Chapter 10 - Ceramic Dielectrics for Microwave Applications

Abstract

This chapter reviews material properties, processing, and physics of dielectric loss that are important for application of ceramic dielectrics for microwave. A wide range of materials can be considered to be ceramic dielectrics. Materials available for use in dielectric resonators have dielectric constants ranging from 10–100. In recent years good progress has been made in processing ceramic dielectric materials. As the mobile and satellite communications industry has grown, dielectric resonators have become an important technology. Although there has been considerable progress in processing, there is still no satisfactory model to accurately describe the dielectric loss of polycrystalline ceramics. To improve the properties of existing materials, a more in-depth understanding of the physics of the loss is required. The drive toward miniaturization requires the development of materials with a higher dielectric constant. Recent advances in cryogenic technology have opened new possibilities for ceramic dielectric resonators. This may even resurrect interest in materials that were previously discarded as impractical. The frequency range important for microwave communications is 500 MHz–30 GHz. Two main types of resonator are currently in use. The choice of resonator type depends on the operating frequency. For higher frequencies, above 2 GHz, dielectric resonators can be used. The aim of a significant portion of the research into dielectrics is to develop materials with higher dielectric constants that can be used to produce dielectric resonators for lower frequency applications.