Fiber optic true time-delay array antenna feed system

• US 6,337,660 B1
• Filed: 09/17/1993
• Issued: 01/08/2002
• Est. Priority Date: 09/17/1993
• Status: Expired due to Fees

• Current Assignee: The Government Of The United States As Represented By The Secretary Of The Navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Goldberg, Lew, Esman, Ronald D.
• Primary Examiner(s): PHAN, DAO LINDA
• Application Number:
  US08/122,671
• Time in Patent Office: 3,035 Days
• Field of Search: 342/375, 342/157, 342/81, 342/154, 342/54
• US Class Current: 342/375
• 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
• CPC Class Codes: H01Q 3/2682 Time delay steered arrays

Abstract

The fiber-optic true time-delay array antenna feed is a device for dynamically generating a plurality of identical electromagnetic radiation (EMR) signals with continuously variable time-delay separations. The EMR signal to be transmitted modulates a continuous-wave optical signal from a laser source which is applied to a plurality of high dispersion single-mode optical fibers acting as synchronized true time-delay modulators forming an array antenna feed system. Each fiber is chosen to have the same nominal time delay but a different net dispersion. Photodetectors convert the optical intensity back into an EMR electrical signal to feed each of the elements of the array antenna.

Claims

1. A fiber optic true time-delay array antenna feed system comprising:

means for generating at least one modulated optical signal having at least one wavelength and containing at least one modulation signal;

means for splitting the modulated optical signal into a plurality of modulated optical signals;

means for respectively propagating the plurality of modulated optical signals at a velocity dependent on the optical wavelength of each of the modulated optical signals comprising the plurality of modulated optical signals thereby producing a plurality of time delayed modulated optical signals;

means for respectively converting the plurality of time delayed modulated optical signals into a plurality of electrical signals;

means for respectively equalizing the nominal time delays of the plurality of electrical signals;

means for respectively amplifying the plurality of nominally equalized electrical signals;

means for transmitting the plurality of nominally equalized electrical signals;

means for receiving a plurality of electromagnetic signals; and

,

means for respectively amplifying, controlling and mixing the plurality of nominally equalized electrical signals with the plurality of received electromagnetic signals.

2. An antenna feed system, as in claim 1, wherein the means for generating at least one modulated optical signal is further comprised of a means for generating at least one narrow-linewidth wavelength controlled continuous-wave optical carrier;

means for controlling the wavelength of the at least one optical carrier; and

means for modulating the at least one optical carrier with at least one electrical signal to produce a modulated optical signal.

3. An antenna feed system, as in claim 2, wherein the means for generating at least one narrow-linewidth wavelength controlled continuous-wave optical carrier is comprised of a single means generating a narrow-linewidth wavelength controlled continuous-wave optical carrier.

4. An antenna feed system, as in claim 3, wherein the means for generating a continuous-wave optical carrier is a laser.

5. An antenna feed system, as in claim 4, wherein the laser is a continuously tunable laser.

6. An antenna feed system, as in claim 2, wherein the means for modulating the optical signal with an electrical signal is an external modulator.

7. An antenna feed system, as in claim 6, wherein the external modulator is an optical intensity modulator.

8. An antenna feed system, as in claim 6, wherein the external modulator is an optical frequency modulator.

9. An antenna feed system, as in claim 6, wherein the external modulator is an optical phase modulator.

10. An antenna feed system, as in claim 2, wherein the means for generating at least one narrow-linewidth wavelength controlled continuous-wave optical carrier is further comprised of a plurality of means for generating a narrow-linewidth wavelength controlled continuous-wave optical carrier, means for respectively controlling the plurality of means for generating the narrow-linewidth wavelength controlled continuous-wave optical carrier and a means for combining the plurality of narrow-linewidth wavelength controlled continuous-wave optical carriers so as to form one multiple wavelength optical carrier.

11. An antenna feed system, as in claim 2, wherein the means for modulating the optical carrier with at least one electrical signal is further comprised of a means to combine a plurality of electrical signals so as to form a composite electrical signal.

12. An antenna feed system, as in claim 11, wherein the means to combine a plurality of electrical signals so as to form a composite electrical signal is an electrical power combiner.

13. An antenna feed system, as in claim 10, wherein the means for combining the plurality of narrow-linewidth wavelength controlled continuous-wave optical carriers so as to form one multiple wavelength optical carrier is at least-one fiber optic combiner.

14. An antenna feed system, as in claim 2, wherein the means for controlling the wavelength of the at least one optical carrier is a constant voltage power supply.

15. An antenna feed system, as in claim 2, wherein the means for controlling the wavelength of the at least one optical carrier is an electrical signal generator.

16. An antenna feed system, as in claim 2, wherein the means for controlling the wavelength of the at least one optical carrier is a digital-to-analog converter.

17. An antenna feed system, as in claim 2, wherein the means for controlling the wavelength of the at least one optical carrier is an electrical circuit capable of producing complex electrical waveforms.

18. An antenna feed system, as in claim 1, wherein the means for generating at least one modulated optical signal is further comprised of a means for generating at least one narrow-linewidth wavelength controllable continuous-wave optical carrier;

means for controlling the wavelength of the at least one optical carrier;

plurality of means for modulating the plurality of optical carriers with at least one electrical signal to produce a plurality of modulated optical signals; and

a means to combine the plurality of modulated optical signals so as to form a combined modulated optical signal.

19. An antenna feed system, as in claim 18, wherein the means for generating at least one narrow-linewidth wavelength controlled continuous-wave optical carrier is comprised of a single means generating a narrow-linewidth wavelength controlled continuous-wave optical carrier.

20. An antenna feed system, as in claim 18, wherein the means for modulating the optical signal with an electrical signal is an external modulator.

21. An antenna feed system, as in claim 20, wherein the external modulator is an optical intensity modulator.

22. An antenna feed system, as in claim 20, wherein the external modulator is an optical frequency modulator.

23. An antenna feed system, as in claim 20, wherein the external modulator is an optical phase modulator.

24. An antenna feed system, as in claim 18, wherein the means to combine the plurality of modulated optical signals so as to form a combined modulated optical signal is at least one fiber optic combiner.

25. An antenna feed system, as in claim 18, wherein the means for generating at least one narrow-linewidth wavelength controlled continuous-wave optical carrier is further comprised of a plurality of means for generating a narrow-linewidth wavelength controlled continuous-wave optical carrier, means for respectively controlling the plurality of means for generating the narrow-linewidth wavelength controlled continuous-wave optical carrier and a means for combining the plurality of narrow-linewidth wavelength controlled continuous-wave optical carriers so as to form one multiple wavelength optical carrier.

26. An antenna feed system, as in claim 18, wherein the means for modulating the optical carrier with at least one electrical signal is further comprised of a means to combine a plurality of electrical signals so as to form a composite electrical signal.

27. An antenna feed system, as in claim 25, wherein the means to combine the plurality of narrow-linewidth wavelength controlled continuous-wave optical carriers so as to form one multiple wavelength optical carrier is at least one fiber optic combiner.

28. An antenna feed system as in claim 1, wherein said means for splitting the modulated optical signal into a plurality of modulated optical signals is at least one fiber-optic splitter.

29. An antenna feed system, as in claim 1, wherein each of the plurality of modulated optical signals has a time-delay differing from the time-delay of each of the other optical signals of the plurality of optical signals.

30. An antenna feed system, as in claim 1, wherein the means for respectively propagating the plurality of modulated optical signals respectively is a plurality of optical fibers.

31. An antenna feed system, as in claim 29, wherein the difference in time-delay between each of the plurality of modulated optical signals is formed by each of the plurality of optical fibers respectively propagating the plurality of modulated optical signals having a different net optical dispersion from the net optical dispersion of any other optical fiber within the plurality of optical fibers.

32. An antenna feed system, as in claim 31, wherein the net optical dispersion of each optical fiber is determined by a makeup of different lengths of dispersive and non-dispersive optical fiber calculated to provide a desired wavelength dependence of time delay in that optical fiber.

33. An antenna feed system, as in claim 1, wherein the means for respectively converting the plurality of time delayed modulated optical signals into a plurality of time-delayed electrical signals is an optical intensity sensitive photodetector.

34. An antenna feed system, as in claim 1, wherein the means for respectively converting the plurality of time delayed modulated optical signals into a plurality of time-delayed electrical signals is an optically coherent detection means for converting frequency-modulated optical signals to time-delayed electrical signals.

35. An antenna feed system, as in claim 1, wherein the means for respectively converting the plurality of time delayed modulated optical signals into a plurality of time-delayed electrical signals further comprising a means to convert frequency-modulated optical signals into intensity-modulated optical signals and an optical intensity sensitive photodetection means for converting the intensity modulated optical signals into time-delayed electrical signals.

36. An antenna feed system, as in claim 1, wherein the means for respectively converting the plurality of time delayed modulated optical signals into a plurality of time-delayed electrical signals is a means for converting phase modulated optical signals into intensity-modulated optical signals and an optical intensity sensitive photodetection means for converting the intensity modulated optical signals into time-delayed electrical signals.

37. An antenna feed system, as in claim 1, wherein each of the plurality of combined modulated optical signals has a time-delay from external modulator until conversion to time-delayed electrical signals differing from the time-delay of each of the other modulated optical signals of the plurality of combined modulated optical signals.

38. An antenna feed system, as in claim 1, wherein the means for nominally equalizing the time delay in each time-delayed electrical signal with the time delay of each of the other time-delayed electrical signals of the plurality of time-delayed electrical signals is a plurality of electromagnetic radiation line stretchers.

39. An antenna feed system, as in claim 1, wherein the means for respectively amplifying the plurality of time-delayed electrical signals is a plurality of electrical amplifiers.

40. An antenna feed system, as in claim 1, wherein the means for transmitting said plurality of time-delayed electrical signals is a plurality of elements comprising an array antenna.

41. An antenna feed system, as in claim 1, wherein the means for receiving a plurality of electromagnetic signals is a plurality of elements comprising an array antenna.

42. An antenna feed system, as in claim 1, wherein the means for mixing the equalized electrical signals with a plurality of received electrical signals is an electrical mixer.

45. An antenna feed system, as in claim 1, wherein the means for respectively amplifying, controlling and mixing the plurality of nominally equalized electrical signals is a plurality of transmit/receive modules.

43. A fiber optic true time-delay antenna feed system comprising:

an array antenna having a plurality of elements capable of generating at least one beam, each beam controllable in azimuth and elevation and any combination of the azimuth and elevation and producing desired beam shapes in transmit and receive mode and any combination of the transmit and receive mode;

means for generating a first optical carrier containing a narrow-linewidth wavelength controlled continuous-wave optical carrier of which the wavelength is used to control the elevation of the beam produced by the plurality of elements of the array antenna;

means for generating a second optical carrier containing a narrow-linewidth wavelength controlled continuous-wave optical carrier of which the wavelength is used to control the azimuth of the beam produced by the plurality of elements of the array antenna;

means for modulating said first optical carrier with an electrical signal producing a first modulated optical signal;

means for amplifying the first modulated optical signal;

means for splitting the amplified first optical signal into a first plurality of modulated optical signals;

a plurality of optical fibers for respectively propagating said first plurality of modulated optical signals comprised of, optical fibers having a different net optical dispersion from any other optical fiber within the plurality of optical fibers thereby resulting in a different time delay being applied to each of the first plurality of modulated optical signals;

means for respectively converting the plurality of first modulated optical signals into a plurality of first time-delayed electrical signals;

means for amplifying the plurality of time-delayed first electrical signals;

means for amplifying the second optical carrier;

means for splitting the amplified second optical carrier into a column (n) of amplified second optical carriers;

means for respectively modulating the column of amplified second optical carriers with the plurality of first time-delayed electrical signals producing a second plurality of modulated optical signals;

means for respectively splitting each of the plurality of second modulated optical signals into a plurality of rows (m) of modulated optical signals;

a plurality of optical fibers for respectively propagating the plurality of rows and columns of modulated optical signals;

each of said plurality of optical fibers being comprised of optical fibers having a different net optical dispersion from any other optical fiber within the row of optical fibers thereby resulting in a different time delay being applied to each of the plurality of rows and columns of modulated optical signals;

means for respectively converting the plurality of time-delayed rows and columns of modulated optical signals into a plurality of rows and columns of second time-delayed electrical signals;

means for respectively amplifying the plurality of second time-delayed electrical signals for application to the plurality of elements of the array antenna for transmission;

means for receiving a plurality of electromagnetic signals; and

,

means for mixing the plurality of time-delayed rows and columns of second time-delayed electrical signals with the plurality of received electromagnetic signals.

44. An antenna feed system, as in claim 43, wherein the difference in net optical dispersion of each optical fiber of a plurality of optical fibers is achieved by combining segments of optical fiber having different lengths of dispersive and non-dispersive optical fiber, the length of dispersive and non-dispersive optical fiber being calculated so as to provide a different time delay in the optical signal being propagated by that optical fiber that differs from the time delay of the optical signal being conducted by any other optical fiber of the plurality of optical fibers.

46. A fiber optic true time-delay finite impulse response filter comprising:

means for generating at least one narrow-linewidth wavelength-controlled continuous-wave optical carrier;

means for combining the optical carrier(s) into a combined optical carrier;

means for combining a first plurality of electrical signals into a combined electrical signal;

means for respectively modulating each of the combined optical carrier(s) with a combined electrical signal to produce a first combined modulated optical signal;

means for splitting the first combined modulated optical signal into a plurality of first combined modulated optical signals;

means for respectively propagating each of said plurality of first combined modulated optical signals at a velocity dependent on the optical wavelength of each of the plurality of first combined modulated optical signals to form a plurality of time-delayed first combined modulated optical signals;

means for combining a plurality of time-delayed first combined modulated optical signals to form a second combined modulated optical signal;

means for respectively converting the second combined modulated optical signal into a second combined electrical signal;

means for independently controlling the wavelength of the optical carriers thereby setting and varying the time delay of the electrical signals from said modulating means to said converting means; and

,

means for respectively amplifying the second combined electrical signal to produce a filtered output electrical signals.

47. A method for providing a fiber-optic true time-delay array antenna feed comprising the steps of:

generating at least one of narrow-linewidth wavelength-controlled optical carrier;

combine the narrow-linewidth wavelength-controlled optical carrier(s) into an optical signal;

modulate the optical signal with an electromagnetic radiation signal to form a modulated optical signal;

split the modulated optical signal into a plurality of modulated optical signals, each of said modulated optical signals having a time-delay differing from each other modulated optical signal of the plurality of modulated optical signals;

respectively convert the plurality of time-delayed modulated optical signals into a plurality of time-delayed electrical signals; and

apply respectively the time-delayed electrical signals to the array antenna.

48. An array antenna system having a fiber optic true time-delay array antenna feed system comprising:

a tunable light source for generating at least one modulated optical signal having at least one wavelength and containing at least one modulation signal;

means for splitting the modulated optical signal into a plurality of modulated optical signals;

a plurality of optical fibers comprised of dispersive and non-dispersive optical fibers of approximately equal length for propagating the plurality of modulated optical signals at a velocity dependent on the optical wavelength of each of the modulated optical signals thereby producing a plurality of time delayed modulated optical signals;

means for respectively converting the plurality of time delayed modulated optical signals into a plurality of electrical signals;

means for respectively equalizing the nominal time delays of the plurality of electrical signals;

means for respectively amplifying the plurality of nominally equalized electrical signals;

means for transmitting the plurality of nominally equalized electrical signals;

means for receiving a plurality of electromagnetic signals; and

means for respectively amplifying, controlling and mixing the plurality of nominally equalized electrical signals with the plurality of received electromagnetic signals.

49. An array antenna system having a fiber optic true time-delay antenna feed system comprising:

a tunable light source for generating a plurality of narrow-linewidth wavelength-controlled continuous-wave optical carriers;

means for combining the plurality of optical carriers into a combined optical carrier;

means for generating a first plurality of external independent electrical signals;

means for combining the first plurality of external independent electrical signals into a combine electrical signal;

means for modulating the combined optical carrier with the combined electrical signal to produce a first combined modulated optical signal;

means for splitting the first combined modulated optical signal into a plurality of first combined modulated optical signals;

means for propagating each of the plurality of first combined modulated optical signals through an optical fiber comprised of dispersive and non-dispersive optical fibers of approximately an equal length at a velocity dependent on a predetermined wavelength of each of the plurality of first combined modulated optical signals to form a plurality of time-delayed first combined modulated optical signals;

means for combining the plurality of time-delayed first combined modulated optical signals to form a second combined modulated optical signal;

means for converting the second combined modulated optical signal into a second combined electrical signal;

means for independently controlling the wavelength of the optical carriers thereby setting and varying the time-delay of the electrical signals from the modulating means to the converting means; and

means for respectively amplifying the second combined electrical signals to produce a filtered output electrical signal.

50. A method for providing a fiber-optic true time-delay array antenna feed comprising the steps of:

generating a plurality of narrow-linewidth wavelength-controlled optical carriers;

combining the plurality of narrow-linewidth wavelength-controlled optical carriers to form a single optical carrier;

generating an electromagnetic signal;

modulating the optical signal with the electromagnetic signal producing a modulated optical signal;

splitting the modulated optical signal into a plurality of modulated optical signals, each of the modulated optical signals having a time-delay differing from each other modulated optical signal;

converting each time-delayed modulated optical signals into a time-delayed electrical signal; and

applying each time-delayed electrical signal to an element of an array antenna.

51. A fiber optic true time-delay array antenna feed system comprising:

one or more tunable light sources for generating a plurality of narrow-linewidth wavelength-controlled continuous-wave optical carriers;

one or more electrical signals;

means for modulating at least one optical carrier with at least one electrical signal to form a modulated optical signal;

means for splitting each modulated optical signal into a plurality of modulated optical signals;

a plurality of optical fibers having a different net optical dispersion from the net optical dispersion of any other optical fiber within the plurality of optical fibers determined by a makeup of different lengths of dispersive and non-dispersive optical fiber calculated to provide a desired wavelength dependence on the time delay in that optical fiber for receiving and propagating, respectively, the plurality of modulated optical signals so that each modulated optical signal has a time-delay differing from the time-delay of each of the other modulated optical signals of the plurality of modulated optical signals;

means for respectively converting the plurality of time delayed modulated optical signals into a plurality of electrical signals;

means for equalizing the nominal time delays of the plurality of electrical signals;

means for respectively amplifying the plurality of nominally equalized electrical signals;

means for transmitting the plurality of amplified nominally equalized electrical signals;

means for receiving a plurality of electromagnetic signals; and

,

means for respectively amplifying, controlling and mixing the plurality of nominally equalized electrical signals with the plurality of nominally equalized electrical signals with the plurality of received electromagnetic signals.