A dual-band broadband absorber based on frequency selective surface (FSS) is proposed. This double-layer absorber consists of two layers of FSS structure; each layer has a unique construction and plays its wave-absorbing function in different frequency bands. In the low-frequency band, layer I is a transmission channel, and layer II effectively absorbs electromagnetic waves. Furthermore, layer I exhibits significant absorption characteristics in the high-frequency band, whereas layer II provides effective reflection. The combination of the two layers results in a remarkably effective absorption. Its reflectivity below - 10 dB covers a bandwidth of 5.5-14.8 GHz and 22.9-33.1 GHz, and its fractional bandwidth is 128%. The structure prevents external electromagnetic interference from affecting the antenna's performance, ensuring communication quality in critical frequency bands while reducing unwanted absorption in unwanted frequency bands. It is worth mentioning that the structure still has good stability under 45° oblique incidence. The physical mechanism is analyzed in detail by using an equivalent circuit model (ECM). The measurement results are in good agreement with those of simulation and ECM.
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