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Dec; 10, 1946.
2,412,446
_- . K, c. DE wA|_T
ULTRA HIGH FREQUENCY SYSTEM
Filed Oct. 31, 1942
~Fig.3.
Inventor:
‘
Kenneth iii/Walt, '
by WW6
2 W1
H is Attorney
Patented Dec. 10, 71946:
~- +
,
2,412,446
PATENT‘ OFFICE
urinal) sr
2,412,446
ULTRA HIGH FREQUENCY SYSTEM
Kenneth C. De Walt, Schenectady, N. Y., assign
or to General Electric Company, a corporation
of New York
Application October 31, 1942, Serial No. 464,036
10 Claims.
1
(Cl. 178-44)
2
My invention relates to ultra high frequency
which I provide includes a metallic member, such
systems, and more particularly to dielectric wave
as a cylinder, which extends through a circular
guides of the hollow-pipe type and associated ap
opening in the transverse wall and also surrounds
paratus for propagating or attenuating the elec
the tuned aperture or slot. The metallic cylinder
tromagnetic Waves within the guides.
5 extends an appreciable distance on each side of‘
It is now rather generally understood that elec
the wall to facilitate the sealing of dielectric win
tromagnetic waves may be propagated through the
dows, such as vitreous or glass Windows, to the
interior of a metallic member or pipe of conduc
tive material which contains a. dielectric medium,
cylinder, thereby establishing a hermetically
Waves is greater than a critical or minimum fre
quency, the value of which is established prin
intensity of the electromagnetic waves within the
guide.
sealed region about the aperture giving it thereby
if the frequency of the exciting electromagnetic ll) a high degree of sensitivity to the magnitude or
cipally by the transverse dimensions of the guide
For a better understanding of my invention,
structure.
In accordance with the teachings-of my inven
tion described hereinafter, I provide new and im
proved structure of a device used in conjunction
reference may be had to the following description
taken in connection with the accompanying draw
ing, and its scope will :be pointed out in the ape
pended’ claims. Fig, 1 diagrammatically illus
with a dielectric wave guide and which may be
trates‘ an embodiment of my invention as applied
employed as a means for selectively obtaining pro~
to a dielectric wave guide of the hollow-pipe type
pagation or attenuation of the waves within the 20 having a rectangular cross section, and Figs. 2
guide. More particularly, in accordance with the
and 3 are a cross-sectional view taken along the
teachings of my invention I provide a new and im
lines 2-2 of Fig. 1 and an end view, respectively,
proved enclosing structure for a resonant aper
of the enclosing structure for the resonant aper
ture or slot to be positioned in or associated with
ture.
a dielectric wave guide, and which is readily
Prior to the detailed discussion of my present
adaptable for rapid manufacture and assembly.
invention as applied to wave guides wherein elec
It is an object of my invention to provide a new
tromagnetic energy is transmitted dielectrically,
and improved ultra high frequency dielectric wave
guide system.
It is another object of my invention to provide '
a new and improved sealed enclosure for a reso
nant aperture or slot to be positioned in, or asso
ciated with, a dielectric wave guide of the hollow
pipe type.
It is a further object of my invention to pro
vide a new and improved sealing and enclosing
structure for a resonant aperture or slot to be
positioned within a dielectric wave guide of the
hollow-pipe type, and which is inexpensive to
it is believed that it may be helpful to review gen
erally certain aspects of the phenomena asso
ciated with the propagation of electromagnetic
waves through guides. As is well appreciated,
wave guides of this nature may be employed for
the transmission and propagation of electromag
netic waves of a variety of forms or character.
These waves have been generally indicated here
tofore as being of the E and H types. subscripts,
as indicated, EM” and Hn,m, have been assigned
to these waves in order to indicate the nature of
the waves, where n represents the order of the
manufacture and readily adaptable to» rapid as 40 wave and m represents the modeofpropagation.
sembly by virtue of the relatively small number
The order. of the wave is determined by the man
of parts involved.
her in which the ?eld intensity varies circumfer
Brie?y stated, in the illustrated embodiment
entially around the axis of the guide, whereas the
of my invention I provide in an ultra high fre
mode
is determined by the manner of its variation
quency electromagnetic, wave guide of the hollow
withradial distance from the axis of the guide.
pipe type, a tuned or resonant aperture structure
The E type waves have both a longitudinal and a
which is positioned in or associated with the guide
transverse component of electric ?eld but only a
and which comprises a metallic wall lying in a
transverse component of magnetic ?eld. The H
plane substantially transverse to the direction of
wave propagation through the guide, and which 50 type waves have both a longitudinal and a trans
verse component of magnetic ?eld but only a
includes therein an aperture or slot tuned sub
transverse component of electric ?eld. Although
stantially to an electromagnetic wave of prede
my invention is applicable to systems, for the
termined frequency equal to or greater than the
critical minimum or cut-o? frequency of the
transmission of a great variety of waves of both
guide. More particularly, the improved structure 55 the E and H types, in describing my invention
2,412,446
3
tenuated so that energy cannot be transmitted
through the guide. Above the critical frequency,
. ture I2 is arranged to have its principal or lon
the wave is propagated in the desired direction and
the wave
4
is tuned to a frequency equal to or greater than
the critical minimum or cut-off frequency of
the guide established. Although I may employ
resonant apertures of various con?gurations, for
the purpose of illustrating my invention I have
chosen to represent the resonant aperture l2 as
comprising a central elongated portion or slit
l3 terminated at the ends thereof in enlarged
openings, such as circles Ill and I5. The aper
hereinafter reference will be made particularly to
the H01 type of wave.
It is also appreciated that, in pipes for dielec
trically guiding Waves, each con?guration of the
pipes establishes a critical minimum frequency
below which energy is not propagated through the
guide. Stated in other words, for frequencies be
low this critical frequency, the wave is rapidly at
assumes a time-space distribution
gitudinal dimension substantially transverse to
the electric component of the electromagnetic
through the guide established principally by the
?eld due to the waves within the guide in order
wave length of the exciting impulses for the guide
and the transverse dimensions of the guide,
to e?ect a concentration or acoentuation of the
Referring now to Fig. 1, I have there illus
trated my invention as applied to a high fre
quency dielectric wave guide system for con-.
trolling the propagation or attenuation of elec
tromagnetic waves of predetermined frequency.
Although my invention may be applied to di
electric wave guides of the hollow-pipe type hav
ing various cross-sectional con?gurations, for the
purpose of facilitating the description of my in
potential difference due to the waves. By virtue
of such a con?guration, or the equivalent thereof,
the aperture or slot in its entirety is resonant to
a predetermined frequency determined by the
dimensions, principally its height and length.
The slot, of course, has a distributed inductance
and a distributed capacitance which resonate
to the particular frequency for which it is de
signed. Consequently, the entire potential dif
ference of the electromagnetic waves within the
vention I have chosen to consider a system which 25 guide appears across the top and the bottom of
the slot.
is used primarily for the transmission or atten
I provide a new and improved enclosing struc
uation of an H01 type wave within a wave guide
ture for the resonant aperture 1 2 and which may
having a rectangular cross section,
be more clearly appreciated by referring to the
It is desirable that the metallic enclosure for
the guide be of a metal of large electrical con 30 cross-sectional view shown in Fig. 2. A metallic
member or cylinder I6 is provided which extends
ductivity, such as copper or brass. The wave
through a circular opening 11 in the transverse
guide may comprise a metallic base plate I and
wall H. It will be noted that the cylinder l6
a top plate 2 of transverse dimensions 1), and in
surrounds the aperture l2 and extends an ap
cludes metallic side walls 3 and 4 having a height
a. The improved enclosure for the resonant 35 preciable distance on each side of the transverse
wall I I. I also provide dielectric windows l8 and
aperture slot to be described presently may be
19 which are sealed to the metallic cylinder l6
employed in a variety of ultra high frequency
and may be preferably sealed to the inner sur
systems, andit is not necessary in the utilization
face of the cylinder. The dielectric windows l8
of my invention to employ the particular wave
guide construction illustrated. One way in which 40 and i9 may be of the bulbous or substantially
semi-spherical con?guration, as illustrated, and
the structure may be employed is by using a
may be constructed of a vitreous material such
wave guide in which one end thereof is termi
as glass and are sealed to the cylinder l6 by any
nated in a metallic plate 5 which may be welded
of the now well known glass-to-metal seals such
or soldered to the base and top plates 1 and 2
as a sealing structure comprising, as an alloy,
and the side walls 3 and 4. The other end of
a composition of iron, nickel and cobalt, which
the dielectric wave guide section as illustrated
may comprise the cylinder l6.
may be terminated in a ?ared horn structure
By virtue of the con?guration of the bulbous
6 which may be employed either in the trans
windows 18 and [3, the re?ection of the windows
mission or reception of electromagnetic waves.
Alternatively, this end of the wave guide section 50 or enclosure may be made substantially equal
and opposite to any re?ection incident to the
may be terminated in a transverse metallic Wall
presence of the transverse wall I I and associated
and electrode means may be employed in place of
resonant aperture, so that the total assembly
the horn structure 6.
is substantially re?ectionless.
As a means for exciting or extracting high
As stated above, the dielectric wave guide, by
frequency electromagnetic energy from the wave 55
virtue of its con?guration, is critically responsive
guide, I may employ a concentric or coaxial
to the frequency of electromagnetic waves at
transmission line 1 comprising an outer tubular
which it is excited, there being a minimum or
and metallic conductor 8 which is conductively
cut-01f frequency below which the electromag
connected to the base plate I substantially sur
rounding a circular opening 9 in plate I. The 60 netic waves are rapidly attenuated so that the
waves are not transmitted an appreciable dis
other element of the concentric transmission line
tance through the guide. The wave lengthof
may comprise an inner conductor In which may
the wave transmitted through a rectangular
be conductively connected to the top plate 3.
guide is a function of the wave length of the
Of course, it will be appreciated that I may em
ploy other exciting or energy extracting means, 65 exciting wave in free space and the dimensions
of the guide. For example, in a rectangular air
such as probes of various con?gurations or the
?lled wave guide of base b and height a, the wave
equivalent thereof.
length )\g for an H01 type wave may be expressed
I employ a metallic wall ll lying in a plane
substantially transverse to the direction of wave
propagation through the guide and which also 70
may be. constructed of a highly conductive metal,
(1)
such‘ as copper or brass, and which is conduc
tively connected to the members [-4, inclusive,
where A is the wave length of the exciting wave
of the guide. The wall [I is provided with a
in free space and where the electric component
resonant‘ aperture or slot l2 (see Fig. 3) which 76 of the ?eld is perpendicular to b.
5
2,412,446
The total impedance Z0 of a rectangular guide
using air as the dielectric may be de?ned as
follows:
6
charge, or are discharge, as soon as the voltage
decreases su?iciently.
,
Some of the advantages incident to my inven
tion are the simplicity of the structure which
Zr‘ 2 T b
(2)
where no is the permeability of air and where c
is the velocity of light. Of course, the total im
is readily adaptable to evacuation and assembly.
Furthermore, by virtue of the metallic cylinder
it‘, there is provided a simple construction to
which may be sealed the dielectric or vitreous
pedance may be characterized as the ratio of
windows I8 and [9.
the applied voltage V to current I which is trans 10
As to the method of assembly, it may be stated
mitted through the guide. If this total guide
that the structure may be assembled in any one
impedance is constant along the guide, the wave
of several ways, one of which may comprise an
will be propagated with no re?ection. To main
initial sealing operation of one of the windows,
tain this impedance constant for changes in
such as window Hi, to the cylinder 16 which is
guide dimensions a and b, one must have at any 15 then passed through opening il in the wall struc
particular wave length the following relationship:
%)\,,= constant 5 It
(3)
In the embodiment of my invention illustrated,
the change in guide dimensions or effective di
mensions occasioned by the presence of the
transverse wall H is made a small fraction of a
wave length and any re?ection due to the dis
continuity so produced is inappreciable. Fur
thermore, it can be shown, analytically and ex
perimentally, that the reflection may be can
celled by a similar discontinuity, opposite in
sense, a very short distance along the guide from
the ?rst discontinuity. Considering the resonant
aperture or slot and the effect thereof, the total
impedance of the slot is the same as that of the
guide since the re?ection produced at the en—
trance of the slot is cancelled by the re?ection
ture ll. Thereafter, the window 19 may be sealed
in place in a chamber of desired pressure, or an
atmosphere or medium of desired pressure. Alter
natively, the window it may be provided with
a tubulation (not shown) and after scaling to
the cylinder 86 and after exhaustion and ?lling
with the desired medium, the tubulation may be
sealed. This tubulation may be such that after
the sealing-off operation no substantial discon
tinuity or bulge is present on the surface of the
window l9.
The operation of the embodiment of my in
vention shown in Fig. 1 will be explained by con
sidering the system when it is operated as a
means for selectively controlling the propagation
or attenuation of received ultra high frequency
signals. In such an instance, the ?ared horn 6
of the wave guide may be employed as a means
from the exit. Furthermore, the assembly, in
for receiving the signal. So long as the intensity
No detailed analysis is presented here as to the
manner in which the eifective length and height
of the resonant aperture or slot i2 may be com
extracting a signal from the guide which is re
sponsive to the electromagnetic waves therein.
cluding the wall H, the resonant aperture or slot 35 of the received signal remains below a predeter
mined value, the transverse wall I l and the aper
I2 and the enclosing assembly, may be designed
ture l2 and enclosing structure oifer substantially
as a whole so that the resultant discontinuity or
no impedance to the propagation of the electro
the reflection of incident waves occasioned by
the assembly, may be made negligible or substan 40 magnetic waves through the guide, and the elec
trode means 1 may be employed as a means for
tially zero.
puted.
Generally speaking, the relative values
of the effective longitudinal dimension and the
height of the aperture may be modi?ed to estab—
lish the desired resonance of the slot for a wave
of particular frequency. As the height of the
aperture approaches zero, the effective longitu
dinal length thereof approaches the limit
By virtue of the design of the resonant aperture
I2, if the intensity of the electromagnetic waves
increases to a value above the value established
by the design of the aperture and the surround
ing atmosphere, the voltage which appears across
the horizontal edges of the aperture will exceed
the breakdown voltage of the medium constitut
ing the atmosphere to establish a discharge
across the horizontal edges or dimensions thereof,
thereby changing the aperture from a resonant
2
device to a dissonant device.
As a result, the
transverse wall II and the associated aperture 12
where A is the wave length of the electromagnetic 55 constitute a substantial discontinuity within the
wave in free space. For a more detailed analysis
guide relative to the propagation of the electro
of the method of computing the dimensions of
magnetic waves, and the waves will be rapidly
the resonant aperture or slot, reference may be
attenuated so that the waves are not transmitted
had to Patent 2,467,068, granted September 3,
an appreciable distance towards the electrode
1946, to Milan D. Fiske and James M. Lafferty,
means 1. Upon interruption of the received sig
and which is assigned to the assignee of the pres
nal, the consequent removal of the voltage across
ent application.
the aperture will extinguish the electric dis-g
The medium within the enclosure comprising
charge, thereby restoring the aperture to its;
cylinder l6 and the bulbous windows l8 and i9,
resonant condition.
'
and which surrounds the resonant aperture I2,
Another way in which the embodiment of my
may be air at a. relatively low pressure or may
invention illustrated in Fig. 1 may be employed
be a suitable inert gas, suchras neon, xenon, or
is in a signalling or locating system wherein other
argon. Alternatively, the medium within the
apparatus (not shown) ‘ is employed for trans
enclosure may consist of a gas such as nitrogen
mitting a high intensity, ultra high frequency
in water vapor, or any other suitable gas which 70 electromagnetic wave which is re?ected by a
permits the establishment of an electric dis
distant object, and where receiving apparatus
charge, or an arc discharge, when the voltage
(not shown) is connected to the transmission
difference between the horizontal dimensions of
line 1. In such an instance, it will be appreciated '
the slot attains a predetermined value and which
that it is desired to protect the receiving appara
also permits rapid extinction of the electric dis 75 tus during the transmitting operations, inasmuch
2,412,446
7
8
lishing electromagnetic waves therein, a wall
as receiving apparatus is purposely designed in
many instances to operate in response to rela
tively weak signals and consequently should be
protected. In such a system, the resonant slot
within said guide and lying in a plane substan
tially transverse to the direction of wave propa
gation therethrough and having therein an ap
erture tuned substantially to the frequency of
and associated structure serve to prevent the
impression of the high intensity transmitted
signal upon receiving apparatus when the trans
said exciting means, and an enclosure for said
aperture including an elongated member extend
mitter is operating. This is effected by the pro
tective action of the resonant aperture which
breaks down by virtue of the high intensity sig
nals of the transmitter, the waves not being
transmitted beyond the wall Ii in the direction
of line 1. Upon interruption of the transmitted
signal, the electric discharge is immediately ex~
tinguished, thereby restoring the resonant condi
tion of the slot i2 to permit the propagation
through the guide of the relatively weak received
ing through said wall and surrounding said ap
erture, and a pair of vitreous windows sealed to
said member and on opposite sides of said wall.
or re?ected signal.
While I have shown and described my inven
tion as applied to a particular system and as em
said exciting means, and an enclosure for said
aperture having a re?ection characteristic sub
5. In combination, a dielectric wave guide of
the hollow-pipe type, exciting means for estab
lishing electromagnetic waves therein, a. wall
within said guide and lying in a plane substan
tially transverse to the direction of wave propa
gation therethrough and having therein an ap
erture tuned substantially to the frequency of
20
bodying various devices diagrammatically shown,
it will be obvious to those skilled in the art that
changes and modi?cations may be made without
departing from my invention, and I, therefore,
aim in the appended claims to cover all such
changes and modifications as fall within the true
spirit and scope of my invention.
What I claim as new and desire to secure by
Letters Patent of the United States is:
1. In combination, a dielectric wave guide of
the hollow-pipe type having a transverse cross
sectional configuration to permit the propaga
tion of electromagnetic waves above a predeter
mined frequency therethrough, a wall within said
guide and lying in a plane substantially trans- verse to the direction of wave propagation there
through.
having an aperture tuned substan
tially to a frequency equal to or greater than
said predetermined frequency, and an enclosure
for said aperture including a. metallic member
extending through said wall and surrounding said
aperture and a pair of dielectric windows sealed
to said member.
2. In combination, a dielectric wave guide of
the hollow-pipe type having a transverse cross
sectional configuration to permit the propagation
therethrough of electromagnetic waves above a
predetermined frequency, a wall within said
guide and lying in a plane substantially trans
verse to the direction of wave propagation there
through and having an aperture tuned substan
tially to a frequency equal to or greater than
said predetermined frequency, and a reflection
less enclosure for said aperture including a metal
stantially equal and opposite in effect to that of
said aperture and including a metallic member
extending through said wall and surrounding
said aperture and a pair of vitreous windows
sealed to said member.
6. In combination, a dielectric .wave guide of
the hollow-pipe type, exciting means for estab
lishing electromagnetic waves therein, a wall
Within said guide and lying in a plane substan
tially transverse to the direction of wave propa
gation therethrough and having therein an ap
erture tuned substantially to the frequency of
said exciting means, and an enclosure for said
aperture including a metallic cylinder extending
through said wall and surrounding said aperture
and a pair of vitreous windows spaced on oppo
site sides of said wall and sealed to said cylinder.
7. In combination, a dielectric wave guide of
the hollow-pipe type, exciting means for estab
lishing electromagnetic waves therein, a wall
within said guide and lying in a plane substan
tially transverse to the direction of wave propa
gation therethrough and having therein an ap
erture tuned substantially to the frequency of
said exciting means, and an enclosure for said
aperture having a re?ection characteristic sub
stantially equal and opposite to that of said ap
erture and comprising a metallic cylinder ex
tending through said wall and surrounding said
aperture and a pair of bulbous vitreous windows
on opposite sides of said wall and sealed to said
cylinder.
* 8. In combination, a dielectric wave guide of
the hollow-pipe type, exciting means for estab
lishing electromagnetic waves therein, a wall
within said guide and lying in a plane substan
lic cylinder extending through said wall and
tially transverse to the direction of wave propa
surrounding said aperture and a pair of bulbous
gation therethrough and having therein an ap~
dielectric windows sealed to said cylinder.
erture tuned substantially to the frequency of
3. In combination, a dielectric wave guide of
said electromagnetic waves for effecting a con
the hollow-pipe type having a transverse cross
centration of the potential difference due to the
sectional configuration to permit the propaga 80 electromagnetic waves to effect the establish
tion therethrough of electromagnetic waves
ment of an electric discharge thereacross when
above a predetermined frequency, a, wall within
the intensity of the electromagnetic waves at
said guide and lying .in a plane substantially
tains or exceeds a predetermined value, said wall
transverse to the direction of wave propagation
being provided with an opening extending around
therethrough and having an aperture tuned sub
said aperture, and an enclosure for said aperture
stantially to a frequency equal to or greater than
including a metallic member passing through
said predetermined frequency, and an enclosure
said
opening and extending an appreciable dis
for said aperture including a metallic cylinder
tance on each side of said wall and a pair of vit
passing through said wall and extending an ap
preciable distance on each side thereof sur 70 reous windows sealed to said member.
9. In combination, a dielectric wave guide of
rounding said aperture and a pair of bulbous vit
the hollow-pipe type, exciting means for estab
reous windows sealed to said cylinder on opposite
lishing electromagnetic waves therein, a wall
sides of said wall.
within said guide and lying in a plane substan
4. In combination, a dielectric wave guide of
the hollow-pipe type, exciting means for estab 75 tially transverse to the direction of wave propa~
‘2,412,446
10
gation therethrough and having therein an aper
ture tuned substantially to the frequency of said
exciting means and, provided with an appreciable
dimension substantially perpendicular to the elec
tric component of the electromagnetic ?eld for
effecting a concentration of the potential dif
ference due to the waves within said guide, said
wall being provided with a circular opening of
a diameter greater than the principal dimen
sion of said aperture, and an enclosure for said 10
tially transverse to the direction of wave propa
gation therethrough and having therein an ap
erture tuned substantially to the frequency of
said exciting means and provided with an ap
preciable dimension substantially perpendicular
aperture comprising a metallic cylinder passing
through said opening and having an appreciable
to the electric component of the electromagnetic
?eld for e?ecting a concentration of the poten
tia1 di?erence due to the waves within said guide,
said‘wall being provided with a circular opening
of a diameter greater than the principal dimen
sion of said aperture, and an enclosure for main
taining said aperture within a desired atmos
distance on each side of said wall and. a pair of
phere at a predetermined pressure comprising a
bulbous vitreous windows sealed to said cylinder.
metallic member extending through said opening
10. In combination, a dielectric Wave guide of 15 and a pair of bulbous vitreous windows sealed to
the hollow-pipe type, exciting means for estab
said member.
lishing electromagnetic waves therein, a wall
KENNETH C. DE WALT.
within said guide and lying in a plane substan
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