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Патент USA US2404408

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July 23,1946
2,404,408
A; D. SM1-FH, JR
RADIO RECIEVIN'G APPARATUS
Filed oct.v 19, 1945
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Patented July 23,1946
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RADIO RECEIVING APPARATUS
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i « `Archibald D. Smith, Jr., Amityville, N. Y., assign-` , v
or to Federal Telephone and Radio Corporation,
A v um Y’ `New -York,` N.’Y.,:a corporation of Delaware, ,
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application october-19,194s,seria1No.50s,79s
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_. Gentils.
((1250-20)
This invention relates to improvements in am-
fier 22 (if desired) an thence to a suitable- ref
,p_lifiers, andmore particularly toia lnovel reflex`
amplifying system for radio receivers.
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producer '23.
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The _intermediate frequency amplifier I_I, vac.,
object of this invention is to provide a novel
c'ordingv tothe present invention, may consist
and'v improvedreflex amplifier.
5 ofi one or `more stages. YThe input tothe inter
Another object of'this invention is tol provide
mediate frequency amplifier passes through vva
a novel radio receiving circuit in which the high
frequency amplifier tubes serve to amplify the
direct capacitative coupling _device I2, while the
output fromthe intermediatefrequency- ampli
low audio frequencies.
fier consists of _a similar coupling device,l as_.does
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i A further object of this invention is to provide 10 alsothe coupling between anyintermediate stages,
a _reflex amplifier in which the lower audio fresuch as indicated lgenerally at I3. The ydirect
,quencies arepassed through and are amplified by
capacitative coupling device in «accordance with
the radio frequency amplifier without mutual inthe present invention may consist of two induc
terference.
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-tors 24 and` 26 »spaced apart sorthat there will s
A still further object of thisinvention is to pro~ 15 Iloe no mutual coupling Vbetween them, the actual
_videa reñex amplifier in vwhich the input, output
coupling taking place through acommon con
and inter-jstage couplingdevices'of the radio frenection which is connected _to ground througha
quency amplifier are adapted to pass both the
common condenser v28. The inductors24 and_`26
_normal high frequencies _and the low audio fremay be adjustable so that with their inherent
_,quencies withoutgmutual interference.
20 capacities C and C', together with the condenser
Morespecifically, the present invention is di28, the circuit will be tuned tothe intermediate
rected to the use .of direct capacitative `coupling
¿frequency band desired. In this respect the cou
Vmeans in a radio frequencyamplifier which is also
pling in the `intermediate frequency amplifìerÍwill
usedl to amplify reñeXed .audio frequency currents.
actin theusual manner. If the low audio fre
« ¿ .An illustrative embodiment disclosing one form 25 _quency is fed, however, to the midpoint between
,of l_the invention together with a modiñed circuit
`the two coils, `to which the `condenser 28 is con
4detail thereof is shown in the accompanying
drawing in whiehg@A .
nected, 'this point willI representan Vappreciable
y
impedance for low frequencies. At`suchlow fre
V_.li‘ig.; 1_is a circuit diagram, partially in block 'f quencies, however, the impedance oi the individ
form illustrating a preferred embodiment of the 30 ¿ualcoils is negligible and the Coupling iS effeßted
present invention;and
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lsolely through thecapacitor 32.V For low fre
Fig. 2isa partial circuit diagram of a modified
coupling device adapted to be used in the circuit
quency ¿currents the capacitor 23 may be by»
passedby’a variable resistor 30 to control the low
shown in Fig. 1.
frequency coupling characteristics, this resistor
The present invention isîdirected to improve- 35 _Sewing @t m6524111? "time 21S 21D- C- path fOl‘ the
ments in what are known in the art as reflex
_anodeîcurrent of theprevious high frequency or
amplifiers, and in Fig. 1 I have illustrated by way
miXer Stäège. The type 0f Coupling deViCe d6
of example the application of my invention to a
scribed, therefore, serves both as coupling means
superheterodyne receiver. Such a circuit may
ÍOI‘ the relatively high intermediate frequency
consist of a first detector, mixer, local oscillator 40 currents and also for the relatively low frequency _
and the like, indicated at IIl, the output of which
audio currents which then are derived, prefer
is passed through an intermediate frequency amably from the last coupling device between the
plifier, generally indicated at II, to a second de-
intermediate" frequency amplifier and the second
tector I4. In accordance with the present inven- a detector I4. The low-pass filter 20 is used to
tion the audio frequency output derived from the 45 prevent passage of the high frequency currents
detector I4 is fed back to the intermediate frefrom the output of the intermediate frequency
quency amplifier I I through a de-coupling condenser I6 and a low-pass filter I8. After the
audio frequency currents pass through and are
amplifier to the audio frequency reproducer, While
the low-pass filter I8 is used to prevent the high
frequency currents derived from the input of the
A:amplified by the intermediate frequency ampli- 50 intermediate frequency amplifier, being impressed
' fier in a manner to be described in more detail
upon the detector circuit. In order to prevent the
hereinafter, such amplified audio frequency output is taken from the output of the, intermediate
high plate voltages from being applied to the grid
of the intermediate frequency amplifier tube 34,
frequency amplifier, passed through another lowor to the input of the detector tube (not shown) .
pass filter 20 through an audio frequency ampli- 55 condensers 32 may be inserted between the in
2,404,408
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ductor winding 26 and the common point connect
ing that inductor to the inductor 24 and the con
input circuit connected to said high frequency
amplifier through the iirst said input coupling
denser 28.
means,l a detector connected to the output cou
.
pling means of said high frequency'ampliñer,
In place of using an adjustable resistor 3U, the
means connecting the output circuit of saidV de- .
tector to the common connection of one of said '
condenser 28 may be'shunted by a variable in- Y
ductor 40 and a resistor 42, as shown in Fig. 2.
input coupling means of an amplifying stage, a
By propenadjustment lof the inductor 42, the
over-all- circuit for low-frequencies may be shunt
signal reproducing device, a low-frequency pass
filter, and means connecting said signalr repro
a flat band-pass characteristic. Other known 10'. ducing device to the common connection of an
output'coupling means following said one input
forms of band-pass (low frequency) compensa
peaked,'making the low frequency circuit have
tion could be used, if desired.
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coupling means through said low-pass ñlter.
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, , While the present invention has the general ad- d
vantage of all reflex circuits in permitting thev r '
` reduction of the number of required tubes, it hasj
Vthe further advantage of permitting the use of
several high frequency amplifyingïstïages as audio
. frequency stages by utilizing special coupling,
'means which will couple the ampliñer both for
rhighandA low frequencies without mutual inter
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2. The combination according tol claim 1, in
combination with a second low-pass filter inter
mediate connected between the output of said
detector and the said common connection of the
linput coupling meansvto an amplifying stage.
3. The combination according to claim 1, in
combination with variable impedance means in >
20 shunt with the common condenser of each cou- '
:While I have disclosed this invention specifi
pling means.l
4. The combination according` to claim 1, in Y
" ‘cally in connection'with a superheterodyne re
which the inductors and common condenser of Y
ference.
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each coupling means are tuned to the said high
ceiver, it will be obvious to those skilled in this
art that the invention is equally applicable to a 25 frequency band, in combination Withïa variable
multi-stage tuned> radio frequency receiver.V
inductance in shunt with said common condenser l
Furthermore, in a superheterodyne receiver, the
forming a i‘lat band-pass filter dimensioned to
shunt peak the circuit for the low frequency de
tector output.
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through the radio frequencyamplifying stage in
5. The combinationraccording to claim: 1, in
the same manner-"as described Withrespect to 30
which the detector output is fed to the input
the reflexing of the audio frequency. In this
coupling means of the ñrst high frequency am'case it is clear that the filter networks I8 and 20
pliiier stage, and the signal‘reproducing device
would be suitably dimensioned. The design of
is connected to the output coupling means of _the
the linductor coils used‘in each of the coupling
last amplifier stage.
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devices is not critical vexcept that there should be
intermediate frequency 'could be coupled back
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' 6. Radio receiving apparatus including, in
.no mutual inductance between the` coils. _The
coils may be provided with variable movable pow
combination, a high frequency ampliñerhaving
dered iron cores for tuning purposes, or they may
one or more relatively high frequency amplifying
stages, each of said stages including input and `
be tuned in other manners known to the art.
Accordingly, while I have described above the 40 output direct capacitativecoupling means, com
prising a pair of uncoupled inductors having a
principles of myginvention in connection with
common'connection and a common condenser
specific apparatus, together with a particular
connecting said common connection to ground,
modification thereof, it is to be clearly under
an input circuit connected to said high frequency
stood that this description is made only by way
of example and notas a limitation on the scope 45 Aamplifier through the ñrst said input coupling
of my invention as set forth in the objects and
means, a detector connected to the output cou-.
the accompanying claims.
pling means of said high Vfrequency amplifier,
means connecting the output circuit of said detec
tor to the common connection of one of said input
1. Radio receiving apparatus including, in
combination, a high frequency amplifier having 50 coupling means of an amplifying stage, a signal
reproducing device, a 10W-frequency pass filter,
one o-r more relatively high frequency amplifying
and means connecting said signal reproducing
stages, each of said stages including input and
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output direct capacitative coupling' means, com
device to the common connection of an output
coupling means following said one input coupling
common connection and a common condenser 55 means through said 10W-pass filter.
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ARCHIBALD D. SMITH, J‘R.
connecting said common connection :to ground, an
prising a pair of uncoupled inductors having a
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