Integrated Antenna Resistive Sheet Radar Cross Section Reduction
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Solution Overview
Problem
Integrated antennas in stealth objects face challenges in reducing radar cross section (RCS) due to in-band diffraction, out-of-band diffraction, structural RCS, antenna-mode RCS, and grating lobes, which contribute to their radar visibility.
Innovation Solution
A thin resistive sheet with a tapered resistivity distribution is applied along the perimeter of an integrated antenna array to provide a smooth transition of scattering properties between the antenna and its surrounding material, effectively reducing the radar cross section by eliminating discontinuities in the reflection coefficient and directing diffracted waves away from the radar.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If an antenna is integrated in a non-absorbing environment, then the antenna can operate efficiently, but in-band diffraction increases radar cross section
Solution Approach 1:
A resistive sheet is introduced as an intermediary layer between the antenna and the surrounding environment. This sheet has a tapered resistivity distribution that gradually transitions from the antenna region to the surrounding material, serving as a mediator that smooths the scattering properties and reduces edge diffraction while maintaining antenna functionality.
Solution Approach 2:
The resistivity parameter of the sheet is varied spatially according to a tapered distribution. By changing the resistivity parameter continuously across the transition region, the scattering properties are smoothly transformed, reducing the abrupt impedance discontinuity that causes diffraction and increasing radar visibility.
2Shape
If there is a rapid change in scattering properties between antenna and surroundings, then antenna structure is defined, but edge diffraction increases radar visibility
Solution Approach 1:
The scattering properties are changed gradually rather than abruptly by implementing a tapered resistivity distribution in the sheet. This continuous parameter change smooths the transition between the antenna region and the surrounding environment, eliminating the rapid change that causes edge diffraction while still maintaining clear structural definition.
3Area of stationary object
If inter-element spacing is larger than half wavelength, then antenna array coverage is improved, but grating lobes increase radar cross section
Solution Approach 1:
The resistive sheet acts as an intermediary that modifies the scattering properties at the edges of antenna elements. By providing a gradual transition in resistivity, it reduces the strength of edge-diffracted waves that would otherwise form grating lobes, allowing larger inter-element spacing without significant increase in radar cross section from grating lobes.
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 significantly reduces the mono-static radar cross section of integrated antenna arrays, transforming their scattering properties to match those of a perfectly electrical conductor, thereby minimizing radar visibility across a wide frequency band.
Implementation Method 1
The in-band diffraction is significant if the antenna is integrated in a non-absorbing environment. The out of band diffraction can also contribute to the so called radar cross section (RCS) if there is a phase difference between the reflection from the antenna and the reflection from the surroundings.
Implementation Method 2
The out of band diffraction can also contribute to the RCS if there is a phase difference between the reflection from the antenna and the reflection from the antenna surrounding.
Data Source
AI summary
An antenna structure including an antenna 10 with an outer main surface 11, where said antenna 10 is integrated in a surface of a surrounding material 20. Further comprising a transition zone 30 arranged along the perimeter of the main surface 11 and overlapping the main surface, where the transition zone 30 comprises a layer of a resistive material with a resistivity that varies with the distance from an outer perimeter of the transition zone 30 to enable a smooth transition of the scattering properties between the antenna 10 and the surrounding material 20.