Near-Vertical Direction Finding Antenna Array Geolocation
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Solution Overview
Problem
Conventional radio direction finding systems are limited in their ability to rapidly and accurately geolocate radio frequency (RF) emitters, especially when they are located near or directly below an airborne platform, as they require multiple lines-of-bearing measurements and are primarily designed for 'stand-off' operations.
Innovation Solution
A Near Vertical Direction Finding (NVDF) system utilizing a two-dimensional antenna array mounted on an airborne platform, which enables instantaneous geolocation of RF emitters by obtaining simultaneous two-dimensional angular measurements and intersecting them with terrain data to determine precise location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional radio direction finding systems are used for stand-off operations, then they can operate at a distance, but they cannot rapidly and accurately geolocate RF emitters that are near or directly below the airborne platform
Solution Approach 1:
The patent transitions from conventional one-dimensional direction finding to two-dimensional angular measurement using a two-dimensional antenna array. This dimensional change enables the system to simultaneously measure both azimuth and elevation angles, providing instantaneous geolocation capability for RF emitters in any position including those directly below or near the airborne platform.
2Productivity
If conventional direction finding systems require multiple lines-of-bearing measurements, then they can achieve geolocation, but the process is time-consuming and not rapid
Solution Approach 1:
The system performs preliminary calibration to create a lookup table that stores the relationship between antenna array responses and geolocation coordinates. During operation, the system can instantly geolocate an RF emitter by querying this pre-computed table, eliminating the need for multiple time-consuming measurements and achieving rapid single-transmission geolocation.
3Adaptability or versatility
If conventional systems are designed for stand-off operations, then they work for distant targets, but they are limited in near-vertical direction finding capability
Solution Approach 1:
The patent employs a dynamic two-dimensional antenna array configuration that can adapt its measurement capability to different spatial regions. The system dynamically processes signals from multiple antennas in the array to achieve high-precision near-vertical direction finding, while maintaining the ability to operate at various distances through the calibrated lookup table approach.
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
The NVDF system achieves high accuracy in geolocating RF emitters that are off to the side, directly below, or nearly directly below the airborne platform, allowing for rapid location of RF emitters in emergency situations, such as natural disasters, with a single short transmission.
Implementation Method 1
receiving a signal from the RF emitter at each antenna of an array of N non-collinear antennas
Data Source
AI summary
A system and method for geolocating an RF emitter disposed on or near the ground includes receiving a signal from the RF emitter at each antenna of an array of N non-collinear antennas, wherein N is an integer greater than 2; routing the signal received at each of the antennas to one of a bank of N corresponding receivers; downconverting the N received signals to N downconverted signals; digitizing the N downconverted signals to digitized signals on N corresponding channels; using a processor to determine phase and amplitude variations across the N channels and to determine a Direction Vector corresponding to the signal received from the RF emitter; using a 2-dimensional pre-determined calibration table to look up a best match to the Direction Vector to determine a Bearing Vector to the RF emitter; transforming the Bearing Vector into locally level reference frame; and geolocating the RF emitter by determining an intersection between the locally level reference frame Bearing Vector and a dataset containing local terrain data.