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Патент USA US2113340

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April 5, 1938.
2,113,340
J. EVANS
ULTRAHIGH FREQUENCY OSCILLATOR -
Filed Sept. 21, 1935
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John, Evans
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HT'I'OHNEY
Patented Apr. 5, 1938
2,113,340
UNITED STATES PATENT OFFICE
2,113,340
ULTRAHIGH FREQUENCY OSCILLATOR
John Evans, Collingswood, N. J., assignor to Radio
Corporation of America, a corporation of Del
aware
Application September 21, 1935, Serial No. 41,540
8 Claims. (01. 250-36)‘
My invention relates to ultrahigh frequency
thermionic devices. More particularly, my in
vention is an ultrahigh frequencyr oscillator em
ploying thermionic tubes in which the anodes are
a virtually at ground potential.
I am aware of numerous circuits for generating
high frequency oscillations. Some of the pro
posed circuits will generate ultrahigh frequencies
but the frequency is far from constant. Other
circuits have been devised which generate oscil
lations of high and constant frequency but it is
impossible to extend the range to frequencies ex
ceeding ?fty megacycles.
Beyond these high
frequencies the thermionic tube elements and the
15- leads within the tubes assume electrical lengths
of proportions which interfere with the higher
frequency ranges.
One of the objects of my invention is the gen
eration of oscillatory currents of ultrahigh fre
20 quencies.
Another object of my invention is to reduce
the effect of the anode load on the input circuits
of a thermionic tube.
A further object is to place the anodes of a
25 pair of push-pull oscillator tubes at virtually
ground potential.
Additional objects will appear in the following
speci?cation and claims.
Figure 1 is a schematic diagram of an ultra
30 high frequency oscillator in which the anodes are
at ground potential, and '
Figure 2 is a diagram of an oscillator embody
ing one form of my invention.
It is well known to those skilled in the art that
35 the characteristics of the input circuit of a 'triode
are dependent on the load in its output circuit.
Although this e?ect may not be of great im
portance at low frequencies, it is of extreme im
portance at high frequencies. By way of ex-~
40 ample, with one type of tube which has an input
capacity of about 28 micromicrofarads with a
zero plate circuit load, the effective input ca
pacity will be approximately three times as great
with an external load of 100,000 ohms. The out
45 put load may be inductive, capacitive or re
sistive and in each case the effective capacity or
reactance of the input circuit will be effected.
The input reactance may be e?ected in either a
positive or negative sense.
7
50
Although these effects are not always deleteri
ous, I have found that at ultrahigh frequences
the plate circuit load will limit the range of os
cillation and ultimately limit the highest oscil
latory frequency which can be reached. At fre
55
quencies of the order of. 50 megacycles and lower,
depending mainly on the tube construction, the
circuit of Figure 1 may be used.’
In Figure 1 a pair of triode tubes l-3 are con
nected in push-pull relation. The grids 5-—‘l are
connected to the conductors 9—ll of a trans 5
mission line l3. A bridging member I5 is ad
justed on the 'lines 9-H until a ‘quarter wave
length characteristic is obtained. The center I‘!
of the bridge is grounded through a grid leak
resistor Hi. The cathodes 2l-23 may be ener 10
gized by any suitable source; for example bat
teries 25-21 or alternating current. In prac
tice the capacity of the batteries or other source
of cathode heating energy must be considered.
Either ?lter networks or concentric lines should 15
be employed between the batteries and the cath
odes as will be described below. The batteries
25-21 in Fig. 1 are shown as directly connected
to the cathodes 2|, 23 merely for convenience of
illustration.
'
Conductors 29—3l of a second transmission
line 33 are connected to the cathodes 2 l-23. An
adjustable bridging member 35 is connected to
the transmission line at about a quarter wave
length position at which the tuned grid, tuned
cathode will cause oscillations.
The center 3‘! of
the cathode bridging member is grounded. The
anodes 39—4l are connected together with the
shortest.l possible leads. The center 43 of the leads
between anodes is connected to ground through
a suitable capacitor 45.
The center is also con
30
nected to a radio frequency choke coil 41. The
choke in turn is connected to the positive ter
minal of the anode current source 49. The nega
tive terminal of the anode current supply 49 is
grounded.
.
In the arrangement shown in Figure 1, if the
length of the leads between the anodes is very
short, the anodeswill be maintained at ground
potential for radio frequency currents because of
the low reactance of the capacitor 45 which vir
tually grounds the anodes. Under favorable cir
cumstances the anode output circuit will have
substantially zero impedance and the effective
input capacity will be relatively low and permit
the generation of oscillatory currents of a fre
quency of the order of 50 megacycles. However,
as the frequency is gradually increased, the
leads between the anodes, and particularly the
leads within the tube envelopes, will assume sub- 0
stantial eifective reactances; i. e., substantial elec
trical length. The higher the frequency the
greater will be the reactive component of the
leads, or the more effective their length. This
reactive component will act as a load on the out-:
2,113,340
put circuit and effect the characteristics of the
input circuit as explained above.
I propose to overcome this di?iculty by ar
ranging an output circuit which will have sub
stantially no effect on the oscillation frequency
and which will place the anodes at virtually
1. In an ultrahigh frequency oscillator of the
thermionic tube type in which the inductance
of the anode electrode lead has sufficient re
actance at said ultrahigh frequency to prevent
grounding the anode electrode within the tube, a
pair of thermionic tubes, each of said tubes in
ground potential at the highest frequencies. In cluding grid. cathode and anode electrodes, 2.
Figure 2 a diagram of‘ a circuit employing anodes ground connection, a grid circuit connected be
at virtual ground potential is shown._ A pairrof tween said grid- electrodes and said ground, a
cathode circuit connected between'said cathode
10 triode thermionic tubes 5 1-52 are connected‘ as a ' electrodes and said ground, means for tuning said
push-pull oscillator. The grids 53-55 are con
nected respectively to the conductors 5'l--59 of a 1’ grid and cathode circuits with reference to the
transmission line 6|. The line is adjustedto a frequency of; the oscillations to be produced, an
anode circuit connected to said anode electrodes,
quarter wave length by moving a bridging mem
ber 63 to the required position. The center 65 of means for grounding said anode circuit, and
the bridging member is connected to ground ‘ means for tuning said anode circuit to effectively
a half wave length of said ultrahigh frequency
through the grid leak resistor 61.
The cathodes 69--'H are each energized by oscillation wherebysaid grid and cathode cir
batteries 'l3—l5 or other suitable source. Radio cuits determine the oscillatory frequency of said
-'oscillator and said anode circuit establishes an
20 frequency choke coils ‘Ill, 12 are connected "in" ultrahigh frequency groundhpotential on said
each of the leadsbetween the batteries 13, 15 and
anode. electrodeswithin said envelope.
the cathodes 69-511. .. The batteries are each
2..In an, ultrahigh frequency oscillator of the
grounded.‘ v“Ag-pairof ‘capacitors 14 and 16 are
connected in series across. each of the cathode thermionic ,tube type in which the anode lead
offers a reactance at the frequency of operation 25
' __leads. The junction of. one pair of capacitors 14,
which prevents directly groundingthe anode elec
‘i4 is connected to one of the conductors ‘ll of a
transmission ,-line 8|; The junction of the other . trode within said tube, a pairof thermionic tubes,
pair of capacitors ‘I6, 16 is connected to the other
conductor“ of the transmission line. Although
I have shown the ?lter network between the bat
teries and the cathodes, .it is equally effective to
make the transmission line 8| a pair of hollow
conductors. One wire is connected within each
conductor from the battery to the cathode and
including, within. an evacuated envelope grid,
cathode and anode electrodes, arranged to oper
ate on opposite phases of ~ oscillatory currents; 30
a ground connection, a grid circuit connected be
tween said grid electrodes and'ground, a cathode
circuit connected between saidcathode electrodes
and ground, means for tuning said grid and cath
.», _,_the hollow conductors are used for the return . OdQ'CiI‘CUItS to said frequency of operation, means 35
wires from each cathode to the battery.
The
for impressing a positive direct current potential
with respect to said cathodes on said anodes, and
cathode leads are by-passed by» a suitableca
pacitor. In either type of connection, it is pref- . means for establishing, an ultrahigh frequency
erable to make the transmission» lines straight, ground potential on said anodes within said en
parallel and of equal length.
' ~ The proper length of the transmission line to
sustain oscillations is found by moving the bridg
ing member 83 whose center point 85 is grounded.
The anodes 8'l-—-89 are connected to the conduc
. tors 9l—93 of a transmission line 95. Across the
' end of the transmission line opposite the anodes
velope.
'
3. In an_ultrahigh frequency oscillator of the
type, in which the anode lead of a thermionic
tube offers sufficient reactance to the frequency
40
' of operation to prevent directly grounding, the
anode within said tube, a pair of thermionic tubes 45
including within an evacuated envelope grid,
is placed the bridging member 91. The center‘ 99 = ' cathode and anode, electrodes and arranged. to
of the bridging member 91 is grounded through
a capacitor l?l whose reactance is low to the
operate on opposite phases of their generated
currents, a ground connection, a grid circuit con
currents generatedgb-y the push-pull oscillator.
nected between said-grid electrodesand ground, 50
nected through'a radio frequency choke I03 to
If the bridging member 91 is carefully adjusted
so that the transmission line is effectively a half
wave length long, the anodes will be virtually at
electrodes and ground, means for tuning said grid
and cathode circuits to said-frequency of opera-,
tion,;means, for impressing -a positive direct cur
rent potential between said anode and cathode 65.
electrodes, and means: for establishing an ultra
high frequency ground potential within said en
velope on said anodes with respect to said ground
ground potential for the high‘frequency currents.
connections.
50. The center. 99 of the bridging member is also con- , a cathode circuit connected between said cathode
the positive terminal of the anode current sup
ply. N15.
The negative terminal of this supply
is grounded.
-.
,
The effect of the virtually grounded anodes is to
'
4.1m a push-pull ultrahigh frequency thermi 60.,
make the output load of the anode circuit sub- . onic oscillator of the type in which the anode
stantially zero and to remove the effects of this lead offers a reactance at the frequency of op
circuit on the input circuit. Using RCA type .852 eration which prevents directly grounding the
tubes in push-pull relation with tuned input and anode within said tube, a pair of thermionic tubes
. tuned cathode-circuits, I have been .able to gener
having inputfanode and cathode electrodes; a 65
ate oscillations of the order of 500 megacycles,
ground connection, a transmission line of sub
or. 60 centimeters wave length.
stantially one quarter wave length connected be
Various obvious modi?cations within the scope
tween said input electrodes and ground, a sec
of my invention will occur to those skilled in the
ond transmission line of substantially a quarter
art;
by
way
of
example,
the
grid
and
cathode
70
wave
length connected between said cathode elec-.
circuits may be tuned with lumped inductance
trodes and ground, and means .for maintaining
and capacity. I do not intend to limit myinven
tion except as required by the prior art and said anodes at points within said thermionic
tubes at ground potential with respect to said
the appended claims.
ground connection for ultrahigh» frequency cur 75.,
I claim: »
2,113,340
rents and at positive direct current potential with
respect to said cathode electrodes.
5. In a push-pull ultrahigh frequency thermi
onic oscillator of the type in which the anode lead
oii’ers a reactance at the frequency of operation
which prevents directly grounding the anode
Within said tube, a pair of thermionic tubes hav
ing grid, anode and cathode electrodes, a ground
connection, a transmission line of substantially
10 one quarter wave length connected between said
grid electrodes and said ground, a second trans
mission line of substantially a quarter wave length
connected between said cathode electrodes and
said ground, and a third transmission line of sub
15 stantially a half wave length connected to said
anode electrodes at one end and to ground at
the other end and tune whereby the ?rst men
tioned end of said third transmission line is sub
stantially at the potential of said ground connec
20 tion with respect to high frequency currents, and
a source of anode current supply, having a
grounded negative terminal and a positive ter
minal connected to the second mentioned end
of said third line.
6. In an ultrahigh frequency thermionic os
25
cillator of the type in which the anode lead offers
3
a reactance at the frequency of operation which
prevents directly grounding the anode within said
tube, a thermionic tube having an evacuated en
velope including grid, cathode and anode elec
trodes; a ground connection, a grid circuit con
nected between said grid electrodes and ground,
a cathode circuit connected between said cathode
electrodes and ground and an anode circuit con
nected between said anode electrodes and ground,
means for tuning said grid and cathode circuits to 10
generate oscillations at said operating frequency,
means for adjusting the effective electrical length
of said anode circuit to a half wave length at said
operating frequency whereby said anode elec
trode within said envelope will be at ground po 15
tential for said high frequency oscillations, a di
rect current supply and connections therefrom for
positively biasing said anode electrode with re
spect to- said cathode.
7. In a device of the character described in 20
claim 4, means for adjusting the effective length
of said transmission lines.
8. In a device of the character described in
claim 5, means for adjusting the effective length
of said transmission lines.
25
JOHN EVANS.
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