Elevation Angle Positioning Using AoA-ToA Switching
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Solution Overview
Problem
Existing positioning systems using array antennas for measuring radio wave angles of arrival (AoA) experience increased phase difference errors when the elevation angle is large, leading to inaccuracies in determining the elevation angle.
Innovation Solution
A positioning system that includes an altitude measurement unit, a distance measurement unit, and a correction calculator to determine a correction value based on the difference between altitude and distance measurements, allowing for accurate elevation angle calculation using either the first elevation angle (based on AoA) or the second elevation angle (based on ToA) when the elevation angle exceeds a predetermined threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the array antenna is used to measure angles of arrival (AoA) based on phase difference between antenna elements, then the arrival directions of radio waves can be measured, but errors in the phase difference are increased when the elevation angle is large
Solution Approach 1:
The patent introduces an altitude measurement unit (using barometric pressure) and distance measurement unit (using ToA) as intermediary devices. These units provide alternative measurement paths that do not suffer from the phase difference errors affecting the AoA method at large elevation angles. The correction value, derived from the difference between altitude and distance measurements, acts as a mediator to compensate for AoA errors.
Solution Approach 2:
The system implements a feedback mechanism where the correction value calculated from altitude and distance measurements is fed back to correct the elevation angle obtained from AoA measurements. The elevation angle calculator selectively applies the correction based on the magnitude of the elevation angle, using the correction value when the absolute value exceeds a threshold angle, thereby improving measurement accuracy through feedback control.
2Ease of operation
If the AoA technique is used for elevation angle determination, then angle measurement is achieved, but accuracy deteriorates at large elevation angles
Solution Approach 1:
The system dynamically switches between different measurement strategies based on the elevation angle magnitude. When the absolute value of the elevation angle is small (within the threshold angle), the uncorrected AoA measurement is used. When the absolute value exceeds the threshold, the corrected elevation angle using the correction value is applied. This dynamic adaptation optimizes measurement accuracy across different operating conditions.
Solution Approach 2:
The patent changes the measurement parameters based on the elevation angle condition. For small elevation angles, the system uses the direct AoA measurement parameters. For large elevation angles, it transitions to using corrected parameters derived from the relationship between altitude, distance, and the correction value, thereby maintaining accuracy across the full range of elevation angles.
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 system reduces errors in measuring angles by using a correction value to switch between AoA and ToA techniques, ensuring accurate determination of elevation angles even at large angles, thereby improving positional accuracy.
Implementation Method 1
an altitude measurement unit provided on the aircraft and configured to measure an altitude of the aircraft with respect to the first communication unit
Implementation Method 2
a distance measurement unit configured to measure a distance between the first communication unit and the aircraft, based on a propagation time, or a phase, of at least one signal that is communicated between the first communication unit and the second communication unit
Implementation Method 3
an elevation angle calculator configured to determine a first elevation angle of the aircraft with respect to the first communication unit, based on phases that are obtained in a case where signals communicated between the first communication unit and the second communication unit are received by multiple antenna elements
Data Source
AI summary
A positioning system includes an elevation angle calculator that determines, as a second elevation angle, an inverse cosine of a first value, upon occurrence of a condition in which an absolute value of a first elevation angle is greater than or equal to a second predetermined angle, the second predetermined angle being greater than a first predetermined angle, the first value being obtained by dividing a second value that is obtained by correcting, with a correction value, an altitude measured by an altitude measurement unit, by a distance measured by a distance measurement unit. The elevation angle calculator selects any one of the first elevation angle and the second elevation angle, based on a value of the first elevation angle.