Achievements and Prospects of Microwave Distributed Amplifiers

A very successful example of Microwave Monolithic Integrated Circuits is the Distributed Amplifier (D.A.). It employs a number of amplifying elements positioned periodically between input and output transmission lines. The device parasitics, normally matched using conventional filter techniques, become then part of an artificial transmission line. Using this approach, monolithic broadband amplifiers have been realized. Small-signal and power amplifiers with bandwidths of many decades have been fabricated with upper cut-off frequencies above 40 GHz. However, also other broadband components have been developed such as wideband mixers and phase modulators. Numerous further concepts can be considered still in connection with this broadband feature.