The Effect of Surface Condition of AlN–Mo Composite Bulk Absorbers on the Reduction of Microwave Radiation Reflection

To improve further the designs and ensure the stable operation of vacuum electronic devices that function in the ultra-high frequency (UHF) range at 1–100 GHz, the characteristics of microwave radiation absorption have been enhanced. We addressed the highly complex task of producing bulk absorbers made from AlN–Mo composites with a high attenuation level of 10–12.3 dB, which corresponds to a microwave radiation absorption coefficient of 37–56 dB/cm. They achieved a good low voltage standing wave ratio (VSWR) value of 1.5–1.6 in the frequency range of 9.3–10 GHz. The study found that chemical treatment of the absorber’s surface, which involves removing molybdenum particles using an acid mixture, improves matching by reducing microwave radiation reflection values, consequently decreasing the VSWR peak by 26–30%.