IMPROVED EQUIVALENT-CIRCUIT MODEL OF GAAS-FET SWITCH FOR MMIC-PHASE-SHIFTER DESIGN

An improved equivalent circuit model of a GaAs FET switch for MMIC pha se shifters is proposed that incorporates distributed lines into a lum ped-constant equivalent circuit to account for distributed-line effect s. The validity of the proposed model is demonstrated by applying a co upled-wave analysis to the FET switch. Comparison of the measured and the simulated phase angles of the S-parameters shows that the improved model gives much better accuracy than the lumped-constant model. X-ba nd six-bit MMIC phase shifters designed using the improved model are a lso described.