Патент USA US2406358код для вставки
Aug. 27, 1946. S. DOBA, JR yGROUND SPEED METER Filed March 2l, 1944 „wenn 2,406,358 5 Sheets-Sheet 1 b5. I.. \. n h wuz;. E /N VEN TOR BY S. 008A, JR. AGENT Aug. 27, ì946.« 2,406,358 S. DOBA, JR GROUND lSPEED METER ` Filed March 21, 1944 ämQ 5 Sheets-Sheet 2 md. .miv /NVE/vrof? S. 008A, JR. BV AGENTv Aug. 27, 1946..V ì s, DQBA, JR 2,495,358 GROUND SPEED METER Filed March 21, 1944 5 Sheets-Sheet 3 /N VEN TOR S. DOB/I, JR. A @r1 AGENT' Àug. 27, 1946. s. DoBA, JR GROUND SPEED METER \ Filed March 21, 1944 2,406,353 1 s sheets-sheet 4 AGE/vr A Aug. 27, 1946.’ s.- DoBA, JR (3,406,358 GROUND SPEED METER v Filed March 21, m44 5 sheets-sheet 5 „VvE/WOR ¿I DOBA, JR Patented Aug. 27, 1946 2,4%,358 2,406,358 GROUND SPEED METER Stephen Doha, Jr., Long llsland City, N. Y., as signor to Bell Telephone Laboratories, Incor porated, New York, N. Y., a corporation of New York Application March 21, 1944, Serial No. 527,459 4 Claims. (Cl. Z50-1) l MB, video amplifier l'lû and vertical sweep am pliñer 20G of Fig. 1; and This invention relates to an improved method and apparatus for measuring the relative speed Figs. 9A and 9B illustrate the patterns on oscil loscope screen 2 produced when switch S is closed of an observer and an observed object visible or invisible. The invention while particularly use ful in a military airplane ñying to-ward a target ahead, has a field of use including all cases of relative movement in the air, at sea or on land~ upward and downward, respectively. In all figures like numerals and letters indicate like elements. The invention will be described with reference The general object of the invention, therefore, to its use in an airplane which will be understood is to provide a method and means for measuring the relative speed at which an observer ap proaches an observed position. The invention makes use of known electrical object locating and ranging means which are in to be provided with the usual altimeter and air speed meter. For simplicity, it will be assumed that the plane is flying directly, without leeway, toward a target ahead. Referring now to Fig. 1, the radar system gen dependent of weather and light, making such means an element in a novel system of appara 15 erally indicated by numeral l, not itself a part of the present invention but here briefly described to facilitate understanding of the complete sys tus for measuring the rate of change of range of a selected object. The invention thus achieves another object, namely, to provide speed meas tem, serves to detect the presence of a target uring means useful in all conditions of observa ahead and represent that target by a luminous tion. In bombing an enemy target from an airplane, it is obviously important to know the relative speed of target and bombing plane. Hence an 20 spot T on screen 2 of cathode ray oscilloscope 3. The location of spot T on screen 2 corresponds as later explained to the range and bearing, at a given instant, of the target represented. System l includes a pulse transmitting circuit other object of the invention is to facilitate the prosecution or war in the air, as well as to pro vide a navigational aid universally useful in time 25 4 and a pulse receiving circuit 5 connected through duplexing unit 6 to a common antenna 'l which is preferably of the highly directive type consisting of a small polarized dipole 8 at the The invention enables the pilot of an airplane focus of a, parabolic reflector 9. Antenna 'i is to measure his absolute speed with respect to a point ahead. If that point is fixed on the earth’s 30 connected by a coaxial link Ill through duplexing unit 6 to the circuits ¿i and 5, with a rotary joint surface and its initial distance is large compared Il in link lil. The portion of link iû above joint with the plane’s altitude, the absolute speed H is provided with gearing l2 through which mo measured is substantially the ground speed of tor i3 is enabled to rotate antenna 'l at a con the plane, For example, ii the altitude is 10,000 feet and the distance on the earth’s surface is 35 stant speed in the horizontal plane. Rotation of antenna ’I in a vertical plane may be accom 50,000 feet between the point of reference and a plished by a like arrangement of motor and gear point vertically beneath the plane, the speed ing which is omitted here as unnecessary to the measured is 98 per cent of the ground speed. For oi peace. present description. The pulse generator i4 sup a surface craft the measurement requires no cor rection. In neither case does a head or a tail 40 plies a positive square top pulse of very short du ration to control radio modulator i5 to supply at wind or ocean current affect the measurement of a convenient repetition rate extremely short and intense pulses of radio frequency energy to an tenna ‘l by which these pulses are directively ra diated into space. Duplexing unit 6, which may speed, Therefore, another object of the inven tion is to provide navigators with means for measuring ground speed regardless of wind or current. The invention is to be understood from the fol lowing description, read with reference to the ac companying drawings in which: be an automatic transmitter-receiver switch of any known type, eiîectively short-circuits the in put to receiving circuit 5 while antenna ‘i is emit ting but allows free passage to circuit 5 of the low level echo received by antenna 1 from a reflect ing target. The interval between successive emissions by antenna 'i is made longer than Fig. l is a block schematic diagram of the ma jor components of the invention; Figs. 2 to 8 are circuit diagrams representing, respectively, time base generator 2d, range sweep generator El), rate sweep generator 8%, range dii ferential amplifier lill, video mixing amplifier , enough to include the reception of radio echoes 55 from the most distant target to be attached. A portion of the energy radiated by antenna 2,406,358 3 Y 4 adjustable initial value and at an adjustable rate of decrease. This sweep voltageoccupies from 100 to 400 seconds to decrease through a range received by antenna l and 'transformed into an of 100 volts, so that throughout any 100 micro electrical pulse which passes through duplexing second interval it may be considered constant. unit 6 to radio receiver iii in circuit 5 where it is The output of generator d@ is likewise applied to ampliiied and detected. The detected pulse is range differential amplifier l lil. Obviously, the further ampliiied by video ainpliñer Il’ and is initial value of the decreasing .output voltage oi thus available to produce intensity modulation generator Sli may be chosen less than the maxi~ of the cathode ray beam of oscilloscope 3. Os cilloscope 3 may be of the Well-known magnetic 10 mum value reached by the rising voltage of genn erator E@ so that in each lo() microsecond intern deflection type and is not shown in detail in Fig. val there will be an instant of equality oi the 1 beyond intensity grid i8, cathode i9, ñuorescent two voltages on the input of differential screen 2 and deiiecting coils HDC‘ and VDC for ampliñer lle. As the voltage from generator ílâì horizontal and vertical beam deflection, respec -slowly decreases this instant of equality will oc~ tively. cur progressively nearer to the start of the lo() vShaft 2E, through which motor i3 drives gear microsecond interval, that is to say, nearer to l2, carries a pair of potentiometer wipers 2l and the moment Of emission of object ranging pulse 2|’ insulated from each other and from Vshaft 2l) from antenna l. Y on which they are mounted radially opposite each To anticipate the later description, it may here other. Wipers 2i and 2i’ traverse potentiometer be said that the voltage from generator Si? is so 22 fixed in the airplane. Battery 23 is connected chosen that at a given time the instant of equa-1 across diametrically opposite points of potentiom ity of the sweep voltages from generators d@ and eter 22. The rotation with shaft 2li of wipers 2l 85B occurs simultaneously with the reception by and ‘2l’ selects a fraction of the voltage of bat tery 23 ranging from zero when the pointing of 25 antenna 'l of an echo reflected from a chosen target and the rate of decrease of the voltage antenna 'l is directly ahead to a maximum when from generator 8@ is so adjusted that this in antenna l points abeam. The polarity oi the . stant continues to occur simultaneously with the selected voltage depends on the left or right reiiected echo as the range of the target decreases. pointing of antenna l and the voltage so selected is applied to produce a current in horizontal de~ 30 Clearly, the means which so sets the rate of volt 'l is intercepted and reflected, usually diffusely, by the target. A part of this reflected portion is age decrease affords a measure of the rate o_i iiecting coil HDC of oscilloscope 3. Auxiliary change of range of the target, that is to say, of means, not shown, are provided for horizontal the relative speed of target and plane. If the centering when wipers of 2l theand cathode 2l’ select ray zero beamvoltage. on screen target is stationary and the plane’s altitude is When the echo pulse from the reilecting target 35 not a large fraction of the plane to target dis» tance,. the speed so measured is the ground speed is available on grid is to produce intensity rnodu of the airplane. lation of the cathode ray beam a luminous spot Before continuing the functional description oi T representing the target will appear on screen the system of Fig. l it is proper here to describe 2 located vertically thereon at a position corre the circuits so far involved. sponding to the target range provided a vertical eferring new to Fig. 2 a short positive trigger sweep current, synchronized with the emission of pulse from pulse generator if: is applied to grid energy from antenna l, is caused to flow in ver tical deîlecting coil VDC. The horizontal sweep 'differentiation of the tube V1, bywhich the circuit is suitably comprising SSTL‘E'Z, con current in coil HRC insures that the target spot will appear displaced left or right on screen 2 according to the bearing of the target left or right. For the present purpose, it is assumed that the target is directly ahead. It is convenient to describe functionally the op eration of some of the major components of the system of Fig. l., postponing the detailed descrip tion of the involved circuits. Each trigger pulse from pulse generator i4 ini tiates the emission of a pulse of radio frequency energy from antenna l and at the saine time is ’ supplied to actuate time base generator 24. Gen erator 2s produces a pair of voltage pulses oi op posite polarity and lasting for approximately 10€) microseconds, which are both supplied to range sweep generator 5B, the negative pulse serving to f excite in generator 5E! a positive sweep voltage rising through a voltage range of about 10G volts linearly with time at a predetermined rate throughout the 100 rnicrosecond interval, the positive pulse producing a positive pedestal volt~ age on which is superposed the rising sweep volt age, This sweep voltage on a pedestal recurs with each radar emission and starts simultaneously therewith. ït is supplied by range sweep genera~ tor El? at all times to range differential ampliñer Hf! and when switch S is closed upwards it is fractionally supplied also to vertical sweep am denser ”¿5 and resistance E?. Grid 225i tube V1 ~ is negatively biased by battery 28 so that tube Vi is normally not conducting. Differcntiating circuitv CZSRZ'E produces a positive pip at the leading edge of the trigger pulse, an instant here~ inafter designated as to. _fi -Á trailing edge on the trigger pulse is disregarded. Prior to the arrival of the positive pip on grid 25 no anode current flows in tube V1 and there is no voltage drop across the resistor 29 through which anode 3B of V1 is connected to 300 Volt battery 3l. Battery 3| is also connected through resistor 32 to-anode 33 of tube V2, a double triode such as a 6N?, through resistor 3s to grid 35 and through resistor 29 to anode 35 of V2. Cathodes 38 and 39 are electrically connected together and through resistors ¿l0 and di in series to ground. The junction of resistors lll) and 4l is connected to grid 42 through resistor ¿i3 while grid ‘d2 is shunted to ground by condenser dit. Cathode 45 of V1 is likewise grounded. ïn all circuits cathode heating power is understood to be sup plied though not shown. Between ground and cathode 39 of V2 are connected condenser ¿l5 and resistance ¿il in series, from the junction of which, through condenser 4S shunted by resistor ¿59, a square topped voltage pulse negative to ground of itil microseconds duration is fed to range sweep generator 5U. Also to generator 5S plifier 2m). a square topped voltage pulse, positive to ground, Rate sweep generator 30 produces a sweep volt» ageslowly decreasing linearly with time from an 75 is fed from anode 3,3 oi V2. Of these voltage 2,406,358 5 pulses, the former excites the rising sweep volt age produced by generator 50 while the latter 4provides the pedestal which the sweep voltage overlies. In the circuit of Fig. 2, grid 25 of V1 is normally .biased to cut-off by battery 28. Grid 42 of tube V2 is biased to cut-off by the voltage developed tive, square topped, pulse across resistors 40 and 4| due to the abrupt drop and succeeding rise of current therein, a negative pulse which is taken olf between cathode 39 and ground and is used as above stated to produce the sweep voltage in generator 50. Here the terminal distortion is harmful and is removed by the ñlter circuit com across resistors 40 and 4| in series by the flow of current in the right half of V2 from anode 33 prising condenser 46, resistor 4,1 and condenser 48 shunted by resistor 49. to cathode 38. Since grid 35 is connected through 10 The input terminals of the circuit of Fig. 2 1.5 megohm resistor 34 to battery 3|, its voltage is are A and ground G, across which the trigger pulse from generator I4 is applied. The output slightly higher than that of cathode 38, namely, about 20 volts positive to ground and the right terminals are B1, C1 and ground G1, the sweep producing pulse being taken between C1 and half of V2 is normally conducting. Condenser 31 is connected between grid 35 and anode 36. 15 ground, the pedestal pulse between B1 and ground. n A positive voltage pip drives grid 25 positive, Time base generator 24, which the circuit of Fig. 2V Y, so that V1 becomes conducting and its anode volt constitutes, defines the duration of the voltage rise in range sweep generator 58 and thus the age falls. Anode 136 of V2 is connected directly range of the most distant target to be considered. to anode 30 of V1 and through condenser 31 to grid 35 of V2. The fall of voltage at anode 30 thus is 20 The 100 microsecond interval, corresponding to a target distance of about 10 miles, is fixed by the coupled through condenser 31 to grid 35 to cut-off choice of condenser 31 and resistor 34, in the case the right half of V2, and the consequent disap described 200 micromiorofarads and 1.5 megohms. pearance of current from resistors 48 and 4| per respectively. The sweep interval is in any case mits the left half of V2 to become conducting. Initially, V1 is not conducting, anodes 30 of V1 25 preferably somewhat shorter than the interval and 36 of V2 are 300 volts positive to ground. In between successive signals from antenna 1 which in some radar installations may be long enough V2 cathodes 38 and 3B as well as grid 35 are for a 100 mile range to be dealt with. 20 volts positive while anode 33 is about 257 volts In Fig. 3 is shown the circuit of range sweep positive to ground, the right half of V2 being conducting while the left half of that tube is 30 generator 50. Input terminals for generator 50 are B2 and C2 on which are impressed positive blocked. Grid 42 of V2 is thus 20 volts negative and negative pulses from terminals B1 and C1 with respect to cathode 39 and condenser 31 is respectively, of Fig. 2, and ground G. The nega thus across a potential difference of 280 volts be tive square topped voltage pulse at terminal C1. tween anode 36 and grid 35. The positive volt age pip from differentiating circuit C26R21 makes 35 of Fig. 2 is applied at terminal C2 of Fig. 3 to V1 conducting and the potential at anodes 30 and grid 5| of tube Vs, a 6AC7, for example, initially conducting and rendered inactive when a nega 36 falls to about 165 volts. This drop of 135 volts tive pulse arrives at grid 5|. Screen grid 52 of at anode 36 is communicated through condenser V3 is supplied through resistor 55 from battery 31 to grid 35 which accordingly falls to 115 volts negative to ground cutting oiï the right half of V2 40 3 i ’ which may be the same as battery 3| serving to supply all voltages of the system of Fig. 1. so that the potential of anode 33 rises to 300 volts. Grid 52 is shunted to ground by condensery 56 The current in resistors 40 and 4| becomes mo mentarily zero, thus removing the 20 volt nega while suppressor grid 53 and cathode 54 are grounded. Anode 51 is supplied through re tive bias on grid 42 so that the left half of V2 becomes conducting, its anode 36 remaining 165 45 sistor 58 and bias control tube V5, a diode such volts positive to ground. A small current now as one-half of a 6H6, from the junction of resistors ñows in cathode resistors 40 and 4| and conden 59 and 60, these resistors constitute a voltage ser 31 starts to readjust its charge to the new divider between battery 3| and ground whereby anode 6| of Vs is supplied with 50 volts. Cathode voltage difference about 146 volts, between anode 36 and grid 35. This involves a rise in poten 62 of V5 is connected through resistor 58 to tial of grid 35 which on reaching the cut-01T po anode 51 of V2. Condenser 63 shunting resistor tential -10 volts allows the right half of V2 53 is connected between anode 51 of V3 and grid to conduct. Now the flow of current of resistors 64 of tube V1 which is suitably one-half of a 40 and 4| results in cut-01T of the left half of V2 GSN'TGT. Anode 65 of V1 is supplied directly from and the initial conditions are restored. The re 55 battery 3| while between cathode 66 and ground adjustment of the charge of condenser 31 is by a are connected resistors 61 and 68 in series. partial discharge through resistor 34 and the left Resistor R, preferably 200,000 ohms, is con half of V2. The time constant C31R34 is 300 nected between cathode 66 and the junction of microseconds and the rise in potential at grid 35 condenser 63 with anode 51. Between anode 51 of V2 from 1~115 volts to -10 volts requires 100 60 and input terminal B2 are connected condensei~ microseconds. During this interval the potential C about 200 micromicrofarads, and condenser C', of anode 33 is 300 Volts rising abruptly from 267 which may be 1,000 micromicrofarads, in series. volts at the instant V1 becomes conducting and Shunting this connection of condensers C and C’ falling rapidly 100 microseconds later. This fur are condensers 69 and 10 in series serving as a nishes a 33-volt positive square topped pulse. At 65 trimming capacitance. Condenser 69 is suitably the end of the 100 microsecond interval the po an air condenser, while condenser 10 may have a tentia1 of anode 33 falls slightly below the initial capacitance of 1,000 micromicrofarads. Resistor value of 267 volts because of a small flow of cur R1. about 330,000 ohms, is inserted between rent from grid 35 to cathode 38. The 33-volt cathode 66 and the junction of condensers C positive pulse is used as pedestal voltage in range 70 and C'. sweep generator 50 and the terminal distortion is It will be observed that the positive pedestal unimportant. Condenser 44 of capacitance .006 voltage pulses from time base generator 24 applied microfarad holds grid 42 at constant voltage with to input terminal B2 is interposed between ground respect to ground. Simultaneously with the posi and the circuit of Fig. 3 to the right of tube V3. tive pulse at anode 33, there is produced a nega 75 Further, those acquainted with sweep voltage 2,406,358 7 generators, well described, for example, in “Time Bases” by O. S. Puckle, published in London in 1943, will recognize that the circuit of Fig. 3 is such a generator, inactive while tube V3 is con 10,000 ohms resistance, on ‘which tap 82 selects a fractional voltage adjusted, as later described, to be proportional to the speed of the airplane relative to the target. This fractional voltage appears across resistor 93, about 1/2‘ megohm, and ducting but generating a rapidly rising voltage from a fixed point 80 thereon about île of the starting from the instant when V3 is blocked by voltage selected by tap 82 is applied through 3 the negative pulse applied to grid 5i from gen megohm resistor 85 to grid 80 of tube V6. Cathode erator 24. .This rapidly rising voltage rises sub 81 is connected through resistor 88 to the posi stantially linearly with time and continues so to rise until the negative pulse from generator 24 10' tive terminal of battery 3| and to ground through the 300 ohms of resistors 89 and 90 in series. has passed from grid 5|. The rate of voltage rise, Variable resistor 89 is so adjusted that when tap controlled by the ratio of the voltage across con 82 _is at ground no current iiows in resistor 85. denser 83 to the product RC, is in the present Anode 9| of Vs is directly connected to cathode circuit about l volt per microsecond. This sweep voltage appears as a voltage positive to ground 1,5 92 of V7 of which grid 93 is positively biased from the junction of resistors 94 and 95 to a potential at cathode 60 to which output terminal D1 is of about 45 volts. Anode 98 of V7 is supplied from connected. Tube V4 is an ampliiier tube supply battery 3| through lO-megohm resistor 91. Sweep ing negative feedback to linearize this voltage wave as a function of time while the circuit R1C’ condenser C”, 4 microfarads, together with re is an integrating circuit further contributing to 20 sistor 85 constitutes the sweep circuit controlled by the voltage taken between point 84 and ground. the desired linearity. The output voltage from the circuit of Fig. 3 is Effectively condenser C" is connected between taken between terminal D1 and ground, or a grid 80 of Ve and anode 96 of V7, which tubes desired fraction of it may be taken between constitute a direct coupled direct current am Terminal D1 is used 25 plifier supplying negative feedback to linearize with time the variation in voltage across conwhen switch S, Fig. l,_ is closed downward, denser C”. Actually, instead of being directly terminal E1 when S is closed upward. Resistors 55, 559 and 00 are respectively about joined to anode 98, condenser C" is connected to cathode 98 of tube V8, of which grid 99 is joined 68,000, 20,000 and 100,000 ohms >while resistor 58 is 2.2 inegohrns. Resistors El' and 08 are about 30 through resistor |00 to anode 98 of V7. Anode |02 of Vs is directly supplied from battery 3|, the 250,000 and 50,000 ohms, respectively, so that the pedestal and sweep voltages at terminal E1 are load resistor of Vs being composed of voltage regulator tube V9 in series with resistor |03. each about one-sixth those at terminal D1. It will be clear from the foregoing description Across tube V9 is shunted resistor |94 which may that in the circuit of Fig. 2 tube V2 is a single~ I. be of 100,000 ohms resistance and is tapped to shot multivibrator synchronized by tube V1 with furnish at terminal F1 a desired fraction of the the trigger pulse which simultaneously actuates constant voltage across tube V9, plus the decreas terminal E1 and ground. radar system l. The output negative pulse from ing voltage across resistor |03. Battery |05, de terminal C1 controls the conductance of tubel rived from battery 3 | , provides a negative voltage V3 in the circuit of Fig. 3, and the duration of 40 to stabilize tube V9. Grid 99 of Vs is shunted to the voltage rise at terminals D1 and E1 of Fig. 3. ground by condenser |08, which with resistor This voltage rise is linearized by negative feed |00 serves to prevent oscillations of voltage at back from tube V4 and further improved in grid 99. Tube Vs functions as a cathode follower linearity by the integrating circuit R’C’, for tube so that condenser C” when connected be which values of resistance and capacity are chosen tween cathode 98 of Vs and grid 80 of V6 is effec with. regard to the values of R and C and the tively connected between that grid and anode 9S amplification factor of tube V4. Diode V5 is so of V1. To increase the amplification positive inserted that in the intervals between successive feedback is provided by resistor |07 between cath sweeps condenser 53, of .006 microfarad capaci ode 98 of Vs and cathode 81 of Ve, thereby raising tance, may be rapidly charged by diode V5 through 50 the amplification factor ofthe ampliñer circuit tube V3, which is during such intervals con to 5,000. ducting, and so be at a fixed potential at the Switch S’ is closed as shown in Fig. 4, when start of each successive pulse from tube V2. The» switch S of Fig. 1 is closed upward. Closing circuit of Fig. 3 is not itself a part of the present switch S’ connects battery 3| through 5,000 ohm invention but is disclosed and claimed in the co 55 resistor |08 to one plate of condenser C”, the pending application of J . lV. Rieke, filed March other plate thereof being connected to grid 86, 21, 1044, Serial No. 527,457, assigned to the same assignee as the present application. The voltage at terminal D varies from about 100 to about 200 volts, starting with about 65 volts during the interval between sweeps, to which a 433-volt pedestal is added at the start 0f the which is at ground potential and only about 2 volts negative to cathode 8l. Condenser C” ac cordingly charges to about 195 volts (battery |05 opposing battery 3|) positive to ground at cath ode 98, through resistor |08 and the grid-cathode circuit of Ve. This voltage also appears across tube V9 and resistor |83, 75'Volts being across The rate sweep generator, of which the circuit tube V9. Thus, the tap |09 on resistor |04 makes is shown in Fig. 4, provides a voltage slowly de 65 available at terminal F1 120 volts plus a desired creasing between terminal F1 and ground from fraction of '75 volts. This is a steady state Volt age independent of the operation of the sweep about 200 to about 100 volts over a time interval circuit of Fig. 3. The equality of this voltage varying from 11/2 to 6 minutes. The circuit of with the sweep voltage from range sweep gen Fig. 4 includes vacuum tubes Vs, V1 and Vs and voltage regulator tube V9. Suitably tubes Ve 70 erator 50 can be set by adjustment of tap |09 to occur at any desired instant in the 100 micro and V7 are respectively, the two triodes contained sweep. in a GSL'T, Va is one-half of a 6SN7GT while V9 is second interval between near its end and near its a VR75. Battery 3| supplies the voltage re quired in the circuit of Fig. 4. Across this bat beginning. When switch S’ is opened, condenser C" starts' tery is connected potentiometer 8| of about 75 to discharge through 3 megohm resistor 85, the 9 2,406,358 discharge rate being controlled by the voltage at tap 84. From the stated values of capacity of condenser C” and resistance of resistor 85 time constant C”R85 appears to be 12 seconds, but the eifective time constant determining the lin earity of the sweep is the product of this 12 sec onds by the amplification factor obtained from tubes Va, Vv and V0, namely 1,000 minutes. In the circuit of Fig. 4 enough amplification is pro 10 K the echo signal from video ampliider l1 of Fig. 1. The bias of grid M2 is controlled by tube V17. The amplified positive pulse at anode E43 of V14 and the amplified echo signal at anode |44 of V15 are applied on grid M5 of tube Vis, from the cathode circuit of Which are fed a pair of negative voltage pips corresponding respectively to the ar rival of the echo signal at terminal K and the start of the square-topped pulse applied to ter vided to make unnecessary an integrating cir 10 minal H2. For a reason later given these voltage cuit such as R’C’ of Fig. 3. By analysis of the pips are delayed 5 microseconds by network 25€). operation of Fig. 4 when switch S' is opened, it Ground terminals, not shown, are provided for may be shown that as condenser C" discharges, the circuits of Figs. 5 and 6 and subsequent grid 86 of V6 remains substantially at ground po figures. ' tential, so that the discharge current through re 15 In Fig. 'Il is shown the circuit of final video sistor 85 is determined by the voltage at tap 84. amplifier lïû. Terminal L’ receives from ter The operation is in eñect a cancellation of the minal L of Fig. 6 the negative voltage pips, de charge placed on condenser C” when S’ is closed, layed 5 microseconds by network 250, and applies by an opposing sweep charge whereby the voltage these to grid lll of tube V10 in amplifier H0. across C” is caused to fall at a rate equal to 20 The amplification and reversal of sign of `these E’/R85C” volts per second where E’ is the voltage voltage pulses is accomplished by tubes V18 and to ground at tap 84. When E’ is 12 volts the V19 so that corresponding positive voltage pips are voltage at cathode 98 and so at terminal F1 will available at terminal N, To permit these volt fall 1 volt per second, the voltage drop across V0 lages to produce traces on screen 2 of oscilloscope is constant. Therefore, if initially with S’ closed, 25 3 of Fig. l, the positive pips are superimposed on a tap |09 is at cathode £8 and E'=12 volts, the in positive pedestal voltage derived from tube V20 stant of equality of the voltages, from terminal to grid §13 of which are applied via terminal N F1 and from terminal D1 of Fig. 3 Will move when unblanking pulses that are explained in the de S’ is opened in 100 seconds from near the end to scription of Fig. 8. It is convenient to provide near the beginning of the 100 microsecond inter 30 also at terminal Z a blanking voltage, derived in val prescribed by time base generator 24. any convenient manner from radar system I to The rate sweep circuit of Fig. 4 is also nota blank the oscilloscope trace during the rearward part of the present invention but is described and pointing of antenna l. This blanking voltage claimed in the copending application of J. W. may be a positive voltage applied to grid i512 of Rieke above referred to. 35 tube V21 during such rearward pointing and re» In the system of Fig. 1, the major components placed by a ground when antenna l points for following range sweep generator 53 and the rate ward of the airplane. When present the blank sweep generator 8l] use known circuit arrange ing voltage annuls the output voltage at terminal ments and will be here described chiefly func N. Thus, only when antenna 1 points forward is tionally, reference being made to the attached the negative bias of grid i8, Fig 1, to be over drawings for the circuit details. Referring to come and the trace is brightened only when a Fig. 5, vacuum tubes V10 and V11 of range differ positive voltage pip appears at terminal N to ential ampliñer Híl receive on grids lll and H2, gether with a pedestal voltage from tube V20. respectively, the voltages appearing at points D1 In Fig. 8, the circuit of vertical sweep ampliñer of Fig. 3 and F1 of Fig. 4. Of these voltages 45 26€) comprises tubes V22, V23, V24 and V25, Tubes the first is a rising sweep voltage lasting 100 V22 and V23 are suitably the two triodes of a microseconds, the second is a voltage slowly de GSN'IGT. Their respective anodes 2Q! and 2112 creasing over a comparatively long time equaled are supplied from battery 3l through resistor 2û3. by the rising voltage at an instant in the 100 Grids 23d and 265 are biased 50 volts negative microsecond interval depending on the positions 50 by battery 295 through resistors 20T and Zíiß for of taps 82 and m9 of Fig. 4. Tube V12 is an grid 28d, 269 and 2li! for grid 205 and further amplifying tube providing positive feedback to biased by the voltage drop in common cathode tube V10 through constant current tube V13 which resistor 2i l. When switch S, Fig. l, is closed upf is inserted between ground and joined cathodes ward the fraction of the output sweep voltage of range sweep generator 5d appearing at terminal H3 and H4 of tubes V10 and V12, respectively. E1 of Fig. 3 is applied via terminal I through con The cathode current of tubes V10 and V12 is con trolled by the potential of grid H5 of V13. Tube denser` 2l2 to grid 29d. dit the same time switch S” ganged with switch S, is closed upward and V11 is a buiîer tube protecting rate sweep gener grounds the junction of resistors 281 and 238 ator 80 from loading due to grid current in tube V12, while voltage regulator tube V11 controls the 60 thereby removing from grid 266 the bias of bat screen voltage of V13. tery 206. As a result, tube V22 becomes conduct ing, increasingly so as the sweep voltage rises at It may be shown by analysis of the operation of terminal I. A correspondingly increasing current the circuit of Fig. 5 that when the voltages at terminals D2 and F2 are equal there appears a flows in resistor 2i I, At the same time a nega square-topped positive pulse at anode H6 of V12 85 tive voltage wave appears at anode 2i?! which is transferred from terminal M' to terminal M of which continues to the end of the 1GO-microsec Fig. 7. The bias on grids 2534 and 265 suñìces to ond intervall This pulse is supplied from ter cut off the pedestal of the voltage from the range minal H1 to Video mixing amplifier |40 and from sweep generator and only a rising voltage appears terminal H1’ when switch S is closed downward to vertical sweep ampliiier 200. 70 across resistor 2H to be transferred through The circuit of video amplifier Mii, of Fig. 1, is stopping condenser 213 and resistor 2M to shown in Fig. 6. It comprises pulse amplifying the junction of resistors 2| 6 and 2H of tube V14, on grid 14H of which is impressed the which the other terminals are connected pulse from terminal H1 of Fig. 5, and video ampli respectively to grids 218 and 2| 9 of tubes V24 fier tube V15 of which grid |42 receives at terminal 75 and V25. these grids being normally biased to 2,406,358 li cut off through resistor 220 by battery 22 l. Tubes V24 and V25 are amplifying tubes in parallel and at their anodes 222 and 223 there appears the amplified sweep voltage which produces a vertical ray deiiecting current in coil VDC of oscilloscope 3. A permanent magnet, not shown, is used to fix the starting point of the vertical sweep, pref erably near the bottom of screen 2. Referring again to video amplifier il@ of Fig. '7 the negative voltage wave arriving at terminal VM is reversed in sign in tube V20 and ultimately appears as an unblanking pulse across resistor H6 in the cathode circuit of tube V19. This pulse is applied to intensity grid i8 of oscilloscope 3 which thus allows the trace on screen 2 to brighten when there arrives a negative pulse at terminal L', Such a pulse, either a radar target echo or one occurring at the instant of equality of range sweep and rate sweep voltages produces a bright spot on screen 2_ 12 Fig. 9B shows the appearance of screen 3 when switches S, S’ and S” are thrown down-wards. Range line RL appears vertically centered and stationary on screen 3 since its creating voltage pip on grid le, although simultaneous with the equality of voltages starting the sweep, is delayed a constant 5 microseconds relative to the moment of such equality. This moment is continually earlier because the voltage at tap E32 on poten tiometer Si determines the date of decrease of> the rate sweep voltage, which accordingly equals the rising range sweep voltage at a continually earlier epoch in the time base interval. If tap t2 is so set that this advance of the moment of equality is proportional to the rate of decrease of the range from plane to target, spot T will con tinue to be intersected by line RL. It will be noted that delay network 256 serves the purpose of Yplacing the intersecting range line and target spot on the screen in a position con venient for observation. Further, it will be re alized that it is much simpler to adjust tap 82 to maintain the coincidence of spot T and line RL than it is by adjustment of tap H39 to follow the Referring to Fig. 8, when switches, S, S’ and S" are thrown downward, tube V23 is rendered conducting and the positive square-topped pulse produced by range diiîerential amplifier H0 pro duces a voltage across cathode resistor 2 ll which 25 moving target spot of Fig. 9A. The operative procedure thus requires that with now is a square-topped wave, positive to ground, switches S, S’ and S” thrown upward, tap |89, beginning at the instant of equality of range and Fig, e, be set to make line RL, Fig. 9A, intersect rate sweep voltages and lasting to the end of the spot T. The ganged switches are thenthrown 100 microseconds time base interval. The cut 01T bias of grids 2W and 2I9 is reduced to zero. 30 downward and tap 82 is adjusted so to control the rate of decrease of the rate sweep voltage, that in The voltage at anodes 222 and 223 abruptly drops Fig. 9B line RL continues tointersect ’spot T. The at the start of this cathode voltage and rises setting of tap 62 thusproduces a voltage to ground proportional to the plane’s velocity relative ‘to in anode voltage of tubes V24 and V25 results in a rise in anode current which ñows in coil HDC, 35 the target considered. This velocity, aspre-V viously stated, is with aA fixed target substan the inductance of which is so chosen that the tially the ground speed of the plane. VThis speed duration of this current is about 11 microseconds. is thus measured by the system of the invention It is thus clear that when switches S, S’ and independently of the conditions of light or S” are closed upward a vertical sweep starts from thereafter exponentially. This exponential rise the bottom of oscilloscope screen 2 and lasts 100 40 weather. ' While Vthe invention has been described with reference to a situation in which the target range appears on screen 2 only when there arrives on is continually decreasing, those skilled in the art grid i8 either a target echo from radar system l are acquainted with means for inverting the de or a pulse from range diiîerential ampliiier l Hi at the instant range and rate sweep voltages are 45 creasing voltage from the rate sweep generator to obtain an increasing voltage. This enables them equal. The azimuth sweep current through coil to maintainV the range line RL intersecting target HDC is controlled from potentiometer 22 of radar spot T as the range increases, thereby adapting system i, so that a target echo brightens the the disclosed system to measure Vspeeds of reces oscilloscope trace at a point corresponding hori microseconds. During this sweep a bright spot zontally to the target bearing, vertically to the target range. On the other hand, the voltage sion as Well as of approach. What is claimed is: ` Y l. The method of measuring the speed of a ves sel relative to an object at a varying range ahead of said vessel, said range being determinable, ness appears as a horizontal line. Fig. 9A represents the appearance of screen 2 55 which comprises the steps of determining said range, defining a repetitive timeinterval, estab under these conditions. T is a target spot hori lishing a ñrst voltage rising substantially linearly Zontally centered while RL is a line formed by with-time during >said repetitive interval, estab the fusion of spots representing equality of range vlishing a second voltage decreasing at a controlla and rate sweep voltages. The vertical position of spot T represents target range, decreasing as 60 ble rate substantially linearly with time over a desired interval longer than said repetitive in the plane iiies onward. Range line RL is made terval, deñning in said repetitive interval an in to intersect spot T at an initial instant by proper stant representative of said range and varying in setting of tap H39 kof Fig. 4. Spot T appears accordance therewith, adjusting said second volt lower and lower as time goes on. While tap m9 age to equality with said iirst voltage at an in may be manually shifted to maintain coincidence stant in said repetitive interval coincident with of RL and T, it is convenient to throw downward said representative instant at an initial definition switch S and switches S' and S” ganged with it. thereof, and controlling the rate of decrease of Now, as previously described, a vertical sweep ll said second voltage to maintain the simultaneity microseconds long starts only at the moment of equality of range and rate voltages and line RL 70 of occurrence of said equality and said represen tative instant, whereby said rate of decrease s appears in a fixed position on the screen, This controlled is proportional to said speed. ' position would be at the bottom were it not for 2. Means for measuring the rate of decrease of delay network 25S which delays the echo pulse the> range from an airplane to a target ahead of and the range line pulse each about 5 micro equality pulseis independent of the rotation of antenna ‘l and the corresponding trace bright seconds. v75 said airplane comprising electrical means for 13 2,406,358 ranging and locating said target including a cath ode ray oscilloscope provided with a fluorescent screen on which the Vertical position of a 1u minous spot moves in accordance With the change in range of said target, electrical means for pro ducing on said screen a luminous horizontal line intersecting said spot in an initial position thereof and electrical means including a potentiometer 14 spot in an initial position thereof and electrical means including a potentiometer graduated in ve locity units for maintaining said spot and said line stationary on said scree . ` 4. Means for measuring the Speed of a vessel relative to and in the direction of an observed target comprising electrical means for ranging and locating said target including a cathode ray graduated in velocity units for moving said line oscilloscope provided with a fluorescent screen to follow said spot. 10 on which the vertical position of a luminous spot 3. Means for measuring the speed of a Vessel represents the range of said target, electrical relative to an object ahead comprising` electrical means for producing a horizontal luminous line means for ranging vand locating said object in on said screen intersecting said spot in an initial cluding a cathode ray oscilloscope provided with position thereof and electrical means including a fluorescent screen on which the vertical position 15 a potentiometer graduated in velocity units for of a luminous spot represents the range of said maintaining said line continuously intersecting object, electrical means for producing a horizon said spot. tal luminous line on said screen intersecting said STEPHEN DOBA, JR.