A broadband adaptively controlled polarization separation network is discussed. Two transmitted signals vertically and horizontally polarized are received as elliptically polarized signals. If there is any vertical polarization on the other signal the separation network provides two signals. The separation is done automatically by the use of two sets of crosscouplers which couple a single line to the other line to complete the polarization decoupling operation

Gianatasio, A.

Pelchat, G. M.

Rassweiler, G. G.

Young, L. R.

English

NASA Technical Reports Server

United States Patent [19] 
Pelchat et al. 
[54] ADAPTIVE POLARIZATION SEPARATION 
[76] Inventors: Robert A. Frosch, Administrator of 
the National Aeronautics and Space 
Administration, with respect to an 
invention of Guy M. Pelchat, 
Indialantic, Fla.; George G. 
Rassweiler, Indialantic, Fla.; Anthony 
J. Gianatasio, Indialantic, Fla.; Lock 
R. Young, Palm Bay, Fla. 
[21] Appl. No.: 17,887 
[22] Filed: Mar. 6,1979 
[51] Int. C l . 3  ........................ HO4B 7/00; HOlQ 15/24 
[52] U.S. Cl. .............................................. 343/100 PE 
[58] Field of Search .................................. 343/100 PE 
~561 References Cited 
U.S. PATENT DOCUMENTS 
3,849,781 11/1974 Ort ............................. 343/100 PE X 
3,943,517 3/1976 Vogt .............................. 343/100 PE 
4,090,137 5/1978 Soma et al. ............... 343/100 PE X 
4,105,977 8/1978 Fitting et al. ............. 343/100 PE X 
4,106,015 8/1978 Beguin et al. ............. 343/100 PE X 
11 11 4,264,908 
[45] Apr. 28, 1981 
4,112,370 9/1978 Monsen ..................... 343/100 PE X 
Primary Examiner-T. H. Tubbesing 
Attorney, Agent, or Firm-William H. King; John R. 
Manning; Howard J. Osborn 
1571 AbSTRACT 
A broadband adaptive1 y controlled polarization separa- 
tion network. Two transmitted signals vertically and 
horizontally polarized are received as elleptically polar- 
ized signals. One of the two received elliptically polar- 
ized signals is automatically adjusted to make it linear 
and thereafter automatically adjusted to make it verti- 
cal. If the other signal does not have any vertical polar- 
ization on it then the two signals are easily separated 
and nothing else is needed. However, if there is any 
vertical polarization ofi the other signal this invention 
provides for separating the resulting crosstalk between 
the two signals. This is done automatically by the use of 
two sets of crosscouplers which couple a single line to 
the other line to complete the polarization decoupling 
operation. 
3 Claims, 3 Drawing Figures 
k. 50 k/ 51 , 
https://ntrs.nasa.gov/search.jsp?R=19810017821 2020-03-21T09:54:03+00:00Z
U.S. Patent Apr. 28, 1981 
dl 
M 
0 1 
cu 
d i 
(u 
0 
(u 
Sheet 1 of 2 
\ 
In cu 
00 
cu 
l a  
a w  
4,264,908 
- -  I 
U*S* Patent Apr. 28,1981 
- 
Sheet 2 of 2 4,264,908 
* 50 
BAND PASS 90 0 
FILTER PHASE M ULT I PL I ER 
f I SHIFTER 
L 
b C 
I 
a 
Y 
J 
FIG. 2 
1 - .r. 
=2 
I I 
900 
\ \ 
J PHASE MULTIPLIER 
SHIFTER - 
53 34 
9 
BAND PASS 
FILTER 4 
f 2  
I I 45 I I 46 
I 43, 
FIG. 3 
4.264,908 
1 
ADAPTIVE POLARIZATION SEPARATION 
ORIGIN OF THE INVENTION 
The invention described herein was made in the per- 
formance of work under a NASA Contract and is sub- 
ject to the provisions of section 305 of the National 
Aeronautics and Space Act of 1958, Public Law 85-568 
(72 Stat. 435; 42 USC 2457). 
BACKGROUND OF THE INVENTION 
The invention relates generally to communication 
systems and more specifically concerns a technique for 
increasing the data capacity of communication systems. 
It is reasonable to expect that future communication 
systems will be allegated only a very limited spectrum 
in desirable frequency bands, while bandwidths of sig- 
nals will be increasing. Several approaches, such as 
more efficient analog-to-digital conversion, more effi- 
cient modulation techniques, and dual polarization can 
be used to increase the data capacity of the available 
spectrums. This invention relates to the dual polariza- 
tion technique for increasing the data capacity. 
With, the technique of dual polarization, different 
channels are established for each of two orthogonal 
polarizations transmitted. Obviously, if the two polar- 
izations can be separated sufficiently, the effective data 
capacity for a given bandwidth is doubled. However, in 
a typical communication system, the received polariza- 
tions are rarely completely separated due to cross polar- 
ization crosstalk from various sources such as rain, non- 
perfect antennas, and ionospheric propagation. The 
presence of crosstalk will cause some degradation of the 
channel capacity of a communication system and thus, it 
may have to be reduced to a lower level for full poten- 
tial of dual polarization to be realized. This reduction 
can be done with a cross polarization correction net- 
work. 
In order to achieve a polarization correction net- 
work, in the face of varying cross polarization (due to 
such factors as varying rain), the correction network 
should be automatic or adaptive so as to track the vary- 
ing cross polarization. The past dual polarization cor- 
rection networks require a general search optimization 
algorithm and do not have a direct analog control. 
It is therefore the primary purpose of this invention to 
provide a dual polarization correction network that is 
automatic or adaptive so as to tracr the varying cross 
polarization. 
It is anothef object of this invention to provide a 
direct analog controlled dual polarization correction 
network. 
Other objects and advantages of this invention will 
become apparent hereinafter in the specifications and 
drawings. 
SUMMARY OF THE INVENTION 
The invention includes three sections: a lossless phase 
shift section, an orthogonalization section, and an ana- 
log automatic control section. The lossless phase shift 
section includes a rotatable 90" differential phase shifter 
which changes one of the received elliptical polarized 
signals to a linear polarized signal. This linear polarized 
signal is adjusted to vertical polarization by means of a 
rotatable 180" differential phase shifter. An orthomode 
transducer then separates the two polarized signals into 
their respective channels with the vertical linear polar- 
5 
10 
15 
20 
25 
30 
35 
40 
45 
50 
55 
60 
65 
ized signal in one channel and an elliptical polarized 
signal in the other channel. 
The orthogonalization section comprises two sets of 
crosscouplers. Each set of crosscouplers includes two 
mechanically ganged variable directional couplers that 
are connected together electrically. One set of couplers 
cancels the inphase crosstalk and the other set, which 
includes a 90" phase shifter, cancels the quadrature 
crosstalk. The analog automatic control section in- 
cludes means for detecting two different frequency CW 
tones that are included with the two received or trans- 
mitted signals and correlates these detected CW tones 
to form control signals which control the rotatable 90" 
differential phase shifter and the rotatable 180" differen- 
tial phase shifter in the lossless phase shifter section and 
which controls the two sets of crosscouplers in the 
orthogonalization section. 
BRIEF DESCRIPTION OF THE DRAWINGS 
FIGS. 1 and 3 together show a block diagram of the 
embodiment of the invention selected for illustration in 
the drawings; and 
FIG. 2 shows the polarization of the two received 
signals at different locations in the circuit. 
DETAILED DESCRIPTION OF THE 
INVENTION 
Turning now to the embodiment of the invention 
selected for illustration in the drawings the number 11 
designates the receiving antenna. The transmitted sig- 
nals are si vertically polarized and s2 horizontally polar- 
ized. The signals si and s2 contain CW tones at frequen- 
cies fi and f2, respectively. Ideally, the received signals 
si and s2 are linearly polarized with si vertical and s2 
horizontal. However, they are elliptically polarized 
signals as shown in diagram a of FIG. 2. The received 
signals are applied to a circular waveguide 12 which 
includes a rotatable 90" differential phase shifter 13 and 
a rotatable 180" differential phase shifter 14. Rotatable 
phase shifter 13 is controlled by a motor 15 to make the 
signal si linear polarized at the output of the phase 
shifter as shown in diagram b of FIG. 2. A less than 90" 
phase shifter can be used in place of phase shifter 13 if 
the ranges of polarization coupling is constrained; a 
smaller phase shift is desirable for wide band operation. 
Differential phase shifter 14 is adjusted by a motor 16 to 
make the signal SI vertically polarized at the output of 
phase shifter 14 as shown in diagram c of FIG. 2. 
The output of rotatable phase shifter 14 is applied to 
an orthomode transducer 17 which has its two outputs 
connected to rectangular waveguides 18 and 19. Ortho- 
mode transducer 17 has the property of passing the 
vertical polarization to waveguide 18 and the horizontal 
polarization to waveguide 19. The resulting signals e18 
and e19 in the rectangular waveguides 18 and 19, respec- 
tively are: 
eie=si+wz 
em=(i-lfil 2)*s2 
where p is related to the vertical component of s2. The 
two signals e18 and e19 are applied to a low noise ampli- 
fier 20 and a low noise amplifier 21, respectively. 
If the signal s2 as shown in diagram c of FIG. 2 has no 
vertical component, p is equal to zero and there is no 
crosstalk between si and s2. If s2 has a vertical compo- 
nent, p is not equal to zero and there is residual cross- 
3 
4,264,908 
talk between the two signals. To eliminate this residual 
crosstalk, two sets of crosscouplers 22 and 23 are pro- 
vided. A set of crosscouplers 22 which cancel the in- 
phase crosstalks includes variable directional couplers 
24 and 25. These two directonal couplers are connected 
together electrically by a connector 26 and are mechan- 
ically ganged by a linkage 27 which is controlled by a 
motor 28. A set of crosscouplers 23 which cancels the 
quadrature crosstalk includes variable directional cou- 
plers 29 and 30. These two directional couplers are 
connected together electrically through a 90" phase 
shifter 31 and are mechanically ganged by a linkage 32 
which is controlled by a motor 33. The resulting sepa- 
rated signals appear on output terminals 34 and 35. 
A set of crosscouplers consist of two mechanically 
ganged variable directional couplers. Such a crosscou- 
pler is usually implemented with a pair of orthomode 
transducers separated by a polarization rotator. With 
this arrangement, the coupling coefficient is sin 2 0 
where 8 is the mechanical alignment of the polarization 
rotator. This approach is capable of giving good cancel- 
lation over wide bandwidths with low incidental losses, 
an important consideration if sufficiently well matched 
low noise amplifiers are not available. With high gain, 
low noise amplifiers, it is possible to obtain good perfor- 
mance with couplers 24 and 30 fned at 3 dB. 
In the analog control system shown in FIG. 3, the 
signal at output terminal 34 is applied to an fi bandpass 
filter 40 whose output is applied directly to a multiplier 
43 and through a 90" phase shifter 41 to a multiplier 42. 
The output signal at output terminal 34 is also applied to 
an f2 bandpass filter 42 whose output is applied directly 
to a multiplier 47 and through a 90" phase shifter 45 to 
a multiplier 46. The output signal at output terminal 35 
is applied to an fi bandpass filter 48 whose output is 
applied directly to multipliers 42 and 43. The signal at 
output terminal 35 is also applied to an f2 bandpass filter 
49 whose output is applied directly to multipliers 46 and 
47. The output of multiplier 42 at terminal 50 is applied 
to motor 15 in FIG. 1 to control the rotatable 90" differ- 
ential phase shifter 13. The output of multiplier 43 at 
terminal 51 is applied to motor 16 to control the rotat- 
able 180" differential phase shifter 14. The output of 
multiplier 47 at terminal 52 is applied to motor 28 to . 
control the set of crosscouplers 22 and the output of 45 
multiplier 46 at terminal 53 is applied to motor 33 to 
control the set of crosscouplers 23. 
The output of multiplier 42 is the quadrature correla- 
tion signal measured on SI and is integrated by motor 15 
to provide the control for phase shifter 13 to make the 50 
received signal SI linear as shown in diagram b of FIG. 
2. The output of multiplier 43 is the inphase correlation 
voltage measured on si and is integrated by motor 16 to 
provide the control for phase shifter 14. The output of 
multiplier 47 is the inphase correlation measured on s2 55 
and is integrated by motor 28 to provide the control for 
the set of crosscouplers 22. The output of multiplier 46 
is the quadrature correlation voltage measured on s2 and 
is integrated by motor 33 to provide the control for the 
The control of phase shifter 13 is independent of the 
control of phase shifter 14 and is almost independent of 
the settings of the sets of crosscouplers 22 and 23 for all 
input polarizations. The control on phase shifter 14 is 
almost independent of all other controls as long as the 65 
other control variables are close to their desired value. 
The advantages of this invention are that it provides 
direct analog correlation circuit control; it minimizes 
set of crosscouplers 23. 60 
4 
mutual coupling between the four control loops; it em- 
ploys rotatable but electrically fixed waveguide phase 
shifters; it adjusts to make one polarization linear; it 
adjusts to completely eliminate the crosstalk for one of 
5 the signals; and it requires signal coupling from a single 
line to the other line to complete the polarization decou- 
pling operation. 
What is claimed is: 
1. A broadband adaptively controlled polarization 
an antenna for receiving two incoming signals si and 
s2 that were transmitted on vertical and horizontal 
polarizations, respectively, with the signals SI and 
s2 containing new CW tones at frequencies fl and 
a circular waveguide connected to said antenna and 
including a rotatable 90" phase shifter and a rotat- 
able 180" phase shifter connected in series; 
means connected to receive the output of said rotat- 
able 180" phase shifter for producing the vertical 
polarized signal at one of its outputs and for pro- 
ducing the horizontally polarized signal at its other 
output; 
a first fl bandpass filter connected to receive the verti- 
cal polarized signals from the last mentioned means 
and a second fi bandpass filter connected to receive 
the horizontal polarized signals from the last men- 
tioned means; 
a 90" phase shifter for shifting the output from said 
30 first fi bandpass filter; 
a first multiplier means for multiplying the signals 
from the 90" phase shifter with the signal from said 
second fi bandpass filter; 
a first motor means receiving the output signals from 
said first multiplier means for controlling said ro- 
tatable 90" phase shifter; 
a second multiplier means for multiplying the signals 
from said first fi bandpass filter with the signal 
from said second fi bandpass filter; second motor 
means receiving the output signals from said sec- 
ond multiplier means for controlling said rotatable 
180" Dhase shifter: 
10 separation network comprising: 
15 f2; respectively; 
20 
25 
35 
40 
r 
a first two mechanically ganged variable directional 
couplers connected together electrically for can- 
celling the inphase crosstalk between the vertical 
and horizontal polarized signals before they are 
applied to said first and second fi bandpass filters; 
and 
a second two mechanically ganged variable direc- 
tional couplers connected together electrically 
through a second 90" phase shifter for cancelling 
the quadrature crosstalk between the polarized 
signals before they are applied to said first and 
second fi bandpass filters. 
2. A broadband adaptively controlled polarization 
a first f2 bandpass filter connected to receive the verti- 
cal polarized signals after they have passed the first 
and second two mechanically ganged variable di- 
rectional couplers and a second f2 bandpass filter 
connected to receive the horizontal polarized sig- 
nals after they have passed the first and second two 
mechanically ganged variable directional couplers; 
a third multiplier means for multiplying the signal 
from the first f2 bandpass filter with the signals 
from the second f2 bandpass filter; and 
a third motor means receiving the output signals from 
said third multiplier means for controlling said first 
separation network according to claim 1 including: 
4,264,908 
5 6 
two mechanically ganged variable directional cou- 
plers. 
3. A broadband adaptively controlled polarization 
a third 90" phase shifter for shifting the output from 5 
a further multiplier means for multiplying the signal 
from the third 90" phase shifter with the signal 
from the second f2 bandpass filter; and 
a fourth motor means receiving the output signal 
from said fourth multiplier means for controlling 
said second two mechanically ganged variable 
directional couplers. 
separation network according to claim 2 including: 
said first f2 bandpass filter; * + * * *  
10 
15 
20 
25 
30 
35 
40 
45 
50 
55 
60 
65 


Adaptive polarization separation

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server