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Патент USA US2123727

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July 12, 1938.‘
H. E. HOLLMANN
21,123,727
MODULATION CIRCUIT FOR RETARDING FIELD GENERATORS
Filed Oct. 25, 1934
MON/LA T/OA/
P075'N T/ALS
MODULATION '
POTENTIALS
INVENTOR
HANS ERICH' HOLLMANN
ATTO R N EY
Patented July 12, 1938
'
UNITED STATES PATENT OFFICE
2,123,727
MODULATION CIRCUIT FOR RETARDING
FIELD GENERATORS
’
Hans Erich Hollmann, Berlin, Germany, assignor
to Telefunken Gesellschaft fiir Drahtlose Tclc- '
graphie m. b. H., Berlin, Germany, a corpora
tion of Germany
Application October 23, 1934, Serial No. 749,535
In Germany November 3, 1933
5 Claims. (c1..179_171);
It is known, in the prior art, that a generator
connected in av Barkhausen-Kurz type of retarding-?eld circuit arrangement is modulable with
relatively low alternating voltages and that the
5 modulator potential em is superposed upon the retarding electrode potential Eb. While this method
notes the retarding ?eld tube which excites a
Lecher wire ‘system L united with the grid and
the anode in well-known manner. M denotes the
modulation transformer whose winding S1, as
above pointed out, is included in the lead brought 5
to the retarding ?eld electrode so that a- pure
insures satisfactory modulation, it nevertheless alternating voltage em becomes superposed upon
involves the drawback thatthe modulating volt- the biasing voltage Eb of the retarding ?eld elec
age works, upon the internal retarding resistance trode.. In order that the modulation potential em,
10 0f the retarding ?eld generator; in other words, pursuant to the idea underlying this invention, 10
upon the resistance acting between the cathode may also be fed to the grid, a second secondary
and the retarding ?eld electrode. Since the lat- winding S2 of the modulation transformer may be
ter resistance amounts to- about 1000 ohms, this included in the grid lead. Transfer of current
means a severe load for the source of the modula-
15 tion voltage which, in the majority of cases, consists of a transformer. In other words, although
the voltages are inherently low, a considerable
amount of modulation power must be provided.
for the modulation frequency may then be equal
ized and maintained constant by Virtue of the 15
mutual inductance of the two windings S1 and S2,
without any action being brought upon the pri
mary winding.
This drawback is obviated entirely by the presAnother circuit scheme is shown in Fig. 3, in
20 ent invention. By the mere adoption of certain which the modulation potential em is imparted to 20
means and ways in the circuit organization, the grid by way of a suitable condenser C and is
perfectly non-dissipative modulation of a retard- prevented from leaking or draining away to the
ing ?eld generator is obtainable. The invention grid voltage source by the aid of the choke coil D
is based upon the fact that the oscillator tube contained in the grid lead. In this circuit ar
25 of a retarding ?eld generator operates inside the rangement the transfer of current is equalized 25
saturation region, so that the total electron emis- between grid and retarding ?eld electrode by way
sion current is=ig+ib, distributed over the re- of C, and for this reason the bridging condenser
tarding ?eld electrode and the grid, is constant. must be chosen so large that it will still constitute
Consequently, in the state of oscillation, the re- a short-circuit even for the lowest modulation
30 tarding ?eld characteristic ib=f (eb), having an
inverted image pattern, is transferred to the grid
end in the very same manner as in the static characteristics of the retading ?eld tube. For in-
stance, Fig. 1 shows the two statically plotted
35 current characteristics of an oscillating retarding
?eld transmitter, it and 21, being observed as a
function of the biasing retarding ?eld voltage eb.
According to this invention, the modulator voltage cm is impressed not only upon the retarding
40 ?eld electrode, but, at the same time, also upon
vthe grid. This means that operation takes place
not only upon the retarding ?eld characteristic
ib=f (6b), but, at the same time, also on the grid
current characteristic ig=f (8b). In this case it
45 and ig become added, resulting in the constant
saturation current is, and the modulation voltage
em, as a consequence, works upon the pure satura-
tion resistance of the tube.
Fig. 1 shows curves explanatory of the comi0 ponent currents forming the total emission cur-
frequency. Hence, in audio frequency modula- 30
tion a condenser of a few microfarads will be re
quired, whereas for radio frequency modulation,
say with one intermediate carrier frequency, the
capacity of the turning bridge piece B will gen
erally be sui?cient. In this instance, all that will 35
be necessary is the connection of the choke-coil D.
What is claimed is:
1. An oscillation generator comprising an elec
tron discharge device having an anode, cathode
and a grid, means for supplying a positive po- 40
tential to said grid and a less positive potential
to said anode relative to said cathode, whereby
there is obtained pendulum motion of electrons
about said grid, and means for supplying modu
l-ating potentials co-phasally to said anode and 45
grid, the last said means comprising means for
causing a constant saturation electron ?o-w from
said cathode.
2. In a modulation circuit for a retarding ?eld
type generator, an electron discharge tube hav- 50
rent. Figs. 2 and 3 show, schematically, two em-
ing a cathode, an anode and a grid, means for
bodiments of the invention.
impressing a highly positive charge on said grid
A circuit organization adapted to carry the
basic idea of the invention into practice is illus5 trated in Fig. 2. Referring to the same, R de-
'
relative to the charges on said cathode and said
anode respectively, means for impressing simul
taneously upon said grid and upon said anode, 55
2
2,123,727
respectively, modulation voltages which are co
_ phasal and additive in their effect, and means for
maintaining a constant saturation electron ?ow
from said cathode.
3. An oscillation generator comprising an elec
to said cathode, means for maintaining a rela
tron discharge tube having a plate, a cathode
and a grid, means for rendering the charge on
tively small difference of direct current potential
between the cathode and the retarding electrode,
a transformer having a primary winding upon
said grid highly positive with respect to said
which modulation potentials may be impressed,
cathode, means for maintaining a relatively small
di?erence of direct current potential between the
10 cathode and the plate, means for producing a
15
5. An oscillation generator comprising an elec
tron discharge tube having a cathode, a grid and
a retarding electrode, means for maintaining a
highly positive charge on said grid with respect
constant saturation electron flow from said cath
ode, and means for impressing modulation volt
ages co-phasally upon said grid and upon said
plate while facilitating the operation of the next
previously mentioned means.
4. A generator in accordance with claim '3 and
having electrostatic coupling means between the
grid and the plate for the transfer of modulat
ing potentials to said grid, said coupling means
20 having a low impedance to the band of fre
quencies of said modulating potentials.
and two secondary windings, one of said second 10
ary windings being in circuit between the oath
ode and the grid and the other of said secondary
windings being in circuit between the cathode
and the retarding electrode, and a capacitor inter
coupling the grid and the retarding electrode, 15
said transformer‘ in combination with said ca
pacitor constituting means for maintaining a.
constant amplitude of electronic emission from
said cathode while impressing said modulation
potentials co-phasally upon the electrodes of 20
said tube.
HANS ERICH HOLLMANN.
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