Method of tracking steerable antennas on platforms to form an RF communication link

Patent metadata

Field	Value
Publication number	US-10833405-B2
Application number	US-201615760429-A
Country	US
Kind code	B2
Filing date	Jul 21, 2016
Priority date	Dec 11, 2015
Publication date	Nov 10, 2020
Grant date	Nov 10, 2020

Abstract

Steerable antenna on platforms, fixed or mobile, are tracked to form an RF communication link by setting the width of the main lobe of the antenna beam pattern to be greater than the initial pointing uncertainty region and then concurrently scanning and progressively reducing the widths of the main lobes as the pointing uncertainty region is reduced to first acquire and then track the opposing antenna. The width of the main lobe is reduced such that the width of the main lobe is approximately fixed for each block. The antennas at opposite ends of the communication link may be scanned with scan patterns that are orthogonal to each other such that the demodulation of the received signal levels to signal direction of arrival at each platform is solely a function of the scan pattern of the receive antenna.

First claim

We claim:

1. A method of pointing and tracking radio frequency (RF) transceiver antennas on platforms to form an RF communication link, comprising:
a) providing a first platform having a steerable RF transceiver antenna, said transceiver antenna configured to transmit and receive with a beam pattern having a main lobe and side lobes, said transceiver antenna configurable to vary the width of the main lobe;
b) providing a second platform having a steerable RF transceiver antenna, said transceiver antenna configured to transmit and receive with a beam pattern having a main lobe and side lobes, said transceiver antenna configurable to vary the width of the main lobe;
c) at each platform, from coordinates of both the first and second platforms and orientation of that platform, determining a pointing direction of the RF transceiver antenna towards the opposing RF transceiver antenna and a pointing uncertainty region;
d) at each platform and concurrently, setting the width of the main lobe greater than the pointing uncertainty region and scanning the beam pattern over a scan pattern to transmit an RF signal to and receive an RF signal from the RF transceiver on the other platform within the main lobe, acquiring a block of received signal levels for an approximately fixed width of the main lobe, and processing a modulation of the received signal levels to update the pointing direction and reduce the pointing uncertainty region of the RF transceiver antenna to track the opposite RF transceiver antenna; and
e) repeating step d with progressively narrower widths of the main lobe greater than the reduced pointing uncertainty region until the width of the main lobe reaches a high gain narrow beam width condition to form the RF communication link.

2. The method of claim 1 , wherein the scan patterns of the opposing RF transceiver antennas are substantially orthogonal to each other for at least a primary component of the scan pattern such that the demodulation of the received signal levels to signal direction of arrival is a function of only the scan pattern of that transceiver antenna and not the scan pattern of the opposing transceiver antenna despite the signal level varying due to the scan pattern and a pointing error of both antennas within the pointing uncertainty region.

3. The method of claim 2 , wherein the scan patterns are substantially orthogonal to each other for the primary component and at least one harmonic component of the scan pattern.

4. The method of claim 2 , wherein the transceiver antennas are scanned over the scan pattern at different rates so that the scan patterns are orthogonal in frequency.

5. The method of claim 1 , further comprising reducing the extent of the scan pattern with the reduction in the width of the main lobe so that the received RF signal remains within the main lobe.

6. The method of claim 1 , wherein the block of received signal levels represents at least one full scan pattern at the approximately fixed width of the main lobe.

7. The method of claim 1 , wherein the width of the main lobe is set just greater than the pointing error.

8. The method of claim 1 , wherein the width of the main lobe is continuously reduced from an initial low gain broad beam width condition to the high gain narrow beam width condition, wherein the rate of reduction is sufficiently slow that the width of the main lobe is approximately fixed for each block of received signal levels.

9. The method of claim 1 , wherein the width of the main lobe is reduced in discrete steps between acquisition and processing of one or more blocks of received signal levels.

10. The method of claim 1 , wherein the width of the main lobe is reduced in a single discrete step from an initial low gain broad beam width condition to the high gain narrow beam width condition.

11. The method of claim 1 , wherein each said steerable RF transceiver antenna comprises a gimbaled reflector-type antenna comprising a main reflector having a focal point, a sub-reflector nominally positioned at the focal point and an RF feed, wherein width of the main antenna beam is initially set by axially translating the sub-reflector away from the focal point to defocus the beam and wherein the width of the main antenna beam is reduced by axially translating the sub-reflector towards the focal point to focus the beam.

12. The method of claim 11 , wherein the focal point to antenna diameter ratio (F/D) is less than 1.

13. The method of claim 11 , wherein the reflector-type antenna further comprises:
a sub-reflector strut system comprising a plurality of struts, each strut attached at one end to the sub-reflector and extending radially and backwards past the main reflector; and
a stepper motor mounted behind the main reflector to drive the sub-reflector strut system axially to translate the sub-reflector.

14. The method of claim 13 , wherein the stepper motor comprises either a turn-screw or solenoid stepper motor.

15. The method of claim 1 , wherein the RF communication link is above 1 GHz.

16. The method of claim 1 , wherein said first and second platforms are mobile platforms.

17. The method of claim 1 , wherein said first and second platforms are fixed platforms.

18. The method of claim 1 , wherein said first platform is a mobile platform and said second platform is a fixed platform.

19. A method of pointing and tracking radio frequency (RF) transceiver antennas on platforms to form an RF communication link, comprising:
a) providing a first platform having a steerable RF transceiver antenna, said transceiver antenna configured to transmit and receive with a beam pattern having a main lobe and side lobes, said transceiver antenna configurable to vary the width of the main lobe;
b) providing a second platform having a steerable RF transceiver antenna, said transceiver antenna configured to transmit and receive with a beam pattern having a main lobe and side lobes, said transceiver antenna configurable to vary the width of the main lobe;
c) at each platform, from coordinates of both the first and second platforms and orientation of that platform, determining a pointing direction of the RF transceiver antenna towards the opposing RF transceiver antenna and a pointing uncertainty region;
d) at each platform and concurrently, setting the width of the main lobe greater than the pointing uncertainty region and scanning the beam pattern over a scan pattern to transmit an RF signal to and receive an RF signal from the RF transceiver on the other platform within the main lobe, acquiring a block of received signal levels for at least one full scan pattern for an approximately fixed width of the main lobe, and processing a modulation of the received signal levels to update the pointing direction and reduce the pointing uncertainty region of the RF transceiver antenna to track the opposite RF transceiver antenna, wherein the scan patterns of the opposing RF transceiver antennas are substantially orthogonal to each other for at least a primary component of the scan pattern such that the demodulation of the received signal levels to signal direction of arrival is a function of only the scan pattern of that transceiver antenna and not the scan pattern of the opposing transceiver antenna despite the signal level varying due to the scan pattern and a pointing error of both antennas within the pointing uncertainty region; and
e) repeating step d with progressively narrower widths of the main lobe greater than the reduced pointing uncertainty region and progressively smaller extents of the scan pattern s

Assignees

• Raytheon Co

Inventors

• Brown Kenneth W
• Rattray Alan
• Feenstra Travis B
• De La Torre Samuel
• Kullstam Johan A
• Pierce Arlin L

Classifications

• H01Q3/10 Primary

  to produce a conical or spiral scan · CPC title

• H01Q3/18

  wherein the primary active element is movable and the reflecting device is fixed · CPC title

• H01Q19/19

  comprising one main concave reflecting surface associated with an auxiliary reflecting surface · CPC title

• H04B7/0617

  for beam forming · CPC title

• H01Q19/10

  using reflecting surfaces · CPC title