Three-Dimensional Fully Symmetric Inductors, Transformer, and Balun in CMOS Technology

This paper presents novel three-dimensional (3-D) symmetric passive components, including inductors, transformers, and balun. Layout areas of these components are drastically reduced by 32% to 70%, while the symmetry of the input and the output ports is still maintained. The inductance mismatch in the 3-D transformer is less than 0.1%, and the coupling coefficient can be up to 0.77. The 3-D balun manifests less than 0.6-dB gain mismatch for 10-GHz range, and the phase error is less than 7deg from 1- to 10-GHz frequency range according to measurement results. Furthermore, the self-resonant frequency (f
_SR
) of the proposed architecture is improved by 32% to 61% in contrast to their planar counterparts. On the other hand, the quality factor is degraded by less than 2 for the sake of using lower metal layers. The distributed capacitance model is utilized to validate their superiorities in f
_SR
. All the devices are fabricated in a generic 0.18-mum CMOS process.