient integrity and accuracy for close formation flying.
Innovation Solution
A system utilizing Doppler null scanning (DNS) and two-way timing radio (TWTR) for relative positioning between nodes, enabling station keeping without relying on GNSS, and using Doppler nulling signals for determining bearing angles and time-of-flight based ranging to maintain formations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Doppler frequency shift correction is applied in conventional MANETs, then receive sensitivity is improved, but system complexity increases due to the need for continuous frequency tracking and correction mechanisms
Solution Approach 1:
The patent extracts the Doppler correction function from continuous operation and applies it only when needed - specifically when nodes enter or exit the Doppler null region during formation flight. This selective application reduces the complexity of frequency tracking systems while maintaining receive sensitivity when Doppler effects are present.
Solution Approach 2:
The system implements periodic Doppler null scanning to detect when frequency shifts occur, rather than continuous frequency tracking. By periodically scanning for Doppler null conditions and applying corrections only during these detected events, the system maintains reliability while reducing the operational complexity of frequency management.
2Measurement precision
If GNSS-based station keeping systems are used for formation flying, then positioning accuracy is improved, but vulnerability to spoofing and jamming increases
Solution Approach 1:
The patent introduces Doppler null scanning as an intermediary mechanism between nodes to establish relative positioning. Instead of relying on external GNSS signals that are vulnerable to spoofing, the system uses the Doppler effect of transmitted signals as a mediator to calculate bearing angles and ranges, creating a spoof-resistant positioning system that maintains accuracy in formation flying.
Solution Approach 2:
The system replaces the mechanical/electronic GNSS receiver system with a signal-processing-based Doppler measurement system. By substituting GNSS dependency with local Doppler null scanning and time-of-flight measurements, the system eliminates vulnerability to external spoofing and jamming while maintaining positioning precision through mathematical calculation of signal characteristics.
3Measurement precision
If wide bandwidth signals are used for high precision positioning, then measurement precision is improved, but bandwidth requirements increase system complexity and resource consumption
Solution Approach 1:
The patent changes the measurement parameter from wide bandwidth signal analysis to narrow bandwidth Doppler frequency shift measurement. By focusing on detecting the frequency shift at the Doppler null point rather than analyzing wide bandwidth signals, the system achieves high precision bearing angle and range measurements while significantly reducing bandwidth requirements and associated system complexity.
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
Enhances network integrity and accuracy in dynamic environments, allowing for precise station keeping and formation flying with low probability of interception and detection, while reducing bandwidth requirements and improving network robustness against spoofing.
Implementation Method 1
Fast-moving platforms (e.g., communications nodes moving relative to each other) experience a frequency Doppler shift (e.g., offset) due to the relative radial velocity between each set of nodes
Implementation Method 2
two-way timing radio (TWTR) for relative positioning between nodes, enabling station keeping without relying on GNSS, and using Doppler nulling signals for determining bearing angles and time-of-flight based ranging
Data Source
AI summary
A system includes a transmitter node and a receiver node. Each node of the transmitter node and the receiver node include a communications interface and a controller operatively coupled to the communications interface. The controller includes one or more processors. Each node of the transmitter node and the receiver node are in motion relative to each other and to a common reference frame. Each node of the transmitter node and the receiver node are time synchronized to apply Doppler corrections associated with said node's own motions relative to the common reference frame. The receiver node is configured to determine a bearing and a range each between the receiver node and the transmitter node. The receiver node is automatically maintained within a formation relative to the transmitter node based on the bearing and range in the station keeping mode.