Theory of traveling-wave transistors

A distributed FET is treated as a problem of coupled active transmission lines over which the traveling waves grow by interaction. Models and equivalent circuits are proposed for evaluation of line parameters and propagation constants. Our calculations show that: 1) the gain increases with transistor width (or length of transmission line) up to about 2 cm, 2) at 15 GHz, a gain of 9 dB is achievable, and 3) the 3-dB bandwidth could be as large as 15 GHz. Possible applications of both types of traveling-wave transistors, unipolar and bipolar are discussed.