Offset-mixer interferometric noise suppressed oscillator (INSO)

An offset-mixer interferometric noise suppressed oscillator (INSO), comprising:

• an amplifier, a loop phase shifter responsive to a control signal, and a resonator arranged in a loop to oscillate and produce a first signal at a carrier frequency, a second signal produced by reflection of a portion of the first signal by the resonator;
• an interferometric bridge including a reference arm responsive to a first portion of the first signal and a reflection arm responsive to a portion of the second signal which combine to produce a carrier suppressed signal, said reference arm having a carrier phase and amplitude and said reflection arm having a carrier phase and amplitude, and a low noise amplifier (LNA) configured to amplify the carrier suppressed signal;
• a LO variable phase shifter responsive to a second portion of the first signal to produce a phase-shifted LO signal;
• an I/Q mixer responsive to the amplified carrier suppressed signal and the phase-shifted LO signal to produce I and Q channel outputs as amplitude and phase error signals, respectively, of the reflection arm, wherein the LO variable phase shifter is tuned to align the Q-channel output to the reflection arm's carrier phase and the I-channel output to the reflection arm's carrier amplitude;
• said reference arm including a fixed phase shifter and a variable phase shifter, wherein the fixed phase shifter provides a phase shift to align the reference arm's variable phase shifter to the I-channel output, wherein the variable phase shifter is responsive to the I-channel output to nullify the I-channel output;
• and
• a control signal generator including an amplification network that amplifies a difference signal between Q-channel output and an externally applied carrier frequency tuning voltage VPLL that imposes a non-zero offset on the mixer's Q-channel output to provide the control signal to the loop phase shifter to adjust the carrier frequency thereby producing a different reflection phase that appears on the Q-channel output to drive the difference signal towards zero,
• wherein the mixer, reference arm variable phase shifter and LNA each have a phase noise contribution, wherein the reference arm's variable phase shifter is aligned with the I-channel and off-axis to the INSO's phase noise in the Q-channel such that its phase noise contribution is less than the mixer's, wherein the carrier suppressed signal is offset from zero thereby increasing a phase noise contribution of the LNA, which remains less than the phase noise contribution of the mixer, whereby the mixer's phase noise contribution is the dominant phase noise contributor for the INSO.

An offset-mixer interferometric noise suppressed oscillator (INSO), comprising:

• an oscillator loop that produces a first signal at a carrier frequency and a second signal as a reflection of the first signal;
• a phase detector including an interferometric bridge having reference and reflection arms responsive to the first and second signals, respectively, and combines them to produce a carrier suppressed signal, a LO variable phase shifter responsive to the first signal to produce a phase-shifted LO signal, and an I/Q mixer responsive to the carrier suppressed signal and the phase-shifted LO signal to generate I and Q-output channels;
• a fixed phase shift that aligns a variable phase shifter in the reference arm to the mixer's I-channel output, said variable phase shifter responsive to the I-channel output to nullify the I-channel output;
• and
• an amplification network responsive to a difference signal between the mixer's Q-channel output and an externally applied carrier frequency tuning voltage VPLL to provide a control signal to the oscillator loop to adjust the carrier frequency, wherein VPLL imposes a non-zero offset on the Q-channel output.