Design considerations for the gate circuit in distributed amplifiers

An analytic model for the design of the elementary cell of the gate circuit in distributed amplifiers is discussed. The used approach is based on the image parameter representation of two-port networks. A closed form expression for the input impedance of the amplifier is provided. Design considerations for the gate circuit are presented based on this analytical result. The simulation of the gate network is performed by means of a commercial software package, including the physical models of the microstrip transmission lines and discontinuities present in the actual structure. Moreover, an hybrid circuit with the same configuration of the gate network has been manufactured. The agreement between experimental numerical and analytical data is remarkable.