Патент USA US2403622код для вставки
Patented July 9, 1946 x 2,403,622 UNITED STATES. PATENT OFFICE 2,403,622 OBSTACLE DETECTING SYSTEM Clarence D. Tuska,l Philadelphia, Pa., assignor to Radio Corporation of Americma corporation of Delaware Application July"3`0,'1938, Serial No. 222,088l 4 Claims. (Cl. 250-11) 2 This invention relates to obstacle» detection and fluency. oscillations ofthe above mentioned :Ere-- more specifically to a system in which pulses of radio frequency energy'- are di-rectively radiated’ quency in any practical installation on an air to be reflected by an object to be detected. Obstacle detecting systems using radio fre quency energy have been proposed. In one» sys tem, a pulse of radio frequency energy» is radiatedy toward an object and simultaneously with the ra ,obtain the required directivity for obstacle detec tion byvutiüzing pulses of radio frequencyenergy diation a cathode ray is deñected along one path. of suchy construction as are practical on airplanes. After the pulse of radio frequency energy has been reflected by an obstacle, it is applied toV a‘receiver which is connected to deflecting electrodes ofthe It is afurther object of this invention to provide means» whereby radio frequency fields navi-ngen' overlappingportion of the required directivity for craft. It is an object of this invention, therefore, to having a frequencyl of 'ther orderV of 500 mega cycles’per second and utilizing directive antennas cathode ray- tube so. that the. raymay be deñected> obstacleV »detection areestabl-ishedf. Itis a stillv at. an angle to its first mentioned path. If the cath further object toA provide means for directively* ode ray traverses the ñrst mentioned path at a 15 and simultaneously radiating pulses of rad-io fre-Y uniform rate dependent upon the range of the quency energy of,v4 different frequency indifferent obstacle detector and startingV in. synchronism directionsV whereby the simultaneous reception` of with. each outgoing pulse, the- received reflected these Waves operates a receiver responsive> to the signals willV caues the second mentioned deñec difference in frequency» of the pulses. A still fur tions at points proportionalto the distance froml 20 ther obj ect of the invention is to providev` means for distinguishing indications obtained by reflections from obstacles locatedv on the desired coursefrom objects to the-left lorrig-ht ofthe course. portional to the time required for the radio Wavel The invention will» bev described by referenceitot to travel to the object and back to- thereceiver 25 the accompanying drawing in lwhich and such indications are independent of direc Figure 1 isa schematic illustration of one e tion. With such systems, the observer is unable bodiment ofthe invention, and ‘ , Figures 2 and 3 are-graphicillustrations used to distinguish between> indications resulting from in describing the invention. reñected Waves arriving at different. angles.. For Referring to Fig. 1, a keyer l is connected to example, if one reflection is caused by an object a pair of pulse generatorsv 3, 5. The pulse gen due north of the observer a distance of 1500 me eratorsl have output frequencies f1 and f2, respec ters„ an exactly similar irniication> will result tively. AThe` output currents from the generators from an object 1500 meters northeast of the ob are applied respectively to the `antennas l, 9 server. One obvious correction of this` difficulty ~' which maybe dipoles or the like. The antennas is to make the radiated Waves as directiveas pos sible. If the obstacle detector is to be used in a preferably include-reflectors H, i3, " The reflectors ñxed position Where suflicient space: is available, are of such-size and arrangement-as Will substan it is possible to erect an antenna. array whichv will tially prevent radiation in one direction'and Will provide the required degree of directivity. concentrate the radiation in the opposite> direc, If the obstacle detecting system is to be> used tion as Will hereinafter be described.r The keyer the transmitter to the reflected object. ì One of the difficulties» with systems. of this type» is that the indication of the reflections is pro-y on a relatively small vehicle suc-h as an airplane, it becomes very difficult to erect an antenna sys is also connected through a suitable networkl lâ which provides a deflecting voltage for one pair tem which will have the required directivity and will not at the same time put unreasonable drag of deiiecting electrodes of 'a cathode ray tube Il. The Vkeyer may also be connected either directly on the craft. Perhaps an obvious solution oi the antenna array for aircrafty would be the utiliza or through the network l5»to a receiver I9. The input of the receiver i9 is connected to a receiv ing antenna 2l which may'include a reñector 23. tion of extremely high frequencies which would permit the use of a reflector for focusing or beam ing the Waves. While this solution is practical from the standpoint of the, antenna. itv requiresv the generation of Waves having a frequency of the order of 3,000,000,000 cycles per second: While currents of such frequencies are generated in the laboratory, it does not. seem entirely prac.-l ticaI toy generate, amplify and detect radio fre In sornel installations either or both ofthe trans~ mitting antennas 1, 9 may be used as there ceiving antenna. The output of the receiver is connected to a second pair ofV defiecting elec trodes; of the cathode ray tube I1; l . - , The principle of operation is as follows: The keyer l generates pulses: which are sharply de 55 fined and of an interval of the lorder of a fraction 2,403,622 4 3 of a micro-second. quency energy f1, fz having field patterns 39, 4I, These pulses are simulta respectively, are simultaneously radiated from the aircraft 31. It will be seen that these field patterns have a common or overlapping portion 43 which sharply defines the path of the craft as represented by the dash lines 45. In the event that there are reflecting objects as indicated by neously applied to the pulse generators of fre quency f1 and f2 whereby the generators are keyed on for a brief interval. The “on interval” is fol lowed by an “off interval” which is long enough to permit the outgoing waves to travel to a distant object and return before the next pulse of radio frequency energy is radiated. The two transmit the reference numerals 41, 49, 5I, it follows that reflections from 41 will only contain energy of II, I3 are arranged to direct the radiation so 10 frequency „f1 while reñections from the object represented by reference numeral 5I will only that the major axes of the field patterns are contain energy of frequency f2. Since these ob directed toward the obstacles to be detected along jects are located at different distances from the the course of the moving craft carrying the appa ting antennas 1, 9, together with their reflectors ratus. , The transmitted pulses of radio frequency en plane, the reflected energy will not arrive simul 15 taneously and will not cause any undesired indication. If, however, an obstacle represented by reference numeral 49 lies in the overlapping portion of the fields, the reflected pulses f1 and f2 will reach the receiver simultaneously and will, ergy f1 and f2 are radiated toward a distant 0b ject to be reñected from the object back to the receiving antenna 2| which may be made direc tive along the desired course. The received waves induce currents in the directive antenna 2| which 20 therefore, cause an indication. While the sys tem of the invention thus appears to limit -itself are applied to any suitable means for combining to obstacles directly on the course of the plane, the two currents to derive a current of a fre it will appear that two objects located at equal quency equal to the difference in frequency of distances, although not on the desired course, the transmitted pulses. For example, if the transmitted pulses have a frequency f1 and f2, 25 may cause reiiections to be simultaneously re ceived and indicated. Such a situation is prob respectively, the pulses, after reiiection, will be ably unlikely and would be transitory instead of combined in the receiver to generate currents of giving a continuous indication. frequency f1-fz. These currents fi-fz may be Thus. it appears that the present system simul amplified and demodulated. The demodulated currents are impressed on the second pair of de 30 taneously radiates impulses of two different radio frequencies along slight different paths having a ' flecting electrodes of the cathode ray tube I1. common field portion. The transmittedY pulses Since the receiver is only responsive to currents are refiected and if the reflections of the two fre of the diiference frequency fi-fz, it follows that the receiver will only respond when the two duencies arrive simultaneously at the receiver. transmitted pulses, after reflection, simultane 35 they are combined to produce an indication. AIn ously arrive at the receiver. In the event that the event that the pulses arrive at different times, , one impulse- for example f1, arrives before the they are not combined and no indication is ob second impulse f2, there will be no current of dif ference frequency f1-f2 produced and therefore no signal will appear in the output of the re ceiver. It should be understood that the receiving an tenna may be suitably shielded to prevent direct pickup from the transmitting antennas. In the event that the shielding is insufficient and to prevent any residual currents from blocking the receiver, it is preferable to apply an initial bias ing impulse, which may be derived directly or indirectly from the keyer I, to make the receiver inoperative for the brief instant at which the radiation takes place from the transmitter. It should also be understood that the receiver may tained. In general~ the simultaneous reflection 40 will only occur in the common portion of the overlapping iields. No attempt has been made to describe the kever, pulse generators, cathode ray tube or deiiecting voltage. network. as these> elements are well known to those skilled in the, art. I claim as my invention: „ . . _ 1. In an obstacle detector system, the combina tion oi' a keyer, a pair of pulse generators' of radio energy of different frequency, means con necting said keyer and said generators whereby said generators are simultaneously keyed, means4 for directively radiating said keyed pulses of radio energy, said radiation having diñerent field pat, utilize a conventional radio frequency detector terns and a portion thereof overlapping, and and audio frequency circuits. means for receiving said pulses after reflection, In Fig. 2 is illustrated an aircraft 25 from 55 from said obstacle, said receiving means being which pulses of radio frequency energy having a responsive to currents of the difference fre field pattern 21 are radiated. The course of the quency of said ñrst mentioned frequencies and4 plane, with a factor of safety on either side being unresponsive unless said currents of both frequencies are simultaneously applied.thereof. is indicated by the dash lines 29. In the event that objects are present at points 3i, 33 60 2. In a system of the character of claim 1 a and 35, it Will be seen that the system would be cathode ray tube including ray deflecting means, responsive to reflections from all three objects. means for deñecting said ray in synchronism These reflections on the conventional system with said keying, and vmeans for indicating onA would all appear as obstacles to be avoided by said cathode ray tube the simultaneous reception the operator of the aircraft. However, it follows, 65 of said signals. from inspection, that the objects represented by 3. 'I'he method of detecting objects by means the reference numerals 3i and 35 are suiiiciently of pulses of radio energy which includes radiat oiï the course as to represent no obstacle in ing pulses of radio frequency energy in different the path of the airplane. With respect to the ob directions, each of said pulses comprising atrain ject indicated by the reference numeral 33, this 70 of radio frequency waves, adjusting directivity of would represent an obstacle to be avoided. said radiations to establish a common field, de-While the foregoing system has the charac riving currents from the reflection of said pulses, » teristics shown in Fig. 2, the system with this combining said currents upon simultaneous re-. invention has the characteristics represented by ception, demodulating said combined currents, Fig. 3. In this illustration pulses of radio fre 75 and indicating the presence of a pulse reflecting 5 object in said common field as a function of said demodulated currents. 4. The method of detecting objects by means of pulses of radio energy which includes, gen quency when said simultaneous pulses are si multaneously received, deriving from said com bined currents a current whereof the frequency , erating radio currents of different frequencies, simultaneously and directively radiating said pulses whereby the patterns of said radiations is equal to the difference between the frquencies of the combind currents, demodulating said dif ferent frequency current, and indicating the presence of a pulse reflecting object in said com-y have a common portion, receiving said radiated mon portion as a function of said demodulated pulses after reflection from an object, deriving currents. currents of diiîerent frequency from said recep 10 tion, combining said currents of diiîerent fre CLARENCE D. TUSKA.