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Патент USA US2122748

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July 5, 1938.
Filed Feb. 12, 1956
F119. 2
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.5?“ 5 Luv-“DY
Patented July 5, 1938
Hans Mayer, Berlin-Charlottenburg, Germany,
assignor to Siemens & Halske, Aktiengesell
schaft, Berlin, Germany, ‘a corporation of
Application February 12, 1936, Serial No. 63,590
In Germany February 2'7, 1935
2 Claims.
The invention relates to a four-pole device hav
ing non-linear properties. Such four-pole de
vices are necessary for many purposes such as for
instance for the limitation of amplitudes, for
the suppression of small amplitudes, or for the
non-linear reduction of distortion. Such four
pole devices can also be utilized for purposes of
blocking or control when using non-linear re
sistors whose values can be controlled by means
of a direct potential.
If such a four-pole device is to be inserted in
such a manner in the transmission system that
desirable amplitude ranges will be transmitted
while undesirable ranges are suppressed, it will
15 be of particular advantage .for many purposes
if the normal impedance of such four-pole device
is independent of the amplitude. The invention
relates to amplitude ?lters having a constant ap
parent resistance independent of the amplitude,
20 at least within a de?nite amplitudinal range.
Out of the theory of the linear networks a
group of four-pole devices has become known in
whichythe wave resistance Z is given by the
values may consist of known non-linear resistors,
preferably dry recti?ers or hot conductors.
Combinations of two respective dry recti?ers with
opposite current ?ow and connected in parallel
or in series were found to be especially suited.
The four-pole devices constructed in accord
ance with the invention are preferably of the
type of bridge ?lters in whose branches or di
agonals the elements having reciprocal resistance
values are inserted. It is obviously within the
scope of the present invention to utilize in place
of bridge ?lters, all equivalent four-pole devices
such as for instance bridged T-cil'cuits, cross
?les or the like.
In accordance with a further feature of the in 15
vention, in order to obtain the desired reciprocity
of the resistors, the non-linear resistors are com
bined with linear resistors. Suited for this pur
pose is also the use of non-linear resistors having
different properties, or the use of special biasing 20'
potentials. If the four-pole devices are to have
a desired dependence upon frequency, the non
linear resistors are to be combined with resistors
depending upon corresponding frequencies.
Z = 1/Z1-Z2
and which has a real and constant value in the
entire frequency range if reciprocal impedance
values are chosen for the resistors Z1 and Z2.
30 Known examples of such four-pole devices are
represented by cross ?les, bridge ?les, bridged
T-circuits and the like. A bridge-?le network is
of the type shown in Fig. 5; while a bridged T
?le network is of the type shown in Fig. 6. A
cross-?le network is a four-pole device containing
crosswise connected impedances. When consid
ering the two input, and the two output, termi
nals of a four-pole device, the crosswise im
pedances are switched in between the upper in
40 put terminal and the lower output terminal on
the one hand, and between the lower input
terminal and the upper output terminal on the
other hand.
In accordance with the invention, an amplitude
45 ?lter with constant wave resistance is obtained
by replacing in an equivalent manner the re
sistors Z1 and Z2 by resistances having reciprocal
resistance values with respect to the amplitude.
In this way it is accomplished that the transmis
50 sion ratio varies with the amplitude, while the
wave resistance however, remains wholly, or ap
proximately constant. Through the selection of
a suitable end resistor it will be possible also to
obtain a constant apparent resistance.
(Cl. 178-44)
The elements having reciprocal resistance
By suitably dimensioning the non-linear re- >
sistors it’ can be accomplished that the four-pole
devices act either as amplitude limiting means
whereby amplitudes above a de?nite value will be
limited (amplitude low-pass) or that these four
pole devices act as amplitude suppressing means
whereby the amplitudes are blocked below a de?»
nite limit (amplitude-high pass). Principally it
is also possible to obtain four-pole devices adapt
ed for a de?nite amplitudinal range only (ampli
tude ?lter band) or which block certain ranges
(amplitude blocking band).
The ?gures serve for elucidating the subject
matter of the invention, and show examples of
embodiments thereof. In the drawing, Figs. 1
to 4 inclusive show in each case a diiferent em
bodiment of the invention, and each embodiment
being accompanied by a characteristic curve;
Fig. 5 shows a bridge type of network employing
the invention; Fig. 6 illustrates a bridge T-type
network. Figures 1 and 2 show two resistors
having reciprocal resistance values and which
are independent of the amplitude. The one of
them according to Figure 1 consists of two de
tectors GI and G2 placed in parallel, and the
other one according to Figure 2 is formed of a
series connection of two detectors GI and G2.
The detectors may be of the dry recti?er type.
With this arrangement there will be obtained the
symmetry of the resistor for positive and nega
tive amplitudes required for the transmission of 55
alternating currents. In both cases the current
flow through the two detectors takes place in op
posite directions.
The curves indicate the cor
responding relationship between the resultant
resistance R and the voltage U. The potential
U is supplied to the recti?er combinations by the
the case previously mentioned.
However the resistors R1 and R2 may also be
chosen in such manner that they are equal at
direct current source shown in each of Figs. 1
to 4.
When biasing the amplitude-dependent re
in which all amplitudes above a desired limit
sistors by means of auxiliary potentials the re
sistance course can be varied at will within wide
limits. Figures 3 and 4 show the manner of
completing the arrangement according to Fig
ures l and 2 for the purpose of shifting the de
pendence upon amplitude to the outside of a
desired amplitudinal range U0. The curves of
Figs. 1 to 4 have been obtained by measuring the
strength and voltage within the circuits repre
sented; the resistance value R results as the
quotient of strength and voltage, and is shown
as a function of the potential U. By proper
choice of the value of U0 and of the recti?er de
vices themselves, it can be accomplished that the
resistors according to Figures 1 and 2, or ?gures
l3 Li 3 and 4 have reciprocal resistance values; in
other words, that at the amplitudes to be con
sidered there is:
2 13
various, and there is no more balance of the
bridge. The damping for this amplitude scope
will, therefore, be substantially smaller than for
large amplitudes while differing greatly at small
This results in an amplitude ?lter
will not be transmitted.
Figure 6 shows an equivalent four-pole device
in the form of a bridged T-circuit. Herein the
four branches of the bridge are formed by the
in-put and out-put resistor and by the two in
ductances L. The non-linear elements R1 and
R2 having reciprocal resistance values are placed
between the diagonal points. In place of the two
inductances, two equal ohmic resistors or two
equal inductances not coupled to each other, may
be employed. In this case, however, it is neces
sary that the apparent resistance Z of these re
sistors ful?lls the equation
values. The terminals E and the terminals A are
A further feature of the idea of the invention
resides in that for instance the auxiliary po
tentials indicated in Figures 3 and 4 are not ?xed
but can be controlled. In transmission systems
having two directions of transmission, such as
four-wire lines, an amplitude ?lter inserted in
the one direction of transmission may for in
stance be so controlled by the transmission cur
rent passing in the other direction, that it prac
tically blocks all amplitudes thus acting as echo
blocking means.
What I claim is:
1. A four-pole network comprising a bridge
placed at the end points of the bridge diagonals.
circuit having input and output terminals, two
The example of embodiment of the inventive
idea shown in Figure 5 represents a four-pole
device in the form of a bridge ?lter. It consists
of two equal inductances L coupled to each other
and forming two branches of a bridge. The
) other two branches contain the non-linear re
sistors R1 and R2 having reciprocal resistance
If now, the two non-linear resistor combinations
of the bridge arms including reactances, and
R1 and R2 are so dimensioned that they approxi
the other two arms each including opposed rec
ti?ers, the recti?ers in one arm being in series
relation, and those in the other arm being in
40 mately equal each other for amplitudes below a
de?nite limit value, these amplitudes cannot pass
through the four~pole device. The higher ampli
tudes will be subjected to a substantially lower
damping since for these amplitudes the bridge
45 is not balanced. The apparent resistance of the
four-pole device is independent of the amplitude
for amplitudes above the blocking limit. The
bridge is equalized within the amplitude scope
for which the two recti?er combinations R1 and
R2 are equal to each other. Due to this fact,
the damping between the input E and the out
put A is very high. Outside this amplitude scope,
the resistances of the recti?er combinations are
parallel relation.
2. In an alternating current transmission net
work, input and output terminals, a pair of re
actances connected between an input and an ‘
output terminal, a direct connection between
the other input and output terminals, a pair of
rectifiers in parallel and in opposed relation con
nected to a point between the reactances and
to the direct connection, and a pair of recti?ers 50
in series and in opposed relation connected across
both reactances.
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