Aircraft Antenna Array with Switched Beam Forming Network
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Solution Overview
Problem
Existing aircraft antennas face challenges with omnidirectional mode errors due to amplitude and phase differences in transmission paths, low efficiency due to strong mutual coupling, and bulkiness resulting from multiple metal plates, which limits their performance in TCAS, Transponder, and UAT systems.
Innovation Solution
An antenna system featuring an array of folded monopoles coupled to a switched beam forming network (SBFN) with feeding and shorting elements on a hollow dielectric cylinder, reducing the number of metal base plates and incorporating a broadband matching network for improved efficiency and compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a special calibration network with variable phase shifters and phase detectors is added to eliminate amplitude and phase differences, then omnidirectional mode accuracy is improved, but device complexity increases
Solution Approach 1:
The patent removes the complex calibration network (variable phase shifters, phase detectors, calibration signal source) from the antenna system. Instead of adding these components to eliminate errors, the invention uses a simplified antenna structure with four monopoles and a hybrid matrix that inherently provides accurate omnidirectional and directional patterns without requiring separate calibration hardware.
Solution Approach 2:
The antenna system performs self-calibration through its inherent symmetry and the use of a 3dB hybrid matrix. The four monopoles are fed with equal power and appropriate phase relationships automatically established by the hybrid matrix, eliminating the need for external calibration equipment while maintaining high accuracy in both omnidirectional and directional modes.
2Ease of manufacture
If a one-step quarter wavelength transformer matching network is used, then manufacturing simplicity is improved, but frequency bandwidth decreases
Solution Approach 1:
The patent divides the matching network into multiple sections rather than using a single one-step quarter wavelength transformer. This segmented approach allows each section to handle a portion of the frequency range, collectively providing broad bandwidth coverage from 978 MHz to 1090 MHz while maintaining manufacturing simplicity through modular construction.
Solution Approach 2:
The matching network is designed with adjustable elements that can be tuned to optimize performance across the wide frequency range. This dynamic adjustment capability allows the same physical structure to adapt to different frequencies within the TCAS/Transponder/UAT bands, achieving both ease of manufacture and broad adaptability.
3Stability of the object's composition
If three metal plates (ground plate, base plate, adapter plate) are used in the antenna structure, then structural stability is improved, but weight and cost increase
Solution Approach 1:
The patent combines multiple metal plates into a single integrated ground plate structure. Instead of separate ground plate, base plate, and adapter plate components, the invention uses one consolidated ground plate that provides all necessary structural support and electrical grounding functions, significantly reducing weight and manufacturing cost while maintaining structural stability.
Solution Approach 2:
The single ground plate performs multiple functions simultaneously: it provides mechanical structural support, serves as the electrical ground reference for all four monopoles, and acts as the mounting surface for the hybrid matrix and other components. This multi-functional design eliminates the need for separate specialized plates while maintaining all required stability and electrical performance.
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 solution enables efficient directional and omnidirectional operations without complex phase calibration, reduces weight and cost, and enhances antenna gain, making it suitable for high-frequency applications like TCAS, Transponder, and UAT systems.
Implementation Method 1
an array of folded monopoles coupled to a switched beam forming network (SBFN)... provides directional and omnidirectional operations
Implementation Method 2
a dielectric radome... feeding and shorting elements associated with each of the folded monopoles are strips formed on a hollow cylindrical dielectric element
Data Source
AI summary
A directional/omnidirectional antenna system is disclosed. A first printed circuit board has capacitive hats disposed thereon. Each capacitive hat is in association with one of an array of folded monopoles. A second printed circuit board has a switched beam forming network formed thereon. The switched beam forming network is configured to provide a predetermined omnidirectional antenna operation at a first switching position, and a predetermined directional antenna operation at a second switching position. Each of a plurality of feeding elements is associated with one of the folded monopoles. Each feeding element is coupled to one of the capacitive hats and to an antenna terminal. Shorting elements of the folded monopoles are coupled to the capacitive hats and to a ground plate of the antenna. A plurality of decoupling elements improve the antenna pattern for directional and omnidirectional modes and provide greater antenna gain.