A 5 GHz above-IC FBAR low phase noise balanced oscillator

In this paper, a 5 GHz FBAR based balanced oscillator is presented. The FBAR resonator was integrated directly above the 0.35 mum BiCMOS IC oscillator. The use of the balanced configuration allows dividing by two the electrodes resistance of the FBAR. Therefore, better phase noise is obtained comparatively to the single ended version. The measured phase noise is -121 dBc/Hz at 100 kHz from 5.46 GHz carrier frequency. Furthermore, the differential output allows direct driving of the divider and mixer, which are generally balanced, without the need of a single-ended to differential converter