Broadband Microwave Absorption Properties Of Magnetic Composite Structure Embedded With FSS

With the rapid development of stealth technology and electronic products, high-performance microwave absorber is eagerly pursued. Especially main attention is paid to expand microwave absorption bandwidth under the condition of limited thickness. Therefore, design and fabrication of magnetic composite structures(MCSs) consisting of frequency selective surfaces(FSSs) and magnetic sheets are extensively investigated in this thesis. And the microwave absorption properties of single-layer and double-layer FSS-embedded MCSs are systematically discussed. Finally, broadband MCSs with the thickness of only 2.2 mm are also presented. The main results are outlined as follows:The MCS based on a single-layer resistor FSS is designed and optimized by High Frequency Structure Simulator(HFSS). At first, FSS and magnetic sheets are respectively prepared by chemical etching method and rubber mixing method. And then electromagnetic parameters of magnetic sheet and microwave reflectivity of MCS are respectively measured by coaxial line method and arch method. The results show that experimental results are in good agreement with the simulations. And the use of resistor FSS makes a significant increase of operating bandwidth compared to single magnetic sheets. Under the condition of normal incident electromagnetic wave, it has remarkable absorptive performance with the reflectivity below-10 d B with the thickness of 2 mm in the range of 6.1~18 GHz. Furthermore, the MCS exhibits high oblique incidence and great stability of polarization when the incident angle and polarizing angle ranges from 0° to 30° and 0° to 90°(normal incidence) respectively.To increase the operating bandwidth of the aforementioned MCS, a ring FSS studied is embedded. And two kinds of typical double-layer FSS-embedded MCSs are designed and fabricated. Their microwave absorption properties are analyzed through the simulation and microwave reflectivity measurement. The results show that when the ring FSS is embedded, an low-frequency absorption peak which will improve the microwave low-frequency performance appears. After incorporating 8*8 ring FSS, the operating bandwidth with the reflectivity below-9 dB increases from 6~18 GHz to 4.8~18 GHz. While embedding 12*12 ring FSS, the operating bandwidth with the reflectivity below-8 dB increases from 5.8~18 GHz to 4.3~18 GHz. Nevertheless, both double-layer FSS-embedded MCSs with total thickness comparison only increases by 0.15 mm. The results also show that both of them keep high oblique incidence stability and great stability of polarization(normal incidence).The investigation of MCSs embedded FSS lays a theoretical foundation for broadband design of novel absorption materials, and also opens up a new route for design and realization of high performance radar absorption materials and structures.