Distributed array for direction and frequency finding

Patent metadata

Field	Value
Publication number	US-10911142-B2
Application number	US-201916284984-A
Country	US
Kind code	B2
Filing date	Feb 25, 2019
Priority date	Aug 3, 2015
Publication date	Feb 2, 2021
Grant date	Feb 2, 2021

Abstract

An optical imaging system and method that reconstructs RF sources in k-space by utilizing interference amongst modulated optical beams. The system and method involves recording with photodetectors the interference pattern produced by RF-modulated optical beams conveyed by optical fibers having unequal lengths. The photodetectors record the interference, and computational analysis using known tomography reconstruction methods is performed to reconstruct the RF sources in k-space.

First claim

What is claimed:

1. An optical imaging receiver comprising:
a phased-array antenna including a plurality of antenna elements configured to receive RF radiation from at least a first RF source, each antenna element configured to provide a corresponding RF signal in response to the received radiation;
a plurality of electro-optic modulators each in communication with a corresponding one of the plurality of antenna elements, each modulator configured to modulate an optical carrier with a corresponding RF signal received from the corresponding one of the plurality of antenna elements to generate a corresponding modulated optical signal, the plurality of electro-optic modulators thereby generating a plurality of modulated optical signals;
a plurality of optical waveguides configured to transmit the plurality of modulated optical signals, each of the plurality of optical waveguides having an output to emanate the corresponding modulated optical signal out of the corresponding optical waveguide to an interference space to provide interference amongst the modulated optical signals;
a plurality of photodetectors to detect the optical signal interference; and
a processor configured to determine frequency and location information of the first RF source as a function of the optical signal interference detected by the photodetectors.

2. The optical imaging receiver of claim 1 , said plurality of optical waveguides comprising a plurality of optical fibers, the optical fibers having varying lengths.

3. The optical imaging receiver of claim 2 , wherein at least two optical fibers of said plurality of optical fibers are connected to the output of a first one of the plurality of modulators.

4. The optical imaging receiver of claim 1 , wherein the distribution of antennas in the phased-array antenna is non-coplanar.

5. The optical imaging receiver of claim 1 , wherein the processor is configured to use a computational tomography technique to reconstruct the first RF source in k-space from the optical signal interference detected by the photodetectors.

6. The optical imaging receiver of claim 2 , wherein lengths of the optical fibers vary linearly in accordance with corresponding positions of antennas in the antenna array to which they are in communication therewith.

7. A method utilized by an optical imaging receiver for RF signal processing, comprising:
receiving incoming RF radiation from at least one RF source at a phased-array antenna including a plurality of antenna elements arranged in a first pattern, each of the plurality of antenna elements generating a corresponding RF signal in response to the received radiation;
modulating each of the RF signals from each of the plurality of antenna elements onto an optical carrier to generate a plurality of modulated optical signals;
directing the plurality of modulated optical signals to an interference space to provide interference amongst the modulated optical signals;
detecting an interference pattern resulting from the interference of the modulated optical signals; and
computationally reconstructing the at least one RF source in k-space from the detected interference pattern.

8. The method of claim 7 , wherein the plurality of modulated optical signals are directed to the interference space by a plurality of optical waveguides having varied path lengths.

9. The method of claim 8 ,
wherein the RF signals are modulated with corresponding electro-optic modulators to generate the plurality of modulated optical signals, and
wherein outputs of the modulated optical signals output by the electro-optic modulators are split into multiple waveguides and provided to the interference space.

10. The method of claim 7 , wherein the distribution of antennas in the phased-array antenna is non-coplanar.

11. The method of claim 7 , wherein computationally reconstructing involves using a computational tomography technique.

12. The method of claim 8 , wherein the lengths of the waveguides vary linearly in accordance with corresponding positions of antennas in the antenna array to which they are in communication therewith.

13. The optical imaging receiver of claim 1 , wherein outputs of the optical waveguides are arranged in a pattern that is independent from a pattern of the arrangement of the plurality of antennas with which the optical waveguides are in communication.

14. The optical imaging receiver of claim 1 , wherein outputs of the optical waveguides are arranged in a first pattern, the plurality of antennas are arranged in a second pattern, wherein the first pattern correlates to the second pattern.

15. The optical imaging receiver of claim 14 , wherein the first pattern is the same as the second pattern.

16. The optical imaging receiver of claim 1 , wherein the plurality of optical waveguides comprise plural sets of optical fibers, and wherein each set of optical fibers is in communication with each of the plurality of antenna elements to provide corresponding modulated optical signals to the interference space.

17. The optical imaging receiver of claim 1 , wherein, for each electro-optic modulator, multiple ones of the optical waveguides are configured to receive a corresponding modulated optical signal from the electro-optic modulator.

18. The optical imaging receive of claim 17 , wherein the optical waveguides includes multiple optical fiber bundles to form multiple images.

19. The optical imaging receiver of claim 1 ,
wherein the processor is configured to determine corresponding frequency and location information of a plurality of RF sources in real time.

20. The optical imaging receiver of claim 19 , wherein the processor is configured to determine in real time k-space information of each of the plurality of RF sources in an RF scene detected by the antenna array, the k-space information including, for each RF source, a frequency of the RF source and an angle of arrival of RF electromagnetic signals emitted by the RF source.

21. The method of claim 7 ,
wherein the plurality of modulated optical signals are directed to the interference space by a plurality of optical waveguides, and
wherein outputs of the optical waveguides are arranged in a pattern that is independent from a pattern of the arrangement of the plurality of antennas with which the optical waveguides are in communication.

22. The method of claim 7 ,
wherein the plurality of modulated optical signals are directed to the interference space by a plurality of optical waveguides, and
wherein outputs of the optical waveguides are arranged in a first pattern, the plurality of antennas are arranged in a second pattern, wherein the first pattern correlates to the second pattern.

23. The method of claim 22 , wherein the first pattern is the same as the second pattern.

24. The method of claim 7 , wherein each of the plurality of modulated optical signals are split and directed to the interference space with plural sets of optical waveguides.

25. The method of claim 7 , wherein the plural sets of optical waveguides are plural sets of optical fibers, and wherein each set of optical fibers is in communication with each of the plurality of antenna elements to provide corresponding modulated optical signals to the interference space.

26. The method of claim 25 , wherein the sets of optical fibers are separate from each other at the interference space.

27. The method of claim 25 , wherein

Assignees

• Phase Sensitive Innovations Inc

Inventors

• Murakowski Janusz
• Schuetz Chris
• Schneider Garrett
• Shi Shouyuan

Classifications

• H04B10/00 Primary

  Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication · CPC title

• H04B10/11 Primary

  Arrangements specific to free-space transmission, i.e. transmission through air or vacuum · CPC title

• H04B2210/006

  Devices for generating or processing an RF signal by optical means · CPC title

• H04B10/60

  Receivers · CPC title

• H04B7/08

  at the receiving station · CPC title