A semidistributed HEMT model for accurate fitting and extrapolation of S-parameters and noise parameters

Accurate distributed and semidistributed models of field effect transistors for millimeter wave applications

“…Meanwhile, the semidistributed models in Refs 11. and12 indicate that the FET is terminated with the gate and drain wire‐bond pads on the same side, which is not consistent with the usual actual situation, whereas in the semidistributed model the proposed FET is terminated on each side. Meanwhile, each slice of the semidistributed model proposed is represented by a four‐port equivalent circuit by considering the source contacts on both sides of the FET as the reference ground instead of directly connecting each slice to the input ground, similar with that in the accurate distributed model, which reduces the number of the parasitic parameters and simplifies the calculation as well.…”

“…As shown in Figure 2a, the voltage and current along the distributed FET satisfy the following equations [12]: However, the elements of the parasitic impedance matrix Z are considerable complicated, because they include not only the resistance and inductance in series but also the capacitance in parallel. Therefore, a simpler process is proposed as follows.…”

“…When compared with the semidistributed models presented in Refs 11. and12, all the parasitic parameters of three electrodes are considered in the proposed one, which makes it more rigorous. Meanwhile, the semidistributed models in Refs 11.…”

“…A lot of literature is available on the analysis of propagation effects on frequency limitation of FETs [2–13]. There are two primary analysis methods: one is full wave analysis, which couples the Maxwell's equations and the Boltzmann transport equations and is a kind of numerical solution [2–4] and the other is equivalent distributed model, which takes the FET electrodes account as transmission lines, then the electrodes and intrinsic part of FETs are presented as equivalent distributed circuit [5–10].…”

“…When compared with the full wave analysis, the distributed model takes less computing time in doing device analysis; however, differential equations should be solved, which makes it inconvenient for circuit simulation and design. So a new kind of semidistributed model based on the distributed model shows up [11–13], which divides the FET into N identical slices along the gate width. When the width of each slice W s = W / N ( W is the gate width of one finger of a FET) is much smaller than the operating wavelength λ g , the propagation effects of each slice could be ignored; thus, each slice of the actual FET can be represented by the common lumped‐element model.…”