MEASURING PHASE NOISE IN RADIO FREQUENCY, MICROWAVE OR MILLIMETER SIGNALS BASED ON PHOTONIC DELAY

• US 20120195590A1
• Filed: 04/09/2012
• Published: 08/02/2012
• Est. Priority Date: 11/13/2007
• Status: Active Grant

• Current Assignee: Oewaves Incorporated
• Original Assignee: Oewaves Incorporated
• Inventors: Eliyahu, Danny, Maleki, Lute, Seidel, David
• Granted Patent: US 9,234,937 B2
• Time in Patent Office: Days
• US Class Current: 398/26
• CPC Class Codes: G01R 29/26 Measuring noise figure; Measuring signal-to-noise ratio
• CPC Class Codes: G01R 31/2824 testing of oscillators or resonators
• CPC Class Codes: H04B 10/61 Coherent receivers

Abstract

Techniques and devices for measuring phase noise in radio frequency (RF), microwave, or millimeter signals based on photonic delay.

Claims

1. A device for measuring a phase noise in a signal, comprising:

an input port that receives an oscillation signal from an oscillator under test;

a photonic signal processing circuit that processes the oscillation signal to produce an output signal; and

circuitry that receives and processes the output signal to measure noise in the received oscillation signal and controls the photonic signal processing circuit and measurements of the noise in the received oscillation signal,

wherein the photonic signal processing circuit includes a laser producing continuous wave laser light in a first optical polarization, an optical modulator that modulates the laser light to produce modulated laser light that carries the oscillation signal and is in the first optical polarization, a photonic beam combiner that receives at a first port the modulated laser light in the first optical polarization along a first optical path from the optical modulator, directs the received modulated laser light in the first optical polarization to a second port and directs light received at the second port in a second optical polarization orthogonal to the first optical polarization to a third port, a fiber delay line coupled to the second port to receive light from the photonic beam combiner, a Faraday rotator mirror coupled to the fiber delay line to reflect light back to the fiber delay line by rotating optical polarization by 90 degrees, a photodetector coupled to receive light from the third port of the photonic beam combiner to generate a detector signal, a voltage controlled phase shifter that receives a copy of the oscillation signal and changes a phase of the copy of the oscillator signal to produce a phase-shifted oscillator signal, and a signal mixer that mixes the detector signal and the phase-shifted oscillator signal to produce the output signal.

2. The device as in claim 1, comprising:

a polarization maintaining fiber that connects the optical modulator and the first port of the photonic beam combiner to maintain light in the first optical polarization.

3. The device as in claim 1, comprising:

an optical switch coupled between the fiber delay line and the Faraday rotator mirror to connect or disconnect a connection between the fiber delay line and the Faraday rotator mirror;

a second fiber delay line separated from the first fiber delay line; and

a second Faraday rotator mirror coupled to the second fiber delay line to receive light from the second fiber delay line and to reflect light back to the second fiber delay line by rotating optical polarization by 90 degrees,

wherein the optical switch is further coupled between the fiber delay line and the second fiber delay line to connect or disconnect a connection between the fiber delay line and the second fiber delay line.

4. The device as in claim 1, wherein the circuitry includes:

a signal analyzer that receives and processes the output signal to measure noise in the received oscillation signal; and

a controller that controls the first photonic signal processing circuit and the signal analyzer to control measurements of the noise in the received oscillation signal.

5. A device for measuring a phase noise in a signal, comprising:

an input port that receives an oscillation signal from an oscillator under test;

a first laser producing a first continuous wave laser beam in a first optical polarization;

a first optical modulator that modulates the first laser beam to produce a first modulated laser light that carries the oscillation signal;

a first optical circulator having a first port that receives the first modulated laser light in the first optical polarization and a second port that outputs light from the first port and a third port that outputs light received at the second port;

a second laser producing a second continuous wave laser beam in a second optical polarization orthogonal to the first optical polarization;

a second optical modulator that modulates the second laser beam to produce a second modulated laser light that carries the oscillation signal;

a second optical circulator having a first port that receives the second modulated laser light in the second optical polarization and a second port that outputs light from the first port and a third port that outputs light received at the second port;

a photonic beam combiner that includes a first port, a second port and a third port, the first port being coupled to the second port of the first optical circulator to receive the first modulated laser light in the first optical polarization which is directed to the second port of the photonic beam combiner, wherein the photonic beam combiner directs light received at the second port in the second optical polarization to the third port and directs light received at the second port in the second optical polarization to the first port, and wherein the third port of the photonic beam combiner is coupled to receive light of the second modulated laser beam in the second polarization from the second port of the second optical circulator;

a fiber delay line coupled to the second port of the photonic beam combiner to receive light from the photonic beam combiner to introduce a phase delay in both the first and second modulated laser beams;

a Faraday rotator mirror coupled to the fiber delay line to reflect light back to the fiber delay line by rotating optical polarization by 90 degrees;

a first photodetector coupled to receive light from the third port of the second optical circulator to generate a first detector signal;

a second photodetector coupled to receive light from the third port of the first optical circulator to generate a second detector signal;

a first voltage controlled phase shifter that receives a copy of the oscillation signal and changes a phase of the copy of the oscillator signal to produce a first phase-shifted oscillator signal;

a first signal mixer that mixes the first detector signal and the first phase-shifted oscillator signal to produce a first output signal;

a second voltage controlled phase shifter that receives another copy of the oscillation signal and changes a phase of the other copy of the oscillator signal to produce a second phase-shifted oscillator signal;

a second signal mixer that mixes the second detector signal and the second phase-shifted oscillator signal to produce a second output signal; and

circuitry that receives the first and second output signals to measure noise in the received oscillation signal, and controls the first and second voltage controlled phase shifters and measurements of the noise in the received oscillation signal.

6. The device as in claim 5, comprising:

a first polarization maintaining fiber that connects the first optical circulator and the first port of the photonic beam combiner to maintain light in the first optical polarization; and

a second polarization maintaining fiber that connects the second optical circulator and the third port of the photonic beam combiner to maintain light in the second optical polarization.

7. The device as in claim 5, comprising:

an optical switch coupled between the fiber delay line and the Faraday rotator mirror to connect or disconnect a connection between the fiber delay line and the Faraday rotator mirror;

a second fiber delay line separated from the first fiber delay line; and

a second Faraday rotator mirror coupled to the second fiber delay line to receive light from the second fiber delay line and to reflect light back to the second fiber delay line by rotating optical polarization by 90 degrees,

wherein the optical switch is further coupled between the fiber delay line and the second fiber delay line to connect or disconnect a connection between the fiber delay line and the second fiber delay line.

8. The device as in claim 5, wherein the circuitry includes:

a signal analyzer that receives the first and second output signals to measure noise in the received oscillation signal; and

a controller that controls the first and second voltage controlled phase shifters and the signal analyzer to control measurements of the noise in the received oscillation signal.

9. A method for measuring a phase noise in a signal in a radio frequency (RF), microwave or millimeter frequency range, comprising:

splitting an initial input signal in a radio frequency (RF), microwave or millimeter frequency range into, at minimum, a first signal and a second signal;

applying a variable phase shift to the first signal to produce a first phase shifted signal;

applying the second signal as a modulation control signal to module one or more laser beams to produce one or more modulated laser beams that carry the second signal;

causing an optical delay in each of the one or more modulated laser beams that carry the second signal to produce a delayed modulated laser beam;

directing each delayed modulated laser beam into a photodetector to produce a detector output signal representing the respective delayed modulated laser beam;

mixing the photodetector output signal and the first phase shifted signal to produce a mixture signal; and

processing the mixture signal to obtain information on phase noise in the initial input signal.