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Патент USA US2411565

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Nov, 26, 1946.
2,411,565
T. L. WILSON
LOW IMPEDANCE OSCILLATOR
Filed July 20, 1942
INVENTOR
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- ATI‘ORNEY
_ 2,411,565‘
Patented Nov. 26, 1946
UNITED STATES PATENT" OFFICE
J., as
Thomas Lamont Wilson, Scotch Plains, N.Newark,
signor to Federal Telegraph Company,
’
N. J. , a corporation of California
Application July 20, 1942, Serial No. 451,596
3 Claims.
(01. 250-36)
1
two electron tubes, Ill and II, coupled to one
This invention, relatesto an electronic oscilla
another so as to constitute an electronic oscil-j
tor, the output‘ impedance of which‘is relatively
low.
'
lator. While these tubes have for the purpose
of simplicity in illustration been shown as tri
odes, it is to be understood that my invention
I
In many industrial ?elds, it is desirable to
couple the output of an electronic oscillator to
' is applicable to tubes having a larger number
a utilization circuit or load having a very low
of elements, such as tetrodes or pentodes and the
modi?cations of my invention necessary, to adapt
it for use with such last mentioned types of
impedance relative to the output impedance of
the conventional oscillator and to have the volt
age across this load impedance remain approxi
mately constant when the magnitude of the im
pedance changes over a wide range.
10 tubes, will be apparent to those skilled in the
The con
ventional electronic oscillator, having a relative;
‘ly high internal impedance will not provide a
art.
‘
The‘cathodes l2 and 13 of tubes [0 and II,
respectively, may be heated from any conven
ient source, as conventionally shown in the draw
ing by the symbols LT applied to the v leads
15
whose magnitude varies widely.
‘
.
proceeding from such cathodes. Likewise the
One object of my invention is to provide an
cathode of tube It is preferably grounded with
electronic oscillator‘ capable of feeding a load
respect to oscillatory currents by means of by
circuit having an impedance whose magnitude
constant voltage source for a load impedance
pass condensers Hl connected in series across
is-relatively low and varying, and of ‘keeping a
substantially constant voltage across that im 20 the’ extremities of the cathode and having a‘
pedance.
direct ground lead extending ‘from the conductor
between the two condensers, as indicated at l5.
At 56 is shown the control grid, and at I’! the
anode of tube It. The exciting energy sup
plied to grid I6 is derived in a manner which
25
cuit of an electronic tube, the excitation of the
will
be herein later described, but for the pur
tube being accomplished by feeding energy, in
poses of the present explanation, it is to be
the proper phase relationship, to an input cir
assumed that oscillatory electrical energy reaches
cuit constituted by the control grid and cathode
grid [6. Anode I1 is supplied with suitable high
of such tube. With electronic tubes of types 30 tension energy derived through conductor 18, as’
which are available in the art, the output im
indicated by the legend H'I‘+. This energy
pedance of a tube connected in the manner just
reaches the anode through a suitable impedance
described is relatively high and therefore the
such as inductance l9, connected in series there
external impedance which feeds the load, must
with. The ampli?ed oscillations appearing in
for the sake of efficiency and voltage regulation
In electronic oscillators as used‘ in the prior
art, the output has customarily been taken from
an impedance located directly in the anode cir
circuit of anode I‘! are transferred through
be made. quite high relative to the anode-cathode 35 the
the combined action of impedance [9 and cou
internal impedance of the tube, which latter value ' pling condenser 20, to the grid 2| of tube ll.
is high, relative to values prevailing in gener
This last mentioned grid is, with respect to
ators of the non-electronic type.
oscillatory energy, isolated from the ground by
In carrying out my“ invention, I make use
means of a suitable impedance such as induc
of electronic tubes of conventional-types‘, hav 40'
' tance 22 and resistance 23, connected in series
ing a comparatively great anode-cathode im
in the ground circuit of the grid. Likewise the
pedance, but I so connect the input and output
static potential of grid l6‘is determined by its
circuits, respectively, of such tubes that the im
connection to the ground through‘ a suitable
pedance of the external output circuit, to which 45. impedance
such as inductance 24 and resistance
the load is connected, shall be e?i‘ectively only
25, while the source of high tension supplying
a fractional part of the impedance existing when
energy to the conductor I8 has its negative ter
conventional methods of connection are em
minal connected to the ground, so that condenser
' ployed.
26 serves to by-pass oscillatory energy around
Another purpose of this invention is to pro
50
this source.
»
vide a generator of ‘electronic oscillations hav
' The anode 21 of tube II is connected directly.
ing an external output circuit of such low imped
ance as to possess an inherent quality of good
regulation, when connected to a load of rela
to a suitable source of high tension energy as
indicated at 28, which generally, but not neces
sarily is the same source as for anode ll of tube
tively low impedance.
ill. This source likewise has itsnegative ter-,
Referring now to the drawing,’ there are shown, 55
3
2,411,665
4
minal grounded as indicated at 29, while con
denser 30 serves to by-pass oscillatory energy
around this last mentioned source. The oscil
latory energy reaches cathode l3 of tube II
through condensers 31. Between the mid-con
nection point of condensers 3| and the ground,
is interposed a tank circuit comprising a con
ance l9 to increase, thus depressing the poten
tial reaching grid 2|.
The total voltage between grid 2| and cathode
I3 will be the grid-ground voltage less the cath
ode-ground voltage. By choice of suitable values
of the various impedances and capacities, as well
known in the art, phase shifts e?ects may be
denser 32, preferably variable, and aninductance
33 connected in shunt therewith. The constants
kept at a minimum.
.;
A reduction of voltage on grid 2| will lower the
10 voltage drop across the tank circuit and thus will
increase the net or effective anode-cathode volt
of this tank circuit serve to determine the fre
quency of the oscillations produced by my gen
erator; and such oscillations may lie either in
the audio frequency or in the radio frequency
spectrum, according to the choice of such con
stants. The exact point of grounding this tank 15
age. This brings about the result that the voltage
appearing from cathode to ground is in phase
with the grid-ground voltage. The voltage ap
pearing at point 36 will then be 180° out of phase
circuit may conveniently be determined by ad
with the grid voltage and thus, when fed through
justment of the point upon inductance 33 to
coupling condenser 31, will appear upon grid l6 of
which ground lead 35 is connected. The upper ‘ tube H1 in proper phase to sustain oscillation of
the system.
end 35 of the tank circuit-is connected tocathode
l3 via condensers 3i, while the lower end 36 of 20
Since the e?ective grid-cathode voltage of tube
this circuit is coupled back through condenser
l l depends on the relative grid-cathode and cath
31 to grid l6 of tube Ill. The tank circuit 32, 33
ode-ground impedances, if a load be coupled into‘
constitutes the output circuit of my generator
inductance 33, the cathode-ground impedance
and it may ‘conveniently be coupled to the load
will be lowered and the net grid-cathode voltage
by means of an inductance, 38 placed in juxta 25 will therefore be raised, assuming that the driver
position to inductance 33 although other methods
voltage supplied ‘to tube l I remains constant.
While this elfect of lowering the cathode-ground
of coupling to the load, as well known in the art,
may be employed.
impedance will usually be less at low frequencies
than at high frequencies, yet the effect is present
The way in which oscillatory energy reaches
under all conditions of oscillation. The cathode
the tube H is such as to cause the e?ective input
ground voltage supplied by tube II depends upon
circuit thereof to lie between the grid and the
anode, rather than between the grid and the 4 the oscillatory current in the anode circuit and
upon the cathode-ground impedance of this tube. ‘
cathode, since the input voltage appears across
If this output impedance be lowered, an increase
points 39 and 4B, the latter being at ground po
tential, while anode 21 is also at ground poten 35 in oscillatory current in the anode circuit, result
ing therefrom, will tend to keep the cathode
tial with respect to oscillatory energy, due to the
ground voltage constant. Thus it will be seen
action of by-pass condenser 30. The load circuit
that there results _a regulatory action similar to
thus becomes one of the type known as cathode
that obtained in the case of a generator having
follower, in that the load circuit is connected so
3
that not only the output energy in reaching the 40 low internal impedance.
Various modi?cations of this invention may be
cathode passes through such load circuit, but
made in order to adapt it to special uses. For
also the return between the grid and cathode
example tube 10 may be excited from an inde
takes place through this same load circuit.
In the operation of my invention, tube I0 func 45 pendent source, rather than receiving its excita
tion energy through feed-back condenser 31.
tions chie?y to amplify the oscillatory energy im
Optionally, it would be possible to substitute for
pressed upon the grid IS, the ampli?ed oscilla~
tube II a pair of tubes connected in push-pull
tions being passed on to grid 2| of tube II by
fashion. Other modi?cations of my invention
means of the impedance coupling circuit includ
ing impedances l9 and 22 and coupling capacity 50 will be apparent to those skilled‘in the art.
' WhatI claim is:
20. The action of this tube and its coupling cir
1.
A
low
impedance
oscillator
including
two
cuit will be apparent to those skilled in the art.
electronic tubes, having cathodes, control grids,
Tube H has the input energy impressed between
and anodes, means for supplying suitable energy’
grid 2i and anode 21, while the output thereof
is obtained between cathode l3 and a point of 55 to the respective cathodes and anodes, means for
keeping the respective control grids at a suitable
inductance 33 which is at ground potential.
mean potential, means for coupling the output
When a tube is connected in this fashion, its in
ternal output resistance, as ordinarily measured ' anode-cathode circuit of the ?rst tube to the in
put grid-anode circuit of the second tube, circuit
between anode and cathode, will be multiplied by
a fraction, the value of which depends upon the 60 means connecting the oscillatory energy of the
anode of the second tube to ground, output circuit
ampli?cation constant of the tube. Thus even a
means connected in the common‘ grid-cathode
tube having a very high IL may be employed as
and anode-cathode return circuit of the second
tube | I, notwithstanding the fact that such tubes,
tube, means for withdrawing oscillatory energy
as usually connected, have an extremely high out
from said output circuit means, and means for
put impedance.
'
65 feeding back to the control grid of the ?rst tube,
Tracing the path of one cycle of oscillation
in regenerative phase relationship, a portion of'
through the circuits of my invention, let it be
the energy present in said output circuit means.
assumed that grid I6 is driven positive above its
2. A low impedance oscillator including a ?rst
static potential. This will increase the anode
electron discharge tube having a grid-cathode
current of tube In and since the internal voltage 70
input and an anode-cathode output, a second
drop of the tube plus that of the voltage drop
electron discharge tube having a grid-anode in!
across impedance l9 will always add'together to
put and a cathode-ground output, means cou
equal the voltage supplied by the high tension
pling the output of the ?rst tube, to the input of»
source through conductor l8, this increase 'of an
second tube, means coupling the‘ oscillatory
ode current will'cause the voltage across‘ imped 75 the
energy of the anode of the second’ tube ‘to ground,
2,411,565
cathode-follower output meansof the second tube
including a parallel tuned circuit connected be
tween the cathode of the second tube and ground,
and regenerative means coupling the output of
said second tube to the input of said ?rst tube.
source of;anode energy, capacitative means by- _
passing said source directly to ground, a resonant
tank circuit connected between cathode and
ground including a series inductance and means
for grounding a predetermined point of said in
ductance, means for withdrawing energy from
3. A low impedance electronic oscillator in
cluding a ?rst tube having cathode, grid and
anode, a choke coil and resistance in series be
tween grid and ground to bias said grid, cathode 10
heating and grounding by-pass ‘means, a source
of anode energy, capacitive means by-passing
said source, a coupling impedance‘ in the anode
said tank circuit, means for feeding back a por
tion of said tank circuit energy to the grid of
said ?rst tube, and a capacity coupling the anode
of said ?rst tube and the grid of said second tube, '
cathode circuit, a second tube having cathode,
oscillatory system.
grid and anode, a choke coil and resistance in
series between the grid andground to bias said 15
grid, cathode-heating and by-passing means, a
whereby said fed-‘back energy is in regenerative
phase relationship and whereby said ?rst tube
excites said second tube so as to produce a self
THOMAS LAMONT WILSON.
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