Integrated RF passive components - discrete vs. distributed

Passive components have been recognized as performance as well as cost limiting elements of integrated radio-frequency (RF) systems. While the integration of high-quality capacitors at small area appears feasible, those requirements are not easily met for inductors. The frequency range, at which discrete spiral inductors can efficiently be used, is limited at around 1 GHz by size and at about 15 GHz by the controllable minimum inductance value. Distributed networks on silicon substrates appear feasible for frequencies above 35 GHz, at which the length of a /spl lambda//4-transmission line becomes smaller than 1 mm. In the intermediate frequency range from 15 GHz to 35 GHz neither discretes nor distributed elements can easily be applied. Here, periodic structures, consisting of discrete components and transmission line sections and operating in slow-wave mode, can provide practical solutions.