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Патент USA US3076953

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Feb. 5, 1963
M. COOPERMAN
AUTOMATIC FREQUENCY AND PHASE CONTROL
3,0 76,943
Filed Oct. 9, 1958
2 Sheets-Sheet 1
Feb. 5, 1963
M. COOPERMAN
AUTOMATIC FREQUENCY AND PHASE CONTROL
3,0 76,943
Filed Oct. 9. 1958
y@
'i my”
INVENTOR.
M1 CHAEI. En UPERMAN
BY
W
Unite ätates arent 'dice
dß'ihßiiâ
Patented Feb. 5, i963
i.
2
3,076,943
Michael Cooperman, Haddon Township, Camden County,
varied until the correct oscillator frequency is selected,
AU'i'ûlt’îATlS FREQUENCY AND PHASE CGNTRÜL
and is set to this value.
In accordance with an illustrative embodiment of the
NJ., assigner to Radio Corporation of America, a cor
poration of Deiaware
invention, the frequency or phase of an oscillator circuit
is controlled by providing an error detector circuit, the
function of which is to determine only if the oscillator is
Fiied Oct. 9, 1958, Ser. N . 7á6,233
l2 Claims. (Cl. 331-4)
in phase or frequency synchronism. A control signal
>from the detector circuit determines merely the condition
This invention relates to automatic tuning ci-rcuits,
of a switching circuit connected to apply an auxiliary
particularly to such circuits using reactance devices that 10 signal
to a reactance control device of the type which may
exhibit a memory function with respect to their reactance
be set to a given value and which remains at this value
values.
Automatic tuning circuits, in present practice, generally
even after the setting signal is removed.
The reactance
device is connected with the frequency determining cir
control the frequency or phase, or both, of an oscillator
circuit in accordance with the deviation of the oscillator 15 cuit of the oscillator to control its frequency or phase.
If the >oscillator should drift from its prescribed re
from the frequency or phase desired. Error detecting
quency
or phase condition, the detector circuit senses the
circuits for detecting the shift of oscillator frequency or
drift and closes the switching circuit to apply the auxiliary
phase provide a contro-l signal that is indicative of the
signal to the reactance device. The auxiliary signal is
direction of the mistuning of the oscillator. To some ex
arranged to sweep the reactance value of the reactance
tent the error detector may also provide an indication of 20
device through many different values and at the point
the amount of mistuning. These automatic frequency
where the reactance value produces through its associated
control circuits are also generally operated in the form
circuit-ry the correct oscillator frequency, the detector cir
of a feedback loop, that is, the frequency of the oscillator
cuit control signal is reduced to a minimum and the
affects the output of the error detector and the erro-r de
switch-ing
circuit is opened, preventing further application
tector in turn affects the frequency of the oscillator. 25 of the auxiliary signal to the reactance device. The re
This loop action may give rise to problems of loop gain
and noise immunity in many types of commercial signal
receivers, such as television receivers.
Also, automatic frequency control of an oscillator in
actance value of the reactance device remains at the set
value and the oscillator signal is thus held at the correct
frequency or phase condition.
The invention, however, may be better understood
a receiver using present day techniques is dependent upon 30 when
the following description is read in connection with
a signal being present in the receiver. If no signal is
the accompanying drawings, in which:
present, the oscillator is uncontrolled. Under such cir
FIGURE l is a schematic circuit diagram of an oscil
cumstances, the oscillator frequency may be returned to
lator automatic tuning control circuit in accordance with
some quiescent value in the absence of a received signal
the invention;
which will allow the automatic frequency control circuit 35
FIGURE 2 is a graph showing curves illustrating cer
to operate in the proper manner when a signal is later re
tain operating characteristics of the circuit. of FIGURE l;
ceived. It is thus desirable to have a reactance device
which may be set to a particular- reactance value and
which will remain at this value even after the setting
FIGURE 3 is a schematic circuit diagram of an oscil
lator automatic frequency control circuit, illustrating an
other embodiment of the invention;
condition is removed from the device.
40
FIGURE 4 is a schematic circuit diagram of a television
In the last few years great strides have been made in
receiver having an automatic frequency control circuit for
the development and use of ferromagnetic devices. Many
the heterodyne oscillator of the receiver, illustrating an
of these devices exhibit characteristics such that the in
other ernbodiment of the invention;
ductance of a winding associated with one of these de
FIGURE 5 is a schematic circuit diagram of a signal
vices may be varied over a considerable range by a con 45
receiver
having an automatic frequency control circuit
trollable change in the permeability of the device. Many
in accordance with the invention;
of these devices exhibit a memory characteristic, that is
FIGURE 6 is a schematic circuit diagram of a portion
the permeability of the device may be set by a signal and
of a signal receiver having an automatic frequency con
the device `will retain the permeability setting even after
trol circuit for‘the local oscillator in accordance with an
the signal has been removed. One such device, the trans 50 other
embodiment of the invention; and
i'luxor, is described in an article appearing in the Proceed
FIGURE 7 is a schematic diagram of an oscillator auto
ings of the IRE for March, 1956, page 321 et seq., en
matic phase control circuit, illustrating yet another em
titled, “The Transiluxor” by Rajchman and Lo.
bodiment of the invention.
It is, therefore, an object of this invention to provide
Referring now to the drawings and particularly to FIG
an improved automatic frequency or phase control cir 55
URES 1 and 2, an oscillator 1t), which may be of any con
cuit for an oscillator.
.ventional type, has an automatic tuning circuit in accord
It is a further object of this invention to provide an irn
ance with the invention. A reactance device which ex
proved oscillator automatic frequency or phase control
hibits a memory characteristic, in this case a transiiuxor
circuit eliminating direct .feedback control of the oscil
device 12, is connected to the tuning or frequency-deter
lator phase or frequency.
mining
circuit 11 of the oscillator iti, and includes’a
It is yet a further object of this invention to provide an
control aperture 14 and an output aperture i6. An out~
improved automatic phase or frequency control circuit for
put Winding lil in the output aperture 16 is included in the
frequency determining circuit 1l of the oscillator 10.
an oscillator utilizing a reactance device having a memory
function in the control circuit.
In accordance with the invention, an error correcting
The control aperture i4 has a control winding Ztl therein
circuit for an oscillator, which has tuning elements, in
illustrated as a source of amplitude modulated (All/i)
cludes a reactance means connected to the tuning elements
of the oscillator. The reactance means is of a character
such that its reactance value may be set to any value with
which is connected to an auxiliary‘source of signal, here
signal 22, through a gate or switching circuit 24. With
the gate circuit 24 open n0 AM signal is applied to the
control winding 2G, but with the gate circuit 24 closed the
in a range of values. If the oscillator becomes mistuned, 7 O AM signal is connected directly to the control winding 2d.
the reactance value of the reactance means is randomly
The oscillator signal is applied to an error detector 26
3,076,943
3
whose output signal is applied to the gate circuit 24. The
function of the error` detector 26 is merely to provide an
indication of whether the oscillator signal is at the correct
tuning and to open or close the gate circuit 24 accordingly.
The simplest way of accomplishing7 this result is to provide
that the error detector 26 has no control signal output at
the correct oscillator tuning, but has an output signal if the
control aperture 14. In this embodiment, however, the
control winding Ztl is connected to an amplifier circuit 3i)
which in turn is connected to the AM source 22.
A por
tion of the output signal of the oscillator lil is fed through
a resistor 27 across a series resonant circuit 2d, comprising
an inductor 32 and a capacitor 3d, tuned to the desired op~
erating frequency for the oscillator lil. Connected across
the series resonant circuit 29 is a rectilier circuit 35, in
oscillator 1t) is mistuned.
cluding a diode 36 in series with a resistor~capacitor net
If the oscillator signal is correctly tuned, no control
work, comprising a resistor 3S and a capacitor liti, con
10
signal output is provided by the error detector 26 and the
nected in parallel. Any voltage that may appear across
gate circuit 24 is open. No AM signal is applied to the
the resistor 33 is connected by the lead 4t2 to the ampli
control winding 2t) of the transiiuxor 12. However, if
fier 30.
the oscillator 1G should become mistuned in phase or fre
In operation, if the oscillator lil is at the prescribed
quency, a control signal is available from the error detec
frequency, a »minimum voltage is developed across the
tor 26 which serves to close the gate circuit 24 to allow
series resonant circuit 29, since the series resonant cir
the source of AM signal 22 to be applied to the control
cuit 29 is at its minimum impedance and the resistance of
winding 20 of the transiluxor device 12.
The action thus provided is best illustrated in FIGURE
the resistor 27 is constant.
Little or no signal is thus
available for rectification by the rectifier circuit 35 and
2, which shows the hysteresis loop characteristics of the
little or no voltage is thus developed across the resistor
transfluxor device 12, and is a plot of the magnetizing 20 38. The bias of the amplifier Sii is controlled by the
force (H) against the magnetic liuX density (B). As
voltage available across the resistor 38 and the amplilier
sume for the moment that the transñuxor device 12 has
no flux therein. lts condition will then be illustrated by
the point a on the B-H curve of the device. As the
AM signal is applied to the control winding 14 the mag
netizing force H changes in a cyclic manner to sweep the
transiiuxor 12 through many permeability conditions.
The inductance or reactive value of the output winding
18 is determined by the permeability of the transfluxor
is cut ofi at minimum or zero voltage across the resistor
38. Thus, the amplilier Sil serves as a gate circuit in the
manner described in the circuit of FIGURE l.
If the oscillator should drift from its prescribed fre
quency, the impedance of the series resonant `circuit 29
increases, causing a larger voltage to be developed there
across and providing a signal to the rectitier 36. A direct
30 control signal voltage is thus developed across the re
17. Thus the iiux condition of the transfluxor 12 begins
sistor 38. The control voltage is coupled by the lead d2
at point a, is driven to point b, then to points c. d, and e in
to
the amplifier Sil which is biased to conduct thereby.
succession. The instantaneous amplitude of the AM sig
The output of AM source 22 is then applied through the
nal determines the value of the magnetizing force (H),
amplifier 36 to the control winding 20 of the transtiuxor
and thus Van amplitude modulated signal will sweep the
magnetizing force through many different values. The - 12. The transñuxor 12 has its permeability swept in the
manner described with reference to FIGURE l. As the
number of permeability variations shown in FIGURE 2
reactance of the output winding 18 develops an oscillator
is merely illustrative, and the number and degree of varia
frequency equal to that which the series resonant cir
tions is determined by the modulation of the AM source.
The permeability of the transiiuxor 12 is swept across its ~ cuit 29 is tuned, no signal is available for rectification
entire range. At the point, however, when the varying 40 by the diode 36 and the control voltage on lead 42
permeability or iiux density B of the transfluxor at zero
magnetizing force H (such as points w, x, y, or z) pro
duces a reactive value in the inductance of the output
vanishes, biasing off the amplifier 30. No signal then
can be applied from the AM source 22 to the control
winding 20, and the permeability of the transiiuxor 12
remains at the last setting.
winding 18 of the correct value to give the required tuning
It will be noted that the circuit described in FIGURE
of the oscillator 14B, the control signal from the error de 45
3
includes
an amplifier Sil and an AM source 22. The
tector 26 disappears, and the gate circuit 24 is opened,
circuit of FIGURE 4 illustrates a manner of providing
disconnecting the AM source 22 from the control wind
their functions, that is, a gating circuit and an AM source,
ing 20 of the transfluxor 12. Sweeping of the transfluxor
in a television receiver in a much simpler manner.
12 is thus stopped and the inductance, and hence the re
active value, of the output winding 1S remains at that 50 Referring now to FIGURE 4, there is illustrated a
television receiver which includes an antenna 45 for
value last set by the AM source 22. The transfluxor 12
intercepting and supplying a television signal, including
“remembers” the permeability to which it was set and
a video carrier and sound carrier, spaced 4.5 mcs. apart
remains at this value until it is again swept by a signal
in present practice, to a radio frequency (RF.) amplilier
from the AM source 22.
It will be noted that there is no continuous interaction 55 48. The carriers are conveyed from the RF. amplifier
48 to a mixer circuit 5t) where they are heterodyned with
between the error detector 26 and the oscillator 10 during
a signal from a local Oscillator 52 to provide video and
the time when the oscillator tuning is being changed,
sound intermediate frequency carriers in the conventional
manner. The intermediate frequency carriers are ampli
output to again shift the oscillator tuning; but rather the 60 fied in an intermediate frequency (LF.) amplifier 5d
and applied to a detector circuit 56. In the detector
error detector 26 merely provides a signal to close a switch
circuit 56 the video intermediate frequency carrier is
24 to apply an AM source 22 to sweep the permeability
detected and the video and sound intermediate frequency
transfluxor 12. The correct oscillator tuning is thus ran
carriers are heterodyned in the conventional manner to
domly selected by the circuit. The entire function of the
error detector 26 is to allow such random selection to oc 65 provide an intercarrier sound signal of 4.5 mcs. The
detected video signal and the intercarrier sound signal are
cur. It will also be noted that if the oscillator signal
applied to a vid-eo amplilier 58 which further ampliñes
should be cut ofi from the error detector 26 that the oscil
and applies the video signal to a kinescope oil. The inter
lator 10 will continue to oscillate at the tuning last set
carrier sound signal is removed from the video ampliiier
by the sweeping of the transfiuaor 12.
Referring now to FIGURE 3, the oscillator circuit 10 70 58 and applied to a sound processing circuit di), where the
intercarrier sound signal is ampliñed, detected, and applied
again includes a transñuxor 12 associated with its fre
to a loudspeaker device 62. Also, in a conventional
quency determining circuit 11. The output winding 13
manner, the synchronizing components of the Video sig
in the output aperture 16 is again included in the fre
nal are separated therefrom by a synchronizing signal
quency-determining or tuning circuit 11 of the oscillator
10; and the control winding 20 is again connected to the 75 separating circuit 64 and applied to the horizontal and
that is, the error detector output does not shift the oscil
lator tuning, which in turn again shifts the error detector
attracts
vertical deflection circuits 66 of the television receiver,
which produce proper currents and voltages to apply to
the deliection windings 69 of the ltinescope 6i) to properly
dei‘lect its electron beam. Finally, from the video ampli
:ñer SS may be derived an automatic gain control signal
lby an automatic gain control circuit 7d, which signal is
applied to the RF. and l.F. amplifiers 48 and 5d to con
trol their gains. The television receiver thus far described
is entirely conventional and forms no part or” the present
d
when a pulse is applied to the resonant circuit Se, so that
the frequency of the oscillator :'52 may be conveniently
changed during the horizontal or vertical blanking inter
val of the receiver.
T Ae vertical rate has proved satis~
factory, even though it is at a relatively low frequency.
It Will be noted that the embodiments of the invention
that have so far been described have illustrated control
of the oscillator from the oscillator signal directly, with
out the interposition of other elements such as inter
10 mediate Írequency amplifiers. Also, all of the previously
described embodiments have included a separate source
of amplitude modulated signal of one sort or another.
the resistor 27, the series resonant circuit 2@ and rectiñer
The circuit shown in FIGURE 5, to which reference is
circuit 35 connected to the signal output circuit of the
oscillator 52. ri`hese circuits are identical to those de 15 now made, illustrates that the invention is applicable to
the control of a local oscillator in a superheterodyne re
scribed in FÃGURE 3 except that the rectifier load re~
ceiver using the intermediate >frequency of a receiver and
sistor 38 is returned to ground in a slightly different
that an' auxiliary source of amplitude modulated signal
mann-er, as will be more fully explained hereinafter. The
is
not required. The receiver illustrated in FIGURE 5
oscillator circuit 52 also includes as a reactance device
includes an antenna 9*@ to intercept and apply a received
a transñunor l2 together with its control and output
signal to a radio frequency amplifier 921, which ampliñes
apertures ld and iti and control and output windings lli
the
signal and applies it to a mixer 94. ln the mixer 94
and Ztl, which are connected to the frequency determin
the signal is heterodyned with an oscillator signal from
ing circuit 53 of the oscillator 52 in a manner identical
a local oscillator 96 to develop an intermediate frequency
to that described in FIGURE 3. The control signal volt
age that may be available across the resistor 3S of the 25 signal, in the usual manner, which is applied to an inter
mediate frequency ampliiier 9S. The signal, after proc
detector circuit 35 is applied to a gate control Winding 74
essing by the intermediate frequency amplifier 93, is ap
on a second transliuxor 76 by connecting the resistor 3S
invention.
,
An automatic frequency control circuit for the local
oscillator 52, in accordance with the invention, includes
and the gate control winding 74 in series between the
rectider 35 and ground for the system. A gate output
plied to any desired utilization circuit liiti, which may,
in' a typical case, consist of conventional television re
ceiver circuits, such as previously described with refer
winding 73 on the second transliuxor 76 is connected in 30 ence
to FIGURE 4.
series with the control `¿vinding 2t! of the transl'ruxor l2.
In accordance with the invention, an automatic fre
.In order to provide an amplitude modulated signal,
quency control circuit for the local oscillator $6 includes
similar to that described with reference to the AM source
an error detector M32; connected to receive a portion of
22, of FIGURES l or 3, a parallel resonant circuit 8€),
the output signal of the intermediate frequency amplifier
including an inductor 32 connected in parallel with a
93. The error detector to2 may be of the -type shown
capacitor 8d, is provided. A resistor d6 is connected in
in FIGURES 3 and Ál, that is, a series resonant circuit
seri-„s with the indu-:tor SZ and the control winding 2li
feeding a rectifier circuit. The output or” the detector i612
of the transliuxor l2 is connected across this resistor
is
fed through a lowpass filter ldd, to remove any spurious
through the gate output winding ’78 of the second trans
high frequency signals that may be present, to one ter
iiuxor 76. ln order to provide the AM signal, it is only
minal ot a storage capacitor lilo. The other terminal of
necessary to apply a pulse signal from a source of pulse
the storage capacitor litio is connected to ground or a
signals S7 across the parallel resonant circuit Sii. Such
point of reference potential for the receiver. The un
a pulse signal is available at a number of places in a tele
grounded terminal of the storage capacitor lilo is con
vision receiver, such as, in the horizontal and vertical
deflection circuits, as is known by those skilled in the art. 45 nected to one of the collector-emitter electrodes MS of
a bidirectional transistor lill. The other collector-emitri‘he pulse signal applied to the resonant circuit Si? will
ter electrode il?. of the transistor il@ is connected to the
cause the circuit to ring and provide damped oscillations
control Winding 24B of a reactance transiiuxor l2. The
across the circuit. These damped oscillations are suit~
transtluxor l2 may `be identical to those Shown and de
able as for the AM source.
scribed previously. rEhe other end of the control Winding
The operation of the circuit of FIGURE 4 is almost
Ztl is connected to ground. As has been previously de
identical to that of FIGURE 3, with the exception of the
scribed with respect to FIGURE 4, the output winding i8
pulsed operation. If the frequency of the oscillator 52
of
the reactance transíiuxor .l2 is connected in' the fre
is correct, no control voltage will be developed across the
quency determining or tuning circuit lo@ of the oscil
resistor' 3d of the rectifier circuit 3.5', and no control cur
lator
rent will be applied to the gate control Winding 7d of the
Tlîie bidirectional transistor liti may be of the type dis
second tra . iuxor To. The inductance of the gate output
closed in a patent issued to Szilclai on December 27, i955,
winding W is then a high impedance and little of the
Patent No. 2,728,857. Brieliy, such a bidirectional tran
ringing signal from the parallel resonant circuit 3d’ Will be
sistor is able to conduct current in both directions, the
applied to the control winding 2@ of »the translluxor 12.
direction of current ilow being determined 'oy the bias
îowever, if the oscillator
should drift from its pre
on the electrodes. When the transistor is conductive, or
scribed frequency, a control voltage will be developed
in. the closed state, it presents a low impedance between
cross the resistor
and provide current flow through
its pair of collector-emitter electrodes; but when it is
the gate control Winding 7d of the second transtluxor 76.
non-conductive, or in the open' state, it presents a high
rîhis action decreases the impedance of the gate output
lo and allows the ringing signal of the resonant
impedance. ln order to insure Ithat the 'transistor 1li?
Winding W"
Circuit Sil to be applied to» the control Winding
of the
conducts only during the required times, it is normally
transfluxor l2. This ringing signal will sweep the per
biased to the non-conducting or open state by connecting
meability of the transliuxor l2, as described with refer
the base electrode M3 thereof to the junction point of a
ence to FÍGURE l, until the proper oscillator tuning is
voltage divider, comprising a pair of serially connected
reached, at Which time the control voltage from the recti~
resistors lle and lid connected between ground and a
70
lier 3S disappears preventing current iiovv in the gate
source of potential positive with respect to ground. In
control winding ’itl and causing the gate output winding
order to rende~ the transistor liti conductive or in the
‘ì'âi of the second transl‘luxcr 725 to become a high im*
closed state at the proper time, since pulse operation as
pedance and stop the sweeping action.
described in connection with FlGURE 4 is necessary, a
The sweeping action in this embodiment can only occur 75 gating pulse signal from a source of pulse signals 87 is
3,076,943
applied to the base electrode 113 of the 4transistor l11i)
through a coupling capacitor 121i.
In operation, if the local oscillator 96 is at the proper
frequency to produce the required LF. signal the detector
circuit 1112 produces no output signal. In a television
receivfr, either the video or sound l.F. frequency may be
used. If, however, the oscillator is at such a frequency
that an incorrect LF. signal is being produced, a control
signal voltage is generated by the detector 1112 and applied
8
tive by a voltage divider. Again, as in FIGURE 5, a
gating or pulse signal, which periodically renders the tran
sistor 11% conductive, is supplied from a source of pulse
signals 87 through a coupling capacitor 1219 to the ‘oase
electrode 113 of the transistor 11o.
The output winding 1S of the transfluxor 12 is the in
ductive portion of a parallel resonant circuit 139, which
comprises the output winding 1S and a capacitor 149 con
nected thcreacross. A source of alternating signal 142 is
connected through a resistor 14141 across the parallel reso
through the lowpass ñlter 1114 to the storage capacitor 10 nant circuit 139. The alternating signal that is developed
106. This action charges the storage capacitor 1116 with
across the parallel resonant circuit 13€;` is rectified by a
the control voltage during the interval when the transistor
diode 11o and developed across a resistor-capacitor net
11€) is biased to a non-conductive state. When a pulse is
work, comprising a resistor 1418 and a capacitor 1511 con
applied to the base electrode 113 of the transistor 119,
nected thereacross. The direct voltage developed across
the transistor 1141 becomes conductive and the charged 15 the resistor 143 is applied through a choke coil 152 to the
storage capacitor 1116 will be connected directly there
diode 136 to control the reverse bias and hence the capaci
through to the control winding 20 of the transñuxor 12.
tance
thereof.
This will provide a circuit containing an inductance and
if the frequency of the oscillator 132 is such as to pro
a charge capacitor. The energy will be transferred alter
duce the correct intermediate frequency, the error detec
nately from the capacitor 196 to the control winding 211
tor 138 produces no control signal and the voltage stored
and back to the capacitor 106, and a ringing signal will
in the capacitor 106 is zero. However, if the oscillator
thus be developed across the control Winding 2t). The
frequency should drift from its correct value, the error
ringing signal will be gradually damped, and is, in effect,
detector 138 will be driven by an incorrect intermediate
a modulated signal applied to the control winding 211; and,
frequency and will produce an output signal to charge the
as has been previously explained, Will sweep the perme
storage capacitor 1116. As a pulse signal is periodically
ability characteristics of the transñuxor 12 in order to
applied to close the transistor 11d, the storage capacitor
change the reactance of the output winding 1S to reduce
1116 will discharge through the control winding 2@ to pro
the oscillator frequency error to zero. No error signal
vide a ringing signal and to vary the permeability of the
will then be developed by the detector 102 and the action
transfluxor 12. As so far described, this action is the same
is stopped. The gating or pulse signal is applied period
ically to the transistor 110 in order to condition the cir
cuit for automatic frequency control action, if the detector
1132 produces an error signal. Such pulse signals are
readily available in television receivers and could easily be
supplied by a single multivibrator in receivers where pulse
as that shown and described in the FIGURE 5.
In FIG
URE 5 the inductance of the output winding 18 of the
transfiuxor 12 was used to directly control tue frequency
of the oscillator.
In this circuit, however, the output winding 1S is a
portieri of a parallel resonant circuit 139, resonant to a
frequency such that the frequency of the alternating sic,
signals are not normally available.
In some instances it may be undesirable or impossible
nal source 142 normally lies on the slope of the resonance
to control the frequency of an oscillator circuit directly
characteristic of the parallel resonant circuit 139. The
from the inductance of a winding associated with the 40 normal voltage thus developed ac; oss the parallel resonant
transñuxor 12. An instance of this situation would be
circuit is rectified by the .diode 146 and applied to the
if the oscillator were operating at a frequency above that
diode 136 as the normal reverse bias therefor. However,
at which transñuxor operation is sufficient or even feas
if the frequency of the oscillator 132 is incorrect, the tun
ible. The circuit shown in FIGURE 6 iliustrates how the
ing of the parallel resonant circuit will be randomly
invention may be used to provide a Voltage variation and 45 changed by the discharge of the capacitor through the
memory instead of an inductance variation and memory.
control winding 20 to change the inductance of the output
The circuit here illustrated is a portion of a superhetero
winding 15. As a ringing voltage appears across the con
dyne radio receiver and includes a mixer circuit 130 to
trol winding 211 the permeability of the transfluxor 12 is
gether With a local oscillator 132 and an intermediate
swept to provide a varying impedance across the parallel
frequency amplifier 134 which is supplied with signal from 50 resonant circuit 139 at the auxiliary source frequency.
the mixer circuit 131B. The remainder of the receiver has
This produces a varying voltage across the parallel reso
not been illustrated and may be a conventional receiver
nant circuit, which produces through the rectifier 146 a
varying bias on the reactance diode 136. The oscillator fre
circuit.
In order to maintain the oscillator frequency at the
quency is thus varied, and at the point where it is at its
correct value, there is provided a reverse biased reactance
correct value, the error detector 138 produces no signal
diode 136 which is connected across the frequency deter
and the control winding 2d of the transiiuxor 12 is no
mining or tuning circuit 131 of the oscillator 132, in a
longer energized at each conduction of the transistor 110.
conventional manner. Variation of the reverse bias across
The permeability of the transñuxor 12 thus remains at the
the reactance diode 136 produces a variable capacitance
setting which gives the correct operating bias for the re
thereacross which varies the tuning of the oscillator 132. 60 actance diode 13o and produces the correct oscillator fre
In order to provide a control voltage for the reactance
quency. At the correct frequency the inductance of the
diode 136, signals appearing in the 1F. amplifier 134 are
winding 1S is not varied by the circuit, and the tuning of
the parallel resonant circuit 139 is not being varied. Since
be similar to those shown in FIGURE 4 of the drawing.
the tuning of the parallel resonant circuit 139 is not now
The output of the error detector 138 is applied to a stor 65 being varied, the alternating voltage applied to the diode
age capacitor 106 and the storage capacitor is connected
146 is not varied, and the direct voltage applied to the
reactance diode 136 is thus held constant. The trans
to a bidirectional transistor 110 in the same manner as
fluxor 12 may thus be used to control oscillator frequen
shown in FIGURE 5, that is, to a ñrst collector-emitter
cies which are far beyond the range Within which it may
electrode 1113. The second collector-emitter electrode 112
of the transistor 110 is connected to the control winding 70 be used directly, since the frequency of the alternating
signal source 142 may `be a frequency Within the operating
20 of a transtiuxor 12 and the other end of the control
range of the transtiuxor 12.
winding 20 is connected to ground for the system. The
Referring now to FlGURE 7, there is illustrated an
transistor 110 is controlled in the same manner as de
oscillator
circuit whose phase may be controiled with re
scribed in FIGURE 5, with the base electrode 113 being
biased to render the transistor 1111 normally non-conduc 75 spect to a reference signal in accordance with another
applied to an error detector 138. The error detector may
at
9,076,943
aspect of the invention. The oscillator 16d includes a
frequency determining circuit 162, having a capacitor 161i»
and an inductor loe connected in paralÍel. The output
winding 1S of a frequency control transliuxor 12 is con
nected in series with the inductor M6. rfhus, the oscil
later frequency is determined by the values of the capa
citor ldd, the inductor lied, and the output Winding i3 of
the transfluxor i2. In order to control the phase of the
nant circuit for rectifying the signal across said series
resonant circuit to provide a control signal when said
oscillator is mistuned.
3. An error correcting circuit for an oscillator having
tuning elements comprising in combination, a reactance
device having a reactance value which may be set to any
value yWithin a range of values and connected with said
tuning elements to control the tuning of said oscillator,
oscillator lei) in accordance with a reference signal, a por
tion of the oscillator output is applied to a phase detector 10 means providing an auxiliary signal, error detecting
means responsive to said oscillator frequency for provid~
log, which also has a source of reference signal 176 ap
ing a control signal when said oscillator is mistuned, and
plied thereto. If the oscillator signal and the reference
means responsive to said control signal for applying said
signal are in phase, a normal output voltage is derived
auxiliary signal to said device to vary the reactance value
from the phase detector ldd and applied to a reactanco
device 169 and to one side of a capacitor Het. The other 15 of said device at random to select and set the reactance
value of said device to produce the correct tuning for
side of the capacitor 17d is connected to the slider §73 of
said oscillator and to thereafter remove said auxiliary
a potentiometer 135), which is connected between a source
of positive potential B+ and ground for the system. A
signal from said device.
4. An automatic error correcting circuit for an oscil
voltage is set on the potentiometer
that is equal to
the normal output voltage at the phase detector 168, so 20 lator having frequency determining ele-ments to deter
mine the tuning of the oscillator, comprising in combi
that W ien the oscillator lod is properly phased no voltage
nation, reactance means >having a reactance value which
is deveîoped across the capacitor 17d. `Connected across
may be set to any reactance value Within a range of
the capacitor 174 is the series combination of the control
values connected with said frequency determining ele
winding Ztl of the transiiuxor 12, a second induîtor E33
and a bidirectional switch transistor illu. The bidirec 25 ments to control the tuning of said oscillator, means re
sponsive to mistuning of said oscillator for randomly
tional transistor liltl, together with a source of pulse sig
varying the reactance value of said device within said
nals S7, is connected and operated in the same manner
range of values to select and set said reactance means
as has been previously described in connection with FiG
URES 5 and 6.
to a reactance value producing the correct oscillator tun
ing.
In operation, the correct phase between the oscillator 30
5. An automatic error correcting circuit for an oscil
signal and the reference signal produces no change in
lator having frequency determining elements to deter
oscillator tuning by the reactance device M9 and no
mine the tuning of the oscillator, comprising in combina
charging of the capacitor 17d. If, however, the oscillator
signal and the reference signal are not in the proper phase
relationship, an output voltage other than normal Will be
provided by the phase detector i163. The reactance device
lio@ driven by the signal from the phase detector Mii
maintains the oscillator foil in instantaneous synchro
nism with the reference signal. The oscillator signal, how
tion, a ferromagnetic reactance lmeans having a perme
ability value which may be ser to any value Within a range
of values connected with said frequency determining ele
ments to control the tuning of said oscillator, and means
responsive to a mistuning of said oscillator for randomly
varying the permeability of said ferromagnetic reactance
ever, may synchronize to an improper phase and the 40 means to select and set said ferromagnetic reactance
means to a permeability value producing the correct
memory loop including the transfluxor 12 serves to cor
rect for steady phase mistuning. The capacitor ll’ïd» Will
thus have, during oscillator mistuning, a voltage there
oscillator tuning.
6. An error cor‘ec 'ng circuit for an oscillator hav
ing frequency determining elements to determine the
tuning thereof, comprising in combination, a ferromag
across and will charge during tne time that the transistor
liti is turned oif. When a pulse signal is applied to the
base electrode fifi of the transistor liti, it will be turned
on, or changed to the closed state, and the capacitor
2174 will discharge through the control winding E@ of the
transr'luxor l2 and the second inductor 152, which pro
may be set to any value within a range of values and
Having thus described the invention, what is claimed is:
applying said auxiliary signal to said control winding
netic reactance `device having a permeability value which
having an output Winding and a control Winding thereon,
means for connecting said output winding with said fre
quency dcterming elements to control the tuning of said
vides sufficient inductance in the circuit to generate a
ringing signal. A ringing signal Will thus appear across 50 oscillator, means providing a source of auxiliary signal,
a gate circuit, means for connecting said source of auX
the control Winding Ztl of the transfluxor l?. and sweep
iliary signal to the control Winding of said ferromagnetic
the permeability of the transiiuxor l2 in the manner de
reactance device through said gate circuit, an error de
scribed in connection ‘with FIGURE l. The oscillator
tecting circuit responsive to the tuning of said oscillator
frequency is continually shifted in this manner until the
and for providing a control signal when said ocillator is
phase deîector output is normal and does not charge the
mistuned, and means for applying said control signal
capacitor 17d between pulse signals. The oscillator is thus
kept properly synchronized.
to said gate circuit to control the conduction thereof for
l. An error correcting circuit for an oscillator having 60 for randomly varying the permeability of said device
to select and set said permeability to a value to produce
tuning elements, comprising in combination, a reactance
the correct oscillator tuning.
device having a reactance value which may be set to any
7. An error correcting circuit for an oscillator having
value Within a range of values and connected with said
frequency determining elements to determine the tun
ing thereof, comprising in combination, a ferromagnetic
oscillator for providing a control signal when said oscil 65 device capable of having the permeability thereof set to
tuning elements to control the tuning of said oscillator,
error detecting means responsive to the frequency of said
lator is mistuned, and means responsive to said control
signal for varying the reactance value of said device at
random to select and set the correct tuning for said oscil
lator.
any value `within a range of values and having an out
put Winding and a control winding thereon, means for
connecting said output winding with said frequency de
termining elements to control the tunning of said oscilla
2. An error detecting circuit as defined in claim l 70 tor, a source of auxiliary signal, a gate circuit, means
for connecting said source of amplitude modulated signal
to the control Winding of said ferromagnetic device
through said gate circuit, an error detecting circuit con
mum signal thereacross when said oscillator is properly
nected to receive a signal indicative of the tuning of said
tuned, and rectilier means connected to said series reso
75 oscillator and to provide a control signal in response
wherein said error detecting means includes a series reso
nant circuit connected to said oscillator to provide a mini
adresse
pulse signals; a storage capacitor connected to said error
thereto, and means ‘for applying said control signal to said
detecting means to be charged by said control signal dur
gate circuit to control the conduction thereof for apply
ing the interval between said pulse signals; a gate circuit
ing sai-d auxiiiary signal to said control Winding when
having an open and a closed state and normally being in
said oscillator is mistuned for randomly varying the
the open state; means for serially connecting said gate cir
permeability of said device to select and set said perme Ul cuit, said storage capacitor, and said control Winding; and
ability to a value to produce the correct oscillator tun
means for applying said pulse signals to said gate circuit
ing.
to change its condition -to the closed state to develop a
elements to control the tuning of ysaid oscillator, a source
netic reactance device having an output Winding and a
8. An error correcting circuit for an oscillator hav
ringing signal across said control Winding for randomly
ing frequency determining elements, comprising in corn
varying the reactance value of said device to select and
bination, a ferromagnetic device having an output wind 10 set the correct tuning for said oscillator.
ing and a control Winding thereon, means for connect
ll. An error correcting circuit for an oscillator having
ing said output winding with said frequency determining
tuning elements, comprising in combination, a ferromag
of auxiliary signal, an error detecting circuit connected
to said oscillator providing a control signal when said
oscillator is mistuned, and means responsive to said con
trol signal for applying said auxiliary signal to said con
trol winding to randomly select and set said ferromagnetic
device to produce the correct oscillator tuning.
control Winding and having a reactance value which may
be set to any value Within a range of values, means for
connecting said output Winding to said tuning elements to
control the tuning of said oscillator, error detecting means
responsive to the frequency of said oscillator for provid~
ing a control signal when said oscillator is mistuned,
9. An error correcting circuit -for an oscillator having 20 means providing a source of periodically recurrent pulse
tuning elements, comprising in combination, a parallel
resonant circuit including a reactance device having a
reactance value which may be set to any value Within
signals, a gate circuit having an open and a closed state
and normally being in the open state, a source of auxil
iary signal, means for connecting said source of auxiliary
a range of values and connected in parallel with a ca
signal through said gate circuit to said control Winding,
pacitor element; means providing an alternating voltage 25 and means for applying said pulse signals to said gate cir
connected across said parallel resonant circuit; error de
cuit to change its condition to the closed state to apply
tecting means responsive to said oscillator frequency
said source of auxiliary signal to said control winding for
for providing a control signal 4when said oscillator is mis
randomly varying the reactance value of said device to se
tuned; means responsive to «said control signal for vary
lect and set the correct tuning for said oscillator.
ing the reactance value of said device at random to ran~ 30
12. An error correcting circuit for `an oscillator having
dornly vary the voltage across said parallel resonant cir
timing elements, comprising in combination, a reactance
cuit; and means connected to said tuning elements and
device having a reactance value which may be set to any
responsive to the voltage across said parallel resonant cir
value Within a range of values connected to control the
cuit for controlling the tuning of said oscillator.
tuning of said oscillator, means providing a source of
l0. An error correcting circuit for an oscillator having
periodically recurrent pulse signals, and means responsive
tuning elements, comprising in combination, a ferromag
to a mistuning of said oscillator and to said pulse signals
netic reactance device having an output winding and a
for randomly varying the reactance value of said device to
control Winding and having a reactance value at said out
select and set the correct tuning for said oscillator.
put Winding which may be set to any value Within a range
of values by a signal applied to said control Winding; 40
References Cited in the tile of this patent
means for connecting said output Winding to said tuning
UNXTED STATES PATENTS
elements to control the tuning of said oscillator; error de
tecting means responsive to the frequency of said oscillator
Gabor ______________ __ Oct. 29, l 1957
2,811,642
for providing a control signal when said oscillator is mis
Smith-Vaniz ________ __ July 28, 1959
45
2,897,5’
52
tuned; means providing a source of periodically recurrent
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