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Патент USA US2403727

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July 9, 1946.
2,403,727
A. V. LOUGHREN
DIRECTION FINDING SYSTEM
Filed'Nov. 10, 1941
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INVENTOR
ARTHLR V. LOUGHREN
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ATI' RNEY
July 9, 1946.
‘A. v. LOUGHREN
2,403,727
DIRECTION FINDING SYSTEM
Filed NOV. 10, 1941
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INVENTOR
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BY
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July 9, 1946.
A. v. LOUGHREN _
2,403,727 f
DIRECTION FINDING. SYSTEM '
Filed Nov. 10, 1941
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A
ORNEY
Patented July 9, 1946
2,403,727
UNITED STATES PATENT OFFICE
2,403,727
DIRECTION-FINDING SYSTEM
Arthur V. Loughren, Great Neck, N. Y., assignor,
by mesne assignments, to Hazeltine Research,
Inc., Chicago, 111., a corporation of Illinois
Application November 10, 1941, Serial No. 418,541
8 Claims.
1
The present invention relates to direction-?nd
ing systems and particularly to such systems of
the type employing a pair of spaced antenna sys
tems by which to receive a carrier wave radiated
from a remote point and to utilize the two carrier
waves received by the pair of antenna systems to
provide an indication of the direction of the
source of the carrier wave relative to the orienta
tion of the antenna systems or, conversely, by
(01. 250-—11)
.
2
simultaneous bearings on the same transmitting
station.
,
Another form of prior art direction-?nding sys
tem employs a directional antenna system, as in
the arrangement just described, but uses in ad
dition a so-called “sense” antenna system where
by the sense of the direction of the transmitting
station may be determined and by which mod
ulation components of the received carrier wave
which two carrier waves may be radiated to a 10 may be continuously reproduced simultaneously
remote point and may be received at the remote
point and utilized to provide an indication of the
direction of the remote point from the antenna
systems.
It is frequently desirable to obtain a direc
tional indication as well as an indication of the
sense of direction of a transmitting station from
a receiving apparatus. Direction-?nding systems
are known for this purpose and are useful in de
with the operation of taking a bearing on the
transmitting station. While this prior art ar
rangement avoids several of the disadvantages
and limitations of the prior art system ?rst de
15 scribed, it has the disadvantage that the antenna
systems employed are frequently complex and re
quire critical relative proportioning. There is the
additional disadvantage that the receiving ap
paratus used in such systems is relatively com
termining the position of a transmitting station 20 plex, and therefore expensive, and generally re
from two receiving stations or of a receiving sta
quires that critical proportioning of circuit con
tion from two transmitting stations, such deter
stants be established and maintained between
mination being e?ected by the method of tri
the units of the apparatus which are connected
angulation.
to the several antenna systems if satisfactory
In one form of direction-?nding system of the 25 operation of the direction-?nding system is to be
prior art, the receiving station employs a single
secured.
antenna system having a sharply-directive char
It is an object of the present invention, there
acteristic by which an indication of the direction
fore, to provide a new and improved direction
of a transmitting station is determined by so
?nding system which avoids one or more of the
orienting the antenna system that the received 30 disadvantages and limitations of prior art sys
carrier wave has minimum intensity. This is the
tems.
so-called null method of direction determination.
It is a further object of the invention to pro‘
Such systems have the disadvantage that the null
vide a direction-?nding system of the type em
point, that is, the point providing minimum car
ploying at least one pair'of spaced antennas and
rier-Wave intensity, cannot be accurately deter 35 one possessing a degree of sensitivity and ac
curacy of a much higher order of magnitude
mined for numerous well-known reasons. Sys
than prior art direction-?nding systems of this
tems of this nature have the further disadvan
nature.
tages that the sense of direction of the transmit
It is an additional object of the invention to
ting station cannot be obtained Without the use
of an additional antenna system and additional 40 provide a direction-?nding system adapted to re
ceive a modulated carrier wave and one in which.
receiving equipment used therewith. There is
a bearing may be taken on the source of the re
the further disadvantage that, since the system
ceived carrier wave while simultaneously, continu
is operated to provide minimum intensity of the
received carrier wave, any modulation com 45 ously, and satisfactorily reproducing the mod
ulation components thereof.”
__
ponents of the received carrier wave cannot
In accordance with the invention, a direction
ordinarily be satisfactorily reproduced during the
?nding system comprises a pair of antenna sys
time that a bearing is being taken on the trans
tems physically spaced by a value which provides
rnitting station. This fact prohibits the use of
such systems where it is essential that modulaé 50 a measurable phase di?erence in at least one
direction between wave signals of a given fre
tion components of the received carrier wave be
quency radiated by the antenna systems. The
continuously and satisfactorily reproduced si
system also includes a pair of carrier-wave trans
multaneously with the act of taking a bearing on
lating paths having output circuits individually
the transmitting station, as, fOr example, to in
sure that two such direction-?nding systems take 55 coupled to the antenna systems and having a com
mon input circuit, and a source of carrier Waves
2,403,727
3
coupled to the input circuit and having the afore
mentioned given irequency. The system addi
tionally includes means for varying the amplitude
of the carrier wave translated by one of the paths
in accordance with a modulation signal, and
means for varying the amplitude of the carrier
Wave translated by the other of the paths in ac
cordance with such modulation signal but with
a predetermined phase displacement relative to
the ?rst-named variation to provide around the
antenna systems effectively one radiated carrier
wave phase-modulated with the modulation sig
nal, the amplitude Of the phase modulation vary
ing with the radial direction around the antenna
4
detector, for reasons presently to be considered,
a differentiating network.
The direction-?nding system includes a source
of modulation signals comprising an oscillator 21
which generates oscillations, preferably of sinu
soidal wave form and of relatively high audio fre
quency or supersonic frequency, for example,
15,000 to 20,000 cycles per second. The output
circuit of the oscillator 21 is coupled to a second
winding 28 of the voltmeter 26, the windings 25
and 23 being normally spring-biased into coaxial
alignment in conventional manner when the
meter pointer is undeflected, but one of the wind
ings being relatively movable to produce de?ec
tions
to either side of the zero-center-scale point,
systems from a given reference radial direction.
in accordance with the relative magnitude and
For a better understanding of the present in
phase of the alternating potentials applied to the
vention, together with other and further objects
windings 25 and 28.
thereof, reference is had to the following descrip
The direction-?nding system includes means
tion taken in connection with the accompanying
for varying the amplitude of the carrier wave
20
drawings, and its scope will be pointed out in the
translated by one of the paths, for example, the
appended claims.
path I2, in accordance with the modulation sig
Referringr now to the drawings, Fig. 1 is a cir
nals, and means for varying the amplitude of the
cuit diagram, partly schematic, of a complete di
carrier wave translated by the other of the paths,
rection-?nding system of the carrier-wave re
for example, the path I3, in accordance with the
ceiver type embodying the invention; Fig. 2 is a 25 modulation signals but with a predetermined
circuit diagram, also partly schematic, of a com
phase displacement relative to the variation of
plete direction-?nding system of the carrier-wave
the ?rst-named path. This means comprises a
transmitter type embodying a modi?ed form of
control electrode 29 provided in the vacuum-tube
the invention; and Fig. 3 is a circuit diagram,
repeater It, a control electrode 30 in the vacuum
partly schematic, Of a complete direction-?nding
tube repeater I6, and a transformer 3I having a
system embodying an additionally modi?ed form
primary winding 32 coupled to the output circuit
of the invention.
of the oscillator 2'! and a secondary winding 33
Referring now more particularly to Fig. 1, there
coupled between the control electrodes 29 and 30.
is represented schematically a complete direc
tion-?nding system of the carrier-wave receiver 35 The control electrodes 29 and 30 may comprise
conventional suppressor grids and have applied
type embodying the present invention in a pre
thereto
a suitable operating bias through individ
ferred form. The system includes a pair of an
ual halves of the transformer secondary winding
tenna systems IE, II, which may be of the dipole
33 from a source of bias potential indicated as
antenna type, and a pair of carrier-wave trans
-C. The transformer 3| thus applies the oscil
lating paths i2, I3, coupled to individual ones of
lations generated by the oscillator 21 to the con
the antenna systems If), I I and adapted to trans
late carrier waves of the same frequency applied
thereto from a common carrier-wave source. The
carrier-wave source in this form of the invention
comprises a single transmitting station, not
shown, situated at a distance from the direction
?nding system. The translating path I2 com
prises a vacuum-tube repeater I4 having an in
put circuit 55 adapted to be tuned to the fre
quency of the received carrier wave and coupled "
to the antenna system II. Similarly, the trans
lating path I3 comprises a vacuum-tube repeater
I6 having an input circuit IT also adapted to be
tuned to the frequency of the received carrier
wave and coupled to the antenna system ID. The
vacuum-tube repeaters I13 and it have a common
output circuit which is coupled to the input'cir
cuit of an oscillator-modulator I8.
Coupled to
the output circuit of the oscillator-modulator I8,
in the order named, are an intermediate-fre
quency ampli?er I9 of one or more stages, an
amplitude detector 20, an audio-frequency am
pli?er 2| of one or more stages, and a sound-re
producing device 22 comprising a pair of head
phones. There'is also coupled to the output cir
cuit of the intermediate-frequency ampli?er I9,
in addition to the amplitude detector 20, an am
plitude-limiting system 23 to the output circuit
trol electrodes 29 and 30 of the respective vac
uum-tube repeaters I4 and IS with opposite rela
tive phase.
Considering now the operation of the direction
?nding system just described, the desired carrier
wave from the distant transmitting station is
received by each of the antenna systems II), II.
The phase difference between the carrier waves
received by the antenna systems varies with the
relative orientation of the antenna systems
with respect to the transmitting station due to the
di?erent time intervals required for the radiated
carrier waves to travel through space to individual
ones of the antenna systems for different rela
tive orientation. They have zero phase difference
when the transmitting station lies on a line per
pendicular to the plane of the dipole antennas I0
and I I and maximum phase difference when the
transmitter lies in the plane thereof, the carrier
signal received by the antenna system closer to
the transmitting station having leading phase
relative to the carrier signal received by the other
antenna system,
The received carrier waves are
applied to individual ones of the vacuum-tube
repeaters I4 and I6 and are repeated thereby to
their common output circuit. However, the oscil
lations applied to the control electrodes 29 and 36
at the respective vacuum-tube repeaters I4 and I6
of which is coupled, in the Order named, a phase 70 from the oscillator 21 vary the repeating ratios
of the vacuum-tube repeaters in opposite senses
or frequency detector and ampli?er 24 and one
in accordance therewith. There is consequently
winding 25 of a zero-center-scale dynamometer
derived in the common output circuit of the
type of voltmeter 2'5. In the event that the detec
vacuum-tube repeaters l4 and I6 a phase-modu
tor of unit 24 is of the frequency-detector type,
there may be included in the output circuit of the 75 lated carrier wave, which may correspondingly be
2,403,127
considered a frequency-modulated» carrier wave,
tion- indication provided‘ by the, de?ections of
the degree and sense of the‘ phase or frequency
modulation of which varies with the phase d'i?er
ence. between the carrier waves received by the
antenna systems It‘ and I'll. By the term “sense”
of the phase or frequency modulation, as’ here
used, is meant that, for a selected half-cycle‘: of the
voltmeter 26 may be utilized in either of two
ways. The ?rst of these, requires that the an-'
tenna' systems [01 and; Hi be rotatable about an
axis parallel to the dipole antennas- I0 and I'll
In this method of operation, the antenna sys
tems l0 and II are rotated or oriented about
their axis until the transmitting station lies on! a
line perpendicular to the plane of the"3dip'ole
oscillations of~ oscillator 21-, the carrier signal
derived in the common output circuit of the
vacuum-tube repeaters I54’ and lit-‘has a phase 10 antennas ‘I0 and l I, at which time the carrier
or frequency advanced or retarded with respect
waves received-by'the antenna systems-have zero; '
to that‘ phase or frequency which it has when
phase difference and the degreeof phase modula
the‘ carrier signals received by the antenna sys
tion of the phase-modulated carrier wave, derived
tems H] and HT have'zerol phase difference, its
in the common output circuit of the vacuum
phase or frequency being‘ advanced or retarded, [5 tube repeaters I4 and I6‘, is zero withresult'ant
for example, when theph-ase-of the carrier signal
received by the antenna system Ii! respectively
absence of de?ection of the voltmeter 26' from
its zero-center-scale point‘. This- method of
leads or lags that of the carrier‘ signal received by
the antenna- system M. This derived phase
modulfatedi carrier wave is converted to an inter
mediate-frequency phase-modulated carrier wave
by‘ theoscillator-modulator I38; is ampli?ed by the
intermediate-frequency ampli?er I19), is limited to
a predetermined substantially constant amplitude
by the-limiting system 23, and‘ the’ phase-modula
operation is perhaps the‘ preferred one since the
direction of deflection of the voltmeter 27$7from
20
direction in which the antenna systems It‘ and
II should be rotated to obtain the desired bear
ing on the transmitting station. ~ It may be: noted
in this regard that the indications of voltmeter"
26 provide an indication not only of the direction
of the transmitting station from the antenna
systems l-D and H, but also of the sense of that
tion or corresponding frequency-modulation com
ponents thereof are derived’ by the phase or fre
quency detector of unit 24. When the detector of
unit 254 is of the phase-detectortype, the derived
phase~mod5ulation components correspond to the :
modulation signal, the latter comprising the oscil
lations which are generated? by the- oscillator 27.
When the detector of unit 24 is of: the frequency
detector type, the? detector derives the modulation
components, but the wave form of the latter is
that obtained by di?’erentiation of the modulation
signal‘. In this case, the derived modulation com»
ponents are applied to the ampli?er of unit 24
through an integrating network included in the
output circuit of the detector, the integrating net
its-zero-center-scal'e point directly indicates the
M
direction. Thus, if rotation of the antenna sys
tems l0 and H in the direction indicated byra
particular de?ection of the voltmeterv 26 pro
duces a larger de?ection of the voltmeter, con
tinued rotation of the antenna systems; in‘ vthe
same direction will- produce further increasing
de?ections up to a maximumqvalue butv thereafter 7
the de?ections will decrease until zero de?ection
is attained, at which time it will be known that
the transmitting station lies not only on aliné
perpendicular to the plane of the dipole an
tennas I01 and H but also is positioned on a par
ti‘cufl'ar’ side thereof.
*
>
worl'r serving to restore to the derived modulation
* Alvse'cond method of operating the direction
components the wave form which they should
?n'dilng system of the invention is one'which're
have accurately to correspond to the modulation
quires that the antenna systems Ii)" and’ ill be
signal‘. It is to be understood that any reference
?irxedl in space, rather thanv being rotatable. In
to a frequency detector in this speci?cation is in 45 this case, the de?ections of voltmeter 26-‘ may be
tended to be one which includes the integrating
directly calibrated- in degrees of orientation of
network in its output circuit.
the antenna system's Hi and‘ Hv with respect to
It may be noted at this point that when the
thepositions which any transmitting station- may
oscillations generated by unit 21 have a sinusoidal
have about‘- the antenna systems. This method
wave form, the integrating network becomes
of operation provides an indication of the direc
merely one to provide a QO-deQ-ree phase shift and
tion of a transmitting station from‘ the antenna
in this event may be included in the output cir
systems It and H, but does" not provide :an,
cuit of the frequency detector of unit 24' or in cir
indication of the sense of direction:
,
cuit with either of the windings 25 or 28' of the
Inthe event that the received carrier wave; is
voltmeter 26'. Such a phase-shifting network is, 55 also amplitude-modulated or frequency-modu
in general, a differentiating or an integrating net
lated in accordance with a‘ modulation signal,
work; when it handles a single frequency, the
the directione?nding systemof the invention has
difference between these twoiisdeterminabl'e only
the‘. advantage that the modulation-signal; com
by the relative polarity of the phase-shifting net~
ponents- of the carrier wave‘ may be continuously
work’s output. The modulation components de
and satisfactoriiy ' reproduced} simultaneously
rived hy- the- detector of unit 24: are ampli?ed by
with the taking of a bearing on the transmitting
the ampli?er of this unit and applied to; the- wind
station.v ‘This results from the fact that the act
ing 25 of the voltmeter 25. There is. consequently
of taking a. bearing on the transmitting station
applied to the windings 25 and 28 of the volt
does-znot?rileq’uire“i‘tliieft'l the‘ antenna‘; system, be‘ so
meter modulation signals of the same frequency 65 oriented that the carrier wave‘recei-‘ved' thereby '
and wave form but differing in relative amplitude
has‘ minimum intensity; The continuous repro-v _ ~
and phase in accordance with the phase difference
duction of the amplitude-modulation or fre
between the carrier waves received by the antenna
qne’ncyirncdulatienrcomponents of ‘the’ received
systems It, II. The resultant de?ections of the
carrier wave simultaneously with the act of tak;
voltmeter 26 directly indicate the relative orienta 70 ing‘ abea'rm‘g' on: .the'i-"source thereof
great
tion of the antenna systems [0 and I I‘ with respect
importance where two direction-?nding systems
to the transmitting station from which there
are simultaneously taking. bearings on the‘ source
ceived carrier wave is radiated.
.
to’determine. the position thereof by the‘ method
The. voltmeter 26-, as previously stated,‘ is pref‘
of; triangulation, and; it‘ is ‘essential; that the oper~
erablyof the zero-center-scale type; ‘The direc is ators of ebotlridirection-?ndin’g' systems be certain
2,403,727
'7
ers l4 and I 6, respectively, from the oscillator 21,
the variation of amplitude of the carrier wave
translated by the translating path l3 due to the
mitting station. This is particularly important
where the transmitting station is of the mobile
type and is in continuous motion or is moved at
frequent intervals.
It has been stated that the carrier wave de
rived in the common output circuit of the vacuum
tube repeaters I4 and i5 is phase-modulated with
the modulation signal derived from the oscillator
21. If the received carrier wave is itself ampli
tude-modulated or frequency-modulated by a
8
oscillations applied to the vacuum-tube repeat
that they are taking bearings on the same trans
oscillator 21 being at the same frequency as but
with a predetermined phase displacement, in the
arrangement described 180 degrees, relative to
the corresponding amplitude variations of the
carrier wave translated by the translating path l2.
If desired, a phase-shifting network, not, shown,
10
may be included in circuit with either the wind
ing 25 or the winding 28 of the voltmeter 26 to
permit correction of minor phase errors accu
carrier wave and its modulation components are
mulated around the system which would tend to
translated by the vacuum-tube repeaters I4 and
I6 and the derived carrier wave consequently is 15 produce slight errors in the direction indications
provided by the Fig. 1 arrangement.
~»
both amplitude-modulated or frequency-modu
Fig. 2 represents schematically a complete 1di
lated with the signal to be transmitted and also
rection-?nding system of the transmitter type
phase-modulated with the signal derived from
embodying the invention in a modi?ed form.
the oscillator 21.
If the received carrier wave is amplitude-mod 20 Circuit elements in the present arrangement cor
responding to similar elements of the Fig. 1 ar
ulated, for example, the amplitude-modulation
rangement are designated by similar reference
components of the derived carrier wave are re
numerals primed. In-this arrangement, there is
moved by the limiting system 23 and thus do
provided a carrier-Wave source 34 having an out
not affect the indications of the voltmeter 26,
but are derived by the detector 2%], which in this 25 put circuit which is coupled to an input circuit
modulating signal to be transmitted, the received
case is of the amplitude-detector type, are ampli
?ed by the audio-frequency ampli?er 2i, and
common to a pair of carrier-wave translating
paths I2’ and [3’. The translating path l2’ in
cludes a vacuum-tube repeater [4' having an out
are reproduced by the sound reproducer 22 in
put circuit comprising a circuit 35 tuned to the
conventional manner. When the detector 20 is
of the amplitude type, it normally is not re 30 frequency of the carrier waves of the source 34
sponsive to the phase-modulation components of
the derived carrier wave. If it does tend to de
rive some portion of the phase-modulation com
and coupled to an antenna system 10'.
The car
rier-wave translating path I3’ similarly includes
a vacuum tube repeater 16? having an output
circuit comprising a circuit 31 also tuned to the
ponent, however, the latter may be removed by
a band-rejection ?lter included in the audio 35 frequency of the carrier waves of the source 34
and coupled to an antenna system H". An os
frequency ampli?er 2| and sharply-tuned to the
cillator 21' has an output circuit coupled to the
frequency of the oscillations generated by the
primary winding 32’ of a transformer 3|’, the
oscillator 21.
transformer having a secondary winding 33’
If, on the other hand, the received carrier
wave is frequency-modulated with a signal to be 40 which is coupled‘ between a control electrode 29'
included in the vacuum tube [4' and a control
transmitted, the detector 20 is of the frequency
electrode 30’ included in the vacuum tube I6’.
detector type. In this event, the band-rejection
The carrier waves of the source 34 may be am
?lter just referred to must be included in the
audio-frequency ampli?er 2| to avoid reproduc
tion of the oscillations of unit 21. Also, unit 24
must include a band-pass ?lter in the output of
either the detector or ampli?er thereof, the ?lter
being tuned to the frequency of the oscillations
of unit 21 to suppress in the output circuit of this
unit all modulation components of the derived
carrier wave except the phase-modulation or fre
quency-modulation components due to the oscil
lations of unit 21.
From the above description of the invention, it
will be evident that the common output circuit ;
plitude-modulated, in accordance, with speech
signals to be transmitted, by a microphone 38
coupled to a modulating circuit thereof.
The carrier waves radiated by the antenna
systems I0’ and II’ may be received at a re
mote point by a receiver apparatus 39 which has
an input circuit coupled to an antenna system
40 and may include a radio-frequency ampli?er
of one or more stages, to the output circuit of
which is coupled both a phase or frequency de
tector and an amplitude detector. The ampli
tude detector is coupled through an audio-fre
of the vacuum-tube repeaters l4 and 16 comprises
quency ampli?er of one or more stages to a sound
means for combining the carrier waves translated
reproducer 4|. The phase or frequency detector
of the receiver 39 also is coupled through an
by the antenna systems Ill, II, and their asso
ciated tranlating paths, I2, 13, respectively, to
derive a carrier wave phase-modulated with the
modulation signal applied thereto from the oscil
lator 21, the degree of the phase modulation
varying with the relative orientation of the an
tenna systems 10, II' with respect to a predeter
mined point in space which, in this case, is the
location of the carrier-wave transmitting station.
The phase or frequency detector of unit “and
the voltmeter 26 comprise means for deriving and
audio-frequency ampli?er of one or more stages
to an indicating device 42 which may be a con
ventional form of alternating-current voltmeter.
Considering now the operation of this modi?ed
form of direction-?nding system, the carrier wave
of source 34 is applied to the common input cir
' cuit of the vacuum-tube repeaters l4’ and I6’ and
is translated thereby through their respective out
put circuits 35, 31, to the respective antenna sys
tems l0’ and II' for radiation. The amplitude
of the carrier waves translated by the translating
utilizing the phase-modulation components of
the carrier wave derived in the common output 70 paths [2' and I3’ is,>however, varied in’ opposite
senses by the oscillations applied from the oscil
circuit of the vacuum-tube repeaters l4 and I6
lator 21’ to the control electrodes 29' and 30' of
to provide a direction indication. It .will further
the respective vacuum-tube repeaters l4’ and I6’.
be evident that the amplitudes of the carrier
Thus, the carrier waves radiated ‘by the antenna
waves translated by the translating paths l2 and
I3 are varied cyclically and continuously by the 75 systems In’ and II’ may be received and com
:9
12,403,727
bined,.as in the input circuitof the receivingzap
paratus 39, to derive'a carrier wave 'which,'assum
ing that the carrier wave of source 34 is :not
amplitude-modulated, is of substantially con
stant amplitude but phase-modulated with ‘the
oscillations of the oscillator 21'. The degree and
sense of the phase vmodulation of the derived
carrier wave varies with the relative orientation
10
'nal also correspond to the oscillations of the
oscillator 21’ of the transmitter, but the ampli
tudes of the phase-modulation components vary,
as previously mentioned, with the relative orien
tation of the transmitter'antenna systems In’, I I’
with respect to the point of reception of the car
rier wave, as in the Fig. 2 system. These phase
modulation components are derived by the phase
detector of unit 156, are ampli?ed by the ampli
of the antenna systems Hl':and II’ with :respect
to the point in space of:receptionof the carrier 10 ?er of the latter unit and are applied to the
waves by the receiving apparatus 39. The phase
second winding 28 of voltmeter 26. There are
modulated carrier waveithus derived is ampli?ed
consequently applied to the windings 25 and '28
by the radio-frequency ampli?ersiof .the‘receiv
of the voltmeter 26 modulation signalsof the.
ing apparatus 39 and the phaseimodulation com
same frequency and wave form but differing in
ponents thereof are derived by the phase or fre
relative amplitudeand phase in accordance with
quency detector of unit 39. The modulation com
the effective phase modulation of the wave-signal
Donents are ampli?ed by the amplifier of the re
energy received by the receiver. The resultant
ceiving apparatus 39 and are applied to the volt
de?ections of voltmeter 216 thus directly indicate
meter 42 which produces a-de?ection varying with
‘the direction and sense ofdirection of-thetrans
the degree of the phase modulation of the derived 20 vmitter antenna systems ill’, II’ with respectito
phase-modulated carrier wave, thus to provide an
the point of reception of the carrier-wave-energy.
indication of the direction of the point of recep
The radiated carrier waves may alsoibezam
tion from the antenna systems l0’ and H’ of the
.plitude-z-modulated in accordance witha desired
transmitter apparatus. The direction .indication
signal to'be transmitted. Thus,rthe microphone
provided by the receiving apparatus39 and volt
38 of Fig. Zderivesa modulation-signal to v'be
meter ‘42 does not furnish an indication of the
transmitted and this signalis utilized to ampli
sense of direction of the point of reception from
tude-modulate thecarrier waves of source r34.
the transmitter apparatus.
This may be accomplished, however, ‘:by a
slightly modi?ed form of the invention wherein
the carrier wave of source 34 is amplitudemodu
lated'by the .oscillationsof unit 21'. A system of
this type is ‘shown in 'Fig. 3, which is-essentially
similar to the system of Fig. 12 and similar
elements are designated by similar reference
numerals and analogous elements by similar
reference numerals double primed. The trans
mitter of the Fig. 3 system includes an -.-am
plitude modulator 153 :having an input ‘cir
cuit coupled to the carrier-wave 'source 34
and having :the same .or an .additional input
circuit so coupled to the output circuit ofxthe
oscillator 21' that the carrier waverof source 34
is‘amplitude-modulated by the oscillations of the
latter unit. As .in the .Fig. 2 system, the oscilla
tions of the oscillator 21' are'applied with oppo
site polarities 'to the ‘vacuum tubesincluded in
After ampli?cation of I the. received .carrier 'waves
in vthe ‘radio-frequency ampli?er :of 'unit ~39, ~the
amplitude-modulation components are derived
by the amplitude-‘detector of thereceiver-BS and
are “ampli?ed by the audio-frequency ampli?er
thereof and applied to thesound reproducer'a?
for reproduction. In this connection, :itFmay-Jbe
notedv that the {amplitude-modulation; compo
nents-of thereceived-carrier waves are continu
ouslyan'd satisfactorilyreproduced while, at .the
same-.time, the meter 4-2 .indicates ‘the relative
.positionxo?the receiving apparatus from the an
tenna systems Ill’ and “'01? the transmitter.
The direction-?nding system :of the ;modi?ed
lfOI‘IIlSgshOWn in Figs. 2 .andj3 hasran important
:application ain,.p'roducing a radio-beacon beam
‘ 'bywhichraircraft-in ?ight,.carrying th'eireceiving '
apparatus 139 ‘or? 39", :may be ‘navigated along-a
desired course.
iWhile it .has been stated that ‘the "oscillations
the wave-signal translatingipaths l2’ and #3’ by
generated by ‘the oscillator .21 of Fig. 1 or the
which to control in opposite senses the amplitudes
oscillatorZl’ of [.Fig. 2 or Fig. .3_preferably.ihave'
of the modulated wave signals translated by the 60 sinusoidal wave form, it will 'be.=evident.thatithe
translating paths. There is‘ thus provided around
oscillations may have other wave forms, for'ex
the antenna system NJ’, ll’ :of the transmitter
ample, saw-ttoothtwave .form, it being only.:neces—
te?‘ectively one radiated carrier wave,'.both phase
sary'that the repeating ratios of: the'vacuum-tube
modulated and amplitude :modulated with the
repeatersitd and I6 of the .Figrlarrangement-‘or,
oscillations of oscillator 21’. No characteristic
correspondingly, the vacuum-tube ' repeatersv 14'
of the amplitude modulationis'affected by the
and i6’ o'f .thefFig, 2 arrangement, becyclically
choice of the point of reception of the radiated
and continuously varied by the oscillations :ap
carrier wave. The phase modulation, on the
plied to these .repeaters.
other hand, varies in amplitude with the radial
‘While :there have been described what are‘at
direction around the antenna system ‘from a 60 present considered to be the preferred ‘em-bodi
given reference radial direction.
ments of the invention, it willbe obvious tOithOSB
The receiver.39"'.of the Fig. 3rsystem may. in
skilled in the art that variousichanges'and modi
'clude a wave-‘signal ampli?er M having :anout
?cationszmay be :made therein ‘without departing.’
,put circuit coupled to the input circuit of ‘an
from the invention, .and itis, therefore, .aime‘diin .
amplitude detector and. ampli?er?? and also to an
the ‘appended claims to .coverzall-such changes
input circuit of Ia phase detector and ampli?er
.and modi?cations as fall within theitrue spirit
$46. The amplitude-modulation components of
and: scope of the invention.
the received wave signal, .these modulation com
‘What is ‘claimed is:
ponents corresponding torthe oscillations of the
i. A direction-?nding "system comprising, a
oscillator 21’ of the transmitter, are derived
pair of antenna systems {physically spaced .by a
bythe detector of unit 45, are suitablyzrampli?ed
value which provides a measurablephase .di?er
by ‘the ampli?er of .the latter unit, and areap
ence in at least one direction'between Wavefsig
plied to the winding 25 :of .a :zero-rcenterescale
nals JOf -a..given ‘frequency radiated- bysaid an
dynamometer-type of voltmeterxz?. Thephase
.tenn-a systems, a pair of carrier-wavetranslating
‘modulation components'of the‘received wave: sig
vpaths‘having output circuitsrindividuallylcoupled
,
2,403,727
11
repeating ratio of one of said vacuum-tube re
peaters, and means responsive to the oscillations
to said input circuit and having said given fre
of said source for varying the repeating ratio of
quency, means for varying the amplitude of the
carrier wave translated by one of said paths in
accordance with a modulation signal, and means
for varying the amplitude of the carrier wave
translated by the other of said paths in accord
ance with said modulation signal but with a pre
the other of said vacuum-tube repeaters but with
a predetermined phase displacement relative to
said ?rst-named variation to provide around said
antenna systems effectively one radiated carrier
wave phase-modulated with the oscillations of
said source, the amplitude of said phase modula
tion varying with the radial direction around
determined phase displacement relative to said
?rst-named variation to provide around said an
tenna systems eifectively one radiated carrier
wave phase-modulated with said modulation sig
said antenna systems from a given reference ra
dial direction.
5. A direction-?nding system comprising, a
pair of antenna systems physically spaced by a
value which provides a measurable phase differ
nal, the amplitude of said phase modulation
varying with the radial direction around said
antenna systems from a given reference radial
direction.
2. A direction-?nding system comprising, a
ence in at least one direction between wave sig
nals of a given frequency radiated by said an
tenna systems, a pair of vacuum-tube repeaters
pair of antenna systems physically spaced by a
value which provides a measurable phase di?er
12
to the oscillations of said source for varying the
to said antenna systems and having a common
input circuit, a source of carrier waves coupled
having output circuits individually coupled to
20
said antenna systems and having a common in
put circuit, a source of carrier waves coupled to
said input circuit and having said given fre
ence in at least one direction between wave sig
nals of a given frequency radiated by said an
tenna systems, a pair of carrier-wave translat
ing paths having output circuits individually cou
quency, a source of oscillations of sinusoidal wave
form, means responsive to the oscillations of said
source for varying the repeating ratio of one of
said vacuum-tube repeaters in accordance with
said oscillations, and means responsive to the
oscillations of said source for varying the repeat
ing ratio of the other of said vacuum-tube re
pled to said antenna systems and having a
common input circuit, a source of carrier waves
coupled to said input circuit and having said
given frequency, and means for cyclically and
continuously varying the amplitude of the car
rier wave translated by one of said paths and
for cyclically and continuously varying the am
plitude of the carrier wave translated by the
peaters in accordance with said oscillations but
with a predetermined phase displacement rela
tive to said ?rst-named variation to provide
around said antenna'systems effectively one radi
ated carrier wave phase-modulated with the os
cillations of said source, the amplitude of said
phase modulation varying with the radial direc
tion around said antenna systems from a given
other of said paths at the same frequency as
but with a predetermined phase displacement
relative to said ?rst-named cyclical variation to
provide around said antenna systems effectively
one radiated carrier wave phase-modulated with
said cyclical variation, the amplitude of said
reference radial‘ direction.
,
phase modulation varying with the radial direc
6. A direction-?nding system comprising, a
tion around said antenna system from a given 40 pair of antenna systems physically spaced by a
reference radial direction.
value which provides a measurable phase differ
3. A direction-?nding system comprising, a
ence in at least one direction between wave sig
pair of antenna systems physically spaced by a
nals of a given frequency radiated by said an
value which provides a measurable phase di?er
tenna systems, a pair of carrier-wave translating
ence in at least one direction between wave sig
paths having output circuits individually cou
nals of a given frequency radiated by said an
pled to said antenna systems and having a com
tenna systems, a pair of vacuum-tube repeaters
mon input circuit, a source of carrier waves cou
having output circuits individually coupled to
pled to said input circuit and haw'ng said given
said antenna systems and having a common in
put circuit, a source of carrier waves coupled to
frequency, a source of oscillations, and means re
said input circuit and having said given fre
quency, means for varying the repeating ratio of
varying in opposite senses the amplitudes of ‘the
sponsive to the oscillations of said source for
carrier waves translated by said paths in accord
ance with said oscillations to provide around
said antenna systems effectively one radiated
carrier wave phase-modulated with the oscilla
tions of said source, the amplitude of said phase
modulation varying with the radial direction
around said antenna systems from a given ref
one of said vacuum-tube repeaters in accordance
with a modulation signal, and means for varying
the repeating ratio of the other of said vacuum
tube repeaters in accordance with said modula
tion signal but with a predetermined phase dis
placement relative to said ?rst-named variation
to provide around said antenna systems effec
erence radial direction.
tively one radiated carrier wave phase-modulated
'7. A direction-?nding system comprising, a
pair of antenna systems physically spaced by a
value which provides a measurable phase differ
with said modulation signal, the amplitude of
said phase modulation varying with the radial
direction around said antenna systems from a
ence in at least one direction between wave sig
given reference radial direction.
4. A direction-?nding system comprising, a
pair of antenna systems physically spaced by a
value which provides a measurable phase differ
nals of a given frequency radiated by said an
tenna systems, a‘ pair of carrier-wave translat
ing paths having output circuits coupled to indi
vidual ones of said antenna systems and having a
common input circuit, a source of carrier waves
ence in at least one direction between wave sig
nals of a given frequency radiated by said an
coupled [to said input circuit, means for varying
the amplitude of the carrier wave translated by
tenna systems, a pair of vacuum-tube repeaters
having output circuits individually coupled to
one of said paths in accordance with a modula
said antenna systems and having a common in
put circuit, a source of carrier waves coupled to
tion signal, means for varying the amplitude of
the carrier Wave translated by the other of said
said input circuit and having said given fre
quency, a source of oscillations, means responsive
-
paths in accordance with said modulation signal
13
2,403,727
but with a predetermined phase displacement
relative to said ?rst-named variation to provide
around said antenna systems effectively one radi
ated carrier wave phase-modulated with said
modulation signal, the amplitude of said phase
modulation varying with the radial direction
around said antenna systems from a given ref
erence radial direction, means for receiving said
radiated phase-modulated carrier wave and re
14
the amplitude of the modulated carrier waves
translated by one of said paths in accordance
with said modulation signal, ‘means for varying
the amplitude of the modulated carrier waves
translated by the other of said paths in accord
ance with said modulation signal but with a pre
determined phase displacement relative to said
?rst-named variation to provide around said an
tenna systems effectively one radiated carrier
sponsive to the phase-modulation components 10 wave phase-modulated by said modulation sig
thereof for deriving a control eifect, and means
nals and additionally modulated by said modu
responsive to said control effect for indicating
lation signals in accordance with said ?rst type
the direction of the point of reception of said
of modulation, the amplitude of said phase mod
carrier wave with respect to said antenna sys
ulation varying with the radial direction around
tems.
_
15 said antenna systems from a given reference
8. A direction-?nding system comprising, a
radial direction, means for receiving said radi
pair of antenna systems physically spaced by a
ated carrier wave, a phase detector for deriving »
value which provides a measurable phase differ
from said received .carrier wave a ?rst signal cor
ence in at least one direction between wave sig
responding to the phase-modulation components
nals of a given frequency radiated by said an
tenna systems, a pair of carrier-wave translat
20 thereof, a second detector for deriving from said
ing paths having output circuits coupled to
ing to the modulation components of said ?rst
type of modulation, and means responsive jointly
to said signals for indicating the direction and
individual ones of said antenna systems and
having a. common input circuit, a source of car
rier waves, a source of modulation signals, means
responsive to said modulation signals for modu
lating said carrier waves with a ?rst type of mod
ulation and for applying said modulated carrier
waves to said input circuit, means for varying
received carrier wave a second signal correspond
sense of direction of the point of reception of
said carrier wave with respect to said antenna
systems.
.
ARTHUR V. LOUGHREN.
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