Reconfigurable optical beamformer for simplified time steered arrays

• US 20020181874A1
• Filed: 05/29/2002
• Published: 12/05/2002
• Est. Priority Date: 05/29/2001
• Status: Active Grant

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Matthews, Paul J., Tulchinsky, David A.
• Granted Patent: US 6,807,343 B2
• Time in Patent Office: Days
• US Class Current: 385/39
• CPC Class Codes: G02B 6/2861 using fibre optic delay lines and optical elements associated with them, e.g. for use in signal processing, e.g. filtering delay lines in general H03H, H01P9/00; optical computing devices G06E
• CPC Class Codes: H01Q 3/2676 Optically controlled phased array

Abstract

An array antenna apparatus for producing a time-delay beamformed RF signal includes a laser, a modulator for RF modulating the laser optical signal, a first plurality of optical paths coupling the modulator output to a dispersive prism, another plurality of optical paths coupling the dispersive prism outputs to a corresponding plurality of time delay trimmers, an attenuator coupled to each time delay trimmer, and an optical switching matrix to which the time delay trimmers outputs are input. The inputs to the optical switching matrix accordingly are time and amplitude adjusted to remove front end errors prior to rerouting. This is repeated in the back end of the apparatus, in which the switching matrix outputs are each applied to a corresponding attenuator, the outputs of which are then each applied to a photodetector to generate a plurality of replica RF signals that are each applied to a time shifter, thereby producing an error-corrected output that is then applied to an antenna array. The output of the antenna array is a time-delay beamformed RF signal having a 2-D beamsteering capability.

Claims

1. An optical beamformer, comprising:

a laser for generating an optical signal;

a modulator having a first input for receiving the optical signal, a second input for receiving an RF input signal, and an output for applying a modulated optical signal;

a first plurality of optical paths, each said optical path of said first plurality of optical paths having an input coupled to the modulator output and an output;

a dispersive prism having a plurality of inputs, each said prism input coupled to a corresponding optical path output of said first plurality of optical paths, and a plurality of corresponding outputs;

a second plurality of optical paths, each said optical path of said second plurality of optical paths having an input coupled to a dispersive prism output and having an output;

a plurality of time delay trimmers, each having an input coupled to a corresponding output of an optical path of said second plurality of optical paths and an output;

a first plurality of attenuators, each having an input coupled to a corresponding time delay trimmer output, and an output;

an optical switching matrix having a plurality of inputs, each coupled to a corresponding attenuator output, and having a plurality of reroutable outputs;

a second plurality of attenuators, each having an input coupled to a corresponding reroutable output, and having a corresponding plurality of outputs;

a plurality of photodetectors each having an input coupled to a corresponding output of an attenuator of said second plurality of attenuators and an output for applying a replica RF signal; and

a plurality of time shifters, each having an input coupled to a corresponding photodetector output and an output for applying a plurality of time shifted RF signals.

2. An optical beamformer as in claim 1, further comprising a first amplifier coupled between the laser and the first input of the modulator for amplifying the optical signal applied to the modulator.

3. An optical beamformer as in claim 1, further comprising a plurality of RF amplifiers, each having an input coupled to a corresponding photodetector output and an output coupled to a corresponding input of a time shifter to thereby amplify the replica RF signals applied to the time shifters.

4. An optical beamformer as in claim 1, wherein said laser is a wavelength tunable semiconductor laser.

5. An optical beamformer as in claim 1, further comprising a second, optical amplifier coupling the modulator and the dispersive prism for amplifying the modulated optical signal.

6. An optical beamformer as in claim 1, wherein the dispersive prism is high dispersion optical fiber.

7. An optical beamformer as in claim 1, wherein the dispersive prism comprises Bragg gratings and optical circulators.

8. An array antenna apparatus for producing a time-delay beamformed RF signal, comprising:

a laser for generating an optical signal;

a modulator having a first input for receiving the optical signal, a second input for receiving an RF input signal, and an output for applying a modulated optical signal;

a first plurality of optical paths, each said optical path of said first plurality of optical paths having an input coupled to the modulator output and an output;

a dispersive prism having a plurality of inputs, each said prism input coupled to a corresponding optical path output of said first plurality of optical paths, and a plurality of corresponding outputs;

a second plurality of optical paths, each said optical path of said second plurality of optical paths having an input coupled to a dispersive prism output and having an output;

a plurality of time delay trimmers, each having an input coupled to a corresponding output of an optical path of said second plurality of optical paths and an output;

a first plurality of attenuators, each having an input coupled to a corresponding time delay trimmer output, and an output;

an optical switching matrix having a plurality of inputs, each coupled to a corresponding attenuator output, and having a plurality of reroutable outputs;

a second plurality of attenuators, each having an input coupled to a corresponding reroutable output, and having a corresponding plurality of outputs;

a plurality of photodetectors each having an input coupled to a corresponding output of an attenuator of said second plurality of attenuators and an output for applying a replica RF signal;

a plurality of time shifters, each having an input coupled to a corresponding photodetector output and an output for applying a plurality of time shifted RF signals; and

an antenna array having a plurality of inputs for receiving each of said time shifted RF signals and an output for applying a time-delay beamformed RF signal.

9. An array antenna apparatus as in claim 8, further comprising a first amplifier coupled between the laser and the first input of the modulator for amplifying the optical signal applied to the modulator.

10. An array antenna apparatus as in claim 8, further comprising a plurality of RF amplifiers, each having an input coupled to a corresponding photodetector output and an output coupled to a corresponding input of a time shifter to thereby amplify the replica RF signals applied to the time shifters.

11. An array antenna apparatus as in claim 8, wherein said laser is a wavelength tunable semiconductor laser.

12. An array antenna apparatus as in claim 8, further comprising a second, optical amplifier coupling the modulator and the dispersive prism for amplifying the modulated optical signal.

13. An array antenna apparatus as in claim 8, wherein the dispersive prism is high dispersion optical fiber.

14. An array antenna apparatus as in claim 8, wherein the dispersive prism comprises Bragg gratings and optical circulators.

16. An array antenna apparatus as in claim 15, further comprising means for amplifying said optical signal;

17. An array antenna apparatus as in claim 15, further comprising means for amplifying said plurality of replica RF output signals;

18. An array antenna apparatus as in claim 15, wherein said means for generating an optical signal is a wavelength tunable semiconductor laser.

19. An array antenna apparatus as in claim 15, further comprising means for amplifying a modulated optical signal received from the means for RF modulating having an output coupled to an input of the means for receiving said outputs of said first plurality of optical paths and for introducing a time delay gradient thereto.

20. An array antenna apparatus as in claim 15, wherein the means for receiving said outputs of said first plurality of optical paths and for introducing a time delay gradient thereto is high dispersion optical fiber.

21. An array antenna apparatus as in claim 15, wherein the means for receiving said outputs of said first plurality of optical paths and for introducing a time delay gradient thereto comprises Bragg gratings and optical circulators.

15. An array antenna apparatus for producing a time-delay beamformed RF signal, comprising:

means for generating an optical signal;

means for RF modulating said amplified optical signal and for applying a modulated optical signal output;

first means for dividing said modulated optical signal into a first plurality of optical paths each having an output;

means for receiving said outputs of said first plurality of optical paths and for introducing a time delay gradient thereto at a corresponding plurality of outputs;

second means for dividing each of said plurality of time delay gradient-introduced outputs into a second plurality of optical paths each having an output;

means for trimming each said second plurality of optical paths output to produce a plurality of error-corrected outputs;

first means for attenuating each of said error-corrected outputs;

means for rerouting said error-corrected outputs to form a 2-D steered output;

second means for attenuating said 2-D steered optical output;

means for converting said 2-D steered optical output into a plurality of replica RF signals;

means for time-shifting said amplified plurality of replica RF output signals; and

means for receiving said time-shifted, amplified plurality of replica RF output signals and for applying a time-delay beamformed RF signal.