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Патент USA US2137629

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Nov. 22,‘ 1938.
E. SCHULZE-HERRINGEN
2,137,629
METHOD OF CONTROLLING HIGH FREQUENCY TRANSMITTERS
5 Sheets-Sheet -l
Filed May 2, 1955
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E. SCHULZE-HERRINGEN
2,137,629
METHOD OF ‘CONTROLLING HIGH FREQUENCY TRANSMITTERS
Filed Maya, 1935
5 Sheets-Sheet_2
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Nov. 22, 1938.
E. SCHULZE-HERRINGEN
2,137,629
METHOD OF CONTROLLING HIGH FREQUENCY TRANSMITTERS
Filed May 2, 1935
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5 Sheets-Sheet 3
Nov. 22, 1938.
é. SCHULZVE-HERRINGEN 1
2,137,629
METHOD OF CONTROLLING HIGH FREQUENCY TRANSMITTERS
Filed May 2, 1955
5 Sheets-Sheet 4
Nov. 22, 1938.
E. SCHULZE-HERRINGEN
2,137,629 '
METHODOF CONTROLLING HIGH FREQUENCY TRANSMITTERS
Filed May 2, 1955
5‘ Sheets-Sheet 5
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Patented Nov. 22, 1938
2,137.629
UNITED STATES PATENT OFFI€E
2,137,629
METHOD’ OF CONTROLLING HIGH FRE
QUENCY TRAN SMITTERS
Erich Schulze-Herringen, Braunschweig, Ger
many, assignor to C. Lorenz Aktiengesellschaft,
Berlin-Tempelhof, Germany, a company
Application May 2, 1935, Serial No. 19,469
In Germany May 2, 1934
3 Claims.
(Cl. 179—171)
The invention has for its object to improve
with the usual transmitters because the voltage
the ef?ciency of high frequency transmitters, and
is in general utilized inei?ciently, for the greatest
particularly of radio telephonic transmitters. In
this respect it has been proposed to employ a
5 method which is based on the following principle.
modulation amplitudes occur only for a short in
terval of time. The greatest e?iciency is only at
tained if the tube is utilized completely. There
fore according to the invention the anode poten
tial for the respective modulation amplitude is so
From the modulation currents a continuous
current is derived that acts to displace the work
ing point in dependency upon the modulation
amplitudaeas may be seen for instance from the
In this Way it is at
tained that the carrier amplitude is essentially
just so great as to be completely utilized for the
7.4 0 British Patent 363,480.
modulation, that is to say, care is taken that
there shall be no overmodulation. There are
15 known also several improvements upon this
selected that the tube is just completely utilized.
If the modulation amplitude increases then the
anode potential is likewise increased and thus a 10
characteristic curve of higher position is selected,
this curve being likewise completely utilized.
It is essential that the operating voltage Us. be
greater than the threshold voltage Us. If
15
Ua=1OUS then the voltage utilization
method which have for their object to avoid
distortions to occur in receivers operating with
non-linear recti?cation. By this method the
eiiioiency is considerably increased. The inven—
With a current utilization
This problem is becoming more and more im
portant as the energy requirement of a high
located in the zero‘ point of the characteristic
20 tion however is intended to create a method
which shall ensure an increase in e?iciency still
greater than is the case with the known method.
25 power transmitter and all its auxiliary devices is
considerable, so that by improving the ef?ciency
the current expenses can be diminished consid
2
U0,
20
adapted for the purpose if the working point is
and if h:90%, the efficiency is 17=72%. This 25
efficiency is derived by means of the well known
formula
erably.
The invention will be understood from the fol
e: O lowing description and be particularly pointed
out in the appended claims, reference being had
to the accompanying drawings in which
Figs. 1 to 6 are diagrams relating to the opera
tion of arrangements constructed according to
3in the invention.
Fig. 7 is a diagrammatic repre
sentation of an embodiment of the invention,
Figs. 8 to 11 are diagrams relating to the opera
tion of a modi?cation of the arrangement shown
in Fig. '7, Fig. 12 is a diagrammatic representa
4 O tion of this modi?cation.
In accordance with the invention the anode
potential and grid bias are dependent upon the
modulation amplitude and are simultaneously
controlled. The diiierence over the known meth
45 od is that the anode potential and grid bias are
controlled simultaneously, from which there re
sult the advantages or physical di?erences which
as explained hereafter require consideration in
connection with the two methods. With the
5 O aforesaid known method either the anode poten
tial or the grid bias is controlled in dependency
upon the modulation amplitude, so that the two
voltages are not controlled simultaneously.
The invention is based on the consideration
55 that the ef?ciency of the valve tubes is very bad
wherein J represents the ratio between the anode
alternating current and the anode direct current
and h the ratio between the anode alternating
Voltage and the anode direct voltage. This for
mula may be found in vol. II of the book “Elek
tronenrohren” by Barkhausen, page 117. In the 35
above formula Ja represents the anode alternat
ing current and Ia the corresponding anode di
rect current. This high e?iciency is only ob
tained by locating the working point in the zero
point of the characteristic and by arranging for
a complete utilization of the valve characteristic,
as shown in Fig. 1. In this event the transmitter
will be on the point of operating in a state of
overtension. In the case of modulated high fre
quency, however, in order to ensure an eiiiciency 45
of 72% the tube cannot be utilized completely
with the carrier wave in its state of rest, as in
the case of a complete utilization thereof the
amplitudes when modulated will vary between
zero and double the carrier amplitude. For this
reason the carrier while in its state of rest, i. e.
during the periods of no modulation, should only
be utilized to a degree which corresponds to the
middle of the characteristic, as shown in Fig. 2.
Hereby however the voltage utilization h de 55
2
2,137,629
creases by half so as to amount to 45%, and
hence also the efficiency is diminished from 72%
down to 36%. If now the carrier is modulated,
and if it is so for the limiting case (highest
modulation amplitude) with m=1, wherein m
represents the modulating degree, then there re
sults the representation of Fig. 3. In this case
the current utilization remains approximately
the same with respect to each point. The volt
age utilization however is varied, and it is so
between zero and the full value (h=0 to 90%).
The input of continuous anode current remains
the same, but the alternating current power is
changed; it will be in the case of m=1 equal to
transmitter the working point is in most cases
located in the zero point of the characteristic
(point I, characteristic A). If the anode poten
tial is made less by half then the characteristic
B is worked upon. The working point then is no
more located in the zero point II of the charac
teristic B but is located with respect to this char
acteristic B in the negative portion, namely in
point I. The working point for characteristic B
has thus been displaced in the negative direction
and by a distance DAUa, where D is the “dumb
griff” the active alternating control voltage for
characteristic B having consequently decreased
by the same amount. The carrier current is thus
decreased at its peaks from the value a. down to
b, as will be seen from Fig. 5. In order now to
(the at rest value of the power being supposed to
be equal to 1). The power output thus increases
20 by half, namely from 1 to 1,5 and the efficiency
of the tube from 36% to
obtain with variable continuous anode potential
the same carrier current as in the case of con
stant anode potential, this displacement of the
working point, caused by the anode reaction, is 20
according to the invention compensated by in
fluencing the grid bias. It must be attained
that with each magnitude of the continuous anode
25 The utilization is however great at rarely occur
ring peaks only. On the average it only amounts
to values of 10 to 15%. With telephonic trans~
mitters therefore the average efficiency of the
terminal tubes is only a little greater than 36%.
As regards different modulation degrees it will
30
be seen from Fig. 4 that only with the complete
utilization m=1 the complete voltage utilization
h:90% is attained at the greatest peaks, whilst
if m=0 this voltage utilization has the uniform
35 value h=45%. For all intermediate values the
peak values relating to a de?nite modulation de
gree are below h=90%.
In order now to improve the potential utiliza
tion the continuous anode potential Ua. is, accord
40 ing to the invention, so varied in the rhythm of
the variations of the modulation degree that the
peaks of the high frequency amplitudes have con
tinuously a voltage utilization h=90%. In the
following consideration the durchgriff of the tube
45 is assumed to be equal to zero. This word “durch
griff” is a familiar German term meaning the
throughgrip of the plate of the tube on the elec
trons between the grids and the cathode which
may be expressed as the reciprocal of the ampli
50 ?cation factor, namely, —1- In order to obtain for
all modulation degrees a voltage utilization of
90% at the peaks the continuous anode potential
must be varied between the values 0.5 and 1 Ua.
55 Then, if m=0, that is if the carrier is in its state
of rest, an efficiency 17=72% (h=90%, (i=1.6) is
obtained. If m=1 the e?‘iciency then will be
n=54%. With the novel method the ef?ciency
of the terminal tube assumes values which are
60 between 72% and 5Li%_. whereas in the case of
the customary method with a constant anode
potential the ef?ciency varies between 36% and
54% with increasing modulation. The average
efficiency and thus the saving over the normal
65 circuit arrangement depends upon the average
variation ratio of the modulation.
In the foregoing the durchgriff is assumed to
be equal to zero in theoretical relation in order
that the anode reaction may be selected; such
70 is not the case however in practice. If the anode
reaction is taken into consideration then by vary
ing the continuous anode potential the following
results: A number of characteristic curves, Fig. 5,
is obtained with respect to different continuous
75 anode potentials.
With the normal telephonic
potential the working point for the respective
characteristic is located in the zero point of this 25
characteristic, as for instance in point II, Fig. 5,
if half the continuous anode potential is dealt
with. Therefore the continuous gridpotential is
so regulated that with respect to the at rest
value of the carrier the working point is located
the zero point of the characteristic for half
the normal continuous anode potential. If the
transmitter is now modulated then with increas
ing anode potential the grid bias is increased
towards the negative side, and this is done when 35
ever the anode potential Ua is increased by the
value DAUa. 'By this means it is ensured that the
carrier value of the high frequency will always be
of the same constant magnitude in the antenna,
as is the case also with the customary transmit
ters operating with constant anode potential (Fig.
6).
In Fig. '7 the terminal stage of the high fre
quency transmitter is designated E and the high
frequency source together with the prestages of 45
the transmitter designated St. The modulating
device M, which consists of a microphone and an
ampli?er, acts to control the anode potential of
recti?er G as well as the grid bias of the terminal
stage. The anode recti?er is fed by an alternating
current network N. The continuous anode po
so
tential is fed in a well known manner from the
recti?er G over a ?lter circuit S or va high fre
quency choke H to the terminal stage E. The
anode feeding means of the control transmitter 55
St or of the prestages are not shown as they are
immaterial to the invention. The modulating de
vice M is arranged to influence on the one hand
a grid control device A and on the other hand a
recti?er B.
By the grid control device A the 60
voltage delivery of the grid controlled recti?er G
is in?uenced in a well known maner by displacing
the ignition point. Any of the known arrange
ments for controlling recti?ers of this kind may
be employed here. It is possible also to use in 65
stead of the grid controlled recti?er another
source of electromotive force, such as a machine,
i. e. a source which is regulable. The modulation
frequencies are however on the other hand recti
?ed also by the rectifier B and act to influence 70
over a ?lter circuit K the grid bias of the terminal
tube E.
The modulation of the high frequency carrier
may be effected in any well-known manner, either
in the terminal stage E or in the prestage stage 75
2,137,629
St, the means and method employed vfor ‘modula
tion being independent of the essential features
of the present invention. Thus "the modulation
may be performed, for example, vby applying to
the grid circuit or anode circuit of the vacuum
tube E, or to the grid circuit or anodecircuit of
a tube in the prestage St, the modulation volt
ages from device M in well-known manner.
The power for controlling the anode recti?er G
10 and the grid of the terminal stage is small com
pared to the power saved. The saving of con
tinuous current energy depends ‘upon the ratio
be varied from zero‘up to the full value 1 but
this variation canlonly be accomplished in start;
ing from acer'tain at rest value, such as 0.2 or
‘0.4. This at rest value depends upon the used
tubes as the characteristic curves worked upon
'must all run parallel' with each other. In Fig.
10 an ‘example of amplitude variations is shown
which are produced for instance by speech and
‘correspond to the curve of the continuous anode
voltage with an at rest value 0.3. The continuous 10
grid voltage is controlled in the same shape and
magnitude as is shown in the foregoing with re
between the variations occurring in the modula
spect ‘to the high frequency ampli?cation. For
tion. This ratio is very small and is, as has been
the improvement of the e?iciency the same applies
as for the high frequency ampli?cation.
In reality the characteristics of push-pull am
pli?ers are not so ideal as shown in Fig. 8 but have
for ‘instance the shape represented in Fig. 11.
Such shapes of the characteristic are able in the
case of small control amplitudes to cause'eifective 20
distortions with respect to loudness ratios and
sound. In addition, such aB-ampli?er is in the
115 shown by recent experiments, approximately
0:02, including a great factor of safety. With
this value a‘ and a variation of the anode poten
tial from 0.5 Ua to l Ua a saving in continuous
current input of about 40% is attained. Conse
quently the efficiency of the transmitter tube is
increased to an average value of 60% whereas
with the customary transmitter it is not much
greater than 36%. If for reasons due to modula
'tion the anode potential should not be decreased
to such degree then with the same 0' of the
case ‘of small control amplitudes very sensitive
over variations of the continuous anode voltage
magnitude 0.2 and a voltage variation between
0.6 and l Ua saving in continuouscurrent input
and grid voltage, as then the Working point in 25'
the lower portion of the characteristic is liable
to ‘be easily displaced into the negative part of
of about 331/3% is effected, ,which corresponds
the characteristic so that small control ampli
to an average e?i'ciencyof the tube of about 54%.
30 The savings possible due to the invention are thus
considerable.
The efficiency may still further be improved by
combining in accordance with a further step of
the invention the method just described with the
35 method mentioned herebefore in the opening
statement, i. e. the method by which the working
point is displaced in dependency upon the modu
lation amplitude. The control device must then
be such that the working point is displaced, that
40 is to say, the grid voltage control ‘device, whose
operation has been explained with reference to
Fig. 5, is to be omitted. By this means the car
rier becomes smaller in the case of the anode po
tential decreasing. One could arrange for ‘hav
45 ing a predetermined at rest value of the ‘carrier
with respect to a predetermined durchgriff D.
Since however in most cases the durchgriff is of
a de?nite value with respect to each such carrier
value, an additional grid control of the well
50 known kind may be used here.
It is further proposed by the invention to use
the novel method with voice frequency ampli?ers
operating as so-called B-ampli?ers in push-pull
arrangement.
55
:3
The ideal characteristic of such a B-ampli?er
in push-pull connection has the shape represented
in Fig. 8. The slope of this characteristic then
is a straight line, as will be seen from Fig. 9.
With respect to a half-wave of the control fre
60 quency the energy conditions may be considered
as follows:
The ef?ciency with a complete utilization of
the characteristic is 11=72%, since h=90% and
j=1.6, as shown herebefore regarding the con
65 trol by high frequency.
With the alternating
grid potential decreasing, the efficiency likewise
decreases in linear relation with the continuous
modulation current. In a like manner to high
frequency ampli?ers the voltage utilization in the
70 case of B-ampli?ers for voice frequencies may, as
regards the small values of the voice frequency
control voltage be increased again by varying the
continuous anode voltage and the continuous grid
voltage in the rhythm of the average amplitude
75 variations. The continuous anode voltage cannot
tudes will not be ampli?ed at all. The active al
ternating grid voltage Ust is formed by the dif 30
ference Ust=DUa-—-Ug, where D is the “durch
griff” of the tube, Ua is the operating plate voltage
and Ug is the grid potential. If Ug becomes small
then Ust depends very much upon DU‘; and thus
upon the continuous anode voltage Ua.
Due to the proposed method of controlling the
continuous anode voltage and grid bias in order
to improve the voltage utilization, ‘the displace
ment of the active working point resulting from
a variation of the anode voltage will in the case
of small control amplitudes no longer cause a
failure of an ampli?cation. This will be seen from
the foregoing formula Ust=DUa—Ug as now a de
crease of Ug does not entail a decrease of Ua and
thus of DUa. The sensitivity of the B-ampli?er 45
‘connection with respect to anode voltage varia
tions is approximately the same whether the con
trol amplitudes at the grid of the push-pull con
nection be great or small.
In order now to diminish the distortions of 50
loudness ratios and sound, caused by the curva
ture of the lower part of the characteristic, ac
cording to a further step of the invention the
act of controlling the continuous grid voltage in
order to realize the DUa compensation in accord 55
ance with a non-linear form, is so accomplished
as to counteract the curvature of the character
istic. Owing to this mode of regulating the grid
bias, each control amplitude of the voice fre
quency has practically another working point on 60
the curvature of the respective characteristic.
This mode of eliminating distortions has the ad
vantage that the elimination can be effected in
the B-ampli?er itself or that owing to such special
circuit arrangement a substantial distortion can 65
not occur.
The elimination of distortions in such a B
ampli?er for voice frequency may in accordance
with a still further step of the invention be ef
fected at the grid by a non-linear displacement of 70
the working point without the continuous anode
voltage being varied. The grid bias is controlled
here within a smaller range since it is not neces
sary to compensate DUa but to provide for the 75
4
2,137,629
small and large control amplitudes being as far
as possible free of distortions.
This will be understood from Fig. 12. The
push-pull tubes are designated R. The voice fre
quencies are in a well known manner led over
10
15
20
25
the transformer T1 and on the grid side directly
to the push-pull tubes and are also conducted
through an ampli?er V to the push-pull arrange
ment, the ampli?er V belonging to the novel con
trol arrangement by which the grid voltage as
well as the anode voltage are in?uenced. N is
a non-linear ampli?er which according to the
foregoing serves for compensating the curvature
of the characteristics. Connected to the output
of the non-linear ampli?er is a recti?er G1 which
through a smoothing means A1, such as a ?lter
circuit, acts to control the grid bias. In the out
put of V another recti?er G2 is disposed by which
the anode voltage is controlled. In the case rep
resented it is intended to derive the anode voltage
from the alternating current network by means
of a grid control recti?er GL. In this case the
grid of GL is controlled by the recti?er G2. The
controlled anode voltage is then led over a
smoothing link A2 of the anode circuit to the
transmitter will be constant magnitude for vary
ing values of anode voltage.
2. An arrangement for controlling a high fre
quency transmitter employing a vacuum tube
terminal stage for delivering a high frequency
carrier modulated in accordance with modulating
frequencies, said vacuum tube stage including
cathode, grid and anode so as to maintain the
high frequency carrier constant, comprising
means including a grid controlled recti?er for 10
supplying direct current potential to the anode of
the vacuum tube terminal stage, a source of mod
ulating frequencies, a control recti?er for recti
fying modulating frequencies from said source,
means for impressing the direct current potentials 15
resulting from such recti?cation upon the grid
of the grid control recti?er, and means including
a recti?er for rectifying modulating frequencies
from said source and impressing the resulting
direct current potentials upon the grid of the 20
terminal stage in such manner as to increase
the negative potential on said grid when the di
rect current potential supplied to said anode is
increased.
'
3. An arrangement for controlling a high fre
push-pull arrangement.
quency transmitter employing a vacuum tube
What is claimed is:
l. The method of controlling a high frequency
transmitter employing a vacuum tube terminal
terminal stage for delivering a high frequency
carrier modulated in accordance with modulating
30 stage for delivering a high frequency carrier
modulated in accordance: with modulating fre
quencies, said vacuum tube stake including cath
ode, grid and anode, means for supplying direct
current potential to the anode‘ and means for sup35 plying a biasing potential to the gride, so as to
maintain the high frequency carrier constant,
said method comprising varying the direct cur
‘frequencies, said 'vacuum tube stage including
cathode, grid and anode so as to maintain the 30
high frequency carrier constant, comprising a
source of modulating frequencies, two rectifying
arrangements for rectifying modulating fre
quencies from said source, means for varying the
anode potential of the vacuum tube terminal 35
stage in accordance with the varying direct cur
rent potentials resulting from such recti?cation
rent potential of the anode in accordance with
the average amplitude variations of the modu
by one of said rectifying arrangements, and means
lating frequencies, displacing the working point
stage in accordance with the varying direct cur
of the said terminal stage by the anode reaction
resulting from such varying of the anode poten
tial, and simultaneously varying the biasing po
tential of the grid in accordance with the average
45 amplitude variations of the modulating frequen
rent potentials produced by the other of said recti
40
cies so as to compensate for the displacement of
said working point whereby the output of the
25
for varying the grid potential of the terminal
40
fying arrangements in such manner as to increase
the negative potential on said grid when the
direct current potential supplied to said anode is
increased.
45
ERICI-I SCHULZE-HERRINGEN.
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