RAPID IN-THE-FIELD AUTO-ALIGNMENT FOR RADIO FREQUENCY AND FREE-SPACE OPTICAL DATA COMMUNICATION TRANSCEIVERS

• US 20140248049A1
• Filed: 03/05/2013
• Published: 09/04/2014
• Est. Priority Date: 03/02/2013
• Status: Active Grant

• Current Assignee: EOS Defense Systems USA Incorporated
• Original Assignee: Aoptix Technologies Incorporated
• Inventors: Saint Georges, Eric
• Granted Patent: US 9,264,137 B2
• Time in Patent Office: Days
• US Class Current: 398/25
• CPC Class Codes: H04B 10/1125 using a single common optical path

Abstract

A local communications apparatus is aligned with a remote apparatus, each apparatus comprising radio frequency (RF) and free space optical (FSO) transceivers with substantially parallel boresight. Coarse alignment is performed using the RF transceiver and fine alignment is performed using the FSO transceiver. A patterned search is performed to locate the RF signal from the remote apparatus and known features of the intensity profile are utilized to locate the global maximum, thus coarsely aligning the pair of apparatuses. A second patterned search is performed to locate the FSO signal from the remote apparatus and an iterative step-search is used to align the FSO signal centroid with the FSO transceiver, thus finely aligning the pair of apparatuses.

Claims

1. A method for aligning a local apparatus with a remote apparatus comprising:

adjusting an orientation of the local apparatus according to a first search pattern;

detecting a radio frequency (RF) signal from the remote apparatus;

adjusting the orientation of the local apparatus, the adjustment increasing an intensity of the detected RF signal;

adjusting a field-of-view of a free space optical (FSO) transceiver of the local apparatus according to a second search pattern;

detecting a FSO signal from the remote apparatus; and

performing an iterative step search to align the FSO transceiver with the detected FSO signal.

2. The method of claim 1, wherein the second adjusting step comprises:

adjusting the orientation of the local apparatus based on variation in the intensity of the detected RF signal, the adjustment locating a local maximum in the intensity of the detected RF signal.

3. The method of claim 2, wherein the second adjusting step further comprises:

adjusting the orientation of the local apparatus in a diverging search pattern until the intensity of the detected RF signal exceeds the intensity at the local maximum.

4. The method of claim 1, wherein adjusting the field-of-view of the FSO transceiver comprises:

adjusting an orientation of a fast steering mirror, the fast steering mirror optically coupled to the FSO transceiver.

5. The method of claim 4, further comprising:

adjusting, once the FSO transceiver is aligned with the detected FSO signal, the orientation of the local apparatus based on the orientation of the fast steering mirror.

6. A method for aligning a local apparatus with a remote apparatus, comprising:

adjusting an orientation of the local apparatus according to a first search pattern to detect a radio frequency (RF) signal from the remote apparatus;

adjusting the orientation of the local apparatus based on a spatial gradient of the detected RF signal;

determining an orientation of the local apparatus that corresponds to a local maximum in an intensity of the detected RF signal;

adjusting the orientation of the local apparatus according to a second search pattern;

adjusting the orientation of the local apparatus based on the spatial gradient of the detected RF signal; and

determining an orientation of the local apparatus that corresponds to a global maximum in the intensity of the detected RF signal.

7. The method of claim 6, wherein the first search pattern comprises:

adjusting the orientation of the local apparatus in a converging spiral pattern.

8. The method of claim 6, further comprising:

determining that the RF signal has been detected responsive to a received RF intensity of the RF transceiver being greater than a RF threshold.

9. The method of claim 6, wherein the second search pattern begins from the orientation of the local apparatus that corresponds to the local maximum.

10. The method of claim 6, wherein the second search pattern comprises:

adjusting the orientation of the local apparatus in a diverging spiral pattern.

11. The method of claim 6, wherein the second search pattern comprises:

adjusting the orientation of the local apparatus until the intensity of the detected RF signal exceeds the intensity of the detected RF signal at the local maximum.

12. The method of claim 6, further comprising:

dithering the orientation of the local apparatus at a local dithering frequency.

13. The method of claim 12, further comprising:

determining that the local apparatus is responsible for an observed drop in intensity of the detected RF signal based on the observed drop in intensity fluctuating at substantially the local dithering frequency.

14. A method for aligning a local apparatus with a remote apparatus, comprising:

adjusting a field-of-view of a free space optical (FSO) transceiver of the local apparatus according to a search pattern to detect a FSO signal from the remote apparatus;

adjusting the field-of-view of the FSO transceiver according to an iterative step-search; and

determining that a centroid of the FSO signal is substantially aligned with a quad-cell of the FSO transceiver based on one or more centroid-alignment conditions.

15. The method of claim 14, wherein the search pattern comprises:

adjusting the field-of-view of the FSO transceiver in a converging spiral pattern.

16. The method of claim 14, wherein the iterative step-search comprises one or more steps, each step comprising:

monitoring a measured level of incident optical radiation for each quadrant of the quad-cell, thereby identifying a quadrant upon which the received FSO signal is primarily incident; and

adjusting the effective orientation of the FSO transceiver, based on the identified quadrant.

17. The method of claim 16, wherein a first step adjusts the field-of-view by a first angle and each subsequent step adjusts the field-of-view by a smaller angle than a preceding step.

18. The method of claim 14, wherein the centroid-alignment conditions comprise the measured level of optical radiation for each quadrant of the quad-cell being equal, within a tolerance threshold.

19. The method of claim 14, wherein the centroid-alignment conditions comprise the measured level of optical radiation for each quadrant of the quad-cell exceeding a centroid-alignment threshold level.