ABSTRACT
Passive components (e.g., resistors, capacitors, inductors, and transformers) and passive devices (e.g.,
varactors, Schottky diodes, and pin diodes) are integral parts of the functioning and performance of
radio-frequency (RF) building blocks [1]. They are used for impedance matching and transformation, in
filters, in resonators, in delay lines and baluns, and for many other purposes. In RF front-end circuits
they often outnumber the active device count. Unlike in the past, bipolar/BiCMOS and CMOS
technologies for communications are limited today to a large extent by the quality and cost of those
passive components and devices. Modern wireless communication products increasingly contain inte-
grated passives, i.e., passive components that are engineered by exploiting the structures and materials of
the device integration process itself. This is in contrast to the hybrid RF systems that have been used in
RF communications for a long time. The reason behind the trend toward integration is not only cost
reduction but also the small inductance (0.5 to 10 nH) and capacitance (100 to 1 pF) values needed in
the current RF circuits operating at >>1 GHz. The parasitic inductances, capacitances, and resistances of
the interconnects are then becoming comparable in value to those of the passive component itself, thus
generally lowering the quality of that component. Also, such interconnects with all associated parasitics
have to be carefully considered in the circuit design making that task extremely difficult. Placement of
passive components off chip into the package or onto the printed circuit board (PCB) as a coplanar
waveguide (CPW), a microstrip, or a discrete element is no longer an option as RFs are >1 GHz.
