Self-rolled-up tube transformers: Extreme miniaturization and performance enhancement

On-chip lumped RFIC transformers are critical radio frequency integrated circuits (RFICs) components that are used to do voltage transformation, signal coupling, and impedance matching, etc. Current RFIC on-chip transformers are based on planar spiral inductors which are fabricated by standard two-dimensional (2D) planar fabrication process. Limitations of planar spiral inductors, such as large footprint and serious substrate parasitic effects, 1 are carried over to the transformer's primary/secondary windings.