Device and method for polarization control for a phased array antenna

• US 7,436,370 B2
• Filed: 10/12/2006
• Issued: 10/14/2008
• Est. Priority Date: 10/14/2005
• Status: Expired due to Fees

• Current Assignee: L-3 Communications Titan Corporation (L3Harris Technologies, Inc.)
• Original Assignee: L-3 Communications Titan Corporation (L3Harris Technologies, Inc.)
• Inventors: Blanton, James L.
• Primary Examiner(s): PHAN, THO GIA
• Application Number:
  US11/580,574
• Publication Number:
  US 20080218424A1
• Time in Patent Office: 733 Days
• Field of Search: 343/756, 343/853, 343/757, 343/766, 342/359
• US Class Current: 343/756
• CPC Class Codes: H01Q 21/061 Two dimensional planar arrays
• CPC Class Codes: H01Q 21/245 provided with means for varying the polarisation polarising devices H01Q15/24; tracking by comparing linear polarisation compounds G01S3/146; reducing depolarisation effects H04B7/00; polarisation diversity H04B7/10

Abstract

A method of configuring a phased array antenna having a plurality of radiators, each said radiator elements capable of radiating or receiving signals in one of two orthogonal polarizations determined to achieve a pseudo-random mix of horizontally and vertically polarized radiators. Upon switching of each of the radiator elements to a calculated one of said two polarizations, a desired slant angle for the antenna is achieved.

Claims

1. A method of controlling the polarization of a phased array antenna having a plurality of individual radiator elements, each of which is capable of radiating and receiving signals in one of two orthogonal, switch-selected polarizations, to yield a desired polarization in said antenna with any desired slant angle, comprising the steps of:

determining a desired polarization slant angle for said phased array antenna for communication with an orbiting satellite from a terrestrial location;

employing a polarization assignment algorithm to calculate a population ratio of said plurality of radiator elements between two orthogonal polarizations to ascertain a determined polarization state, from said two orthogonal polarizations, for each said plurality of radiator elements, to achieve said population ratio; and

switching each respective said radiator element, to said determined polarization state, to yield said population ratio, whereby the desired slant angle is achieved in said phased array antenna.

2. The method of controlling the polarization of a phased array antenna of claim 1 additionally comprising the steps of:

employing a deterministic algorithm as said polarization assignment algorithm.

3. The method of controlling the polarization of a phased array antenna of claim 2 additionally comprising the steps of:

employing a data processor with computer software adapted to run said polarization assignment algorithm; and

communicating to a respective means for switching each individual radiator element to one of said two orthogonal, polarizations, the determined polarization state said respective element, to cause each member of said plurality of radiator elements to assume said determined polarization state.

4. The method of controlling the polarization of a phased array antenna of claim 1 additionally comprising the steps of:

employing a probabilistic algorithm as said polarization assignment algorithm.

5. The method of controlling the polarization of a phased array antenna of claim 4 additionally comprising the steps of:

employing a data processor with computer software adapted to run said polarization assignment algorithm; and

communicating to a respective means for switching each individual radiator element to one of said two orthogonal, polarizations, the determined polarization state said respective element, to cause each member of said plurality of radiator elements to assume said determined polarization state.

6. The method of controlling the polarization of a phased array antenna of claim 1 additionally comprising the steps of:

employing a data processor with computer software adapted to run said polarization assignment algorithm; and

communicating to a respective means for switching each individual radiator element to one of said two orthogonal, polarizations, the determined polarization state said respective element, to cause each member of said plurality of radiator elements to assume said determined polarization state.

7. The method of claim 6 wherein said the polarization assignment algorithm employed to calculate said desired switching mode to yield said desired one of said two polarizations, for each said respective radiator element, is determined by the equation:

where an RF signal exciting a horizontal radiator port can be expressed using magnitude and phase as

a_w(i)a_h(i)cos(ω

_ct+φ

_i); and

where the signal exciting a vertical port is written as

a_w(i)a_v(i)cos(ω

_ct+φ

_i+δ

φ

_v) and;

where ω

_c is the radian frequency of the RF carrier; and

where the desired polarization is slant-linear the phase difference δ

φ

_v can be ignored; and

where the desired polarization slant angle can be designated ψ

_s, where a value of zero represents horizontal polarization and a value of π

/2 (or 90 degrees) represents vertical polarization; and

where the fraction of radiators to be excited in the horizontally polarized mode is F_h=cos² ψ

_s; and

the fraction to be excited in the vertically polarized mode is F_v=1−

F_h=sin² ψ

_s; and

where U represents a uniformly distributed random variable having values ranging between 0 and 1; and

for each radiator element i a new value of u is generated;

employing a polarization assignment algorithm to switch polarization between horizontal and vertical for each radiator element at the element level, employing the polarization switch as follows;

if u_i<

F_h

(a_h(i)=1;

a_v(i)=0)

polarization switch set to horizontal, otherwise

(a_h(i)=0;

a_v(i)=1)

polarization switch set to vertical, wherein the a_h(i) and a_v(i) weights discussed above are effectively applied multiplicatively with other amplitude weighting function(s) required for sidelobe control.

8. The method of controlling the polarization of a phased array antenna of claim 6 additionally comprising the steps of:

employing a commanded phase difference between populations of orthogonally polarized radiator elements to generate circular or elliptical polarization.

9. The method of claim 1 wherein said the polarization assignment algorithm employed to calculate said desired switching mode to yield said desired one of said two polarizations, for each said respective radiator element, is determined by the equation:

where an RF signal exciting a horizontal radiator port can be expressed using magnitude and phase as

a_w(i)a_h(i)cos(ω

_ct+φ

_i); and

where the signal exciting a vertical port is written as

a_w(i)a_v(i)cos(ω

_ct+φ

_i+δ

φ

_v) and;

where ω

_c is the radian frequency of the RF carrier; and

where the desired polarization is slant-linear the phase difference δ

φ

_v can be ignored; and

where the desired polarization slant angle can be designated ψ

_s, where a value of zero represents horizontal polarization and a value of π

/2 (or 90 degrees) represents vertical polarization; and

where the fraction of radiators to be excited in the horizontally polarized mode is F_h=cos² ψ

_s; and

the fraction to be excited in the vertically polarized mode is F_v=1−

F_h=sin² ψ

_s; and

where u represents a uniformly distributed random variable having values ranging between 0 and 1; and

for each radiator element i a new value of u is generated;

employing a polarization assignment algorithm to switch polarization between horizontal and vertical for each radiator element at the element level, employing the polarization switch as follows;

if u_i<

F_h

(a_h(i)=1;

a_v(i)=0)

polarization switch set to horizontal, otherwise

(a_h(i)=0;

a_v(i)=1)

polarization switch set to vertical, wherein a_h(i) and a_v(i) weights discussed above are effectively applied multiplicatively with other amplitude weighting function(s) required for sidelobe control.

10. The method of controlling the polarization of a phased array antenna of claim 1 additionally comprising the steps of:

employing a commanded phase difference between populations of orthogonally polarized radiator elements to generate circular or elliptical polarization.