Device and method for polarization control for a phased array antenna
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.
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 c t+φ i ); and
where the signal exciting a vertical port is written as
a w(i) a v(i) cos(ω c t+φ i +δφ v ) and;
where ω c is the radian frequency of the RF carrier; and
where the desired polarization is slant-linear the phase difference δφ 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 =cos 2 ψ s ; and
the fraction to be excited in the vertically polarized mode is F v =1−F h =sin 2 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 c t+φ i ); and
where the signal exciting a vertical port is written as
a w(i) a v(i) cos(ω c t+φ i +δφ v ) and;
where ω c is the radian frequency of the RF carrier; and
where the desired polarization is slant-linear the phase difference δφ 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 =cos 2 ψ s ; and
the fraction to be excited in the vertically polarized mode is F v =1−F h =sin 2 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.