Analysis of Travelling-Wave Inverted-Gate Field-Effect Transistors

A unified approach to the analysis the traveling-wave Inverted-Gate FET (INGFET) is presented. The equivalent circuit parameters of the GaAs Inverted-Gate FET, with submicron gate-length, is obtained using a two-dimensional computer model which takes into account the non-stationary electron dynamics. The parameters of the passive transmission line, corresponding to the INGFET, are obtained using a quasi-TEM wave approach. The conductor losses of this structure are estimated using the Incremental-Inductance Rule. The coupled mode theory is used to derive the wave equation describing this traveling-wave transistor. The results show the existence of a fast growing mode along the device electrodes. It is also shown that this mode can be excited alone by appropriate matching and feeding arrangements. Improper matching and feeding lead to a narrower bandwidth due to the resonance phenomenon of the resulting standing wave.