US 12,596,019 B1Granted

RF spectrum analyzer using Rayleigh backscattering

AssigneeThe Government of the United States of America, as represented by the Secretary of the Navy

InventorsMatthew J. Murray, Joseph B. Murray, Ross T. Schermer, Jason McKinney, Brandon F. Redding

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Abstract

An apparatus receives a radio frequency (“RF”) signal. The apparatus includes a first modulator encoding the RF signal on an optical carrier. The optical carrier includes a plurality of sidebands. The apparatus includes a filter operably coupled to the first modulator and passing therethrough an isolated sideband of the plurality of sidebands. The apparatus includes a Rayleigh-backscattering (“RBS”) speckle spectrometer. The RBS speckle spectrometer includes a second modulator receiving the isolated sideband and modulating the isolated sideband into alternating short and long, interrogation pulses. The RF speckle spectrometer generates a first collected signal based on Raleigh backscattered light in a first polarization and a second collected signal based on Raleigh backscattered light in a second polarization. The apparatus includes a processor receiving the first collected signal and the second collected signal, and recovering therefrom the RF spectrum of the RF signal.

Claims14

Dependent claims

An apparatus comprising:

a radio frequency (“RF”) spectrum analyzer receiving an RF signal, the RF signal comprising an RF spectrum, said RF spectrum analyzer comprising:
a first modulator encoding the RF signal on an optical carrier, the optical carrier comprising a plurality of sidebands;
and
a filter operably coupled with said first modulator and passing therethrough an isolated sideband of the plurality of sidebands;
a Rayleigh-backscatter speckle spectrometer comprising:
a second modulator receiving the isolated sideband and modulating the isolated sideband into alternating short and long;
interrogation pulses;
a first amplifier amplifying the modulated, isolated sideband;
an optical fiber receiving the amplified, modulated, isolated sideband, said optical fiber outputting Rayleigh backscattered light propagating through the fiber in a direction opposite to that of the amplified, modulated, isolated sideband;
a first photodetector operably coupled to said optical fiber and collecting therefrom the Raleigh backscattered light in a first polarization, said first photodetector generating a first collected signal;
and
a second photodetector operably coupled to said optical fiber and collecting therefrom the Raleigh backscattered light in a second polarization, said second photodetector generating a second collected signal;
and
a processor receiving the first collected signal and the second collected signal, and recovering therefrom the RF spectrum.

11 more elements

A method comprising:

providing a radio frequency (“RF”) spectrum analyzer receiving an RF signal, the RF signal comprising at least one RF tone and an RF spectrum, the RF spectrum including an RF frequency range, the RF spectrum analyzer comprising:
a Rayleigh-backscatter speckle spectrometer;
and
a processor communicating with the Rayleigh-backscatter speckle spectrometer and recovering the RF spectrum;
initializing the RF spectrum analyzer by measuring a plurality of initial speckle intensity patterns across the RF frequency range;
measuring a calibration speckle intensity pattern generated by a single calibration frequency in the RF spectrum, using the processor;
comparing the calibration speckle intensity pattern to the plurality of initial speckle intensity patterns to determine an optical frequency shift, using the processor;
and
recalibrating the RF spectrum analyzer by shifting the recovered RF spectrum by a frequency equal to the optical frequency shift, using the processor.

6 more elements

A method comprising:

providing a radio frequency (“RF”) spectrum analyzer receiving simultaneously an RF signal and a calibration signal, the RF signal comprising at least one RF tone and an RF spectrum, the RF spectrum including an RF frequency range, the calibration signal comprising a single calibration frequency, the RF spectrum analyzer comprising:
a Rayleigh-backscatter speckle spectrometer;
and
a processor communicating with the Rayleigh-backscatter speckle spectrometer and recovering the RF spectrum;
initializing the RF spectrum analyzer by measuring a plurality of initial speckle intensity patterns across the RF frequency range;
measuring a calibration speckle intensity pattern generated by the single calibration frequency in the RF spectrum;
comparing the calibration speckle intensity pattern to the plurality of initial speckle intensity patterns to determine an optical frequency shift;
and
recalibrating the RF spectrum analyzer by shifting the recovered RF spectrum to compensate for the optical frequency shift, using the processor.

6 more elements

Dependencies are inferred from the claim text.

Facts

Application: 18/603,585Filed 13 Mar 2024 · us provisional application
Priority: 15 Mar 2023
Granted: 7 Apr 2026
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

G01D 3/08
Indicating or recording apparatus with provision for the special purposes referred to in the subgroups: with provision for safeguarding the…
G01D 5/35361
Using backscattering to detect the measured quantity: using elastic backscattering to detect the measured quantity, e.g. using Rayleigh backscattering
G01J 3/0218
Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows: using optical fibers
G01J 3/1895
Using diffraction elements, e.g. grating: using fiber Bragg gratings or gratings integrated in a waveguide