Airborne Goniometry Calibration Across Low Frequencies In Flight
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Solution Overview
Problem
Current methods for calibrating airborne goniometry apparatuses at low frequencies are time-consuming and expensive, and cannot account for the metal structure of the air carrier, requiring large anechoic chambers that do not exist for low-frequency calibration.
Innovation Solution
A method involving the transmission of two orthogonal calibration signals by a calibration transmitter on board an air carrier, allowing in-flight calibration that accounts for the air carrier's metal structure, enabling quicker and less expensive calibration by measuring responses for multiple polarizations and frequencies, with frequency and angular position interpolation to cover entire ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If calibration is performed in an anechoic chamber, then measurement precision is improved, but device complexity and cost increase significantly due to the large chamber dimensions required for low frequencies
Solution Approach 1:
The patent introduces a calibration transmitter as an intermediary device that enables calibration to be performed in-flight using natural propagation conditions. The transmitter sends calibration signals to the airborne goniometry apparatus, allowing calibration without requiring a large anechoic chamber while maintaining measurement precision through the use of known signal characteristics and geometric relationships
Solution Approach 2:
The patent replaces the mechanical/physical infrastructure of a large anechoic chamber with an electromagnetic field-based calibration method. Instead of using physical absorptive structures to control reflections, the system uses signal processing and geometric calibration approaches that work in the natural electromagnetic environment during flight
2Measurement precision
If calibration is performed for each frequency and polarization separately, then measurement precision is improved, but loss of time increases significantly
Solution Approach 1:
The patent merges multiple calibration measurements into a single in-flight calibration operation. By transmitting calibration signals with multiple polarizations simultaneously and using the airborne apparatus to measure responses across different frequencies and angles during flight, the system combines what would traditionally require separate calibration sessions into one efficient process
Solution Approach 2:
The calibration method achieves multi-functionality by obtaining calibration data for multiple frequencies, polarizations, and angular positions simultaneously. The single calibration flight produces a comprehensive calibration table that serves all these parameters, making the calibration process universally applicable across the operational range of the goniometry apparatus
3Adaptability or versatility
If in-flight calibration is performed to account for metal structure effects, then adaptability is improved, but measurement precision may worsen due to environmental interference
Solution Approach 1:
The patent converts the harmful effect of the air carrier's metal structure into a beneficial adaptation. Instead of trying to eliminate or avoid the metal structure's influence on electromagnetic waves, the calibration method explicitly accounts for these effects by performing calibration in the actual flight environment. The metal structure's impact becomes part of the calibrated system characteristics, improving adaptability while maintaining precision through proper signal processing
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 method reduces calibration time and cost by enabling precise in-flight calibration for low frequencies, covering multiple polarizations and frequencies with minimal equipment, and allows for interpolation to determine unmeasured data points, thus optimizing the calibration process.
Implementation Method 1
transmitting, by means of a calibration transmitter, at said given frequency and in the direction of said goniometry apparatus, at least two calibration signals, with polarizations orthogonal to each other
Data Source
AI summary
The invention includes a method for calibrating at low frequency and in-flight a goniometry apparatus including an antenna array, on board an air carrier. The method includes for an angular position of reception, calibrating the airborne goniometry apparatus at a given frequency, comprising transmitting, by means of a calibration transmitter, at the given frequency and in the direction of the goniometry apparatus, at least two calibration signals, with polarizations orthogonal to each other. The method also includes measuring a response of the antenna array for each of the signals. The invention also includes a system implementing such a method.