Distributed Small Signal Modelling for Multi-port GaAs FETs

The design of Microwave and Millimeter-wave Monolithic Integrated Circuits (MMIC) requires a meaningful and accurate characterization of the electron device along with information about the changes caused by the process parameter variations. Meanwhile, increasing application of multi-port GaAs FETs, adopted for side-biasing in the higher level of MMIC integration, has led to increased research focus on its modeling. However, conventional lumped models, based on simple linear rules or completely empirical expressions may not be sufficiently proper at relatively high operating frequencies. One of the main problems is related to the limitation of the lumped description of intrinsically distributed phenomena such as the coupling effect caused by metallic stripes and grounded vias. Moreover, their side-biasing ports also can not be well modeled by those conventional methods. Therefore, the transistor must be distributed as both the parasitic phenomena and the intrinsic elements to achieve precisely modeled especially in high-frequency domain. This paper presents a novel approach to multi-port distributed modeling for GaAs FETs with different multi-fingers and physical structures (Fig. 1), which describes the GaAs FETs based on the electromagnetic field theory and circuit analysis.