Direction Finding Using Virtual Antenna Array Aperture
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Solution Overview
Problem
Direction finding systems using interferometry face challenges with ambiguity resolution and accuracy due to long baselines, which require many antennas and are costly, especially when implemented on airborne vehicles where space is limited.
Innovation Solution
A method using a platform with at least two antennas separated by a known distance, where the position of one antenna is changed based on the platform's orientation to create a virtual antenna array aperture, allowing direction determination by correlating phase relations and position changes to resolve ambiguities with fewer antennas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the interferometer baseline length is increased to improve direction measurement accuracy, then measurement precision improves, but the number of ambiguities increases and device complexity increases
Solution Approach 1:
The patent applies dynamics by making the antenna array configuration changeable over time. The system transitions from a static antenna array to a dynamic configuration where antennas are moved to different positions during measurement. This allows the system to achieve the directional accuracy of a long baseline while using fewer physical antennas, as the same antennas can occupy multiple positions sequentially rather than requiring all positions to be simultaneously occupied.
Solution Approach 2:
The patent introduces the time dimension to the antenna array configuration. Instead of only spatial arrangement, the system utilizes temporal variation by moving antennas between different positions. This transforms a purely spatial problem into a space-time problem, allowing the system to synthesize a large virtual aperture through sequential positioning rather than requiring a large physical aperture with many simultaneous antenna elements.
2Measurement precision
If the interferometer baseline length is increased to improve direction measurement accuracy, then measurement precision improves, but robust phase or ambiguity resolution becomes more difficult
Solution Approach 1:
The patent applies preliminary action by pre-planning and pre-positioning the antenna array in specific configurations before measurements are taken. The system uses a controlled sequence of antenna positions that are predetermined to optimize both accuracy and ambiguity resolution. By carefully selecting and preparing the measurement configurations in advance, the system ensures that phase ambiguity can be resolved more easily while still achieving high directional accuracy.
3Measurement precision
If many antennas and DF receivers are used to achieve accurate direction finding, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The patent merges the functions of multiple antenna elements into fewer physical antennas by utilizing temporal multiplexing. Instead of requiring many antennas to operate simultaneously to achieve a large aperture, the system combines the measurements from fewer antennas taken at different positions and times. This consolidation reduces the total number of antenna elements and receivers needed while maintaining the directional finding accuracy that would otherwise require a much larger simultaneous array.
4Measurement precision
If a long baseline interferometer is used on an airborne vehicle to improve direction measurement accuracy, then measurement precision improves, but ease of operation deteriorates due to space constraints
Solution Approach 1:
The patent creates a virtual copy of a large baseline interferometer configuration using fewer physical antennas. Instead of physically installing a long baseline array that would require significant space on an airborne vehicle, the system uses electronic processing and sequential positioning to replicate the measurement capabilities of a long baseline system. This virtualization allows the airborne platform to achieve high directional accuracy without the space requirements of a physical long baseline array.
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 enables accurate direction finding with fewer antennas, forming a large virtual antenna array aperture, reducing ambiguities and costs, while allowing airborne vehicles to determine signal-emitting object directions with high precision.
Implementation Method 1
Phase interferometry techniques in their simplest form utilize a pair of antennas disposed on a moving platform spaced apart by a known distance such that a plane wave arriving at an angle relative to the pair is received by one antenna at an earlier point in time than the other, due to the difference in path length traversed by the wave. If the signals from the two antennas are processed, their phase difference provides an indirect measurement of a direction to a signal-emitting object relative to the antenna pair.
Data Source
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AI summary
The present invention relates to a method for determining a direction to a signal-emitting object by means of a platform comprising at least two antennas separated by a known distance. The method comprises said steps of: receiving, with each of said at least two antennas, a signal from said signal-emitting object at first positions, determining a first phase relation of said signal between said at least two antennas, - receiving, with each of said at least two antennas, a signal from said signal-emitting object at at least second positions, determining at least a second phase relation of said signal between said at least two antennas, characterised by the steps of: determining change(s) in position(s) of at least one antenna of said at least two antennas, and determining a direction to a signal-emitting object based on said first phase relation, said at least second phase relation and said change(s) in position(s) of said at least one antenna. The invention further relates to a platform performing a determination of a direction to a signal-emitting object.