Tapered Antenna Frame with Absorbent Material for Radar Cross Section Reduction
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Solution Overview
Problem
Integrating broadband array antennas with vehicles poses challenges due to impedance differences between the antenna and the vehicle hull, leading to high radar cross-sections, especially when the antenna has a small size and operates over a broad frequency band, causing scattering and increased side lobes.
Innovation Solution
An antenna frame with a tapering profile and absorbent materials is designed to surround the antenna aperture, creating a gradual transition between the antenna and the vehicle hull, reducing radar cross-section by matching electromagnetic impedances and absorbing surface currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If broadband array antenna is integrated directly with vehicle hull, then antenna functionality is maintained, but radar cross-section increases due to impedance mismatch and scattering
Solution Approach 1:
A transition structure with tapered profile and absorbent material is introduced as an intermediary between the antenna aperture and vehicle hull. This intermediate structure gradually transforms the electromagnetic impedance from the antenna to the hull, reducing scattering while maintaining antenna functionality.
Solution Approach 2:
The transition structure employs a tapered profile where the thickness or width varies continuously from the antenna aperture toward the vehicle hull. This gradual parameter change creates a smooth impedance transition, minimizing reflections and scattering across the broadband frequency range.
2Object-affected harmful factors
If frequency selective surface is used to reduce radar cross-section, then RCS is reduced at specific frequencies, but broadband operation is compromised
Solution Approach 1:
Instead of using frequency-selective surfaces with discrete resonant frequencies, the invention employs a tapered transition structure with continuously varying geometric parameters. This approach provides broadband impedance matching by gradually transforming the electromagnetic properties across a wide frequency range, maintaining effectiveness from 6 to 18 GHz.
3Area of stationary object
If small antenna array is used, then vehicle integration is improved, but scattered field beamwidth increases and side lobes are enhanced
Solution Approach 1:
The tapered transition structure acts as an intermediary that modifies the scattered field from the small antenna array. By providing a gradual impedance transition, it reduces the strength of scattered fields and suppresses side lobe levels, allowing small antenna apertures to be used without excessive scattering.
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 effectively reduces radar cross-section by minimizing scattering and side lobes, allowing for a lower RCS across a broad frequency band while maintaining the antenna's functionality and efficiency.
Implementation Method 1
a first absorbent material is attached to the bevelled side of the tapering profile
Implementation Method 2
the antenna frame comprises a transition region that has a tapering profile with a bevelled side... creating a gradual transition between the antenna and the vehicle hull, reducing radar cross-section by matching electromagnetic impedances
Data Source
Figure 1~2
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AI summary
An antenna frame for reducing radar cross section of a vehicle provided with a flat microstrip patch antenna array comprising a number of microstrip patches arranged in an array pattern, the antenna frame: - being arranged to surround the outer periphery of the flat antenna array - the frame comprising a first conductive sheet; - the first conductive sheet extending from the most peripheral patches and outward in a sloping manner; wherein dielectric and magnetic absorbent material are arranged to improve impedance transition from a point of the antenna to a point on the periphery of the frame, which is also contemplated as adjoining a vehicle fuselage.