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Патент USA US2406850

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Filed April 11, 1941
FIG. /
I’ '
one, 22, of which the portion l1 of the beam
forming electrode is ?tted and to the other, 23,
of which there are secured rigid, small diameter
wires 24 a?ixed to the cathode shell M. The
cylindrical portion l9 of the accelerating anode
is provided with a flange 25 extending between
a pair of insulating washers 26, the anode being
beam by the beam forming electrode I1, l8 and
includes a central cylindrical portion 32 integral
self-excited and operates to generate oscillations,
are accelerated toward the gap between the grid
portions 34 and 31 of the electrodes 30 and 3|,
respectively, due to the positive potential of the
accelerating anode l9. In passing across the
gap between the grid portions 34 and 31, the
electrons receive a velocity variation and the
velocity varied electron stream then passes into
secured to the foundation member 2| by an an
the space between the electrodes 3| and 38,
nular clamping bracket 21 a?lxed to the mem
wherein a bunching of the electrons occurs and
ber 2|.
the velocity variations are converted into density
The electron gun, it will be noted, constitutes
variations. Because of the negative potential
a unitary assembly which is supported from the
upon the re?ecting electrode 38, the bunched
stem H by a plurality of rigid wires 28 embedded
electrons are reversed in direction and again
in the stem, and to which wires the foundation
cross the gap between the grid portions 34 and
member 2| ‘is attached by rigid tie wires 29.
31 of the electrodes 30 and 3 |, respectively, trav
Mounted opposite the electron gun and co
eling toward the cathode, and deliver energy to
axial therewith are a pair of electrodes, desig
the resonant cavity. The device, therefore, is
nated generally as 30 and 3|, one, 30, of which
with an annular disc 33 extending through the 20 which are of extremely low wave-lengths, for
example, of the order of a few centimeters, de
wall of the enclosing vessel l0 and hermetically
pending upon the electrical parameters of the
sealed thereto, and includes also a dished reticu
lated or grid end portion 34. The other elec
The electrode 38 is so spaced with respect to
trode, 3|, includes a central cylindrical portion
35 integral with an annular disc 36 extending 25 the gap and is operated at such potential that
the drift time, that is the total time an electron
through and hermetically sealed to the wall of the
in the stream is in the space between the elec
enclosing vessel I0, and includes also a dished
trodes 3| and 38, considering both its motion
reticulated or grid end portion 31 conforming to
from the gap toward the reflector electrode and
and immediately adjacent the grid portion 34 of
30 in the reverse direction, is substantially equal
the electrode 30.
to (n—%) cycles of the operating frequency, n
A dished circular re?ecting electrode 38 is
an integer, so that the returning electrons
mounted opposite the electrode 3| and coaxial
cross the gap in the proper phase to deliver en
therewith and is supported from the stem l2 by a
ergy to the resonant cavity. In practice, the res
leading-in conductor 39.
onant cavity is tuned to the desired operating
Associated with the electrodes 30 and 3| and
frequency, by adjusting the position of the plung
coaxial therewith are a pair of coaxial cylindrical
er 43, and the voltage upon the electrode 38 is
conductors 40 and 4| which are joined at one
then varied until the power output derived from
end by an annular metallic spacer 42 and are
the output loop 48 is a maximum.
slidably engaged intermediate their ends. by an
The propriety of the requirement that the drift
annular conductor 43 or plunger the position of 40
time for the condition of sustained oscillations
which may be adjusted by a drive screw 44 se
shall be equal to (n—%) cycles of the operating
cured thereto and threaded to the metallic spacer
frequency may readily be veri?ed by considering
42. The inner coaxial conductor 40 engages and
the history of electrons crossing the gap at var
may be secured to the annular disc portion 36 of
the electrode 3|. The outer coaxial conductor 4| 45 ious phases of the electric ?eld in the resonant
cavity. For convenience, consider an electron
is connected to the annular disc portion 33 of the
(which will be referred to as the reference elec
electrode 30, as by way of metallic annuli 45
tron) that crosses the gap at the instant when
clamped to this disc portion and against the con
the electric ?eld is changing from the direction
ductor 4| by clamping members 46 and 41
produces electron acceleration to the direc
threaded to each other.
tion which decelerates an electron. The speed
The electrodes 30 and 3| together with the co
of the reference electron is substantially the same
axial conductors 40 and 4| de?ne a resonant
upon leaving as upon entering the gap. The elec
tron will travel a certain distance, d say, toward
by adjusting the position of the plunger 43.
Power may be taken from the cavity through a 65 the re?ector before being halted and will reach
the gap again after traveling a total distance
conductor 48 having a looped inner end as shown
equal to 2d. Such electrons as may have crossed
and extending through a cylindrical conductor
the gap shortly ahead of the reference electron
49 carried by the clamping member 41.
cavity which may be tuned to a desired frequency
had their speed increased by the action of the
During operation of the device, the accelerat
ing anode I9 is maintained at a positive poten 60 electric ?eld in the gap and hence penetrated
further into the re?ecting ?eld than does the
tial with respect to the cathode and the re?ecting
reference electron. Traveling a distance equal
electrode 38 is maintained at a negative poten
to more than 2d, the speedier electrons will tend
tial with respect to the cathode. The electrodes
to return to the gap at substantially the same
30 and 3| are maintained at the same positive
instant as the reference electron. Similarly, such
potential with respect to the cathode. In one
electrons as may cross the gap shortly after the
particular embodiment, operable in the 10 centi
reference electron will be slowed down, will pene
meter wave-length range, the accelerating anode
trate a smaller distance into the re?ecting field,
I9 may be operated at the order of 330 volts pos
and, traveling a total distance equal to less than
itive, the electrodes 30 and 3| may be operated
at the order of 250 volts positive, and the re 70 201, will tend to return to the gap at substantially
the same instant as those that started earlier.
?eeting electrode 38 may be operated between
Thus it will be seen that the reference electron
80 to 100 volts negative or between 22 to 32
volts negative, all with respect to the cathode.
The electrons emanating from the cathode l4,
I5 are maintained in a substantially parallel
may be regarded as the center of an electron
group. In order that the group may contribute
energy to the electric ?eld to offset the natural
damping- in- the.- resonator, the ‘ group should: return
to the gap at .an‘instant “when the~electric ?eld
is opposed to the motion. of the electrons inthe
group and is of ‘maximum intensity.
Such 'an
instant occurs substantially three-quarters of a ,
. change > in ,the :output ; obtainable. from the- device,
so that ;"the .‘device ais-suitable ‘ for use’ ‘for fre
quency modulation jpurposes.
For -‘ example, if
the devi‘cefwerequsedfor frequency modulation,
, an element would-be inserted in the-connection
cycle after the reference electron above described
..betweenthe;_ electrode 38’and the potential source
?rst crossed the gap and this and other such
itherefor, for varying the potential of the elec
instants occur at the times determined‘ by the
trode 38 ‘in accordance ‘with the signal 'to be
value of (n——1/4) cycles of the operating frequency.
modulated. ‘ As a speci?c illustration, such ele
Some of the electrons traveling in the reverse
mentcould be'the secondary Winding of an out
direction, that is from the .space between the
.put transformer theprimary winding of which
electrodesSl and '38 toward the gap between the
was‘in circuit with atransmitter or microphone.
grids ~34 and 3?, will be collected by the elec
Inasmuch'as the frequency of oscillation is'con
trodes 301and 3|. However, a large percentage
trollable by ‘the potential‘ of'the‘electrode 38, ‘the
of the returning electrons will cross the gap, 15. device disclosed is particularly suitable for use
deliver energy to the resonant cavity and pass
as'a beatingoscillator’with automatic tuning, in
through the grid 34, continuing thereafter toward
which case the electrode ‘38 vwould be appropriate
the‘electron gun t3. In the vicinity of or within
.ly; associated vwith an automatic tuning circuit
the gun, such electrons will again have their
effective'to maintain‘ the potential of the electrode
direction of‘moti'on reversed and be directed back
38 at thevalue requisite ‘for the generation of
across the gap.
These electrons thus again re
oscillations of the desired frequency to thereby
maintain-the correctlrelation between the beating
versedin direction of ‘motion have substantially
random velocities and also are debunched, so that
in again crossing the gap they deliver little energy
oscillator and‘signal frequencies.
High. frequencystability or, stated in another
way,v constant frequency ‘operation of the device
to the resonant cavity. Effectively they inter 25
mingle with and act similarly to the electrons
shown in ‘Fig. 1, maybe realized in one way il
‘emanating from the cathode of the electron gun.
lustratedin Fig. v3. ‘In the circuit illustrated‘in
It has been found that this re?ection effect and
this ?gure, the "oscillator device I0 is associated
double reversal of the direction of motion of the
' ‘with a “high‘Q circuit, such as “a ‘resonant cavity
electrons is augmented-by the form of the grid 30 de?ned by a cylindrical conductive member ‘ill the
vportionstllland 31 and of the electrode 38, that
frequency‘ of which “cavity maybe adjusted ac
is the dished form thereof, with the inner or
curately by a screw ‘H. Mounted adjacent one
concavesurface thereof toward the electron gun
Wall of the member 10 are a pair of identical recti
and that thus shaping these elements reduces
?erelements 12a ‘and 12b which are connected to
the magnitude of the current which must be :35 opposite ends of aresistance 13 in turn connected
drawn from the cathode to enable the attain
‘across the input terminals of a direct current
.mentof a particular output power. The dished
ampli?er 14, the mid-point of the resistance 13
form of the electrodes, furthermore, results in
being connected to the member 10.
uniform electron transit times in the region be
The resonant cavity of the device It is cou~
tween the electrodes?l and .38. I
$40 pled‘to the‘resonant cavity 10 by a coaxial ‘line
It’ will be noted that in one sense the device
shown and described is a velocity variation device
wherein a single resonant cavity isutilized for
15 having aloop end'l?a within the'cavity 10,
bothinputand output. The transit timesin the
space between ‘the gun and the electrode 30 is
.7 45
not critical. Furthermore, it will be appreciated
that the device is susceptible of simple operation
inasmuch as only one tuning adjustment and
one potential adjustment, that of the electrode
38, is necessary‘to effect variation of the oper
ating frequency over a fairly wide ‘range. For
example, in ‘the speci?c construction shown and
described, oscillations over the range of 8 to 13.4
centimeters have been obtained and, operating
with a second mode in the cavity, oscillations of .155
5 centimeters wave-length have been obtained.
With the resonant cavity tuned to a particular
frequency, the oscillator frequency maybevaried'
by 20 to 30 megacycles by varying the potential of
the electrode .38.
It'may be noted also that the coupling con
ductor '48 need not have any direct current con
nection to the cavity. Hence, the cavity need not
be grounded and the :device can be energized
from a supply having a negative ground, such,
' for example, as the‘supplyIfor an intermediate
frequency ampli?er. Also, it will be appreciated
that but relatively low voltages, in comparison
with the voltages employed in velocity variation
devices of known constructionare necessary upon
the electrodes of the device, this being due in
.part to'the grid portions 34 and ~37 utilized in
the electrodes 39 and 3|.
The frequency of oscillation can bevaried over
_a fairly wide range with but ‘little resultant 75
the line also connecting the ?rstementioned cav
ity-to—two loops ‘16a ‘and 16b in turn connected
.to the recti?er ‘elements ‘12a and "12b respec
In operation, ‘the accelerating anode I9 and
the electrodes ‘"30 ‘and f3! have ‘applied thereto
appropriate positive potentialspas by‘battery ‘H,
as described heretofore'in connection with Fig. 1,
and the- cavity- of the‘device 10 and the potential
of the electrode 38,=~supplied‘ by a battery ‘18, are
adjusted so that the device oscillates at the desired
frequency. The resonant cavity 10 also is ad
justed to this frequency.
When the discharge device [0 oscillates, energy
.is conveyed by the ‘line 15 to the two loops 16a
and 151). Also, electromotive fOrceS will be pro
.duced in these loops, opposite in phase as applied
tothe-recti?er elements 12a and 1219, due to the
currents induced in the cavity 10 by the loop
15a. -When the frequency of oscillations produced
inthedevice l?is thesame as that to which the
cavity 10 is tuned, the voltages produced at the
recti?ers 12a and‘TZb by the line 15 directly and
by the ~-loop 15a through the cavity 10 will be
equal and substantially equal recti?ed voltages
will ‘be produced by the recti?er elements.
Hence, substantially zero voltage exists across the
resistance 13 and no voltage change occurs at
the output terminals of the direct current ampli
?er 74.
However, ifthe frequency of oscillations gen
erated by the device [0 changes from ‘that to
which the cavity 10 is tuned, due for example to
temperature effects in the discharge deviceor
?uctuations in the voltages supplied to the elec
trodes thereof, the alternating current voltages
appearing across the recti?er elements 12a and
12b will be unequal and consequently the recti
ulated portions de?ning a gap, an electron gun
opposite one of said electrodes and in alignment
with said gap, and a re?ecting electrode oppo
site the other of said electrodes and in alignment
?ed voltages will no longer balance so that a di
rect current voltage will appear across the in
put of the ampli?er 14. Hence, an ampli?ed
with said gap, said reticulated portions being
dished in the direction away from said electron
2. Electron discharge apparatus in accordance
with claim 1 wherein the face of said reflecting
electrode toward said gap is dished in the direc
tion away from said electron gun.
3. Electron discharge apparatus in accordance
quency of oscillations generated by the device
with claim 1 wherein said electron gun includes
ill will be that to which the cavity 10 is tuned.
an accelerating electrode having a reticulated
In the electron discharge device illustrated in
Fig. 4, the enclosing vessel comprises a metallic 15 portion opposite said one electrode and dished
in the opposite direction to the reticulated por
cylinder 50 having an internal annular shoulder
direct current voltage will be impressed across
battery 18, in such direction as to change the
potential of the electrode 38 in the manner req
uisite to bring it to the value whereby the fre
portion 5|, and metallic annular end portions
52 and 53 having sealed thereto insulating mem
bers 54 and 55, respectively. Within the vessel
are mounted an electron gun l3 and electrodes
31!, 3| and 38 which may be of the same gen
tion of said one electrode.
4. Electron discharge apparatus comprising
a pair of coaxial electrodes having juxtaposed
grid portions de?ning a. gap, an electron gun op
posite one of said electrodes and coaxial there
with, and a reflecting electrode opposite the other
of said electrodes and in alignment with said gap,
said grid portions being concavo-convex and uni
eral construction as the corresponding elements
in the device shown in Fig. 1 and described here
inabove. The annular disc portion 33 of the elec
formly spaced with the concave surface thereof
trode 30 is seated against one end of the inter
toward said electron gun, and the surface of said
nal annular portion 5| of the enclosing vessel and
re?ecting electrode toward said other electrode
has bearing thereagainst a cylindrica1 metallic
being concave and uniformly spaced from the
spacer 56 against which there is seated in turn
grid portion of said other electrode.
the annular disc 36 of the electrode 3|. The
5. Electron discharge apparatus comprising an
electrodes 30 and 3| and the spacer 56 are ?t
enclosing vessel having a cylindrical metallic por
ted slidably within the cylinder 50 and may be
tion provided with an internal annular shoulder,
clamped in position by a cylindrical sleeve 51 ?t
an electrode having an annular portion seated on
ted within the metal cylinder 50.
shoulder and having a central electron per
In this construction, the resonant cavity is en
tirely within the enclosing vessel, being de?ned 35 meable portion, a second electrode having an
outer annular portion and a central electron per
by the electrodes 30 and 3|, the spacer 56 and
meable portion in juxtaposition to said ?rst elec
the portions of the cylinder 50 between the discs
tron permeable portion, a cylindrical metallic
33 and 36. Energy may be taken from the cav
spacer member engaging said annular portions
ity through the conductor 59 which extends,
of said electrodes and bounding therewith a res
through an eyelet 58 secured to the cylinder 5!]
onant cavity, an electron gun opposite one of said
and is hermetically sealed to the eyelet by a glass
electron permeable portions, an auxiliary elec
or other insulating bead. The cavity may be
trode opposite the other of said electron perme
tuned through a coaxial line 60 of adjustable ef
able portions, said annular portions and said
fective length in shunt with the cavity, the in
spacer member being slidably ?tted Within said
ner conductor of the coaxial line being con-‘
metallic portion of said vessel, and means secur
nected to the disc 33 and the outer conductor of
ing said portions and spacer member against said
the coaxial line contacting and being secured to
the metal cylinder 50.
6. Electron discharge apparatus in accordance
The device illustrated in Fig. 4 may be operated
in the same manner as the device shown in Figs; 50 with claim 5 comprising a variable coaxial line
coupled to said cavity.
1 and 2 as described heretofore.
'7. Electron discharge apparatus comprising an
enclosing vessel having a cylindrical metallic por
tion, a pair of electrodes within said vessel and
de?ning a resonant cavity with a section of said
metallic portion, said electrodes having inner re
ticulated portions in juxtaposition and de?ning
a gap and having also outer portions conduc
tively connected to said metallic portion, an elec
sulation in other constructions are avoided as are
also extraneous capacities of such insulators. 60 tron gun opposite one of said electrodes, and a
re?ecting electrode opposite the other of said
Also, it will be noted that this construction en
A particular feature of the construction illus
trated in Fig. 4 resides in the fact that the cav
ity does not include any joints so that power
losses due to contact resistance losses in such
joints or to radiation losses through gaps therein
are avoided. Furthermore, the cavity is free
from insulating material so that losses due to in
ables the very accurate alignment and spacing
of the electrodes so that the construction of de
electrodes, said reticulated portions being con
cavo-convex and having the concavo face thereof
toward said electron gun.
vices for operation at very high frequencies, at
8. Electron discharge apparatus in accordance
which accurate alignment and spacing of the 65
claim '7 wherein the surface of said re?ect
electrodes is very important, is facilitated.
ing electrode opposite said other electrode is co
Although speci?c embodiments of the inven
axial with and-curved in the same direction as
tion have been shown and described, it will be
reticulated portion of said other electrode.
understood that they are but illustrative and that
9. Electron discharge apparatus comprising a
various modi?cations may be made therein with 70
pair of electrodes having juxtaposed grid por
out departing from the scope and spirit of this
tions de?ning a gap, means cooperatively asso
invention as de?ned in the appended claims.
ciated with said electrodes de?ning a resonant
What is claimed is :
cavity therewith, an electron gun including a
1. Electron discharge apparatus comprising a
pair of spaced electrodes having juxtaposed retic 75 cathode opposite one of said grid portions, a re
?eeting electrode opposite the other of said grid
portions, said grid portions‘ being dished and
having the inner faces thereof toward said elec
tron gun, re?ecting electrode having a dished
surface facing the grid portion to which it is
opposite, means for maintaining said pair of elec
trodes at a positive potential with respect to said
cathode, and means for maintaining said re?ect
ing electrode at a high negative potential relative
to said cathode.
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