Jan. 22, 1952
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`F. w. ouumoaa
`PULSE ECHO DISTANCE AND DIRECTION FINDING
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`2,582,971
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`Filed Nov. 10, 1939
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`2 SHEETS—SI-IEET 1
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`MODULATION
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`/2.3 REPEATER I
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`MODULATION
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`BY
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`INVENTOR
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`ATTORNEY
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`PETITIONERS 1005-0001
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`

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`Jan. 22, 01952
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`F, w, DUNMORE
`PULSE ECHO DISTANCE AND DIRECTION FINDING
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`2,582,971
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`Filed Nov. 10, 1959
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`2 SHEETS—SHEET 2.
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`MODULATION
`REPEATER
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`—
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`MODULATOR
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`SWEEP
`FREQUENCY
`OSCILLATOR
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`PU LSE
`MODULATOR
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`1/,’ a £0
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`FREQUENCY
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`OSCILLATOR
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`Franc/2; /M Dz//micro
`INVENTOR
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` MODULATION
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`REPEATER
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`BY
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`-
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`ATTORNEY
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`PETITIONERS 1005-0002
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`

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`Patented Jan. 22, 1952
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`2,582,971
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`UNl'l‘ED STATES PATENT omci-.
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`2.582.971
`PULSE ECHO DISTANCE AND DIRECTION
`~
`FINDING
`
`Francis W. Dunmore, Washington, D. 0., assignor
`to the United States of America as represented
`by the Secretary of Commerce
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`Application November 10, 1939, Serial No. 803.798
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`is claims. (Cl. 343-11)
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`(Granted under the act oi’ March 3. 1883,]!
`amended April 30, 1928; 370 0. G. 757)
`
`1
`The invention herein described may be made
`or used by or for the Government of the United
`States without
`the payment of ‘any royalty
`thereon or therefor.
`This invention relates to the determination of
`location of an ambulant object by radio and aims
`generally to improve this art. The invention,
`among other things, enables location of a mobile
`object, either as regards its distance from one or
`more points,
`its direction from one or more
`points, or both.
`'
`The invention is particularly, but not exclu-
`sively, applicable in conjunction with the radio
`sonde whereby the position of a balloon carrying
`a radio sonde, or radiometerograph, may be de-
`termined at all times. This is a valuable appli-
`cation of the invention as the geographic posi-
`tion at which thegtemperature and humidity and
`other meterological factors are being measured
`by the radio sonde constitutes desirable knowl-
`edge in the art of radiometeorography.
`I-Ieretofore it has been necessary to take cross
`bearings with the radio direction finder in order
`to determine the distance to the radio sonde.
`This method is inaccurate and difilcult as the
`ultra-high radio-frequency signals
`from the‘
`radio sonde give wrong indications of direction
`as they are refracted, reflected and diffracted by
`abrupt changes in the density of the air due to
`marked changes in its humidity. Such errors
`in two or more bearings, when used to obtain
`a position indication, result in marked errors in
`determining the distance to or geographic loca-
`tion of the mobile object.
`a
`One object of my invention is therefore to pro-
`vide for locating a mobile object, without entire
`reliance on azimuthal direction finding at two or
`more widely separated points, by measuring the
`distance directly, by the time required for a sig-
`nal to go to the mobile object and be re-trans-
`mitted back to the starting point. This accu-
`rate determination of distance, combined with an
`azimuthal bearing taken preferably from the
`point of origin of the distance determination sig-
`nal, serves to give a geographic location of the
`mobile object with much greater accuracy than
`heretofore, when cross bearings were employed.
`There are also many advantages of determining
`the geographic location of a mobile object from
`a single station as no communication between
`widely separated points is necessary when mak-
`ing a measurement as is the case when cross
`bearings are taken.
`It is understood. however,
`that my method is applicable in many combina-
`tions, and may be applied without resort to direc-
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`tion finding at all, if distance determinations are
`made from two separated points.
`Briefly this novel method of distance finding
`and position determination involves the trans-
`mission of a radio-frequency carrier. wave to a
`mobile object. This ‘carrier wave may ‘be mod-
`ulated in various ways, as by a suitable modula-
`tion frequency or by interruption at a suitable
`~ pulse rate. This carrier wave is received by a
`10
`receiving means on the mobile object. amplified.
`and applied to modulate an ultra-high radio-
`frequency transmitter on the mobile object op-
`erating at a distinguishable carrier frequency
`compared to that of the original modulated car-
`rier wave.
`(This may be the radio-meteorograph
`transmitter in the case of its use in radiome-
`teorography). This modulated ultra-high radio-
`frequency signal from the mobile object (segre-
`gable from the original modulated carrier wave
`due to its distinguishable carrier frequency) is
`again received at, at least, one ground station.
`preferably located at the point of origin of the
`original signal. The modulation is detected and
`applied to an oscillograph along with some of the
`ordinal modulation frequency or pulse. From
`the figure or spacing of figures thus produced,
`the distance and functions of the distance such
`as rate of lateral motion of the mobile object may
`be determined. Such determinations at two sep-
`arate points make possible the determination of
`the position of the mobile object. or such a deter-
`mination of distance together with an azimuthal
`bearing, preferably taken at the same station,
`‘makes it possible to determine the position of the
`mobile object.
`‘-
`Other and further objects of my invention will
`be apparent from the following detailed descrip-
`tion and accompanying drawings. It is expressly
`understood, however, that these drawings are
`for the purpose of illustration only and not de-
`singed for a definition of the limits of my inven-
`tion. Referring to the illustrations—-
`Fig. 1 shows a combination in which the sig-
`nal transmitted to the mobile object is modulated
`by a sinusoidal wave.
`'
`Fig. 2 shows a similar combination with the
`addition of an electronic switch so that two or
`more Lissajous figures may be superimposed, one
`figure forming a zero or reference.
`Fig. 3 shows a combination in which the signal
`transmitted to the balloon is broken into pulses.
`Fig. 4 shows a combination using the pulse
`transmission of Fig. 3 with the addition of aux-
`iliary direction finding means.
`Referring more in detail to the illustrative em-
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`PETITIONERS 1005-0003
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`

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`2,582,971
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`3
`bodiments represented in the drawings, the em-
`bodiment shown in Fig.
`1 comprises a radio
`transmitter I which may operate at any con-
`venient high-frequency such, for example, as 15
`megacycles, and which is provided with a radiat-
`ing antenna 2, and with a modulator‘ 3 which
`may operate to modulate the transmitter signal
`at any desirable frequency or band of frequen-
`cies preferably from 10 to 20 kc. The higher the
`frequency of the modulator 3, the more sensitive
`the distance determination indications become.
`A part of the output of modulator 3 in the form
`shown. is passed through a phase shifter 4 with
`indicator 6 and scale 5 calibrated in angle of
`phase shift. The output of shifted phase is con-_
`nected from phase shifter 4 to the horizontal
`plates II? of oscillograph 1. By means of phase
`shifter 4, therefore, the phase of the voltage de-
`livered to these plates may be shifted through
`known angles.
`The vertical plates 1' of the oscillograph 1 in
`the form shown are connected to the output of
`an ultra high frequency receiver 8, coupled
`through coil 9 to receiving antenna I0.
`The modulated wave I2 radiated from antenna
`2 is received by the mobile receiving antenna I5,
`carried by the mobile object II, which in the form
`shown is rendered ambulant by balloon 23, and
`may be termed an ambulant or repeater station.
`In the form shown the mobile receiving antenna
`I5 tuned to the radio frequency of the trans-
`mitter I, is coupled by coupling coils I6 to the
`radio-frequency amplifier I1 for the radio fre-
`quency of transmitter I, thence to a detector I8,
`an amplifier is for the frequency or band of fre-
`quencies impressed on transmitter
`I by mod-
`ulator 3, and thence to ultra high radio frequency
`oscillator 20 which is modulated by the output of
`amplifier I9 and the output of which is coupled
`through coil 2| to the mobile radiating antenna
`22. Oscillator 20 may operate on any convenient
`ultra high radio frequency, say, for example, 65
`megacycles. The modulated radiated wave I3
`from mobile antenna 22 is received by antenna I 0
`and receiver 8 (preferably located, as shown, at
`the signal originating station) and the output of
`receiver 8 (which consists of the original mod-
`ulation impressed on transmitter I by modulator
`3) is applied to the vertical plates 1’ of oscillo-
`graph 1.
`With this arrangement, if the modulation car-
`ried by carrier I3 is 90° out of phase with the
`original modulation supplied by modulator 3
`through phase shift indicator 4 to plates I I’, then
`a circle will be observed at I2’.
`If they are in
`phase a straight line sloping 45° will be observed.
`and if out of phase by 180° then the 45° slope
`will be in the opposite direction. By operating
`phase shift member 4 so that the figure I2’ is
`held in deflnite form, say, a circle, the difler-
`ence in phase of the modulation on carrier I3
`and the original modulation supplied. by mod- *
`ilator 3 can be continuously measured.
`Knowing the phase relationship for one known
`relative position of the two stations (as the phase
`:elation.at the moment the mobile radio-sonde
`s released, for example) and knowing the fre-
`luency of modulator 3 and the velocity of wave
`wropagation, 186,000 miles per second, then the
`;otal shift of phase in any elapsed period of
`;ime is a direct indication of the amount by
`vhich the radial distance between the two sta-
`;ions has changed in that period of time, and
`ietermines the total radial distance therebe-
`ween. Or, otherwise expressed, knowing the
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`phase shift per unit of time, the frequency of
`modulator I, and the velocity of propagation of
`radio waves 186,000 miles per second, the radial
`Speed of the mobile object is easily determined,
`and knowing each increment of radial speed from
`the time of takeoff, the radial distance to the
`mobile object
`is known at each instant.
`A
`graphical record against time may be made of
`the position of pointer 6 as moved to hold a circle
`at I2’ from which each increment of speed may
`be read of! and added up to give distance at any
`instant.
`If desired this may be done automati-
`cally by means known to the art so that the
`radial distance to the balloon at any instant may
`be read from a graph.
`As as example of the determination of distance
`by the above embodiment of the invention, as-
`suming the modulation frequency of modulator 3
`is set at, say 10,000. cycles per second, then 1
`cycle of the 10,000 cycles (or 360° of phase shift)
`is equivalent to ‘/1o.ooo of 186,000 miles per second
`(velocity of radio waves) which amounts to 18.6
`miles. As the signal must go to the mobile ob-
`ject
`I4 and return, the corresponding one-way
`distance would amount to 9.3,miles. Now, if, as
`in the assumed case 360° equal 9.3 miles, then 1"
`of phase shift represents .0258 mile of one-way
`distance. Thus each degree of phase difference
`registered by phase shift meter 4 means the
`mobile object has moved radially by .0258 mile,
`or 136.4 feet.
`If a frequency of 2000 cycles per
`second is employed, then each 360° of phase shift
`represents 46.5 miles of one-way distance.
`From these facts it will be apparent that great
`sensitivity to distance change can be obtained by
`this invention while guarding against loss ‘of an
`increment of distance corresponding to a sub-
`stantial change, as plus or minus one or more
`complete 360° phase shifts, which might be oc-
`casioned if reception of the corresponding very
`high modulation frequency were interrupted for
`a substantial period. This may be done by
`shifting periodically, as for a. short interval once
`in every few minutes, from the principal and
`sensitive high frequency of modulation,
`to a
`secondary,
`low frequency of modulation, pro-
`viding for following within-a single complete
`cycle of phase shift, a much greater travel dis-
`tance of the mobile object. With this arrange-
`ment any loss of the high frequency modulation
`over a period of time less than one complete
`cycle of phase shift of the low-frequency mod-
`ulation may be caught up even if both signals
`' are interrupted, and more, if the low frequency
`55
`signal is not interrupted.
`Furthermore, while I have illustrated my pre-
`ferred arrangement comprising a goniometer
`means 4-7 for following and counting the cycles
`a phase shift, the broader aspects of the inven-
`tion are not limited thereto, and the shifts of
`phase may be followed without use of the phase
`shifter 4 by counting the changes in the Lissajous
`curve from circular to linear and return to cir-
`cular which occurs if the phase shifter I is left
`at a fixed setting or omitted.
`As also indicated in Fig. 1, if it is desired to
`obtain distance indications at more than one
`point of reception to enable direction determina-
`tion by triangulation, this may be accomplished
`in any of the forms of the invention ‘shown, by
`setting up a duplicate of the receiver arrange-
`ment at another station of known location rel-
`ative to the station at receiving point
`I 0. The
`time reference may be obtained at this second
`receiving point, by any suitable means, such, for
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`PETITIONERS 1005-0004
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`

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`2,589,971
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`example, as direct reception at the second re-
`ceiving station of the signal from antenna 2. or
`reception of the modulation frequency thereat
`by transmission lines. such as indicated at 4",
`Fig. 1. With such an arrangement the receiver
`at the station of origin having determined the
`time for the signal to be transmitted, intercepted,
`retransmitted and received at that station, and
`the other having, determined thetime for the
`signal
`to be transmitted,
`intercepted, retrans-
`mitted and received at the second station, both
`for an initially known position of the ambulant
`station H, the changed distances from. the am-
`bulant station M to each of the receiving sta-
`tions may be determined as a basis for triangula-
`tion to locate the position of the ambulant sta-
`tion relative thereto.
`My invention further contemplates that the
`position of the ambulant station may be deter-
`mined by determining its distance from the sta-
`tion of origin, as above described, and deter-
`mining its direction from one or more other re-
`ceiving points of known position relative to the
`station of origin.
`By this arrangement with one direction find-
`ing station, known elevation of the ambulant
`station (determinable by other means in the
`case ‘of the radio sonde, or radiometeorograph)
`and known distance from a reference station
`(preferably the station of origin) the location in
`space of the ambulant station may be deter-
`mined, and with two direction finding stations
`and the known distance from the reference sta-
`tion, the position of the ambulant station in space
`may be determined without independent inform-
`ation as to its elevation.
`It will be appreciated
`in this connection, that the receiver 8, 9,
`II) of
`Fig. 1 may be a directional receiver as described
`in connection with Fig. 4 hereinafter.
`Referring now to Fig. 2. the form there shown
`comprises a combination which operates essen-
`tially as that shown in Fig. 1, except that an
`electronic switch 24 is introduced to give a fixed
`reference circle on the oscillograph from which
`it is easier to see any drift in the circle produced
`by the incoming modulation from the mobile ob-
`Ject.
`In this arrangement the elements I, 2. 3
`are the same as in Fig. 1. as are the elements on
`the mobile object Ill. The receiver 8. coil 9 and
`antenna II) are also the same, as is oscillograph ‘l.
`The phase shift meter 4 is the same but includes
`a comptometer 6’ arranged to algebraically record
`the number of complete revolutions of the full-
`cycle phase indicator 8, and the phase shift meter
`4 is connected to the output of receiver 0 so the
`phase of the received modulation delivered to
`terminals 26 of electronic switch 24 may be held
`equal to the phase of the voltage delivered to
`terminals 25 by the modulator 3, to the output
`of which said input terminals 25 of the electronic
`switch are also connected. The electronic switch
`may be of any suitable form, for example, of the
`type 150 made by Allen B. Dumpnt Laboratories,
`Upper Montclair, N. J. When the electronic
`switch connects terminals 25 to the output 21
`and to vertical plates 1' then a circle 4' is formed
`since the same source is connected to both the
`horizontal and vertical plates of oscillograph 28.
`This circle provides a fixed reference from which
`the drift of the other figure 3' may be observed.
`Figure 3’ is formed when the electronic switch
`operates to connect terminals 28 to 21 and plates
`1', and is produced by the signal I3 received from
`the mobile object M. since the switching rate is
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`Very rapid the circle 4.’ and figure I‘ are observed
`simultaneously.
`There is also shown in Fig. 2 an amusement
`whereby direction, as well as radial distance, may
`5 be determined by the triangulation data ob-
`tained by reception of the signal at two receiv-
`ing stations.
`In the form shown control is cen-
`tralized at the station of origin as is preferred.
`In this instance a second receiving station is
`provided at a known distance from receiving sta-
`'tions 8, 9,
`I0, comprising parts I’, I’, and II‘
`which may be duplicates of parts I, I. II. The
`output from this second receiver I’, I’, I0’, is in
`the form shown connected by transmission line
`8a to a second phase shifter la, ‘similar to phase
`shifter 4, and phase shifter la is connected by
`lines lb to electronic switch 24: a suitable switch-
`ing means, shown as two single-pole single-throw
`switches us, being provided to enable either or
`both phased receiver outputs to be connected to
`the electronic switch 24 for supply to plates 1' of
`oscillograph 1. As the receiver I, I, ll enables
`the determination of the distance if to be ob-
`tained as above explained, and as the time lag
`from receiver 8', 0’, ll’ 'te phase shifter la is
`known (or eliminated by the initial reading for
`a known position of the ambulant station) it is
`apparent that the distance I3’ from the ambulant
`station to the second receiver I0’. I’. 0', may be
`closely determined by closely following a read-
`ing on receiver 8, 9, It by a reading on receiver
`8', 8',
`lo’ and coordinating the two readings.
`The two distances I3 and II’ being determined,
`and the distance from receiver I, I. It to re-
`ceiver 8’, 9’,
`ll)’ being known, the position of the
`ambulant station It may be determined by tri-
`angulation, and may be azimuthally determined
`by correction for the elevation of the ambulant
`station, which elevation may be determined in
`any suitable manner, as by an altitude indicat-
`ing signal from a radiometeorograph carried by
`ambulant station It.
`If desired,
`transmission
`line 8a may be replaced by a radio-link, inter-
`posed between receiver 8' and phase shifter la.
`Furthermore, by the arrangement shown, by
`adjusting the output of phaseshifters I and la
`to different amplitudes and closing both switches
`of switching means 24a, a Lissajous figure (not
`shown) which will be similar to the figure 3’
`50 but of different size, may be added to the visual
`indications of the oscillograph, and by keeping
`the three figures of the oscillograph concentric
`by manipulating phase shifters 4 and la the two
`distance determinations, one for each receiving
`55 point, may be concurrently found.
`0
`In the form shown in Fig. 3 pulse transmission
`takes the place of a steady modulation. The time
`taken for a pulse to go to the mobile object, be
`received, and reradiated, and received back at its
`no source is a measure of the radial distance to the
`mobile object. The velocity of propagation of
`radio waves and the time constant of the receiver
`and transmitter on the mobile object being
`known, the time interval is readily measured by
`an oscillograph in accordance with this inven-
`tion, preferably by attenuating the‘ reference and
`received signal pulses along a time axis.
`In the embodiment of Fig. 3, the radio trans-
`mitter 32 may operate at any convenient high
`radio frequency, for example, 15 megacycles, and
`is provided with a pulse modulator 3! so that the
`transmitter 32 radiates its carrier 38 in the form
`of very short pulses separated by suitable short
`time intervals. Antenna 2 radiates these pulses
`75 86 into space where they are received at the
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`PETITIONERS 1005-0005
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`2,589,971
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`'7
`mobile obJect- II by antenna is tuned to the
`carrier frequency of transmitter 32. The pulse
`of carrier 38 passes from antenna I5 through
`coupling means shown as coils ii to radio-fre-
`quency a-mplifier 39 tuned to the carrier fre-
`quency of transmitter 32, and thence to a de-
`tector 4o for rectifying the radio-frequency pulse
`36. From detector 40 the direct current pulse is
`amplified by direct current amplifier 4|, the out-
`put of which is applied to ultra high radio fre-
`quency transmitter 42 which may be of any suit-
`able type, but preferably of the type that has the
`grids of its tubes normally biased to stop it from
`functioning but which is caused to function by
`the pulse voltages which neutralize the bias volt-
`ages. The 15-megacycle pulses received by an-
`tenna l5 are thus reradiated in the form of ultra
`high radio frequency‘ pulses 31, 31’ by trans-
`mitter 42, shown as coupled to antenna 22 by
`means of coil 2|. The reradiated pulses 31 are
`received by antenna in which is coupled through
`coils 9 to ultra high radio frequency receiver 34.
`This receiver comprises an ultra high radio fre-
`quency amplifier tuned to transmitter 42, a de-
`tector, and a direct current pulse amplifier. The
`direct current pulse output of amplifier 34, is im-
`pressed on vertical deflecting plates 1’ of oscil-
`lograph 1, which plates 1' are also excited by the
`pulse modulator 33. Horizontal deflecting plates
`4’ are connected to the sweep frequency oscil-
`later 35 which is standard oscillograph equip-
`ment. The local pulse from 33 produces the
`reference figure 3| on oscillograph 1 and the re-
`radiated pulse from the mobile object the figure
`30. Knowing the traverse speed of sweep fre-
`quency oscillator 35 and the distance between
`figure 3| and 30, the time taken for the pulse to
`go to the mobile object, pass through it and re-
`turn to the point of origin, may be found. Know-
`.ng the time constant of the apparatus on mobile
`abject 38 and the velocity of propagation of radio
`waves, the distance to the mobile object may be
`jetermined. Thus, if the oscillograph shows that
`.t took 1/500 second for the radio wave to go to
`;he mobile object and return and the time con-
`stant of the receiver and transmitter on the
`nobile object is 1/1000 second, then it took .1/moo
`;econd to traverse the space to the mobile object
`and back. 1/iooo><186,0000=186 miles or 93 miles
`'0 the mobile object.
`'
`The time constant of the apparatus may be
`-eadily determined by determining the spacing of
`|0—3i along the time axis for a known distance
`I6—31, calculating the part of the separation of
`igures 3lJ——3l along the time axis due ‘to the
`:nown distance, 36—31, and subtracting that part
`pf the separation from the total separation to
`letermine the part of the separation 3ll——3l along
`be time axis due to the constants of the appa-
`atus. Or, if differences of separation of 30-3!
`or unknown distances 36 are determined with
`eference to the initial separation of 30—3l for
`. known distance, as indications of the incre-
`nents of distance added,
`then the time con-
`tants of the apparatus are directly eliminated
`.nd need not be determined.
`As described in connection with Figs. 1 and 2,
`.istance indication may also be obtained in the
`mbodiment of Fig. 3, as by providing an addi-
`ional retransmission receiver similar to receiver
`0, 9, 34, at a known distance therefrom, as indi-
`ated at I0’, 9', 34’, in which event this addi-
`ional receiver may be connected, as shown, for
`>cal control at the primary reception station as
`y means of transmission line 34a. and suitable
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`switches 34b, 34c, enabling the output of either
`or both receivers to be coupled to oscillograph 7-
`With this arrangement use of the two receivers
`alternatively, one immediately following the other
`will determine distances 31 and 31' as described
`in connection with Fig. 2; or use of the two re-
`ceivers 34 and 34' concurrently (particularly if
`the distance separating them is such that the
`signal from receiver 34’ will arrive at the oscil-
`lograph in Phase with that from receiver 34 when
`the mobile station‘ I4 is equi-distant from the
`two receivers, or if one or the other of their out-
`puts is so "controlled in phase by a phase shifter
`like that disclosed in Fig. 2 as to effect this re-
`sult) will produce two received signal humps 33
`in the figure of oscillograph‘ 1 (as described in
`connection with Fig. 4) -the spacing between
`which will then correspond to the distance 31’.
`These distance determinations, with the known
`separation of stations 34 and 34’ will then deter-
`mine the location of mobile station 38, as de-
`scribed in connection with mobile station I4
`shown in Fig. 2.
`Knowing the distances to a mobile object of
`known altitude from two geographically separated
`points. the geographic location of the mobile ob-
`ject is known. Thus, if, instead of providing a sec-
`ond receiving installation only (as indicated‘ at
`4" in Fig. 1, at 8a in Fig. 2, and at 3411 in Fig. 3)
`a complete apparatus such as is otherwise shown
`30
`' in Fig. 1. 2 or 3, is located at two or more points,
`the position of a mobile object may also be found,
`by coordinating the two independent distance
`records to the same time axis.
`.
`-
`In Fig. 4 is shown a combination-in which the
`positional’ a mobile object may be found with
`receiving and transmitting apparatus all located
`at a single location.
`In this instance the trans-
`mitting and receiving equipment at the ground‘
`station, and the equipment on the mobile object-
`may be the same as that shown in Fig. 3 and may
`be operated in the same manner to determine the
`distance to the mobile object. Directional receiv-
`ing equipment is however added or substituted so
`that the azimuthal location of the mobile object
`may be found. An important novel aspect of this
`equipment is that it eliminates the errors in bear-
`ings due to spurious refiecte . refracted and dif-
`fracted waves which may co e over indirect paths
`from the mobile object. With this type of direc-
`tion finder the bearing is taken only on the wave
`that reaches the receiving point first which gives
`the true hearing as it has traveled over
`the
`straight path.
`In Fig. 4, there is represented a
`conventional form of direction finder with ver-
`tical doublets 45, 46, and 41 arranged in the man-
`ner of a Yagi array, rotatable about a vertical
`axis by means of shaft 48, with pointer 53 and
`scale 52. Doublet 46 is connected to slip rings 50.
`50’ by means of transmission lines 49, 49’.
`Brushes 5|, 5|’ connect the slip rings to ultra
`high radio frequency receiver‘44 which is similar
`to and may be used together with or in lieu of
`receiver 34, as indicated by switches 44a and 34a.
`The output of the directional receiver 44 is ap-
`plied (together with or in lieu of the output of
`non-directional receiver 34)
`to one set, as the
`vertical set, of deflecting plates of the oscillograph
`to be employed, two oscillographs 1 and 54, having
`defiecting plates 1’ and 55 respectively, and oper-
`able with different sweep speeds, being shown in
`this connection. When the outputs of both
`receivers are to be applied to the oscillograph or
`oscillographs so that the oscillograph figures will
`have a certain observable amplitude at all times,
`
`75
`
`PETITIONERS 1005-0006
`
`

`
`2,582,971
`
`9
`at least one of the receivers is preferably provided
`with an adjustable time-lag device as Mb, which
`may be of the well known resistance-capacity net-
`work type. to enable adjustment of the two out-
`puts to synchronism with one another. To
`provide
`the reference hump,
`in the form
`shown, the output of the local pulse generator 33
`is also connected to the vertical defiecting plates
`of the oscillograph or oscillographs being used, 1’
`and 55 in the form shown. The other set of oscil-
`lograph plates (I I’ and 56 herein) of the oscil-
`lograph being used‘ is connected to the oscillo-
`graph sweep frequency generator. Two such
`generators are shown in the illustrative embodi-
`ment; a high-speed generator 35 to produce the
`more attenuated figure 30-3! of oscillograph 1,
`and a slower speed generator 50 to produce the
`more comprehensive figure-51, 58, 59 of oscil-
`lograph 54.
`In the form shown both sweep fre-
`quency generators are of the type triggered to
`commence the sweep by pulse frequency generator
`33 as indicated by the connections 33a, to start
`the traverse concurrently with the start of the
`pulse of pulse generator 33 producing figure 3|
`and 59.
`When this system is operating the local pulse
`produces figure 59 (and figure 3|) and the direct
`one from the mobile object travelling over path
`6! produces figure 58 (and figure 30). The in-
`direct pulse 63 reflected from cloud layer or
`humidity front 62 produces the figure 51 which
`arrives somewhat later than the directly trans-
`mitted pulse 6 I. In operation the direction finder
`is oriented until the pulse producing figure 58 (the
`one travelling over the shortest route) produces
`a maximum (or minimum) defiection in figure 58.
`When this point is found the azimuthal bearing
`is read opposite pointer 53 on scale 52.
`It is
`understood that any conventional form of direc-
`tion finder suitable for taking azimuthal bearings
`on ultra-high radio frequencies may be used in
`the place of the one shown with its output con-
`nected to the visual pulse indicator as shown.
`Knowing the azimuthal bearing to the mobile ob-
`ject, and the distance to it, its geographical loca-
`tion is known.
`The employment of two oscillographs, as 1 and
`54, renders it possible to conduct adjustment of
`one, to change its horizontal scale, while con-
`tinuing readings on the other, it being desirable
`to maintain the horizontal scale of one oscil-
`lograph to widely separate the humps, as 30 and
`3|, to facilitate accurate determination of the
`time lag, but to have the other adjusted with the
`humps more closely spaced, as 59, 58, 51, so that
`when hump 30 moves out of the frame, due say
`to increase of distance to the mobile object, cor-
`responding hump 58 will remain on oscillograph
`55, and be continuously observable, during change
`of the sweep-speed of oscillograph 1, and vice-
`versa.
`If, however, this advantage is not desired,
`it will be appreciated that one of the oscillographs
`and its sweep-frequency generator may be omitted
`without departing from the broader aspects of
`this invention.
`‘
`Similarly, it is desirable than non-directional
`receiver 34 be available in addition to directional
`receiver 44, so that a continuous check on distance
`may be had, undisturbed by loss of signal on re-
`orientation of the directional receiving antenna
`45, 48, 41. This may be done either by closing
`the switch 34!;
`if and when the directionally
`received signal is lost, or by keeping the switch
`34:; closed to always assure a minimum ampli-
`tude of humps in the oscillograph figures,
`in
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`10
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`’
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`15
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`20
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`25
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`30
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`35
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`40
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`10
`which case the outputs of the two receivers should
`be phased, as by the means Nb described. The
`switch Ma is of course kept closed whenever direc-
`tional reception is desired, and it will be apparent
`that if the advantage of the availability of two
`receivers, or the equivalent thereof, is not de-
`sired, receiver 34 may be omitted and the distance
`and direction indications may both be obtained
`from receiver 44, care being taken to not lose the
`signal by excessive manipulation of antenna 65.
`46, 41.
`From the above description it is obvious that
`the invention is not limited to the particular em-
`bodiments described and the subject matter of
`the invention as set forth in the following claims.
`is to be interpreted accordingly.
`I claim:
`1. A method for determining direction and dis-
`tance between two relatively ambulant stations
`which comprises transmitting a signal from one
`of said stations as a station of origin, intercept-
`ing and retransmitting the signal at the other of
`said stations as a repeater station, and receiving
`the repeated signal by directional reception at
`said station of origin where the portion of said
`signal travelling a direct path will be received
`ahead of the portion- thereof travelling an in-
`direct path, establishing the elapsed time between
`t