NVIS Emitter Localization Using Multi-Site Elevation Angles
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Solution Overview
Problem
Existing direction finding systems for near vertical incidence skywave (NVIS) emitters are inaccurate due to the use of weak groundwave components, leading to unreliable signal measurements.
Innovation Solution
Measure elevation angles at multiple sites, convert these angles into distances, and superimpose estimated areas to determine an area of interest encompassing the NVIS emitter's location, using a processing unit to process and combine data from multiple sites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If direction finding systems use weak groundwave components to locate NVIS emitters, then the system can operate with existing groundwave detection capabilities, but the measurement accuracy deteriorates due to very low signal levels
Solution Approach 1:
Instead of detecting weak groundwave components that travel along the ground, the patent inverts the approach by detecting skywave components that travel upward and reflect off the ionosphere. This inversion allows the system to use strong skywave signals rather than weak groundwave signals, thereby improving measurement accuracy while maintaining adaptability to NVIS emitter characteristics
Solution Approach 2:
The patent changes the detection parameter from groundwave signal strength to skywave elevation angle. By measuring the elevation angle at which skywave components arrive at the detector, the system transforms the detection approach from relying on weak ground-level signals to utilizing strong overhead signals reflected from the ionosphere, thus improving location accuracy
2Measurement precision
If multiple direction finding sites are used to improve location accuracy through triangulation, then the measurement precision improves, but the system complexity increases due to coordination and data processing requirements
Solution Approach 1:
The patent makes the direction finding system universal by enabling a single detector to function as multiple measurement points through temporal separation. The mobile detector visits different locations at different times, collecting elevation angle data that can be processed together as if from simultaneous multi-site measurements, thereby achieving triangulation accuracy without the coordination complexity of permanently distributed stations
Solution Approach 2:
The patent introduces dynamics by using a mobile detector that moves to different measurement locations rather than relying on fixed stationary detectors. This dynamic approach allows the system to gather spatially distributed data from a single reconfigurable platform, simplifying system architecture while maintaining the triangulation capability needed for accurate location determination
3Device complexity
If a single mobile direction finding station is used to reduce system complexity, then the device complexity decreases, but the measurement precision deteriorates due to inability to perform simultaneous multi-site measurements
Solution Approach 1:
The patent applies preliminary action by having the mobile detector visit and measure at multiple predetermined locations before processing the collected data. The detector gathers elevation angle measurements at various sites during separate visits, storing the data for later combined processing that achieves triangulation accuracy equivalent to simultaneous multi-site measurements, thus maintaining simplicity while improving precision
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
Accurately locates NVIS emitters by correlating elevation angles with distances, providing a precise area of interest that encompasses the emitter's location, enhancing accuracy through triangulation.
Implementation Method 1
The radio waves emitted by the near vertical incidence skywave emitters travel near vertically upwards into the atmosphere, where the respective radio waves are reflected back down
Implementation Method 2
Measuring at a first site a first elevation angle of an incoming signal issued by the near vertical incidence skywave emitter
Data Source
Figure 1~2
Figure 3~5
AI summary
A method of localizing a near vertical incidence skywave emitter (12). At a first site (A) a first elevation angle of an incoming signal issued by the near vertical incidence skywave emitter (12) is measured. At a second site (B) a second elevation angle of an incoming signal issued by the near vertical incidence skywave emitter (12) is measured, wherein the second site (B) is different to the first site (A). The first elevation angle measured and the second elevation angle measured are converted into a first length and a second length respectively, which represent the distance between the respective site (A, B) and the estimated location of the near vertical incidence skywave emitter (12). The respective length is processed, thereby generating an estimated area (24, 26) of the near vertical incidence skywave emitter (12) for each of the different sites (A, B) such that at least two different estimated areas (24, 26) are generated. The estimated areas (24, 26) for each site (A, B) are superimposed, thereby obtaining an area of interest (30) encompassing the estimated location of the near vertical incidence skywave emitter (12). Further, a direction finding system (10) is described.