Microwave dielectrics

In the last 20 years the field of microwave communications has seen exceptional growth. It has been estimated that there are over 55,000 new users of cellular communications every day. This is largely due to the wish of most people for mobility as a key feature of communications. This growth places an enormous burden on the filters to the extent that filters using current technology simply cannot cope with the increased traffic demand. There is a requirement for systems with lower insertion loss, steeper filter skirts, better selectivity and ideally all of these with miniaturisation. In this paper, dielectric resonators are discussed. The interest in dielectric resonators is a direct consequence of the hurdles facing current technology. Dielectric resonators are now being developed with extremely attractive properties as well as the inherent potential for miniaturisation. The key properties are seen to be the dielectric loss (tan δ) the dielectric constant (ε´) and the temperature coefficient of the resonant frequency (TCf)