Diversity Polarization Modulation for GNSS Anti-Jamming
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Solution Overview
Problem
Global Navigation Satellite Systems (GNSS) face challenges in robustness against multipath interference, jamming, and spoofing, with existing anti-jamming techniques assuming specific polarizations and jammer locations that are not always true, necessitating the development of new techniques to enhance signal transmission and reception resilience.
Innovation Solution
The method involves transmitting and receiving navigation codes using diversity polarization modulation, including polarization hopping and simultaneous dual polarization code transmission, which alternates between right-hand and left-hand circular polarizations to confuse jammers and identify spoofing signals, while being compatible with existing systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional single-polarization navigation signals are transmitted, then the system is simple to implement, but the system is highly susceptible to jamming and spoofing attacks
Solution Approach 1:
The patent implements dynamic polarization switching where the navigation signal alternates between right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) in time-division multiplexed fashion. This dynamic change in polarization state confuses jammers that are tuned to a specific polarization, as the signal characteristics continuously vary, thereby improving anti-jamming reliability without requiring complex spatial diversity structures
Solution Approach 2:
The patent introduces polarization dimension to the traditional single-dimension navigation signal transmission. By encoding navigation data in both RHCP and LHCP dimensions and switching between them, the system creates an additional degree of freedom for signal transmission and jammer discrimination, improving reliability while maintaining manageable system complexity through structured polarization time-division multiplexing
2Reliability
If polarization hopping is implemented to confuse jammers, then anti-jamming performance improves, but signal processing complexity increases
Solution Approach 1:
The patent employs periodic polarization hopping where the navigation signal systematically switches between RHCP and LHCP at predetermined time intervals. This periodic structure allows receivers to anticipate and track polarization changes using known patterns, reducing signal processing complexity compared to random polarization switching while maintaining effective jammer confusion through regular polarization state changes
Solution Approach 2:
The patent incorporates preliminary synchronization information in the navigation signal that enables receivers to pre-establish knowledge of the polarization hopping pattern. This preliminary action allows the receiver to prepare for upcoming polarization transitions, reducing the real-time signal processing complexity while maintaining the anti-jamming benefits of polarization hopping
3Reliability
If dual polarization codes are transmitted simultaneously, then signal robustness against spoofing improves, but transmission bandwidth requirements increase
Solution Approach 1:
The patent segments the navigation signal transmission into distinct time intervals, with each segment transmitted in a specific polarization state (RHCP or LHCP). Different navigation data or code phases are assigned to different polarization segments, allowing spoofing detection through polarization diversity while using time-division multiplexing to avoid requiring doubled bandwidth that would result from simultaneous dual-polarization transmission
4Reliability
If existing anti-jamming techniques assuming specific jammer polarizations are used, then implementation is straightforward, but effectiveness is limited when assumptions are incorrect
Solution Approach 1:
The patent implements a universal polarization time-division multiplexing scheme that is effective against multiple types of jammers regardless of their polarization characteristics. By switching between RHCP and LHCP, the system simultaneously provides protection against linearly polarized jammers, circularly polarized jammers, and jammers with unknown polarization states, achieving broad adaptability without requiring separate specialized anti-jamming systems for different jammer types
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 improves signal-to-noise ratio, effectively eliminates jamming signals, and identifies spoofing, achieving an anti-jamming improvement of up to 17 dB and maintaining compatibility with legacy systems.
Implementation Method 1
transmitting a first portion of the information using electromagnetic waves with a first polarization in response to a first value of the digital code, and transmitting a second portion of the information using electromagnetic waves of a second polarization
Implementation Method 2
receiving and decoding the electromagnetic waves, the method comprising: receiving, at the receiver from a transmitter, a digital code... receiving, at the receiver, first electromagnetic waves. The first electromagnetic waves are decoded corresponding to a first polarization... Second electromagnetic waves are received at the receiver, and the second electromagnetic waves are decoded corresponding to a second polarization
Data Source
AI summary
A method includes transmitting a digital code from a transmitter to a receiver. Information is transmitted via electromagnetic waves from the transmitter to the receiver. The transmission of the information includes transmitting a first portion of the information using electromagnetic waves with a first polarization in response to a first value of the digital code, and transmitting a second portion of the information using electromagnetic waves of a second polarization in response to a second value of the digital code. The first information may include a first navigational code and the second information may include a second navigational code.