Small-signal modeling approach to 0.1-μm metamorphic HEMTs for W-band coplanar MMIC amplifier design

We present an accurate and reliable modeling method for designing the W-band (75-110 GHz) small-signal millimeter-wave monolithic integrated circuit (MMIC) amplifiers with the GaAs-based 0.1-μm metamorphic high electron-mobility transistors (MHEMTs). For this, we propose an improved process control monitoring (PCM) pattern layout for the MHEMT modeling and a small-signal equivalent circuit model of 17 elements accounting for the feedback capacitance (C_pgd) and output conductance time delay (τ_ds). The modeling technique adopts a gradient optimizer with the initial values of the extrinsic parameter set determined from the cold-FET measurement avoiding the forward gate-biasing in a frequency range of 0.5-65 GHz and the intrinsic parameter set obtained at an operating hot-FET condition in our W-band design frequency range. On the basis of the proposed small-signal equivalent circuit model, we design and fabricate 1- and 2-stage W-band MMIC amplifiers using the MHEMTs (30-μm gate width, 2 gate fingers) and a coplanar waveguide-based MMIC process. The measurements of the fabricated MMIC amplifiers show an excellent agreement with simulation data in the design frequency range.