Method for maintaining instantaneous bandwidth for a segmented, mechanically augmented phased array antenna

• US 6,356,239 B1
• Filed: 08/23/2000
• Issued: 03/12/2002
• Est. Priority Date: 08/23/2000
• Status: Expired due to Term

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Carson, Ronald Steven
• Primary Examiner(s): Ho, Tan
• Application Number:
  US09/644,328
• Time in Patent Office: 566 Days
• Field of Search: 343/709, 343/710, 343/711, 343/754, 343/761, 343/765, 343/766, 343/882, 343/757, 342/367, 342/368, 342/375, 342/376, 248/183
• US Class Current: 343/765
• CPC Class Codes: H01Q 1/125 Means for positioning
• CPC Class Codes: H01Q 3/04 for varying one co-ordinate of the orientation
• CPC Class Codes: H01Q 3/08 for varying two co-ordinates of the orientation
• CPC Class Codes: H01Q 3/10 to produce a conical or spiral scan
• CPC Class Codes: H01Q 3/26 varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture H01Q3/12, H01Q3/22, H01Q3/24 take precedence

Abstract

A system and method for positioning an electronically scanned, phased array antenna disposed on a moving platform, such as an aircraft, to enable the antenna to remain pointed at, and track, a geostationary satellite as the moving platform is in motion. The antenna is mounted on a support which is coupled to an output shaft of a motor. The motor is used to rotate the support, and therefore the antenna, as needed to maintain the beam of the antenna directed at the satellite. The support is rotated only after a scan angle of the beam of the antenna exceeds a predetermined maximum scan angle. The degree of rotational movement of the support is further selected to be such that only a minimum number of adjustments to the position of the support are needed to maintain the scan angle of the beam of the antenna within the desired maximum scan angle over a large distance of travel of the aircraft. The invention significantly reduces the frequency of adjustment of the position of the support required to maintain the antenna directed at the desired satellite, and thus significantly reduces wear and tear on the motor without adversely affecting the antenna'"'"'s ability to track a target satellite.

Claims

1. A method for positioning an electronically scanned phased array antenna disposed on a rotatable support in real time, wherein the support is disposed on a moving platform, as said antenna tracks a radio frequency transponder fixed in position relative to the Earth, to maintain an actual scan angle of a beam of said antenna within a predetermined scan angle range necessary to maintain a desired bandwidth of said antenna at a given wavelength, said method comprising the steps of:

determining a maximum scan angle not to be exceeded in order to maintain said desired bandwidth when said antenna is being scanned to track said transponder while said support is being held stationary;

defining a rotational path of movement of said antenna to include a plurality of generally evenly spaced apart locations to which said support can be rotated, with a distance between adjacent ones of said locations being determined so as to result in a change in magnitude of less than about twice that of said predetermined maximum scan angle;

monitoring said actual scan angle of said antenna during movement of said moving platform and, if said actual scan angle exceeds said predetermined maximum scan angle, rotating said support to a next adjacent one of said locations and in a direction necessary to point said antenna relative to said transponder to cause said actual scan angle to be reduced in magnitude below said maximum scan angle.

2. The method of claim 1, further comprising the step of initializing said support to determine a reference position of said support.

3. The method of claim 1, wherein the step of rotating said support by a fixed increment of movement comprises moving the support by a value of no more than approximately 24 degrees.

4. The method of claim 1, further comprising the step of segmenting said movement of said support into no more than 20 distinct rotational positions to which said support can be rotated.

5. A method for positioning an electronically scanned phased array antenna disposed on a rotatable support in real time, wherein the support is disposed on a moving platform, as said antenna tracks a space-based radio frequency transponder, to maintain an actual scan angle of a beam of said antenna within a predetermined scan angle range necessary to maintain a desired bandwidth of said antenna at a given wavelength, said method comprising the steps of:

providing a dual element, electronically scanned phased array antenna;

determining a true-time-delay (TTD) increment between said dual elements of said electronically scanned phased array antenna and using said increment to determine a maximum scan angle not to be exceeded in order to maintain said desired bandwidth; and

monitoring said actual scan angle during movement of said moving platform and, if said actual scan angle exceeds said predetermined maximum scan angle, rotating said support in a direction necessary to cause said actual scan angle to be reduced in magnitude below said maximum scan angle.

6. The method of claim 5, further comprising the step of:

determining a fixed increment of movement by which said support is to be rotated.

7. The method of claim 6, further comprising the step of:

when said actual scan angle exceeds said maximum predetermined scan angle, causing said support to be rotated by a number of degrees that is less than twice said maximum scan angle.

8. The method of claim 6, wherein the step of determining said maximum scan angle comprises setting said maximum scan angle to approximately 14 degrees;

and

wherein the step of determining said fixed increment of movement comprises setting said fixed increment of movement to a value less than approximately 24 degrees.

9. The method of claim 5, further comprising the step of determining whether to rotate said support clockwise or counterclockwise when it is determined that said actual scan angle has exceeded said maximum scan angle.

10. A method for positioning an electronically scanned phased array antenna disposed on a rotatable support in real time, wherein the support is disposed on a moving platform, as said antenna tracks a space-based radio frequency transponder, to maintain an actual scan angle of a beam of said antenna within a predetermined scan angle range necessary to maintain a desired bandwidth of said antenna at a given wavelength, said method comprising the steps of:

providing a dual element, electronically scanned phased array antenna;

determining a true-time-delay (TTD) increment between said dual elements of said electronically scanned phased array antenna and using said increment to determine a maximum scan angle not to be exceeded in order to maintain said desired bandwidth;

segmenting movement of said support into a plurality of distinct rotational positions to which said support can be rotated, said plurality of distinct rotational positions being selected based upon said maximum desired scan angle;

monitoring said actual scan angle during movement of said moving platform;

comparing said actual scan angle to said predetermined maximum scan angle;

if said actual scan angle exceeds said predetermined maximum scan angle, rotating said support to one of said distinct rotational positions immediately adjacent its present said rotational position to cause said actual scan angle to be reduced in magnitude below said maximum scan angle.

11. The method of claim 10, wherein the step of determining said maximum scan angle comprises setting said maximum scan angle at approximately 14 degrees.

12. The method of claim 10, wherein the step of segmenting movement of said support into a plurality of distinct rotational positions comprises the step of segmenting movement of said support into no more than 20 distinct rotational positions.

13. The method of claim 10, further comprising the step of initializing said support to establish a reference position of said support.

14. A method for positioning an electronically scanned phased array antenna disposed on a rotatable support to thus cause said antenna to track a desired target, wherein the support is disposed on a moving platform, to thereby maintain an actual scan angle of a beam of said antenna within a predetermined scan angle range necessary to maintain a desired bandwidth of said antenna at a given wavelength, said method comprising the steps of:

determining a maximum scan angle not to be exceeded in order to maintain said desired bandwidth;

segmenting rotational movement of said support into a plurality of distinct, evenly spaced apart rotational positions to which said support can be rotated, wherein said plurality of rotational positions selected does not exceed by a factor of two said determined maximum scan angle; and

monitoring said actual scan angle of said antenna during movement of said moving platform and, if said actual scan angle exceeds said predetermined maximum scan angle, rotating said support in a direction necessary to point said antenna relative to said desired target to cause said actual scan angle to be reduced in magnitude below said maximum scan angle.

15. The method of claim 14, wherein said step of determining said maximum scan angle comprises the step of setting said maximum scan angle to approximately 14 degrees.

16. The method of claim 14, wherein the step of segmenting rotational movement of said support into said plurality of distinct rotational positions comprises the step of segmenting movement of said support into evenly spaced apart rotational positions spaced at least approximately 18 degrees apart from one another.