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B.'D._LOUGH|_IN
DIRECTION INDIQATING :DEVICE>
Filed Sept;A 15, 1944
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DIRECTION` INDI CAT'ING DEVICE
`F'iled Sept. l5, 1944
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INVENTOR
Í BERNARD D. L'OUGHLIä
BY 4)/
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Patented Dec. 31, 1946
f unire -1
29eme@
¥stares Partnr orifice
2,413,637
DIRECTÍON INDICATING DEVICE
Bernard n. Loughlin, Bayside, N. Y., assigner,
by mesne assignments, to Hazeltine Research,
inc., Chicago, Ill., a corporation of Illinois
Application September 15, 1944, Serial No. 554,233
13 Claims.
(Cl. Z50-_11)
1
2
The present invention relates to direction-indi
unevenness of the terrain surrounding the trans
mitting antennas or atmospheric fading, serious
ly impairs the accuracy of the system. Accuracy
cating systems of the type adapted for use as an
aid in the navigation of a mobile craft and, par
ticularly, to such systems of the type Which uti
lize spaced wave-signal radiators.
The majority of the prior wave-signal systems
of indication is likewise impaired by changes of
the relative intensities or phases of the wave sig
nals applied to transmitting antenna systems, or
by relative changes of the amplitudes or phases
of «the modulating signals.
It would be desirable that direction indications
utilized as an aid in navigation may be roughly
divided into several classes. One class, used
largely for marine navigation, is the radio direc
tion-finder system which employs a movable di 10 through 360 degrees, and without ambiguity, be
provided by the use of only one station of fixed
rective receiving antenna, usually of the loop or
location. It would further be desirable that the
Adcock type, by which to obtain directional in
system be one of the pulse-modulation type which
formation from signals radiated between the mo
has the important advantages that it permits the
bile craft and stations of known ñxed position.
transmitting equipment of the system to operate
In the absence of knowledge of the general po
with high peak-power output greatly exceeding
sition of the craft from one such station, as might
its average power-outputl capabilities, thus oper
occur during blind flight of any aircraft, two such
stations when suñiciently widely spaced furnish
ating with high-power gain, and additionally per
mits a transponder type of operation. In the lat
to ascertain position, free from ambiguity, by cal 20 ter mode of operation, the process by which di
rection is determined is initiated by an interrogat
culation cr by some plotting process. Where com
ing signal which is transmitted from the direc
pass bearings are not available to a mobile craft
tion-indicating staton to the station `which ra
or cannot be relied upon, at least three widely
diates the wave signals used in providing the di
-spaced stations are necessary for the ascertain
ment of position of the craft. This system has 25 rection indication. The interrogating signals
when received by the latter station initiate and
the disadvantages that it not only requires at
control its operation so that direction-indicating
least two and possibly three Widely spaced sys
signals are radiated only when interrogating sig
tems, but also that it is not in general adapted
nals are received, thus minimizing possible inter
rapidly and easily to provide desired position in
dications. Moreover, only one craft can be served 30 ference with adjacent transmitting channels used
for other purposes and increasing the element
at a time by the system.
. .
of secrecy which is of importance in military ap
The prior systems most extensively used >in
suñicient information with the aid of a compass
plications.
air-craft navigation are of the complementary~
It is an object of the present invention to pro
signal or equi-signal-locus class, employed with
predetermined deiined courses. These directional 35 vide a new and improved direction-indicatirer sys
tem which is free of one or more of the above
radio beacons, or radio “range” beacons, may be
mentioned disadvantages and limitations of prior
considered direction-indicating systems in the
systems of this type.
limited sense that the defined courses have pre
It is a further object of the invention to pro
determined fixed directional relations with a ter
restrially located radiating system. Systems of 40 vide a new and improved direction-indicating svs
tem which possesses one or more of the desirable
this character are subject to the serious limitation
characteristics mentioned above.
that they may provide indications of but a rela
It is an additional object of the invention to
tively small number of divergent courses. Addi
provide a new and improved direction-indicating
tionally, their operation is premised upon re
system the operation of which is prem-'sed on
ceived wave-signal intensities which are affected
average values of wave-signal'travel diiîerentials
by many factors, such as terrain and atmospheric
for effecting indications of direction and one
fading, with the result that this type of system is
subject to errors introduced by these extraneous
which, therefore, is not affected either by any nor
mal slow changes of intensities of received wave
factors.
Other proposed prior art systems have nu 50 signals or rapid changes of intensity of relatively
short duration.
merous disadvantages and limitations by virtue
primarily of the fact that they depend upon the
In accordance with the invention, there is pro
intensity of the received wave-signal energy to
vided in a radiant-energy system of. the type
which effects translation of a modulation signal
provide the direction indications. Thus, any fac~
tor affecting the wave-signal intensity, such as 55 over at least two space paths extending between
2,413,637
3
4
an antenna of one antenna system and indi
vidual antennas of another antenna system, a
axes having known azimuthal bearings, the
course indications provided by the system become
direction-indicating device for indicating with
azimuthal indications and will be hereinafter re
ferred to as such.
relation to a predetermined reference plane the
direction of one of the antenna systems relative
to the other. This device comprises means re
sponsive to thc modulation signals translated over
the aforementioned space 1iïlaths for developing a
pair of signals having characteristics which vary
similarly with time and a time relationship vary
ing with the relative lengths of the space paths.
The device includes means for differentially com
bining these developed signals to derive a control
signal effectively of pulse wave form and having
a pulse duration varying with the time relation
snip of the developed signals, and means respon
sive to the control signal for indicating the direc
tion of one of the aforesaid antenna systems rela
tive to the other.
For a better understanding of the present in
The direction-indicating device includes means
for selectively receiving wave signals from an
tennas il and i2. This means is coupled to a
receiving antenna system 2b and comprises two
similar wave-signal translating channels, com
ponente of the second channel corresponding to
analogous components of the first channel being
designated by similar reference numerals primed.
The first channel comprises in cascade, in the
order named, a radio-frequency amplifier 2|, an
oscillator-modulator 23 for converting~ the re
ceived wave signals to intermediate-frequency
signals, and an intermediate-frequency amplifier
23 which preferably includes at least one ampli
tilde-limiter stage for limiting to a predetermined
value the amplitude of the pulse-modulated wave
signal translated by unit 23. rl‘he output circuit
vention, together with other and further objects
thereof, reference is had to the following descrip
of unit 23 is coupled to an input circuit of a con
tion taken in connection with the accompanying
trol-signal generator 2d. The ñrst channel, com
drawings, and its scope will be pointed out in the
prising units 2l-23, inclusive, selectively receives
appended claims.
25 and translates the wave signal of transmitter I3,
Referring now to the drawings, Fig. l is a cir
while the second channel, comprising units
cuit diagram, partly schematic, of a complete di
2i’-23’, inclusive, selectively receives and trans
rection-indicating system embodying the present
lates the wave signal of transmitter I4.
The unit 2t includes a pair of input trans
in explaining the operation of the invention; and 30 formers 25 and 2li’ having primary windings cou
Figs. 4 and 5 represent direction-indicating sys
ple to the output circuits of the respective am
pliñers 25S and 23’. These transformers have
tems embodying modified forms of the inven
invention; Figs. 2 and 3 are curves used as an aid
tion.
secondary windings 25, 26’ which are tuned by
Referring now more particularly to Fig, l of
respective condensers 2l and 2l’ to provide fre
the drawings, there is represented a complete 35 quency-selective circuits 2li, 21 and 28', 21’ reso
direction-indicating system embodying the pres
nant at the nominal intermediate frequencies of
the respective ampliñers 23 and 23’.
The direction-indicating device also includes a
to a predetermined reference plane of longitude
pair of rectifier systems having individual load
which is coincident with a iixed terrestrially 40 impede-noos for deriving across the latter the
positioned antenna system of the indicating sys
modulation components of the wave signals from
tem. This arrangement thus provides azimuthal
antennas Il and l2. One rectifier system com»
prises a diode rectifier 3E) and a load resistor 3|
indications. It will be understood, however, that
therefor, these components being serially con
the invention is not so limited and the reference
nected across the frequency-selective circuit 25,
plane may, if desired, he a horizontal one in;
2l. The other rectifier system similarly corn
which case the indications then involve the aspect
prises a diode rectiñer 3G’ and a load resistor 3l'
of elevational direction. This system includes a
pair of spaced antennas i i, il? coupled to indi
which are serially connected across the fre
quency-selective circuit 2B', 2T’.
vidual ones of a pair of transmitters i3, i4 for
generating and transmitting individual ones of
The device additionally includes energy-stor
age means coupled to individual ones of the load
a pair of carrier-wave signals. Each of the
transmitters i3, iii includes a modulationr input
resistors 3l,
and responsive to the derived
circuit coupled to an output circuit of a pulse
modulation components of the received wave sig
generator l5, which. `generates a signal of periodic
nais for developing a pair of signals having char
pulse wave form. The system also includes a
acteristics'which vary similarly with time. This
second pair of spaced antennas lâ, Il coupled to
means comprises a pair of condensers 32, 32’ indi
individual ones of a pair of transmitters la' i9,
vidually connected in parallel with resistors 3l,
which also have individual modulation input cir
El ’, respectively.
cuits coupled to an output circuit of generator l5.
Means is provided for diiîerentially combining
Antennas il, l2, l5 and il? are preferably located so the signals developed by condensers 32, 32’ to de
on a Cartesian system of coordinates, passing
rive a first control signal eiîectively of pulse wave
through the four cardinal points of the compass,
form. This means comprises the control elec
and equidistant from the origin thereof, Trans
trode and cathode elements of a-Dair of’vacuum
mitters i3, is, lâ and i9 are oi the pulse-modu
tubes 3E and Sê’. The cathodes of these vacuum
lated type and have individual carrier-wave fre et tubes are connected to gro-und, whereas their con
quencies. It will be understood that the elements
trol electrodes are connected to individual ter
li-lâl, inclusive, are normally terrestrially lo
minals of the load impedances 3i, 32 and 32', 32'
cated, and that the portion of the system pres
of the respective diode rectiflers dû and 3d', these
ently to loe described is normally associated with
load impedances having a common termina1 and
a craft the direction of which is to be determined 70 the diode rectiilers being so po-led that the poten
and comprises a direction-indicating device for
tials developed acrossfthe uncommon terminals
receiving the wave signals radiated from anten
of the load impedances have the same polarity.
nas il, i2, I6 and il to indicate its direction with
A grid-leak resistor 33 is connected between the
respect to these antennas. Since the antennas
control electrode and cathode of the vacuum tube
ent invention in a particular form suitable for
providing an indication of direction with relation
il, l2, lâ and lll are ñxed and are spaced along ‘
3% to serve as a common grid-leak resistor for both
2,413,637
6
of the vacuum tubes 36 and 3S'. It may be noted
that this common grid-leak resistor may be con'
nected between ground and any point on the cir
cuit which includes the elements 3l, 32, 3|' and
32'.
verted into intermediate-frequency signals by the
units 22 and 22', amplified at intermediate fre
quency by the amplifiers 23 and 23', and applied
to the input-circuit transformers 25 and 25’ of
unit 24. It is assumed that the distance from the
antennas I2, I I to the indicating device is so great
The direction-indicating device additionally in
that the convergence of the paths of signal travel
cludes means responsive to this first control sig
from antennas I2, II to antenna 20 may be neg
nal for indicating the azimuth of the indicating
lected. Under the assumed conditions, the pulse
device relative to the antennas I I, I2. This means
includes means for developing from this control 10 modulation components of the wave signals re
ceived from the north and south transmitters I3
signal a second control signal having a char
and i4 have a relative time displacement at the
acteristic varying with the pulse duration of the
time of reception given by the relation:
first control signal. This last-mentioned means
comprises a time-constant circuit including 'a con
t=kd sin a
(1)
denser 31 connected across the output electrodes 15 where
of tube ‘36, together with a resistor 38 of relatively
d is the distance between antennas II a-nd I2,
large value connected between the anode of this
c is the angle formed by a line drawn from anten
tubey and a source of energizing potential, in
na 2U to the midpoint of the line between an
dicated as -l-B, and a similar time-constant cir
tennas I6 and I'I, and
cuit including a condenser 31’ connected across 20
1c isa constant related to the wave-signal velocit
the output electrodes of tube 36' and a resistor
and the units of measurement selected.
`
3S’ of relatively large value connected between
Similarly, the wave signals from transmitters
the anode of the latter tube and the potential>
i8 and Li are received by the east-West receiving
source +B.
The first control-signal responsive means also
system 43 and applied to control-signal generator
includes means for developing from the second
44. The modulation components of these wave
control signal a third control signal having a
signals have a relative time displacement at the
time of reception given by the relation:
characteristic varying with a characteristic of the
second control signal. The last-named means
t'=kd cos a
(2)
comprises a pair of vacuum tubes 3S, 3S', having -_
As
will
presently
be
explained
in
greater
detail,
their control electrodes coupled to respective ones
the system has such operation that control sig
of the output circuits of tubes 36 and 36', and
nals are applied to cathode-ray tube 42 having
cathode-circuit time-constant networks including
values varying with the signal-time differentials
a condenser di! and parallel-connected resistor 4i
lcd sin a and kd cos a, thus to provide direction
for the tube S9 and a condenser 49’ and parallel
indications through a BSO-degree angle and with»
connected resistor lil’ for the tube 39’. The
out ambiguity.
-anodes of tubes 39, 39' are energized from an
The manner in which the control signals just
anode-potential source, indicated as -l-B.
mentioned are derived from the received wave
In order to provide for visual directional in
signal energy will now be considered in connection
dications, the output circuit of control-signal gen
with the curves of Fig. 2 which represent the wave
erator 24 is coupled to the vertical beam-defiect
forms of voltages appearing at selected points
ing elements of a cathode-ray tube 42. rlî‘ube 42
in the direction-indicating device. Consider for
is of a conventional type and is provided with suit
able operating potentials, not shown for sim
the moment only the wave-signal modulation
45 components corresponding to a single given pulse
plicity.
of the signal of generator I5. Under the condi
It wül be seen that the units 2I-23, inclusive,
tions heretofore assumed, the wave-signal modu
2I’--23’, inclusive, and 26 are adapted to receive
wave-signal energy from the north-south an
lation components from the north transmitter I3
tennas II-I2, so that they may be referred to
are the first ones to arrive at the direction-in
50 dicating device. These components are trans
as the “north-south receiving system.”
The` direction-indicating device further in
lated through receiver units 2I-23, inclusive, to
the signal generator 24. The received Wave sig
cludes an east-west receiving system d3, which has
nal is of the pulse-modulation type and is pref
an input circuit coupled to the common receiving
erably limited to a substantially constant am
antenna 2G. Receiving system @3, which includes
plitude by the amplitude-limiter stage or stages
circuit elements similar to those of the north
south receiving system, is adapted to receive and
included in the ampliñer 23, thus to reduce the
effect of undesirable changes of received wave
to translate tol an associated control-signal gen
erator 44 wave-signal energy from antennas I6,
signal intensity. The received Wave signal is
translated by the frequency-selective circuit 26,
I1. Generator 4d comprises elements similar to
those included in unit 2d and a similar circuit ar 60 2l and is applied to the diode rectifier 3Il~ which
rangement. The output circuit of generator 44 is
derives the modulation components thereof. If
coupled to the horizontal beam-deñecting ele
the condenser 32 were disconnected from the load
ments of tube 42.
resistor 3|, the derived pulse-modulation compo
Considering now the operation of the indicat
nents would produce across the latter resistor at
ing system just described, the wave signals of the 65 time t1, Fig. 2, a potential pulse having the wave
transmitters I3, i4, IB and i9 are sîmultaneously
form represented by curve A of Fig. 2. With the
modulated by a signal of periodic-pulse wave form
condenser 32 connected across the resistor 3l,
generated by the generator I5, thus to radiate
however, the derived pulse rapidly charges the
pulse-modulated wave signals distinguishable in
latter during the pulse interval. At the termina
frequency. Assume that the direction-indicating 70 tion of the pulse, condenser 32 discharges slowly
deviceis inthe north-east quadrant. The sig
through the relatively large resistor 3l to develop
nals from transmitters i3 and i 4, hereinafter re
ferred to as the "north” and “south” signals, re
thereacross a signal having an exponential por
spective‘y, are selectively received by the respec
tiveradio-frequency amplifiers 2| and 2|', con
tion, as represented by curve B.
,
This developed signal is applied between the
75 control electrodes of tubes 36 and 36’ and has
2,413,637
8
positive polarity with respect to the control elec
trode of tube 35. The control electrode of tube
35 becomes conductive as soon as it is biased only
slightly positive with respect to its cathode. Fur
ther, the potential drop between the control elec
trode and cathode of tube 36 then becomes so
small that the control electrode cannot be biased
ciated cathode.
It will be apparent that the
maximum value of the time interval ti-tz occurs
when the indicating device is either due south
or due north of -the antennas Il, I2. The de
crease of amplitude of the signal vdeveloped across
the condenser 32, due to the discharge of the
latter through the resistor 3 l, is sufficiently small
more than a small fraction of a volt positive with
even during the longest possible interval ti-ta
relation to the cathode. Consequently, the con
last mentioned, that the signals developed across
trol electrode of tube 36 is maintained at sub 10 the condensers 32 and 32' have approximately
stantially ground potential, which is the potential
equal amplitudes at time tz. The signal de
of the cathode of this tube, during the applica
veloped across the condenser 32’ thus effectively
tion thereto of the signal developed across the
condenser 32 so that the signal is applied With
terminates the signal developed across the con
denser 32 so that there is applied to the control
substantially full amplitude and negative polarity 15 electrode of tube 36’ a potential or control signal
between thee control electrode and cathode of
of pulse wave form, represented by curve F, hav
vacuum tube 35', as represented by curve C. In
ing a pulse duration varying with the time in
this regard, it should be noted that in the absence
terval ti-ta Expressed in another manner, the
of any received wave-signal energy, the control
pulse duration of the control signal resulting
electrodes of vacuum tubes 3@ and 36’ have sub
from the differential combination of the signals
stantially zero bias with respect to their asso
developed across the condensers 32 and 32' has a
ciated cathodes and both of these tubes are fully
value varying with lcd sin a.
conductive under this condition. The resistors
The control signal applied to the control elec
38 and 38’ in the anode circuits of the latter have
trode of vacuum tube 36' renders the latter non
values suiiiciently high that the potential drops
conductive during the pulse interval of the signal,
produced across these resistors by the zero-bias
space currents of tubes 36 and 3G' are so large
that only a small positive potential is actually
.thus tending to increase the anode potential of
this tube as previously mentioned. The anode
potential does not increase at once, however, since
applied to the anodes of these tubes. Consequent
the charge of the condenser 3l’ must correspond
ingly increase and the latter can only charge
through the resistor 3S' of relatively large value.
ly,
ie signal derived across the condenser 32 is
not repeated with any substantial amplitude to
the output circuit of the tube 35, due to the low
anode potential of the latter, but is repeated to
the output circuit of the tube 36' since it causes
the control electrode of this tube to become more
negative with relation to its associated cathode,
thus reducing the space current of tube 35’ and
thereby tending to increase its anode potential.
In practice, the amplitude of the signal developed
across the condenser 32 preferably is sufliciently
large that it causes the control electrode of vacu
um tube 30’ to bias the latter to or beyond anode
current cutoff so that undesirable changes of
amplitude of the signal, as might be caused by
undesirable changes of received Wave-signal in
tensity, are not eifective to vary the amplitude of
the signal developed in the output circuit of the
tube 3%’.
At some later time, for example at time t2 of
Fig. 2, the Wave signal radiated by the antenna '50
The circuit parameters are so selected that the
time constant of the condenser 3l’ and resistor
38' is long compared to the pulse duration of the
control signal applied to the control electrode of
vacuum tube 3S’.
At the termination of a pulse
of this control signal, condenser 3l' discharges
rapidly through vacuum tube 3iì’ which, as pre
viously explained, again becomes conductive at
the termination of the pulse. There is thus de
veloped across the condenser 3l' a second control
signal having positive polarity with respect to
ground and having an approximately triangular
pulse wave form, as represented by curve G. This
second control signal has an amplitude varying
substantially only With the pulse duration of the
ñrst control signal applied to the control elec
trode of tube 36', and thus has an amplitude pro
portional to lcd sin a.
This second control signal is applied with posi
tive polarity to the control electrode of tube 39'.
l2 of the south transmitter I4 is received by the
indicating device; is translated through the re
ceiver units 2I’--23’, inclusive; is limited to a sub
tively large value, of the order of one megohm,
stantially constant vamplitude by .the amplitude
and the cathode condenser ¿lû’ a capacitance only
The cathode resistor 4l' of this tube has a rela
limiter stage of the unit 23'; and is applied 55 large enough to provide therewith a time con
through the frequency-selective circuits 26', 2l’
stant three or four times the period of the second
control signal. The circuit parameters are thus
to the diode rectiñer Sil’ which derives the modu
lation components thereof. Were it not for the
so chosen that, under no-signal conditions, con
denser iiß' is charged to such a potential that the
condenser 32', there would thus be developed
across the resistor 3l' a potential of pulse Wave 60 cathode of >tube 39' is more positive than its con
form, as represented by curve D of Fig, 2. The
trol electrode by an amount almost sufficient;> to
condenser 32', however, rapidly charges >during
bias tube 39’ to anode current cutoff. Upon the
the pulse and slowly discharges exponentially
application of the second control signal, tube 39’
through resistor 3l' at the termination of the
becomes more conductive during the first several
pulse, lthus to develop thereacross a signal, rep 65 pulses thereof and condenser dil' receives an in
resented by curve E, having an exponential por
crement of charge to raise the cathode potential
tion similar to that of the signal developed across
above the maximum amplitude of the second
control signal by a value equal approximately to
the condenser 32 associated with the diode recti
fier 3i?. The signal developed across 4the con
>the anode current cutoff potential of tube Sil'. As
denser 32’ is applied between the control elec 70 indicated by curve H of Fig, 3, ythe condenser 40’
trodes of vacuum> tubes 36 and 36', but has a
charges rapidly during each pulse G' of the sec
polarity opposite to that of the signal developed
ond control signal and discharges relatively slow
ly through the cathode resistor 4|'. A third uni
-to restore the potential of the control electrode
directional control signal thus is developed in the
of tube 3E' to the same potential as its asso 75 output or cathode circuit of tube 39', the magni
across the condenser 32 and thus one which tends
25.413,63??
`tu'de of this control signal varying with the am
plitude of the second control signal and thus
being proportional to kd sin a.
.
This third control signal is applied to the ver
tical deñecting electrodes of tube 42 to deflect the
beam thereof in the Vertical direction, indicated
in Fig. 1, by an amount proportional to lcd sin a.
It may be noted in passing that the polarity of
this control signal, considered with relation tol a
selected one of the vertical deilecting electrodes
of tube 42, is the same as long as the indicating
device is positioned in either the north-east or
north-west quadrants since corresponding modu
lation components of the Wave signal of antenna
II then always precede those of the wave signal
I3, I4, _I8 and I9 coupled to the antenna systems
Il, lf2, I B and I?, these elements normally com
prising a terrestrially located system, operating
in conjunction-_with the direction-indicating de
vice comprising elements Qi'B-sßß, inclusive, 42, 43
and 44 normally carried by a craft the direction
of which is to be indicated. It will be apparent,
however, that an equally useful form of direction
indicating system embodying the invention is, as
shown in Fig. 4, one in which the spaced an
tennas Ii,'!2, it rand I ï, terrestrially located, are
coupled to individual ones of the input circuits
of the plurality of Wave-signal translating chan
nels 45, 45 of the receiving system and in which
the transmitting system is carried by the craft
and includes a single nondirective antenna 47
of antenna I2.
»
coupled to a single transmitter 48 having an
Similarly, wave signals from antennas I6,4 vI‘l
amplitude-modulation input circuit coupled to a
are received by the east-west receiving system 43
pulse generator I5.> In this form of indicating
and applied to control-signal generator 44. .Gen
erator 44 derives the modulation components of 20 system, the transmitter operates 'at only one
wave-signalirequency and- the several Wave
the received wave signals and responds thereto
signal translating channel-s of the receiving sys
to generate a control signal having a magnitude
tem are tuned-to receive wave signals of this
proportional to lcd cos a.. This control signal is
frequency, Indications of the direction of the
applied to the horizontal beam-deiiecting elec
trodes of tube 42v to deflect the beam thereof in 25 craft are here providedby the indicator 42 at the
the horizontal direction as indicated in Fig. l. ` ground installation. An additionally modiñed
form of this‘system, >shown in Fig. 5, is one in
It may again be noted in passing that the polarity
of this control signal considered relative to the
which‘the single transmitter 48 is terrestrially
located and the spaced antennas and receiving
horizontal deilecting electrodes is the same
¿ system 49 are carried by the craft, thus to provide
Whether the indicating device be inthe north
a “homing” type of indicating system.
east or south-east quadrants since corresponding
‘ From the above description of the invention,
modulation components of antenna I6 then pre
it will be apparent that the direction-indicating
cede those of antenna I'I.
_
system is of the radiant-energy type which effects
The two control signals thus applied to the
translation of a modulation signal or” periodic
deflecting electrodes of tube 42 ‘simultaneously
pulse’wave form over at least two space paths
deflect the beam of the tube so that there ap
extending'between an antenna of one antenna
pears on the screen thereof a luminous spot, the
system and individual spaced antennas of another
angular position of which indicates the direction
antenna system. Further, it will be apparent that
of the indicating device with relation to the
the indicating device is responsive to the modu
spaced antennas II, I2, I6 and I1. The screen
l'ation'signals translated over these space paths
of tube 42 may therefore be calibrated in terms
for developing a pair of signals having character
of direction.
,
vIt will be apparent from the foregoing descrip
istics which vary similarly with time and which
tion of the system operation that when the di
havea time relationship varying with the rela
rection-indicating device is in the south-east 45 tive lengths of the space paths, thus to permit
quadrant with relation to the spaced antennas,
the differential combination of the developed
the first modulation-signal components to arrive
signals to derive a control signal which is utilized
at the indicating device are those of the antennaJ
in effecting the desired direction indication.
I2. The iirst developed signal in point >of time
~ A ’direction-indicating device embodying the
consequently i-s that produced by condenser 32,’. 50 invention-:has the advantage that it is adapted
The second signal derived in point of time is that
' for operation in a direction-indicating system of
across the condenser 32 and this signal is diiîer
the pulse-modulation type and thus possesses all
entially combined with the ñrst developed signal
of> the'advantages characteristic of pulse-modu
in the input circuit of tubes 36 and 36' to derive
lation- operation; namely, the operation of trans
a control signal of negative polarity as applied 5.54 mittin‘g> equipment of the system with high power
to the vcontrol electrode of tube 36. Tube '35'
gain 'and the operation of the system as a whole
does not repeat this signal, but tubes 36 'and 39V
as a transponder type of system. hereinbeîore
and their associated circuits then function in
mentioned. An indicating device embodying the
similar manner to that previously described in
invention has the additional advantage that its
connection with tubes 36’ and 39’ to develop al 60 operation is not detrimentallyaffected by rela
third control signal having, with relation to the
tively slow changes of received wave-signal in
vertical deñecting electrodes of tube 42, a polarity
tensity, Such as might occur during conditions of
opposite to that developed under the conditions
severe atmospheric fading and the like. Nor is its
first assumed. This control signal thus produces
operation 'affected by Arelatively rapid changes of
a vertical component of deflection of the electron
received wave-signal intensity such as might oc
beam of tube 42 in a direction opposite to that
cur- by virtue of ymultiple paths of transmission
hereinbefore described.
' or reception, or both in the transponder type'of
Further, it will now be apparent .that when the
operation, and to a. rapid change in the character
indicating device is in a north-West or south-west
of vsuch multiple paths due to relative movement
quadrant, control-signal generator 44 is effective 70 of the indicating device and the transmitting
to produce a horizontal component of deflection
equipment, as during the course of flight of an
of the beam of tube 42 in a horizontal direction>
aircraft. The lack of sensitivity of the indicat
ing device to` relatively slow changes of received
opposite to that hereinbefore described. f 1 Y
The >direction-indicating system has been- de_
wave-signal _intensity is due of course, to the lim
scribed as` including a plurality orv t_ransnriitters_VV
iting action provided by the units 23 and 23’ and
2,413,637
11
12
to the operation of tubes 36 and 36’. The lack
of sensitivity of the indicating device to rela
tively rapid changes of Wave-signal intensity is
bining said developed signals to derive a control
signal effectively of pulse wave form and having
a. pulse duration varying with the time relation
due to the long time constant of the elements
ships yof said developed signals, and means re
all, ¿il and 4B', 4|’ in the cathode circuits of
sponsive to said control signal for indicating said
the respective vacuum tubes 39 and 3S’ which
direction.
are sumciently long that the potentials developed
4. In a radiant-energy system of the type which
thereacross vary only with the average values
effects translation of a modulation signal over
of amplitude of the control signal applied to the
at least two space paths extending between an
latter tubes.
10 antenna of one antenna system and individual
While there have been described what are at
spaced antennas of another antenna system, a
present considered to be the preferred embodi
direction-indicating device for indicating with re
ments of this invention, it will be obvious to those
lation to a predetermined reference plane the
skilled in the art that various changes and mod
direction of one of said antenna systems relative
ifications may be made therein without depart 15 to the other comprising, means responsive to the
ing from the invention, and it is, therefore aimed
modulation signals translated over said space
to cover all such changes and modiñcations as
paths for developing a pair of signals having
fall within the true spirit and scope of the in
characteristics which vary similarly with time
vention.
and a time relationship varying with the relative
What is claimed is:
lengths of said space paths, means for diiîeren
l. In a radiant-energy system of the type which
tially combining said developed signals to derive
eiTects translation of a modulation signal over at
' a control signal effectively of pulse wave form and
least two space paths extending between an an
having a pulse duration varying with the time re
tenna of one antenna system and individual
lationships of said developed signals, means for
spaced antennas of another antenna system, a 25 developing from said control signal a second con
direction-indicating device for indicating with re
trol signal having a characteristic varying with
lation to a predetermined reference plane the
the pulse duration' of said first control signal,
direction of one of said antenna systems relative
and means responsive to said second control sig
to the other comprising, means responsive to the
nal for indicating said direction.
modulation signals translated over said space
5. In a radiant-energy system of the type
paths for developing a pair of signals having 30
which effects translation of a modulation signal
characteristics which vary similarly with time
over at least two space paths extending between
and a time relationship varying with the relative
lengths of said space paths. means for differen
an antenna of one antenna system and individual
spaced antennas of another antenna system, a
a control signal eiîectively of pulse Wave form 35 direction-indicating device for indicating with
tially combining said developed signals to derive
relation to a predetermined reference plane the
and having a pulse duration varying with the
direction oi' one of said antenna systems relative
time relationships of said developed signals, and
to the other comprising, means responsive to the
means responsive to said control signal for indi
modulation Isignals translated over said space
cating said direction.
2. In a radiant-energy system of the type which 40 paths for developing a pair of signals having
characteristics which vary similarly with time
eiîects translation of a modulation signal over at
and a time relationship varying with the rela
least two space paths extending between an an- .
tenna of one antenna system and individual
tive lengths of said space paths, means for dif
ferentially combining said developed signals to
spaced antennas of another antenna system, a 45
derive a control signal effectively of pulse wave
direction-indicating device for indicating with
relation to a predetermined- reference plane the
direction of one of said antenna systems relative
to the other comprising, means responsive to the
modulation signals translated over said space
paths for developing a pair of signals having
characteristics which vary similarly with time
and a time relationship varying with the relative
lengths of said space paths, means for differen
tially combining said developed signals to derive
form and having a pulse duration varying with
the time relationships of said developed signals,
means for developing from said control signal a
second control signal having an amplitude vary
ing _with the pulse duration of said iirst control
signal, and means responsive to the amplitude
of said second control signal for indicating said
direction.
6. In a radiant-energy system cf the type
which effects translation of a modulation signal
over at least two space paths extending between
an antenna of one antenna system and individual
spaced antennas of another antenna system, a
a control signal of approximately rectangular
pulse wave form having a pulse duration varying
with the time relationships of said developed sig
nals, and means responsive to said control signal
direction-indicating device for indicating with
for indicating said direction.
60 relation to a predetermined reference plane the
3. In a radiant-energy system of the type which
direction of one of said antenna systems rela
eiîects translation of a modulation signal over at
tive to the other comprising, means responsive
least two space paths extending between an
to the modulation signals translated over said
antenna of one antenna system and individual
space paths for developing a pair of signals hav
spaced antennas of another antenna system, a 65 ing characteristics which vary similarlär with
direction-indicating device for indicating with re
time and a time relationship varying with the
lation to a predetermined reference plane the di
relative lengths of said space paths, means for
rection of one of said antenna systems relative to
differentially combining said developed signals
the other comprising, means responsive to the
to derive a control signal effectively of pulse
modulation signals translated over said space 70 waveV form and having a pulse duration varying
paths for developing a pair of signals of approxi
mately saw-tooth wave form having amplitudes
which vary similarly with time and having a time
relationship varying with the relative lengths of
said space pathameans for differentially com
with the time relationships of said developed
signals, means forv developing from said control
signal a second control signal of approximately
triangular-pulse wave form having a character
istic varying with the pulse duration of said first
2,413,637
13
14
control signal, and means responsive >to said
second control signal for indicating said direc
tion.
7. In a radiant-energy. system of the type
which effects translation of a modulation signal
over at least two space path-s extending between
eating the direction of said indicating device
relative to >said spaced antennas.,
an antenna of one antenna system and indi
vidual spaced antennas of another antenna sys
tem, a direction-indicating device for indicat
ing with relation to a predetermined reference l()
, plane the direction of one of said antenna sys
tems relative to the other comprising, means re
sponsive to the modulation signals translated
over Isaid space paths for developing a pair of
signals having characteristics which vary simi
larly with time and a time relationship varying
with the relative lengths of said space paths,
means for differentially combining said devel
oped signals to derive a control signal eiTectively
of pulse wave form and having a pulse duration
varying with’the time relationships of said de
veloped signals, means for developing from said
control signal a second control signal having an
amplitude varying with the pulse duration of
said first control signal, means for developing
from Said second control signal a unidirectional
control potential having a magnitude varying
with the amplitude of said second control sig
nal, and means responsive to said unidirectional
potential for indicating said direction.
8. In an azimuth-indicating system of the
type including at least one transmitter and a
pair of spaced antennas for transmitting indi
vidual ones of a pair of wave signals modulated
l0. In a direction-indicating system of the type
including at least one transmitter and a pair of
spaced antennas for transmitting individual ones
of a pair of wave signals modulated by individual
modulation signals- having a determinable time
relation therebetween, a direction-indicating.de
-vice for receiving said Wave signals to indicate
with relation to a predetermined reference plane
its direction with respect to said antennas com
prising, means‘for selectively receiving said wave
signals and for deriving the modulation corn
ponents thereof, means responsive to said derived
modulation components for developing a pair oi
signals having characteristics Which vary simi
larly with time and a time relationship varying
with the relative times of reception oi” the modu
lation components of said received wave signals,
means for differentially combining said developed
signals to derive a control signal effectively oi
pulse-wave form having a pulse duration vary
ing with the time relationships of said developed
signals, and means responsive to said control sig
nal for indicating the direction of said indicat
ing device relative to said spaced antennas.
11. In a direction-indicating system of the type
including at least one transmitter and a pair of
spaced antennas for transmitting individual ones
of a pair of wave signals modulated by individual
modulation signals having a determinable time
relation therebetween, a directioneindicating de
vice for receiving> said wave signals to indicate
with relation to a predetermined reference plane
its direction with respect to said antennas com
prising, means for selectively receiving said wave
signals and for deriving the modulation com
by individual modulation signals having a de-'
terminable time relation therebetween, a direc
tion-indicating device for receiving said Wave
ponents thereof, energy-storage means responsive
signals to indicate with relation to a predeter
to said derived modulation components for de
mined reference plane its direction with respect
veloping a pair of signals of approximately saw
to said antennas comprising, means for selec
tooth Wave form having amplitudes which vary
tively receiving said wave signals and responsive
similarly with time and a time relationship vary
to the modulation components there-of for de
ing with the relative times of reception of the
veloping a pair of Isignals having characteristics
modulation components of said -received. wave
which vary similarly with time and a time re
lationship Varying with the relative times of 45 signals, means for differentially combining said
developed signals to derive a control signal effec
reception of the modulation components of said
tively of pulse Wave form having a pulse dura
received wave signals, means for differentially
-tion varying with the time relationships of said
combining said developed signals to derive a con
developed signals, and means responsive to said
trol signal eiîectively of pulse wave form having
a pulse duration varying with the time relation 50 control signal for indicating the direction of said
indicating device relative t0 said spaced antennas.
ships of said developed signals, and means re
l2. In a direction-indicating system of the type
sponsive to said control signal for indicating the
including at least one transmitter and a pair of
direction of said indicating device relative to said
spaced antennas for transmitting individual ones
spaced antennas.
9. In a direction-indicating system of the type 55 of a pair of wave signals modulated by individual
modulation signals having a determinable time
including at least one transmitter and a pair of
relation therebetween, a direction-indicating de
spaced antennas for transmitting individual ones
vice for receiving said Wave signals to indicate
of a pair of wave signals modulated by individual
ith relation to a predetermined reference plane
modulation signals having a determinable time
relation therebetween, a direction-indicating de 60 its direction with respect to said antennas com
prising, means for selectively receiving said Wave
vice for receiving said wave signals to indicate
signals, a pair of rectifier'> systems including in
with relation to a predetermined reference plane
dividual load impedances for deriving across said
its direction with respect to said antennas com
load impedances the modulation components of
prising, means for selectively receiving said wave
signals and for deriving from the modulation 65 individual ones of said wave signals, a pair of
energy-storage devices coupled to individual ones
components thereof a pair of signals having
of said load impedances for deriving from said
characteristics which vary similarly with time
modulation components a pair of signals having
and a time relationship varying with the relative
times of reception of the mo-dulation components
characteristics which vary similarly with time
of said received wave signals, means for differ 70 and a time relationship varying with the relative
entially combining said developed signals to de
times of reception oi the modulation components
rive a control signal eiîectively of pulse wave
of said received wave signals, means for differ
entially combining said developed signals to de
form having a pulse duration varying with the
time relationships of said developed signals, and
rive a control signal eiîectively of pulse wave
means responsive to said control signal for indi 75 form havingl a pulse duration varying with the
22,413,631
I5
I6
time relationships of said developed signals, and
time and a time relationship varying with the
means responsive to- said control signal for indi
eating the direction of said indicating device
relative to said spaced antennas.
13. In a direction-indicating system of the type
relative times of reception of the modulation
components of said received Wave signals, said
means including a pair of serially-connected out
put circuits to which individual ones of said de.
veloped signals are applied, a pair of vacuum
.
including at least one transmitter and va pair of
spaced antennas for transmitting individual ones
tubes having- input electrodes al1 coupled in series
of a pair of wave signals modulated by individual
relation across said output circuits to derive by
modulation signals having a determinable time
differential combination of said developed sig
relation therebetween, a direction-indicating de 10 nais a control signal effectively of pulse wave
vice fer receiving said wave signals to indicate
form having a pulse duration varying with the n
with relation to a predetermined reference plane
time` relationships of said developed signals, and
its direction with respect to said antennas com
meansA responsive to said control .signal for in~
prising, means for selectively receiving said wave
dicating the direction of said indicating device
signals and responsive to the modulation corn lo relative to said spaced antennas.
ponents thereof for developing> a pair of signals
having characteristics which vary similarly with
BERNARD D. LOUGHLIN.
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