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Патент USA US2124191

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'July 19, 1938.
_
M, GEIGER
'
2,124,191
DEMODULATION SYSTEM IN SURERHETERODYNE RECEIVER
Filed Sept. 25, 1936
’
129.1
'Ml/L T/PL/CA 7/0”)
FACTOR 0F 15'
0.6140001!) 70?
11119.2
STAGE 02 zwosr.
6
7
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QVMPl/IWDE
L/M/TEQ
,
INVENTOR
»
MAX_ QEIGER
BY
m
ATTORNEY
Patented July 19, 1938
1
UNITED STATES PATENT OFFICE.
"2,124,191
DEMODULATION SYSTEM IN SUPERHETER
ODYNE RECEIVER
,
Max Geiger, Berlin, Germany, assignor to Tele
funken Gesellschaft fiir vDrahtlose Telegraphic
m. b. IL, Berlin, Germany, a corporation of
Germany
Application September 25, 1936, Serial No. 102,475
In Germany“ October 23, 1935
3 Claims.
' This invention discloses a novel method of and
means for demodulation which may be usefull
particularly for the production of an intermediate
or beat frequency in superheterodyne receiver
sets. rI‘he method according to the invention con
sists in that the frequency to be demodulated (in
coming signal frequency) is mixed in a modula
tion circuit scheme with an auxiliary oscillation
which is obtained from the intermediate fre?
1'19 quency by frequency multiplication.
Figures 1 and 2 of the accompanying drawing
show diagrammatically two modi?cations accord
ing to the invention.
'
_
‘
Referring to Fig. 1' of’ the drawing, the fre
l<5i quency to be “demodulated (signal or incoming
frequency) E-is impressed in Fig. 1 on the control
(01. 250-20)
so that the incoming frequency is conve‘rte'd’into
an intermediate frequency 16 times lower; "
‘
Inthe case of a heterodyne receiver the ad,
vantage of frequency division is that a distinct‘
oscillator is made dispensable. _ This is particu
larly desirable Where ultra-short wave'receivers‘
are dealt with, seeing that the local oscillator
normally required works With a very high fre-‘
quency ‘the stabilization of which is attended with
particularly great difficulties. .A shift in fre 10
quency is transferred to the intermediate "fre
quency, and its effect on the latter in terms?of
percentage is far greater and moreserious; in‘
fact, there is a risk of the intermediate frequency,
in case of'a su?iciently serious drift of the oscill‘ 15
lator Wave-length, falling entirely ‘outside: the‘
range of transmission of the I. F. ampli?er. How
hexode, also known as a pentagrid converter. At
the plate 3 is made available the intermediate or
beat frequency I. F. (which for the time being
ever, by resorting to the method here disclosed
this risk is wholly precluded seeing that no sep
arate oscillator is provided and that the I. F. bears
must be imagined to exist) which is then ampli
?ed in the intermediate-frequency ampli?er 4.
quency.
?ed and/or demodulated, as Well known in the
25 art, and, on the other hand, is impressed upon
the frequency multiplier 5. The frequency from
the output of the latter then serves as the hetero
dyning frequency 0, instead of an oscillation
a ?xed relationship to the incoming signal fre- '
30 oscillator, and is fed to the other control grid 6
of the mixer tube. The I. F. ampli?er 4 and the
frequency multiplier 5 may be of the convential
standard receivers comprising a distinct oscil
lator. In accordance with the relation
1
I. F. —- Em
above laid down, the intermediate frequency I. F.
is changed to
1
types as known in the art, and for that reason are
E1.——1
+V
shown in block form. '
Insuring in the multiplier stage 5 a multiplica
tion 1), then the following relations hold good:
I. F.=E-O
0:01. F.
40 whence the division ratio between frequencies E
and I. F.
.
Another merit worth mentioning is that fre
quency fluctuations of the signal frequency will
make themselves less seriously felt than in
which would have to be produced in a distinct
For instance, if the multiplication is 11:40, it will 35
be noted that the shift of the I. F. will amount
only to
i
41
40
of the shift in the incoming signal frequency.
What may also be mentioned is’that the ar
=1. F._ 1
#5
‘
grid I of. a mixer tube or demodulator 2, say, a
This I. F., on the one hand, is then further ampli
5
‘
Numerical examples are indicated in brackets
in Fig. l. The intermediate frequency is here as
sumed to be 2.5 megacycle's (120 m.) and the same
is raised ?fteen times. The ensuing heterodyne
r frequency of 37.5 megacycles forms with the in
"0 coming signal frequency of 40 megacycles (7.5
meters) the intermediate or beat frequency of 2.5
megacycles. The dividing ratio is
t
1
rangement here disclosed will operate only if the
multiplication is so chosen that the heterodyning
frequency is lower than the incoming or signal 45
frequency, lest the arrangement becomes un
stable. This condition will be understood most
clearly by assuming, for instance, that the I. F.
grows a little. In that case also the heterodyning
frequency increases and as a result by Way of the 50
mixer tube the I. F. becomes smaller again so that
a counter-action to the assumed increase takes
place. However, this effect will arise only where
the incoming frequency is higher than the hetero
dyning frequency, otherwise a higher heterodyn 55
2
2,124,191
ing frequency would in turn result in a higher
I. F., etc.
The building-up of oscillations in the system
from its quiescent state to the oscillatory state
C21 occurs, in the presence of the incoming frequency
E, just as in the case of a regenerative transmit
ter tube as a result of and in response to small
accidental changes in the tube current which
are always present. A system wherein occurs'
10 the building up of oscillations such as here re
megacycles, this frequency is chosen in this case
as the I. F.
Fig. 2 differs from Fig. 1 by the insertion of an
amplitude limiter ‘l. The purpose of ‘the same
is to prevent frequency 0 from being modulated
in case of reception of a modulated oscillation,
for a modulation would occasion distortions in
the mixing process.
It may ?nally be mentioned that the invention
is useful not only for receiving sets, but generally 1O
ferred to is shown and described in the U. S.
for frequency division work.
patent to O’Brien No. 2,039,923.
What I claim is:
1. In the reception of signals by the super
heterodyne principle, the method of demodula
tion which consists in collecting the received sig
nal frequency, mixing the received signal fre
quency with a second frequency which results
in an intermediate frequency, and deriving said
If the arrangement is to be capable of receiv
ing different frequencies E without a change of
the I. F., the arrangement may be rendered use
ful by that the multiplication u of multiplier stage
5, when tuning to another station, is so altered
that always together with the prevailing signal
frequency E the same or a ?xed I. F. is pro
20 duced. If the stage 5 consists of a tube with
tuned plate circuit (Whose rotary condenser may
be coupled with the condenser of the receiving
circuit so as to obtain uni-control) and if the
same is operated with a markedly negatively
biased grid, then the quantity 1? will always be a
wholevnumber. In the light of the last equation
above indicated, I. F. will then be always an
integral fraction of frequency E. This relation
prevents any desired signal frequency E from be
ing received. However, it is possible to pick up
1
second frequency by frequency multiplication of
a portion of said intermediate frequency.
2,. A demodulation circuit arrangement com
prising a vacuum tube provided with a cathode,
anode, and a plurality of interposed grills, a
signal input circuit connected to one of the grids,
an intermediate frequency ampli?er having an
output circuit fed from the anode circuit of said
tube, and a frequency multiplier coupled to the
output circuit of the intermediate frequency
ampli?er, and a connection from the output cir
cuit of the frequency multiplier to one of the 30
those frequencies which are a multiple of the
I. F. This fact is particularly valuable and im
interposed grids other than the signal grid.
portant in connection with television reception.
Television stations are to operate with fre
amplitude limiter is interposed between the in
termediate frequency ampli?er and the frequency
quencies of 40, 42.5, 45, etc., megacycles. Inas
multiplier.
much as these frequencies are multiples of 2.5
3. A circuit according to claim 2 wherein an
MAX GEIGER.
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