利用带原位BN涂层的吸波SiC纤维为增强体，以硅氧碳（SiOC）陶瓷为基体，采用先驱体浸渍裂解（precursor infiltration pyrolysis，PIP）工艺制备SiC-BN/SiOC陶瓷基复合材料。在7个PIP制备周期后复合材料实现致密化，密度为2.05 g/cm³，孔隙率为4.28%。采用矢量网络分析仪测试介电常数，结合传输线理论对复合材料在8.2~18 GHz下室温至800 ℃的吸波性能进行计算优化。结果表明：SiC-BN/SiOC复合材料的室温介电常数呈现出明显的频散效应，使其具有良好的宽频吸波特性。当复合材料厚度为2.1 mm时，在X波段和Ku波段反射损耗优于-10 dB的最大频宽为5.7 GHz。此外，复合材料的复介电常数实部和虚部随着环境温度的升高而增大。在宽频反射损耗优于-5 dB的水平下，材料的最优厚度由2.3 mm（200 ℃）降至1.1 mm（800 ℃）。

The SiC-BN/SiOC ceramic matrix composites are prepared through the precursor infiltration pyrolysis（PIP） process， using wave-absorbing SiC fibers with in-situ BN coatings as reinforcements and SiOC ceramic as the matrix. After 7 PIP preparation cycles， the composite achieves densification with density of 2.05 g/cm³ and porosity of 4.28%. The dielectric constants are tested with vector network analyzer. Using transmission line theory， the microwave-absorbing properties of the composites from room temperature to 800 ℃ at 8.2-18 GHz are optimized. The results show that the dielectric constants of the SiC-BN/SiOC composites exhibits significant frequency dispersion effects， leading to broadband microwave-absorbing properties. When the thickness of the composites is 2.1 mm， the maximum bandwidth of the reflection loss better than -10 dB in the X band and the Ku band is 5.7 GHz. As the ambient temperature increases， the real and imaginary parts of the complex permittivity of the composites both increase. For reflection loss better than -5 dB in a wide bandwidth， the optimum thicknesses decrease from 2.3 mm （200 ℃） to 1.1 mm （800 ℃）.