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Патент USA US2403540

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July 9, E46.
Filed April 23. 1945
2 sheets-sheet 1
, 1946.
Filed April 23, 1943
2. Sheets-Sheet 2
«ln»i -
5. . www1.2¢:
l nu
Patented July 9, 10946
UNITED STATES PATENT ro»l=i=1'c_E`--¿j
- Radio
A. Corporation
Meneley, Princeton,
of America,
J., as'signor to
’ I
Application April'23, 1943,»'Se1‘ial'NoL 484,304'1' l
s claims; (ci. ricami
My' invention relates to the production of the
means ‘,ofga coding ¿disc,~thespeech signaly S- is
multiplied'by the signal K,1and the signal SKf-is
transmitted ,to the receiver. At theV receiver
reciprocal of a signal or wave and particularly
to the production of such a signal for use in a sys-f
tem for secret communication.
In the copending application of Alda V. Bed
ford Serial No. 456,578, filed August 29, 1942, and
entitled Secret communication system,l there is
described a communication system in which the
speech or other communication signal S is mul
tiplied by a coding signal K and in which the 10
product SK is transmitted. At ithe receiver the
incoming signal SK is multiplied. by the recip
rocal of the coding signal K to obtain the orig
inal signal S, that is, SK >< 1/K=S. According to
the above Bedford application, the coding signal
there is another signal generating device for pro.-r
ducing ¿the signal K; it may -be a coding disclike
that at the transmitter, the two coding discs‘be
ingv runin synchronism. The _signal'K generated
at 'the` receiver is supplied to the .reciprocal cir
cuitfto »obtain the decoding _signal `1/K,-which~is
then multiplied With the received signal SK to
obtain'the-Qrieinal signals-f:
i .
1 -, f,
¿The invention Lwill be better understoodfrom
ther following description taken >vin connection
with vthe accompanying'drawingsin which - ¿»
15 ,Figure `1 is a vblock diagram _of signalling appar,
K may be generated-by means of aîcode disc
which is cut toy make-its periphery have the wave
2 to 5 are'
~ 'arereferredto
' -f
form of the signal K lwhile the decoding signal
in explaining the» invention; '_i
l/K may be produced by, a differentA discwhich
. Figure 61isa circuit diagram of a reciprocal cir
is cut in accordance with calculated values to 20 cuit designed inaccordance with one embodiment
make its periphery have the Wave form of l/K.
of the-invention,
- v
v- »
In a later application of Alda V. Bedford Yand
A. 'Figure 7 >is a circuit diagram ofanother recip~
Frank P. Wipñî, Serial No.-480,716, ñled March
rocal circuit designed in` accordance with another .
26, 1943, and entitled Reciprocal circuits, there is
embodiment ofthe invention, and . A,
described one type of electrical circuit for pro
ducing-the reciprocal ofa signal or wave such
--Figureß 'is a` circuit‘diagramiof-a multiplier cir
cuit Vthat may be `utilized in- .the circuitioffFig. ¿1;
as the wave K.
r' ,
~In-the- several' ñgures; similar parts are indi
An object of the present-invention isl to pro-A
cated by’ similar reference characters. g f
ducing the reciprocal of a signal or Wave. ‘
A further object of the invention is to provide
an improved electrical circuit for converting an
» ~
>.i--Referring `„to Fig; 1,V the invention is shown ap-`
vide an improved method of and means for pro
30 plied to radio apparatus that may-be >switchedgfoz‘nf, .
operation either as a transmitter or as a receiver.
Theseveral switches are shown in the'ppsi-tionior
applied signal having a certain wave form into a
transmitter operation,
signal having the reciprocal wave form.- ' .
the apparatus that `will iflrst Vbe described. «,A
A still further object of the invention is'to pro
vide an improved communication'syst’em for se
cret signalling.
vThis , is f the t operation f oi
35 microphone and a speechampliner are-showniat
In a preferred embodiment of my invention the
>reciprocal of a wave K is-obtained yby> means of
f'lyand v8,-‘respectively.,` 'The .signal S is applied
through -a switch.k 9 »to a multiplier unit. i4, which
may be of; the samev designv as thatdescribedyin
the above-identified. Bedford application or which
an electrical circuit in which'the îwaveK is clipped 40 maybe of the type vshownin Fig. -8_ and described
on both its positive cycle and onïits negative
and `claimed ingapplication Serial No. 484,303, ñled
cycle to produce a rectangular wave, and in which
on the same day as the present applicationin
the wave K and the rectangular'waveare added
the namepf >Frank-P. Wipff and entitled Multi
together with one of them' reversed in polarity,
plier Fcircuits. _'The code Isignal K may :be profl
preferably after the peaks‘of‘the positive >and
ducedfby; means of a'code disc I6, a maskA |71, a
negative cycles of the wave K have been
light source'lß, a condensing lens I9, and a pho
“squashed” or flattened somewhat. My recip
toelectric-Y cell '2_0., ,The signalrK is, supplied
rocal circuit contains nocapactive lor-ginductive
-through amplifiers 2l and. 22 and through a
reactances (the blocking capacitors inthe‘circuit
switch to the multipler unit '14. The resulting
presenting a negligible impedance» and,; there 50 multiplier-.output signal -SK is supplied through
fore, functions the same for )any applied signal
anv ampliñer 2B*- and through a sWitchÍZl ltoa.
regardless of its frequency or waveform. e ,
radio-v transmitter 28 or to a wire line, if .pre
In utilizing the reciprocal lcircuit in a commu-‘
nicationy system,;a coding signalK--is generated at
the transmitter in any suitable manner'fas'by ' ‘
' The receiver Vfo-rfdïecocling the gsignalSK may C
be the same» apparatus. as¿_rin Eig. :1.,with switches
9, 23 and 21 thrown to their contact positions R.
The signal SK is supplied from a radio receiver
3| through the switch 9 to the multiplier I4. The
of comparatively low resistance are connected
in series with the diodes 62 and 63, respectively.
A biasing voltage drop for opposing current ñow
coding signal K produced by the disc I6 is sup
plied through the amplifier 2l to a reciprocal cir
cuit 32 designed in accordance with my inven
thereacross, a resistor 61 being in series with the
through diode 63 is produced across the resistor
66 by connecting a source of voltage (not shown)
rocal circuit 32 supplies the decoding signal l/K
voltage source. The diodes 62 and 63 clip the
applied wave m symmetrically about its A.-C.
through the switch 23 to the multiplier I4. The
resulting output of multiplier I4 is the original
communication signal S since SK >< l/K=S. The
signal S is ampliñed by the amplifier 26 and supn
across the capacitor 59 by the positive cycle
pulses ilowing through the diode 63. Thus, the
tion and shown in detail in Fig. 6.
The recip
plied through the switch 21 to headphones or to
the loudspeaker 33.
The code disc I6 at the transmitter and the
similar code disc at the receiver are held in syn
chronism and in the proper phase relation by
suitable synchronizing means. For example, at
the transmitter a 60G-cycle per second current
from a source 36 may be supplied through a
switch ,31 to a synchronous motor 38 which ro
tates the code disc I6.
The GOO-cycle current
axis because a voltage which causes current flow
through the diode 62 and resistor 64 is built up
diodes 52 and 63 become conducting on alternate
cycles when the signal voltage exceeds the D.-C.
voltage drop across the resistors 64 and 66, re
spectively. The resulting rectangular wave 1L
is amplified and reversed in polarity by the tube
The wave n and the flattened wave m add
in the portion of the anode resistor 51-51' that
is common to the tubes 54 and 58 to produce the
desired reciprocal wave I/K shown in Fig. 5.
If the wave m is flattened correctly and if the
waves m and n are added with the correct rela
also modulates a radio transmitter 39 for the
tive amplitudes, the resulting signal will be sub
transmission of synchronizing signals to the re
ceiver. At the receiver the switch 31 is in its 25 stantially a true reciprocal of the wave K. The
contact position R whereby the received 600
only substantial departure from a true reciprocal
signal will be where the wave K crosses the A.-C.
axis. Here the reciprocal value is infinity
whereas the maximum amplitude of the wave
may be preferable to transmit the synchronizing
30 I/K necessarily has a deñnite limit. The .waves
signal over a wire line.
m and n may be mixed with the correct relative
My method of obtaining the reciprocal wave
amplitudes by adjusting a variable tap '1l on
I /K will now be explained with reference to the
cycle current is supplied from a radio receiver 4I
to the synchronous motor 38. In some cases it
graphs of Figs. 2 to 5. The graph of Fig. 2
represents the wave K while the graph of Fig. 5
represents substantially the reciprocal wave I/K
the anode resistor 51.
The correct shaping of
the flattened wave m may be 'obtained byselect
ing a non-linear resistor unit 53 having a suit
which is the sum of the flattened wave m of
able voltage-resistance characteristic and by ad
reversed polarity shown in Fig. 3 and the rec
tangular wave n of Fig. 4. The “squashed” or
justing the value'of the resistor 52.
As previously noted, the above-described re
ciprocal circuit isV purelyresistive so that its
flattened wave m may be obtained by passing
the wave K through a circuit that changes its 40 operation is independent of frequency. > The in-`
stantaneous voltage 'output of the circuit'A is
resistance with a change in applied voltage.
always the reciprocal of the instantaneous ap
The rectangular wave n may be produced by
clipping the positive and negative cycles of the
wave m at the voltage levels e and f, respectively,
for example, near the alternating-current axis of
the signal and then amplifying the clipped signal.
Fig. 6 shows, by way of example, one reciprocal
circuit that -may be employed in practicing the
invention. The wave K, having a peak-to-peak
plied voltage. It follows thatîîf the reciprocal
circuit is adjusted to produce the reciprocal of
an appliedI signal having one wave form, the cir
cuit will then always produce the lreciprocal of
an applied signal regardless of itsv wave form.
There are various ways of determining when the
circuit has been adjusted to give substantiallya
amplitude of 6() volts, for example, is applied 50 true reciprocal` ‘ One way is to connect the re
ciprocal circuit into the signalling system of
through a blocking capacitor 5I and a resistor
Fig. 1 and, while transmitting speech or music.
52 to a copper oxide rectifier unit 53 which
vfunctions as a non-linear resistor having the
property of decreasing in resistance as the ap
plied voltage increases. The resistor 52 is of
high enough resistance so that the driving source
for the non-linear resistance unit 53 is of high
adjust the resistor 52 and the variable tap 1I
at the receiver until the speech or music has» a
minimum of distortion.
Fig. 'Z shows a reciprocal circuit that is the
same as that of Fig. 6 except that a `pair of di
odes 12 and 13 have been substituted for the
impedance whereby there is only a slight varia
copper oxide rectiñers 53a and 53h. The diodes
tion in the current iiow through the unit 53.
The unit 53 may consist of a pair of copper 60 ‘i2 and 13 may beproperly biased by adjusting
a pair of variable taps 14 and 16 on resistors 11
oxide rectifiers 53a and 53h connected to conduct
and 18, respectively. When properly biased, the
current in opposite directions.
two diodes will be operated along the lower knee
The voltage appearing across the non-linear
of their characteristic curve and in the proper
unit 53 is the voltage m of Fig. 3 having the flat
tened wave form. This voltage is amplified by a 65 region to shape the wave m in the desired manè
ner. It will be noted that the bias applied. to
cathode biased vacuum tube 54 and appears
the cathode of the diode 12 is of positive polar
across an anode resistor 56 and a portion of the
ity and corresponds tothe positive bias applied
anode resistor 51-51’ of a second amplifier
to diode 63 of Fig. 6. Also, the diode circuit 12
tube 58.
13 operates the same as the diode circuit 62-53
The rectangular wave n is produced, in this
except that the adjustment of the bias and the
particular example, by applying the output of the
magnitude of the applied signal ’are such that
tube 54 through a blocking capacitor 59 and a
the signal is not clipped.
i ` ‘A "
high Yimpedance resistor 6I to a pair of diodes
It will be understood that the invention is
62 and 63 which are connected to conduct in
opposite directions. Output resistors 64 and 66
not limited to the particular circuits illustrated
adjusted; only.v .the f 'desiree product iterm'igzsx
and the D.-C. component A2. appear'at'the 'junc
tion-point 9|. In practice it is- necessary "toad
ïju'st'the multiplier circuit carefully for minimum
vsince the lwaves m 'andr-n, maybe derived from
"the wave K in various-'ways andìsince the two
'waves may be combined by means of a variety of
l residual _fsig'nal when' >eitherïthe signal Sor'ïthe
According to the above-identiñed Wipff appli
signal K is removed:
= -'
cation, the multiplier circuit I4 may utilize' one
' '-‘In the several figures, circuit values- are'rgiven,
of several known types of circuits that have the.
merely by-way-of example, in ohms, megohms,
property of providing an instantaneousoutput
voltage which is proportional to the square of
"and microfarads. '
the instantaneous input voltage for a reason' 10 _»I `claim as my invention:
- - f. .
"1‘ ’The methcd 0f ' VI'Qdlißîng the reciprocal’v of
able voltage swing. Such circuits will be >referred
to as “squaring circuits,” and will be designated
:a lsignal that-reverses in polarityat intervals with
“Q” where referred to in the description ’anfd
'respect to >an alternating-current ` axis whereby
drawings. In the multiplier circuitïillustratedin
the »signal has'cross-ov'er'points yon saidfaxis, said
K are added, then the sum S-|-K is squared inta~
third squaring circuit Qa and the squared signal ¿
over’points, and' whichireverseis in polarity rat
said cross-over points, producing another'si'g'nal
Fig. 8, the waves S and K to ¿be lmultipliedl >are ,15 niethodlcomprising the stepsof producing'a'si'g‘
each separately squared in two squaring-circuit's»
"rial'that `has ai relatively largev amplitude >sub
stantially at the’time of occurrence -of said; cross
Q1 and Q2. In a branch circuit the signals S and
is reversed in polarity. 'I‘he three outputs of Q_i, 20 that has a wave form approximately,` similar to
that of the first-mentioned signal, and adding
Ch and Q3 are then added to obtain the sum as
shown in the following equations:
the two produced signals with one of them re
versed in polarity and having the proper ampli- _»
tude with respect to the other produced signal
25 for producing a sum voltage that is substantially
the desired reciprocal signal.
2. The method of producing the reciprocal of
The value “A” above is the D.-C. component or
a signal that reverses in polarity at intervals withv
bias that is applied to the squaring circuits to
respectr to an alternating-current axis whereby
cause the voltage swing always to be on the de
sired portion of the squaring circuit character 30 the signal has cross-over points on said axis, said
method comprising the steps of producing a sig
istic curve.
nal that has a relatively large amplitude at the
Referring more speciñcally to Fig. 8, the vac
uum tubes 80, 8| and 82 are utilized as the squar
ing circuits Q1, Q3 and Q2, respectively. These
tubes must have plate current vs. grid voltage 35
characteristic that follows substantially a square
law. Vacuum tubes of the types 6.15, BSN?, 605,
and other triodes have suitable characteristics.
The plate resistors for such tubes should be kept'
small, not more than about 1000 ohms.
The signals S and K are applied to the grids
of tubes 80 and 82 through resistors 83 and 84,
respectively. Both of the signals S and K are
applied to the grid of tube 8| through resistors 45
85 and 86, respectively. A suitable negative bias
is applied to the grids of the tubes 80, 8| and 82
through grid resistors 81 and 88. The resistors
B3, 84, 85, 86, 81 and 88 all have the same com
paratively high resistance, such as between 0.1' to
megohm and 1 megohm, so as not to load the
time of occurrence of said cross-over points, and
which reverses,v in polarity at said «cross-over
points, producing another signal that has a wave
form approximately` similar to but ilatter than
that of the first-mentioned signal, and adding
the two produced-signals with one of them re
versed in polarity and having the proper ampli- ,k
tude with respect to the other produced signal '
for producing a sum voltage that is substantially
the desired reciprocal signal.
3. The method of obtaining the reciprocal of
-a, signal having a certain `wave' form which com
prises the steps of producing a signal of` substan
tially rectangular wave form having positive and
negative cycles corresponding to the positive and
negative cycles of the >first signal, producing an
other signal that is generally similar in vwavev
form to the first-mentioned signal, and adding ,Y .
comparatively low impedance driving source too
said rectangular wave to said other wave _with
much. However, the resistance is not made so
high as to permit~ excessive phase shift due' to
grid-cathode capacity. Since the pairs of re
' one of the waves reversed in polarity andV with
the two waves having such relative amplitudes
that said reciprocal signal is obtained?
sistors 83-81, 85--86, and 84-88 act as voltage '
9, signal having a certain wave form which com
dividers for the applied signals, the voltages ap
plied to the grids of tubes 80, 8| and 82 will be
4. The method of obtaining the reciprocal of
prises the steps of producing a signal of substan
tially rectangular wave form having positive and
negative cycles corresponding to the positive and
negative cycles of the ñrst signal,- flattening the y
positivejand negative cycles of the '.ñrst signal,
The grid bias (_C) on tubes 80, 8| and 82
and Aadding said rectangular wave to saidilat
should be about to the middle of the straight por
tened wave with one of the `waves reversed in ,
tion of the grid voltage vs. mutual' conductance 65 polarity.
curve. For a 6SN7 or 6J5 with 250 volts on the
plate, this is about -14 volts.
A vacuum tube 89 serves to reverse the polar
ity of the output of tube 8| and should have ap
5. An electrical circuit for` obtaining Vthe recip
rocal value of- a voltage applied thereto compris- -
ing means for producing a substantially rectan->
gular wave having positive and negative cycles
proximately unity gain and very low distortion.
corresponding tothe positive and negative cycles
The outputs of the tubes 80 and 82 and of the re
of a voltage applied to said circuit, vI_neans for
versing tube 89 are added by supplying them to
producing a wave having flattened positive and
a common junction point 9| through adding re
negative cycles corresponding to the positive and
sistors 92, 93 and 94. These adding resistors may
negative cycles of the voltage applied to said cir- ' ~
have a resistance of from 0.05 megohm to 0.1
75 cuit, and means for adding said rectangular wave
megohm, for example. If everything isproperlyY
Ito 'said iiattened Wave with ,one of- the waves
reversed in polarity.
~ » „ '
.6. The invention according to claim«5_ wherein
lthe impedance of the circuit is substantially
purely resistive at the-frequencies of the applied l
7. `An electrical circuit for obtaining the recip
rocal of a signal voltage applied thereto com
prising a non-linear resistive device which de
8. Anelejctrical circuit for obtaining the recip
rocal of a signal voltage applied thereto `com
aprising a non-linear resistive device which de
creases in resistance with an increase in applied
voltage, means' for passing said signal voltage
through said resistive device whereby its Wave
form is flattened, means for .clipping said signal
voltage symmetrically with respect to its alter
nating-current axis _to produce a rectangular
creases in resistance with an increase in applied 10 voltage wavev having positive and negative cycles
voltage, means for passing said signal voltage
corresponding to the positive _and negative‘cycles
through said resistive device whereby its wave
-form is flattened, means for producing a sub
of said signalwavaand means for adding said
rectangular wave to said ñattened wave withone
of said waves reversed in polarity and withvtheir
relative amplitudes such as to produce a sum
voltage that is the desired reciprocal signal.
stantially rectangular voltage wave having posi
tive and negative cycles corresponding to the
positive and negative cycles of said signal wave,
and means for adding said rectangular Wave to
»said flattened wave with one of said waves re
versed in polarity.
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