Wind Turbine Blade Radar Signature Reduction
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Solution Overview
Problem
Wind turbine blades, especially those made of composite sandwich materials, cause significant electromagnetic disturbances to radars due to their reflection of radar signals, which existing solutions fail to adequately address, leading to increased costs and complexity in adapting matching circuits for homogeneous walls.
Innovation Solution
A wind turbine blade with a hollow shell featuring a sandwich-type wall composed of two dielectric composite skins separated by a low dielectric constant core, equipped with an adaptation circuit that varies the electrical distance between the skins to reduce the radar equivalent surface, making the blade transparent in specific frequency bands, using inductive or capacitive behavior and susceptance to loop back radar waves to a central point of conductance 1 and susceptance 0, and employing flexible printed circuits with periodic metal patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If matching circuits with quasi-periodic metal patterns are applied to each skin of sandwich-type material, then radar transparency is improved, but device complexity and manufacturing cost increase significantly
Solution Approach 1:
The patent merges the matching circuit functions into a single layer positioned between the two skins of the sandwich structure, rather than applying separate matching circuits to each skin. This consolidation reduces the total number of matching circuits required while maintaining the radar transparency effect through the combined electrical distance adjustment.
Solution Approach 2:
The single matching circuit layer serves multiple functions: it adjusts the electrical distance for both skins simultaneously, provides a unified interface for radar wave interaction, and simplifies the overall structure. This multi-functional approach reduces complexity while achieving the same radar transparency objective.
2Ease of manufacture
If the blade wall is made of homogeneous dielectric material, then manufacturing is simpler, but radar transparency is harder to achieve compared to sandwich structure
Solution Approach 1:
The patent employs sandwich-type composite material consisting of two dielectric composite skins with different dielectric constants separated by a core layer. This composite structure enables radar transparency by allowing independent optimization of each skin's electrical properties, achieving better radar performance than homogeneous materials while maintaining manufacturing feasibility.
3Object-affected harmful factors
If adaptation circuits are added to reduce radar equivalent surface, then radar interference is reduced, but manufacturing cost and complexity increase
Solution Approach 1:
The patent applies matching circuits only in specific localized areas between the skins where radar wave interaction is most significant, rather than covering the entire blade surface. This localized approach reduces the total amount of matching circuit material and manufacturing complexity while effectively reducing radar interference in the critical zones.
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 the radar equivalent surface of the blade, achieving a reduction in reflection coefficients by more than 15 dB in specific frequency bands, thereby minimizing radar interference and reducing the number of matching circuits needed, thus lowering costs and simplifying the adaptation process.
Implementation Method 1
making it possible to reduce the radar equivalent surface of the blade by making said blade transparent in the frequency band of a radar near which said blade is intended to be installed
Implementation Method 2
a wall of the sandwich type, this wall being made up of at least two dielectric composite skins separated by a core made of a material of low dielectric constant
Implementation Method 3
comprises at least one adaptation circuit with inductive or capacitive behavior positioned inside the core
Implementation Method 4
comprises at least one adaptation circuit with inductive or capacitive behavior positioned inside the core
Implementation Method 5
The susceptance of the adaptation circuit making it possible to globally adapt the sandwich-type wall is given by...
Implementation Method 6
employing flexible printed circuits with periodic metal patterns
Data Source
Figure 1~4
Figure 5~6b
Figure 7a~7d
AI summary
The blade (1) has a hollow hull (2) locally provided with a sandwich type wall (2.1) having dielectric composite skins (7.1, 7.2) separated by a core (9) made of a low dielectric constant material. A capacitive or inductive behavior adaptation circuit is positioned within the core to reduce a radar equivalent surface of the blade by making the blade transparent in the frequency band of a radar at the proximity of which the blade is installed. The adaptation circuit is formed by low thickness flexible printed circuits i.e. epoxy glass circuits, on which metal tracks are etched.