Tunable Active Inductors for High-Frequency Applications

Tunable active inductors are employed for several applications in signal conditioning systems. In this contribution, two gyrator-based active inductors to shift the resonance frequency of notch-filter structures by means of external voltage settings are proposed. The analytical study of a new active inductor, less parameter-dependent than those found in the literature, is presented. Two resulting active inductors are inserted in series L-C structures in order to design two notch filters. The first filter has a 0.91x0.91 mm2 chip area occupation and a frequency band of 1.2 GHz centered at 16 GHz, scanned by 6 channels of 200 MHz each. The second filter, composed by an extended active inductor version, reaches K-Band and scans 8 40-MHz-wide channels around 21 GHz. The die occupies an area of 1.17x0.87 mm2