The effective trace resistance of a multiturn spiral inductor operating at high frequencies is known to increase dramatically above its dc value, due to proximity effect or current crowding. This phenomenon, which dominates resistance increases due to skin effect, is difficult to analyze precisely and has generally required electromagnetic simulation for quantitative assessment. Current crowding is studied in this paper through approximate analytical modeling, and first-order expressions are derived for predicting resistance as a function of frequency. The results are validated through comparisons with electromagnetic simulations and compared with measured data taken from a spiral inductor implemented in a silicon-on-sapphire process.

The effective series resistance of a multi-turn spiral inductor operating at high frequencies is known to increase dramatically above its DC value due to proxhity-effect or current crowding. This phenomenon is difficult to analyze precisely and has generally required electromagnetic . simulation for quantitative assessment. Current crowding is studied in this work through approximate analytical modeling and fvst order expressions are derived for predicting resistance as a function of frequency. The results are validated through electromagnetic simulation and with measured data taken from a spiral inductor implemented in a Silicon-on-Sapphire process.

SUMMARYThe magnetic field distribution within a square spiral inductor is investigated in this paper by summing closed-form expressions for the fields from each segment. Plots illustrating the variation of the normally directed B-field penetrating the surface of the spiral traces are then developed for a variety of perspectives. The expressions and insight gained represent an essential step in developing a detailed model of effects such as current crowding, which significantly limit the spiral's performance in practical circuits.

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