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Патент USA US2407069

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Sept 3,1946-
M.A D. FlsKE
DIELEÓTRIC lWAVE GUIDE SYSTEM
` Filed Sept. 15, 1942
42,407,069
2 Sheets-Sheet l
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Inventor:
Milan D_Flfske,
b WM¿2W
y His Attorney.
Sept¿ 3,. 1_946.
M. D. FlsKE
2,407,069
' DIELECTRIC WAVE yGUIDE SYSTEM
méd sept'. 15, 1942
2 sheets-sheet 2
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Inventor. ,
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Mììa'n>~ D. Fiske,
by ß/w-«fáßwßm >
Patented Sept. 3, 1946
2,407,069
i.
UNITED- STATES PATE-NT ÜFFICE»
2;40t',`ò69
`
manicomio-,WAVE Gurus SYSTEM
Milan D.. Fiske, Schenectady„ .NL Yy, assi'gnor to
General' Electric' Company, a' corporation of‘New
York
Application September 15, 19.42;v S'erialfNo; 4583423
14' Claims. (Cl. 17d-44)'
2
My invention relates- to dielectric wave guides,
of the hollow-pipe type for transmitting electro
magnetic waves of ultra high frequency,` andV
more particularly to structures associated there
with for selectively controlling the propagation
of electromagnetic waves through the- guides.V
t is now quite generally appreciated thaty elec
tromagnetic waves vmay be propagated through
the interior of a hollowv pipe type guide which
may be constructed of a conductive'materialand
which contains a dielectric medium> such as air
or a` gas through which the energy of the Waves
is transmitted. Of course, the frequency ofthe
exciting» electromagnetic waves must be greater
than the critical minimum frequency established,
by the dimensions, principally the‘transverse> di
the intensity thereof exceeds a. predetermined
value.
Itis a, further object of my invention to pro
vide a-.new and improved'resonant structure as
i sociated with ay dielectric wave guide which is
highly responsive tothe magnitude of the excit
ing electromagnetic waves.
_ Itis a further object of my invention to pro
vide-:anew and-,improved resonant` aperture with
in- a metallic.> wall». enclosed within or associated
with` a wave guide of the dielectric type, and
which is enclosed within an atmosphere, such
as a gas, at low pressure.
e `Ity is a still further object of my invention to
`provide new and improved arrangements for con'
trollingl‘or adjusting the natural resonance fre
mensions of the guide.
There may bey placed within the interior` of a
dielectric guide a» metallic wall having an aper
quencyI of. an~ aperture mounted within av hollow
pipe wave guide of the dielectric, type.
It is aistill further object of my invention to
prov-idea new and.' improvedV assembly for main
ture which is- tuned to the frequency of the excit
ing waves‘to effecta concentration of thev poten
taining a. resonant aperture in a dielectric wave
guide in Yan atmosphere ofv desired pressure, and
tial due tothe waves within or across a substan
tially small dimension of the aperture. As the
intensity or the magnitude of the exciting elec
tromagnetic waves is increased, the magnitude of
the potential diiference appearing between op
posing surfaces of the aperturel is also increased,
and when the magnitude of this potential dif
ference increases to a predetermined Value estab
lished by the configuration of the aperture and
the dielectric strength of the medium surround
ing the aperture, an electric dischargey is estab
lished across thev aperture thereby materially
changing th'e propagation characteristics of the
which is proportioned. so that the reflection of
the electromagnetic waves. is reducedA to a mini
mum throughout that range ofV intensities within
which. it is desired, to. propagate the waves.
Briefly stated, in the illustrated' embodiments
of my invention I provide a metallic wall having
an enclosed resonant aperture,` such Yas a reso
nant slot, tun'ed substantially to’ thefrequency of
the exciting electromagnetic Waves and which is
designed to effectv a; breakdown of the surround
ing atmosphere in the' event the intensity >of‘ the
electromagnetic waves attains or“ exceeds a pre
guide.
i
t
to Ul determined vallue. The" presence ofthe electric
discharge across the slot varies the effective di‘
Oneway in which a structure of this nature
electric constant" ofV the dielectric medium
may be employed is in connection with a system
through which thev electromagnetic waves are
which is subjected to electromagnetic waves of ‘
propagated, thereby changing the wave guide
considerable range of intensity and utilizingV the
from a propagator1to> an attenuator of the elec
characteristics of the aperture to effect trans
tromagnetic Waves;
mission or attenuation> of the Waves within the
guide.
,
,
l
.
>
Itis an object of my invention to provide a new
and impro-ved dielectric wave guide of’the'hollow‘
pipe type and associated structure whereby `thel
-
a new and improved structure, such as a reso
nant slot or aperture associated with the dielec
tric guide tuned to the frequency of :the excit
ing waves, and which is designed to. prevent the
l
a vitreous dielectric material, such as glass,
which may have various configurations. The ‘di
attenuation thereof `within the guide may beV
It is another object of my invention to provide
t
aperture'.` The sealing structure may comprise
transmission of electromagnetic waves or `the
selectively controlled.
`
More specifically, I provide structures for en
closing the resonantV aperture or structures or
for' sealing a- portion of the dielectric Wave guide
which is’ de'ñnedby the wall which comprisesthe
ì
electric material may be inthe form of a plate,` or
0 may- be` of' bulbous.- or liemìspherical form.
In
any case, theV dielectric material- is“ positioned
andproportioned so that .the reflection therefrom
l is substantially equal and >opposite to the reflec
tion produced'by thepresenc'e; ofthe wall and the
propagation of waves therethrough in the event 55 resonant aperture:
Stated in otner‘words, the
2,407,069
È
assembly including the wall and the sealing dl
electric is substantially re?lectionless.
In accordance with a still further teaching of
my invention, I provide a structure for housing
a tuned aperture in a dielectric wave guide and
which is sealed to maintain the aperture in an
atmosphere of low pressure, and which is also
provided with externally accessible adjusting
4
waves have both a longitudinal and a transverse
component of magnetic field but only a transverse
component of electric ñeld. Although my inven
tion is applicable to systems for transmitting a
great variety of waves, in describing my inven
tion hereinafter reference will be made particu
larly to the H01 type of wave.
Referring now to Fig. 1 of the accompanying
drawings, my invention is there illustrated as
means to`control or tune the aperture.
For a better understanding of my invention, 10 applied to a system including a hollow-pipe type
reference may be had to the following descrip
tion taken in connection with the accompanying
drawings, and its scope will be pointed out in the
wave guide of the dielectric type. The dielectric
wave guide may be of rectangular- cross section
formed by conductive material, such as copper
or brass, having a height a and a base dimen
appended claims. Fig. 1 diagrammatically illus-v
trates one way in which my invention may be 15 sion b. Electromagnetic waves are established
within the guide by suitable exciting electrodes
incorporated in a hollow-pipe dielectric wave
which may have various configurations, depend
guide, and Figs. 2 and 3 are views of the sealing
ing upon the nature of the excitation required
structure for the resonant aperture or slot. Figs.
or desired. One form which the input electrodes
4 and 5 diagrammatically illustrate another mod-`
iiication of my invention wherein the sealing 20 or exciting means may assume is that of a con
centric line including a tubular conductor I and
structure constitutes a dielectric window of plane
a conductor 2, the former of which is conductively
connected to the bottom of the wave guide and
the latter of which may be conductively connect
to the frame including the resonant aperture by 25 ed to the top. There is positioned within the
wave guide a metal wall 3, preferably constructed
means of a sealing ring having a temperature co
of copper or brass, and whichis provided with
eiiicient of expansion substantially equal to that
an aperture 4 having an appreciable dimension
of the dielectric material employed. Fig. '7 rep
transverse to the direction of propagation of
resents an assembly of the elements shown in Fig.
6, and Fig. 8 is a still further modiñcation where 30 electromagnetic waves through the guide. Where
the wave guide is excited by electromagnetic waves
in the enclosing compartment for the resonant
of the Hoi type, for example, the slot aiîords a
aperture comprises two bulbous type vitreous win
principal dimension transverse to the electric
dows mounted on opposite sides of the metallic
component of the electromagnetic ñeld and effects
wall. Fig. 9 diagrammatically illustrates a still
construction. Fig. 6 represents a further modi
ñcation of my invention wherein a bulbous vit
reous dielectric window may be attached or sealed
further feature of my invention wherein the res
onant element is provided with means for con
trolling its effective dimensions, the means being
externally controllable. Fig. 10 diagrammati
cally illustrates another manner in which exter
nally accessible means may be employed for con
trolling the natural resonance frequency of the
slot and wherein the adjustable means is posi
tioned so that it is not subjected to the electric ‘
a' concentration of the potential due to the wave
across the upper and lower edges of the slot.
This accentuation or concentration of the poten
tial due to the wave is effected by virtue of the
fact that the slot is tuned to the frequency of
the exciting waves. If desired, the resonant aper
ture may be of the conñguration illustrated
wherein an elongated slit 5 is provided with en
larged openings, such as circular openings 6 and
discharge when the magnitude of the waves ex
1; at each end thereof, and the complete opening
ceeds a predetermined value.
or aperture is tuned to be resonant at the fre
quency of the exciting waves.
The wall 3 and the associated dielectric window
-
Prior to a detailed description of the various
embodiments of my invention, it is believed that
it will be helpful to describe generally ,the typeof
system to which my invention is applicable. It
constitute one end of the sealed chamber or sec
tion of the dielectric wave guide, the other lon
is now understood that ultra high frequency elec- ,
tromagnetic waves may be propagated dielec- j
gitudinal end of such section being provided ‘by
have both a longitudinal and a transverse com
tromagnetic waves.
Where it is desired to seal a portion cf a di
the end wall beyond the concentric electrode
means l and 2. Oi course it is to be understood
trically through hollow-type guides where the
that the concentric line may be sealed in any
frequency of the exciting electromagnetic waves
conventional way so that the region between the
is greater than a critical minimum frequency
wall 3 and the end wall may be maintained at a
which, in turn, is determined principally by the
desired low pressure.
transverse dimensions of the guide. The guide
Where the principal transverse dimension of
is preferably constructed of a conductive mate
the aperture is perpendicular to the electric com
rial such as copper or brass.
‘
ponent of the electromagnetic iield, the dimen
Many types of high frequency electromagnetic
sions of a rectangular aperture may be calculated
waves may be transmitted dielectrically through
with reference to the dimensions a and b of the
hollow-pipe type guides. These waves have been
wave-guide. Generally speaking, as the eiiective
generally indicated heretofore as being of the E
dimension of the aperture transverse to the elec
and H types. subscripts, as indicated, Emu and
tric component of the field is increased, the fre
Hmm, have .been assigned to these waves in order
to indicate the nature of the waves, where n rep (16 quency to which the aperture is resonant is de
resents the order of the wave and m represents
creased. Furthermore, as the effective height of
the mode of propagation. The order of the wave
the aperture approaches zero, the effective length
of the aperture approaches the limit
is determined by the manner in which the ñeld
intensity varies circumierentially around the axis
A
of the guide, whereas the mode is determined by 70'
2
the manner of its variation with radial distance
where A is the `wave length of the exciting elec
from the axis of the guide. The E type waves
ponent of electric iield but only a transverse com
ponent of magnetic iield, whereas the H type 75 electric wave guide or to maintain the aperture
¿4075669
5
6
Within an atmosphere-at the'properfpressure
equi-valent electrical circuit of the aperture-»arid
order- to- effect al selective` response-in- accord4`>>-` ,
window-»is resonant at the frequency of’the- Wave»
propagated throughthe' -wave guide.V
ance-.i with the VAmagnitude l of the electromagnetic
Wavesebe'in'gltransmittedi I provide'a sealing-struc»
ture forV the aperture-*which performsA the seal-y
ing function'fwithout sacrificing the wave trans
mitt-ìng characteristics Y oi- the» guide. For exa-m
ple; inf Fig. I I provide a bulbous type dielectric
WindowI 8 for' theresonant‘aperture and which is
designed to neutralize substantially any' reflection
or“ discontinuity inthe wavev> propagating characteristics of; theA guide incidenti td the walls" and
theaperture 4’. Stat'ed‘- in other words, thej bul~
'bous dielectric window 8 produces an ell’ect'whifch`
is substantially equal and oppositeftoltliat ofi the
Wall! 3f and lehe- aperture so »that "theïaniountl‘of
energy reflected is‘minimi'zedf.
' `
‘
^ »Thee voltage or“ potentialidifference appearing
between the upper and lower edges of the aper» '
turefis'fe?fected 'by` the resonant characteristics
of the‘aperture, andJ the‘magnitude- of ' this volt
age difference increases as the'A magnitude of- the
exciting" Waves’- increafses». Upon reaching apre’
dëterminedf value; the dielectric materialr within
tha aperture breaks down; that is; the voltage»
difference ~ is sufficient to cause ionization of the
medium-»whiclr-may'be‘ïair, and an electric- dis--~
charger taliespla‘ce- across the aperture. Upon
i occurrence-` of‘such` an electric discharge; the>
waveft?ansmitting characteristics of the‘- guide
are‘radically change’d`^,_ causing rapid attenuation
or theA electromagnetic WavesK within the» vicnity:
of the Wall- 3ì WithoutV attempting to- enter'into
aperture- to minimize»- anyf discontinuity'
im-~ ~‘ f any detailed -discussion of the reason Why the
waves' are not transmitted beyond the-wall 3`, sufpedanceof-fthe dielectric 'guide may1 befmore fully
fîce it tcfsay‘» that' then presence of the charged
appreciated byy reviewing certain fundamental
particles' Within the vicinity of the-resonant ap
concepts' relative' to‘ thepropagationof an Hoi
erture; due to' the electric discharga‘effèctively
type» wave ina-"dielectric guide;` The total iin
pedanc‘eeZo-of- a rectangular waveguides, which f changes the' dielectric constant= of' the mediumv
through which the' waves are being propagated,
may.; ofcourse, be characterized as“ thef ratio of
The mannerr in which-.the dielectricy window 8
cooperates with» the wall `3 andn` the associated
the applied" voltage? V“ to- the»l current I`, may also
bed'eñned a'sffollows‘.
e
'
'
~
Y
(1):'A
where nobis» the dielectric Con-stant- ofr air, xg is
as; forexample; air` in the> present discussion,
thereby substantially» increasing the critical' min
imum frequency forl the particular' guide“ em-~/
ployedl` so= that the Waves are` not propagated an
appreciable distance beyondy the wall‘3.
‘
'
`
" -Figï `2r represents a morel‘detailed cross sec'
y and c isi the velocity of light”. If'the total' guide _
tional view of that portion of the wave guide
including the wall I‘I` of the' dielectric Window 8'.
particular Wave~l`ength the‘following‘ relationship`
may be constructed’` cf‘an alloy; such as' an iron
the wave-length off‘ the Waves within the guide,v
impedance- isî‘constant' alongn the- guide, {theçvirave` " T_he‘dielectric- window* 8a may be- constructed of'
a'suitabl'e vitreous material, such as a boron
will be' propagated with no reflection. To main:
silie'ate glass, and sealed' to'` the"4 metalA wall 3’ by'
tain this impedance constant for changes' in
m‘e'arisfof acylindrical ilange 9'. The ñange 9
guide dimensions c“ and-hone must have at any
fora rectangular' guide:
l
`
`
niclëel-cobalt alloy; to' facilitateV sealing of' the
glassto‘ the'meta‘l Wallï
A , = constantä lc
where Agathe. phase-Wave-length of `the Waves
transmittedthrough the- AguideÍ is.:
'
'a Tè'
e) l
(.395.
~
‘
` In Fig; 3`, an end View of" the bulbous ‘dielec
tric window‘ andA thev resonant slotj is` also` illus
tratedi
"Figa 4‘ and. 5 represent two views of a different.
form or’ the dielectric Window for sealingI a sec
tion-'cfa dielectric> Wave“ guide.. The> metallic wall>
including= the resonant aperture or's'lot may be
_formed integral with'Y theA walls ofthe dielectric
Wave` guideas shown' in Fig. 4'. where the Walls
50
andwhere 7V is the wave length of ‘the exciting
constituted righteangle‘ extensions of' the top. Í`0
waves in free space and'where the electric com
ponent-‘of the ñeld‘ is perpendicular to the di’
mension b'o'?the guidetf ~
l
andthe bottom H‘ of; a sectionof a rectangular
wave' guide. InÍ` this modiñ‘cati'on of my inven
tion; the resonant aperturemay' be in the nature
Where the transverse wall includesan aper 55 ofia'tunedorjresonant rectangular slot 12“ which
ture which is resonant to the -frequency of1 the
isf-falsorvA t‘un‘ed‘ to the frequency of the exciting
exciting electromagnetic» Waves andl where ` theV
means which ,establishes the electromagnetic
change in the` guide dimensions occasioned by
Waves inthe,v guide and in which the height h and'v
such a structure is" aismall fraction «of the waveA y thefl'ength, Ii'ythereof bear a definite relationship
length of the: Waves:VV transmitted througlr‘the 60 withB respect to' the excitation frequency and the.
guidathe change in thez-total‘impedance offered.,
trai'tls‘yents~eJ dimensionsof" the guide, particularly
bythe guide isf also-relatively small,V ,
the‘basejdimension b. vIt is to' be understood that
Therefore, lprovide a Window 8 which. offers
var_ibusrdimensions ofi the resonant slot may be
an; impedance « effect substantially equalY and op'
posite tof‘ that produced by the resonant aper
ture,. so `that‘wa Wavev propagated. through. the
guide experiences substantially no reflection.I
The resonant'aperture 5--1 is the electrical equiv
employed;_ìthat ‘is`,`,the dimensions ofthe slot may
be Varied"
still’. maintainits resonance with
respectitof the exciting frequency.
I'proyide' a sealing. structure for a dielectric
Waite* ‘guide which notonly affords mechanical
alent of a parallel resonant circuit and the win
strerigfthf'wl'ierelitlisfdesired? to seal a. sectionofì
dow 8 appears as a reactance in shuntwiththis>
ance is capacitivelor> inductive in the.V plane of
a dielectrici‘wave' guide, but> is also designed and.
arranged so that' the assembly including the slot.,
the` metallic wall, and'ïïthe, dielectric window„ is'.
wall 3 is determined bythe'spacingof. window 8'(
substantiallyr reflectionl'ess. Furthermoratlie >di;
parallel. resonant circuit. Whethery thereact
el'ectric window construction which I provideïp’er
i
oi" aperture âl-T may he correlatedso that‘theA` 75 ata partial vacuum or at“ l‘ow pressure;
from. wall' 3i
lspacing ‘and ' the dimensions'
a
2,407,069
, More particularly, as a means for sealing a.
sectionpof a wave guide, I provide a dielectric
window I3, preferably constructed ofa vitreous
material such as glass and which may be par
tain degree of resilience iSPVI'OVided to compensate
for strainsincident to pressure and temperature
variations. »In this manner, variations in pres
sure do not change the position of the glass win
tiallyßsupported in position by means of adjoin
dow, and consequently do not appreciably affect
ing metallic straps I4 and I5 which establish a
suitable conductive path between the top ||l and
the net reflection from the Window.
Further
more, the glass window 26 is constructed of a
bottom II of one section of a Wave guide and a
top I6 and bottom |‘I of another section of a
suitable glass, such as boron-silicate, having a
or Ãvice versa, depending upon the direction of
such that an appropriate amount of material is
temperature coefficient of expansion substan
dielectric Wave guide. It is to be understood 10 tially equal to that of the metal constituting the
that similar straps Maand I5_a. shown in Fig, 5
ring 23. Wall 2| is provided with an annular
are also placed along the sides of the guide to
groove~21 in which the section 24a of ring 23 is
afford similar bridging means. In this manner,
seated. Ring 23 may be welded or soldered to
a continuous conductive path is provided between
wall 2|.
_
the two sections of the guide. If it is not desired 15 Inthe production of this type of window, the
to form the wall or diaphragm I8,l which includes '
ring 23 may be sealed to the wall 2|, and the glass
the resonant slot I2, integral with the top and
Window v26 may be sealed tolsection 24h of the
bottom members Il] and ||, the diaphragm may
ring by placing the Window 26,11pon the section
be soldered or Welded to these members. _
24h and subjecting the ring 23 to a heating
The window I3 is designed and positioned rela 20 agency such as a high frequency field, causing the
tive to the wall I8 so that the reiiection from the
glass to seal around the outer edge of section 24D,
slot I2 cancels the reñection from the dielectric,
the diameter and thickness of the glass being
wave propagation through the guide. The win
provided for making a seal of desired strength.
dow It'> ¿may be cemented -to the diaphragm by 25 As an agency for controlling the effective di
usingV a vacuum cement I9 so that one of the
mensions of the resonant slot or aperture, I pro
sections or regions of the Wave guide may be
maintained at a different pressure from an ad
vide externally accessible means for varying the
natural resonance frequency of the slot, and
joining region.
y
`
which may comprise a screw 28 which extends
I have found that the length -L of the slot I2 30 into the body ofV the `wall'2I and into the aper
required Vto make the window I3 reflectionless
ture, and as illustrated may extend into one of
depends very critically upon the proximity or
the circular openings Aat the ends of the elongated
spacing of the dielectric material used in the
slit 22 thereof. It will be appreciated that as the
window. To establish this distance and to allow
position of the screw is changed, the effective di
space for the cement I9, a thin metal gasket or
mensions of the aperture are also changed, there
35
spacer 20 is inserted around the `slot |2«. This
by adjusting or controlling the frequency at
gasket may be formed as an integral part of the
which the aperture is resonant.
wall or diaphragm I8 and positioned as close
v If desired, the screw 28 may be provided with
to the slot as desired. Residual reflection from
an extension 28' of 'substantially paddle shape
the Window I3 after construction may be canceled 40 which may extend into one of the circular open
or neutralized by cementing to the outside sur
ings of the resonant slot, and the position of
face of the dielectric window lI3 a diaphragm
which determines or controls the natural reso
I3’ of properly chosen characteristics.
nance frequency of the slot.
,
I have’found that a Window constructed in ac
Where it is desired to maintain the resonant
cordance with the principles of my invention 45 aperture in a suitable atmosphere and at the
described herein, particularly that type of win
proper pressure, thus maintaining a high degree
dow construction represented in Figs. 4 and 5,
of sensitivity of the aperture to the intensity of
causes very little reflection of the electromagnetic
the electromagnetic waves being transmitted
waves, For example, a window constructed in
accordance with my invention reñects substan Ul through the guide, the> aperture may be com
pletely enclosed in such an atmosphere. For ex
tially only 0.3% of the energy incident upon it.
ample, two arrangements such as shown in Fig. 6
Figs. 6 and 7 diagrammatically illustrate a still
may be employed, one on each side of the wall 2|,
further modiñcation'of the window construction
for a dielectric wave guide wherein a metallic
in a manner illustrated in Fig. 8 wherein a wall
Wall member 2I` positioned in a dielectric wave
29, provided with a resonant aperture 30, is sealed
guide and lpreferably constructed of a metal, such.
by bulbous vitreous windows 3| and 32, which are
as_brass or copper, is provided with a resonant
sealed tothe -wall 29 by rings 33 and 34 of a con
aperture 22 of the type having an elongated slit
structionV and material similar to ring 23 dis
with circular openings at either end. In order
cussed in connection With Fig. 6.
to establish a'seal of suitable mechanical rigid 60 The atmosphere employed within the enclosure
ity and one which is substantially reflectionless,
by maintaining the dielectric element of the Win
dow precisely positioned relative to the wall and
the slot, I provide an arrangement 4wherein the
dielectric window is sealed to the wall by means
of a supporting frame or ring 23, preferably con
structed of a metal such as an iron-nickel-cobalt
alloy, thereby facilitating the sealing of a vitre
ousÍo-ruglass dielectric window 24 which is of
bulbous of hemispherical configuration. The me
tallic ring 23 is preferably constructed of a thin
sheet and may be formed by a suitable stamping
operation so that i-t is provided with two sections
2'4ja _and 24b.of unequal diameter joined by a
substantially transverse section 25» so that a cer
may be any suitable fluid or gas which will sup
port an electric discharge when the voltage dif
ference between the edges of the slot or aperture
attains a predetermined value, and which permits
a substantially rapid extinction of the arc when
the voltage difference decreases below the critical
value. For example, I'may employ within the en
closure an atmosphere of hydrogen and Water
vapor, an atmosphere of nitrogen, or an atmos
> phere of argon. '
‘
It will be understood that in the application
of the embodiment of my invention _shown in Fig.
8, to a _dielectric wave guide; wall member 29 is
75 placedin conductivevcontact with the metallic or
'
arcanos
9
conductive Walls vof the guide. For example, it
may replace the ’wall >3 and :associated assembly`
shown lin Fig. 1.
10`
.
quency` oi an aperture or slot 56 vis positioned in
the-slot so as not to be subjected to the electric
discharge which is produced when the magnitude
As stated above, the dimensions of a resonant
of the electromagnetic waves transmitted
slot :in a system of this nature are :fairly critical;
through a wave guide attains or exceeds a pre
that is, variations in the dimensions change the
determined value. The resonant aperture or slot
frequency >at >which the aperture or slot is lreso
5E! comprises an elongated portion or slit 5| ter
nant. In some applications and in the operation
minated at each end in enlarged openings 52 and
of dielectric wave guides, it may be desirable to
ESQ One of the openings, such as opening 53,
tune or adjust the frequency‘at which the aper
may be provided with an extension 54 in which
ture ls resonant while maintaining the aperture
is placed an adjustable or deformable diaphragm.
ina region of low -pressure or in a region of a de
55 which is sealed to the body of the wallso that
sired atmosphere. Consequently, I provide ex
the region including the aperture may be main
ternally accessible means for controlling the .ef
tainedLa-t ‘low pressurelor within a desired atmos
fective dimensions of a tuneable aperture‘mount
phere. A `metallic member >or block 5d `'of high
ed in a metallic wall suitable `for use in conneci
thermal conductivity is >attached to diaphragm
tion with a dielectric wave guide. One form of
E5 and may'beactuated or positioned bya diiîer
my :invention is illustrated in Fig. `9 wherein a
ential screw arrangement 51 similar to that
metallic wall 3S is employed and may be con
shown in Fig. 9. I'n like manner, the adjusting>
structed in upper and lower sections ‘31 and `38 20 means is made externally accessible by extending>
to :facilitate the construction of the aperture and
to a recess 58 in the body of the metallic wall.
to'permit the Vplacement therein ofthe adjusting
"The Wave guide structures shown in Figs; '7-10
means itc be .described presently.
v
are more speciiically described and claimed in my
The .aperture 3f9smay1be .of the form illustrated
copending application, Serial No. 553,512, iiled
in Fig. ‘1'7 comprising a' restricted elongated sec 25 December `16, 1944.
‘
tion „and having circular :openings at each end
`While I have lshown and described my inven
thereof. Furthermore, r.the aperture 39 may 'be
tion vas appliedlto a particular system embodying
maintained ata low "pressure, .or maybe main
various devices diagrammatica'lly shown, it will be
tained in a .suitable »atmosphere at the proper
obvious to those skilled in »the art that changes
pressure :by means of `a pair ¿of bulbous vitreous 30 and modiñcations may be made withoutdepart
Windows -40 and 4| which are sealed to and ‘sup
ing from my invention, and I, therefore, aim in
ported ‘by ¿the `wal-1 :36 _by ymeans .of dmetallic rings`
the appended claims to cover all such changes
42 and 43 constructed `-in the ‘manner explained
and modiñcations as ‘fall ‘Within the true spirit
above in connection with the apparatus shown 'in
and scope of my invention.
.
Fig. 6.. nThe rings 412 and 43 may beseated 1in -an
What I claim as new and `desire to secure "by
nularfs'rooves in the `end'faces of wall 3.6.
As a means for `tuning the -resonant aperture
39, -I provide an adjustable member, such »as a
Letters Patent of the United States is:
1. In combination, a dielectric wave guide of
the hollow-pipe type-exciting means for estab
lishing electromagnetic waves within said guide,r
deformable diaphragm 44, lwhich may constitute
one boundary of the resonant aperture and `may 40 a metallic Wall associated with said guide and
be Áwelded `or soldered to the upper section :31 .of
lying 'in' a plane substantially transverse to the
Wall 3E.
l
direction of wave propagation through said guide
The upper section 31 of wall 36 is provided’with
and -‘provided with an aperture having an appre
a recess 45, which may be `of> rectangular cross
ciable ¿dimension perpendicular to the electric
section, and is also Aprovided'with a communicat
component of the ñeld incident to the propaga
ing circular opening .'46 lwhich extends to an outer'
tionvof waves through said guide and tuned to
periphery of the upper section 31. 4This arrange-`
the frequency of said exciting means, and a sub->
ment permits external ladjustment ofthe position
of the Adiaphragm so that it is not ‘necessary to
disturb the seal for the `resonant aperture `in ~
making an adjustment. ‘I provide a 'metallic
block §41 v‘which `is connected to `the 'diaphragm
44 and which is positioned by 'means of adiiîer
ential screw arrangement 48 whichextends -f-rom
the block 41 to the Arecess 4,9. >The block «4,«1is
preferably vconstructed of „a «material having :a
relatively :high »thermal conductivity and ther-malV
capacity to facilitate the dissipation lof the heat
stantially
>reiiectionless _structure
connected
across said aperture comprising a dielectric ma
terial sealed to said wall and having an imped
ance eiïect substantially equal and opposite to
that produced by said aperture.
` 2. In combination, a dielectric Wave _guide of
the hollow-pipe type, exciting means for estab
_ lishing electromagnetic waves within said guide.
a `metallic wall associated with said guide and
lying in Va plane substantially transverse to the
direction of wave propagation through said guide
incident .to the estabishment of electric Idis
and provided with an aperture having an appre
charges `across the boundary lof the _resonant
ciable dimension perpendicular to the electric
aperture when the .intensity of `the .electromag
component of the ñeld incident to the propaga
netic waves exceeds'the .critical value. ,For ,ex-Í
tion of Waves through said guide and tuned to
ample, the block 41 may ‘be-_constructed of copper.
the frequency of `said exciting means, and means
Upon _adjustment 0f .the differential. screw ar
connected across said aperture .comprising a
rangement 48., -the block 41 is raised or. lowered, 6. vitreous dielectric member sealed to said wall and
thereby deforming the diaphragm 44 and effec.
. having
an eiîective impedance substantially
tively controlling the dimensions of the resonant
equal and opposite to that of said aperture so
aperture. «Of course, the diaphragm 44 is sealed
that .the assembly including said dielectric mem
to the upper section 3‘1 of wall ‘3B so ‘that `the 'ad
ber'and said Wall is substantially refiectionless.
justment may ~-be made without disturbing :the 70.4 3. `In combination, a hollow-pipe type con
condition of ¿the .atmosphere within which the
ductive member, exciting means for establishing
'resonant :aperture ‘is enclosed.
’
`
.An _alternativeembodiment of my linvention' is
illustrated in
1'0 wherein the adjustable'
means for controlling the :natural resonance 'fre
electromagnetic `waves within said member, a Wall
positioned in said member lying in a plane sub
stantially transverse to the direction of wave
propagation through said member and provided
2,407,069
12
11
ber and provided with an aperture having an
with an aperture having an appreciable dimen
sion perpendicular to the electric component of
appreciable dimension substantially perpendicu
the Waves and tuned to the frequency of the ex
citing means, and a substantially reflectionless
enclosure for said aperture comprising a bulbous
lar to the electric component of the field incident
to said Waves and tuned to the frequency of said
exciting means, and means for sealing said aper
ture comprising a bulbous type member supported
dielectric member sealed to said Wall.
by said Wall and comprising a vitreous dielectric
4. In combination, a dielectric wave guide of
material spaced from the immediate vicinity oi
the hollow-pipe type, excitation means for estab
said aperture so that variations in the position
lishing electromagnetic waves within said guide,
a metallic wall associated with said guide and 10 of said bulbous member incident to pressure
changes, strains and the like do not appreciably
lying in a plane substantially transverse to the
affect the reflection characteristics of the as
direction of wave propagation through said guide
sembly including said wall and said bulbous mem
and provided with an aperture having an appre
ber.
ciable dimension transverse to the electric com
9. In combination, a hollow-pipe type dielectric
ponent of the iield due to said Waves and tuned 15
Wave guide, means for establishing electromag
to the frequency of said exciting means, a bulbous
netic waves within said guide, a metallic wall
vitreous member sealed to one side of said wall
associated with said guide lying in a plane sub
and proportioned to neutralize substantially the
stantially transverse to the direction of Wave
reflection incident to said aperture so that the
assembly including said Wall and said bulbous 20 propagation therethrough and provided With an
aperture having an appreciable dimension per
-member is substantially reñectionless.
pendicular to the electric component of said Waves
5. In combination, a dielectric wave guide of
and tuned to the frequency of the exciting means,
the hollow-pipe type, means for establishing elec
and an enclosure for said aperture comprising a
tromagnetic Waves within said guide, a conduc
bulbous vitreous member and a metallic ring
tive Wall associated With said guide and provided
With an aperture having an appreciable dimen
sealed to said bulbous member and said wall and
having a Itemperature coefñcient of expansion
sion substantially perpendicular to the electric
substantially equal to the temperature coeñicient
component of the ñeld incident to the propaga
tion of Waves through said guide, and means for
of expansion of said bulbous member.
sealing a region of said guide determined in part 30
10. In combination, a hollow-pipe type dielec
tric Wave guide, means for establishing electro
by said wall and comprising a bulbous vitreous
magnetic vvaves within said guide, a metallic Wall
member supported by said Wall and sealed across
said aperture, said bulbous member being propor
associated with said guide lying in a plane sub
stantially transverse to the direction of Wave
tioned relative to said aperture so that the as
propagation therethrough and provided With an
sembly including said Wall and said bulbous
aperture having an appreciable dimension per
member is substantially reñectionless.
pendicular to the electric component of said
6. In combination, a dielectric Wave guide of
the type comprising a conductive hollow-pipe
waves and tuned to the frequency of the exciting
member, means for establishing electromagneticmeans, and an enclosure for said aperture and
waves within said guide, a metallic Wall associ
ated With said guide and lying in a plane substan
tially transverse to the direction of Wave propa
gation therethrough and provided with an aper
ture having an appreciable dimension substan
40 mounted on at least one side of said wall com
prising a vitreous hemispherical member and a
tially transverse to the electric component of the
field incident to the propagation of Waves
through said guide, said Wall being provided with
a cylindrical ñange, and a bulbous dielectric
member sealed to said ñange and being propor
tioned to have an eiîective impedance substan
tially equal and opposite in effect to the im
pedance of said aperture so that the assembly in
cluding said bulbous member and said Wallis sub
stantially reilectionless.
7. In combination, a dielectric Wave guide of
the type comprising a conductive hollow-pipe
member, means for establishing electromagnetic
v
metallic ring sealed to said bulbous member and
said wall.
11. In combination, a dielectric Wave guide of
the hollow-pipe type, exciting means for estab
lishing electromagnetic waves Within said guide,
a metallic Wall associated with said guide and
lying in a plane substantially transverse to the
direction of wave propagation therethrough and
provided with an aperture having an appreciable
dimension perpendicular to the electric compo
nent of the waves and tuned tothe frequency of
the exciting means, said Wall being provided With
a circular groove, and an enclosure for said aper
ture mounted on one side of said Wall and com
prising a bulbous vitreous member and an an
nular ring positioned in said> groove and sealed to
said wall and said bulbous member.
with said guide and lying in a plane substantially
12. In combination, a dielectric Wave guide of
transverse to the direction of Wave propagation 60 the hollow-pipe type, exciting means for estab
therethrough and provided with an aperture hav
lishing electromagnetic Waves Within said guide,
ing an appreciable dimension substantially trans
a metallic wall associated with said guide and
verse to the electric component of the field inci
lying in a plane substantially transverse to the
dent to the propagation of waves through said
direction of Wave propagation through said guide
guide, said Wall being provided with a cylindrical
and provided with an aperture having an appre
ñange. and a bulbous vitreous member sealed to
ciable
dimension perpendicular to the electric
said flange and proportioned to neutralize sub
component of the field incident to the propaga
stantially the discontinuity in impedance inci
tion of Waves through said guide and tuned to the
dent to said Wall.
8. In combination, a dielectric Wave guide com 70 frequency of said exciting means, a dielectric
Window in spaced relation with respect to said
prising a hollow-pipe type member, means for
aperture, a spacer substantially surrounding said‘
establishing electromagnetic Waves Within vsaid
aperture and connecting said Window and said
member, a wall positioned in said member and
wall in spaced relation and for aiîording an
lying in a plane substantially transverse to the
direction of Wave propagation through said mem 75 appreciable space between said window and saidï
waves within said guide, a metallic wall associated
2,407,069
13
14
wall whereby said Window may be sealed to said
wall.
13. In combination, a dielectric waveguide of
the hollow-pipe type, exciting means for estab
lishing electromagnetic Waves within said guide, 5
a metallic Wall associated with said guide and
lying in a plane substantiallytransverse to the
direction of Wave propagation through said guide
and provided with an aperture having an appre
ciable dimension perpendicular to the electric
component of the field incident to the propaga
tion of Waves through said guide and tuned to
the frequency of said exciting means, a vitreous
dielectric Window in spaced relation with said
wall, a spacer substantially surrounding said
aperture for maintaining said Window and-Wall
sections, exciting means for establishing electro
magnetic Waves within said guide, a metallic
Wall conductively connected to one of said sec
tions and lying in a plane substantially trans
verse to the `direction of wave propagation
through said guide and provided with an aperture
having an appreciable dimension perpendicular
to the electric componentv of the field incident to
the propagation of waves through said guide and
tuned to the frequency of said exciting means, a
dielectric Window in spaced relation with said
wall, a spacer substantially surrounding said
aperture and in contact with said Window and
said wall for maintaining said window and said
15 Wall in spaced relation and for providing a space
for a vacuum cement for sealing one of said sec
in spaced relation and for providing a space for
tions With respect to the other, and means for
a vacuum cement to seal said window to said
conductively connecting said sections and bridg
Wall.
ing said window.
14. In combination, a dielectric Wave guide of 20
MILAN D. FISKE.
the hollow-pipe type comprising two metallic
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