The First Active Tunable Wideband Impedance Matching Circuit

The first transistor-based impedance matching circuit for radio-frequency (RF) applications is introduced in this paper. It adapts arbitrary output impedances of RF blocks to desired values between 50ohmand 250ohm, from 0 to 5GHz, while occupying only 0.005mm² of circuit area in a 0.35μm SiGe BiCMOS process. Its superiority over traditional passive-element networks can be resumed by the following facts: flexible performance without the need for redesigning the components; adaptation of arbitrary impedances to desired values by the simple means of biasing current; extremely small form factors (the smallest observed); and matching over several gigahertz. Application to a low-noise amplifier validates the new topology.