MONOLITHIC NARROW-BAND-FILTER USING ULTRAHIGH-Q TUNABLE ACTIVE INDUCTORS

A tunable active inductor is presented where the novel topology enable s both the inductance and series resistance to be varied. With a discr ete MMIC realization of this active inductor, Q-factors in excess of 1 5 000 have been measured over a wide range of inductance values. Appli cations for these active inductors include high-performance narrow-ban d filters, voltage controlled oscillators, and analog phase shifters. Analytical equations for the novel active inductor and a 3-resonator f ilter are given. The measured performance for a monolithic 2 GHz filte r achieves a mean insertion loss of 0.9 dB, passband ripple of +/-0.7 dB, with a 3 dB bandwidth of 70 MHz, and an excellent out-of-band reje ction which exceeds 50 dB up to 18 GHz.