3.4 Frequency selective surface textile materials

## 3.4.1 The structure and properties of frequency selective surface textile materials

Frequency selective surface (FSS) is an infinitely large periodic array structure that is one-dimensional, two-dimensional, etc. It is mainly divided into two types: patch type and aperture type, which have frequency selective characteristic for the propagation of electromagnetic wave in space. The patch type can totally reflect electromagnetic waves of a specific frequency, and the aperture type can transmit all electromagnetic waves of a specific frequency.

The textiles are light, soft, and flexible in processing. Relying on the media of textile materials, textile processing technology will qualify the textile products to attain the filtering characteristics and light, soft, and other characteristics, which can be applied in more fields [13]. Flexible periodic array structure prepared by textile processing technology is called frequency selective fabric (FSF). According to the filtering characteristics, the frequency selective fabric can be divided into four frequency response characteristics: high pass, low pass, band pass, and band stop, as shown in Figure 29.

#### Figure 29.

The four frequency response characteristics of the frequency selective surface. (a) High pass; (b) low pass; (c) band stop; and (d) band pass.

woven into a plain fabric with a square weight of 127 g/m<sup>2</sup> (as shown in Figure 26). The fabrics are treated at different temperatures to obtain fabrics with different

It can be seen from Figure 27 that the fabrics have different degrees of unevenness at different heat processing temperatures. The higher the treatment temperature, the more obvious the uneven structure; the lower the treatment temperature, the smaller the uneven structure. At 58°C, the fabric has a smaller degree of

concave and convex structures, as shown in Figure 27.

Comparison of reflection coefficients under different conditions.

Stainless steel fabrics with concave structure embedded with high heat shrinkage wires.

shrinkage.

Figure 28.

202

Figure 26.

Figure 27.

The original plain weave.

Electromagnetic Materials and Devices

3.4.2 The processing of frequency selective surface textiles
