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Патент USA US2406309

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v Aug. 20, 1946.
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M. _ZIEGLER> ETAL
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2,406,309 '
FREQUENCY STABILIZATION
Filed Nov. 3, 1942
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45
MR6’ ZIEGLER
‘
,
M4NUFL JUHOKOBILSKX
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INVENTORS.
A 7' mRNEY
Patented Aug. 20, 1946
2,406,309
UNITED STATES PATENT'I‘OFFICE
FREQUENC€ZZTIZEIZATION
I
Marc Ziegler and Manuel Julio Kobilsky, Buenos
Aires, Argentina, assignors to Hartford National
Bank and Trust Company, Hartford, Conn., as
trustee
Application November 3, 1942, Serial No. 464,380 '
9 Claims. (01. 179-1715)
The present invention relates to frequency staé _
bilization and more p'articularly'to the‘stabiliza
tion at a desired value of the frequency of an
oscillator.
.,
‘
In connection with the problem of stabilizing
the frequency of an oscillator ‘at a desired value,
which is of great importance in radio technique,
several solutions have heretofore been proposed.
For instance, the use of very selective circuits
with great physical constancy, such as crystals,
spatial circuits and tuning forks, permits ofvthe
construction of oscillators the frequency of which
which is rigorouslyequal to that of the pilot.
The classical phasemeasuring methods are lim
ited however to phase differences smaller than
1r/2 which is a given limitation. The second
method gives rise merely to a reduction of the
frequency, though this reduction can generally
be as large as desired.
The ,‘present invention is more particularly’
concerned with the frequency reduction meth
ods of stabilization.
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r
>
The known systems of frequency control by
does not vary more than a small fraction of its
nominal predetermined value.
2
two oscillations andto a resultant frequency
frequency reduction utilize,~for obtaining the
controlling magnitude, the frequency responsive
'_
' The frequency of such an oscillator is, however,
properties of selective circuits. Hence the ab
solute stability obtainable cannot be better than
they absolute stability of the said discriminator
desired, from its original value. Only a phase
circuits, and this suggests the use, for the dis
shift can be forced on the oscillation obtained,
either by using the properties of electrical cir 20 criminator, of high quality circuits such as those
hereinbefore mentioned.’ While the use of such
cuits or by introducing a time-retarding device.
circuits is, of course, possible, it will not answer
By phase modulation a corresponding frequency
the requirements of linear response to frequency
modulation may be created at the output, but
variations over a relatively wide range, which
the frequency of the oscillator itself does ‘not, ,. must be satis?ed in, for instance, frequency mod
vary, and the mean frequency of the'output sig
ulation problems. If a wide frequency swing has
nal remains equal to it.
.
to
be discriminated linearly, only less selective
In many cases,'however, it is not desired to
circuits can be used, whereby the inherent insta
obtain merely a frequency of rigorously known,
bility thereof is introduced into the system. 7
value, but to have an oscillatorvwhich shall auto
matically adjust itself exactly at a frequency 30 Furthermore, the response of the common dis
criminator circuits, and, therefore, the result
which is known only-approximately and which
ing controlled frequency, depend either on the
may be varying in time. Again, it may be de
amplitude of the applied signal and on the value
sired to modulate directly the frequency of an
so well de?ned by the physical constants of the
circuits used that it cannot be shifted, even if -
oscillator by periodic variation of one of the cir
cuit
constants.
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All these cases necessarily require the use of
suitable oscillator arrangements the constants of
which may readily be modi?ed, so that the fre
quency may be changed as a function of a con
trolling magnitude.
The control of the circuit
may be either mechanical, as by means of vari
able condensers, moving cores and the like, or
of a compensating voltage, or on the-correct bal
ance of a symmetric detector arrangement, all
35 of which factors are possible causes of drift from
the exact adjustment.
The method of the present invention and the
[devices for the realization thereof while shav
ing the same basic idea as other frequency sta
bilizing arrangements, namely, to measure the
frequency diiference between the oscillation to be
stabilized or controlled and a pilot oscillation and
electrical, as by means of magnetic saturation,
to use the magnitude so obtained for automat
variation of dielectric constant with temperature,
ically reducing the frequency difference as much
reactance tubes and the like, and of these meth 45
as possible, utilizes, in contradistinction to the
ods, the purely electrical one involving reactance
prior art, a compensated frequency meter the
tubes is the most generally used nowadays.
outputof which is zero for a predetermined fre
The controlling magnitude may be obtained in
quency independently of the battery tension ap
one of two general ways, namely, either by oper
ating on the basis of the phase difference be 50 'By'frequency meter is- meant herein a fre
tween the oscillation to be controlled and a pilot
quency responsive device ‘commonly known as
oscillation, or by obtaining it from a frequency
plied.
responsive device which measures’ the frequency
difference between said oscillations. "I
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such, whichincludes only resistances/and capacie
ties.“ Accordinglythe present invention dispenses "
‘
The ?rst way leads to a synchronization of the 55 with the use of a symmetric discriminator design
comprising selective inductance and capacity cir
aeoasoe
cuits'and with the use of a stabilized compensate
ing tension.
~
' .meter I6 which produces an output proportional
'
to said frequency difference.
7
Preferably the mixer 12 includes a convenient
output ?lter from which the signal of frequency
difference resulting from the mixing of the os
Since frequency‘ In ters have already been'dis
cussed in detail elsewhere (see Frequenziometri
' electronici a d-esviazione,cAlta Frequenza, F. Vec
cillator and pilot outputs is obtained.
chiacchi, May 1937) it is deemed su?icient for
the understanding of the present invention, to
recall that the output current is provided by a
number of condenser discharges which is equal,
during anytime, to the number of positive phases »
7
It will be clear to those skilled-in the art that,
with the, above arrangement any deviation from
the desired frequency, due to variation in the
constants of the oscillator Ill, as for example a
change of capacity with temperature, cannot take
place without causing an opposite effect propor
tional to the frequency change really taking place
‘; as the result of both effects. Analogously, with
of the signal applied to the apparatus.
If the RC time of the condenser ClI‘Cllll'! is suf
?ciently small compared withthe period'ofthe.
highest frequency to be measured, the condenser .
. the ‘well-known .theory of negative feed-back, it
can be shown that the frequency drift of the os
:'is each time charged tothe sameepotential and
discharged completely, so that the discharges are
cillator when connected to the correcting link is
equal and'the mean value of the; current, talgen; 7 * approximately A times smaller than the frequency
over some time including a su?iciently'largenum
ber of periods, is proportional to the number-0f
drift
without such
link.to A
acenstant
the arrangement
equal
thebeing
product
of the senof
periods and hence to-the frequency. Moreover,
sitivity lc-of the frequency‘ meter it in voltsper ‘
if the amplitude of the signalapplied- does vnot
kcJand' the in?uenced ‘ofthereactance tube 22'
in?uence the loading voltage, the output is in-' _ in kc. per volt. '
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dependent of this. amplitude. It can also be
Since for successful; operation of" the: novel
'> shown that, if the frequency of the signal varies, 25 method of frequency stabilization the output of
the output reproduces the variation correctly so ‘ the" frequency meter must be properly compen
’ long‘ as the variation. is‘ slow as compared with
sated at all’ times, variations of the elements of
the longest period of the frequencies passed dur- ,
this'mp’art of a practical arrangement would be
ing therexcursion, and that, even if the frequency
considered as meriting attention, and indeed, in
modulation has a period of the same order as or 30 vestig'a'tion of this 'point'has led to certain valuae
even smaller than said longest period, the aver- _ ,
ble features of the present invention," as will now
agegvaluelof the output current, taken over a
long time, will still be proportional to the central
bemadeclear.
frequency.
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It can be‘shown that the influence of relative
variations da/a and die/k of the constants hand
70 can be made practically negligible, as it is equal
to their product with the" frequency "difference
divided by the factor 'A=alc, which can be made
.
These general properties of the frequency me
terrwill be utilized in accordance with the present
invention for obtaining an improved method and
means for frequency stabilization and for ob
taining other derivative advantages arising out
of the application of'the said improved method
large in practice.
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The influence of undesired variations inithe
compensating voltage'Vb, when taken’ separately
and means in particular problems, as will here
is, though by no means exaggerated,inot at, all
inafter be more particularly explained. -
negligible, but the present invention provides’
In the drawing,
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means for compensating this effect. As said'be-f
i
fore,'the output current of the frequency'meter
Fig. l is a block diagram illustrating the meth
od of- frequency stabilization of the present in—'
vention, and
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_ is prdvided
a number of condenser discharges
' equal to the number of periods of the frequency
applied. The output tension obtained is there?
.
VFig. 2' is a diagram illustrating a frequency
modulated transmitter embodying frequency sta
bilization according to the present invention.
' As already stated, the basic idea underlying the
- present method is to measure the frequency dif
' ference between the oscillation to be stabilized
fore proportional’ to the frequency, to. the ca
pacity of the condenser,v to the’voltage-yup to
59. whichthe condenser has been charged and to
and the oscillation of apilot, and it is therefore
obvious that‘ the frequency difference which is
to be the direct cause of the controlling action
to be applied to the oscillator, must be Within the
working range, an univocal function of the os
cillator frequency.
the resistance through which the current is now;
If now the compensating voltage is obtained,
ing,
H
.
by means of a potentiometer, from the‘ same bat: '
tery, which provides the tension for loading up,’
5.5.; the
condenser, a change of battery tension will
not affect the», frequency for which the, compen- '
. sated output tension ofthe frequency meter is
.
Since,,physically, the difference frequency'can ‘
zero.
,
,
never have attributed to it a negative sign, it 6,0v Such anarr'angement is shown inthe portion
of Fig. 2 marked off with chain} lines in which a
will be clear that the oscillator frequency will al
battery '13 provides the operating tension for the.
ways have to be either higher or lower than the
frequency meter main tube 245, and the compen
pilot frequency. Hence, the oscillator frequency
sating tension x13 is taken off a potentiometer
mustbe stabilized at. a frequency differing a pre
determined amountfrom the pilot frequency, and
65
this constitutes a particular feature of the pres
ent invention. The amount of. difference is so
chosen that the oscillator frequency will never
with an output ?ltercomprising resistances 28
and .36 and condensers 32 and 34-.
pass the pilot frequency, taking into-account all'
possible factors, including the possibility offree
quency modulation.
The difference‘ frequency, obtained as‘ shown
in Fig. l, by applying the frequency of‘an ‘os
23 across said battery 3. The frequency meter,
as shown, likewise comprises a condenser C and
an outputresistance r, and is preferably provided
70
o
In the operation of the frequency meter the,
oscillations present in the outputvof the ‘mixer
stage lZa are applied to, the grid of the ,valve'2_§;.¢.
During those half periods of the oscillationiori
which the gridris»positive'with ,r?specttothe
cillator'iil to a mixer l2 simultaneously with the
output of a pilot i4, is applied to a frequencyv , cathode-of- the valve. the-latter willbeconductive,
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2,406,309
6
and practicallythevfull voltage of battery B will
justablev frequency having all the stability ofin-i
herently non-variable oscillators, suchas quartz
be applied to capacitor C through load resistor
r and diode I00. During the other half periods
of the oscillation, when the grid of valve 24 is
negative with respect to the cathode, capacitor
C will be discharged through diode Illl, resistor
q and the external ‘circuit including battery B,
anoderesistor I04 and potentiometer 26.
Resistors I02 and H13, included in the grid cir
cult, of valve 24, are designed to transform the
oscillation generated in the output circuit of the
mixer stage [2a into a square wave. Across re
sistor 1' there is generated a discharge impulse of
capacitor 0 every time the control grid‘ of the
valve 24 is positive with respect to the cathode of
this valve, so that for each period of the oscilla
tion applied to valve 24, an electrical impulse is
obtained in such a form vthat the mean value of
the tension developed across resistor r is propor
tional to the frequency of the oscillation» applied
to the control grid of valve 24. The tension so
developed across the resistor r ‘is compensated
to zero for a given value of the frequency of the
oscillation applied to the grid of valve 24 by
means of the compensating tension AB so that
oscillators and the like.‘ The desired frequency
can be changed, by choosing, for exampleanother
position of the potentiometer which determines
the fractional compensating voltage. The po
tentiometer,v which may be of the continuously or
step—by-step variable type, may be calibrated in
Y
kilocycles for adjustment. ‘ Alternativelythe out
put resistance or the .capacitymay be made 31d?
justable, and in the latter event, the condenser
of the frequency meter would be made variable or
comprise a variable portion, as indicated by the
varrowin broken lines in Fig. 2.
V
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' I .,
In the foregoing discussion the arrangement
and method have been considered for the case of
a
non-modulated \ oscillator .7 to
be
stabilized
around a frequencydiifering a ?xed amount from
that ‘of a non-modulated pilot. It is obvious
that, since the response of the frequency meter
does not, within a very large range, depend on the
amplitude of the signal applied, either the oscil
lator to be stabilized or the pilot oscillator or
both may be amplitude modulated, so long as the
tive values in proportion to the sense and amount
amplitude of the signal applied during the most
pronounced amplitude minima, does not fall be
of deviation of the frequency'of the oscillation
from the ‘given value.
If one Or both of the oscillators is frequency
the resulting voltage assumes positive and nega
‘
modulated, stabilization is also possible, provided
The low pass ?lter following resistor r and con
stituted by resistorsl28 and 30 and condensers 32
and 34 is adapted to suppress the alternating
components in the mean voltage developed across
the resistor r.
It can be deduced easily, that
low the lower admissible limit.
such an ar- .
rangement, if a’r’CB>>l, this product having
the same signi?cance as the factor A=ak above
mentioned, that the input frequency of thexfre
quency meter forwhich the compensated out
put is zero, that is just the desired frequency dif
ference between the pilot and the oscillator to be
stabilized, is approximately equal to A/rC.
, It follows from this that said desired frequency
can be adjusted to a predetermined value by
that care is takenv that the predetermined fre
quency difference is su?iciently greater than the
sum of the maximum excursions of the oscillators
for the reasons hereinabove set forth‘.
If care is taken to make the response charac
teristic of the frequency meter linear between 0
and twice the'desired frequency," and a suitable
band pass ?lter, designed to‘cut out all frequencies
above SGc/s, is placed between the output of the
frequency meter and the input of the reactance
tubeasindicated at 28 to 54 in Fig.2",the theoe
retical results obtained can be applied without
change to the‘ central frequencies of the free
» quency modulated signals considered.
The frequency stabilization method of the
varying either the potentiometer relation A, the
output resistance or the capacity of the frequency
meter, which is a very interesting feature.
present. invention may also be applied to‘ fre
factors, moreover, can each be made adjustable ’
ment of such application is shown in Fig. 2.
quency modulated transmission, and an embodi
with all the precision required and may ‘present
Here the transmitteriantenna 36 is connected
a high degree of constancy.
through a'power output section 38, a driver or
doubler 40 and a separator 42 to an oscillator
l0a, which is connected to the mixer |2a of the
For this reason, and ,
because the frequency applied to the frequency
meter (difference frequency)~ by which the rela-> ,
tive variations of said factors are multiplied, may ‘
be of the order of only kc. or tenths of kc., a
high degree of stability of the oscillator fre
quency when compared with the pilot‘ frequency
may be expected, even when working at frequen-‘
cies as large as mc./s.
frequency meter ‘unit already described, and to.
a reactance tube 2211, which in the present in
stance acts both as stabilizer. and. as modulator.
The output of the frequency meter unit, after.
pass ?lter 28 to 34, is
,
It may further be observed that variations of
the proper frequency of the oscillator from the
source of intelligence,
60 such as a microphone (not shown).
Thus while
the frequency meter arrangement maintains the
central. frequency constant, the output of the
I
oscillator is also'frequency modulated by super-' '
output makes it possible and easy to readjust,
during operation, the proper frequency of the os-,
cillator to the correct value, when it appears that
over a long-time, the frequency shift tends to in
imposition of the intelligence factor derived from
said secondary 44.
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Those skilled in the art Will appreciate from
the foregoing description that the novel method
and means for frequency stabilization of the
invention
The above-mentioned relationship between the 70 present
advantages
of great
desired frequency and the fractional compensat
crease to an inadmissible value.
ing voltage,
ity of the frequency meter, provides a very con
2,406,309
@7
quantity substantially proportional to the‘. fre
merit does :not require more than .-a single quartz ' ' quency of saidjo'scilllation and to :said voltage,
; oscillator. Again, itis possible vto ‘make ‘the sta
and ‘simultaneously inje'c‘ting a fraction of said
frequency vdepend prac
or, the quartz 0's.
1 ‘bility. of . the central
. tically only :upon the stability
cillator used. In general,"the complete stabiliz- I,
ingarrangement does n ot require more ‘than a
3 single adjustment .in'orderto adapt it to work at
‘and a change of the value
‘ the desired frequency,
of only one element makes it. possible ‘to ‘stabilize
voltage in opposition to said quarrt'ity'to produce 7
an output quantity which is compensated ‘to ‘zero
independently of variations in said source at a
frequency value jof‘the oscillation equal to ‘the
said predetermined ‘mean frequency value and
the polarity and value of‘whi'ch areproportional
to‘the deviations of said electrical'oscillation from
* the oscillator around different well-de?ned fre-' .10. the predetermined frequency value.
'
> quencies, a feature which ‘may ‘have many "appli
3. A compensated frequency ‘discriminator for
'1 , cations in radio communication. The number "of f vdetecting frequency deviations of an electrical
tubesand parts is relatively small and there‘ is i » oscillation varying about apredetermin'ed mean
nothing very critical "n' their assembly. More; .‘1-5. frequency, comprising a‘ ‘circuit containing a
over, critical elements, such as a tube or a source
of tension, may, as 'can'be shown, have variations
as‘large 'as 10% without affectingythe validity of
the results. . Finally, it should be noted ‘that ‘the ‘
stabilizing arrangement does .notxuse any tuned
source of direct current “and a resistance, "means
for interrupting the current in said circuit ‘in syn
chronism'jwith ‘half-waves‘ of like sign of'said
oscillation to obtain voltage ipul'sationsfa'cros’ssa'id
resistance, means for transforming said Voltage
circuits. Hence it can be utilized at any "fre
quency, and vmay be assembled and marketed as
a universal frequency modulation and stabiliza
pulsations into electrical impulses of like sign
having an area substantially’proportional to the
voltage ‘of said source, an amplitude independent
of said oscillation and a duration smaller than the
tion unit. Inclusion of the quartz pilot and of‘
the oscillator gives a frequency modulation trans
mitting unit adapted to be directly connected to‘
half-periods of the highest frequencylto be dee
tected, means to integrate said impulses to ob
tain a potential substantially proportional to the
a frequency modulation transmitter. '
Although the present invention has herein
above been described with reference to certain
preferredembodiments, We do not wish to be lim
frequency of said oscillation and to the voltage of
to connect a fraction of
said
voltage
in
opposition
to said pote'ntial'to pro
ited thereto as obvious modi?cations will occur 30 duce an output potential which is compensated
' said source, and means
to those skilled in the art without departing from
‘ ' the spirit and scope of the invention.
We claim:
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V 1. The method of detecting frequency deviae
to zero independently of voltage variations in said
direct current source at frequency values of the
oscillation equal to the said predetermined mean
frequency value and the polarity and value of,
oscillation about a prede~ 35 which
‘are prcportionalto the deviations of said
7 tions of'an electrical
termined frequency value by means of a circuit‘
arrangement comprising a direct current source
_
means responsive to
7 and current interrupting
electrical oscillation from the predetermined fre
qu ency value.
'
I
Li. A ‘compensated frequency discriminator for
said electrical oscillation connected in series with ' detecting frequency deviations of an, electrical os
said source, comprising thesteps of generating 40
electrical impulses for each period of vsaid os
cillation having an area substantially propor
" tional to the ‘voltage of said source and a ‘dura
cillation varying about a predetermined mean fre
quency, comprisingv a thermionic tube having ‘a
control electrode, an anode and a cathode, a re
sistance and a direct current source‘ serially con
nected between theanode and cathode,'means
tion smaller than the periods of the-highest fre
quency'to be detected, integrating said'impulses‘ ‘ , tov apply said oscillation to said control electrode
to obtain an electrical quantity substantially pro
to produce voltage pulsations across said resist
portional to the frequency of said oscillation and ‘ ance in synchronism with half-waves of like sign
to said voltage, and simultaneously injecting ‘an
of said oscillation, means to transform saidL volt- ,
other electrical quantity derived from said source . ' agepulsations into electrical impulses of like sign
in, opposition to said first quantity to produce .
an output quantity which is compensated to zero
independently of variations of said voltage at 'a
frequency value of the‘ oscillation equal tort'he
said predetermined frequency ‘value and the
polarity and value of which are proportional.
to the ‘deviation of- said electrical .oscillation
fromthe predetermined frequency ‘value.
2. The methodvof detecting frequencyrdevia- I '
having an. area substantially proportional to the
voltage of said source, an' amplitudeindependeht
of said oscillation and a duration smaller than
the-half-peri-ods of the highest frequencyto be
7
having one elec
' detected comprising a condenser
trode coupled to the anode circuit of said tube,
two half wave recti?ers having anode and cath
' ode electrodes, and a load
resistance, the cathode
of one of said recti?ers and the anode of the other
tions of-an electrical oscillation varying about, a
rectifier being coupled‘ to the other electrode of ,
predetermined mean frequency by'meansof a 60, the condenser, one terminal of theload resistance .~
circuit arrangement comprising a direct current
,being'coupled to the other electrode of one of said
source, a resistance and current interrupting
r-ecti?ers, and the other electrode of the second
means responsive ,to said electrical oscillation
of said recti?ers and the other terminal of the
connectedin series with said source and resist 65 load resistance being coupled to an intermediate
ance, which comprises the steps of interrupting
voltage point in said direct current source, and
the current in said circuit in synchronism with
means to integrate said impulses to produce 'a
' half-waves of like sign of’ saidroscillation to ob
potential substantially proportional‘ to the fre
tain voltage pulsations across said vresistance,
quency of said oscillation comprising a ?lter coil
transforming said vvoltage pulsations, into elec-V 1 , pled to. said load resistance, the voltage‘at said
tricali impulses of like sign having an area sub—
stantially proportional to the voltage of said,
intermediate point having a value substantially
source, anamplitude independent of said oscil-.
potential at a frequency value of the oscillation
equal to the said predetermined mean frequency 1
l-ationand a duration smaller thanthe half-pea _
riods'of the highestfrequency to be.deteeted,-in
; telgratme said impulses .to obtain an. electrical
equal and opposite in sign to the‘ value of said
‘value;
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2,406,309
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5. A compensated frequency discriminator ac
cording to claim 4, in which the condenser is
adjustable and varies the frequency at which the
said compensated output potential is zero.
6. In a frequency stabilizing system, means for
of the direct current source in opposition to the
said potential to produce an output voltage com
pensated to zero independently of voltage varia
tions in said source at frequency values of the
main oscillation equal to said desired value, means
generating a main oscillation the frequency of
which is to be maintained at a predetermined
to connect said integrating means tovsaid fre- ,
value, frequency adjusting means coupled to
said generating means, means for generating a
pilot oscillation differing from said main oscilla 10
tion by a predetermined frequency, means for
mixing said pilot and said main oscillations to
produce a difference oscillation, a circuit includ
ing a direct current source and a resistance,
quency adjusting means, and means to vary the
amplitude of said output voltage proportional to
intelligence to produce frequency modulation of
said main oscillation.
9. In a frequency modulation system, a main
oscillator the frequency of which may vary about
an adjustable stabilized value differing by a pre
determined amount from the frequency of a crys
means for interrupting the current in said circuit 15 tal controlled pilot oscillator, means for radiat
in synchronism with the half-waves of like sign a ring the energy of said main oscillation, means for
of said difference oscillation to produce voltage
pulsations across said resistance, means for trans
forming said voltage pulsations into electrical im
pulses of like sign having an area substantially
proportional to the voltage of said source, an
amplitude independent on said oscillation and a
duration smaller than the half-periods of the
adjusting the frequency of the main oscillator,
means for mixing said main and said pilot osoil~
lations to produce a difference oscillation, a ther
mionic tub-e having a control electrode, an anode
and a cathode, a resistance and a direct current
source serially connected between the anode and
cathode, a potentiometer connected in shunt with
highest frequency of said difference oscillation,
said
direct current source, means to apply said
means to integrate said impulses to obtain a po
difference oscillation to said control electrode to
tential substantially proportional to the frequency 25 produce
voltage pulsations across said resistance
of said difference oscillation and to said voltage,
in synchronism with half waves of like sign of
means to connect said integrating means to said
said difference oscillation, means to transform
frequency adjusting means to maintain said main
said voltage pulsations into electrical impulses of
oscillation at said predetermined frequency value,
like sign having an area substantially propor
and means to inject a fraction of the voltage of 30 tional to the voltage of said source, an amplitude
the direct current source in opposition to said
independent of said difference oscillation and a
potential to produce an output voltage compen
duration smaller than the half periods of the
sated to zero independently of voltage variations
difference oscillation comprising a condenser hav
in said direct current source at frequency values
35 ing one electrode coupled to the anode circuit of
of the main oscillation equal to said predeter
said tube, two half wave recti?ers having anode
mined value.
and cathode electrodes, and a load resistance, the
7. A frequency stabilizing system, according to
cathode of one of said recti?ers and the anode
claim 6, in which the relation between said volt
of the other recti?er being coupled to the other
age fraction and said potential is adjustable, and
‘electrode of the condenser, one terminal of the
the frequency at which the main oscillation is
load resistance being coupled to the other elec
stabilized is variable before and during operation.
trode of one of said. recti?ers, and the other elec
8. In a frequency modulation system, means for
generating an electrical oscillation the mean fre
quency of which is to be stabilized at a desired
value differing by a predetermined amount from >
the frequency of a pilot oscillation generated in
said frequency modulation system, frequency ad
justing means coupled to said main oscillation
generating means, means for mixing said main and
said pilot oscillations to obtain a difference oscil- "
lation, a circuit including a direct current source
and a resistance, means to interrupt the current
in said circuit in synchronism with half-waves of
like sign of said difference oscillation to produce
voltage pulsations across said resistance, means
for transforming said voltage pulsations into elec
trical impulses of like sign having an area sub
stantially proportional to the voltage of said
source, an amplitude independent of said oscilla- -
tion and a duration smaller than the half-periods
of the highest frequency of said difference oscilla
trode of the second of said recti?ers and the other .
terminal of the-load resistance being coupled to
the movable arm of said potentiometer, and
means to integrate said impulses to produce a po»
tential substantially proportional to the frequency
of said difference oscillation and to the voltage of
said source comprising a ?lter coupled to said
load resistance, said movable tap being positioned
at a point at which the voltage thereat has a
value substantially equal and opposite in sign to
the value of said potential at a frequency value of
said difference oscillation equal to the mean fre
quency value of said difference oscillation, said
filter circuit being connected to said frequency
adjusting means to maintain said main oscillation
at the desired stabilized value, and means inserted
between said ?lter circuit and said frequency ad
justing means for additionally varying the ampli
tude of said compensated output voltage propor
tional to intelligence to produce frequency modu
tion, means to integrate said impulses to produce
lation
of said main oscillation about said sta
a potential substantially proportional to the fre
bilized value.
.
'
quency of said difference oscillation and to said
MARC
ZIEGLER.
65
voltage, means to inject a fraction of the voltage
MANUEL JULIO KOBILSKY.
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