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Патент USA US3092797

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June 4, 1963
Filed March 14, 1958
H6. 4HUGH c
Patented June 4, 1963
Hugh C. Hanks, Jn, Towson, Md., asslgnor to Martin
Marietta Corporation, a corporation of Maryland
Filed Mar. 14, 1958, Ser. No. 721,556
3 Claims. ((11. 333-11)
being proportional to the magnitude of the applied mag
netic ?eld. This rotation of the E vector causes a portion
of the coupled electromagnetic energy to be re?ected back,
the amount of energy thus re?ected being proportional
to the degree of E vector rotation. In this way, a selected
proportion of electromagnetic energy may be coupled at
will, the remainder being re?ected back. The limiting
condition exists when the magnitude of the magnetic ?eld
The present invention relates to apparatus for selec
tively switching electromagnetic energy within an elec
is su-fdcient to cause the E vector to rotate exactly 90°,
trical waveguide system, and more particularly to such 10 at which time the total amount of energy is re?ected back
apparatus wherein the switching is e?ected electronically
into the input waveguide section and no coupling at all
as distinguished from mechanical methods.
takes place. It can thus be seen that in a system as pro
The invention has for its principal object the control
vided by the invention selective switching can be effected
of the propagation of electromagnetic energy in a wave
by conventional electronic means designed for switching
guide system such that the energy may be selectively di 15 and controlling the magnitude of the separate magnetic
rected to one or more of a plurality of output terminals
?elds applied to the ferrite coupling elements.
and selectively divided therebetween. Heretofore control
In the above description the application of the magnetic
switching has been accomplished mechanically. This type
?elds limits or prevents the coupling of electromagnetic
of control suifers from the following disadvantages: (a)
energy. However, the waveguide system of the invention
a long switching ‘cycle, (1)) frequent and large mismatches 20 may be designed so that the opposite is true. In such ar
during a switching cycle, and (c) a physically large size.
The present invention provides apparatus for electronic
rather than mechanical switching of electromagnetic en
rangement the waveguide sections are physically rotated
through an angle or" 90“ relative to one another so that
no energy is ordinarily coupled from one to the other.
ergy within a waveguide system. This apparatus has none
The E vector rotation caused by the magnetic ?elds then
of the above-listed disadvantages and further permits a 25 effects a coupling of electromagnetic energy rather than
large latitude in design con?guration.
a re?ection as hereinbefore. Again the limiting condi
It is well known that in order for electromagnetic en
tion, in this case the total coupling of energy, will take
ergy to be coupled from one waveguide section into an-'
place when the magnetic ?eld is of such intensity as to
rotate the E vector through an angle of 90°.
other the latter waveguide section must have a dimension
in its H plane which is at least one-half of the wave
Due to the nature of the present invention extremely
length of the propagated electromagnetic energy, and, in
rapid waveguide switching may be effected by means of
addition, the electromagnetic energy entering the latter
conventional electronic equipment designed to selectively
Waveguide section must be properly oriented. Such cou—
apply a separate magnetic field to each of the ferrite
pling has successfully been effected in the past by the use
elements in the waveguide system. For this reason the
of ferrite elements. it has now been found that ferrite 35 present invention may be advantageously employed for
elements also provide means for electronically switching
switching between a plurality of antennas and either a
electromagnetic energy within a waveguide system.
transmitter or receiver circuit. For example, by means
According to the invention waveguide switching is
of the invention the transmitter or receiver circuits may
e?ected by ?rst providing a waveguide system having a
be rapidly switched from- one antenna to another. Fur
common input waveguide section for the propagation of
ther, the invention may be employed to selectively divide
the electromagnetic energy. An impedance element is
electromagnetic energy among the plurality of antennas.
electrically associated with this input waveguide section
Also, rapid scanning of the antennas may be obtained by
to urge the electromagnetic energy therethrough in a given
the provision of appropriate sequential switching means.
direction. A plurality of output waveguide sections may
Other advantages of the invention deriving from its elec
then be separately connected into the input waveguide
tronic nature are no moving parts and a theoretically
section. Each output waveguide section is provided with
unlimited number of output sections.
means adapted to couple the electromagnetic energy ‘from
The invention can best be understood by referring to
the common waveguide section thereinto. The electronic
the following drawings in which:
switching may then be effected by mounting a separate
‘FIG. 1 is a plan view of multiplex switching apparatus
ferrite element in each of the output waveguide sections.
in accordance with the invention;
Further, means are provided for selectively applying a
FIG. 2 is a section taken along line 2—2 of FIG. 1;
separate magnetic ?eld parallel to the axis of each of the
FIG. 3 is an alternative embodiment of waveguide
output waveguide sections and to the ferrite element there
switching apparatus in accordance with the invention
shown in plan view;
The selective application of magnetic ?elds to the fer 55
FIG. 4 is a section taken along line 4—4 of FIG. 3.
rite element within the waveguide system of the invention
Referring ?rst to the embodiment of FIGS. 1 and 2,
provides electronic waveguide switching which may be
electromagnetic energy from a waveguide system is con
rapidly controlled both as to the selection of the output
nected into a common waveguide section 1. The wave
waveguide sections into which electromagnetic energy is
guide may be of any conventional shape such as cir
to be coupled, and as to the division in magnitude of the
cular, ridged, or, as shown, rectangular. An impedance
electromagnetic energy between the selected output wave
element is electrically associated with the common wave—
guide sections and the common input section. This is ex
guide section to urge the electromagnetic energy there
plained by noting the effect a magnetic ?eld has on the
through in a given direction as shown ‘by the arrows.
coupling by a ferrite element of electromagnetic energy
The impedance element is illustrated schematically in
from one waveguide section into another wave guide sec 65 FIG. 1 as resistor 2.
tion. For example, assume the waveguide sections are
Normally the electromagnetic energy would propagate
oriented such that the ferrite element provides a high de
gree of coupling. With the establishment of a magnetic
undisturbed through the common waveguide section in ac
gated may be caused to rotate, the amount of rotation
mon waveguide section into any one or more of a plu
cordance with Maxwell’s equations. It is the object of
?eld about the ferrite element, the E vector, that is, the
the present invention, however, to provide apparatus which
electric ?eld, of the coupled electromagnetic energy propa
is capable of selectively switching energy ‘from the com~
rality of output waveguide sections. To this end the
desired plurality of output waveguide sections N (in this
case N=3) are separately connected into the common
?elds. Thus if the direction of either ?eld is reversed,
the direction of travelis also reversed.
The application of an external magnetic ?eld parallel
waveguide section. These output sections are identi?ed
to the axis of a ferrite element causes the propagated
electric ?eld coupled through the ferrite element to
rotate. The amount of this rotation is proportional to
Each of these output waveguide sections comprises a
the magnitude of the magnetic field applied. In this
conventional waveguide 3 and an intermediate waveguide,
way, the electric ?eld may be made to rotate through
shown generally at 4. The intermediate waveguides are
an angle of exactly 90° by the application of a magnetic
connected to the waveguide Sby means of bolted ?anges
?eld of the proper magnitude. A 90° rotation is the
and to the common waveguide section 1 by solder. The
limiting condition at which 'no coupling through the
intermediate waveguides also include ferrite element 5
ferrite element into the rectangular output waveguide
which extends into the common waveguide section 1
section associated therewith can take place. Rather,
through the intermediate waveguide 4, into the wave
with an angle of rotation of 90° the electromagnetic
guide 3. Advantageously a Te?on bushing 6 may be
provided in order to insulate the ferrite element 5 from 15 energy propagating through the ferrite element is
caused to reverse its direction and return back through
the metallic portions through which it passes. In the
the ferrite element. In returning through the ferrite
embodiment of FIG. 1 the ferrite element is made rod
element the electric ?eld undergoes another 90° rotation
shaped of circular cross-section and is mounted in axial
thereby undergoing a complete rotation through 180° en
alignment with waveguide section 3. Further, the fer
rite element passes coaxially through a circular hollow 20 abling the electromagnetic . energy to be coupled back
into the input waveguide section. In this way the inter
cylinder 7 ?lled with the Te?on insulating bushing thus
mediate waveguide 4 may be designed so as to effectively
forming, in e?ect, a circular waveguide section.
set up a gate blocking passage of electromagnetic energy
Each ferrite coupling arrangement according to the in
into the output waveguide section. The design consider
vention performs two functions, coupling and gating.
First, it couples electromagnetic energy from the com 25 ations determining the angle of rotation of the propagated
electric ?eld are the length of the ferrite element and the
mon waveguide section into the output waveguide sec
by the letters A, B, and C.
tion of which it forms a part. This results from the pro
trusion of the ferrite element 5 into the common wave
magnitude of the applied magnetic ?eld; therefore, the
shorter the ferrite element the greater the ?eld required.
It will thus be seen that, with this arrangement accord
The ferromagnetic properties of the
ing to the invention, the accomplishment of the desired
ferrite elements effect a perturbation of the electric and 30. switching within the waveguide system is a matter of
magnetic ?elds of con?guration within the common wave
selectively applying magnetic ?elds of proper magnitude
guide section. The coupling then is a combination of
to the ferrite elements 5. This selective application may
both electric and magnetic phenomena and is a func
be advantageously effected by providing the separate
tion of (l) the depth of insertion of the ferrite element
electromagnet ‘8 for each ferrite element with a separate
into the common waveguide section, and (2) the diameter
connection through an on-off switch 9 to a power
of the ferrite element.
supply 10. In this way one or more of the electromag
Ordinarily the electromagnetic energy would thus be
nets may be energized thereby to selectively control the
diverted from its course down the common waveguide
switching of electromagnetic energy from the common
sectionrinto' the output waveguide sections by the cou
40 waveguide section into the output waveguide sections.
pling effected in the ferrite elements 5. However, the
The waveguide switching operation is therefore ac
second function of the intermediate waveguide 4 is to
complished in the following manner. As energy prop~
control this ferrite coupling phenomenon. Such control
agates down the common waveguide section it is inter
guide section.
is accomplished ‘by gating means which either permit the
coupled electromagnetic energy to propagate along the 45
output waveguide section or prevent it from so» doing.
This gating is e?ected by means for selectively apply
ing a separate magnetic ?eld to reach of the ferrite ele
ments. Advantageously such means comprises a sepa
rate electromagnet 8 for each output waveguide section. 0
Each of these magnets is so arranged and adapted as
to apply a predetermined magnetic ?eld parallel to the
axis of its output waveguide section and to the ferrite
element therewithin. In this particular embodiment the
electromagnet is arranged about the circular waveguide
section 7 in coaxial relationship therewith so as to ap
ply a magnetic ?eld parallel to the axis of the ferrite
element 5. The gating is then effected by the phenome
non of Faraday rotation which results from the appli
cation of a magnetic ?eld to a ferrite element in the di
rection of the propagation of electromagnetic energy
therethrough. In order for Faraday rotation to take
place, however, the output waveguide sections must be
rupted in its course by the coupling in?uence of the ?rst
ferrite element 5 associated with output waveguide sec
tion A. This coupling tends to urge the electromagnetic
energy from the common waveguide section into wave
guide section A. With the switch 9 open no gate is set
up to prevent the energy from traveling down the ferrite
?lled circular waveguide 4 into the waveguide 3. Thus,
the electromagnetic energy is switched into output wave
guide section A when switch 9 is in its open position.
The insertion loss resulting from this switching opera
tion is dependent upon the following three functions:
(1) the coupling e?’iciency from the common waveguide
section to the ferrite element, (2) the loss caused within
the ferrite element, and (3) the coupling e?iciency from
the ferrite element into the output waveguide section.
The ?rst function is controlled by the diameter of the
ferrite element and the depth of insertion of the ferrite
element into the waveguide. The loss within the ferrite
element is primarily -a function of the type of ferrite
and can be minimized by keeping the length of the ferrite
element as short as possible.
limited to a rectangular cross-section con?guration. A
Assume, however, that it is desired to propagate the
wide variety within such limitation is permissible, how 65 electromagnetic energy ‘through common waveguide sec
ever, such as, for example, ridged rectangular and the
To explain Faraday rotation it must be recognized
that electromagnetic enegry propagating in a wave
guide comprises an electric ?eld and a magnetic ?eld
oriented at right angles to each other and also at right
angles to the direction of travel. In addition, the direc
tion of travel of the energy in a waveguide depends
upon the relative direction of the magnetic and electric 75
tion 1 without being coupled into the output waveguide
section A. It then becomes necessary to prevent the'pas
sage of energy into section A by closing the gate within
the intermediate waveguide 4. This is e?‘ected by clos
ing the switch 9 to apply the magnetic ?eld from electro
magnet 8 to the the ferrite element 5. The energy tend
ing to travel down the ferrite ?lled waveguide is thus
re?ected back into the common waveguide section 1.
Without any preliminary design adaptation in,‘ the
common waveguide section 1 the electromagnetic energy
from section A might travel in either direction upon
being re?ected back into the common waveguide sec
tion. The division which would thus result may be
of several antennas to either transmitter or receiver de
vices. In such application any one or more of the
antennas may be selectively switched to the receiver or
prevented, however, by designing the common waveguide
section such that the impedance seen by the re?ected
electromagnetic energy is lower in the desired direction
of travel. Such design has been shown schematically in
transmitter. Further, the antennas may be rapidly
scanned by the provision of sequential means for switches
9 for the selective application of the separate electromag
netic ?elds. Or, if desired, a division of the electromag—
netic energy between the antennas may be provided by
FIG. 1 by the impedance symbol 2.
the control devices 20.
The switching procedure above described is, of course, 10 It should be noted that the present invention may be
also applicable to the other output waveguide sections
operated with the output waveguide sections 3 oriented
B and C. It should be noted at this point that this
switching can be made reciprocal with respect to the
with respect to the input waveguide section 1 such as to
block or partially block the passage of electromagnetic
energy therebetween. For example, if the output wave
inputs and outputs. That is, energy may be applied
through any one of the waveguide sections A, B, or C 15 guide sections were physically rotated through an angle
into the common waveguide section and then coupled
of 90° from that position illustrated in FIGS. 1 and 2,
selectively into the remaining output waveguide sections.
they would be so oriented as to make impossible the cou
pling of electromagnetic energy from one waveguide sec
tion into another. In that event the closing of switches
another to effect the switching of electromagnetic energy 20 9 would effect an ‘opposite reaction than that described
by electronic rather than mechanical methods.
hereinbefore. That is, the application of a magnetic ?eld
In addition to the advantages of selective electronic
would effect a rotation of the electric ?eld vector of the
Thus the electromagnetic energy within the common
waveguide section may be switched from one output to
waveguide switching hereinbefore described, the inven
tion further provides the means for effecting a division,
propagated electromagnetic energy so as to permit cou
pling into the output waveguide section rather than to
in magnitude, of the electromagnetic energy propagated 25 prevent it as in the embodiment of FIG. 1. Of course,
through the common waveguide section 1 among one or
more of the output waveguide sections. This additional
feature results from the determination that the degree of
any arrangement of the output waveguide sections inter
mediate to a complete 90° rotation relative to the ar
rangement of FIG. 1 is also included within the scope
of the invention.
rite element is proportional to the magnitude of the ex 30
It should also be noted that gating within the output
ternal magnetic ?eld applied thereto. Further, the per
waveguide sections of FIGS. 1 and 2 may also be effected
centage of the total electromagnetic energy re?ected
by a phenomenon alternative to Faraday rotation and
back into the input waveguide section varies in propor
denoted as waveguide cutoff. This phenomenon also
tion to the degree of rotation of the electric ?eld. Thus,
results from the application of a magnetic ?eld to the
by the provision of means for selectively controlling 35 ferrite elements 5. However, in order for the phe
the magnitude of the magnetic ?eld applied to the sep
nomenon of waveguide cuto?? to occur, the magnetic ?eld
arate ferrite elements, division of the magnetic ?eld with
applied to the ferrite elements must be substantially
in well-de?ned limits may be effected.
greater {than that which is applied to e?ect Faraday rota
For example, 50 percent of the energy of the input
tion. This is due to the fact that to produce a wave
rotation of the electric ?eld propagating through the fer
waveguide section may be coupled into output waveguide 40 guide beyond cutotf condition enough energy is required
section A by controlling the intensity of the magnetic
to disturb the electric and magnetic con?guration Within
?eld applied to fern'teelement 5 so as to eifect a 45°
the waveguide to such an extent that the waveguide is
no longer capable of supporting the propagation of
Correspondingly, however, a 60 db reduction
the input waveguide section thereby effecting the desired 45 energy.
of energy may be obtained by the use of a waveguide
division. Thus, by controlling the magnitude of the mag
beyond cutoff condition compared to the 30 db reduction
rotation of the E vector. In this war, only 50 percent
of the electromagnetic energy will be returned back to
netic ?eld so as to cause rotation of the E vector be
tween zero and 90°, any level of energy transfer between
0 percent and *1 00 percent can theoretically be achieved.
of energy produced by Faraday rotation. Further, the
use of the waveguide cuto? phenomenon permits the
output waveguide sections to employ con?gurations other
Control of the magnitudes of the separate magnetic ?elds 50 than rectangular as is required in the case of Faraday
may be e?ected by the provision of conventional elec
tronic potentiometer control elements 20 connected to the
FIGS. 3 and 4 illustrate an alternative embodiment of
output of the power supply 10 and separately connected
the invention which permits greater control over the divi
in each one of the electromagnet lines.
sion of energy in the common waveguide section as de
A waveguide switch similar to that of FIGS. 1 and 55 scribed
above. The apparatus again comprises a com
2 was built and tested over the frequency range of 9.l-—l0
mon waveguide section 1 and output waveguide sections
kmc. The intermediate waveguide section was designed
A, B, and C. This embodiment idi?’ers primarily in the
to operate above 8.8 kmc. Tests were run to determine
for coupling electromagnetic energy from the
the insertion loss and impedance as a function of (l)
common waveguide section 1 into the output waveguide
the insertion distance of the ferrite element into the com 60
sections. As shown by the ?gure no intermediate wave
mon waveguide section and (2) the impedance 2 in the
guide is employed to effect the coupling as was done in
form of a termination for the common waveguide section.
the embodiment ‘of FIG. '1. Rather, the output Wave
A series of terminations were used including (1) matched
guide sections are connected ‘directly to the common
load, (2) a short circuit, (3) an open circuit, and (4) an
optimum load. These tests veri?ed the recited advan 65 waveguide section 1. Coupling is eifected by means of
ferrite elements 11, preferably slab shaped, mounted with
tages of the multiplex switch of this invention.
the common waveguide section and separated there
Further advantages of the invention derive from the
from by Te?on insulation v12'. Each of these ferrite ele
electronic nature of the waveguide switching thereby
ments 11 is individually associated with a separate output
eiiected. The electronic switching results in the elimina
waveguide section and is mounted beside the waveguide
tion of moving parts, the ability to have as many output 70 section associated therewith. A separate coupling elec
waveguide sections as is desired, the ability to divide the
tromagnet ‘12 is provided for each of these coupling
electromagnetic energy in magnitude, and further, the
ferrite elements 11. The electromagnets are so posi
provision of extremely rapid switching speeds. The latter
tioned as to apply a predetermined magnetic ?eld parallel
two advantages make the waveguide switching system of
to the axis of the common waveguide section and to the
the invention particularly advantageous for the switching
ferrite elements associated therewith. Each electromag
I claim:
netic and ferrite element combination forms a coupling
unit. These are labeled A’, B’, and C’, respectively, to
designate their association with the correspondingly
1. Apparatus for’ selectively ‘switching electromagnetic
energy'within a waveguidegsystem, comprising a common
input Waveguide section for supporting propagation of
labeled output waveguide sections.
‘electromagnetic energy therethrough, a- plurality of out—
put waveguide sections" each having a substantiallly rec
tangular cross-section, a plurality of circular waveguide
sections each mounted for electromagnetically. coupling
Coupling into an output waveguide section by means
of these coupling units is accomplished in the following
manner. As energy propagates down the common wave
guide section it approaches the coupling ferrite element
a respective one of .said output waveguide sections to
11 of unit A’. If the electromagnet 12 associated there
with is unenergized the electromagnetic energy will pass 10 said common input- waveguide section, a plurality of
rod-shaped ferrite elements, each of said ferrite elements
on beyond this point. Energization of the electromagnet,
having a circular cross-section and being coaxially mount
however, causes the electric and magnetic ?eld con?gura
:ed in a respective one of said circular waveguide sections,
tion within the common waveguide section to change
each said ferrite element projecting into said common
such that propagation is no longer permitted in the for
.’ard direction at that point. By proper placement of 15 waveguide section to provide coupling electromagnetic
the ferrite element 11 as described above, the electro
magnetic energy may be turned into the output waveguide
energy thereform' into, the associated said circular wave
guide section, and means for selectively applying a
section A to e?ect the desired coupling. This same cou
V magnetic ?eld parallel to the axis of each said circular
pling procedure is also applicable for the units 13' and C’
associated with the output waveguide sections B and C,
respectively. To enable selective coupling through this
medium each electromagnet 12 is separately connected
waveguide, section and to the said ferrite element there
within, said magnetic ?eld having a magnitude su?icient
for causing Faraday rotation of the electromagnetic
energy coupled by the said ferrite element associated
therewith, thereby to selectively control the switching
and power division ‘of electromagnetic energy from said
Further control ‘of the waveguide switching is provided
by the positioning of separate gating ferrite elements 15 25 common waveguide section into said output waveguide
sections, the amount of electromagnetic energy coupled
in each of the output waveguide sections. These ferrite
to a switch 13 to a power supply 14.
elements are mounted within the output waveguide sec
tion by Te?on insulation 16. A separate gating electro
magnet 17 is provided for each of the gating ferrite
from said common waveguide section to said output
waveguide sectionsbeing a function of the intensity of the
parallel magnetic ?eld applied to said ferrite element.
2. Apparatus in accordance with claim 1 in which
eachof said. output waveguide sections is orientated with
respect to said input waveguide section for presenting
waveguide cut-off to the electromagnetic energy propa
gated in said input waveguide section until said magnetic .
35 ?eld is applied to the said ferrite element‘ associated
into operation.
The gating ferrite elements 15 have the same effect as
3. Apparatus in accordance with claim 1 in which
do the coupling fer-rite elements 11 in that when energized
each of said output waveguide sections is oriented with
they render the output waveguide sections unilateral as
respect 'to' said input waveguide section for coupling
far as the propagation of electromagnetic energy there
electromagnetic energy there-between whenever the said
through is concerned. Thus, energy coupled thereinto
magnetic ?eld is removed from the said ferrite element
by means of the coupling units may be rejected or passed
on depending upon the position of the switch 18. In
associated therewith.
operation then the apparatus of FIGS. 3 and 4 may be
References Cited in the ?le of this patent
operated to effect selective multiplex switching by the
use of switches 13 and 18. Further, the unit is recipro
cal in nature in that energy may be applied through any
Rigrod ______________ __ Aug. 17, 1954
one of the output waveguide sections rather than the
elements and is mounted and arranged so as to apply a
magnetic ?eld parallel to the axis of the output wave
guide section and to the ferrite element associated there
with. Separate switching means 18 are also provided
so that each electromagnet may be selectively switched
common waveguide section.
In that event, the energy
introduced through the output waveguide section may be
urged in either direction in the common waveguide 50
section by the selective energization of the coupling units
through switches v13. The coupling units therefore
effectively function as the impedance 2 of FIG. 1.
Preferred embodiments of the invention have been
described. Various changes and modi?cations may be 55
Luhrs ______________ __ Sept. 27, 1955
Hewitt ______________ __ May 8, 1956
Hogan __________ __'_____ July 2, 1957
Hewitt ______________ __ Jan. 20, 1959
Garoff ______________ __ Oct. 13, 1959
r 2,961,658
Spencer ______________ __ Nov. 22, 1960
made in the scope of the invention as set forth in the
Theory and Application of Ferrites, Soohoo, Prentice
HallElectrical Engineering Series, 1960, pages 9, 119 and
appended claims.
12.0 of interest. TK7870/ S 55.
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