close

Вход

Забыли?

вход по аккаунту

?

код для вставки
NW. 12, 1946.
c. MQS|NNETT
2,411,008‘
TRANSDUCER SYSTEM
'
Fiil>ed Nov; 28, 1944
CAPACZMNCE AMPLIHER
05'C/LLA TOE’
7D
REZWFIER
26
I ‘ii/570°
CAPACITANCE
_
AMPLIFIER j .
M
OSC/L LA 70/?
"“
REC7/F/ER
came/72m:
INVEN TOR.
+8
CHESTER M. SINNETT _ v
BY
A TTOkA/EV
2,411,008
Patented Nov. 12, 1946
UNITED STATES PATENT OFFICE
2,411,008
TRANSDUCER SYSTEM
‘ Chester
Sinnett, Westmont, N. J., assignor to
Radio Corporation of America, a. corporation
of Delaware
Application November 28, 1944, Serial No. 565,462
7 Claims. ( Cl. 179_100.4)
1
lation of high frequency oscillations, and more
particularly to improved frequency modulated
(FM) oscillation systems for deriving from re
actance variations into electrical currents repre
sentative of such variations.
ganizations whereby my invention may be car
ried into effect.
In my application Serial No. 459,375, ?led
September 23, 1942, I have disclosed systems for
translating physical displacements of the mobile 10
electrode of a capacitative reactance into‘ FM
oscillations, a simple form of discriminator-recti
2
itself, however, as to both its organization and
method of operation will ‘best be understood by
reference to the following description, taken in
connection with the drawing, in which I have
indicated diagrammatically several circuit or
My present invention relates generally to trans
ducer systems of the type employing angle modu
~
In the drawing:
Fig. 1 shows an embodiment of the invention;
Fig. 1a, showsddeally a resonance curve of :the
discriminator section of the detector;
Fig. 2 shows a simpli?ed modi?cation wherein
the FM detector electrodes are embodied in the
?er being employed to derive ‘from the FM oscilla
capacitance ampli?er tube; and
tions electrical waves representativeof the afore
said physical displacements. In my said appli 15 Fig. 3 shows a further simpli?cation wherein
a special discriminator circuit is eliminated.
cation a small condenser was employed whose
Referring now to the accompanying drawing,
mobile electrode was stylus-actuated, and the
wherein like reference characters in the differ
condenser was connected directly across the oscil
ent ?gures designate similar circuit elements, the
'lator ‘tank circuit. The capacity variation across
the tank circuit is limited by the normally small 20 embodiment .of Fig. ‘1' is shown applied to a con.
denser or capacityv pickup device. However, there
maximum capacitance value of the pickup con
is no restriction to that form of transducer, since
denser.
the latter. may be a condenser microphone. Ad
It is one of the primary objects of my present
ditionally, the reactive input element may be any
invention to provide a method of amplifying the
pickup capacitance variations prior to utilization 25 form of reactance provided with a mobile element
for providing reactance variations representative
of the latter in varying the oscillatortank-ci-rcuit
of physical changes of force, space, temperature
frequency.
and the like. Assuming for the .purposes of my
Another important object of my invention is
present patent application that the input element
to convert a small capacitance variation by purely
the capacity pickup device of a record repro
electronic means into a large similar variation, 30 is
ducing
system, the pickup generally comprises a
and to employ the large variation :for angle
?xed electrode -.l and a spaced mobile electrode 2.
modulating an oscillator.
The spaced electrodes land .2 provide a con
Another object of my invention is to ‘provide in
denser
whose capacity varies in .accordance with
combination with a high frequency oscillator, a
transducer of the reactance type whose variations 35 the motion of a stylus secured to the mobile elec
trode 2. The pickup is schematically represented.
are utilized to vary the tuned circuit frequency
It is not a part of this invention, and reference
of a reactance tube whose input electrodes are
is made to my applicationSerial No. 414,305, ?led
coupled across the oscillator.
October 9, 1941, now Patent No. 2,376,456, dated
.Still another object of my invention is to pro
vides. variable condenser adapted to .be coupled 40 May 22, 1945, for a preferred pickup device.
Displacement of electrode ,2 causes a change in
across the tuned circuit of a reactance tube whose
the capacitance of the pickup. Displacement of
input capacitance is connected to vthe tank cir
a stylus‘ laterally, as ‘when scanning record
cuit of a high frequency oscillator, and the tuned
grooves, results in a change of the position of
circuit simultaneously acting as .a discriminator
of FM oscillations.
'
A more speci?c object of my invention is to
provide an FM phonograph system whose con
dense-r pickup unit has its capacitance variations
ampli?ed by causing the 'latterto vary the tuning
45 electrode 2 with respect to ?xed-electrode >l . The
?xed electrode l is represented as the grounded-or
low potential side oft-he condenser, while the
mobile electrode 2 functions as the high potential
side of the pickup device.
Whereas in the system-of my application Serial
of the resonant plate circuit of a reactance tube 50
No. 459,375 the pickup ‘device was connected di
whose input capacitance is connected across the
rectly-across the resonant tan-kcircuit of the high
oscillator tank circuit of the system.
frequency oscillator, in the ‘present system
The novel features which I believe to be char
capacitance changes of the pickup device are
acteristic of ‘my invention are set forthwith par
ticularity in the appended claims; the invention 55 ampli?ed by (means of an electronic device which
12,411,00é
.
4
3
I have termed a “capacitance ampli?er.” The
latter electronic device consists of an electron
discharge tube 3 which is shown, by way of speci?c
course F0 may be located on a suitable point of
the opposite ?ank of the resonance curve.
suitable direct current source through a coil 1,
Those skilled in the art of FM communication
are fully aware of the fact that the oscillations
produced in the tank circuit I5 are of substantially
constant frequency in the absence of capacitance
variation of the pickup I-2. However, varia
and the coil is shunted by a condenser 8.
tion of the pickup capacitance causes the am
example, as a triode.
The tube 3 includes a
cathode 4, a control grid 5 and a plate 5. ‘The
plate 6 is connected to the +B terminal of a
The
pli?ed capacitance I4 to vary the frequency of
The 10 tank circuit l5, and, of course, the frequency
low potential side of tuned circuit 1-8 is re- 7
variation or deviation will correspond to the
turned to ground for high frequency currents
capacitance variations at the pickup I-2. Var
by condenser 9. Numeral I0 denotes the cou
iations in frequency of the local oscillations will
pling path between the mobile electrode 2 and
result in developing across circuit 25-26 high
the high potential side of circuit 1-8. The 15 frequency oscillations whose amplitude will vary
cathode 4 may be connected to ground through
in accordance with the frequency variations oc
resonant circuit 1-8 is tuned to substantially the
operating normal oscillator frequency F0.
a biasing resistor H which is bypassed for high
frequency currents by condenser I2, and the con
trol grid 5 is returned to ground through a re
sistor l3 which acts as a direct current return 20
path for the control grid.
.It is to be clearly understood that the coupling
path In may be of any desired form. For ex
ample, it may be a coaxial cable whose grounded
sheath would be connected to the ?xed electrode
l. Merely by way of example, and in no way
restrictive upon the invention, F0 may be given
a value in the megacycle range such as 30 mega
cycles (mc.). The control grid 5 of tube 4 has a
curring at tank circuit l5. This is the well known
frequency discrimination action which has been
described in my aforesaid co-pending patent ap
plication.
Any suitable type of recti?er may be coupled
across circuit 25-26, as by coupling condenser
21, for the purpose of rectifying the high fre
quency oscillations of variable amplitude. The
recti?ed voltage produced during the recti?ca~
tion step corresponds to the capacitance varia
tions of the pickup element l-2. The recti?er
device coupled to the discriminator circuit 25-26
may be of any well known construction, as, for
predetermined capacity with respect to the 30 example, a simple diode. Where the mobile elec
trode 2 is varied by a stylus scanning sound
grounded cathode 4, and numeral [4 denotes this
grooves of a record, the voltage produced by the
input capacity, or inherent interelectrode capaci
recti?er coupled to circuit 25-26 represents the
tance, of the input electrodes of tube 3. The
audio frequency voltage corresponding to the re
capacity [4 is designated in dotted lines to repre
sent the fact that it is inherent, and is not an
actual physical condenser across the tank cir
cuit of the high frequency oscillator. The control
grid 5 is connected to the high potential side of
tank circuit I5 of the high frequency oscillator by
corded sound. In the case where'condenser l-2
is a condenser microphone the output of the sys
tem Will be the audio frequency waves corre
sponding to the sound waves varying the capaci
tance of condenser l-2.
In order to provide an ampli?cation of the rela
means of a direct current blocking condenser I6.
The low potential side of . tank circuit I5 is
tively small capacity changes of condenser 1-2
grounded. Tank circuit l5 consists of coil I‘! and
and shunt condenser I8, and the tank circuit is
normally tuned to the frequency F0.
The oscillator tube is designated by numeral l9
and is shown as a pentode type tube, although
my invention is not limited to that type of tube.
Since the present invention is concerned mainly
the tube 3 and its associated circuits are utilized.
Since the resonant circuit 1-8 of tube 3 is tuned
to F0, it follows that tube 3 will have a plate
circuit whose plate impedance is essentially re
sistive when circuit 1-8 is tuned to F0. It can
be shown that in any tube, such as tube 3 of
Fig. 1, whose plate impedance consists of a reso
with the circuit details between the reactive input ,
nant circuit tuned to the frequency of the high
element l-2 and the oscillator tank circuit 50 frequency voltage applied to the grid of the tube,
l'l-l8, the remainder of the system comprising
the input capacitance M will have its magnitude
the oscillator and discriminator-recti?er will be
depend upon the effective magnitude of the plate
impedance of tube 3. At resonance the input
capacity C1 of a vacuum tube ampli?er is given
generally referred to.
The oscillator tube cathode 20 is connected to
a suitable point on coil [1, control grid 21 being
connected by direct current blocking condenser
22 to the high potential side of tank circuit I5.
A suitable grid leak resistor 23 returns grid 2| to
ground. Plate 24 is connected through coil 25 to
the +3 terminal of a suitable direct current
source. Coil 25 is shunted by condenser 26, and
the resonant circuit 25-26 is tuned to a frequency
which is su?iciently different from the normal
oscillator frequency F0 to provide frequency dis
criminator action. In Fig. lo I have shown an
ideal resonance curve of circuit 25-26. The
peak frequency of the resonance curve is chosen
to be Fo+f, the value of 1‘ being such that F0 falls
by:
where M is the ampli?cation factor of the tube;
Cgk is the capacity between the grid and cathode;
and Cgp is the' capacity between cathode and
plate. This relation applies for a resistance load.
Since at resonance a tuned circuit possesses unity
power factor, the relation will hold for the cir
cuit shown in Fig, l for tube 3. If now the fre
quency of the resonant plate circuit of tube 3 is
varied relative to F0 the effective impedance of
the plate circuit varies. On either side of reso
nance (F0) the value of Cl decreases, and for the
speci?ed circuit is given by:
at the midpoint of the most linear section of one
of the ?anks of the resonance curve. If, for ex 70
ample, F0 is chosen to be 30 me, then .the dis
Due to this effect the input capacity IA of tube 3
criminator circuit 25-26 will be tuned to a peak
is re?ected into the oscillator tank circuit in
frequency sufficiently above 30 me. so that the
magni?ed form relative to the capacitance of
latter value will fall at a linear point of the lower
?ank of the resonance curve shown in Fig. 1a. Of
condenser l, 2.
2,5191 mos
.
,
.
6
5
.
lations into _ amplitude V modulated‘ oscillations.
‘This change in effect" of plate impedance of
fl‘lii’eflatter areiappliedto‘anode 30 of‘ diode rectié
tube 3v will be clearly magni?ed as a correspond;
ing variation in the, magnitude of the input
capacitance 14, and the‘ variation of capacitance
I4 will follow the frequency variation of circuit
'l'-—-8. It is for ‘this reason that the capacity
variation of capacitance M will frequency modu
"late the" high frequency oscillations produced at
tank ‘circuit [5; The extent of frequencydevia
?er’i’ril, AFthroi-igh condenser 45-' which has a small
capacity)‘
";
-
'
"
' The anode 30 is connected to ground through a
series path consisting of 'choke coil 3| and» load
resistor 32. Load resistor 32 is shuntedby con
denser. 33 which bypassesv high frequency cur
rents. ‘ ‘The recti?ed voltage across-resistor 32 is
am at tank circuit l5 will'be a function of the 10 appliedv through condenser 34 to the following
audio frequency network. The fact that: circuit
amplitude of physical displacement of mobile
electrode 2, while the rate of frequency variation
7, _8 is‘ tuned to Fo-l-f in no way interferes with
‘the function of the circuit» in ‘acting as the plate
will depend upon the rate of physical displace
ment. In the case of recorded sound the extent
of frequency variation at tank circuit IE will de
impedance 'of tube 3''.
pend ‘upon the amplitude of the recorded sound,
aridthe rate of deviation will depend upon the
and- down» the ?ank'of‘the resonance curve of
tuned circuitT, 8. This causes a change in voltage
audio' frequencies per se] The generic term
“anglemodulated” is'employed herein to indicate
the fact that the variations of the-high ‘fre
> Changes in pickup
capacity modulate the high frequency oscillations,
but the ampli?ed oscillator voltage also swings up
is
across the‘diode load resistor 32. '
a
‘quency-energy' at tank circuiti? could be phases
modulated, since frequency and phase modula
tiorr have characteristicsin common.
In Fig. 2 there is shown a modi?cation of‘ the
invention wherein the recti?er device coupled
"25
across discriminator circuit 25—~2i5 has its elec
trodes included within the tube envelope of the
capacitance ampli?er. Additionally, the leads it’
,
Tube 3’ is fundamentally a high frequency
ampli?er receiving its energy from oscillator tube
vl9.3Therewill appear across the tank circuit: 1,
‘8"anipli?ed energy derived from the oscillator.
The input capacity of tube >3'vis,‘however, con
nected‘across tank circuit l1, l3. ‘ From the
above ‘relation for vC'i'the tuning o-f'thelplate
circuit of tube 3’ has an effect on its input
capacity. Even when circuit 1, 8 is tuned o?
resonance with Fe it can be: seen fromtheabove
are an unshielded pair of twisted wires. It will
further be noticed that control grid 5 of tube 3' 30 formula thatv the eifectiveinput capacity becomes
a variabie'or a magnitude larger than the tube’s
normal‘ grid to cathode capacity. The variation
in‘ frequency of the oscillator is- ampli?ed‘ by tube
3', and-with its plate-circuitoff resonance large
changes in voltage occur across circuit 1.8., The
capacity. variations in ‘circuit ‘l, 8 dueto the pick
is connected directly to the high potential end of
oscillator tank'coil i1. Adjacent a portion of the
‘cathode 4 ‘of tube 3’ there is located the diode
anode 3i’! which is returned to the grounded
“cathode through a path consisting of the choke
coil 3! and load resistor 32, the latter resistor
~upfaresmall, but the changes in voltageare large ‘
being bypassed for; high frequency currents by
since. tube 3’- ampli?es‘ ‘the oscillator‘ output
condenser 33. The anode 38 is connected through
direct current blocking condenser 21 to the plate
_
'end of discriminator coil 25. The tube 3’ may
be a diode-triode of the 6Q7G type, although any
other well known type of multiple duty tube may
be employed.
The ' recti?ed audio " frequency
voltage across resistor 32 may be transmitted by
coupling, condenser 31; toany suitable audio fre
quency ampli?er network. The action described
in connection with Fig. 1 applies equally well to
the functions of the system of Fig. 2. Here again
the inherent input capacity of tube 3’ is Varied
in accordance with the variations in magnitude of
condenser [-2, and the input capacitance of the
triode section of tube 3' is provided across the
oscillator tank circuit as described for the system
of Fig. 1.
In Fig. 3 I have shown a further simpli?cation
of the invention. In this case discriminator cir
cuit 25—26 is completely dispensed with, ‘while
the resonant plate circuit of tube 3' is caused
to perform frequency discrimination in addition
to its function as described in Fig. 1.
In this .
"voltage at Foif.
l
'
Whi'le I. have indicated and described several '
systems for carryingimy invention-into effect, it
.40 .
will be apparent to one skilled in the art that'my ,
‘ invention is. bylno means limited to the particular >
organizations shown‘ ‘and described,»but‘ that
many modi?cations-may be made: without-.de
parting from theiscop'e of my, invention. :
What I claim is:
v
r
'1. In combination, an oscillator having a reso
nant tank circuit tuned to a desired frequency, a
reactance device having a displaceable element
responsive to a physical force for varying the
reactance of said device, and the improvement
which comprises an electron discharge tube hav-v '
ing at least a cathode, control grid and plate, a
, second resonant circuit connected beween the
cathode and‘plate tuned substantially to. said de
sired frequency, means electrically connecting
the grid to cathode capacity of said tube across ‘
said tank circuit, means connecting the reactance
60 device across said second resonant circuit for
providing frequency variations of the latter in
modi?ed system the resonant plate circuit 1, 8
response to displacements of said element there
of tube 3' is tuned to the peak frequency Fo+f,
by to cause corresponding variations of said grid
while the oscillator tank circuit ll, l8 of tube i9
to cathode capacity, and means for deriving from
is tuned to F0. The variations in capacitance
of condenser i, 2 cause corresponding variations 65 oscillations variable in frequency, due to said ca
pacity variations, a Voltage representative of said
in plate impedance of tube 3' thereby producing
physical force.
'
ampli?ed capacitance variations across tank cir
2. In combination with a high frequency oscil
cuit IT, IS. The FM oscillations across tank cir
lator producing oscillations of a predetermined
cuit I1, is are applied to grid 5, and there will be
developed in the plate circuit of tube 3' FM oscil 70 frequency, a condenser having a mobile electrode
responsive to forces to be reproduced, a tube hav
lations which are applied to circuit 1, 8. Since
ing a resonant plate circuit tuned substantially
circuit 7, 8 is tuned to Fo-l-J‘ and the FM oscilla
to said frequency, said condenser being connected
tions have a mean or center frequency F0, it '
directly across said resonant plate circuit to vary
follows that circuit 1, 8 acts in the manner of a
frequency discriminator to convert the FM oscil 75 the frequency thereof in accordance with move
2,411,008
7
8
mentsof the ,mobile, electrode, means responsive
to corresponding variations in'the input capaci
tanceof said tube for varying the frequency of
resonant tank circuit tuned to a desired high fre
said oscillations, and means for deriving from the
frequency-variable oscillations a voltage whose
variations are, representative of said electrode
movements.
,
3. In combination with a high frequency oscil
lator producing oscillations of a predetermined
frequency, a condenser having a mobile elec
trode responsive to forces to be reproduced, a
tube having a resonant plate circuit tuned sub
quency, a reactance device having a displaceable
element responsive to a physical force for vary
ing the reactance of said device, an electron dis
charge'tube having at least a cathode, control
grid and plate, a second resonant circuit con
nected between the cathode and plate tuned to
a frequency differing by a small value from said
desired frequency, means electrically connecting
10 the grid to cathode capacity of said tube across
said tank circuit, means connecting the reactance
device across said second resonant circuit for
stantially to said frequency, said condenser being
providing frequency variations of the latter in
connected directly across said resonant plate cir
response to displacements of said element thereby
cult‘ to vary the frequency thereof in accordance 15 to cause corresponding variations of said grid to
with movements of the mobile electrode, means
cathode capacity, and recti?er means in circuit
responsive to corresponding variations in the in
with said second resonant circuit for deriving
put capacitance of said tube for varying the fre
from oscillations variable in frequency, due to
quency of said oscillations, means for deriving
said, capacity variations, a voltage representative
from the frequency-variable oscillations a voltage 20 .ofsaid physical force,
whose variations are representative of said elec
6. In combination with a high frequency oscil
trode movements, said mobile electrode having a
lator tube producing oscillations of a predeter
record reproducing stylus coupled thereto, and
mined frequency, a condenser pickup having a
said deriving means including a recti?er whose
mobile electrode responsive to record grooves to
input circuit is said resonant plate circuit,
25 be reproduced, a tube having a resonant plate
4. In combination with a high frequency oscil
circuit tuned oif resonance with said frequency,
lator producing oscillations of a predetermined
said pickup condenser being connected directly
‘frequency, a condenser having a mobile electrode
responsive to forces to be reproduced, a tube hav
across said resonant plate circuit to vary the fre
quency thereof in accordance with movements of
ing a resonant plate circuit tuned substantially 30 the mobile electrode, means responsive to corre
to said frequency, said condenser being connected
sponding variations in the input capacitance of
directly across said resonant plate circuit to vary
said tube for varying the frequency of said oscil
the frequency thereof in accordance with move
lations, a recti?er whose electrodes are included
ments of the mobile electrode, means responsive
in the tube envelope of said tube, and a condenser
to corresponding variations in the input capaci 35 coupling said resonant plate circuit to said recti
tance of said tube for varying the frequency of
?er.
said oscillations, means for deriving from the fre
7. In combination with a high frequency oscil
quency-variable oscillations a_voltage whose vari
lator, a tube whose input capacitance is coupled
ations are representative of said electrode move
across a frequency determining circuit of the
ments, said deriving means comprising a recti?er 40 oscillator, a resonant circuit tuned away from the
whose electrodes are included in the tube en
oscillator frequency by a small frequency value
velope of said tube, and a frequency discrimina
connected in the tube plate circuit, and a modu
tor circuit coupling said) oscillator and recti?er
lating reactance device connected directly across
and tuned to a frequency close to said predeter
said resonant circuit,
mined frequency.
,
l
.
5. In combination, an oscillator tube having a
45
CHESTER M. SINNETT.
Документ
Категория
Без категории
Просмотров
0
Размер файла
705 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа