Synthesis of a super broadband model for on-chip spiral inductors

A modified T-section equivalent circuit is proposed to model on-chip spiral inductors with extremely large bandwidth. This developed model combines a five-element modified T-section to include up to half-wavelength long transmission-line effects, and parallel and series feedback resonators to account for higher-order resonances present in the coil-coupling and ground-return paths. The modeled S parameters show excellent agreement with measured results over the entire measurement frequency range of 20 GHz and 50 GHz for a series of planar spiral inductors implemented on silicon and InGaAs substrates, respectively. The effective modeling bandwidth is at least several times larger than in a conventional PI-section model.