Class-C architecture for cross-coupled FBAR oscillator to further improve phase noise

Abstract

In this letter, a class-C architecture for an oscillator employing film bulk acoustic resonator (FBAR) is presented to improve the phase noise significantly in 1/f³ region. The advantages offers by class-C operation are exploited in order to reduce the noise contributed by the current-source transistor in cross-coupled topology. An adaptive biasing circuit is used in order to ensure the oscillation start-up. The post-layout simulation incorporating all parasitic and representing FBAR by modified Butterworth Van Dyke (MBVD) model illustrates the phase noise improvement by 17 dBc/Hz at 100 kHz offset of a 1.9 GHz carrier compared to the FBAR based cross-coupled topology presented by the authors [1].