Dielectric powder loaded coaxial-cavity filters

In this paper we demonstrate the use of low-loss powders in the design and fabrication of RF filters. Initially, several different powders are tested for their RF performance - in particular their relative dielectric permittivity and loss tangent. Then, based on the information obtained in this way, the best performance powder is used to design a 5 pole Chebyshev filter operating at a centre frequency of 779 MHz, with a bandwidth of 17 MHz. Upon fabrication of the filter housing, the filter cavities are filled with the powder. Compaction of the powders is achieved in a systematic way and has resulted in stable performance.