A 220dB FOM, 1.9GHz oscillator using a phase noise reduction technique for high-Q oscillators

We present a technique to reduce the close-in phase noise of high-Q (FBAR/MEMS/crystal) oscillators. The proposed technique suppresses the up-conversion of 1/f noise via AM-PM conversion by the addition of a non-linear capacitor to the tank. The proposed AM-PM suppression technique has no additional power penalty and incurs a minimal area penalty. Measurements from multiple dies of a 1.9GHZ FBAR oscillator show ≥3.5dB reduction in close-in phase noise using the proposed technique. The FBAR oscillator achieves a measured phase noise of -88dBc/Hz @ 1kHz, -116dBc/Hz @ 10kHz, -146dBc/Hz @ 1MHz offsets. The oscillator with the proposed technique achieves a Figure of Merit (FOM) of 220dB, which is 5.5dB better than the FBAR oscillator with lowest close-in phase noise reported to date [1].