The Transistor, a Microwave Filter Element

Active filters offer a method for reducing the size of microwave filters without degrading performance. In addition, with active filters, network functions can be realized that are otherwise unrealizable. With the arrival of compact solid state techniques at microwave frequencies, the possibility for active microwave filters is emerging. Since transistors are one of the most likely components for active filter applications, it is of interest to see how microwave transistors can be used in filter applications. The purpose of this paper is to discuss several approaches to active microwave filters and to show examples of how transistor filters have been constructed.