Novel fast multiline analysis of parasitic effects in CPW inductors for MMICs

The author presents a novel multiline modeling of monolithic microwave integrated circuit (MMIC) spiral inductors in coplanar waveguide (CPW) technology. Starting from transmission line parameters calculated for only single lines and pairs of lines, a distributed equivalent circuit is established for each section of multicoupled lines in the structure. It readily yields the S-parameters of the section. An adequate interconnection of sections having different topologies results in the S-matrix of the device. Our technique is wideband, fast, and fully scalable. It predicts on-line the effect of the underpass and of spurious propagation along the coplanar waveguide (CPW) grounding. It is shown that a significant frequency shift is due to the combination of those two effects. Results are validated by measurements on SOI inductors, up to the second self-resonance frequency.