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Патент USA US2130421

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Patented Sept. 20, 1938
i
UNITED STATES PATENT OFFICE
2,130,421
TRANSMISSION AND RECEPTION OF
INTELLIGENCE
Samuel G. Frantz and Brunson S. McCutchen,
Princeton, N. J., assignors to Radio Corpora
tion of America, a corporation of Delaware
Original application April 23, 1935, Serial No.
17,775. Divided and this application April 17,
1963, Serial No. 74,834
7 Claims.? (01. v179-1)
This invention relates generally to the transmission and reception of intelligence and is speci?cally directed towards improving the quality
of the received intelligence.
5
The present application is a division of copending application Serial Number 17,775 ?led April
23,? 1935, entitled ?Transmission and reception of
intelligence? which in turn is a continuation in
part of application Serial Number 496,595 now
means are provided to re-eXpend the intensity
range to that existing in the Original signal
These means at the receiver must be so] arranged
as to work in correspondence with the compres
10 U. S. Patent No. 2,006,989.
receiver.
More speci?cally, the present invention relates
to systems and methods for maintaining the relations between the various increments of the intelligence issuing from an electrical energy trans15 lating device at a receiving point substantially
The measure of the e?ect of atmospheric dis
turbances or other interference on'the quality of
reception is the ratio of interference intensity to
signal intensity, and this e?eet Will therefore .be
most pronounced when the signal intensity is 15
proportional to the relations between the various
corresponding increments of the original intelligenee-
.
sion effected at the transmission station.
At this point we desire to emphasize the?fact
that one of the bene?ts that will be derived from
the use of our system will be the lessening of
the effect of atmospheric disturbances upon the
.
I
always be greater than it would be were there no
compression of intensity range before transmis
sion, and therefore the effect of interference is
minimized. In other words, when weak signals
are being transmitted the energy Will be more
ampli?ed before it is used [for modulation with
the result that ordinary atmospheric disturb
ances will not obscure the signal.
This invention relates to and comprises the
above described compression and expansion of
intensity range, and means for accomplishing the
compression and expansion.
In applicants? parent applications there are
PTODOSed for this purpose three Ways of inform
ing the receiving apparatus as to what amount of
in the microphone circuit is made to su??er a
expansion is necessary. The three cases may be
smaller percentage variation than the latter.
35 This may be called range compression or subproportional modulation. Thus, in this system
a weak signal 'will be more amplified before it is
classi?ed as follows:
1. Separate wire or radio channel.
lation percentage itself as the signal which com
feature of our invention is then that the intensity
municetes t0 the receiving apparatus how much
40 range or the ratio between maximum and minlmum percentage of modulation of the transmit-
ted radio signal is less than the intensity range of
the original signal. The extent or degree of this
compression of intensity range may in practice
45 result in about the same ratio of maximum to
minimum percentage of modulation as is at pres-
transmitted
modulation.
55
at
constant
'
percentage
In general, in the present system
super-proportional range expansion at the re
ceiver. Expressed mathematically we have:-?
'
30
35
45
_
3
�u_kkI
_
3f 2 2 If� 1 2 1
Where I1=皉1g1na1 Intensity
Iz=transmitted
intensity
of
modulation
_
_
_
50
I3=rece1ver output intensity
I ,
751 and 752 are constants
obliterated,
and a=a constant <1
At the receiving end of the present system
'
1
the intensity range will be compressed but not
'
25
rithmic sub-proportional range compression at
the transmitter wlth corresponding logarithmic
ent obtained by manual control at broadcasting
much further even to the limit at which there is
'
the signal should be empll?ed_
40
The simplest case of the latter would be logaY
stations; or, the compression may be carried
50 a total obliteration of intensity range and the
20
' 2. Variation of carrier frequency.
3. The use of the residual variation of modu
used for modulation than will a strong signal. A
is
10
low. With the present system. during weak orig-_
inal signals, the transmitted signal intensity Will
An object of the invention is to provide a novel
-.:o and e?icient method of transmission and reception of signals.
Another object of the present invention is the
achieving of clear ?delity of reproduction at the
receiving end of radio signals and in particular
2-3 music, by partial or total compression of the intensity range, or range of modulation at the
transmitting end and corresponding expansion of?
the intensity range at~the receiving end.
In the proposed system the degree or percent30 age of modulation applied to the carrier wave at
the transmitting end instead of being made dil?eetly proportional to the intensity of the signal
signal
5
In?usingthe system described in the third sub- 55'
2
2,130,421
division it is obvious, of course, that the intensity
range must not be completely obliterated.
An object of the present invention is to pro
vide a specially constructed bridge arrangement
for effecting the desired compression at the trans
mitter and expansion at the receiver.
Another object of the invention is the pro
vision of a plurality of said specially constructed
resistance bridges arranged in cascade.
Still other objects of the invention will be ap
parent from the following description of typical
points 22 and 23 of the bridge l8 are connected 10
by conductors 24 and 25 respectively to two di
circuits according to our invention illustrated in
agonally opposite points 21 and 26 respectively
temperature bridge;
of a second temperature bridge device I9. The
other two points of said last named bridge,
namely, 28 and 29 may be connected either to an
other similar bridge arrangement or to the modu
Figure 2 illustrates diagrammatically a meth
od by which two or more temperature bridges
by Figure 1 through the medium of conductors Ill
Figure 1 illustrates a transmitter arrangement
may be cascaded; and,
Figure 3 illustrates diagrammatically a receiver
in accordance with our invention employing a
temperature bridge arrangement for receiving an
appropriately expanding signal transmitted from
a system such as shown in Figure 1.
Referring to Figure 1 a microphone circuit is
shown composed of microphone 5, transformer ?I
and the usual source of current 6. An ampli?er
for the current generated in the microphone cir
cuit is shown generally at 8 coupled to the micro
30 phone circuit by means of the transformer 1.
The output of the ampli?er 8 is connected to a
temperature bridge 9 by means of conductors l3
and I2 connected to diagonally opposite points
l4 and I5 respectively of the bridge 9. The
35 other two diagonally opposite points of the bridge
9, namely, i6 and H are connected by conductors
II and I0 respectively, to a modulator and radio
frequency energy source circuit of any well known
design. Referring more particularly to the tem
perature bridge I, 2, 3 and 4 compose the four
elements thereof. Elements | and 4 are of the
same material and elements 2 and 3 are of some
lator and radio frequency energy source as shown
and II. It will thus be evident that in the ar
rangement shown any number of temperature 20
bridges may be connected in cascade for obtain
ing any results desired.
Attention is now directed to Figure 3 which
shows a receiver adapted to properly expand
the signals which were compressed by the trans 25
mitter shown in Figure 1. In Figure 3, 3|! rep
resents generally a stage of audio frequency am
pli?cation in an ordinary radio receiver. Con
pled to the output of said stage by means of
transformer 3| is a temperature bridge 32 in ac 30
cordance with our invention. It will be noted
that the secondary of the transformer 3| is
connected by conductors 33 and 45 to two diag
onally opposite points of said bridge 32. The
other two diagonally opposite points of the bridge 35
are connected by means of conductors 35 and 36
to the input of an amplifier generally shown at
31. The output of this ampli?er 31 is connected
by means of conductors 39 and 38 to a receiving
instrument shown generally as a telephone re
ceiver 40. The bridge 32 is made up of elements
I, 2, 3 and 4 which operate in a somewhat simi
other material having a different temperature
coefficient of resistance than said ?rst material.
The wires it will be evident are appreciably heat
ed by the passage of the currents due to the signal
lar manner to that described above in connection
with Figure 1 except that in the case of the re
voltage applied from the ampli?er output. With
maximum signal voltage the bridge is hottest
greater the applied electromotive force across
the secondary of the transformer 3| the greaterv
and the resistances are so proportioned that
under this condition the bridge is almost bal
anced; that is, the ratio of bridge output volt
age to bridge input voltage is a minimum. .With
very low input voltage the bridge is comparative
ly cold and has a maximum of unbalance and
55 hence the ratio of output to input voltage is a
maximum.
Thus the bridge acts as a non-pro
portional attenuator, attenuating strong sig
nals more than weak ones. While we do not in
tend to limit ourselves to any particular construc
tion of the bridge one way in which the bridge
could be constructed would be of small wires
about the size of ?ash-light bulb ?laments.
65
coe?icient of resistance.
Attention is now directed to Figure 2. In said
?gure conductors l2 and I3 correspond to the
conductors l2 and I3 leading from the output
of the ampli?er 8 of Figure 1. Conductors I2
and I3 are connected to diagonally opposite
points 2| and 20 respectively of the temperature
bridge l8. rI'he other two diagonally opposite
the accompanying drawing, in which
of one form of our invention utilizing a so-called
20
elements 2 and 3 comparatively low temperature -
Either I and 4 or 2 and 3 may be resistances
so designed as to heat but little. Broadly, the
term ?temperature bridge? as used herein in
cludes any network with input and output con
nections in which the ratio of output to input
voltage varies according to the input voltage
70 as a result of change of resistance of any of the
elements of the network due to heating by the
current passing through it.
In Figure 1 the arrangement? could be such
that the elements I and 4 have comparatively
high temperature coefficient of resistance and
ceiver, the bridge will be in approximate balance 45
for minimum signal, so that in Figure 3 the
will be the resistance of elements I and 4 com
pared to the resistance of elements 2 and 3. This 50
condition causes an increased unbalance of the
bridge and an increased output current. It is
to be distinctly understood that while we have
shown only one bridge arrangement in the re
ceiver shown in Figure 3 two or more such bridge 55
arrangements may be arranged in cascade as
shown in Figure 2.
We claim:
1. In a radio receiving system including means
for connecting the input of the system to a 60
source of variable intensity signal energy and
means for connecting the output of the system
to a utilizing circuit, a four-arm resistance bridge
interposed between said two means, opposite
arms of said bridge being constructed so as to 65
have substantially the same temperature coef
?cient of resistance but one pair of said arms
having different temperature coefficient of re
sistance than the other thereof, said bridge be
ing adjusted so as to be approximately balanced 70
for minimum signal intensity and to become more
and more unbalanced as the average intensity
of the signal energy increases, the ratio of out
put to input voltage varying according to the
input voltage as a resultvof change of resistance 75
2,130,421
of any of the elements of the network due to
heating by current passing therethrough.
2. In a radio communication system, a source
of variable intensity signal voltage and a utiliz
ing circuit, a four-arm resistance bridge, a pair
of diagonally opposite terminals of said bridge
comprising input terminals therefor, the other
pair of diagonally opposite terminals of the
bridge comprising output terminals therefor,
means for connecting the source of signal volt
age between the input terminals of the bridge
and
means
connecting
the
utilizing
circuit
in a balanced condition for substantially maxi
mum ?average value of signal intensity and to
become more and more unbalanced as the av
erage intensity of the signal energy decreases,
the ratio of output to input voltage of said bridge
circuit varying according to the input voltage
as the result of changes in the resistance of any
of the elements of the bridge circuit due to heat
ing thereof by current passing? therethrough.
5. A volume range compressor comprising a 10
resistance bridge having input terminals and out
put terminals, means for connecting a source of
between the output terminals of the bridge,
varying intensity voltage to said input termi
each of a pair of opposite arms of said bridge in
nals, a utilizing circuit connected to said output
terminals, means connected in the arms of said 15
bridge for attenuating electrical energy applied
to the input terminals thereof to a greater or
cluding means having a, high temperature coef
?cient'of resistance, the other pair of opposite
arms including means having a comparatively low
temperature coe?icient of resistance, said bridge
less extent depending upon the average intensity '
being adjusted so as to be approximately in a
of the electrical energy applied to the input ter
minals of the bridge, said means attenuating 20
high intensity energy to a greater extent than
low intensity energy whereby the ratio between?
balanced condition for a predetermined value of
average signal voltage and to become more and
more unbalanced as the average intensity of the
signal voltage departs from said value in one
direction, the ratio of output to input voltage of
said bridge circuit varying according to the aver
age value of signal voltage as the result of change
of resistance of any of the means provided in the
arms of said resistance bridge due to heating by
the lowest average intensity of the energy ap
plied to the input of the bridge to the highest
average intensity applied thereat is substantially
current passing therethrough.
greater than the ratio of the lowest average in
tensity of the voltage appearing across the out
put terminals of the bridge to the highest aver
age intensity voltage applied thereat.
3. ?In a radio communication system, a source
of variable intensity signal energy and a utiliz
sistance bridge having' input terminals and
ing circuit, ?a four-arm resistance bridge inter
posed between said source and the utilizing cir
cuit, opposite arms of said bridge including means
6. A volume range expander comprising a re
30
output terminals, means for connecting a source
ture coemcient of resistance than the other pair
thereof, said bridge being adjusted so as to be
of varying intensity electrical energy to said
input terminals, 3, utilizing circuit connect
ed to said output terminals, said bridge including 35
means for attenuating electrical energy applied
to the input terminals thereof to a greater or
less extent depending upon the average intensity
of the electrical energy applied to the input ter
approximately in a balanced condition for a pre
minals of the source, said means acting to at
determined average value of signal intensity and
tenuate high average intensity energy less than
having substantially the same temperature co
efficient of resistance but the means provided for
one pair of said arms having different tempera
40
to become more and more unbalanced as the av
low average intensity energy, whereby the ratio
erage intensity of the signal energy departs from
said value, the'ratio of output to input voltage
of said bridge circuit varying according to the
input voltage as the result of change of resist
ance of any of the elements of the network due
to heating thereof by current passing there
between'the lowest average intensity energy ap
plied to the input terminals of the bridge and
through.
est average intensity energy applied thereat.
7. A volume range expander device comprising, 50.
4. In a radio communication system, a source
of variable intensity signal energy and a utiliz
ing circuit, a four-arm resistance bridge circuit
interposed between said source and the utilizing
circuit, opposite arms of said bridge including
means having substantially the same tempera
ture coe?icient of resistance but the means pro
vided for one pair of said arms having di?erent
temperature coe?icient of resistance than the
means provided for the other pair of arms,,said
bridge being adjusted so as to be approximately
the highest average intensity applied thereat is 45
substantially smaller than the ratio of the low
est average intensity energy appearing across
the output terminals of the bridge andthe high
a four-arm bridge circuit, substantially equal
?xed resistance means having'a low temperature
coe??icient of resistance connected in each of two
opposite arms of the bridge and substantially
similar resistance means having a high tempera 55
ture coe?lcient of resistance connected in each
of the other two opposite arms of the bridge.
SAMUEL G.v FRANTZ.
BRUNSON S. MCCUTCHEN.
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