Surface-Mount Antenna Array With Loop-Back Calibration for GPS-Free Altimetry
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Solution Overview
Problem
GPS-based navigation systems in aircraft are vulnerable to interference, jamming, and spoofing, and radio altimeters introduce delays and interference due to RF cabling, necessitating improved navigation solutions.
Innovation Solution
A combined radio altimeter and Doppler radar system with a surface-mountable antenna array and loop-back calibration, which digitizes RF signals at the antenna module, allowing for cable length-independent measurements and robust interference resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS-based navigation systems are used, then navigation accuracy and ease of deployment are improved, but vulnerability to interference, jamming, and spoofing increases
Solution Approach 1:
The system segments the navigation function into multiple independent components: GPS receiver, radio altimeter, and Doppler radar. Each component operates independently to provide navigation data, so if one system is jammed or spoofed, the others can compensate, reducing overall vulnerability while maintaining navigation accuracy through sensor fusion.
Solution Approach 2:
The system changes the operational parameters by operating radio altimeter and Doppler radar in frequency bands and modes optimized for their specific functions, rather than relying solely on GPS frequency. This parameter diversification makes it harder for a single interference source to affect all navigation systems simultaneously.
2Measurement precision
If radio altimeters with RF cabling are used, then altitude measurement capability is improved, but measurement delay and interference susceptibility increase
Solution Approach 1:
The invention extracts and removes the RF cabling component from the radio altimeter system. By using a surface-mountable antenna array directly coupled to the LRU without intermediate RF cables, the system eliminates the source of cable-induced delays and interference, achieving real-time altitude measurements without time loss.
Solution Approach 2:
The patent introduces a direct coupling mechanism (surface-mountable antenna array) as an intermediary between the LRU and the external environment, replacing the traditional RF cable intermediary. This new intermediary provides direct signal transmission without the delays and interference characteristics of RF cabling.
3Ease of operation
If surface-mountable antenna array with direct LRU coupling is used, then cable length constraints are eliminated and ease of installation is improved, but device complexity increases
Solution Approach 1:
The invention merges the antenna array and LRU into a single integrated surface-mountable unit. By combining these previously separate components into one module, the system eliminates the need for complex cable management and installation procedures while the integrated design manages internal complexity through modular architecture.
Solution Approach 2:
The surface-mountable antenna array with direct LRU coupling serves multiple functions: it provides radio altimeter capability, Doppler radar functionality, and eliminates cable-related constraints. This multi-functionality compensates for the increased device complexity by providing greater installation flexibility and eliminating cable management requirements.
4Measurement precision
If loop-back calibration procedure is implemented, then measurement accuracy is improved, but calibration time and procedure complexity increase
Solution Approach 1:
The system performs loop-back calibration automatically during the manufacturing or initialization process before the system is deployed. By completing the calibration procedure in advance, the measurement accuracy is optimized beforehand, and no additional calibration time is required during actual operation or maintenance.
Solution Approach 2:
The loop-back calibration procedure is designed to be self-executing, using the system's own components to calibrate itself without requiring external equipment or manual intervention. This self-service calibration minimizes the time and complexity involved by automatically performing the necessary adjustments during system initialization.
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 provides accurate altitude and speed measurements without GPS, reduces interference susceptibility, and facilitates easy retrofitting by eliminating cable length constraints, enhancing navigation reliability.
Implementation Method 1
a radio altimeter, which typically includes an antenna mounted to a surface of the aircraft and a line replaceable unit (LRU) that sends radio frequency (RF) signals to and receives return RF signals from the antenna
Implementation Method 2
The radio altimeter is configured to measure a height of the aircraft above the ground using a transmitted RF wave and a reflected RF wave from the ground below the aircraft
Implementation Method 3
Doppler radars have been deployed in order to measure ground speed independent of GPS or inertial measurements
Data Source
AI summary
A radio device includes a radio frequency (RF) unit and a surface-mountable antenna module coupled to the RF unit via an electrical connector. The RF unit includes first transmit circuitry, first receive circuitry, and a processing unit, and the surface-mountable antenna module includes a housing, second receive circuitry, and second transmit circuitry. During a calibration procedure, the RF unit is configured to output a calibration RF signal via the electrical connector, receive a first bitstream representing a sampled calibration signal via the electrical connector, and determine a time delay associated with the electrical connector based on the digitized calibration signal and the first bitstream. During the calibration procedure, the surface-mountable antenna module is configured to receive the calibration RF signal via the electrical connector, sample the calibration RF signal to generate the sampled calibration signal, and output the sampled calibration signal via the electrical connector as the first bitstream.