Direction Finding Using Rotating Antenna Array Calibration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing direction finding (DF) systems, particularly amplitude-comparison systems, suffer from low accuracy and high sensitivity to multipath interference and non-ideal antenna characteristics, which cannot be corrected by calibration, limiting their ability to determine the angle of arrival (AOA) of radio frequency signals with the required precision.
Innovation Solution
A direction finding system utilizing a multi-antenna array with a rotatable mount, where antennas are calibrated to determine a rotation angle to eliminate ambiguities, and the power difference between adjacent antennas is processed to calculate the angle of arrival by subtracting the rotation angle from the intersection angle, thereby improving accuracy and reducing sensitivity to environmental factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If amplitude-comparison DF systems are used, then the system is inexpensive and compact, but the measurement precision is low and sensitivity to multipath interference is high
Solution Approach 1:
The system performs preliminary calibration by rotating the antenna array through 360 degrees to measure received signal strength at multiple angular positions before actual direction finding. This pre-measurement phase creates a calibration dataset that stores the relationship between antenna orientation and signal strength, enabling more accurate AOA determination during operation without requiring expensive hardware modifications.
Solution Approach 2:
The invention adds a temporal dimension to the measurement process by taking multiple measurements at different rotational positions rather than relying on a single static antenna configuration. The system measures signal strength at N different angular positions (0°, 360°/N, 2×360°/N, ...) and uses this multi-dimensional data set to calculate AOA, effectively transforming a 2D spatial problem into a 3D problem that includes the time/rotation dimension.
2Measurement precision
If interferometer systems are used, then the angle of arrival measurement accuracy is high, but the device complexity and cost are high
Solution Approach 1:
The system employs a rotatable antenna array that dynamically changes its orientation during calibration and measurement. Rather than using multiple fixed antennas in a complex interferometer configuration, the invention uses a single antenna array that rotates to different positions, transforming a static multi-antenna problem into a dynamic single-array problem that achieves similar measurement accuracy with reduced hardware complexity.
Solution Approach 2:
The calibration process creates a digital copy or model of the antenna array's signal strength characteristics at different orientations. This calibration dataset serves as a reference model that can be used to determine AOA without requiring the physical presence of multiple antennas or complex interferometer hardware, effectively replacing physical complexity with information processing.
3Measurement precision
If the antenna array is rotated to eliminate ambiguities, then the measurement precision is improved, but the measurement time increases
Solution Approach 1:
The system uses periodic rotation of the antenna array through 360 degrees at predetermined angular increments to collect calibration data. This periodic action ensures that all angular positions are sampled systematically, allowing the system to resolve ambiguities in AOA determination while maintaining a structured and efficient measurement sequence that minimizes total calibration time.
Solution Approach 2:
The system measures signal strength at more angular positions than the minimum single position would require, taking N measurements at positions 0°, 360°/N, 2×360°/N, etc. This excessive action of measuring at multiple positions rather than one provides redundant data that resolves ambiguities and improves accuracy, while the measurements can be performed efficiently during normal system operation or calibration phases.
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 achieves higher accuracy in determining the angle of arrival with reduced sensitivity to multipath interference and other environmental issues, providing AOA measurements with improved precision compared to traditional systems.
Implementation Method 1
a plurality of directional antennas positioned to face different directions for receiving a target signal from a transmitter
Implementation Method 2
A receiver unit connects to the directional antennas and down converts the radio frequency signals to intermediate frequency (IF) signals
Data Source
AI summary
A direction finding system for finding the angle of arrival of a target signal from a transmitter. The system includes a plurality of directional antennas positioned to face different directions for receiving the target signal. The antennas are mounted as an antenna array on a rotatable mount for supporting and rotating the antenna array. A receiver unit down converts the RF target signal to IF signals that are digitized by an A/D converter providing digital values. A computer computes the power in the signals from the A/D samples. A computer stores calibration information for the directional antennas, processes the digital values and the calibration information to determine a rotation angle α for rotating the antennas to provide new digital values, processes the new digital values and the calibration information to determine an intersection angle, and subtracts the rotation angle from the intersection angle to determine the final value for the angle of arrival of the target signal.