Comparison Study on Single-layered and Double-layered Differential Symmetric Circular Spiral Inductors

Based on the Ansoft 3D electromagnetic field software HFSS and the typical lumped equivalent-circuit model of spiral inductors on silicon (SIOS) for RF integrated circuits (RFICs), the comparison study of single-layered and double-layered differential symmetric circular spiral inductors has been given. The numerical analyses showed that the former can give better results of quality factor (QF) and self-resonant frequency (SRF) and the L value of the former can satisfied the nH level requirements where the Q factor obtains its highest value. Experimental results showed that the former can gives a 50.5% increase for the maximum Q value and 164.5% increase for the SRF whereas the latter can supply over 3 times larger L value. The simulation results have good agreements with the theoretical analyses. At last the design guidelines were given according to the simulation and experimental results.