1. No category

Nov. 29, 1949
2,489,270
E. COLE
DIRECTION FINDER SYSTEM
Filed Jan. 4, 1947
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A
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INVENTOR.
EUGENE 00L É
BY
.
M4
A TTORNEY
2,489,270
Patented Nov. 29, 1949
UNITED STATES PATENT OFFICE
2,489,270
DIRECTION FINDER SYSTEM
Eugene Cole, Long Island, N. Y., assignor to Fed
eral Telecommunications Labs. Inc., New York,
N. Y., a corporation of Delaware
Y Application January 4, 1947, Serial No. 720,155
10 Claims. (Cl. 343-117)
1
This invention relates to automatic indicating
direction finders, and particularly the type pro
viding control of the amplitude of the sense volt
age during bearing seeking operation.
Direction finders of the type using rotating
loop antennas or ñxed Adcock antenna arrays
are well known. In order to resolve the 180°
sense ambiguity which is commonly associated
with the use of these antennas, a sense anten
2
modulating voltages are applied in phase oppo~
sition through transformer 4 to the secondary
control elements 5 and 6 of tubes 2 and 3 re
spectively. The radio frequency voltages from
the radio direction ñnder loop 'I are applied, in
phase opposition, to the primary control elements
8 and 9 of tubes 2 and 3 respectively. The plates
of tubes 2 and 3 are coupled in parallel such that
their plate currents are additive and connected
na, usually of the vertical omni-directional type, 10 to a common load I0. Under these conditions
a carrier suppressed modulated wave is produced.
is provided. In one instance employing a fixed
The voltages developed across the load I0 are
Adcock array having an omni-directional recep
then passed to a conventional receiver II where
tion pattern, a sense antenna is adapted to be
a tone, preferably audible is produced. The fre
yswitched in to the bearing translating device for
altering the omni-directional pattern to a cardi 15 quency of this tone will be twice the frequency
of the low frequency oscillator modulator I.
oid shaped pattern. The use of the cardioid
An amplifier l2 is also connected to the com
shaped pattern during bearing seeking operation
mon load I Il. The grid voltage of amplifier I2
enables the resolving of the 180° sense ambiguity
is supplied by the sense antenna I3 which is
of this system.
coupled
to the primary control element I4. The
20
One of the objects of this invention is to pro
sense antenna voltage, and the loop voltage de
vide an improved sensing system for direction
veloped across the loop tuning condensers I5 and
ñnders and more particularly one which is auto
I6 will normally be in phase or out of phase de
matic in operation.
pendent on which end of the loop is being con
Another object of this invention is to provide
automatic means for controlling the sense volt 25 sidered, and therefore affords means for resolv
ing the 180° sense ambiguity.
age particularly its magnitude used in resolv
For convenience it is assumed that tubes 2, 3
ing 180° sense ambiguity of direction finder sys
and I2 have equal amplification for the radio
tems.
frequency voltages. Now if the sense voltage is
Another related object of this invention is to
provide automatic means for improving the sen 30 equal to or greater than the loop voltage, the
voltage being fed to the receiver will be the con
sitivity of the direction finder about the zero or
ventional amplitude modulated wave enabling
null indication.
the resolving of sense ambiguity. The tone and
In a preferred embodiment of the present in
the output of the receiver will now be of the
vention low frequency signals are separately
mixed with the signals received from a loop an 35 same frequency as the modulator I.
tenna and a sense antenna.
Means are further
provided for using the low frequency signals
Expressing these relations:
The involtage induced in the loop is
after detection in a radio direction finder re
EL=h cos 0 (sin wit)
ceiver coupled to the antenna system for con
trolling the sense voltage applied to the bearing 40 where
resolving system.
h equals the effective height of the loop;
The above mentioned and other features and
0=angle of arrival of electromagnetic wave;
objects of this invention will become more ap
sin wt=arriving wave;
parent and the invention itself, though not
necessarily del-ined by said feature and objects, 45 The voltages appearing at 8 and 9 across the
tuning condensers I5 and I6 are:
will be best understood by reference to the fol
lowing descriptìon of an embodiment of the in
vention taken in connection with the single fig
ure of the drawing, wherein there is shown a
The voltage induced in the vertical or sense
block circuit diagram of an automatic direction 50
antenna I3 is
ñnder sense control system employing modula
tion and embodying the invention.
The single figure shows a low frequency oscil
lator I arranged to supply voltage to a pair of
radio frequency modulators 2 and ,3,
E13=A2h/2 sin wit
Replacing the expressions A171/ 2 and Aan/2 with
These 55 constants V1 and V2 respectively, the contribu
2,489,270
3
tion of tubes 2, 3, and 4 to the load I0 for a modu
lating voltage of sin (wzt) and _sin (wat) is
E2=V3 sin w2lÍ(V1 COS 0 sin wit)
4
and audio reproducer are of the same order, the
modulation products produced by the loop modu
lators may be reduced by 20 db. or more while
maintaining the same signal to noise ratio at the
» indicator as exists in the reproducer.
The contribution to the receiver I I is
If a switch
23 located in the coupling network between said
diode I8 and the said controlconnection, is closed,
this direction finder automatic volume control
action may be eliminated, as by short-circuit
10 `:thereby making it an optional feature in an auto
This is the expression for a conventional .ampli
tude modulated wave.
maximum when
The modulation will be
-g-2= ViVg cos 0 (100% modulated Wave)
Where V1, V2 are constants as specified above and
V3 is a constant dependent upon E2 and E3.
matic direction finder.
While Iïhave described above the principles of
_my invention in connection with specific appa
ratus >and kparticular modifications thereof, it is
to be .clearly :understood that this description is
made only by way of example and not as a limita
tion of the scope of ‘my invention.
1. A radio direction îi'lnder having means to
Under normal operational conditions the maxi
mum amplitude of the modulation component 20 receive component energies of directional and
omni-directional patterns and to produce there
attainable at rthe receiver output is proportional
from `a resultant energy reception pattern for
tothe cosine of the angle of arrival 0. This means
determining the bearing of received .radiant en
that a variation in vamplitude of zero to some
ergy, comprising means to derive from said re
other arbitrary value exists. In order to‘sharpen
the indication about the >zero or null-position,
some sort .of limiting action 'is desirable. If the
25 sultant a control energy and ~means for applying
said control .energy to the .means for receiving
the energy of .one .of said components whereby
indicator operationis confined so that >it responds
the directivity of .said resultant pattern is con
only .to signals of the samefrequency as oscillator
1_, this limiting action can be arranged. In this 30 tinuously varied :as said bearing is approached.
2. In a >radio .direction finder .system of the
connection there is .provided an isolating ampli
type »comprising an `effectively.rotating directional
iler ,ITI .coupled to a diode detector I8 through `a
antenna and a sense antenna, a signal source of
narrow .band-pass Afilter .L9 designed to pass the
given frequency, means for .mixing signals from
frequency of oscillator I. The diode I5 provides
said source and the electrical signals received by
negative voltage .proportional to the signal ampli
said >directional antenna, means .for combining
tude, The gain of tube I2, preferably of the
said mixed signals with the signals from said
variablemu type pentode, -is controlled by apply
sense-antenna, >means Ífor demodulatingsaid com
ing .the potential from diode I8 to the .primary
bined signals, means for translating Ysaid demod
control element -I4 through connection 2i).
ulated signals to obtain the .direction of received
-As the loop becomes oriented -to the null or zero
.indication of the incoming radio frequency sig
nal the negative voltage applied to the control
electrical signals, ymeans for producing a bias sig~
nal corresponding to the amplitude of said de
modulated signals, said bias signalcontrolling the
element I4 of .tube I2 is .decreased proportion
relative intensities of :the signals from said di
ately„resultin_g ina greater .amplification of the
rectional and sense antennas whereby the sensi
sense voltage used for .mixing with the loop volt 45 tivity of said translating means is increased about
:ages .across the -load l0. This results in produc
.the null `position .of the combined antenna recep
`ing steeper slope to the null portion of .the Ydirec
tion pattern.
tion .finder reception pattern signals which are
3. A radio direction ñnder system comprising
.applied to receiver VI-I and results .in a more vpre
an effectively rotating -directional antenna, a
cise bearing indication. As .the direc-tion finder 50 sense antenna, a Ilovv `frequency signal source,
.antenna system approaches the bearing, the in
means for mixing said low frequency signals and
dication is sharpened :about .the null position.
the electrical signals `received by said directional
The input >to .the detector |-8 is :also passed to
antenna, means for combining the signal received
a control circuit 2|, zand may be .used for con
by said sense antenna> and said mixed signals,
trolling the orientation Lof loop antenna ll. This 55 mea-ns for d-emodulating said combined signals,
control can .take several forms, vas >for example,
means for deriving -from »said demodulated signal
a control energy ‘for effectively controlling the
rotation of said directional antenna, means for
rection finder wherein the amplitude of the signal
producing a bias signal corresponding to the am
as received in the control circuit 2! controls 60 plitude of said demodulated signals, means re
motor 24 for rotating the loop 1.
sponsive to said bias signal -for controlling the
If the control voltage from .the output of the
.relative ‘intensity of said directional and sense
a visual indicator 23, an audio indicator or a
control circuit of an :automatic null-seeking di
diode detector I8 is only applied to the primary
.control .element of .only tubes 2 and 3 simulta
neously through connection 22, a `further advan
tage is attained. It is then possible to operate
a bearing indicator in the control circuit of an
automatic direction finder lsystem Without appre
ciably impairing the audibility of modulated sig
*antenna signals before combining whereby the
sensitivity of said control means is increased
65 .about the null position fof vthe antenna reception
pattern.
4. A radio direction finder system comprising
.an effectively rotating directive antenna, a sense
antenna, a loW frequency signal source, means
Since the indicator operates von a fixed 70 .for mixing said 10W frequency signals and the
frequency, the sensitivity of the indication may
electrical signals received by said directional an
be increased a factor proportional to the ratio of
tenna, means for combining the signal received
.the audio response band width to the indicator
by said .sense antenna and .said mixed signals,
nals.
.channel band width. This factor can readily
exceed 20 db. If the sensitivity of the indicator
means for demodulating said combined signal
means responsive to said demodulated signals for
2,489,270
5
6
effectively controlling the rotation of said direc
tional antenna, means for producing a bias signal
proportional to the amplitude of said demodu
lated signals means responsive to the value of
said bias signal for controlling the amplitude of
said sense antenna signal for mixing with said
low frequency signals to vary inversely with the
amplitude of said demodulated signals.
nals received by said sense antenna through
said third mixer to said receiving means, said
receiving means comprising means for demodu
lating the signals applied thereto for obtaining
said given frequency signals, means responsive
for modulating the electrical signals received by
reception pattern of said directive antenna.
to said demcdulated signals for eiîectively con
trolling the rotation of said directional antenna,
means for producing a bias signal proportional to
5. A radio direction finder comprising an ef
said demodulated signals, means for applying
fectively rotating directional antenna, a sense an 10 said bias signals to said first and second mixer-`
tenna, a source of low frequency signals, a ñrst
circuits whereby the sensitivity of said control
and second mixing circuit, and a receiver, means
means is increased about the null-position of the
said directional antenna comprising said low fre
8. In a radio direction finder system of the
quency source and said first and second mixer 15 type comprising an effectively rotating direction
circ-uits, means coupling the output of said first
al antenna, and sense antenna, a receiving
and second mixers to said receiver whereby car
means, a ñrst and second electron _discharge de
rier suppressed low frequency modulated elec
vice, having control electrodes, means for apply
trical signals are produced in said receiver, a third
ing modulation signals from said given frequency
mixer circuit, means for coupling the electrical 20 signal source in phase opposition to control eleo
signals received by said sense antenna through
trodes of said first and second device, means for
said third mixer to said receiver, said receiver
applying electrical signals received by said direc
comprising means for demodulating the signals
tional antenna in phase opposition to control elec
applied thereto for obtaining said lov»T frequency
trodes of said ñrst and second device means for
signals, means for eii‘ectively controlling the ro 25 coupling the output of said first and second de
tation of said directional antenna, means for ap
vice to said receiving means, a third electron dis
plying said demodulated signals to said control
charge device having control electrodes, means
ling means, means for producing a bias signal pro
for coupling the electrical signals received by said
portional to said demodulated signals, means for
sense antenna to a control electrode of said third
applying said bias signal to said third mixer cir 30 device, means for coupling the output of said
cuit whereby the amplitude of said sense antenna
third device to said receiving means, an ampli
signal applied to said receiver varies inversely
fier circuit coupled to the output of said receiv
proportionally with the amplitude of said demod
ing means, said amplifier circuit having its out
ulated signals.
put coupled through a band pass ñlter to the in
6. In a radio direction ñnder of the type com 35 put of a detector circuit, said band pass filter be
prising an effectively rotating directional antenna
ing tuned i0 pass said given frequency signals
and a sense antenna, a source of electrical sig
from said receiving means. means for translating
nals of given frequency and a receiver, a ñrst and
said filtered signals to obtain the direction of
second mixing circuit, means for modulating the
received electrical signals, means for applying
the electrical signals received by said directional 40 the output of said detector to control electrodes
antenna comprising said given frequency source
of said first and second device whereby the sen
and said first and second mixer circuits, the out
sitivity of the direction finder is improved about
put of said first and second mixing circuits com
the null-position of the reception pattern of said
prising carrier suppressed given frequency modu
directional antenna.
lated electrical signals, means for applying said 45
9. In a radio direction ñnder system of the
last named signals to said receiver a third mixing
type comprising an effectively rotating directive
circuit, means for coupling the electrical signals
antenna and a sense antenna a source of ñxed
received by said sense, means for coupling the
frequency modulation signals, a receiving means,
electrical signals received by said sense antenna
a ñrst and second electron discharge device, hav
50
through said third mixing circuit to said receiver,
ing control electrodes means for applying modu
said receiver comprising means for demodulating
lation signals from said fixed frequency source
the signals applied thereto for obtaining said giv
en frequency signals a translating means and
in phase opposition to control electrodes of said
first and second device, means for applying elec
trical signals received by said directional antenna
means for applying thereto said demodulated sig
nals whereby the direction of antennae received 55 in phase opposition to control electrodes of said
electrical signals is determined, means for pro
ñrst and second device, means for coupling the
ducing a bias signal corresponding to said demod
output of said first and second device to said re
ulated signals, means for applying said bias sig
ceiving means. a third electrical discharge device,
nals to said ñrst and second mixer circuits where
by the sensitivity of said translating means is 60 having control electrodes means for coupling the
electrical signals received by said sense antenna
increased about the null-position of the recep
to a control electrode of said third device, means
tion pattern of said directive antennae.
for coupling the output of said third device to
7. A radio direction finder comprising an ef
said receiving means an ampliñer circuit coupled
fectively rotating directional antenna, a sense an
tenna, a receiving means, a source of given fre 65 to the output of said receiving means, said ampli
ñer circuit having its output circuit coupled
quency signals, a ñrst and second mixing circuit,
through a band pass filter to the input of a de
means for modulating the electrical signals re
tector circuit, said band pass iìlter being tuned to
ceived by said directional antenna comprising
pass said ñxed frequency signals, from said re
said low frequency source and said iirst and
Second mixer circuits the output of Said ñrst 70 ceiving means, means responsive to said band pass
filter output for eiîectively controlling the rota
and second mixers being electrically coupled to
said receiving means whereby carrier suppressed
tion of said omni-directional antenna, means for
applying the output of said detector to control
low frequency modulated electrical signal-s are
passed to said receiving means, a third mixer
electrodes of said ñrst and second device where
circuit, means for coupling the electrical sig
75 by the sensitivity of the direction ñnder is in
25,48%2170
creased, about the null-position of the» reception
pattern of said directive, antenna.
pled through a band. pass ñlter to the~ input- of a
10».~In a. radio- direction ñnder system of the
to pass said low frequency signals from said re
ceiving means, means responsive to saidV band
passl ñlter output for effectively controlling the
type- comprisingl an effectively rotating directive
antenna, and. a. sense antenna, a source of low
frequency' modulation` signals, a receiving means
añrst; and second electron discharge device, hav
ing control electrodes, means for applying modu
lation signals from said low frequency source in
detector circuit, said band pass filter being tuned
rotation of said directive antenna, the output of
said detector being coupled to a control electrode
of said third device whereby a bias signal is pro
duced, said bias signal controlling the amplifi
phase opposition to control> electrodes of said ñrst 10 cation of said third device whereby the sense an
tenna signals applied to said receiving means vary
and second` device, means forl applying electrical
in accordance with said receiving means output.
signals received by said direc-tional antenna in
EUGENE COLE.
phase opposition to control electrodes of said ñrst
and second device, means for coupling the output
REFERENCES CITED
ofr said ñrst and. second dev-ice to said receiving 15
means, a third electron discharge device having
The following references are of record. in. the
control «electrodes» means for coupling the elec
ñle of this patent:
trical signals received by said» sense antenna to
UNITED sTATEs i=ATENTs
a- controlî electrode of said third device, means
for coupling the output of said thirdv device to 20 Number
said receiving means, an amplifier circuit cou
pled:- toy the output of said receiving means, said
ampliñer circuit- having its- output circuit cou
2,171,561
2,220,904
2,314,029
Name
Date
Hooven __________ __ Sept. 5, 1939
Hooven __________ __ Nov. 12, 1940
Bond et al ________ __ Mar. 16, 1943