May 23, 31950 7
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BR’ITTON CHANGE
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Filed Sept. 21, 1945
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INVENTOR.
BRITTON CHANCE
BY
ATTORNEY
‘Patented May 23, 1950
v 2.508.565
vuurrso sfrA'rEs Pars
2,508,565
ELECTRICAL NAVIGATION SYSTEM
Britton Chance, Cambridge, Mass., assignor, by
'mesne assignments, to the United States of
America-as represented by the Secretary of War
Application September 21, 1945, Serial No. 617,873
10 Claims. (Cl. 343-45)
2 .
This invention relates to an electrical naviga
ods, radio responder beacons are designated as
beacons A and B while 0 is, the point to which
the aircraft P is to be accurately navigated. If
bombs are to be dropped, point 0 becomes the
bomb release point and is determined from the
tion system and more particularly to a means for
simultaneously tracking a plurality of respond
ing radio beacons.
One method of navigating an aircraft includes
the determination of the distance between the
aircraft and a radio beacon having a known posi
tion. The beacon may be of the type which,
when interrogated by a pulse of electromagnetic
energy transmitted by the radio object detection
apparatus carried by the aircraft, responds with
a reply.
position of the target, by predetermining the alti- I
tude, speed, and heading of the ‘aircraft at the
1o
The response of the beacon may be a
series of pulses uniquely coded to distinguish it
from other responding beacons. The time claps
ing between the transmission of the interrogating
pulse from the aircraft and the receipt by the air
craft of the beacon response is a measure of the
bomb release point, and by predicting the wind
velocity and direction.
One method by which the aircraft may accu=
rately navigate to the bomb release point is by
?ying at a constant distance from one beacon,
known as the cat beacon, and shown as A. in Fig.‘
l. The bombs are released when the aircraft ar
‘lives at the proper distance from beacon B, known
as the mouse beacon.
When the cat and mouse bombing approach is -
distance from the aircraft to the beacon.
used, voltages may be produced each of which is
The aircraft may carry apparatus capable of
proportional to the range from the aircraft to one
being set to track a preselected beacon and pro 20 beacon. These voltages may each be compared
ducing a continuous measure of the range of the
with a fixed voltage preset to a value correspond
beacon from the aircraft. As used herein the
ing to the range of destination, or bomb release
term “tracking a beacon” denotes the operation of
point, to one of the beacons.
producing a voltage the magnitude of which is
- If a voltage corresponding to the entire range
proportional to the instantaneous range fromthe 25 to a beacon, such as A-C in Fig. 1, is used for
aircraft to the beacon. If the range from the air
comparison with a ?xed‘ voltage, the percentage
craft of two beacons having known positions is
variation of the changing range voltage is small
determined, the position of the aircraft may be
and it is di?icult to make the comparison with a
established.
‘
high degree of precision. It is therefore more
It is an object of this invention to provide an‘
satisfactory if the range of the aircraft is tracked
apparatus for simultaneously tracking a plurality
with respect to a ?xed range circle such as range
of beacons. It is a further object to provide
circles l or 2 designated in Fig. l. Voltages cormeans for tracking a plurality of beacons where~
responding to the ranges of the aircraft to range
by at least some of the tracking components are
circles i and 2 are therefore compared with volt35 ages corresponding to the distances C-D and
used in the tracking of each beacon.
Other objects, features, and advantages'of this
C-E. The percentage variation of the changinvention will suggest themselves to those skilled
ing range voltages is then high and the compari
in the art and will become apparent from the fol
son with the ?xed voltages may be readily made
lowing description of the invention taken in con
with precision.
I
nection with the accompanying drawing in 40 Referring now more particularly’ to Fig. 2, ra
which:
_
/'
dio object detection apparatus it includes timer
Fig. l is a diagram used in explaining the prin
H controlling the operation of transmitter 12
ciples of beacon navigation;
which is connected through transmit-receive
Fig. 2 is a block diagram of a navigation system
(T-R) switch is to radiating element is of an
45 tenna l5. Timer ii is preferably a circuit capa
involving the principles of this invention;
Fig. 3 shows the viewing screen of the indicator '
tube in Fig. 2;
_
Fig. 4 is a block diagram of one form 01’ beacon
tracker circuit;
'
Fig. 5 is a block diagram showing an alterna- '
tive form of a beacon tracker circuit; and
Fig. 6 is a schematic wiring diagram of one .
’
'
'
‘
:
'
ble of producing short sharp voltage pulses at ac
curately spaced intervals oi’ time. Antenna it
also includes re?ecting element it and is rotated
about a vertical axis by antenna drive mechanism
ll. T—R switch it is also connected to receiver
it. 'An indication of antenna rotation is trans
mitted as indicated by dotted line 22 to di?'eren
tial gear assemblies 23 and it, provided with ad
form of memory circuit.‘
Referring now more particularly to Fig. 1 for
justing knobs 25 and 28 respectively. The output
an explanation of navigation and bombing meth- 55 ‘1 of di?erential 23 drives cam 29 while the output "
3
asoasss
of differential 24 drives cam 30. Cams 2! and II
both act upon cam follower ll pivoted at point 32
and held in a neutral position by member 33 and
‘the tension of spring 84. Follower 3i may be
slightly ?exible so as not to break if, during ad
justment, it is simultaneously forced in opposite
directions by cams 29 and 30.
Timer H is also connected to provide 9, refer
ence pulse to step delay circuit 40 which may be
vided with the output of receiver ll to provide an
index pulse and may be any circuit capable of
comparing the beacon response or index pulse
from receiver l8 with the delayed reference pulse
from range delay circuit 55 and producing 9. volt
age proportional to the time di?erence in the oc
currence of the two pulses. The output voltage
of beacon tracker It must have one polarity if the
reference pulse occurs before the beacon response
any circuit capable of delaying the reference 10 and the opposite polarity if the reference pulse
pulses from timer II by ‘predetermined steps.
occurs after the beacon response. Beacon track
One circuit that is well adapted for use as a step
er circuit 50 will be more fully described below
delay circuit is a uni-stable multivibrator circuit.
with reference to Figs. 4 and 5.
It is well known that this type of multivibrator
Beacon tracker circuit 80, is provided with a
will produce a voltage pulse starting at the time 15' switch 52 having upper position “A,” lower posi
an input pulse is ap lied to a control element of
tion "3,” and middle neutral position "N." In
the multivibrator. t is also well known that the
the upper position “A," switch 82 makes contact
time width of the pulse produced by a uni-stable
with memory circuit A. .Memory circuit A may
multivibrator may be made proportional to the
be any circuit capable of receiving the error VOlt‘.
steady bias voltage applied to the same or another 20 age from beacon tracker circuit 80 and producing
control element. This pulse generated by the
a continuing voltage indicative of the elapsed
time between the interrogating pulse and the re
short, sharp output pulse occurs in time coinci
ceived response, and hence indicative of the range
dence with the trailing edge of the pulse gener
from the aircraft to the beacon. The output
ated by the multivibrator. If the bias voltage ap 25 voltage of memory circuit A also varies in mag
plied to the multivibrator in discreet steps the in
nitude in accordance with the rate of variation in '
terval of time between the time the input pulse
range between the aircraft and beacon. In posi
is applied and the time the sharp output pulse is
tion “B,” switch 62 connects beacon tracker 8|
generated will vary in discreet steps or discreet
with memory circuit. B which is constructed in
intervals of time. It will be convenient in analyz 30 the same manner as memory circuit A. Switch
ing the operation of this circuit to speak of the
63 having upper position “A," lower position “B,”
output pulse from the multivibrator as a delayed
and middle neutral position “N" is provided to
reference pulse. The delayed reference pulse is
connect line 59 to the output of either memory
fed to range delay circuit 58. Range delay circuit
circuit A or memory circuit B.
85
58 may be a second uni-stable multivibrator circuit
Memory circuits A and B which will presently
similar to the one described , above._ However,
be described in connection with Figure 6 may be
range delay circuit 58 diil’ers from circuit 40 in
constructed in the manner disclosed for the mem
that the bias voltage applied to circuit 58 is‘con
ory circuit in the application by Andrew B. Jacob
tinuously variable rather than being variable in
sen, Serial No. 584.233, entitled “Electrical cir
steps as was the case in circuit 40. The continu 40 cuit," ?led March 22, 1945.
ously variable bias voltage permits circuit 58 to
Memory circuits A and B are more fully de
produce a continuously variable time delay. Step
scribed in connection with the, description of
delay circuit 40 is provided with a switch 45 having
Fig. 6 below.
1
. an upper position “A? lower position “3,” and
The output of memory circuit A may be com
middle neutral position “NJ’ Switch 45 in the “A”
pared by meter 65 to a voltage picked up by ad
position makes contact with the contactor 46 of ’ justable contactor 6B. Contactor 85 is adjustable
potentiometer 41 connected between a source of
along potentiometer 61 connected between a
positive potential and ground. In the "3” posi
source of positive potential and ground. The out
tion, switch 45 makes contact with contactor 48 of
put of memory circuit B is compared by meter 58
potentiometer 49 connected between a source of 50 with a voltage picked up by contactor 10. Con
positive potential and ground. Contactors 46 and
tactor ‘i0 is adjustable along potentiometer Tl
48 are adjustable along their respective potenti
connected between a source of positive potential
ometers in steps. Since the pulse repetition rate
and ground. Bomb release circuit 72 receives an
of timer i l is high compared to the switching rate
input from memory circuit B and contactor ‘I0.
55
of switch 45 the delay introduced by circuit 40
Circuit ‘#2 may be any circuit capable of releasing
when switch 65 is in the “A” position will be de
a bomb, as by energizing or deenergizing a relay,
termined by the bias supplied by potentiometer
when the voltage output of memory circuit 13 is
5?. When switch 85 moves to the “B” position
equal to the voltage picked up by contactor 10.‘
' the delay introduced by circuit at will be that de
Since relays and relay circuits that operate on a
termined by potentiometer 49.
~ 60 very small differential between two applied volt
Timer ii is also connected to sweep generator
ages are very well known it is not considered nec
50, the output of which isconnected to the de
essary to further describe circuit ‘I2. However, if:
iiecting coils 5! of cathode ray indicator tube 52.
it is desired to construct a bomb release circuit
Tube 52 also contains electron gun 53, control
that is well adapted for use with applicant's in
65 vention reference should be had to the copending
grid 54, and ?uorescent screen 55.
As stated above, range delay'circuit 58 may be
application of Richard K. Mosher, Serial No.
any circuit capable of adding a controlled delay
$922,155,
entitled, Electrical apparatus, ?led June
to the pulse received from step delay circuit 40.
Again, the pulse produced by circuit 58 could be
In the operation of the apparatus set forth
differentiated to produce a sharp pulse at the V10 in Fig. 2, timer I I controls the operation of trans
trailing edge of the multivibrator pulse.
mitter I: so that the latter produces a series of
The delayed pulse provided in the output of
equally spaced radiov frequency pulses which are
range delay circuit 58 is applied to control grid 55
transmitted through T-R switch ii to antenna
of indicator tube 52 and also to beacon tracker
l5. Radiating element It and re?ector ll co
circuit 60. Beacon tracker circuit 60 is also pro‘ 75 operate to Produce a narrow directional beam of
multivibrator may be differentiated so that a
radio frequency pulses. Antenna it is rota
about a vertical axis by antenna drive l‘l.
1
radio responder beacons intercepting the search
pulses sent out by antenna it will respond by
transmitting a non-directional reply. Any reply
received by antenna it will be fed through T-R
switch as to receiver it. T-R switch it is pro-»
vided for the purpose of preventing radio pulses
produced by transmitter l2 from entering receiver
age correctly 3)
to the range of beacon
A, the delay given the reference pulse will. be such
as to cause the reference pulse to appear at bea
con tracker to in time coincidence with the
arrival of the index ‘pulse beacon response and no
error voltage will be supplied to change the out
put of fnemory circuit A. On the other hand, if
the two pulses do not arrive coincidently at
beacon tracker Bil, a proper error voltage will be
it, and for preventing signals received by antenna l0 produced to correct the range voltage produced
it from entering transmitter l2.
by memory circuit A which will in turn correct
Cams 29 and 3B are rotated in synchronism with
the range delay in circuit 58.
antenna it. The phase of cams 29 and 30 may be
When beacon B is being interrogated, the ac
adjusted by knobs 25 and 26 respectively so that
tion is similar to that described above except
when rotating antenna It approaches the azi 15 that switch t2 applies the error voltage produced
muth oi’ beacon A, cam 29 coacts with cam fol
by beacon tracker st to memory circuit B while
switch 83 applies the range voltage from memory
lower 85 to throw swit'ches d5, 82, and 63 into
their "A” positions. The switches are kept in
circuit B to range delay circuit 58 so that the
range pulse has a delay corresponding to the
their “A" position while antenna is sweeps
through a short arc, the center of which has an
range of beacon B.
'
The range voltage produced‘ by memory cir
cuit A is compared by meter 66 with the voltage
set in potentiometer 61. Meter 85 will thus
beacon B, cam 38 coacts with follower 3i and
indicate when the aircraft reaches a certain range
causes switches as, $2, and $3 to be in their “B” 25 with respect to beacon A. Meter til similarly
azimuth approximately that of beacon A. The
are may have a width of about 15°. Similarly
when antenna it approaches the azimuth of
position through a short are of rotation by an
indicates when the aircraft reaches a certain
tenna it. During the intervals when antenna in
is not pointed approximately at either beacon A
range with respect to beacon B. On bombing
missions, bombrelease mechanism l2 automat
ically releases the bombs when the aircraft reach
or B, neither cam 2Q nor til will coast with fol
lower 8i. and switches (it. 82, and to will be in 80 es the range preset into potentiometer l l.
their neutral position “N.”
The range of the beacon is tracked in the ap
The reference pulse produced by timer ii isied
paratus of Fig. 2 by delaying the reference pulse
to step delay circuit dd where it is delayed by one
from timer H by an amount corresponding to the
predetermined amount when antenna id is point
range from the aircraft to the beacon. Adjust
ment of step delay circuit M by potentiometers
ed at beacon A and by another controlled amount
when antenna it is pointed at beacon B.
The .
delay for beacon A is set by adjustment of con
tractor 58 while the delay for beacon B is set by
adjustment of contractor lit. In the situation
shown in Fig. l, contactor 58 would be set to ,
give a delay corresponding to AD while contactor
68 would be set to give a delay corresponding to
BE.
The delayed reference pulse in the output of
circuit Ad is further delayed by range delay cir
cuit 58. The additional delay given by circuit
58 depends upon the control voltage received
through line 59, from either memory circuit A or
memory circuit B in dependence upon whether
antenna it. is pointed at beacon A or beacon, B.
‘The delayed reference pulse in the output of
circuit 58 is fed to beacon tracker 86 where its
time of arrival is compared with the time of
arrival of the response received from the inter
rogated beacon. If the delayed pulse from cir
6i and as introduces delays of an amount cor
respondng to any of the 10 mile range circles
shown in Fig. i. It will be obvious however that
the step delay circuit is not necessarily limited to
10 mile steps but, may be made adjustable to in
troduce delays corresponding to any range. In
the situation shown in Fig. l, the step delay cir
cuit tit introduces delays corresponding to the
distances from beacons A and B to range circles
l and 2 respectively. Range delay circuit 58 in
troduces delays corresponding to the range from
the aircraft P to range circles l and 2.
Referring again to Fig. 1, when the cat and
mouse method of approach to destination or the
bomb release point is used, meter 65 indicating
the range to beacon A becomes a pilot direction
indicator, the de?ection of the needle indicating
to the pilot whether or not he is on course, and
in which direction he must go to get on course,
while meter t6 becomes a distance-to-go meter
cuit 58 arrives at beacon tracker til at the same
indicating to the pilot the distance to the bomb
time as the beacon response or index pulse from
release point.
receiver it, no error voltage is produced by beacon
tracker so. If the delayed reference pulse arrives
In Fig. 4 is shown a possible circuit for beacon
tracker $3 in which ‘the reference pulse from
before the beacon response, an error voltage of
range delay circuit as produces in gate generator
one polarity is produced, said voltage being of a
magnitude proportional to the time difference. if
the delayed reference pulse arrives at a time after
the arrival of the beacon response, a voltage of the
8d a square pulse which is fed to coincidence
circuit ti and delay circuit 92 where it is de
'
iayed by a slight amount and fed to coincidence .
opposite polarity is produced,'said voltage having
circuit 83. Again, gate generator til may be a
uni-stable multivibrator. In this instance, how
a magnitude proportional to the time difference.
If beacon A is being interrogated, the error
. ever, it is preferred that the multivibrator be
voltage is applied through operation of switch 6%
to memory circuit A. As will be explained pres
ently, memory circuit A produces an output volt
age proportional to the range of beacon A. When
beacon A is being interrogated, the output voltage
supplied with a ?xed bias voltage. The ?xed
bias is supplied so that the square voltage pulse
produced by the multivibrator will have a con
stant time width. Delay circuit as may be a
uni-stable multivibrator or it may be an elec
trical delay line. The beacon response or index
of memory circuit A is applied through action of
pulse is fed from receiver is to coincidence cir
switch 588 and through line 59 to range delay cirw
cuits ti and as. Coincidence circuits ti and t3 ,
cuit 5%. If memory circuit A is producing a volt~ 75 are arranged so that a pulse appears in the out
2,508,505
8
put'of these circuits only if the reference‘pulsc'
.
producing a delay in the reference pulse, said
delay being of certain magnitudes when switches
and the ?rst pulse of the beacon response ap
88 and 89 are in position “A" and being of other
pears simultaneously therein. Coincidence cir
cuits 8| and 03 are essentially ampli?ers having
magnitudes when switches 98 and 99 are‘ in posi
two signal inputs, In this respect they are some 5 tion "B," the magnitude of the various delays
being adjustable by movement of contactors I02,
what similar to audio frequency mixer circuits.
However, they diner from thwe mixer circuits
I03, I00,_and'l01.
The, outputs of delay circuits 98 and 81 are
in that the bias on both signal inputs is great
fed to coincidence circuits H2 and II! respec
enough to prevent .the generation of an output
signal unless a signal is present at both signal 10 tively. The coincidence circuits H2 and III are
inputs. Therefore, if the beacon response or in
dex pulse arrives at a time directly between the
gate pulse from generator 80 and the delayed
gate pulse from circuit 82, equal pulses will be
applied to di?erential error circuit 84 and no
error voltage will be generated by the latter cir
cuit. Ii’. however, the beacon response or index
pulse occurs at a time more nearly coincident
also supplied with the beacon response from the
video circuit of receiver II and produce a pulse
in their output, when the delayed reference pulse
coincides in time with one o! the pulses in the
coded series of the beacon response. The out
' puts of coincidence circuits H2 and H3 are ap
plied to connector circuits III and II! respec—
tively. Connector circuits H4 and H5 will allow
the differential error voltage from circuit 84 to
with the gate pulse from generator 80 then a
larger pulse will be produced by coincidence cir 20 pass to the memory circuits A or B only when
the reference pulse has been properly‘ delayed
cuit 8I than is the case for coincidence circuit
by circuits 96 and 91 to coincide with the coded
83 and an error voltage of one polarity will be
series of beacon responses.
produced. If the beacon response arrives at a
When the antenna points toward beacon A,
time more nearly coincident with the delayed
gate pulse from generator 80, then coincidence 26 switches 98 and 99 will be shifted by member
33 of Fig. 1, into their A positions and the beacon
circuit 83 will produce a larger pulse than will
tracker circuit will then accept only responses
coincidence circuit 8| and an error voltage of
coded in accordance with the code of beacon A.
opposite polarity will be generated by the latter
circuit.
Diiferential error circuit 84 which pro
duces the error voltage is preferably a, type of
diiierential ampli?er circuit followed by a low
pass ?lter. The low pass ?lter in effect converts
the pulses of error voltage coming from the dif
ferential ampli?er into a steady or slowly chang
ing error voltage. This steady or slowly chang
ing voltage is essential to the proper operation
of range delay circuit 58. The components of
the circuit in Fig. 4 are constructed and operate
in the manner set forth in the application by
Andrew B. Jacobsen, Serial No. 584,233, referred
to above.
In the apparatus described above, reliance is
placed on the directional qualities of antenna
is for insurance that the proper beacons are be
ing tracked. If additional insurance is required
that the proper beacons are being tracked, the
beacon tracking circuit may be arranged to ac
cept responses’ from beacon A as identi?ed by
the known coding of its pulses, when the antenna
When antenna points toward beacon B. switches _
30 98 and 99 will be shifted to the “B” position and
beacon tracker 60 will accept only impulses coded
in accordance with the code of beacon 2B.
The components of the circuit in Fig. 5 may be
similar in construction and operation to corre
35 sponding circuits described in the application by
Andrew B. Jacobsen, Serial No. 584,233, referred
to above.
Each of memory circuits A and B may be con
structed as set forth in Fig. 6. In Fig. 6, the sig
40 nal or error voltage is applied to terminal I08
and, during the duration of said error voltage,
capacitors I69 and I10 charged with the charg
ing current ?owing through resistor "I. The
charge on capacitor I68, serving as bias for elec
45 tron tube I12, controls the amount of plate cur.
rent ?owing through this tube and thus the
amount of current through resistor I13. When
the potential at the end of resistor I13 con
nected to resistor I14 rises above the charge
points toward beacon A, and to accept only pulses 50 on capacitor I10, current ?ows through resistor
I14 to increase the charge on capacitor I10.
from beacon B when the antenna points toward
that beacon.
Connected to‘the plate of tube I12 is shown a
Referring now more particularly to Fig. 5 for
source of voltage I 15. Switches I16, I11, and
a tracking circuit capable of discriminating
I18 are mechanically connected together and rep
among coded responses, gate generator 90, co '55 resent a single throw triple-pole device which
is normally open but when closed permits man
incidence circuits BI and 98, delay circuit 92,
and differential error circuit 04 are constructed
ual setting of the bias supplied by connector 58
and operate in a manner similar to that set forth
to range delay unit 58 by moving the sliding
for components 80, 8I, 83, 82, and 84 respectively
contact on potentiometer I19 which has con--‘
in Fig. 4. The reference pulse from range de 60 nected across its sources of voltage I80 anod I8I. ,
lay circuit 58 is also applied to delay circuits 96
The manner in which memory ‘circuits A and
and 91. Delay circuits 96 and 91 are provided
. B operate may be explained with reference to Fig‘.
with ganged switches 88 and 99 respectively, each
6. The voltage charge across capacitor I69 is
having left positions ,“A,” right positions “B,”
proportional to the error voltage. If this is a
and neutral positions “N.” In positions “A,” 65 large voltage, tube I12 conducts more readily
switches 98 and 99 make contact with movable
and the potential at terminal I82 will rise rap- ,
contactors I02 and I03 01' potentiometers ‘I04
idly. The potential at terminal I82 rises or falls
and I05 respectively, said potentiometers being
in an exponential manner due to the charge or
connected between a source of positive'potential
discharge of capacitor I10. The grid of tube
and ground. In the “B” position, switches 98 and 70 I12 rises with the cathode as the grid is con
89 make connections with contactors I06 and I01
nected to the cathode by resistors HI and ‘I14
of potentiometers I08 and I09 respectively, said
and capacitor I68.
,
.
potentiometers each being connected between a
Thus. it will be seen that a positive error volt
source of positive potential and ground. Delay
age applied at terminal I68 will produce an out’
circuits 96 and 91 may be any circuits capable of ‘"5 put voltage at terminal I82, said output voltage
aso’acco
increasing at a rate depending on the magnitude
part of the distance comprising a potential sup=
of the error voltage. A negative error signal at
plied by either potentiometer d‘! or 48, which
represents a measure of the major part of the
referred to distance. A second means, range de
terminal use will produce a. similarly decreasing
output voltage. Said increase or decrease in out
put voltage will continue for a time which is
lay unit 58, is provided for additionally delay
long compared to the interrogation period.
ing the reference pulse, the purpose of which
When switches H5, Ill and H8 are closed,
resistor i'ié is shorted and it is possible to con
trol the voltage at terminal 182 by regulating
is to establish coincidence of the reference and
the index pulses and is comprised of a bias or
range potential which represents a measure of
_
v
potentiometer 5133. Switch I'll prevents power 10 the remaining part of the distance.
A comparison circuit, the beacon tracker 68,
losses from sources 1186 and it! when poten
is provided for producing an error potential pro
tiometer H9 is not being used.
portional to the deviation from the aforemen
The output of memory circuits A and B are
applied as bias to range vdelay unit by means
tioned coincidence which results from travel of
of switch 63.
15 the craft.
Memory circuits A and B each produce a volt-'
Also, there is provided a memory circuit, the
memory circuit A or B, comprising means for
age bias indicative of the range to 2, correspond
storing the range potential. This memory cir
ing ?xed beacon. This range voltage initially
out also includes means responsive to the error
set or stored in the circuit by the manual op
eration described above in locating the beacon 20 signal for adjusting the stored range potential
in correspondence with the rate of change of
and therefore varies in accordance with the er
the range.
ror voltage generated by unit to. If the beacon
Also there is provided means, the potentiometer
is interrogated intermittently, memory circuit 23
?ll or potentiometer ‘H, for establishing a po
develops a voltage between the replies, said volt
age being indicative of the range determined by 25 tential representing a desired range for the par
the last reply.
ticular station and means, the meter 65 or 6t.
Referring to Fig. 6, the rate at which capacitor
for indicating the difference between the meas
ured and desired range.
lid changes its charge is proportional to the ve
locity of the moving interrogator with respect
While there has been described what is at
to the beacon. The time constant of the cir 86 present considered to be the preferred embodi
cuit containing capacitor l'l? is approximately
ment of this invention. it will be obvious to those
equal or larger than the longest time interval
skilled in the art that various changes and modi=
?cations may be made therein without depart
between successive appearances of the video sig
nal permitting capacitor lid to change its volt
ing from the scope of the invention as set forth
age; thus, changing the bias on range delay unit 35 in the appended claims.
The invention claimed is:
58 in relation to the rate of change of the dis
1. In a radio navigation system means for
tance between the interrogator and the ?xed
transmitting electromagnetic energy pulses and
beacon which results in velocity memory. If the
for receiving signals from each of a plurality
rate of change of the distance between inter
of remote sources responsive to said transmitted
rogator and the beacon remains constant, the
memory circuit will anticipate the change in
pulses, means for generating a reference pulse
distance between successive interrogations and
each time a pulse is transmitted, ?rst predicting
means providing a voltage the amplitude of which
position the reference pulse so that it is coin
is proportional to the anticipated time interval
cident with the received reply or index pulse.
Referring to Fig. 6, it will be noted that when 45 between the time of occurrence of said refer
switches fit, if? and We are closed the voltage
ence pulses and the time that signals from a
at terminal I82 may be controlled manually to
first remote source are received, second predict
ing means providing a. voltage proportional to
adjust the delay of unit 58 to position the ref
the anticipated time interval between the time
erence pulse output of 5% at coincidence with the
received pulses, thus permitting a particular bea '50 of occurrence of said reference pulses and the
con to be searched for and, after ?nding the
time signals from a second remote source are
received, delay means responsive to said pre
beacon, the opening of switches 178, ill, and
dicting means for delaying said reference pulses,
978 will permit the beacon to be tracked auto
matically,
?rst switch means having at least two opera
From the description given above, it will be 55 tive positions, said switch means connecting said
?rst predicting means to said delay means when
clear that in accordance with the present in
.in a ?rst operative position and connecting said
vention, there is provided a navigation system
for continuously determining the location of a
second predicting means to said delay means
when in a second operative position, a comparison
mobile craft relative to a plurality of fixed sta
tions located at known positions comprising 60 circuit responsive to said delayed reference pulses
means for establishing communication periodi
and signals from said remote sources, said com
parison circuit providing an error signal propor
cally between the craft and each of these sta~
tions.
'
tional to the time interval between the time of
‘occurrence of said delayed reference pulse and
Also there is provided the means, timer H for
producing at the craft a timing and a reference
the time that said signals are received, second switch means having at least two operative posi
pulse recurrent at a chosen repetition rate and
tions, said second switch means connecting said
means, receiver 58, responsive to the commu
comparison circuit to said ?rst predicting means
nication with a particular one of these stations
when in a ?rst operative position and to said sec
for producing an index pulse having a time delay
relative to the reference pulse which corresponds 70 ond predicting means when in a second operative
position; and means for causing said ?rst and sec
to the distance of the craft from the particular
ond switch means. to be in said first operative pom
station.
'
sition's when signals from said ?rst source are
Also, there is provided a ?rst means, the step
delay unit 66, for delaying ‘the reference pulse
' being received and in said second operative po
by an amount corresponding to a chosen major 75 sltion when signals from said second source are
3,608,600
.11
v
, being received whereby the signal from said com
parison means controls the output of said pre
dicting means‘so that errors, if any, between
said anticipated time intervals and the actual
time intervals between the time of occurrence
of said reference pulses andthe time said signals
_ are received from said remote sources are sub
stantially eliminated.
12
, storage means thereby storing data
- only one of said sources.
relative to
7. A navigation system for continuously de
termining the location of a mobile craft‘rela
tive to a plurality of ?xed stations located at
known positions comprising means for establish
ing communication cyclically between said craft
and each of said stations, means for producing
2. Apparatus as claimed in claim 1 wherein
at said craft a timing and a reference pulse re
said comparison circuit includes means for re 10 current at a chosen repetition rate, means re
jecting received signals not having a predeter
sponsive in turn to the communication with each
mined code.
one of said stations for producing in turn an
3. Apparatus as claimed in claim 1 said ap
index pulse having a time delay relative to said
paratus further comprising means for establish
reference pulse which corresponds in turn to
ing a ?rst ?xed reference voltage, means for 15 the distance of said craft from each of said
comparing the output of said ?rst predicting
stations, a ?rst means for cyclically delaying
means with said ?rst reference voltage and in
said reference pulse by an amount which in turn
dicating the di?erence in amplitude if any there
corresponds to a chosen major part of said dis
between, means tor estabishing a, second ?xed
tance from each of said stations comprising a plu- '
‘reference voltage, and means for comparing the 20 rality of potentials which represent in each case
output of said second predicting‘means and in
dicating the difference, if any, therebetween.
4. A system for tracking a plurality of signals
the measure of said major part, a second means
for additionally delaying said reference pulse by
an amount which corresponds in each case to the
remaining part of said range, to establish co
prising means for generating a reference pulse, 25 incidence of said reference and said index pulses,
delay means responsive to an input bias voltage
comprising a bias or range potential which rep
for delaying said reference pulse, ‘a comparison
resents a measure of the remaining part of said
circuit for generating an error voltage propor
range, a comparison circuit for producing an
tional to the time spacing between said delayed
error potential proportional to the deviation from
reference pulse and a received signal, a plurality 30 coincidence which results from travel of said
' of signal storage means, a ?rst switch means
craft, a corresponding plurality of memory cir
having a plurality of operative positions, each
cuits comprising means for storing said range
of said positions selectively connecting said com
potentials which represent the range of each of
parlson circuit to one of said signal storage
said stations and means responsive to said error
means, a second switch means having a plu
signal for adjusting each of said stored range
‘rality of operative positions, each of said op
potentials in correspondence with the rate of
erative positions connecting said delay means to
change of said range, means ior establishing a
one of said signal storage means and means for
corresponding plurality of potentials, each rep- '
causing said ?rst and second switch means to as
resenting the desired remaining part of said range
sume predetermined operative positions as each
and means for indicating in each case the dif
signal is being received whereby the output of
ference between said measured and said desired
range.
said signal storage means acts as the input bias
voltage to said delay means and said error signal
8. A navigation system for continuously de
causes the output of said signal from said signal
termining the location of a mobile craft relative
45
storage means to change in a direction that
to a plurality of ?xed stations located at known
will reduce the amplitude of said error signal,
positions comprising, means for establishing com
the output signal from each of said storage means
munication periodically ‘between said craft and
thereby providing a measure of the time interval
each of said stations, means for producing at
between the time a pulse-is transmitted and the
said craft a timing and a reference pulse re~
50 current at a chosen repetition rate, means re
time a particular signal is received.
5. Apparatus as claimed in claim 4 wherein
sponsive to the communication with a particular
said delay means comprises two serially connected
one of said stations for producing an index pulse
delay circuits, one of saidv circuits being respon
having a time delay relative to said reference
sive to the bias voltage supplied from said storage
pulse which corresponds to the distance of said
means and the other of said delay circuits being
craft from said station, a ?rst means for delay
responsive to a second input bias voltage, said
ing said reference pulse by an amount correspond
apparatus further comprising a plurality of ad
ing to a chosen major .part of said distance com
prising a potential which represents a measure
.iustable bias sources, a third switch means hav
ing a .plurality of operative positions, each of
of said major part, a second meansi'or addition.
received in response to a transmitted signal com‘
said positions connecting said other delay cir 60 ally delaying said reference pulse to establish
cuit to one of said adjustable bias sources, and
coincidence of said reference and said' index
means for operating said third switch means in
synchronism with said ?rst and second switch
pulses, comprising a bias or range potential which
represents a measure of the remaining part of
means.
said distance, a comparison circuit for produc
6. In a range tracking system wherein signals 65 ing an error potential proportional to the devia
from a plurality of sources are intermittently
tion from said coincidence which results from
received, and wherein said range tracking sys
travel of said craft, a memory circuit compris
tem comprises means for generating energy rep
_ ing means for storing said range potential, means
resenting a, characteristic of each of said sig
responsive to said error signal for adjusting said
nals, and means for storing said energy, means 70 stored range potential in correspondence with
for simultaneously tracking a plurality of sig
the rate of change of said range, means for
nals comprising a plurality of said storage means
establishing a potential representing a desired
and switch means for connecting a different
range for said particular station and means for
storage means to said generating means each
indicating the difference between said measured,
time a different signal is received, each of said 75 and said desired range.
a
9. A navigation system for continuously de
lishing communication periodically between said
termining the location of ‘a mobile craft rela
tive to a plurality of ?xed stations located at
known positions comprising, means for estab
craft and each of said stations, means for pro
ducing at said craft a timing and a reference
pulse recurrent at a chosen repetition rate, means
lishing communication periodically between said
responsive to the communication with a par?‘
craft and each of said stations, means for pro
ducing at said craft a timing and a reference
ticular one of said stations for producing an
index pulse having a time delay relative to said
pulse recurrent at a chosen repetition rate, means
reference .pulse which corresponds to the range
responsive to the communication with a parof said craft from said station, means for de
ticular one of said stations for producing an in 10 laying said reference pulse by an amount which
corresponds to said range, to establish coinci
dex pulse having a time delay relative to said
dence of said reference and said index pulses,
reierencekpulse which corresponds to the range
comprising a bias or range potential which rep-,
of said craft from said station, means for de
resents a measure of said range, a comparison
laying said reference pulse by an amount which
corresponds to said range, to establish coinci 15 circuit for producing an error potential propor
tional to the deviation from coincidence which
dence of said reference and said index pulses,
comprising a bias or range potential which rep
results from travel of said craft, a memory cir
cuit comprising means for storing said range
resents a measure of said range, a comparison
circuit for producing an error potential propor
potential,
for adjusting
means
saidresponsive
stored range
to said
potential
errorin cor
tional to the deviation from coincidence which 20
respondence with the rate of change of said
results from travel of said craft, a memory cir
range.
cult comprising means for storing said range
potential, means responsive to said error signal
for adjusting said stored range potential in cor
respondence with the rate of change of said 25
REFERENCES CHTED
range, means for establishing a potential rep
The
following
references are of record in the
resenting a desired range for said particular
?le of this patent:
station and means for indicating ‘the di?erence
,
UNITED STATES PATENTS
between said measured and said desired range.
10. A navigation system for continuously de 30 Number
Name
Date
the location of a mobile craft rela=
2,252,083
Luck ___________ _. Aug. 12, 19M
tive to a plurality of ?xed stations located at
w‘... a
2,307,029
M‘. ____________ .._ Jan. 5, 13
positions comprising, means for estab~