Sept. i?, 1946. H. EENIOFF 2,407,644 HANGING SYSTEM TIME-__w FIG.| INvENToR BY ffl-’y0 genr'off Sept. E7, 1946. H. SBENIoI-'F 2,407ß44 RANGIN G SYSTEM Filed July 29, 1940 3 Sheets-Sheet 2 /ì RECEPT“ Í l HIGH 1 FREauENcY I AMPLIFIER BEAT | BEÃT pscILLATon l FRìWE'wY Fnsousucv DETECTOR AMPLIFIER szNslTlvITv VARIATION IN Accoœumsca o or I-'|c.| LouosPEAIIER IN l A 0R ,sLAPseo TIM: mmcMoR wI‘rI-l SENSITIVFTY conrnox. FREQUENCY coNTnoL "cI-E TUNING vAmA'rloN IN AcconbANcI: ’ C°NTR°L wI‘rI-I A FIGA NADIA-ron MAsTER OSCILLATOR RF AMPLIFIER> ._I Pm'zqumcv vArIIATIoN IN AcconßANcE WITH A Plek f . \ Fnseusncv connor. Ampuruos con‘rnol. POWER VARIATION lIN ACCORDANCE ` WITH ß FIG.I INVENTOR Sep@ n?, 394s. - _ H, BENIOFF` Y 2,407,644 RANGING SYSTEM ,Filed July 29, 1940 - 3 Sheets-Sheet 3 . Y \ _ v \ y 2|` _* E DRIVEN \I ToGETHER ' .Y là l I4 || " \ ' >lf2 y Fun-:Quemawww@a> m Acconmc-É www A ' -- @owen vAmAneNm AccoœoANçz 0F Fl?" - _ wn'nc or ne.:- - , l Il@ l TRÀNSMITTE I5 | l -|7|fe|el|é`l RECEIVER „mA-"9N m ACGORDAN¢E WITH A ì 0F ‘l F|G_3 Fl'âJ f ; E' i _» FREQUENCY 0F POWER íUPF‘LIEDl TO PROJECTOR. Y' smsrrlvlrv VARIA-519mm AccomnAm-.z WITH D OF FIGJ I ' l l Í `l | s RESONANCE CURVE 0F PROJECTOR OR OUTPUT POWER LEVEL AS A FUNCTION OF TINE. v ì ` ' » INVENTOR » n , Patented Sept. 17, 1946 2,407,644 i'i'ED STATES PATENT OFFICE 2,407,644 RANGING SYSTEM Hugo Benioff, La Canada, Calif., assigner, by mesne assignments, to _Submarine Signal Com pany, Boston, Mass., a corporation of Delaware 1 Application llluly 29, 1940, SerialNo. 348,127 9 Claims. (Cl. 177-352) The present invention relates to a method of acoustic, supersonic and radio ranging which may be used in the ñeld of submarine signaling for the determination of the distance of obstacles and reflecting surfaces as well as for sound rang ing in the air at audible, supersonic and radio frequencies throughout the entire useful radio range. In sound ranging at supersonic frequencies, particularly for submarine signalingr purposes in determining both direction and distance, it is 2 b. From the point by to a point g the frequency remains constant after which the frequency de creases to the starting _point h of the second cycle. The curve A, just described, is made up oi a group of straight-line curves. It should be noted that other types and _forms of curves for curve A may be used and that the curve indi cated in the ñgure might be approximated b_ya single 'harmonic function or a -combination of straight-line and exponential function. In >these, cases it is, of course, necessary to adjust the quite common to use a submarine signaling pro scale of the indicator to correspond. These dif jector from which a Ibeam of oompressional waves ferent types of curves can be controlled either at supersonic frequencies is emitted and the echo mechanically or electrically by control of ca reflected from a distant object picked up by the 15 pacities and resistances in the driving and re same or second similar projector to determine ceiving circuits. It will be noted that the trans both direction and distance. The impulse Vemit mitter or projector in accordance with curve B ted may be at a constant or varying frequency is only radiating between the points o and b and for a time interval of the order'of île of a along the curve 2., since at the point a, as shown second. in this method of sound ranging it has 20. in curve C, the power comes on substantially been found that the nearby reflecting surfaces instantaneously and remains on to the point b. such as the bottom, the sides o the vessel and This radiated power, as indicated by the section the water surface, which return the reflected 3 of the curve C, decreases from an initial maxi signal, produce reverberatlons which last for a mum to z_ero approximately exponentially or ac considerable interval after the projector has 25 cording to some other chosen law. The purpose ceased emitting its sound beam. These reverber of this decrease will be more fully explained later. sufficient intensity to interfere with the proper The control of the receiver is also indicated reception of echoes returning from more distant in the curves of Fig, 1. In accordance with curve objects. This is true even where the compres 30 B the tuning of the receiver varies from the point sional waves are confined in a beam _as a result c in accordance with the dotted-line section ¿l of which the possible reiiecting surface is reduced. of curve B. This variation in frequency of the ations persist for a _long period of time with In the present invention the system is so ar receiver starts with a frequency F2 and Varies to F1 along a similar curve as the transmitter, which ranged that these reverberations do not disturb the operation of the system. This is accom starts at F1 and varies to F2. Similarly, the receiver sensitivity which is indicated in curve D shows .irl the portion 5 of the curve between the points c and d that the sensitivity of the plished principally by cyclic control of both fre.V quency and intensity of the radiated signal as Well as the tuning and sensitivity Of the receiving apparatus. . receive;` increases in its cycley from a minimum The system will be more completely described 4.0 to a maximum in the reverse of section 3 of the in connection with the drawings in which Fig. power radiated. 1 shows a group of curves illustrating the cons trol and cyclic operation of the transmitting and receiving systems; Fig. 2 shows in block diagram a transmitting and receiving system for radio and supersonic ranging; Fig. 3 illustrates a system adaptable „for acoustic or supersonic ranging in accordance with the invention; and Fig. 4 shows a pair of curves of projector resonance and fre quency variation which may be used in, a modi fication of the present invention. In Fig. 1 curve A shows the control of the master oscillator frequency plotted against a time axis. _At the point a in the time axis the ' From what has been described above, it will be seen that between the points b and c no power _is radiated and no signal is received. This deter mines tlîle minimum time-interval measurement and distance of the operation of the apparatus, since lthe shortest time interval between the 0p eration of, the transmitter and the operation of the receiver is deiined by the distance bc on curve 50 A .so that the minimum signal. renee is equal to 45 , U [26.5 Here, bc is equal to the Shortest time interval frequency increases along the curve I to the point 55 between the operation of the transmitter and thiD 2,407,644 3 earliest instant that the receiver becomes opera tive, while 'D is equal to the velocity of the signal wave. The frequency received at the minimum distance will be the high frequency at b and 4 trolled either by means of some standard fre quency oscillator or through a standard and con stant driving system, as, for instance, where the condensers for varying lthe frequency are of the rotor type and driven synchronously or on a common shaft. since this signal energy travels only a short dis tance before reflection, the power radiated at this The receiving system is made up of a receptor point in the cycle is made small and the .sensi which may be a radio receiving antenna or in a sound sysœm a sound receiver of the sonic or tivity of the receiver is correspondingly `keptrlat a low value. For signals returning at a greater supersonic type. The signal received by the re distance the power output is increased and the ceiver is impressed upon an amplifier which may receiver sensitivity is raised as indicated by the operate in the high frequency range where the curves C and D, sections 3 and 5, respectively. signal is in that range or in any other range Further selectivity and freedom from interference corresponding to the range of variations of the are obtained by simultaneously varying the fre» signals to be received. Corresponding to the am quency of the transmitter and receiver to cor plitude control of the transmitter is a sensitivity respond so that the receiver is progressively in control of the receiving amplifier which may be condition to receive signals as they arrive from by control of a grid bias or by any of the other given distances without being sensitive tothe systems and methods commonly used. The am arrival of signals from other distances, that is pliñer is also cyclically controlled through a fre to say. when the receiver is adjusted to the fre 20 quency control shown in the diagram which may quency at œ, the receiver will be in condition to be of the usual frequency modulation receivers receive the same frequency radiated at œ' and adaptable for .the desired range of reception. the distance will be established by the interval With the use of very high frequencies the fre between :1: and œ'. At the point y on the curve “ quency may be controlled through the variation of the receiving frequency the only distance of tuning of the tube of the “klystron” type. measurable will be yy' so that for each point on the curve, the frequency at which 'the receiver In the receiving system there is also shown a detector and a beat frequency oscillator ampli will respond, correspondsto a single measurable , fier. The beat frequency oscillator amplifier per mits the use of a beat frequency range indicator 30 E in Fig. 1 where the elapsed time of travel of the distance. This is illustrated more clearly in curve in the present invention, the range being indi cated by the corresponding frequency established through the beating of the beat frequency oscil-lator andthe received signal. In addition to the received signal is plotted against the time axis. Curve rF in Fig. 1 shows the beat _frequency obtained by the beating of a constant master oscillator at a frequency as indicated in curve A, Fig. 1, with the received signal. This curve may be made to increase or decrease with range, de 35 distance and elapsed time being determined in this Way, an elapsed time indicator may also be provided, the indicator in this case being driven pending upon what frequency is chosen for .the through the cycle control and being operated by master oscillator. As the receiver tuning drops the signal received by the receiver. The elapsed from that of the master oscillator, the beat fre quency increases corresponding to the elapsed 40 time indicator may be a rotating disc carrying a neon light which is illuminated when the signal time and gives a definite frequency vas .a measure is received. of the time and distance. A system adaptable for acoustic and supersonic The system may be operated by the arrange ‘systems is indicated diagrammatically in Fig. 3. ment shown in Fig. 2 in which the elements are given their proper legends. The signal radiated from the radiator, which may be an antenna or a submarine signaling radiator or projectory is Here the transmitter I0 sends out a signal in ac« cordance with curves A and B of Fig. 1, the tun ing or frequency of .the signal being controlled by the variable rotating condensers I I and I2 and the power radiated being controlled by variable excitation in the input grid circuit of the oscil oscillator is controlled in accordance with curve 50 lator I3 by means of the rotating potentiometer A of Fig. 1 by the frequency-control element arm I4. In the receiving system the receiver I5 which may be a condenser Whose capacity is impresses the signal received into the receiving altered by a sinusoidal vibration of one of its circuit I6 which goes through a cyclic tuning plates or by any other suitable method, as, for stage effected by the rota-tion of the condensers instance, cam control or capacity variation with I'I and I8 for tuning the receiving circuit. The the use of a condenser having a rotor and a stator sensitivity of the receiving system is controlled element or the frequency may be controlledby by means of the rotating potentiometer arm I9 any one of the methods used in frequency modu which varies the bias on the grid 2i! of the receiv lation for long and short waves, as, for instance, in the manner shown in the pa-tent to Hansell, 60 ing tube. The signal received is made to operate the neon indicator 2I mounted on‘the rotating No. 1,830,166, issued November 3, 1931.V A “klys disc 22. In the system above described the rotat tron” type tube may be used for this purpose in ing disc 22 and all of the other rotating elements, which the resonant element may be mechanical such as II, I2, I4, I1, I8 and I9, are rotated either ly, magnetically, electrically or magnetostrictively on the same shaft or at the same speeds by means operated. The frequency may also be controlled of synchronous motors or positive driving con by the use of a piezoelectric crystal. The am nections. In these cases the various elements plitude of the radiated signal, which is controlled are phased to produce the cyclic operation de in accordance with section 3 of curve C, is con scribed in connection with Fig. 1. trolled by means of the amplitude control con A different method of obtaining the radiating nected to the amplifier. Various methods of am 70 power output curve may be employed by using plitude control may be used, as, for instance, the Ithe resonance curve of the projector or sound control of variation of excitation or by variation supplied with power through the master oscil lator and amplifier. The frequency of the master of grid and plate potentials. The complete cycle control is indicated by the legend “Cycle control” and may be electrically or mechanically con transmitter. A resonance curve of this type is shown in curve B of Fig. 4 where the power am plitude is plotted as an ordinate against fre 2,407, 644 5 quency as the abscissa. It will be noted that the projector need not have a dat characteristic overV the frequency range and that as a matter of- fact 6 formity to a determinable curve, means for pro-_ gressively decreasing the signal amplitude from a maximum to zero contemporaneously with the frequency modulation and means for adjusting jector is advantageously used. By varying the CII the tuning and sensitivity of the receiving means frequency between the peak f1 of Fig. 4 and the to follow substantially the same determinable point f2 in accordance with section 2 of curve curve but in reverse direction to that of the signal B of Fig. 1 the power output will decrease as sent out with regard respectively to frequency indicated by the section Sii of curve B of Fig. 4 and amplitude. similar to that of section 3 in curve C in Fig, l. 10 4l. A standby system for obstacle detection and This system may particularly be employed with a distance measurement comprising means for submarine signaling projector. For this purpose sending out a signal modulated linearly with in any fairly sharp transmitter may be used as. for creasing frequency during at least a portion of instance, a so-called Fessenden oscillator, or a a repeated cycle in conformity to a determinable tuned diaphragm device magnetically or dynami 15 curve. means for progressively decreasing the sig. cally operated or any of the Well-known devices nal amplitude from a maximum to Zero during of which there are many. As references the said same portion of the repeated cycle and applicant refers to the Fessenden Patent No. means for adjusting the tuning and sensitivity 1,167,366, issued January 4, 1916, and the Hecht of the receiving means to follow substantially the in the present case the resonance of the pro et a1. Patent No. 1,604,693, issued October 26, 20 same determinable curve but in reverse direction 1926. to that of the signal sent out with regard respec This provides a distinct advantage over the tively to frequency and amplitude. visual indicating system in that it need not be 5. A standby system for obstacle detection and watched continually to indicate Whether an ob distance measurement comprising means for ject is within range and, further, the pitch of 25 sending out a signal modulated linearly with re the audible signal will thus be an indication of spect to frequency during at least a portion of the distance of th-e object. a repeated signal cycle in conformity to a deter In the system which has just been described minable curve, means for progressively decreasing it should be noted that .the reverberations of the signal amplitude from a maximum to zero the high-'powered signal initially sent out will not 30 during said same portion of the repeated cycle affect the receiver when it is put in condition to and thereafter maintaining a zero amplitude un receive the signal, for not only is the tuning of til the said same portion of the cycle is repeated the receiver such .that the receiver is unable to and means for adjusting the tuning and sensi handle this signal, but also it is some time later tivity of the receiving means to follow substan before the receiver is in proper condition to be operated. tially the same determinable curve but in reverse direction to that of the signal sent out with regard The minimum measuring distance, as has been respectively to frequency and amplitude. stated. is determined by the time interval repre 6. A standby system for obstacle detection and sented by the points b and c. The maximum distance measurement comprising means for time interval is determined by the time interval 40 sending out a signal modulated in frequency pro represented between points a and d. By using a gressively in repeated cycles in conformity to a compartively slow modulation of frequency and determinable curve, means for progressively de intensity the system may be made to cover a creasing the signal amplitude from a maximum range from the minimum to the maximum to to a zero value down a portion of said cycle and which the energy will travel and be reflected. maintaining the amplitude at substantially zero Having now described my invention, I claim: until said portion of the cycle is repeated, means l. A standby system for obstacle detection and for receiving the signal sent out after reflection distance .easurement comprising means for from an obstacle or distant reflecting signal and sending out a signal modulated in frequency and means for varying the timing and sensitivity of amplitude progressively in repeated cycles in con 50 the receiving means to follow substantially the formity to a determinable curve. means for re same determinable curve but in reverse direction to that of the signal sent out with regard respec an obstacle or distant reflecting surface and tively to frequency and amplitude and means means for adjusting the tuning and sensitivity providing a constant frequency for producing a of the receiving means to follow substantially the beat note with the signal received, said beat note same determinable curve but in reverse direction being adapted to establish the distance to be to that of the signal sent out with regard respec measured. tively to frequency and amplitude. '7. A standby system for obstacle detection and 2. A standby system for obstacle detection and distance measurement comprising means for distance measurement comprising means for 60 sending out a signal modulated in frequency pro sending out a signal modulated in frequency pro gressively in repeated cycles in conformity to a gressively in repeated cycles in conformity to a determinable curve, means for progressively de determina-ble curve, means for progressively de creasing the signal amplitude from a maximum to creasing the signal amplitude from a maximum a zero value down a portion of said cycle and ceiving the signal sent out after reflection from to zero contemporaneously with the frequency modulation and means for adjusting the tuning and sensitivity of the receiving means to follow substantially the same determinable curve but in reverse direction to that of the signal sent out with regard respectively to frequency and am 70 maintaining the amplitude at substantially zero until said portion of the cycle is repeated, means for receiving the signal sent out after reflection -from an obstacle or distant reflecting signal and means for varying the tuning and sensitivity of the receiving means to follow substantially the 3. A standby system for obstacle detection and distance measurement comprising means for sending out a signal modulated linearly in fre to that of the signal sent out with regard respec plitude, same determinable curve but in reverse direction tively to frequency and amplitude and time measuring means synchronously operated with quency in a portion of a repeated cycle in con 75 said cycle for indicating the elapsed time between 2,407,644 the transmission of a portion of the signal cycle and the receipt of its reflected echo. 8. A method of obstacle and distance measure ment which comprises transmitting a signal vary 8 9. A method for obstacle detection and distance measurement comprising sending out periodically signals linearly modulated in frequency and de creasing in amplitude from an initia1 maximum ing both in frequency and amplitude according to a determinable curve, receiving the signal after value to zero according to a determinable curve, refiection from the obstacle or distant reflecting creasing the sensitivity of reception and varying surface, varying during the receiving period tun ing and sensitivity of the receiving system ac receiving said signals sent out at a time interval later than the end of the transmitted signal, in the tuning thereof linearly according to said curve but in reverse progression from that employed in cording to said determinable curve but in reverse 10 the transmission of the signal whereby the listen direction corresponding to a time schedule for ing area is progressively swept away from the the return of reflected signals from the nearest listening point, and indicating by the frequency to the most distant object in the range to be ob of the received signal the distance being meas served whereby the receipt of the signal and its corresponding frequency identity determines the 15 ured. HUGO BENIOFF. distance of the object.