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Патент USA US2128837

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Aug. 30, 1938.
2,128,837
H. R. MEAHL
OSCILLATOR
Filed April 16, 1956
Inver‘rtor:
Harry RM}, ahl,
'13YL'J 76/44/15.
Hi Attorney.
2,128,837
Patented Aug. 30, 1938
UNITED STATES
PATENT OFFICE
2,128,837
OSCILLATOR
7
I
,
Harry R. Meahl, Scotia, N. Y., assignor to General
Electric Company, a corporation of New
.
. York
Application April 16, 1936, Serial No. 74,658
4 Claims. '
and a variable capacitor 1, is connectedbetween
oscillators and it has for one of its objects a
novel method and means for controlling the volt
age impressed on the crystal thereof.
anode 2 and cathode 3. Anode 2 is also con
nected to a suitable source of high potential (in
dicated as B) through the usual radio frequency
In high frequency apparatus of the type which
includes a crystal controlled oscillator, it is high
3
ly desirable and frequently necessary to provide
either some means for limiting the amount of
feed-back in the oscillating circuit or else to pro
'10 videsorne means for vlimiting the voltage im
pressed on the crystal. Excessive feed-back with
the resultant excessive voltage impressed on the
crystal of an oscillating circuit tends to create
wave disturbances, causes poor frequency sta-'
bility and often causes blocking of the oscillator.
When the oscillating circuit is designed to op
erate at extremely high frequencies, excessive
choke 8, the latter being employed to keep the
potential source free of radio frequency oscilla
tions. The usual blocking condenser 9 is con
nected in the anode return 'circuit to prevent
the high unidirectional voltage of the potential
source from being impressed on cathode 3. Con
trol electrode 4 is given a suitable bias by means
of the ?xed biasing. resistor H]. A transmission
line ii, having uniformly distributed inductance
and capacity, and being substantially a whole
number of half wave lengths long at the desired 15
operating frequency, is connected between con
trol electrode 4 and cathode 3, for reasons which
voltage on .the crystal frequently causes disin
will presently be explained.
tegration of the crystal because of the small
the so-called tuned-plate tuned-grid type in 20
crystal dimensions necessary for high frequency
O
(01. 250‘--36)
My invention relates to crystal’ controlled
The operating circuit thus far described is of
‘operation; These excessive voltages occur be
which the tuned circuit for the grid‘ or control
7cause-theMfeed-back through the electron dis
electrode is formed by transmission line II.
When transmission line H has a‘ length equal to
charge device of‘the oscillator increases as a
function of frequency. Various satisfactoryar
'25 rangements' have been provided for limiting
feed-back and the voltage impressed on the
crystal of an oscillating circuit where the cir
cuit has been designed for operation on so-called
“long” waves and for ordinary “short” Waves.
30
'
“
“
a whole number of half wave lengths at the op
erating frequency, a standing Wave ‘M is estab 25
lished thereon upon energization'of discharge
device I.
.In accordance with my invention a piezo elec
tric crystal I2 having suitable electrodes 13 is
0
No satisfactory arrangement has been provided, . connected across transmission line H at a point
somewhere between a nodal point ‘of potential
however, for controlling feed-back or for limit
ing the voltage impressed on the crystal of an and an anti-nodal point of potential of standing
oscillating circuit which is designed to operate at wave ill on transmission line H. By varying the
extremely high frequencies, such, for example, point at which piezo electric crystal I2 is con
nected to transmission line II with respect to
as above 6 megacycles. It is, therefore, an ob
ject of my invention to provide a novel means the standing wave established thereon, it is ap
for limiting the voltage impressed across the parentthat the voltage impressed on crystal i2
crystal of a crystal controlled oscillator of the may be varied from zero to the maximum volt
type which is designed to operate at extremely age of standing wave l4. Hence, a simple means
is provided for controlling the voltage which is
high frequencies.
a
impressed across the piezo electric crystal. '
The novel features-which I believe to be char
It should be understood that piezo electric
acteristic of my invention are set forth with
crystal l2 constitutes the dominant stabilizing
particularity in the appended claims. My inven
tion itself, however, both as to its organization means of the oscillator and that transmission
and method of operation, together with further line I l is used primarily for obtaining a standing
wave system to which crystal l2 may be selec
objects and advantages thereof, may best be un
derstood by reference to the following descrip-> tively connected. For this reason, transmission
tion taken in connection with the accompanying line i I may be much shorter than that necessary
drawing innwhich the single ?gure thereof illus
trates a crystal controlled oscillator constructed
in accordance with my invention.
when it is used as a frequency stabilizing means.
It has been found that a line substantially one 50
and one-half wave lengths long gives highly
satisfactory results when used in an oscillator
i an electron discharge devicehaving an anodev of the type illustrated in the drawing.
In order to hold the standing wave pattern
2, a cathode 3, and a control electrode 4. 'An
output impedance 5, comprising an inductance 6 constant it is sometimes desirable to connect a 55
Referring to the drawing, I have illustrated at
2
2,128,837
resistance H‘: such as an incandescent lamp across
way or the other along the line, a voltage is im
half wave lengths long at a desired operating
frequency, a piezo electric crystal, and means for
selectively connecting said crystal across said
line, thereby selectively to control the voltage im
pressed across resistor l5 and a short circuit is
pressed across said crystal.
transmission line H at a nodal point of potential.
Whenever standing wave I4 tends to shift one
placed across the line.
This tends to maintain
the nodal points of standing wave M at ?xed
points along line H.
2. A crystal controlled electron discharge os
cillator comprising an electron discharge device
having an anode, a cathode and a control elec
The operation of my device is as follows. The trode, a resonant transmission'line connected be
?lament of electron discharge device I is ener
tween said control electrode and said cathode, 1O
gized from a suitable source of potential (not ,said line being substantially a whole number of
shown) and the high potential source is connect
half wave lengths long at a desired operating fre
ed between anode 2 and cathode 3. By reason of
quency, an output impedance connected between
the feed-back from anode 2 to control electrode said anode and said cathode, and a piezo elec
4 in discharge device I, high frequency oscilla
tric crystal connected across said transmission
tions are established. Crystal I2 is moved along line at a point intermediate a nodal point of po
transmission line H until a point is reached tential and an anti-nodal point of potential of
where there is just su?icient voltage impressed
said line.
across its electrodes l3 to maintain oscillations.
3. In a crystal controlled oscillator, the com
bination with an electron discharge device hav
ing an anode, a cathode, and a control electrode,
of means for energizing said discharge device, an
oscillatory circuit connected. between said anode
and said cathode, a piezo electric crystal, means
comprising a transmission line connected between
said control electrode and cathode for producing
standing waves, and means to connect selectively
said crystal across said line at a point thereof of
suitable potential for excitation of said crystal.
4. In a crystal controlled oscillator,_the com 30
bination with an electron discharge device hav
ing' an anode, a cathode, and a control electrode,
of means for energizing said discharge device, an
It will be noticed that varying the position of
crystal l2 along transmission line ll does not in
any way vary the amount of feed-back in dis
charge device I. This, however, is unnecessary
since the voltage impressed across crystal |2 is
now limited to a value which will not cause any
of the disadvantages previously referred to.
While I have shown a particular embodiment
of my invention, it will of course be understood
that I do not wish to be limited thereto since
many modi?cations may be made both in the cir
cuit arrangement and in the instrumentalities
employed, and I therefore contemplate by the
appended claims to cover all such modi?cations
as fall within the true spirit and scope of my
invention.
What I claim as new and desire to secure by
Letters Patent of the United States is:
=1. In a tuned plate crystal controlled oscillator,
the combination of an electron discharge device
having an, anode, a cathode, and a control elec
trode, an output impedance connected between
said anode and said cathode, a source of poten~
tial connected between said anode and said cath
ode, a resonant transmission line connected be
tween said control electrode and said cathode,
said transmission line being a whole number of
'
oscillatory circuit connected between said anode
and said cathode, a piezo electric crystal, means
comprising a transmission line connected between
said control electrode and cathode for producing
standing waves, means to connect selectively said
crystal across said line at a point thereof of suit
able potential for excitation of said, crystal, and a 40
resistance connected across said- line on the op
posite side of said crystal from said discharge
device and at a nodal point of potential of said
line.
L
HARRY R. MEAHL.
45
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