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Патент USA US3070883

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Jan. 1, 1963
H. s. GORDON ETAL
3,070,873
WAVEGUIDE CONSTRUCTION
Filed'Nov. 1, 1956
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INVENTORS.
Hayden .5.‘ Gordon
Roy 6‘. Mar/(er
’
BY
Richard E P057‘
Jan- 1, 1963
HS. GORDON ETAL
3,070,873
WAVEGUIDE CONSTRUCTION
Filed Nov. 1, 1956
4 Sheets-Sheet 2
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I NVENTORS .
5‘. Gordon
Hayden
6.‘ Marker
Ray
BY
R/chard F P057‘
Jan. 1, 1963
H. s. GORDON ETAL I
3,070,873
WAVEGUIDE CONSTRUCTION
Filed Nov. 1, 1956
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1N VENTORS.
Hayden S Gordan
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United States Patent 0
3,070,873
Patented Jan. 1,. 1963
1
2
,070,873
Hayden S. Gordon, Lafayette, Roy C. Marker, Berkeley,
e.g., gold diffusion joints, clamping, and the like, are
unsatisfactory for establishing mechanical rigidity com
mensurate with vacuum tightness of the dimensions speci—
?ed above.
WAVEGUIDE CONSTRUCTION
and Richard F. Post, Walnut Creek, Calif, assignors
to Appiied Radiation Corporation, Walnut Creek,
Calif” a corporation of California
The present invention overcomes the disadvantages and
limitations associated with known methods of construc
Filed Nov. 1, 1956, Ser. No. 61%,899
18 Claims. (Cl. 29-1555)
ing waveguides, and other electrically resonant mechani
The present invention relates to electrically resonant
mechanical structures in general, and more particularly
to an improved method of constructing multiple resonant
cavity waveguides and the like.
Transmission characteristics of ‘guiding systems for the
propagation of electromagnetic waves are very sensitive
ing Waveguides whereby cavity enclosures and septa in
to various physical properties established in the particular
guiding system, particularly the exact dimensions thereof.
It is, therefore, very important that such physical proper
ties in a ?nished waveguide be precisely determined in
mine deviations in electrical resonant frequency from a
cal structures, as well as furnishing other important ad
vantages by providing an improved method of construct
cluding inis apertures are separately formed to relatively
large mechanical tolerances (e.g.,. $0.001”) commen
surate with normal machine shop practices. Said en
closures and septa are then each separately checked elec
trically by appropriate radio frequency means to deter
predetermined desired operating resonant frequency after
which the dimensions of the enclosures and septa are
materially altered by very precisely controlled means to
the construction thereof for otherwise the characteristics 20 accordingly compensate for such frequency deviations.
The enclosures and septa are next oriented and alter
of a system in which the guide is employed would de
nately coaxially aligned in ?nal assembled relationship
pend upon unpredictable factors which would accord
and then rigidly joined by an improved diffusion joining
ingly render the system inoperable or unreliable. For
process possessing certain advantages over known as
example, one type of waveguide for use in electron linear
accelerators and other devices requiring waveguides for 25 sembly methods.
It is, therefore, an object of the present invention to
the uniform transmission of radio frequency power com
provide an improved method of constructing electrically
pnises a series of coaxially disposed cylindrical cavities
resonant mechanical structures with great precision.
coupled one to the other by transverse circular septa
It is another object of the invention to provide an im~
having axially aligned apertures or irises provided therein.
proved method of permanently tuning resonant cavities
To insure reliable operation of the ?nished guiding sys
tem the waveguide must be constructed so as to embody
with great precision.
It is still another object of the present invention to pro
vide an improved method of constructing mechanical
frequency of each cavity must be the same within very
coupling partitions for the transmission of electromag
close tolerances as determined by the identicalness to
very close tolerances of the electrical equivalent volume 35 netic waves possessing electrical resonance characteris—
tics to very close electrical tolerances.
.
of each cavity and the diameter and edge-contour of
An important object of the invention is to provide
each iris. In addition, each cavity must be spaced at
an ‘improved process for joining metallic surfaces with a
an exact fraction of the wavelength corresponding to the
certain requisite properties, e.g., the resonant electrical
cavity resonant frequency indicating that axial spacing
high degree of rigidity and vacuum tightness.
It is a further object of the invention to provide an
and thickness of the septa must be respectively identical 4-0
improved multiple resonant cavity waveguide having pre
within very close tolerances. It is also desirable that
cise and uniform transmission characteristics for the
the completed waveguide have low electrical losses, be
propagation of radio frequency power, and a method of
free of porosity in the cylindrical walls so as to ‘be ca
constructing same.
,
pable of maintaining a high vacuum in the order of
The structure and method of the present invention to
l><l()—6 mm. of mercury, and be mechanically sturdy
gether with further objects and advantages thereof will
to permit handling and mounting without excessive de
be better understood by reference to the following de
?ection or destruction of vacuum tightness as well as
being capable of being repeatedly heated to tempera
scription taken in conjunction with the accompanying
tures in the order of 600° C. without increasing elec- r
drawing wherein the structure and method of the inven
tion is described and illustrated with respect to speci?c
trical losses, changing the resonant frequency of the
cavities, or causing vacuum leaks to develop.
Conventional methods of constructing waveguides of
the foregoing type, as well as waveguides of various
steps and apparatus in the interest of clarity, however,
no limitations are intended or to be inferred therefrom,
reference being made to the appended claims for a pre
cise delineation of the scope of the invention.
other designs, have depended upon the most exacting
In the accompanying drawing:
1
machining operations to establish certain of the above
FIGURE 1 is a schematic representation of one em
mentioned stringent properties in the ?nished guide. For
bodiment of a ?nished multiple cavity waveguide;
example, in waveguides of the type described above the
FIGURE 2 is a cross sectional view of this embodi~
dimensions of the cavity rings and septa including iris
‘
apertures are generally carefully machined to mechani 60 ment taken at 2—2 of FIGURE 1;
FIGURE 3 is a schematic representation‘of'a cavity
cal tolerances of at least 10.0001" to establish the de
ring of this embodiment formed by conventional manu
sired resonant frequency of each cavity and the axial
factuning and machining methods;
spacing of the cavities corresponding to an exact frac
FIGURE 4 is a schematic representation of a test ?x
tion of a wavelength. Such ?nishing machining opera
tions are disadvantageous in that they are dif?cult, time 65 ture for determining the resonant frequency of the vol~'
ume enclosed by the ring of [FIGURE 3;
'
consuming, and although they establish the above two
FIGURE 5 is a schematic representation of a second
properties in the waveguide according to mathematical
test ?xture for determining the resonant frequency of the
analysis based upon physical dimensions to very close
volume enclosed by the ring of FIGURE v3 embodied in
mechanical tolerances, the wave guide does not neces
an electrical circuit for measuring same; ‘
sarily conform to desired electrical tolerances. Further~ 70 FIGS. 6A and 6B are a graphical illustration of vari
more, known methods of joining the components of mul
ous oscilloscope patterns obtained by the circuit of FIG
tiple cavity waveguides in the ?nal assembly thereof,
URE 5;
’
3,070,873
4
prises a pair of ?at electrically conducting plates l8, 19
FIGURE 7 illustrates one method of decreasing the
volume enclosed by this ring in a controlled manner;
FIGURE 8 illustrates a method of selectively decreas
ing on increasing the volume enclosed by this ring inva
controlled manner;
FIGURE 9 is a schematic representation of a cavity
septum of the embodiment illustrated in FIGURE 1 as
adapted to be disposed in closing relationship at the end
extremities of ring 11 to form an enclosed cavity 21. One
plate 19 is ?tted with conventional excitation and pickup
loop connectors 22, 23 respectively terminating in input
and output coaxial cables, 24, 26 to admit and extract
electrical energy from cavity 21.
One other test ?xture 27 for gaging the resonant fre
quency of cavity rings 11 is shown in FIGURE 5. Fix
ture 27 includes a standard ?xture cavity element 23 which
is formed as a standard cavity ring 29 rigidly joined at
formed by conventional machining, methods;
FIGURE 10 is a schematic representation of a preferred
test ?xture and electrical circuit for measuring the reso
nant frequency of transmission of this septum;
FIGURE 11 illustrates a preferred method of uniformly
removing metal from the edge of the center iris of this
septum or depositing metal thereon in a precisely con
one end extremity to a closure plate 31 having a half iris
. 32 provided therein and at the other end extremity to a
trolled manner to tune same to a predetermined operating
standard septum 33 including a central axial reference iris
aperture 34 thereby forming a standard cavity 35. Said
resonant frequency within very close electrical tolerances;
cavity element 28 is disposed in closing relationship at
septum 33 wtih one end extremity of cavity ring 11, the
other end extremity of which is closed by an end plate 36
provided with a central axial half iris 37 thereby de
and
20 scribing an enclosed cavity 38 coupled through iris 34 to
FIGURE 13 illustrates an assembly ?xture for aligning
standard cavity 35. Plate 36 is ?tted with conventional
and clamping rings and septa in ?nal assembled relation
excitation and pick-up loop connectors 39, 41 respectively
ship, for purposes of joining and sealing such rings and
terminating in input and output coaxial cables 42, 43 to
septa in the ?nal waveguide‘ assembly.
admit and extract electrical energy from coupled cavities
Referring now tothe drawings and FIGURES 1 and 2 25 33, 35. Fixture 27 thus provides means for gaging cavity
in'particular, there is shown a' multiple resonant cavity
rings 11 in the same electrical mode as is established in
waveguide structure comprising a plurality of cavity en
the ?nished waveguide assembly, i.e., in the mode estab
closures conventionally formed as coaxial cylindrical cav
. lished in two adjacent cavities 35, 38 coupled by an iris 34.
ity rings 11 rigidly attached in pressure sealed relation
In order to determine the resonant frequency of each
ship to a plurality of correspondingly interposed coaxial 30 cavity ring 11, test ?xture 17 or test ?xture 27 is con,
nected in a measuring circuit as illustrated in FIGURE 5
transverse circular septa 12, thereby de?ning a plurality
of coaxial spaced resonant cavities 13. Each septum 12
(?xture 27 is shown connected in the circuit of FIGURE
includes a central axial circular iris aperture 14 having
5 at cables 42, 43 although ?xture 17 may be similarly
rounded edges 16 to provide coupling between adjacent
connected at cables 24, 26). As shown in the foregoing
ones of the cavities 13. If will be appreciated that the 35 ?gure, coupled cavities 38, 35 are excited by connecting
most sensitive variable affecting the resonant frequency
input cable 42 to the output of a swept oscillator 44 which
is frequency modulated at 60 cps. by a sweep voltage sup
of each one of such cavities 13 is the volume thereof, which
ply 46. A swept oscillator as herein utilized is conven~
' is in turn a function of the inner diameter and axial length
of the corresponding rings 11 as well as the volume oc
tionally de?ned as a radio frequency oscillator which is
FIGURE 12 is a schematic representation of a gaging
?xture and electrical circuit for determining proper orien
tations of each septum in the ?nal waveguide assembly;
cupied by the adjacent closing-septum 12. Similarly,
40
variations in the diameter of iris apertures 14 and the
contour radius of rounded edges 16 thereof affect the
resonant frequency of adjacent cavities 13. It is conse
quently necessary that the foregoing dimensions be held
to close tolerances in the manufacture of the ?nished 4:5
waveguide.
,
‘
Proceeding now with a description of an improved
method of manufacturing the multiple resonant cavity
frequency modulated by a relatively low modulating fre
quency to produce a relatively large frequency deviation,
i.e., the generated output voltage of oscillator 44 as ap»
plied to cavities 38, 35 varies back and forth over a band.
of frequencies.
Electrical energy from cavities 38, 35 is extracted and":
applied by output cable 43 to the input of a voltage de-~
tector 47. The extracted energy is also applied by means;
of a T-section 48 in cable 43 through an adjustable attenuator 49 to a tunable reference cavity 51 which is Cali-
waveguide illustrated in FIGURE 1, there are ?rst formed
a plurality of identical cavity rings 11 (cavity enclosures) 50 brated in frequency. Cavity 51 consequently absorbs a;
small amount of the energy extracted from cavities 38, 35v
and applied to detector 47. The amount of energy ab~<
sorbed is dependent upon the setting of attenuator 49 while.
the frequency at which the energy is absorbed is depen-
which are conventionally cylindrical in cross section as
shown in FIGURE 3 although other cross sections are
also satisfactory. Rings 11 are fabricated from a good
electrically conducting material such as copper and are
preferably sawed to approximate length from a tube of‘ 55 dent upon the calibrated frequency setting of cavity 51..
appropriate Wall thickness or out upon a lathe, for exam
The output of voltage detector 47, i.e., a voltage signal‘
ple‘,'although said rings may also be formed by other
conventional manufacturing processes, e.g., by casting,
proportional to the energy extracted from cavities 38, 35'
diminished by the energy absorbed by reference cavity 51
as a function of frequency, is applied to vertical de?ection
forging, drawing as cups, or the like.
Rings 11 are next annealed in a hydrogen atmosphere 60 plates 52 of a cathode ray oscilloscope 53. The horizontal
de?ection plates 54 of such oscilloscope are connected to‘
and machined to close tolerances in theorder of $0.001”
commensurate with standard machine-shoppractices as
the output of sweep voltage supply 46 to provide a hori
by turning the outside ring diameter on a lathe or a cen
zontal de?ection of the oscilloscope beam which is syn
terless grinder, reaming or boring the inside ring diameter,
chronized to the frequency change of the detector output
and facing or grinding the transverse end extremities‘ to 65 signal applied to vertical de?ection plates 52. The oscil
appropriate axial length. After machining, both end ex
loscopic display produced at the viewing screen of oscillo
tremities of each ring 11 are lapped flat and smooth to
scope 53 is consequently a visual indication of the change
insure very accurate ?ts in the ?nished waveguide, and
in power transmission through cavity 38 enclosed by ring
this may be accomplished by rotating a ?at surface in
11 with respect to frequency as illustrated graphically in
intimate contact with said end extremities, preferably in
FIGURE 6A. It is to .be noted that such. display in
conjunction with an abrasive compoundwrn, for example, _
cludes a reference pip 56 due to the energy absorbed by
.
a liquid or paste form.
>
-_
. 70
I
Each cavity ring 11 is next- placed in a suitable test
reference cavity 51,.and therefore corresponding to the
calibrated frequency setting thereof.
Cavity 51 may con
?xture for gaging the electrical resonant frequency thereof.
‘ sequently be tuned until pip 56 coincides with the resonant
One such ?xture 17 as illustrated in FIGURE 4 com
peak of the oscilloscopic display as illustrated graphically
3,070,873
5
.
At this point it should be noted that the con?gurations
of the test ?xtures 17, 27 and circuit utilized for reso
nant frequency measurements in the method of the pres
ent invention are not limited to the embodiments illus
resonant frequency accordingly produced by the decrease
trated in FIGURES 4 and 5 and hereinbefore described,
as numerous other satisfactory resonant frequency measur
ing means exist which are well known to persons skilled in
the electronic art.
In order that all cavity rings 11 possess the same pre
determined operating resonant frequency in the ?nished
waveguide within very close electrical tolerances, those
cavity rings having resonant frequencies as determined
above different from such operating frequency must be
accordingly compensated. Since the resonant frequency
of a cavity varies inversely with the volume thereof, the
volumes enclosed by those cavity rings 11 having a
measured resonant frequency less than the predetermined 20
operating resonant frequency must be decreased in a
precisely controlled manner to tune the cavity resonant
frequency to operating frequency within very close elec
6
concentric with reference to ring 11. Electrode .64
and ring it are connected in series with a battery 66
through a switch 67. With switch 76 closed a uniform
metallic layer is plated upon the interior wall surfaces of
ring 11 in a well known manner. Since electroplating de
posits the metallic layer upon the interior wall surfaces
of cavity rings 11 at a very slow rate, the increase in
in FIGURE 6B, the calibrated frequency setting of cavity
51 being then equal to the resonant frequency of cavity
ring 11.
in cavity volume is easily controllable within limits of 1
part in 30,000 or more by varying the time or current,
or both. After electroplating the oversized cavity rings
11 in the foregoing manner, the resonant frequency of such
rings is again measured as by the gaging means illustrated
in FIGURE 5 to determine any remaining deviations from
operating resonant frequency.
Such electroplating and
measuring process is continued until the resonant fre
quency of the cavity ring 11 agrees with operating resonant
frequency.
‘
Tuning of undersized cavity rings 11 (i.e., cavity rings
11 enclosing too small a volume) is preferably accom
plished by increasing the volume enclosed by such rings
in a controlled manner as by means of electropolishing
the interior wall surfaces thereof. Since electropolishing
is the reverse process of electroplating as illustrated in the
trical tolerances. Similarly the volumes of undersized
cavity rings 11 having two great a resonant frequency must 25 embodiment of FIGURE 8, such electropolishing may
be increased in a controlled manner to tune same sub
stantially precisely to the standard predetermined operat~
ing frequency.
Tuning of oversized cavity rings 11 (i.e., cavity rings
11 enclosing too great a volume) may best be accom
‘best be accomplished in a similar manner with the battery
polarity reversed and plating bath electrolyte 63 replaced
by a suitable polishing bath. Since electropolishing re
moves metal at a very slow rate, just as electroplating de
30 posits metal at a very slow rate, the decrease in resonant
frequency accordingly produced by the increase in cavity
volume is easily controllable within limits of 1 part in
57 in the shape of shallow spherical segments into the
30,000 or more by appropriately varying the time or cur
peripheral wall surfaces of rings 11 to produce corre
rent or both.
sponding bulges at the interior wall surfaces of such ring
The plurality of identical septa 12 are next formed in
extending into the enclosed cavity volume as shown in 35
the improved method of manufacturing waveguides of the
FIGURE 7. Indentations 57 are preferably effected by
plished by brinelling, i.e., by pressing local indentations
character illustrated in FIGURE 1. Such septa 12 con
form to the particular cross section of the cavity rings
11 utilized in the waveguide construction and are there
depth of penetration and adapted to engage a semi 40 fore conventionally formed as circular discs having a di
ameter substantially identical to the outside diameter of
spherical forming die 61 at the interior Wall surfaces of
cavity rings 11 as shown in FIGURE 8. Each septum 12
ring 11 such that all indentations 57 are of substantially
includes a central iris aperture 14 having rounded edges
identical size. Each indentation 57 produces a small, dis
16, which aperture is conventionally circular in wave
tinct and consistent change in the cavity volume enclosed
guides of circular cross section although it is sometimes
by rings 11 sufficient to produce a change in resonant fre
desirable that said apertures be rectangular or of various
quency corresponding to an acceptable frequency toler
other con?gurations.
ance. Consequently, to tune an oversized cavity ring 11
Septa 12 are fabricated from a good electrically con
having a known frequency deviation from operating reso
ducting material and are therefore preferably cut from
nant frequency, it is only necessary to indent such ring a
predetermined number of times as calculated by dividing 50 copper plate or bar stock of appropriate size and cross
a single indenting punch 58 or annular array thereof
pressed radially inward into the outer periphery of rings
11, each punch 58 having a restricting collar 59 to limit
the total frequency deviation by the frequency change per
section followed by drilling of apertures 14, although
indentation. The indentations 57 may or may not be
symmetrically disposed and may or may not be of an even
said septum may also be formed by other well known
manufacturing processes, e.g., by casting, forging, or
number depending on the magnitude of perturbations of
the electric ?eld allowable within the cavity enclosed by
the ring 11. In addition the effect of slight out-of-round
ness in the cavity rings 11 produced by indentations 57 has
punching and blanking.
been shown not to affect frequency measurement.
Fur
thermo-re, it has been observed in practice that frequency
tolerance of substantially any shaped resonant cavity can
be easily held to 1 part in 30,000‘ or more by the fore
going indentation tuning operation without requiring a
corresponding increase in the machining accuracy of the
cavity enclosure dimensions thereby resulting in the im
portant advantage that the tuning of resonant cavities
may be precisely performed by persons unskilled in elec~
tric or metal working arts.
The volume enclosed by oversized cavity rings 11 may
.
Septa 12 are next annealed in a hydrogen atmosphere
to remove internal stresses and strains established there
in due to the foregoing cold forming operations. The
diameter and thickness of septa 12, diameter and rounded
edges 16 of iris apertures 14, are then machined to close
tolerances in the order of $0.001" commensurate with
standard machine shop practices as by turning the septum
diameter to the outside diameter of cavity rings 11 on
a lathe or centeriess grinder, turning the aperture diameter
and forming rounded edges 16 on aisle, and facing or
grinding the septa end faces to suitable thicknesses. After
the above machining operations the septum end faces are
lapped ?at and smooth to insure very accurate ?ts in the
?nished waveguide, and this may ‘be accomplished by
rotating a ?at surface in intimate contact with said end
also be uniformly decreased in a controlled manner by
depositing additional metal in controlled amounts on the 70 faces, preferably in conjunction with an abrasive com
pound in, for example, a liquid or paste form.
interior wall surfaces of such rings by means of electro
Each septum 12 is next gaged electrically to determine
plating as shown in FIGURE 7. The cavity rings 11 are
deviations in the transmissive resonant frequency of iris
suspended in a tank 62 containing a suitable electrolyte
63 (plating bath). An elongated electrode 64 fabricated
apertures 14 from the hereinbefore mentioned predeten
for example from copper isalso suspended within tank 62
mined waveguide operating resonant frequency in a man
3,670,879?
8
ner similar to that previously described in relation to
cavity rings 11. Said gaging may be best accomplished
by placing each septum 12 in a gaging ?xture 68 as illus
trated in FIGURE 10. As shown therein, ?xture 68 com
prises a pair of standard cavity rings 69 having said pre
determined operating frequency one disposed coaxially
adjacent each end face of a septum 12 to be tested. Stand
ard electrically conducting end plates 71, 72 each provided
with a central axial half iris 73 are respectively disposed in
1 part in 30,000 or more by varying the time and/or
current employed in the electropolishing process.
Electroplating of the rounded edges 16 of oversized
apertures 14 is similarly employed to decrease the reso
nant frequency thereof in proportion to the amount of
metal deposited by utilizing electrolysis structure similar
to that illustrated in FIGURE 11 and described above
in regard to electropolishing but wherein electrolyte 87
is suitable for plating (i.e., a plating bath) and the polarity
closing relationship at the open end extremities of rings 10 of battery 91 is reversed. The same degree of control
69 to form a pair of coaxially adjacent resonant cavities
of resonant frequency change is possible with electro
74 coupled by means of the test septa iris aperture 14 thus
plating as with electropolishing (i.e., 1 part in 30,000 or
simulating the ?nished waveguide structure, and the entire
more) by varying the time and/or current employed in
?xture assembly so formed is rigidly clamped under axial
the plating process. It is advantageous to plate su?icient
force as shown generally at '76.
One plate 72 is ?tted t. . Q7: metal upon edges 16 of oversized iris apertures 14 to
with conventional excitation and pickup loop connectors
77, 78 respectively terminating in input and output coaxial
decrease the resonant frequency thereof below operating
resonant frequency such that electropolishing of rounded
edges 16 may be ?nally employed to precisely tune said
cables 79, 81 to admit and extract electrical energy from
septa to operating resonant frequency. Electropolishing,
the axially coupled cavities 74.
'
Deviations in the transmissive resonant frequency of 20 in addition to providing a means of precisely tuning septa
12 to operating resonant frequency, produces a high
iris aperture 14 of test septum 12 from standard operat
ing resonant frequency may be determined by numerous
degree of smoothness upon aperture rounded edges 16
thus minimizing voltage breakdown ‘between adjacent
methods familiar to persons skilled in the electronics art,
e.g., by means of the measuring circuit as illustrated for
the sake of simplicity in FIGURE 10 wherein gaging
septa in the ?nished waveguide assembly.
.
After electropolishing septa 12, the resonant frequency
?xture 68 is excited by a calibrated variable frequency
oscillator 82 coupled to input coaxial cable 79 and the
thereof is again measured as by means of the gaging
?xture 63 and measuring circuit illustrated in FIGURE 10
to determine any remaining deviations from operating
response of said ?xture is observed at a suitable radio
resonant frequency and such deviations are appropriately
frequency power indicator 83 (e.g., a crystal detector,
bolometer, or simple radio receiver) connected to out 30 compensated for by further electropolishing or electro~
plating followed by electropolishing until subsequent
put coaxial cable 81.
The measuring procedure then consists in varying the
frequency of oscillator 32 and observing the calibrated
frequency setting at which indicator 83 indicates maxi
measuring indicates resonant frequencies in agreement
with operating resonant frequency.
mum response of ?xture 68.
by cavity rings 11 interposed between transversely dis
Greater accuracy may be
Since the resonant frequency of the cavities formed
obtained however by considering the resonant frequency
posed septa 12, although tuned to a common operating
to be the mean of two frequencies on either side of reso
nance at which the indicated response is less than at
resonance by some speci?ed amount such as 3 decibels.
resonant frequency as hereinbefore described, is affected
Septa 12 having resonant frequencies deviating from
40 assembly is next determined to minimize differences
operating resonant frequency as indicated by the fore
going measuring procedure must be accordingly compen
sated.
Septa having too small or too great an associated
by the ?atness of the faces of said septa, appropriate
orientation of each septum 12 in the ?nal waveguide
in resonant frequency between adjacent cavities. The
foregoing is best accomplished by placing each septum
12 in a test ?xture 93 as shown in FIGURE 12.
Fixture
resonant frequency respectively indicating undersized and
93 comprises a non-resonant cavity enclosure 94 disposed
oversized diameters of iris apertures 14 may be accord
ingly tuned to operating resonant frequency within very
close electrical tolerances by removing or depositing
small controlled amounts of metal uniformly at rounded
edges 16 thereof preferably by means of electropolishing
or electroplating followed by electropolishing.
Undersized septa iris apertures may best be electro
polished as illustrated in FIGURE 11. Each septum
12 is rigidly interposed between two annular “thief” elec
trodes 84 disposed coaxial with reference to iris aperture
14 and having inner wall surfaces intersecting rounded
coaxially adjacent one end face of a septum 12 to be
oriented forming a non-resonant cavity 96 therewith,
and a standard cavity ring 97 (i.e., having a resonant
edges 16 circumferentially. The resulting assembly is
frequency equal to operating resonant frequency) coax
ially disposed between the other end face of said septum
and a standard transverse end plate 98 thereby forming
a resonant cavity 99. The entire ?xture assembly 93 is
clamped under axial force as shown generally at 101
and end'plate 98 is provided with conventional excitation
and pickup loop connectors 102, 103 respectively ter
minating in input and output coaxial cables 104, 106.
suspended in a tank 86 containing an electrolyte 87,
A calibrated variable frequency oscillator 107 is con
nected to input cable 104 to excite cavity 99 and the
suitable for electropolishing (i.e., a polishing bath). An
response thereof is observed at a suitable radio fre
elongated cylindrical electrode 88 having a reduced center
quency power indicator 108 (e.g., a crystal detector,
section 39 and conventionally fabricated from the same 60 bolometer, or simple radio receiver) connected to output
coaxial cable 106. The frequency of oscillator 107 is
material as septa 12 is suspended coaxially symmetrical
then varied and the calibrated frequency setting is
within the submerged septum 12 and thief electrode assem
observed at resonance which corresponds to maximum
bly. Electrode 88 is singly connected and one thief elec
response of ?xture 93 as indicated by indicator 108.
trode 84 and septum 12 are commonly connected in series
with a battery 91 through a switch 92. With switch 92 65 Since the frequency of a resonant cavity coupled to a
non-resonant cavity is very sensitive to the ?atness of
closed, metal is uniformly removed from the rounded
the coupling septum, the resonant frequency of cavity
edges 16 of aperture 14 by electrolysis; removal of metal
99 is measured with septum 12 oriented ?rst with one
from the remaining portions of septum 12 being pro
end face and then the other end face adjacent cavity 96.
hibited by the shielding effects of thief electrodes 84.
As was previously mentioned in regard to electropolish 70 The out-of-?atness of septa 12 being essentially conical
ing of the interior wall surfaces of cavity rings 11, such
in nature, i.e., septa 12 are minutely deformed into cones
truncated at iris apertures 14, results in cavity 99 having
electropolishing process removes metal at a very slow
slightly less volume at one orientation of said septa
rate. Consequently the increase in size of aperture 14
than at the other. The corresponding measured resonant
and therefore the corresponding increase in associated
resonant frequency is easily controllable within limits of
frequencies of cavity 99 consequently di?er slightly for
3,070,873
each orientation of septum 12. For example, the cali-_,
brated frequency setting of oscillator 107 at resonance
may be 300 me. for one end face of a particular septum
1f)
the contacting surfaces of cavity rings 11 and septa 12
and in effect welding same together into one mass.
It
has been illustrated in practice that such diffusion welded
joints possess excellent electrical properties and mechani
cal strength, however, they are porous to high vacuum.
Consequently, upon completion of the diffusion process,
12 adjacent cavity 99 while being 300.1 rnc. for the other
end face of said septum adjacent cavity 99. Since the
out-of-‘latness of each septum 12 (i.e., the taper of the
the temperature of the waveguide assembly is raised to
minute conical deformations) should be in the same direc
melt the brazing alloy 137 which in turn flows to seal
tion in the ?nished waveguide assembly to minimize dif
each joint vacuum-tight. After the solder has ?owed, the
fereuces between the resonant frequencies of adjacent
cavities, the direction of out-of-?atness of each septum 10 assembly is cooled and removed from clamping ?xture
109 thus resulting in the ?nished multiple resonant cavity
12 is accordingly noted as by marking the periphery
thereof with a small notch at the end face producing,
waveguide assembly.
‘
It will be appreciated that various other methods exist
for joining the cavity rings 11 and septum 12 into an
same predetermined operating resonant frequency and a 15 integral waveguide assembly, however, such methods are
variously disadvantageous. For example, diffusion joints
common orientation of said septa noted, said rings and
between adjacent cavity rings 11 and septum 12 may be
septa are coaxially aligned in ?nal waveguide assembly
obtained by utilizing a noble metal such as gold in the
relationship as by alternately placing rings and septa upon
form of electroplated layers upon the surfaces to be joined
V-blocks or parallel bars, septa 12 being oriented with
marked end faces facing the same axial direction. The 20 and applying heat and/or pressure thereto; such noble
metal maintaining oxide-free surfaces while being heated.
cavity rings 11 and septa 12 are next axially compressed
The previously described diffusion joining method is con
as by means of a clamping ?xture 109 adapted to exert
sequently preferred in that the tedious, more expensive,
uniform pressure axially inward as shown in FIGURE 13.
electroplating of noble metal upon the surfaces to be
Clamping ?xture 109 is fabricated entirely from heat
resistant alloy such as stainless steel and comprises an 25 joined in the latter process is eliminated.
There has been described hereinbefore an improved
elongated tie rod 111 threaded at both end extremities
method of constructing waveguides and the like which has
which is inserted through the axially aligned iris apertures
been illustrated and described in connection with but
14 of septa 12. Cylindrical intermediate plates 112, 113
for example, the highest observed resonant frequency.
With all cavity rings 11 and septa 12 tuned to the
respectively having annular peripheral shoulders 114, 116
some of many possible embodiments and with respect to
annular axially projecting rims 127, 128 respectively bear
ing against intermediate plate shoulders 114, 117. A
prising a plurality of axially aligned cavity rings and
and 117, 118 in each end face thereof and central axial 30 speci?c steps and structure, however same are presented
as illustrative only of certain embodiments of the inven
bores 119, 121 engaging tie rod 111 are respectively
tion. Another example of structure to which the herein~
disposed adjacent the end extremities of the waveguide
before described precision method of constructing elec
assembly. The end faces of the end cavity rings 11 re
trically resonant cavities and coupling partitions for the
spectively interlock with shoulders 116, 118 while cylin
transmission of radio frequency power may be advan
drical end plates 122, 123 having central axial bores 124,
tageously applied is a waveguide buncher assembly com
126 respectively engaging tie rod 111 are provided with
cylindrical compression equalizer plate 129 including a
coupling septa constructed in such manner that the said
cavities possess different predetermined resonant fre
priately tightened to accordingly back-off equalizer plate
central iris apertures therethrough, (2) electrically test
129 until the axial spacing of same from end plate 123 is
circumferentially uniform as indicated for example by
frequency thereof, (3) comparing said resonant frequen
a plurality of identical circumferentially spaced microm
eter readings thereby indicating uniform axial compres
determine deviations therefrom, (4) altering the interior
central axial bore 131 engaging tie rod 111 is disposed 40 quencies and radio frequency transmission characteristics
which vary uniformly from cavity to cavity along the
coaxially adjacent end plate 123 and nuts 132, 133 are
axis. The foregoing illustrations are to be taken only as
threadably secured to the end extremities of tie rod 111
examples and in no way limiting the scope of the inven
and cinched tight against end plate 122 and equalizer
tion which is precisely delineated in the following claims.
plate 129 respectively. To insure that such compression
What is claimed is:
is uniform over the entire mating surface area of each
11. A method of producing a multiple cavity waveguide
adjacent pair of rings 11 and septa 12, a plurality of an
comprising the steps of ( 1) forming from electrically
nularly spaced back-off bolts 134 are provided in equal
conducting material a plurality of similar enclosures hav
izer plate 129 extending through threaded bores 136 to
ing open ends and a plurality of ?at septa conforming
bear against end plate 123 at points axially aligned with
the end faces of cavity rings 11. Bolts 134 are appro 50 to the exterior cross section of said open ends and having
sron.
The clamped cavity rings 11 and septa 12 are now in
tegrally joined together to form the finished waveguide
and this may be best accomplished by diffusion welding
the mating surfaces of said rings and septum followed by
brazing of the welded joints to provide vacuum tightness.
The foregoing joining process is accomplished by ?rst
placing a suitable brazing alloy 137 (e.g., in the case of
copper rings and septum solder of composition 72%
Ag—28% Cu) in intimate contact with each juncture of
the clamped cavity rings 11 and septa 12. Such brazing
alloy 137 may be applied in paste form, as power com
bined with a suitable binder, or as foil or ribbon tied
about or preformed into rings slipped over said junctures
as illustrated in FIGURE 13. The clamped assembly
including brazing alloy 137 is next placed in a reducing
atmosphere, such as hydrogen or “forming gas” (i.e.,
95% N2+5% H2), to prevent oxides from forming on
ing each of said enclosures to determine the resonant
cies to a predetermined operating resonant frequency to
volume of said enclosure as required to produce reso
nance thereof at said operating frequency, (5) repeating
steps (2), (3), and (4) alternately until said enclosures
resonate at said operating frequency, (6) electrically
testing the iris apertures of each septum to determine the
transmissive resonant frequency thereof, (7) comparing
said transmissive resonant frequency to said operating
frequency to determine deviations therefrom, (8) alter
ing the size of said apertures as required to produce reso
nance thereof at said operating frequency, (9) repeating
steps (6), (7), and (8) alternately until said septa aper
tures resonate at said operating frequency, (10) deter
mining the axial direction of out-of-?atness deformation
of each one of said septa, and (11) assembling said en
closures and ‘said septa all oriented in the same direction
of out-of-flatness in alternate coaxial relationship.
2. The method de?ned by claim 1 further de?ned by
step (4) consisting in controllably indenting the walls of
said enclosures determined to deviate below said operat~
the surfaces to be joined and heated to 450° C.—600° C.
for several hours thus causing diffusion to occur between 75 ing frequency from the exterior to precisely reduce the
3,070,879
f2
internal volumes of said enclosures and provide a reso
nant frequency thereof equal to said operating frequency,
and electropolishing the walls of said enclosures deter
mined to deviate above said operating frequency to uni
frequency, (7) interposing each one of said septa be-'
tween identical cavity enclosures resonate at said operat
ing frequency, (8) energizing the interior of said cavity
enclosures with a radio frequency ?eld, (9) repeating
formly remove metal therefrom in controlled amounts
steps (3), (4), (5), (l0) altering the size of saidsepta
thereby precisely increasing the internal volumes of said
enclosures and providing a resonant frequency thereof
iris apertures as required to produce peak response at
said operating frequency, (11) interposing each one of
equal to said operating frequency.
3. The method de?ned by claim 1 further de?ned by
step (8) consisting in electropolishing the edge surfaces
said septa between a non-resonant cavity enclosure and
a cavity enclosure resonant at said operating frequency,
( 12) energizing the interior of said cavity enclosures
with a radio frequency ?eld, (l3) repeating steps (3)
and (4), ( 14) rotating each of said septa transversely
upside down and repeating steps (l1), (l2), and (13),
(15) marking the septum end face noted to produce
peak response at greatest frequency, (16) and assembling
of septa iris apertures determined to produce transmis~
sive resonant frequencies deviating below said operating
frequency whereby metal is uniformly removed from said
surfaces in precisely controlled amounts to tune said
apertures to said operating frequency Within close elec
trical tolerances, and electroplating the edge surfaces of
septa iris apertures determined to produce transmissive
resonant frequencies deviating above said operating fre
quency whereby metal is uniformly deposited upon said
said enclosures and septa in alternate coaxial relation
ship, said septa marked end faces oriented in the same
axial direction.
6. A method as de?ned by claim 5 further character
surfaces in precisely controlled amounts to tune said aper 20 ized by step 10 consisting in electroplating the edge sur
tures to said operating frequency within close electrical
faces of septa iris apertures producing peak response
tolerances.
'
at frequencies greater than said operating frequency, re
peating steps (7), (8), (9) alternately with the foregoing
' 4. In the manufacture of multiple cavity waveguides
formed of a plurality of cavity enclosures and inter
posed septa having axial iris apertures provided therein,
the method ‘consisting of (1) individually electrically
step until peak response is produced at a frequency less
25
than said operating frequency, electropolishing the edge
surfaces of septa iris apertures producing peak response
at frequencies less than said operating frequency, and
repeating steps (7), (8), (9)‘ alternately with the im
mediately preceding step until peak response is produced
at said operating frequency.
comparing the resonant frequency’ of said enclosures
with a predetermined operating resonant frequency, (2)
controllably impressing identical local indentations into
the periphery of enclosures having resonant frequencies 30
less than said operating frequency to‘ form correspond
7. A method as de?ned by claim 5 further character
ing bulges at the interior wall surfaces thereof, (3) repeat
ized by step (6) comprising electroplating the inner wall
ing steps (1) and (2) alternately until said enclosures
surfaces of enclosures producing peak response at fre
resonate at said operating frequency, (4) electropolishing
quencies less than said operating frequency, repeating
the interior walls of enclosures having resonant fre 35 steps (2), (3), (4), (5) alternately with the immediately
quencies greater than said operating frequency, (5) re
peatiug steps (1) and (4) alternately until the resonant
frequency of said enclosures is -in agreement with said
operating frequency, (6) electrically comparing the
resonant frequency of transmission of said septa iris aper 40
tures to said operating frequency, (7) electropolishing
the edge surfaces of septa apertures having resonant fre
preceding step until peak response is produced at said
operating frequency, electropolishing the inner wall sur
faces of enclosures producing peak response at frequencies
greater than said operating frequency, and repeating
steps (2), ‘(3), (4), (5) alternately with the immediately
preceding step until peak response is produced at said
operating frequency.
quencies less than said operating frequency, (8) repeat
' 8. A method as de?ned by claim 5 further de?ned by
ing steps (6) andv (7) alternately until the resonant fre~
step (6) consisting in controllably impressing identical
quency of said septa apertures is equal to said operating '
local indentations into the periphery of enclosures pro
ducing peak response at frequencies less than said operat
ing frequency to form corresponding bulges at the interior
frequency, (9) electroplating the edge surfaces of septa
apertures having resonant frequencies greater than said
operating frequency, (10) repeating steps (6) and (9)
alternately until the resonant frequency of said septa
apertures is less than said operating frequency followed
by step (8), (11) determining the axial direction of out
of-?atness deformation of each one of said septa, (12)
placing said enclosures and said septa in alternate coaxial
juxtaposition, (13) orienting said septa inthe same di
rection of out-of-flatness, (14) axially clamping said en 55
closures and septa, (15) diffusion welding together said
clamped en :losures and septa to obtain diffusion welded
joints therebetween, said diffusion welded joints being
wall surfaces thereof, repeating steps (2), (3), (4), (5)
alternately with the foregoing step until peak response
is produced at said operating frequency, electropolishing
the interior wall surfaces of enclosures producing peak
response at frequencies greater than said operating fre
quency, and repeating steps (2), (3), (4), (5') alternate
ly with the foregoing step until peak response is produced
at said operating frequency.
9. In the manufacture of multiple cavity waveguides
formed of a plurality of cavity enclosures and interposed
septa having axial iris apertures provided therein, the
porous to vacuum, (16) brazing the porous diffusion
method consisting in closing each one of said enclosures
welded septum-enclosure joints to vacuum seal the same, 60 and energizing same with a variable radio frequency ?eld
and (17) unclamping said joined septa and enclosures.
5. A method of producing a multiple cavity waveguide
simultaneously while observing the frequency response of
said enclosure to determine the frequency at which peak
having a plurality of axially aligned open ended cavity
response occurs, comparing the resonant frequencies so
enclosures separated by centrally apertured transverse
determined to a predetermined operating resonant fre
septa comprising the steps of (1) forming ‘from elec
quency and determining deviations therefrom, electro
polishing the interior Wall surfaces of enclosures deviating
closures and flat septa with central apertures therethrough,
above said operating frequency to produce a change in
(2) closing each of said enclosures and energizing the
resonant frequency compensatory to the deviation, con
interior volume thereof with a radio frequency ?eld, (3)
trollably indenting the Walls of enclosures deviating below
varying the frequency of, said ?eld simultaneously while 70 said operating frequency from the exterior as required to
observing the frequency response of said enclosures, (4)
produce a change in resonant frequency compensatory to
noting the frequency producing peak response, (5) com
the deviation, interposing each septum between identical
paring said frequency to a predetermined operating fre~
cavities resonant at said operating frequency, energizing
quency, (6) altering the interior volume of said enclosures
said septum coupled cavities with a variable radio fre
as required to produce peak response at said operating
quency ?eld simultaneously while observing the frequency
trically conducting material a plurality of similar en
3,670,873
33
14
wall surface of each enclosure to uniformly deposit metal
thereon in controlled amounts and thereby precisely de
crease the internal volume of said enclosure, and step
(15) consisting in electropolishing .the aperture edge sur
response of said cavities to determine the frequency at
which peak response occurs, comparing the septa aper
ture resonant frequencies so determined to said operat
ing resonant frequency and determining deviations there
face of each septum to uniformly remove metal there
from, selectively electroplating and electropolishing the
from in controlled amounts and thereby precisely in
crease the aperture size.
aperture edge surfaces of septa deviating from said oper
ating frequency to produce corresponding changes in
12. A method as de?ned by claim 10 further de?ned
resonant frequency compensatory to the deviations, in
terposing each septum between a cavity resonant at said
operating frequency and a non-resonant cavity, energizing
said cavities with a variable radio frequency ?eld while
observing the frequency response of said cavities to de
termine the frequency producing peak response, orient
ing said septum transversely upside down between said
by step (10) consisting in controllably impressing iden-.
tical local indentations into the periphery of each en
closure to form corresponding bulges to the interior wall
surface thereof and thereby decrease the internal volume
of said enclosure in precise incremental steps, and step
(15) comprising electropolishing the aperture edge sur
cavities and repeating the immediately preceding step, 15 face of each septum to uniformly remove metal there
from to controlled amounts and thereby precisely in
marking the septum end face orientation producing peak
response at greatest frequency, and assembling said en
crease the aperture size.
closures and septa similarly oriented with reference to
the end faces thereof in rigid pressure sealed alternate
13. A method of manufacturing multiple cavity Wave
guides comprising the steps of providing a plurality of
metallic cavity enclosures having open ends, providing
coaxial relationship.
10. A method of manufacturing multiple cavity wave
guides comprising the steps of (1) providing a plurality
of cavity enclosures having open ends, (2) providing a
‘plurality of septa conforming to said open ends and each
including a central axial aperture, (3) machining the
length and outer periphery of said enclosures respeztively
identical within close tolerances, (4) machining the in
a plurality of metallic septa conforming to said open ends
and each including a central axial aperture, machining
the length and outer periphery of said enclosures respec
tively identical within close tolerances, machining the
25 interior dimensions of each of said enclosures to predeter
mined dimension commensurate with a predetermined
operating frequency within close tolerances greater than
said predetermined dimensions, machining the periphery
terior dimensions of each of said enclosures to predeter
mined dimensions commensurate with a predetermined
operating frequency within close tolerances greater than
said predetermined dimensions, (5) machining the periph
ery of said septa‘to conform to the outer periphery of
30
of said septa to conform to the outer periphery of said
enclosures within close tolerances, machining the dimen
sions of each of said septa apertures to predetermined
dimensions commensurate with said operating resonant
frequency within close tolerances less than said predeter
mined dimensions, annealing said enclosures and septa,
determined dimensions commensurate with said operating 35 honing the transverse faces of said enclosures and said
septa flat and smooth, energizing each one of said en
resonant frequency within close tolerances less than said
said enclosures within close tolerances, (6) machining
the dimensions of each of said septa apertures to pre
predetermined dimensions, (7) annealing said enclosures
closures with a variable radio frequency ?eld simultane
ously while observing the frequency response of said
and septa in a reducing atmosphere, honing the transverse
enclosure to determine the frequency at which peak re
faces of said enclosures and said septa ?at and smooth,
(8) closing each one of said enclosures and energizing 40 sponse occurs, comparing the resonant frequencies so
determined to said operating resonant frequency to deter
same with a variable radio frequency ?eld simultaneously
mine deviations therefrom, repetitiously positioning a
while observing the frequency response of said enclosure
spherical surface adjacent the periphery of each of said
to determine the frequency at which peak response oc
enclosures, positioning a forming die adjacent the interior
curs, (9) comparing the resonant frequencies so deter
mined to said operating resonant frequency to determine 45 wall surface of said enclosure diametrically opposed to
said spherical surface, applying pressure to said surface
deviations therefrom, (l0) decreasing the internal volume
to impress same into the periphery of said enclosure,
of each enclosure, (11) repeating steps (8) and (9)
limiting the depth of penetration of said surface into said
alternately with step (10) until the resonant frequency
periphery, continuing the impressing process until suf
of said enclosure is equal to said operating frequency,
(12) interposing each septum between identical resonant 50 ?cient bulges are formed at the interior wall surface of
each enclosure to compensate said deviations from oper
cavities having said operating resonant frequency, (13)
ating resonant frequency within close electrical toler
energizing said septum coupled cavities with a variable
ances, interposing each of said septa between identical
radio frequency ?eld simultaneously while observing the
resonant cavities having said operating resonant fre
frequency response of said cavities to determine the fre
quency, energizing said septum coupled cavities with a
quency at which peak response occurs, (14) comparing
the septa resonant frequencies so determined to said
operating resonant frequency and determining deviations
therefrom, ( 15) increasing the aperture size of each
variable radio frequency ?eld simultaneously while ob
serving the frequency response of said cavities to deter
septum, (16) repeating steps (12), (13), (14) alter
mine the frequency at which peak response occurs, com
paring the septa resonant frequencies so determined to
posing each septum between a cavity resonant at said
face of each septum until‘ an amount of metal is removed
nately with step (15) until the resonant frequency of said 60 said operating resonant frequency and determining devia
tions therefrom, electropolishing the aperture edge sur
septum is equal to said operating frequency, (17) inter
producing a change in the resonant frequency thereof
compensatory to said deviation from operating resonant
energizing said cavities with a variable radio frequency
?eld while observing the frequency response of said 65 frequency, interposing each of said septa between a non
resonant cavity and a cavity resonant at said operating
cavities to determine the frequency producing peak re
frequency, energizing said cavities with a variable radio‘
sponse, (19) orienting said septum transversely upside
frequency ?eld while observing the response of said cav
down and repeating steps ( 17) and (18), (20) marking
ities to determine the frequency producing peak response,
the septum end face orientation producing peak response
at greatest frequency, and (21) and assembling said en 70 orienting said septum transversely upside down between
said cavities and repeating the preceding step, marking
closures and septa similarly oriented with reference to
the septum end face orientation producing peak response
the marked end faces thereof in rigid pressure sealed
at greatest frequency, placing the cavity enclosures and
alternate coaxial relationship.
said septa in alternate coaxial juxtaposition with the septa
11. A method as de?ned by claim 10 further character
operating frequency and a non-resonant cavity, (18)
ized by step (10) consisting in electroplating theinterior 75 in similar marked end face? orientation, axially clamping
16>
15
said enclosures and septa, contacting brazing alloy about
ical surface‘ adjacent the periphery of each cavity ring
each seam formed by abutting surfaces of said enclo
sures and septa, placing said clamped enclosures and
septa in a reducing atmosphere and applying heat main
tained at a temperature below the melting point of said
valloy'to diffusion weld said abutting surfaces, the result
ing diffusion welded seams porous to vacuum, raising
the temperature of said heat to at least the melting point
of said alloy to flow same around said welded surfaces
and vacuum seal the welded seams, cooling said joined
enclosures and septa, and removing the clamp means
determined to deviate below said operating frequency,
(11) applying pressure to said surface to impress same
therefrom.
14. A method of manufacturing multiple resonant
cavity waveguides comprising the steps of providing a
length of metallic tubing, transversely cutting said tub
said operating frequency, (16) repeating steps (6), (7),
into said periphery, (12) limiting the depth of penetra
tion into said periphery by said surfaces whereby bulges
are formed at the interior wall surfaces of said cavity
rings, (13) forming said bulges to identity, (14) repeat
in steps (10), (11), (12), (13) alternately with steps
(6), (7), (8), (9) until the cavity ring is resonant at
said operating frequency, (15) electropolishing the interior
wall surface of each ring determined to deviate above
(8), (9) alternately with step (15) until the ring is res
onant at said operating frequency, (17) providing a
15 length of copper bar stock having a cross section con
forming to the outer cross section of said cavity rings,
(18) cutting said bar stock at equal axial increments to
form a plurality of septa, (l9) drilling an axial iris aper
ture in each one of said septa, (20) machining said septa
iris apertures to round the edges thereof, (21) ?nish
machining said septa to identical dimensions within close
tolerances and in conformity to the exterior cross section
ing at equal axial increments to form a plurality of elec
trically conducting cavity rings, machining said cavity
rings to identical dimensions within close tolerances, an
nealing said rings in a hydrogen atmosphere to remove
vstresses and strains therein, honing the end faces of said
cavity rings ?at and smooth, electrically testing each of
said cavity rings to determine the resonant frequency
of said machined cavity rings, (22) annealing said septa
thereof, comparing said resonant frequencies to a pre
determined operating resonant frequency to determine de
in a hydrogen atmosphere to remove all stresses and
jviations therefrom, electropolishing the interior wall sur 25 strains therein, (23) honing the faces of said septa flat
and smooth, (24) clamping each of said septa in inter
faces of said cavity rings having resonant frequencies
position between a pair of like cavities resonant at said
operating frequency, ' (25) energizing said septum coupled
cavities with a variable radio frequency ?eld simultane
greater than said operating resonant frequency to tune
‘same to said operating resonant frequency, electroplating
the interior wall surfaces of said cavity rings having res
onant frequencies less than said operating resonant fre 30 ously while observing- the frequency response of said
cavities to determine the frequency producing peak re
quency to tune same to said operating resonant fre
sponse, (26) comparing the septum resonant frequencies
quency, providing a length of metallic bar stock having a
so determined to said operating resonant frequency to
cross section conforming to the outer cross section of said
determine deviations therefrom, (27) removing said septa
rings, cutting said bar stock at equal axial increments
to form aplurality thin septa, drilling an axial aperture
‘in each of said septa, machining said septa apertures to
round the edges thereof, ?nish machining said septa to
35
identical dimensions within close tolerances and in con
from said cavities, (28) electroplating and electropolishing
the aperture edge surfaces of septa determined to deviate
above and below said operating frequency respectively,
(29) repeating steps (24), (25), (26), (27) alternately
with step (28) until the resonant frequency of each sep
tum is in agreement with said operating frequency, (29)
formity to said machined cavity rings, annealing said
‘septa in a hydrogen atmosphere to remove stresses and
strains therein, honing the faces of said septa flat and
smooth, electrically testing each of said septa to deter
mine the resonant frequency thereof, comparing said
clamping each of said septa in interposition between a
non-resonant cavity and a cavity resonant at said op
resonant frequencies to said predetermined operating res
onant frequency to determine deviations therefrom, elec
coupled cavities with a variable radio frequency ?eld si
multaneously while observing the response of said cav
tropolishing the round aperture edges of said septa hav
ing resonant frequencies less than said operating fre
ities to determine the frequency producing peak response,
(31) orienting each septum upside down between said
quency to tune same to said operating resonant frequency,
cavities, (32) repeating step (30), (33) marking the
erating resonant frequency, (30) energizing said septum
septum end face orientation producing peak response at
electroplating the rounded aperture edges of said septa
having resonant frequencies greater than said operating 50 greatest frequency, (34) placing said cavity rings and
said septa in alternate coaxial juxtaposition with the septa
frequency to tune same to said operating resonant fre
in similar marked end face orientation, (35) axially
"quency, determining the axial direction of out-of-?at
clamping said cavity rings and septa to establish intimate
ness deformation of each septum, and assembling said
contact therebetween, (36) contacting silver solder wire,
.cavity rings and said septa in alternate coaxial relation
"ship, said septa oriented in the same direction of de 55 about each seam formed by abutting surfaces of said
cavity rings and septa, (37) placing said clamped rings
formation.
and septa in a reducing atmosphere and applying heat
15. A method of manufacturing multiple resonant cav
maintained at a temperature of between 450° C. to 600°
ity waveguides comprising the steps of (1) providing a
'length of copper tubing, (2) transversely cutting said
C. below the melting point of said silver solder wire for
tubing at equal axial increments to form a plurality of 60 several hours whereby diffusion occurs between said
abutting surfaces and porous diffusion welded seams are
electrically conducting cavity rings, (3) machining said
produced therebetween, (38) raising the temperature of
[cavity rings to identical dimensions within close toler
ances, (4) annealing said rings in a hydrogen atmosphere
-to remove all stresses and strains therein, (5) honing the
"end faces of said cavity rings ?at andsmooth, (6) clamp
said heat to at least the melting temperature of said
silver solder to ?ow same around said seams to estab
65
ing flat metallic plates at the end extremities of each
ring to form a resonant cavity therewith, (7) energizing
said cavity with a variable radio frequency ?eld simul
taneously while observing the response of said cavity to
determine the frequency at which peak response occurs, 70
lish pressure sealed diffusion welded joints, (39) cool
ing said cavity rings and septa, (40) and removing the
‘clamp means therefrom.
16. A multiple cavity waveguide, comprising a plurality
of metallic cavity enclosures having open ends, said en
determined to a predetermined operating resonant fre
closures having interiorly projecting self-supporting sub
stantially hemispherical indentations of substantially
equal size in respective quantities rendering their elec
quency to determine deviations therefrom, (9) removing
trical equivalent volumes identical within tolerances of 1
‘(8) comparing the cavity ring resonant frequencies so
part in 30,000, and a plurality of ?at metallic septa con
said metallic plates from the end extremities of said
cavity rings, > ‘(10) Iepetitiouslty positioning a hard spher 75 forming to the exterior cross-section of said enclosures
3,070,873
17
disposed in alternate coaxial succession therewith and
secured to the open ends of adjacent ones thereof, said
septa having iris apertures with electropolished surround
ing edge surfaces, and apertures being electrically identi
18
References Cited in the ?le of this patent
UNITED STATES PATENTS
cal within tolerances of 1 part in 30,000.
2,126,074
2,195,314
2,228,087
Wissler ______________ __ Aug. 9, 1938
Lincoln _____________ __ Mar. 26, 1940
Rose _________________ __ Jan. 7, 1941
17. Method of tuning oversized cavity rings compris
ing the following steps: placing a brinelling die at the
2,382,549
2,567,701
Edmonson ___________ .._ Aug. 14, 1945
Fiske _______________ __ Sept. 11, 1951
interior wall surface of such a ring, placing an indent
ing punch corresponding to said die at a corresponding 10
portion of the exterior wall surface of said ring, and
2,602,146
2,629,066
2,629,774
2,649,576
2,662,277
2,725,353
2,749,523
2,777,193
2,779,993
2,787,766
2,817,813
2,824,289
2,892,958
Ludi _________________ __ July 1,
Eitel et a1 _____________ __ Feb. 17,
Longacre ____________ __ Feb. 24,
Lewis _______________ __ Aug. 18,
Stone _______________ __ Dec. 15,
Strobel ______________ __ Nov. 29,
Dishal ______________ __ June 5,
Albright et a1 __________ __ Jan. 15,
Pityo ________________ __ Feb. 5,
Scheftelowitz _________ __ Apr. 2,
Rowen et a1. _________ __ Dec. 24,
Murdock _____________ __ Feb. 18,
Nygard ______________ __ June 30,
pressing said punch radially inward into said exterior
Wall surface, said punch having a restricting collar to
limit depth of penetration.
18. Method of tuning oversized cavity rings compris
ing the following steps: placing a brinnelling die at the
interior wall surface of such a ring, placing an indenting
punch corresponding to said die at a corresponding por
tion of the exterior wall surface of said ring, pressing
said punch radially inward into said exterior wall sur 20
face, said punch having a restricting collar to limit depth
of penetration, and repeating said steps a predetermined
number of times as calculated by dividing the total fre
quency deviation by the frequency change per indentation.
1952
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OTHER REFERENCES
Hassell et al.: “Electroforming Waveguide Compo
nents,” Electronics, March 1946, pages 134-138.
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