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Патент USA US2115875

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May 3, 1938.
2,1 15,875
W, VAN B. ROBERTS
REGENERATIVE DETECTOR‘
Filed Oct. 30, ‘1936
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INVENTOR
WALTER VAN B. ROBERTS
BY
ATTORN EY
Patented May 3, 1938
2,115,875
UNITED STATES
PATENT OFFICE I
2,115,875
REGENERATIVE DETECTOR
Walter van B. Roberts, Princeton, N. J ., assignor
to Radio Corporation of America, a. corpora
tion of Delaware
Application October 30, 1936, Serial No. 108,426
2 Claims.
My present invention relates to a regenerative
detector, and more particularly to a new and
improved type of regenerative detector circuit
wherein audio ampli?cation is simultaneously
.51 secured.
In the prior art the regenerative detector is
very well known, and it usually comprises a grid
leak detector of the triode type wherein the plate
circuit is regeneratively coupled to the tuned
input circuit. It is known that such a regenera
tive detector circuit suffers the disadvantage that
a large radio frequency current ?ows in the
plate circuit when strong signals are received.
By virtue of the latter overloading occurs, since
1 Ql the plate circuit current variation that must be
handled by the tube is equal to the sum of the
audio frequency and radio frequency amplitudes.
This operating disadvantage has discouraged the
use of the regenerative detector circuit in situa
20 tions where it may well be employed. It is
pointed out that the recent trend has been to
(Cl. 250+27)
to provide a regenerative detector circuit which
is not only reliable in operation, but is economi
cally manufactured and assembled in radio
receivers.
The novel features which I believe to be char
acteristic of my invention are set forth in par
ticularity in the appended claims; the invention
itself, however, as to both its organization and
method of operation will best be understood by
reference to the following description taken in 10
connection with the drawing in which I have
indicated diagrammatically several circuit or
ganizations whereby my invention may be carried
into e?ect.
15
In the drawing:
Fig. 1 shows a regenerative detector circuit
embodying one form of the invention, and
Fig. 2 shows a detector circuit employing a_
modi?cation of the invention.
Referring now to the accompanying drawing, 20
wherein like reference characters in the different
ward use of a separate diode detector whose audio
?gures designate similar circuit elements, the
frequency output is ?ltered free of radio fre
quency components and impressed upon the grid
25 of a tube used solely for audio frequency ampli
?cation.
numeral I denotes an electron discharge tube
which may be of the well known 55 or 85 type.
Accordingly. it may be stated that it is one
of the main objects of my present invention to
This type of tube essentially comprises electrodes 25
arranged to provide a diode section and an inde
pendent ampli?er section. Brie?y, the tube com
such regeneration being secured without appre
prises a cathode 2, a diode anode 3 disposed
adjacent a portion of the cathode 2 so as to
receive electrons therefrom. The diode anode 3
and plate 5 are arranged to receive independent
stream of electrons from the common cathode 2.
Those skilled in the art will readily realize that
when using a tube of the duo-diode triode type,
the two diode anodes will be strapped together, 35
and thus furnish an effective single anode for
ciably hastening the network overloading.
the diode section.
provide a regenerative detector network where
30 in the tube employed in the network comprises
a diode section and an audio ampli?er section;
the audio ampli?er section being utilized for radio
frequency regeneration by regenerative feedback
from the output of the audio section to the tuned
35 input circuit connected to the diode section, and
Another important object of the invention may
be stated to reside in the provision of a detector
4“ network which comprises a tube constructed to
Furthermore, the ampli?er
section of the tube may be of the screen grid,
or pentode, type as in the 85 type tube, if desired.
The signal input circuit 6 has its coil 1 mag 40
furnish a diode section and an ampli?er sec
netically coupled to the source of signal current,
tion, a signal input circuit being connected to
the diode section to provide a diode detector
by the latter functions as an audio ampli?er,
and the condenser 8 tunes the input circuit 6
at the desired signal frequency. If the receiving
system is of the superheterodyne type, then the
source of signal energy coupled to input circuit 6 45
will be the output of the I. F. ampli?er. Since
superheterodyne receivers are very well known to
the plate circuit of the ampli?er being relatively
those skilled in the art it is not believed neces
tightly coupled to the detector input circuit, and
sary to describe such a system in detail, except
50
to point out that the input circuit 6 would be
tuned to the operating I. F., and the condenser 8
would be of ?xed value. If the receiving system
is of the tuned radio frequency type, then one,
or more, tunable radio frequency ampli?ers pre
cede the input circuit 6, and the variable con
denser 8 would have its rotors arranged for uni
control adjustment with the rotors of the variable
condensers used in the preceding ampli?ers.
The diode load resistor 9 is connected between 60
circuit, the audio frequency component of the
45 detected signal current being impressed upon
the control grid of the ampli?er section where
50 a relatively loose coupling being provided be
tween the ampli?er grid and the diode detector
input circuit whereby the ampli?er functions to
provide regeneration of the signal current with
out carrying sufficient radio current to appre
551 ciably
hasten overloading of the ampli?er output
circuit.
Still other objects of the invention are to im
prove generally the e?iciency and utility of re
60 generative detector circuits, and more especially
. 2
2,115,875
the low alternating potential side of input circuit
5 and the grounded cathode, the by-pass con
denser lll being shunted across resistor 9.
The
audio frequency component of detected signal
current is impressed upon the control grid 4 by
connecting the latter to an adjustable tap II.
The tap H is slidable along load resistor 9, and'
is connected to control grid 4 through a path
which includes condenser l2 and the coil 13. The
10 latter is reactively coupled. to input coil 7, and
the arrow through coils ‘I and I3 denotes ad
justability of the reactive coupling between the
two coils. The junction of coil I3 and condenser
l 2 is connected to ground through resistor l4, and
15 the function of this resistor is to provide a de?
nite direct current operating potential for grid 4.
The plate 5 of tube I is connected to the posi
tive terminal of a source of direct current po
tential, which source is not shown, through apath
which includes the feedback coil l5 and the head
phones IG. Coil l5 and coil '1 are reactively cou
pled. If desired, the headphones l6 may be re
placed by any other type of reproducer, such as a
loudspeaker, and the audio output of the plate
25 circuit of tube I may be ampli?ed in one, or
more stages of audio ampli?cation.
In the circuit shown in Fig. 1, a relatively
strong feedback coupling is provided between the
plate circuit of tube I and the tuned input circuit
30 6. A variable coupling of the correct phase for
regeneration is then provided between input cir
cuit 6 and control grid 4. Since the feedback
coupling is much tighter than customary in re
generative circuits heretofore used, it is only
35 necessary to impress a small fraction of the radio
frequency voltage across coil 1 upon the grid 4
to obtain su?icient regeneration, or even oscilla
tion. Since the radio frequency voltage im
pressed upon grid 4 is very small there will be
40 only a very small radio frequency current in the
radio frequency choke coil 30 to the control grid
4. The grid leak resistor 3| is connected in se
ries between the control grid 4 and the usual grid
bias resistor 40. It will be understood that the
voltage drop across resistor 40, the latter being
shunted by the by-pass condenser 4|, provides
the normal grid bias for control grid 4. The
anode side of load resistor 9 is connected to the
midpoint of input coil 1, and an automatic volume
control connection (AVC) is shown connected to 10
the anode side of resistor 9. The resistor-con
denser network 50 ?lters the radio frequency
components from the AVG’ bias, and, as is well
known, the latter bias is applied to one, or more,
radio frequency ampli?ers for reducing the gain 15
of the ampli?ers as the signal amplitude in
creases thereby to maintain the‘ carrier ampli
tude at the input circuit 6 substantially uniform
over a relatively wide range of signal variation at
the signal collector of the receiving system.
While I have indicated and described several
systems for carrying my invention into effect, it
will be apparent to one skilled in the art that my
invention is by no means limited to the particular
organizations shown and described, but that
many modi?cations may be made without de
parting from the scope of my invention, as set
forth in the appended claims.
What I claim is:
1. In combination, in a detector network, an 80
electron discharge tube provided with a diode
section and an ampli?er section, a tuned signal
input circuit connected to the diode section and
including means for rendering the diode capable
of detecting signals, means for impressing the
audio component of detected signals upon the
control grid of the ampli?er section, an audio
utilization means in the plate circuit of the am
pli?er section, means tightly coupling the plate
circuit of the ampli?er section with the detector
plate circuit, and accordingly this will not bring
input circuit to provide strong regenerative feed
about overloading appreciably sooner than if re
generation were not used at all. For purposes of
back thereto, and a reactive coupling between the
control grid of the ampli?er section and said de
illustration, it is pointed outthat the coupling
tector input circuit whereby the ampli?er section
45 between coils l5 and 1 may be one such as would
functions to regenerate signal currents, said re 45
ordinarily be employed for ampli?cation purposes
where a plate circuit, or primary coil, is coupled
to a tuned secondary circuit. The voltage step
tight coupling and to an extent such that only a
very small radio frequency current flows in said
down between coils l and l3 is variable over a
plate circuit.
50 range‘including a step down that just compen
sates for the ampli?cation action, which particu
lar step down is the critical value for sustained
oscillations.
In Fig. 2 there is shown an alternative circuit
55 arrangement employing the same method of op
eration, but having its regeneration controlled by
a variable capacity instead of a variable mutual
inductance. In this ?gure any radio frequency
component in the plate circuit is forced by choke
60 coil 20 to flow through condenser 2| back into
the tuned input circuit 6. The control grid 4 is
connected to a point 22 which is at zero radio
frequency potential when the adjustable con
denser 23 is suitably adjusted. .The tuning con
65 denser 8 is connected in shunt to the adjustable
condenser 23 and the ?xed condenser 24, both of
the latter condensers being connected in series.
A slight variation of condenser 23 will impress a
small radio frequency potential upon the control
70 grid 4 and produce regeneration.
The diode detector has its audio frequency out
put connected through the condenser l2 and
active coupling being substantially less than said
2. In combination, in a detector network, an
electron discharge tube provided with a diode
section and an ampli?er section, a tuned signal
input circuit connected to the diode section and
including means for rendering the diode capable
of detecting signals, means for impressing the
audio component of detected signals upon the
control grid of the ampli?er section, an audio
utilization means in the plate circuit of the am
pli?er section, means tightly coupling the plate
circuit of the ampli?er section with the detector
input circuit to provide strong regenerative feed
back, a reactive coupling between the control grid
of the ampli?er section and said detector input
circuit whereby the ampli?er section functions
to regenerate signal currents, and said coupling
between the plate circuit of the ampli?er section
and the detector tuned input circuit being rela
tively stronger than said other coupling to the
ampli?er control grid, the said reactive coupling
being sufficiently small to prevent overloading of
the said plate circuit by radio frequency currents.
WALTER VAN B. ROBERTS.
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