Feed-back and feed-forward systems and methods to reduce oscillator phase-noise

Abstract

Systems, methods, and apparatus are described that provide for low phase-noise, spectrally-pure, and low-jitter signals from electrical oscillators. An aspect of the present disclosure includes utilization of an open-loop feed-forward phase-noise cancellation scheme to cancel phase noise, or jitter, of an electrical oscillator. Phase noise can be measured and then subtracted, with the phase noise measurement and subtraction being performed at a speed faster than phase noise variations of the oscillator. Another aspect of the present disclosure includes use of a feedback scheme for phase noise reduction. A feedback scheme can be used alone or in conjunction with a feed-forward scheme. Related phase-noise cancellation and/or reduction methods are described. Notch filter and RF amplifier circuits are also described.

1 . A notch filter and RF amplifier stage comprising:
 a band-pass sub-circuit including a resonator, wherein the band-pass circuit is operative to receive an input signal from an oscillator and a feedback signal from an all-pass sub-circuit;   an all-pass sub-circuit configured to receive a control signal from an amplitude control loop and operative to receive an input signal from an RF amplifier and provide an output signal to the band-pass sub-circuit; and   an RF amplifier configured for common-mode and differential operation, wherein the RF amplifier is connected to the band-pass sub-circuit and the all-pass sub-circuit, and wherein the stage is connected to ground by a common-mode trap including first and second capacitors in parallel that are connected in series to an inductor, wherein the inductor resonates with the first and second capacitors during common-mode operation of the RF amplifier and acts a virtual ground during differential mode operation of the RF amplifier, and wherein the RF amplifier is operative to receive an input signal from the band-pass sub-circuit, amplify the signal, and provide an ouput signal to the all-pass sub-circuit.   
     
     
         2 . The notch filter and RF amplifier stage of  claim 1 , wherein the resonator is a film bulk acoustic resonator. 
     
     
         3 . A frequency discriminator circuit comprising:
 a notch filter and a RF amplifier stage operative to receive an input signal from an oscillator, and including,
 a band-pass sub-circuit including a resonator, wherein the band-pass circuit is operative to receive an input signal from an oscillator and a feedback signal from an all-pass sub-circuit; 
 an all-pass sub-circuit configured to receive a control signal from an amplitude control loop and operative to receive an input signal from an RF amplifier and provide an output signal to the band-pass sub-circuit; and 
 an RF amplifier configured for common-mode and differential operation, wherein the RF amplifier is connected to the band-pass sub-circuit and the all-pass sub-circuit, and wherein the stage is connected to ground by a common-mode trap including first and second capacitors in parallel that are connected in series to an inductor, wherein the inductor resonates with the first and second capacitors during common-mode operation of the RF amplifier and acts a virtual ground during differential mode operation of the RF amplifier, and wherein the RF amplifier is operative to receive an input signal from the band-pass sub-circuit, amplify the signal, and provide an ouput signal to the all-pass sub-circuit; 
   a phase shifter operative to receive an input signal from the oscillator and a phase shift control signal, and wherein the phase shifter is operative to impart a phase shift to the input signal based on the phase shift control signal and produce an output signal; and   a mixer receiving the output signal from the phase shifter and the output signal of the RF amplifier, and operative to produce an output signal based on a frequency of the output signal of the RF amplifier.   
     
     
         4 . The frequency discriminator circuit of  claim 3 , further comprising a feedback loop from the mixer to the phase shifter, wherein the feedback loop comprises a base-band amplifier connected to a low-pass filter that is connected to a second phase shifter that is connected to a variable delay line, wherein the base-band amplifier is operative to receive an input signal from the mixer and provide an output signal, wherein the low-pass filter is operative to receive an input signal from the base-band amplifier and provide an output signal, wherein the second phase shifter is operative to receive an input signal from the low-pass filter and to produce an output signal, wherein the variable delay line is operable to receive an input signal from the second phase shifter and provide as an output the phase shift control signal to the phase shifter. 
     
     
         5 . The frequency discriminator circuit of  claims 4 , wherein the second phase shifter comprises a voltage-controller phase shifter.