Antennas, Base and Mobile Stations -12.Filter
A number of filters for the RF and IF bands as well as base band filters are used in mobile and portable units for such purposes as interference elimination and channel selection. These filters are classified according to their operating principles and structures into dielectric filters, SAW filters, LC filters, quartz filters, piezoelectric ceramic filters, digital filters, etc. In the selection and design of these filters, it is important to consider the required electrical performance and size for the specific application.
In pursuing the trend towards compact and lightweight portable telephones, miniaturization technologies for various filters have been developed. In the case of the high dielectric filter for the 800-MHz band, the specific inductive capacity has been remarkably increased from the 10 to 30% range, and now reaches 90% capacity. Moreover, base band filters have evolved from CR active filters using hybrid ICs to switched-capacitor filters using monolithic ICs.
Application According to Filter Type