Monolithic coplanar waveguide travelling wave transistor amplifier

Abstract

A microwave and millimeter wave amplifier consisting of a field effect travelling wave transistor monolithically integrated into a coplanar waveguide having input, output and matching sections is disclosed. The amplifier consists of a semi-insulating substrate doped on its upper surface to form within an active region of the device a doping layer of predetermined conductivity type, such as an N type layer. At the lateral edges of the active region the N type material is further doped to produce N+ type regions for receiving source electrodes, while a central part of the active region is similarly doped to produce an N+ type region for receiving a drain electrode. A gate line having a bifurcated terminal end extends into the spaces between the drain electrode and the spaced source electrodes and forms junction contacts with the N type layer in the active region. A pair of ground lines extending the length of the substrate are formed as part of the two source electrodes, while the drain electrode is formed as part of a drain line. The gate and ground lines cooperate to form an input and an input matching structure, while the drain and ground lines cooperate to form a coplanar output transmission line. A major feature of the proposed amplifier structure is that all of the circuit elements and transistor elements are placed on the same surface to facilitate fabrication, thereby to obtain low cost and high performance.