A 3 GHz silicon-BJT active resonator and filter

A tunable active resonator for filtering applications is presented in this paper. The resonator consists of a fully differential high-Q active inductor with resonating passive capacitors. The realisation of the active inductor has no critical passive components, which reduces size and sensitivity, and extends the number of possible process technologies. On the other hand, the inherently poor noise properties of active inductors are discussed. The tuning range of the resonator is 2.5-3 GHz with freely adjustable quality factor. A second-order filter with the same tuning range and -3 dB bandwidth of 50 MHz is also described.