The present article is an introduction to the topic of active antennas. The first section is a description of the field suitable for reading by almost any undergraduate science major. The next section is an in-depth reexamination of the subject, including equations and some derivations. Its basic idea is to provide the reader with enough tools that he or she can evaluate whether it is an active antenna that he or she might need for a specific application. The final section is a discussion of where active antennas are finding and will find application.
We should mention here that, if one really needs to design active antennas, one will need to go further than this article. The set of references to the primary research literature given in this article is by no means complete, nor is it meant to be. A good way to get started on the current literature on this topic would be a reading of the overview monograph of Navarro and Chang (1). We will not cover active amplifiers in this article. However, this topic is treated in the book edited by York and Popovic (2).