STABILIZED MICROWAVE-FREQUENCY SOURCE

摘要

A microwave-frequency source at frequency fM comprises: a dual optical-frequency reference source, an electro-optic sideband generator, an optical bandpass filter, an optical detector, a reference oscillator, an electrical circuit, and a voltage-controlled oscillator (VCO). The sideband generator modulates dual optical reference signals at v2 and v1 to generate sideband signals at v1±n1fM and v2±n2fM. The bandpass filter transmits sideband signals at v1+N1fM and v2−N2fM. The optical detector generates a beat note at (v2−N2fM)−(v1+N1fM). The beat note and a reference oscillator signal are processed by the circuit to generate a loop-filtered error signal to input to the VCO. Output of the VCO at fM drives the sideband generator and forms the microwave-frequency output signal. The resultant frequency division results in reduced phase noise on the microwave-frequency signal.

主权项

1. A microwave-frequency source for generating an output electrical signal at an output frequency fM, the microwave-frequency source comprising:
(a) a dual optical-frequency reference source arranged so as to generate (i) a first optical reference signal at a first optical reference frequency v1 and (ii) a second optical reference signal at a second optical reference frequency v2>v1; (b) an electro-optic sideband generator arranged so as to (i) receive the first and second optical reference signals and a sideband generator input electrical signal at the frequency fM and (ii) generate therefrom multiple sideband optical signals at respective sideband optical frequencies of the form v1±n1fM and v2±n2fM, wherein n1 and n2 are integers; (c) an optical bandpass filter arranged so as to transmit a subset of the multiple sideband optical signals including the sideband optical signal at a frequency v1+N1fM and the sideband optical signal at a frequency v2−N2fM, wherein N1 and N2 are integers; (d) an optical detector arranged so as to (i) receive the transmitted sideband optical signals and (ii) generate an optical detector electrical signal at a beat frequency fBEAT=(v2−N2fM)−(v1+N1fM); (e) a reference oscillator arranged so as to generate a reference oscillator electrical signal at a reference oscillator frequency fR; (f) an electrical circuit arranged so as to (i) receive the optical detector electrical signal and the reference oscillator electrical signal, (ii) generate therefrom, using a comparator portion of the electrical circuit, an electrical error signal dependent on relative phase of the optical detector and reference oscillator electrical signals, and (iii) process the electrical error signal using a loop-filter portion of the electrical circuit; and (g) a voltage-controlled electrical oscillator arranged so as to (i) receive the loop-filtered electrical error signal as a VCO input electrical signal and (ii) generate a VCO output electrical signal at the frequency fM, wherein a first portion of the VCO output electrical signal is received by the electro-optic sideband generator as the sideband generator input electrical signal and a second portion of the VCO output electrical signal forms the output electrical signal of the microwave-frequency source, (h) wherein reception of the first portion of the VCO output electrical signal by the electro-optic sideband generator as the sideband generator input electrical signal results in the electrical circuit and the voltage-controlled oscillator being coupled in a negative feedback arrangement so as to function as a phase-locked loop.