Inductorless filters: a survey I. Electromechanical filters

Since their invention early in the 20th century, filters have played an important role in electronic technology. However, the LC filter, which had been the type most widely used in the past, is now being phased out because of the change in design criterions imposed by the current trend toward microminiaturization. The problem of finding a replacement may be solved by implementing some of the inductorless filter methods described in this two-part article. Part I discusses the two basic groups of electromechanical filters-the monolithic crystal and ceramic types, and the mechanical filter, which is coupled with a transducer. Part II of this article, to appear next month, will consider linear active and digital devices.