Comparison of frequency responses of spiral inductors with different figures

The results of a comprehensive investigation into the characteristics of in ductors fabricated by the GaAs monolithic microwave integrated circuit (MMI C) process are presented. Various spiral inductors with different figures w ere fabricated and measured, and their frequency responses were investigate d. The S-parameter optimization was used to estimate the lumped elements of the pi-equivalent circuit model of inductors. The simulated results indica te that the quality factor (Q) of the inductor is dominated by loss in the metal strip at lower frequency, and loss introduced by the substrate dissip ation tends to dominate the performance at higher frequency. In addition, t he inductance affects the Q value over the whole frequency range. The serie s resistance of a circular inductor is about 10% smaller than that of a squ are inductor with the same diameter. The reduction of the diameter and turn s decrease the IZ value at lower frequency, but the Q value is increased at higher frequency since the rapid drop of inductance induces the decrease o f Q(met) and the increase of Q(sub). The wide metal width increases Q(met) by the reduction of the resistance and the increase of inductance. To guide the design of inductor, the design formula was established based on experi mental results. It is expected that when the geometrical dimension is selec ted the formula will help us to predict the properties of inductors easily. Among the three types of inductor, the circular and octagonal inductors ha ve the higher quality factor and the lower loss, which implies that these t ypes of inductor are appropriate for GaAs MMIC applications.