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Патент USA US2406364

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Filedl Nov. e, 1941v
H. 7.' FRI/S
/NvE/vroRs y C, R/DEOÈUT
Patented Aug. 27, 1946
Harald .T. Friis, Rumson, and Vincent C. Rideout,
Red Bank, N. J., assignors to Bell Telephone
Laboratories, Incorporated, New York, N. Y., a
corporation of New York
Application November 6, 1941, Serial No.` 418,018
4 claims.
(ci. 25o-36)
This invention relates to vacuum tube `oscilla
tors and more particularly to oscillators for the
generation of ultra-high frequency currents for
which the corresponding wave-lengths may be
comparable to the dimensions-ofl the Vacuum tube
electrodes and their associated leads.
The principal objects of the `invention are to
ensure the establishment of the oscillation fre
quency at a definite desired value and to prevent
the generation of oscillations at frequencies other
than that desired. Another object is to improve
the efñciency of ultra-short wave oscillation of
the feedback type.
When the frequency of oscillation corresponds
to a wave-length of the order of 10 centimeters
it may be found that the distributed inductance
>and capacity of the vacuum tube electrodes and
their lead-in conductors Vare suchlthat a portion
of a standing wave representing a-substantial
n fraction of a wave-length may be set up within 20
the vacuum 4tube, leaving lonly a small part of
the Wave to ’be established in the conductors eX
vided by the inherent capacity between the plate
and cathode or a supplementary capacity may be
provided if necessary.
Other features of the invention are, first, the
use of a vacuum tube having its electrodes so dis
posed and connected that they form, vin effect,
continuations of the tuning lines and, second, the
extension of the tuning lines on both sides of
the electrodes. `By virtue of these features the
creation of voltage antinodes at the centers of
the electrodes becomes possible with a resulting
`substantial increase in the output power.
The nature of the invention will be more fully
understood from the detailed description which
follows and by reference to the accompanying
drawing of which:
Fig. 1 is a simplified schematic of the inven
Figs. 2 to 4, inclusive, areV diagrams illustra
>tive of the operation of the invention;
Fig. 5‘is a somewhat simplified showing «of a
preferred form of the invention; and
Figs. 6 and 7 illustrate mechanical and circuit
features of the oscillator of Fig. 5.
cillation frequency. Where tuning by Lecher 25 Referring to Fig. 1, III is a vacuum tube con
-ternal to the tube. This results in a restriction of
the range and accuracy of adjustment ofthe os
wires or adjustable concentric lines has been
used, a common practice has been to extend the
lengths of the lines sufliciently to include several
half waves at the oscillation frequency. This
has the advantages of permitting a wide range of 30
taining a straight ñlamentary cathode II, a con
trol grid I2, and an anode I3, disposed in par-_
allel relation to one another.
Lead-in wires ex
Itend from both ends of the filament and plate
through opposite sides of the tube to tuning‘con
ductors I4, I5, I6 and I1, which constitute the
frequency adjustment and, because of the inher
centralconductors of sections of coaxial line ele
ently low dissipation of the line structures, of
ments I8, I9, Z0 and 2|. Each line section is
ensuring a high degree of frequency stability.
provided with a sliding short-circuiting bridge
However, such arrangements tend to permit the
`establishment of >oscillations at the lower natural 35 such las 22, by .means of which its effective length
may be varied for tuning purposes. For the sake
frequencies ofthe extended lines, with the result
of simplicity the connections of the energizing
that oscillation at the desired harmonic modes ‘
sources for the cathode and plate have been
can be started and rmaintained only with difli
omitted from the showing of Fig. 1, but these are
40 shown in Fig. 5. As is usual in thecase of feed- y
In accordance with this invention the above
back oscillators, the plate is positive with respect
noted difficulty is avoided by employing the feed
to the filament and thegrid may beat the same
back method of oscillation generation using a
current potential as the filament or .may
triode vacuum tube and by tuning two of the
a negative bias. The control gridis con- .
interelectrode circuits by means of lines differing
in length by a predetermined fraction of a wave 45 nected directly to the outer conductors of the ~
tuning lines allfof which may be grounded.
length at the operating frequency. With this ar
rangement the phase or the magnitude, or both,
with the filament Il and grid I2 constitute a
of the feedback are such at the lower natural
single substantially uniform shielded line short
resonances of the lines that oscillations cannot
circuitedat both> ends. Likewise, line sections 20
be sustained. For the generation of the highest
and 2I together with the plate I3 and the grid
frequency oscillations we find it advantageous to
constitute Ia second substantially continuous
operate the vacuum tube with its control- grid at
short-circuited line. The two lines are shielded
ground potential and to connect the tuning lines
from each >other except for the. couplings pro
to the grid-cathode> and grid-plate circuits, re
spectively. .The feedback coupling may be pro 55 vided bythe direct capacity between the plate .
and filament of the tube, denoted by Cp in the
figure, and by the electron stream. The lines are
frequency, the lengths diñering from each other
They» are also acl
plate and filament when standing waves are pro
Y duced. With these adjustments rthe system oïscilá"
be such as to permit oscillationsin a lower fre
quency mode.
lates readily at the desired frequency-correspond-V ,v
Y -
çonstructional features of an oscillator
Y,‘embodying,the principles .of the y invention_ areV
ing to the half Wave diiTerence inthe »lengths _of
’ ,Y
tended further to include larger numbers of half
waves andïthat the difference in their lengths
ceuld be'inore than a single half wave, subject
to` the condition that the dilîerence should not
atively to theantinodes
of the
at the
of the» «
It will be evident that the lines might be ex
justed by positioning the short-circuited ends reln
the lines.
condition the
bridges can be kept well clear of the tube struc
ture so that the tuning adjustment is not re
adjusted '_so that each is an integral number of
half waves in length at the desired oscillation
by one or more half waves.
. „shown inlFigs. 5, ,6 and 7.
'I‘he oscillatormay be looked upon as a modi- '
lied form of the well-known C'olpitts oscillator, `
in which the oscillation circuit comprises essen
two capacities
and the plate
and cathode,the`-r
Referring tc Fig. 5,
`Ythe vacuum tube comprises a roughly hemispheri
' cal glass envelope 23 sealed to a iiat metallic
.base 2d. ' v'The grid l2 is mounted directly on
the base .2d and is electrically connected thereto. »
Leads from both ends of filament i! and plate
tively, and an inductance ,connected betweenrpthe
tirare brought out through vglass seals,v,such as
plate and the grid. One of the capacities is pro
vided'by the plate to cathode tube capacity/1Ds
and the other by detuning the cathode line lil, Vl 9
25, ineholes in the base'ëß, The four tuning
linesAV I3, le, 29 Yand 2lY haveA their outer conduc
' to-«a frequencyavery slightlybelcw` the _oscilla->
tion frequency so -thatits ._eiïective reactance, ~
tors connected directly to the vacuumtube b_ase
'Ell 'and -extend perpendicularly thereto, The
inner conductors Y*of the'li'nesconsist of small’Y
measured at Ythe tube electrodes, is capacitive.
diameter tubes such as 25, the o_uter surfaces of
Correspondingly, the, inductive characterof the »
which carry YtheÍhighÍ.'frequency' currents and -
plate to'grid impedance maybe realized by Vtuning
Vthe.' plateline 2,53, 2l to a frequency’very?slightly
greater than-the oscillation frequency. `Y`This. ex» . '
Yplanatio'nof Vthe, character of the. Circuit isV given
tentatively in Vthe absence Yof, more'vlexaot knowl-edge .of theactions> atltheextremely high, fl‘e?
„ '
through which insulated conductorsarethreadedV „
forsupplying the necessary energizing currents
to the’ plate" and fñlarnent.V ’These 'inner 'tubes
areY held Yin place insiderthe outer conductors by
ring" supports such as 2'! which may `be metallic.
At'their inner ends, the inner tubes arev provided
with ‘special condenser couplings te 'to ther/u1’-`
Some of the various standing waveY conditions -`- - rent supply conductors top-rovide low impedance
v that mayY existinthe tuninglines _of tlfieoscilla-r ` paths for the high frequency oscillations. ’These
are shown diagrammatically in'Fig.'5 and inde
tor with diiïerent adjustments of the short-,cir
ycuiting `bridges'are shown in Figs. 2, 3 andre. In
each of theseñgures the upper and lower hori
zontal lines represent,Y respectively,l the? central
conductors of the filament ,and plate tuning lines.
The curves, designatedby Vr 4and IVD, superim
posed thereon illustratethe _voltage distributions
along these lines. , The endsof the voltagecurves
correspond _to .the positions of the. short-circuit
ing bridges.VVA The Ashortest `possible vadjustment
ofthe linesis illustratedrbyeFig. 2,7,for whichcase
each line supports onlyisingle half wave. _ Be,
causeof` the. ìrreeularítiesßf the gemein’. Of
the" electrodeY structures the voltage' distributionV
' maybe. expected to diiîer from the simple sinus
o_idal Aform _characteristic of .a uniform line.
With this mode Vof operation the range of ad
justment is limited Yby the dimensions of the tube
and the highest frequenciesA cannot bel produced.
Fig. 3 illustrates one mode of operation in ac'
cordance withthe
on both sides
of the The
tail in Fig; 7. Adjustment of the eifective lengths
, of the linesV is obtained by meansrof sliding _
bridges such as 28 comprising metallic piston .
members drilled through the'center to' slide' over
the'inner tubes and provided with >a circular>
comb of nexible contact fingers which make cone
tact with both line conductors. Direct current
is supplied to 'the plate from a source through
the inner conductor ofA line 2Q. " The "other termi
nal of the plate` extends into the inner conductor
of’line 2l but is insulated therefrom bycondenser
coupling 30. Filament‘cu'rrent 'is supplied from
a sourceV 3l, grounded atits positive terminal,`
through >conductors threading the inner tubes of
lines I3 and lil and is controlled by a circuit in
cluding resistors 32 and 33, potentiometer 34, and
ballast lamp 35. These elements also serve to
provide a suitable Ynegative bias Yvoltage for the
grid, the amount of which may beV controlled by
the choice vof the values of resistors 32 and 33. >
‘An output circuit isindicated by a branching
concentric line 36 connected to line 2E) .close to
Ato accommodate three half waves and the y_fila
Qment line is4 extended on one side only so thatl ` the base of the tube. When this output circuit
it includes two half Waves.. VI'f the ñlament line
` wereY extended equally on the other side of the
connection is used the impedance ofthe con
nected circuit should be high and preferably
but, with the two linesv V'differing by one-half
should be so tuned as to prevent any substantial
effect on the standing wave pattern in the oscil
lator lines. Other well-known types of coupling ,
wave-"en_gth, oscillation is possible only at rthe
may also be used.
tube,_oscillation could take place at a greater
Wave-length as indicated, by the „dotted curves,
a higher> frequency.
` For the generation of the highest possible’fre
quencies it is desirable that each, of thel lines
shou1d__ include at _least three half >Waves', in ’
As already explained, the showing of Fig. 5 is
to some extent diagrammatic»Y Constructional
features of an actual oscillator are shown in Figs. `
5 and A'2. Fig. 6 shows a plan View of' the tube
base and electrodes, and Fig'. 7 vis a sectional
which case the dimensions of theV tube no ylonger
limit> Vthe .positioning of the `short-circuiting
' bridges.` Fig. ¿i illustrates the'stand'ingwavecon--
view showing the details of the line construction.
The 'tuning lines, instead Yof being disposed side
ditionswherí the filament line includes threeA
by side are placed'at the four corners-of a square
>half waves vand the plate line includes four.
as indicated by the four small circles in Fig. 6.
section and a diamond-shaped plan.
1. An oscillation generator comprising a vac
The vacuum tube plate I3 has a roof-like form in
uum tube having a cathode, an anode and a con
Th'e grid
trol grid, a tuning line connected to said anode
and said grid and a second tuning line connected
to said cathode and said grid, said lines being
short-circuited at their ends remote from the
vacuum tube electrodes and >having unequal
base plate provide supports for the tuning lines.
lengths differing by an integral number of h'alf
The lines fit over the supporting elements, good
wave-lengths at the oscillation frequency, and
contact and a firm hold being obtained by slit
ting the ends of the outer conductors axially. 10 said electrodes being connected to said lines at
points corresponding to voltage loops of the
Oth'er familiar methods of attachment may, of
standing waves developed in the lines at the os
course, be used. The tube terminals take the
cillation frequency.
form of straight rods coming out through the
2'. An oscillation generator in accordance with
centers of the line supporting tubes. Their con
nections to the inner conductors of ~the tuning 15 claim 1 in which the tuning lines are extended
has the sectional form of a U-shaped channel
and has a multiplicity of narrow transverse slits,
not shown, giving it a comb-like structure.
Short tubular elements 31 welded to the tube
on both sides of the vacuum tube electrodes suiii
ciently to include on each side at least one half
standing Wave in addition to th'e half wave cen
tered about the connection of the electrodes to
lines and the power supply leads are shown in
detail in Fig. '7. Plate supply lead38, passing
through the center of the inner conductor and
insulated therefrom by glass beads 39 terminates
in a tapered circular rod 40 which fits tightly in
the end of the inner conductor tube and is insu
lated therefrom by a layer of mica 4I. 'I'he end
,of the rod 40 projects beyond the inner conductor
tube and is drilled and slitted axially to receive
and make contact with plate terminal 42. The
layer of mica between the terminal rod and the
tube insulates the direct current supply circuit
and at the same time provides a capacitive cou
pling to the tubular conductor having very low
impedance at ultra-high frequencies. The con
nections to the other terminals of the tube are
made in the same way as described above.
For the adjustment of th'e short-circuiting
bridges 28, rods 43 are provided which are con
nected to the bridges and extend beyond the ends
of the tuning lines.
What is claimed is:
the lines.
3. An oscillation generator in accordance with
claim 1 in which the tuning lines are extended
_ o-n both sides of the vacuum tube electrodes and
in which the electrodes are connected to the line
extensions at the opposite ends of their major
axes whereby -the electrodes are included as por
tions of the line conductors.
4. An oscillation generator in accordance with
claim l in which the tuning lines comprise co
30 axial conductors, the cathode of the vacuum tube
being connected to the inner conductor of one of
said lines, the anode being connected to the inner
conductor of the other line, and the control grid
being connected to the outer conductors of both'
35 of said lines.
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