|Publication number||US3768043 A|
|Publication date||Oct 23, 1973|
|Filing date||Jan 5, 1973|
|Priority date||Jan 5, 1973|
|Also published as||CA983132A, CA983132A1|
|Publication number||US 3768043 A, US 3768043A, US-A-3768043, US3768043 A, US3768043A|
|Original Assignee||Rca Corp|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (2), Referenced by (14), Classifications (13)|
|External Links: USPTO, USPTO Assignment, Espacenet|
United States Patent Foldes Oct. 23, 1973 l WIDEBAND HYBRID SYSTEM Primary Examiner-Rudolph V. Rolinec Assistant Examiner-Marvin Nussbaum :Pt Fld M t l,C d Inventor e er on ma ana a W Att0rneyEdward J. Norton et al. [73 Assignee: RCA Corporation, New York, NY.
 Filed: Jan. 5, 1973  ABSTRACT  APPL 321,469 An input diplexer separates wide frequency range signals by frequency to provide, at a plural ty of outputs, signals within different narrow frequency bands. A  US. Cl 333/6, 333/11, 333/21 A, plurality of quadrature h i are adapted so that 333/29 333/31 333/70 R1 333/73 w each hybrid achieves equal power division and 90 rel-  f Cl H16, H18, Help /12 ative phase shift with low distortion over one ofthe  Field of Search 333/6, 11, 21 R, narrow frequency bands. A hybrid i coupled to each 333/21 A, 31 R, 31 A, 70 1 73 R, 73 w output of the input diplexer. Output diplexers are coupled to the two outputs of each of the hybrids to com-  References W 1 bine the power divided narrow frequency band signals UNITED STATES PATENTS into two wide frequency band signals of substantially 2,727,141 12 1955 Cheek 333/29 x equal Power and differential P 3,056,096 9/1962 Vane 333/73 W X 5 Claims, 2 Drawing gu I QUADRATURE 2) I r- 1 1 49 1 3O 23 OUAR'ATURE ,35 1v I 1 2 1 46 PWR 1 Z'l ,230 373 i c0111; f 0, QUARATURE 1 d5 1 L 25, i L 39 3 9b 43 0.0. '27 U 1'" "1 \,27c 3 5 1 i 1 9 '1 9 9C 1 2 I 1 2 PWR 243 QUADRATURE 38 frh PWR I 8 1 mv. I711 3011 111111110 1 f COMB 1 3 4 I 1 34 i 3 4 1 2 f4- 1 1 4- 5 l l 32!] v l L l E 1 l Q L EZELJ llu PATENTEDnm 23 ms SHEET 18F 2 WIDEBAND HYBRID SYSTEM BACKGROUND OF THE INVENTION This invention relates to hybrids and more particularly to a polarizer using a system of hybrids for achieving 90 differential phase shift and power splitting over a wide band of frequencies with low amplitude and phase error.
It is desirable for achieving circular polarization that the signals fed to the orthogonally polarized antenna radiating element be at phase quadrature or 90 difference in relative phase and that the power be exactly divided. A practical way of achieving this with low loss is by means of a short slot hybrid. Although these short hybrid slot devices have had humps put at the center of the short slot region or the cross sectional width made smaller near the slotted region to achieve broadband operation, these hybrid structures remain relatively narrow band devices. When one of these devices is operated over a wide frequency band such as for example from 3,700 to 4,200 MHz (as in satellite communication systems), phase error of over is produced at some frequencies in the band. Consequently, relatively high axial ratios occur when the outputs of one ofthese are applied to the elements of an antenna. Wideband polarizers capable of achieving axial ratios in the order of 0.25 to 0.5 db are required over these above frequencies in satellite communication systems. This has heretofore not been achieved over such widebands using hybrids.
Briefly, according to the present invention substanequal in amplitude, 90 different in relative phase and no output power is coupled at 1 or reflected back to I Further, the purpose of the circuit is that the terminal I of diplexer 11 and the terminal of diplexer 11a be interchangable and simultaneously useful. All of the above functions are maintained in the f through f frequency band. Circular polarization is achieved by coupling the output at terminal 0 to one terminal 9a of an orthogonal coupler 9, for example, and the other output at terminal 0 is coupled to an orthogonally oriented terminal 9b of coupler 9. If these outputs at O, and 0 are equal in power and at phase quadrature pure circular polarization is achieved. The coupling to the orthogonally oriented terminal 9b may require a rotation of the polarization attitude 90. This rotation may be accomplished by a twisted waveguide section (rotator) 8 located in the coupling lead between terminal 0 and terminal 9b.
The input signal I at frequencies f, to f is divided on the basis of frequency by diplexer 11 into four frequency bands f to f f to f f,, to f, and f', to f The diplexer 11 is made up of a power divider 13 followed by a plurality of band-pass filters 15, 16,17 and 18. The
power divider l3 splits the input signal power into, for example, four signals of equal power and couples these separate signals to separate filters 15, l6, l7 and 18.
tially lower amplitude and phase error is achieved for 1 providing equal power division and 90 relative phase shift between the power divided outputs by the use of a first diplexer for subdividing the signals by frequency into subfrequency bands and by coupling the narrow frequency band signals to separate hybrids. The separate hybrids are each adapted to provide at their two separate outputs, power division and 90 relative phase shift between the power divided signals over the particular narrow frequency band coupled thereto with minimum amplitude and phase error. That one of the two outputs from each of the separate hybrids having substantially identical phase is coupled to a second diplexer for combining the narrow band signals to a first Wideband output. The second output from each of the separate hybrids is coupled to a third diplexer for combining the 90 relative phase shifted nar'row frequencyband signals to a second wideband output.
A more complete description of the subject invention follows in conjunction with the following drawings wherein:
FIG. 1 is a schematic diagram ofa Wideband hybrid system and a polarizer system using the same according to the presentinvention.
FIG. 2 is a perspective view of a portion of a wideband hybrid system shownin FIG. 1 with a portion of the top walls removed. g
Referring to-the block diagram of- FIG. 1, there is shown a Wideband hybrid system 10 consisting of two diplexers 11 and 11a at the input and two output diplexers 41 and 43 with four short slot quadrature hybrids 21, 23, 25 and 27 coupled therebetween. The purpose of the circuit is to divide the input power fed to the input terminall, of diplexer 11 into two parts occurring at the output terminals 0 of diplexer 41 and 0 of diplexer 43 in such a way that the output powers are The band-pass filter 15 is selected to pass those frequencies within the f, to f frequency band. Similarly,
band-pass filters l6, l7 and 18 are selected to pass the frequency bands f to f f; to f, and f, to f, respectively.
A plurality of hybrids 21, 23, 25 and 27 equal to the number of band-pass filters is provided. The hybrid 21 is adapted topro'vide equal power division of the input signal with differential phase shift between the power divided signals. The hybrid 21 is designed to accomplish this with minimum phase'and amplitude error between its two output ports over the frequencies of from f, to f,. The output of band-pass filter 15 is coupled via lead 29 to input terminal 21a of hybrid 21. The hybrid 23 'is similarly I adapted to operate as a 90 differential phase shifting power dividing coupler but with minimum phase and amplitude error over the frequencies from f to f,,. The output of band-pass filter 16 is coupled via lead 30 to terminal 23a of hybrid 23. The hybrid 25 is similarly a 90 differential phase shifting power dividing coupler which is adapted to operate 'with'minimum phase and amplitude error over the frequencies from f, to f,. The output of band-pass filter 17 is coupled via lead 31 to terminal 25a of hybrid 25. The hybrid 27 is a 90 differential phase shifting power dividing couplerwhich isadapted to operate with minimum phase and amplitude error over the frequencies from f to f The output of band-pass filter 18 is coupled via lead 32 to terminal 27a of hybrid 27. The hybrids 21, 23, 25 and 27 may each'be short slot hybrids as described, for example, by Riblett in US. Pat. Nos.
2,739,287 and 2,739,288. Basically, each of these short plexer 41 includes band-pass filters 45, 46, 47 and 4s; Bandpass filter 45 is adapted to couple only those signals with low attenuation between the frequencies off; to f Similarly, band-pass filter 46 is adapted to pass the frequencies off to f Band-pass filter 47 is adapted to pass the frequencies betweenf to f with low attenuation and band-pass filter 48 is adapted to pass frequencies between f. to f with low attenuation. In the diplexer 41 the outputs of band-pass filters 45, 46, 47 and 48 are each coupled to a power combiner 49 wherein the signals at frequencies from f to f are combined to provide an output at terminal 0,. Diplexer 43 is similarly arranged comprising band-pass filter 55 covering the frequency range from f to f band-pass filter 56 covering the frequency range from f to f band-pass filter 57 covering the frequency range from f tof., and band-pass filter 58 covering the frequency range from f, to f All the output power at the band-pass filters 55 through 58 are combined at power combiner 59 to provide a single output at output terminal of diplexer 43.
The power divided signal at terminal 21b of hybrid 21 is coupled via lead 33 to band-pass filter 45 in diplexer 41. The equal power 90 phase shifted signal at terminal 210 of hybrid 21 is coupled via lead 35 to band-pass filter 55 of diplexer 43. The one half power output signal at terminal 23b of hybrid 23 is coupled via lead 37 to band-pass filter 46 of diplexer 41. The equal power 90 relative phase shifted signal from hybrid 23 at terminal 23c is coupled via lead 38 to band-pass filter 56 of diplexer 43. The half power output signal from hybrid 25 at terminal 25b is coupled via lead 39 to bandpass filter 47 of diplexer 41. The equal power and 90 relative phase shifted signal at terminal 250 of hybrid 25 is coupled via lead 40 to band-pass filter 57 of diplexer 43. The half power output signal at terminal 27b of hybrid 27.is coupled to band-pass filter 48 of di plexer 41 via lead 36. The equal power 90 differential phase shifted signal at terminal 27c is coupled via lead 34 to band-pass filter 58 of diplexer 43.
In the operation of the device described in FIG. 1, the input signals 1 of frequencies from f tof which cover the operating frequency band of the system are coupled to the input power divider 13 wherein these signals are divided into four equal power sections and coupled to the respective filters 15, 16, 17 and 18. The filter passes frequencies from f to f to short slot hybrid 21. At the hybrid 21 the f to f frequency signals are equally power divided and with one portion undergoing zero or reference phase shift to terminal 21b and the other portion undergoing 90 differential phase through the short slot 22 in hybrid 21 to terminal 210.
The output at terminal 21b is coupled to band-pass filter 45 in diplexer 41 via lead 33. The 90 differential phase shifted signal at terminal 21c is coupled via lead 35 to band-pass filter of diplexer 43. Similarly, those signals at frequencies from f to f;, are coupled to short slot hybrid 23 and power divided such that those signals at the reference phase at hybrid terminal 23b are coupled to band-pass filter 46 of diplexer 41 and the 90 differential phase shifted signals at terminal 23c are coupled to band-pass filter 56 of diplexer 43. Those signals between frequencies f to f are coupled to short slot hybrid 25 with the one half power output at terminal 25b at reference phase coupled to band-pass filter 47 of diplexer 41 and those half power signals undergoing 90 differential phase shift being coupled out of terminal 25c to band-pass filter 57 of diplexer 43. The signals at frequencies between f and J2, are coupled out of band-pass filter 18 to short slot hybrid 27. The output signals at reference phase at terminal 27b of hybrid 27 are coupled to band-pass filter 48 of diplexer 41 and the differential phase shifted signals at terminal 27c are coupled to band-pass filter 58 of diplexer 43. As can be seen by reviewing the above, those signals which undergo the 90 additional phase shift are coupled to the diplexer 43 and the other signals of equal power but of reference phase are coupled to diplexer 41. The signals at the band-pass filters 45 through 48 are combined at power combiner 49 to provide one half the total output power at the reference phase at terminal 0,. The band-pass filters 55 through 58 are coupled to power combiner 59 wherein the other half of the total power at the frequencies from f tof are combined and applied to the output terminal 0 The power at terminal 0 should approximately equal the power at terminal O and be at 90 relative phase to the phase of the signal at terminal 0,.
A nearly circular polarized wave with a relatively low axial ratio of powers at the two terminals is achieved for example by coupling the output at terminal 0 to one terminal 9a of orthogonal coupler 9 and by coupling the other output at terminal 0 to terminal 9b of the orthogonal coupler 9 via attitude rotator 8. The orthogonal coupler 9 may be coupled at terminal 9c to a radiating horn antenna, not shown, whereby the circular polarized waves are radiated or received. The orthogonal coupler 9 may be a square section of waveguide (not shown) with the terminals 90 and 9b oriented to excite the output signal at terminal 0 in for example a TE mode and to excite the output signal at terminal 0 in the orthogonal TE mode. Metal irises (not shown) can be placed across the input of terminal 90 orthogonal to the electric field in the TE. to provide isolation of the two terminals 9a and 9b. A typical waveguide orthogonal coupler may be like that shown in FIG. 8 and described in connection therewith in U. S. Pat. No. 3,569,870 issued to Peter Foldes.
Input signals applied to terminal 1 in FIG. 1 undergo similar operation to that described above for input signals applied to diplexer 11. Input signals applied to terminal 1 of diplexer 11a are power divided at divider 13a with those signals from frequency f tof being coupled through filter 15a and lead 290 to terminal 21d of hybrid 21. Similarly, those signals at frequencies f to f at divider 13a are coupled through filter 16a and lead 30a to terminal 23d of hybrid 23. Signals at frequencies f tof, at divider are passed through filter 17a and lead 31a to terminal 25d of hybrid 25. Signalsat frequenciesf, tof at divider 13a are passed through filter 18a and lead 32 to terminal 27d of hybrid 27. The operation of the hybrids 21, 23, 25 and 27 and diplexers 41 and 43 is similar to that described above with the output at terminals 0 and 0 being of equal power at 90 relative phase but in this case the output at terminal 0 undergoes the additional 90 phase shift and the output at terminal 0 is at reference phase. This is due to the fact that the signals which are ultimately coupled to diplexer 41 are coupled through the slots in each of the hybrids 21, 23, 25 and 27.
As mentioned previously, it is desirable that the device be reciprocal. It can be seen that by making the power dividers and power combiners identical by having them both with the filters at the input and output terminals of the hybrids, reciprocal operation is provided. For example, signals applied at output terminal 0, of diplexer 41 can also undergo the frequency division of the signals corresponding to f to f ,f to f ,f tof, andf, to f, and be applied to the corresponding hybrids 21, 23, 25 and 27. Since the hybrids are symmetrical, the two output signals from each of the hybrids are of equal power with 90 relative phase shift between the two output signals. Diplexer 11 in the example combines the signals of reference phase and the diplexer 11a combines the signals having the additional 90 phase shift. Also, it is necessary that these hybrids 21, 23, 25 and 27 at either end see a similar match. This is provided by having similar band-pass filter sections coupled at each terminal of a given hybrid.
Turning to FIG. 2, there is illustrated the construction of a portion of such a wideband hybrid system. Only two diplexer sections and the multiple hybrid section is illustrated in the assembly 61 shown since the remaining two diplexer sections (not shown) of the assembly 61 are identical in construction to the first two diplexers. Waveguide assembly 61 as shown in FIG. 2 is made up of two waveguide sections 63 and 64 each sharing a common narrow wall 65. The waveguide section 63further includes-broad walls 67 and 69 and narrow wall 70 opposite common wall 65. Thewaveguide section 64 includes opposite broad walls 71 and 73 and narrow wall 75 opposite common wall 65. The top walls 67 and 71 are formed by one continuous conductive plate and the bottom walls 69 and 73' are formed 81 at these apertures. At the hybrids 92, 93, 94 and 95 the signals are power divided with the outputs from the two output terminals of each hybrid being substantially 90 out of phaseand of substantially equal power. The outputs from the hybrids 92, 93, 94 and 95 are coupled to a structure (partly shown) which is a continuation of waveguide sections 63 and64. The remaining structure by one continuous conductive plate. The waveguide section 63 is power divided into four equal rectangular waveguide sections by three plates 77, 78 and 79, which are placed parallel to each other. and parallel to walls 69 and 67. Similarly, plates 81, 82 and 83 are placed within waveguide section 64. The input signal applied to waveguide 63 is then power divided by a factor of four into separate waveguide sub-sections formed between the plates 77, 78 and 79 and between plate 77 and wall 67 and between plate 79 and wall 69.
The input signals coupled to the input of waveguide section 64 are power divided between the plates 81, 82
and 83 and between the plate 81 and wall 73 and be-- tween broad wall .71 and plate 83. By placing tuning stubs or irises 91 in the sub-sections between the plates and the broad walls, the waveguide sub-sections formed between the plates and between the plates and the broad walls of thewaveguide can be 'made to pass different frequencies and'thus'ly pro'vide frequency separation. In the arrangement shown in FIG. 2, the irises 91 are placed within thesesections to form band-pass filters forpassing, for example, at the top waveguide sub-section 63a formed between wall 67 and plate 77,
' a band-pass filter at f, to f frequencies. Similarly, the
sub-section 63b formed between the plates 77 and 78 passes frequencies from f, to f;,, the sub-section 63c between plates 78 and 79 passes frequencies from f to f and the sub-section 63d formed between plate 79 and wall 69 passes frequencies from f to f Similarly, the band-pass filters at frequencies f, to f f to f f to f, and f, to f are provided by thewaveguide sub-sections 64a, 64b, 64c and 64d having appropriately placed is similar to that shown at the input but is symmetrically arranged so that the outputs of the hybrids are coupled to the band-pass filter sections includingthe plates and irises and the output of'the filter sections is coupled to the undivided waveguide section to form a combiner. The filter section coupled to each terminal of each hybrid is made substantially the same.
Numerous and varied other arrangements within the sphere and scope of the principle of the invention will have occurred to those skilled in the art. The general principles of the invention are, for example, readily applicable to systems employing two or more hybrids and corresponding band-pass filters and power dividers. Power division can be up to any n number of sections with nband-pass filters and n hybrids to achieve the desired minimum phase and amplitude error through such 'hybrids. In the configuration using only two such hybrids,-"four diplexers' and an orthogonal c0uple'r,an
axial ratio on the order of 0.35 db is achieved in the 3,700 to 4,200 MHZ 'fre quencyjband.
What ,is claimed isi v 1. A system for providing substantially equal power splitting and 909. relative phaseshiftof power divided signals over a given relatively wide band of frequencies with reduced amplitude and phase error comprising:
afirst diplexer responsive to signals of said given wide band .of frequencies at its input for separating said signals by frequency to provide at a plurality of first diplexer output terminals signals within different narrow frequency bands where the sum of aid narrow frequency-bands covers the frequency spectrum of said given wide band of frequencies, plurality of quadrature hybrids, each hybrid coupled to a different one of said plurality of first diplexer output terminals and adapted to provide equal power splitting to first and second hybrid output terminals with signals at the first hybrid output terminal undergoing less phase shift than the signalsat the second hybrid output terminal with minimum error over the coupled relatively narrow frequency band,
-a second diplexer coupled to said first hybrid output terminal 'of each of said plurality of hybrids and being'responsive to said signals within each of said 7 narrow frequency bands for providing at the second diplexer output terminal wide frequency band signals of a given power level and phase,
a third diplexer coupled to the second hybrid output terminal of each of said plurality of hybrids and being responsive to said signals within each of said narrow frequency bands for providing at the third diplexer output terminal said wide frequency band signals of a power level substantially equal to said given power level and at 90 relative phase to said given phase.
. 2; A wideband polarizer for providing circularly polarized waves from linearly polarized waves over a given wide band of frequencies with low axial ratio comprising:
a first diplexer responsive to the linearly polarized signals over the given wide band of frequencies at its input for separating said linearly polarized signals by frequency to provide at a plurality of first diplexer output terminals linearly polarized signals within different narrow frequency bands where the sum of said narrow frequency bands covers the frequency spectrum of said given wide band of frequencies,
a plurality of quadrature hybrids, each hybrid coupled to a different one of said plurality of first diplexer output terminals and adapted to provide equal power splitting to first and second output hybrid terminals with linearly polarized signals at the first hybrid output terminal undergoing 90 less phase shift than the linearly polarized signals at the second hybrid output terminal with minimum error over the coupled relatively narrow frequency band,
a second diplexer coupled to said first hybrid output terminal of each of said plurality of hybrids and being responsive to said linearly polarized signals within each of said narrow frequency bands for providing at the second diplexer output terminal wide frequency band linearly polarized signals of a given power level and phase, .7
a third diplexer coupled to the second hybrid output terminal of each of said plurality of hybrids and being responsive to said linearly polarized signals within each of said narrow frequency bands coupled thereto for providing at the third diplexer output terminal said wide frequency band linearly polarized signals of a power level substantially equal to said given power level and at relative phase to said given phase,
an orthogonal coupler having a first terminal coupled to the second diplexer output terminal and an orthogonally oriented second terminal coupled to the third diplexer output terminal and responsive to linearly polarized signals for providing circularly polarized waves over said wide band of frequencies with substantially low axial ratio.
3. The combination claimed in claim 2, wherein said 4. The combination claimed in claim 3 wherein all of the band-pass filters coupled to a given one of said hybrids are substantially identical.
5. The combination claimed in claim 2, wherein said hybrids are short slot hybrids. Y
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|U.S. Classification||333/135, 333/21.00A|
|International Classification||H01P1/17, H01P1/213, H03H7/46, H01P1/20, H01P5/16, H01Q1/00, H03H7/00, H03H7/21, H01P1/165|