3.3.2.1 Velvet structure fabrics

The fibers having electromagnetic properties are scattered as the fluff of the fabric on the surface, or are consolidated as a U-shaped structural unit on the fabric to form the fluff, and thereby a velvet structure fabrics with good radar wave scattering property is obtained.

The woven velvet fabric for decoration and its reflection coefficient is displayed in Figure 22. It can be seen from the test results that the tested structural unit achieves attenuation of 5 dB in the bandwidth of 10 GHz, and the peak value reaches 30 dB. This is mainly due to the angle between the metal fluff of the structural unit and the plane of the sample. When electromagnetic waves are incident onto the sample, those metal fluffs with a certain angle in the plane have a certain scattering of the incident electromagnetic waves, which reduces the energy received by the receiving antenna, so that the reflection coefficient is reduced.

periodic three-dimensional structure, and after being attenuated in the threedimensional structure, the reflected waves and the transmitted waves are again

The schematic diagram of electromagnetic wave incident three-dimensional structure.

3.3.1.2 The electromagnetic wave scattering characteristics of the concave-convex element

conforms to the law of reflection, as shown in Figure 19. The concave-convex natural surfaces can be broken down into a series of planar elements with smallsized geometries, which is called roughness. The roughness of the scattering surface

radiates and shoots in all directions, becoming a scattering field, as shown in

Electromagnetic waves are reflected at the interface of different medium, which

If the surface is smooth, the incident energy would form two plane waves after interacting with the surface. One is a surface-reflected wave whose angle with the normal is the same as the angle of incidence, and the direction is opposite, as shown in Figure 20. The other is refracted or transmitted waves with downward surface. If the surface is rough, the incident energy interacts with the surface and then

generated at the lower surface interface.

Dielectric column periodic three-dimensional structure.

Electromagnetic Materials and Devices

is very important in the surface scattering.

structure

Figure 17.

Figure 18.

Figure 21.

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Figure 22. The woven velvet fabric for decoration and its reflection coefficient.
