Microwave attenuation performance of MgO-Mg₂SiO₄-SiC composites lossy button

MgO-Mg₂SiO₄-SiC diphase microwave attenuation lossy buttons are manufactured by hot-pressing method at 1500°C for 1 hour. The microwave attenuation characteristics of the diphase material with different proportioning of MgO and Mg₂SiO₄ in X band (8~12 GHz) is tested by the network analyzer. Effects of different SiC addition on the microwave characteristics are investigated. The results show that the attenuation frequency of the hot-pressing MgO and Mg₂SiO₄ are 10.68 GHz and 11.80 GHz respectively. The attenuation frequency of the MgO-Mg₂SiO₄ composites are between them, and it will shift to higher frequency as the Mg₂SiO₄ phase increased. The additive of SiC will decrease the apprent prosity of the composites and would make the anttenuation frequency shift to lower one. From the analysis of the testing principium and the property of wave-guide, it is found that the lossy buttons with 6.1 mm of diameter and 4.2 mm of height can prevent the un-wanted frequencies in the traveling wave tube only if they satisfied 9.9 < ε_r < 18.66, and the attenuation frequency f₀ is 37.7 × ε_r^-0.5(GHz).