Ferroelectrics in Microwave Devices, Circuits and Systems: Physics, Modeling, Fabrication and Measurements (re)

Today’s wireless communications and information systems are heavily based on microwave technology, as are an increasing number of other industry sectors. The mobile phone is a typical example of a device which makes use of wireless technologies, often capable of also functioning as an Internet browser, GPS and/or TV. In order to cope with multiple communication channels and increasing bandwidth, whilst remaining user-friendly and cost-effective, both the mobile handsets and the associated systems must be agile (adaptable/reconfigurable).

The complex needs of society have inspired considerable interest in the field of cognitive and software defined radios and triggered extensive research in adequate components and technology platforms. To meet the stringent requirements to these systems, especially in agility and cost, new components with enhanced performances and new functionalities are needed. In this area, ferroelectrics have great potential and are already gaining ground.

Ferroelectrics are a class of materials characterized by spontaneous electric polarization. Components based on these materials have a broad range of commercial applications. The piezoelectric properties of the materials are exploited in sensors and actuators. When the electric dipoles are aligned (ferroelectric phase), the materials are widely used in memory cells. When the electric dipoles are not aligned (paraelectric phase), the materials have even greater potential for microwave applications. Many ferroelectrics, especially perovskites, exhibit good dielectric properties (low microwave loss and leakage currents), including an extremely high dielectric permittivity. As this permittivity is dependent on the applied electric field, mechanical stress and temperature, such materials are suitable for the development of tuneable microwave devices for applications in agile microwave systems.