BE467784A - - Google Patents

Description

       

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  REQUIREMENTS TO; RADIO-BEACON SYSTEMS.



   The present invention relates to improvements to radio beacon systems and, in particular, to those of the flagship type, suitable for the reproduction of a formation of approaching aircraft; and in the vicinity of the beacon.



   Radio beacon or position indicator systems in which the reproduction of a formation of aircraft for reflecting energy can be obtained on a remotely located receiver, such as used on a moving aircraft have already been proposed. To obtain the indications relating to the formation, it is necessary to solve a series of triangles relating to the various positions of the reflective objects so as to suitably dimension the parameters of the formation. In such systems, in order to obtain the indication of the position of the receiver on which the reproduction takes place, relative to the transmitter, or radio beacon, it has generally been necessary to use the radio- lighthouse, a directed broadcast and, on the aircraft, a directed reception.

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  At the very least, two sources of radiation should be provided at the beacon, with suitable spacing. These little radiators. wind be either very directed or non-directional. When a directed beacon is provided in combination with a reflecting source, or other source of radiation, directivity is no longer required on the aircraft or at the remote receiver. If one has planned. radio beacon transmitters spaced apart from each other, it is necessary to employ a directive reception on the aircraft, or other indicating receiver, so as to obtain the proper angular relation in the reproduction of the image. training, and to use triangulation for distance determination.



   According to the invention, there is provided a radio headlight fitting system by means of which a reproduction of reflective objects, with their relative positions, can be produced in a receiver located at a distance from the headlight, below the headlight. effect of the energy of a single headlamp emitting gear having a directive radiation characteristic and without using directive reception at the receiver.



   In accordance with one of the characteristics of the invention, provision is made for what may be called a three-way radar apparatus, to produce on the airplane or other remote indicating receiver, the reproduction of the position of the indicating receiver. -even with respect to the radio-beacon and the relative positions of other reflecting objects, provided with suitable receivers. To obtain this reproduction, the energy of the radio beacon is transmitted in a directed manner, in different directions, successively. This energy is received by each of the active repeater stations, including at least. one is fitted with reproduction equipment. At the repeating and reproducing station, a pulse of different characteristics, for example of different wavelength, can be obtained.



  Simultaneously with the repetition of this pulse, control of a position indicator scan circuit is obtained. This repeated impulse and the analogous repeated impulses from the

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 other active repeaters is used to activate an additional repeater at the beacon station. The pulses repeated by the headlight are then transmitted, preferably without directivity, with particular identification characteristics. The repeated pulses corresponding to those of the reproducing station serve, when received at said station, to determine the distance and the position of this station with respect to the radio beacon.

   The angle and distance parameters thus determined serve to establish the basic parameters for the scanning of the indicator, as the repeated pulses from the radio beacon in response to all pulses from the active repeaters produce. indications of the relative position of said active repeaters. It can thus be seen that a reproduction of all the active reflecting objects is obtained at the reproduction receiver. Preferably, the triggering pulses of the headlight are transmitted over a beam with pronounced directivity, so that the only repeaters which are in alignment with said beam are actuated with a view to transmitting reproduced pulses to the beam. reproduction station.

   The reproducing station also scans the indicator surface in time relation to the directional movement of the high beam of the headlight. In this way, the reproduction of the reflecting elements occurs in different angular positions, depending on the position of said elements with respect to the radio beacon.



  This reproduction practically corresponds to an azimuthal radr reproduction of the type which would be produced directly at the beacon radio station. In fact, such reproduction can also be pro. picked up at the lighthouse station, in response to repeated impulses from reflective objects located at a distance. However, the replica can be produced at each repeater location, provided the necessary indicating equipment is available there.



   In accordance with the characteristics of the invention outlined above, the object of said invention is the constitution of a remote measurement indication system on a remote receiver, in

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 response to signal energy transmitted from a transmitter.



   The invention also relates to a radio-electric position indicator and a system for producing the radio-electric reproduction of a number of reflective objects, in response to energy emitted by a single remote transmitter.



   The invention also contemplates the production of multiple indications at a receiving point, the radiating effect of which is not directed, in response to the energy emitted by a single radio beacon apparatus.



   Having determined the distance between the position receiving equipment and the radio beacon, by means of the three-way radar equipment, it is also possible to produce a reproduction of the radio beacon on the indicating equipment, by means of the direct beacon. - tional and various reflective objects, active and passive, located in its field. For this purpose, reflected energy can be received at the indicating station which is not dependent on specially repeated signals. The triangle defined by the reproduction indicator of the radio beacon and other reflective objects can be resolved by the cooperation of the directed transmission beam and the known distance between the position indicator at reception and the radio beacon. , determined by the radar equipment.

   The position indicator may then be caused to deviate commensurately from the resulting determined position indication based on the spacing and directionality of the transmitter. Accordingly, at the position indicator, a duplicate indication may be produced, substantially similar to that described above. However, in this case passive reflectors will be indicated as well as active receivers. In this type of indication, however, the position of objects within an area defined by an ellipse containing the radio beacon and the position indicator itself is not susceptible to definition. suitable.

   Circuits for alternately applying the two indicating voltage pulses to the indicating device can be provided at the position indicator.

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  If there is any error from the steering gear or the distance indications, the two diagrams will not match. The greatest possibility of error occurs in the distance measuring system, since it is possible that the range indicating range of the three-way radar is based on repeated pulses by an apparatus other than that of the station in question. However, as this would result in a distortion of the two diagrams, one can easily make a coincidence adjustment of the two diagrams to correct this error.

   The fact that there is an error in the indications of the radio beacon can easily be checked by comparing the position of known fixed objects on a map with the indications of said objects produced on the general position indicator itself.



   In order to produce alternately the indication of the three-way radar and that of the radio beacon, means are provided at the transmitter or at the radio beacon for the cyclic switching necessary for the transmission of the various control signals. Likewise, suitable switching and blocking controls are provided at the receiving equipment of the reproducing station to distribute the various signals received on suitable circuits for the production of the various reproductions.



   In accordance with these additional characteristics of the invention, another object of the latter is the constitution of a system intended to produce the reproduction of several reflective objects, in accordance with the principle of the radio-beacon, without it being necessary to provide directivity both at the transmitter and at the receiver, or to provide several known reference radiators.



   The invention also envisages the constitution of a position indicator receiver intended to produce alternately position indications of the radio beacon and the indications of a three-way radar.



   The invention also provides for transmitting and

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 receiver capable of providing a virtually error-free indication of the position of a number of reflecting objects at the location of one of said reflecting objects.



   The main characteristics and objects of the invention having been outlined above, the invention will be better understood with the aid of the following description of one of its embodiments, and by examining the accompanying drawings in which the said embodiment is shown schematically, by way of non-limiting example.



   Figures 1.A, 1.B, 1.C are the schematic representation of a radio beacon system and a diagram / cycle of operation as a function of. time, according to the invention, with indication of several transmission positions and the various operating cycles.



   FIG. 2 is a schematic representation of the relative position of a radio beacon in accordance with the invention and of a repeater set of indications, thus street of several reflected objects - jumps.



   FIG. 3 schematically represents, with the aid of rectangles, a radio beacon transmitter system according to the invention.



   FIG. 4 conventionally represents in the same way an indication receiver according to the invention,
FIG. 5 is an illustrative diagram of the follower circuit shown retort forming part of the diagram of FIG. 4.



   Figure 6 is a set of curves used to explain the operation of the diagram of Figure 5.



   FIG. 7 is the diagram of a scanning circuit according to the cube law, usable with the system of FIG. 4.



   Figure 8 is a schematic of a pulse width selector which can be used in the arrangements of Figures 3 and 4.



   Figure 9 is a graphical representation for explaining the operation of the system of Figure 8.

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   Figures 10 and 11 are illustrative diagrams of the figures obtained on the oscilloscope by the indicator circuits of the radio beacon and the three-way radar, respectively.



   There is shown in Figure 1 (1.A. 1.B, 1.0) a diagram as a function of time, of the operations of a complete system according to the invention, representing the operation of the beacon and reproduction receiver, by sub-periods, for some of the sixty-seven time positions: 1, 2, 61, 62,66, 67, of a rotating beacon, the other periods between 1 and 67, and additional periods of operation having been omitted. The odd time sequence indications 1, 61 and 67 illustrate part of the operating sub-period relating to the transmission of the radio beacon indication, while the even diagrams, 2.62 and 66 illustrate the operating sub-periods corresponding to the indication of the three-way radar.



   For the operation of the radio beacon indication, the radio beacon 68 emits a beam of strongly directional energy, as shown at 69, and simultaneously emits, in all directions, another series of pulses 70, preferably at a radio frequency different from that emitted at 69. The emission 70 is intended to transmit synchronization pulses causing the start of the indicator scanning circuit, which may be located, for example, on an airplane shown in 71. A mountain forming an obstacle, for example, is shown at 72, and another smaller elevation, at 73. A number of other planes 74,75, 76,77,78, 79 are shown in the vicinity of the radio. headlight.



   For the indication of the three-way radai *, the directional beam 69 is modulated by means of a particular selective or interrogation signal such as, for example, that pulses of a certain width, different from the pulses transmitted for. the radio beacon indication. At the same time, cmni-directional radiations at different wavelengths may carry a special signaling modulation, as indicated by lines 80, for the purpose.

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 to indicate that beam 69 passes through true north. This indication will only be reproduced at a small angle. for example of a degree, during which the beam, is in this direction.

   For the remaining cycles of the three-way radar indication transmission, further signals 81, as shown in columns 62 and 66 of the timing diagram, will be transmitted, for the purpose of starting the scan circuit. three-way radar indication.



   In explaining the operating principles of systole it will be more convenient to consider separately the operating principles of the two functions performed more or less separately, that is to say those relating to the three-way radar (3P.R. ) and those relating to the radio beacon (RLS).



   The theory of operation can be best explained by referring to the time diagram of FIG. I.B; as this timing diagram relates to the combined operation of the complete system, comprising both the RLS. and 3.PR functions, which are performed alternately in very rapid successions, it is necessary in the present discussion to neglect odd numbered columns. The figures and the timing diagram shown in column 62 of Figure I.B can be taken as best representing the principles of operation which will now be discussed.



   The upper figure of said column 62 shows the radio beacon 68 emitting a characteristic signal, such as a pulse of width W1, radiated in a narrow beam 69 at a given frequency, for example, at a micrometric wave frequency. time, said radio beacon undirectedly emits pulses 81 of a different and preferably lower frequency for synchronization. Note that the narrow beam of micrometric radiation crosses the plane of the observer himself 71 and two other planes 74 and 75 (whose route is exactly 15 to the East of the direction of North) and finally comes to hit mountain 72.

   But this beam narrowly avoids the contact of a

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 -fourth plane 76, slightly out of alignment with the others.



   The timing diagram at the bottom of column 62 only represents signals produced along an arbitrarily chosen radius, and directed from the lighthouse at an angle of 15 to the east. With respect to this narrow region of space, the time diagram represents all the signals known to occur up to a radial distance of 30 km. On this time diagram, the vertical coordinates represent the radial distance along the chosen 15 azimuth and horizontal coordinates correspond to time in microseconds.



   In this way, the lower frequency sync pulses 81, moving away from the radio beacon at the speed of light are shown as an oblique dashed line on the timing diagram. It is assumed that this impulse is radiated a certain time after the beginning of the complete cycle of rotation and that it corresponds to 0 km. The maximum range of the apparatus and the speed of rotation determine the length of the ray. At progressively later instants, this pulse is represented at progressively greater radial distances, thus forming an oblique line which, finally, reaches a distance of 50 km. Approximately 270 microseconds later.

   Since the micrometer wave beam shown in the column figure 62 is at azimuth 15 shown on the timing diagram, the corresponding emitted micrometer wave pulse 83 is also shown as a dashed line. full thick, starting at distance 0 at time 50.833 microseconds and propagating outward in the same way as the low frequency sync pulse just discussed.



   If we now refer to the second image of the colon. ne'62, pn will see that each of the three airplanes 71, 74 and 75 which have been struck by the micrometer wave beam react by reflecting a pulse of different and lower frequency 84 in all directions. The fixture 72 is shown as purely and simply reflecting the same energy at 85, but

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 this reflection has no meaning at this moment because the 3.PR indication is not organized in such a way as to include passive reflections.



   On the time diagram, we see that at the three instants at which the energy of micrometric waves propagates towards the outside passes to the radial distances occupied by the three planes 71, 74 and 75, which we suppose to be situated at 9, 20 and 35 km respectively, three lower frequency reflections originate at the corresponding distances, and begin to return to lighthouse 68 with a slope still corresponding to the propagation speed, as shown in 86, 87 and 88.



   One can also imagine the radio beacon 68 as once again emitting a train of micrometric wave pulses 89, supposedly triggered by the arrival of the three lower frequency responses of the three planes. However, these pulses are not beamed, but sent in all directions and hence produce much lower signal intensities than the original beam radiation. The pulses are also differentiated by various characteristics, such as a slightly larger width than the original pulses transmitted over beam 69. The timing diagram at the bottom of column 62 clearly shows 90.91. and 92 that these special pulses are emitted individually at the instants of reception of responses from the aircraft.

   We see, for example, that the instant the response of the rockiest plane 71 reaches the lighthouse 68, a special micrometer wave pulse is emitted and begins to propagate outward again. . /
Summarizing the above, it can be seen that, for any airplane, a complete operating cycle comprises three successive transmissions. The first of these propagates outward on the narrow beam from the headlight to the aircraft in question; the second takes place in all directions and, as a result, part of its energy returns from the plane to the lighthouse; the third transmission propagates outward in all directions, from the headlight to the aircraft.

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   We will now consider the signals which would be observed by a particular airplane, for example by the airplane of the observer 71, assumed to be 9 km away along the radius at 15 represented in the diagram. First of all, this aircraft receives a synchronization signal 81, accompanied by an interrogation signal 89, these two signals reaching it simultaneously. In response to the synchronization signal: the aircraft performs some local actions such as starting a sweep circuit, but it does not emit any special signals.



  In response to the interrogation signal, the aircraft radiates an 84 response signal.



   After a suitable interval, the aircraft receives from the headlight a weak signal 90 which represents its own response, which is sent back to it. Still later, said aircraft receives two other similar weak signals, 91 and 92, from the lighthouse, which represent the responses: from the other two aircraft, returned to the observer aircraft.



  In the interval between these weak signals from the lighthouse, the aircraft also receives two response signals 87, 88 from planes 74, 75, but the arrival of this energy will have no consequence, since the aircraft is not organized to receive signals at this wavelength during the cycles of application of the 3.PR principle.



   The time intervals between the arrival of the synchronization signal 82 and the arrival of the three special signals 90, 91 and 92 are, as can be seen, directly proportional to the radial distances from the lighthouse 68 to the three planes 71, 74, 75 located on lazimut at 15 shown in the timing diagram. In this way, if, on the observer airplane, a simple radial sweep is applied to the beam of an oscilloscope and if the said beam is, / made brighter for a short time, in the usual way, at the same time. The 'arrival time' of each of these three special green signals, the distances of the three planes located at L5 from direction will be indicated appropriately.



   To make this indication correct as regards the azimuth, it suffices to provide a rotation of the deviator system of

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 the oscilloscope in synchronism with the rotation of the headlight beam. This can easily be accomplished in a number of ways, for example by means of an engine rotating very slightly faster than the beam and a start-stop clutch releasing the rotating shaft, in response to a special signal. sent by the lighthouse whenever its beam passes / through the steering! lord.



   The above discussion has only taken into account the special case shown in column 62 of Figure 1.B where the beam is in alignment with the aircraft of observer 71. But, in other cases, the The operation is essentially the same, except that the interrogation signal 62 is not heard on the observer's aircraft when the latter is en route in any other direction. Column 66 of figure 1.0 relates to the case where the rotating beam 69 no longer strikes the plane of the observer 71 nor any of the two other planes 74 and 75 located on the same azimuth at 15, but strikes an airplane. 76, about 16 azimuth, as shown in the top image of this column.

   The second image of the column indicates the aircraft located at 16 responding with an omni-directional signal (radiated UHF pulse 84) and we can also imagine the lighthouse 68 as emitting a special signal of micrometric waves in all directions, the. said emission being triggered by the arrival of the response pulse coming from the aircraft 76.



   If we now turn to the timing diagram at the bottom of column 66, we will see that this is quite similar to the one which would have been shown in column 62, if there had been only one airplane at azimuth 15, so that only one response pulse would have been returned to the lighthouse and only one special radiation would have been emitted from said lighthouse. Apart from the differences caused by the presence of a single plane instead of 3, the time diagram of column 66 is still distinguished by the fact that the original powerful pulse of 83 micrometer waves from the lighthouse is not represented spreading to

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 outside. simultaneously with the sync pulse 82 which initiates the cycle.

   This is because the timing diagram only shows signals along the arbitrarily chosen radius of 15, whereas at the instant shown in column 66 the micrometer wave beam is directed slightly to the right of. this ray.



   The signals received on the observer's aircraft 71 are all represented in the timing diagram of column 66. First, the synchronization pulse 82 is received, without being accompanied by the interrogation pulse 83. Then, the response pulse 93 from the aircraft 76 hits the observer's aircraft, but this has no result, as previously explained. Then, the special pulse 93, emitted in all directions by the headlight 68, at the time of arrival of the response pulse 92, is received on the observer's aircraft. Eventually, the energy 85 reflected from mountain 72 strikes the observer's plane, but to no effect.



   As in the previously examined case, the time interval between the arrival of the synchronization pulse and the arrival of the special pulse is proportional to the radial distance of the aircraft being explored (i.e. aircraft 76, in this case).



   ,
In this way, the radial exploration of the oscilloscope of the observer's airplane correctly represents this airplane at the appropriate radial distance. Since the oscilloscope's deflector system is assumed to rotate in synchronism with the headlight beam, the spot representing that aircraft will also be at the correct azimuth.



   Similarly, all other airplanes within the effective range of the beacon will be successively scanned and appropriately represented on the oscilloscope of the observer's airplane. '
To avoid confusion in the above description of how a 3.PR reproduction is produced on board an airplane, we have limited ourselves to a single airplane 71. The other airplanes have been considered only as having response equipment, but the indication reception equipment of these other airplanes

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 -have been neglected.

   Nevertheless, it is evident that each of the airplanes moving within range of the headlight may be provided with a complete and precise indication system similar to that provided on the particular airplane in question. Each of these systems indicate the positions of all airplanes, including that of the airplane on which the reproduction takes place.



   Points on land, marked by means of active repeaters (response beacon) may also be indicated during the 3.PR operation, in the manner above indicated for the reproduction of airplanes. Natural obstacles and passive repeaters, however, will not appear on the 3.PR reproduction, since depicting these would provide no more information than can be obtained from a map.



   In short, the principle of the radio beacon system (RLS) with regard to its operation, is the same as the principle of operation of conventional radars, except that the transmitter is largely separated from the receiver and that, therefore parallax correctors are needed to eliminate distortions resulting from the separation or shifting of these two parts of the system, and the calculation or determination of the distance has to be done.



   In RLS operation according to the present invention, the same general principles are used. In this case, however, the transmitter and its rotating narrow beam antenna are located on the ground, while the receiver, with its receiving antenna not directed, is located on an aircraft which may be several kilometers away.



   There is no great difficulty in determining the direction of the obstacles whose reflections are received at any time. In FIG. 2, if the transmitter 68 is directed to the South-South-West, at the time considered, it is clear that all the obstacles encountered by the beam from said transmitter must be on a straight line extending south-southwest from the point of emission. As a result, the deflector coil of the indicating oscilloscope on the airplane may

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 be turned in such a way that at this moment it deflects the oscilloscope beam radially to the direction representing the South-South-West.

   As the oscilloscope deflector coil is located on the airplane and the rotating beam is on the ground, a synchronization member is necessary to orient this coil in the same direction as the beam, but such synchronization members are relatively simple and safe.



   To explain how the correct distance can be determined despite the offset between the transmitter and the receiver, reference can be made to figure 2. Point L represents the beacon or transmitter turning on earth 68, points 0 and 0 'represent reflective objects and point A represents the aircraft 71 which carries the receiving equipment intended to provide the RLS indication which is now in question. The zig-zag line extending south-
Southwest from 68 represents the narrow beam radiation on the one hand at object 0 and the length of this path from L to 0 (or to
O ') is indicated by the letter M (or by M').

   The zig-zag line from 0 to A represents 1! Reflected energy propagating from the object to the airplane and the length of this line from 0 (or 0 ') to A is denoted by the letter P ( or P '). Plane A is assumed to be 9 km southwest of lighthouse L and the solid line C represents this distance, that is to say the separation distance between the two parts of the radar.



   We will now consider a particular impulse of energy radiated towards the south-southwest from the lighthouse towards objects 0 and 0 'and reflected by these objects towards airplane 71. It is clear that this impulse will first reach object 0 and only then will reach the other object 0 '. The total time taken by the pulse to propagate from L to 0 and thence to A is proportional to the sum of the distances M + P. Analogously, the total time between the radiation of the pulse at L and its arrival at A after reflection on 0 'will be proportional to M' + P '. It is therefore clear that the pulses from the two objects do not reach the aircraft 71 at the same time, but successively.

   It is

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 also clear, that if aircraft 71 is at any point except directly on the extended LO 'line (i.e. anywhere except a point such as B) the reflected pulse from 0 will always arrive at the The first and the pulse of 0 'the second, exactly couse in a normal radar, The only difference is that the lengths of the delays are not exactly proportional to the distances from L to the objects and, therefore, if the a linear sweep was used on the oscilloscope, the distances would be distorted.

   To overcome this drawback, it is necessary to make the scanning circuit nonlinear such that it begins to move from the center of the screen very quickly and then slows down more and more, in accordance with a certain cubic law.



   At the particular moment shown in Figure 2, the beam from L to the two objects is assumed to be directed to the South-South-West so that the angle n is 157.1 / 2. The plane is pictured 35.1 / 2 southwest of the lighthouse so that the angle is only 125.1 / 2.



  In this way, the angle p (which is equal to the difference between n and n ') is 32. The distance C between the aircraft and the lighthouse is assumed to be 9 km.



   From these particular values of the angle p and the distance C, we deduce the length of the indirect path M + P is about 11.8 km. (Assuming that 0 is 7 km from L) and, therefore , the pulse propagating from the lighthouse to 0 and, from there, to aircraft 71 will have to travel 11.8 km. For synchronization, another pulse is sent at the same time directly from the beacon to the aircraft on along the path C.

   As this direct impulse only crosses 9 km, then aue the indirect reflected impulse crosses 11.8 km, the difference in path of these two impulses is about 2.8 km, taking the propagation speed of all the impulses as equal to 186 m. per microsecond, the aircraft will observe a delay of about 15 microseconds between the arrival of the direct impulse from the headlight and that of the indirect impulse reflected on the object C.

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   To correctly represent the fact that object 0 is 7 km from the lighthouse, the scanning voltage which deflects the beam of the oscilloscope on the plane, must, therefore, have a Speed such that in 15, micro -seconds it deflects the beam at a distance corresponding to 7 km. (ie 7 cm. if the desired scale is 1 / 100,000).



   From another object such as 0 ', however, (the distance M of which is assumed to be 10 Km,) the sum of the paths M + P is equal to approximately 15.3 Km, or 6.3Km. longer than the path of the direct impulse. Thus, the delay time of the pulses reflected on 0 'will be 34 microseconds, or more than double the delay time of the pulses reflected on 0. For a correct indication of the object 0' the Sevra scanning circuit, for example Therefore, produced a deviation corresponding to 10 km. (ie 10 cm. of deviation) in a time of 34 microseconds.



   If we compare this last requirement with the previous one, we see that, in the first 15 microseconds, the beam must move 7 cm. whereas in a total of 34 microseconds it should only produce a locm deviation. In this way, it should propagate over two centimeters during the first 15 microseconds, and only three centimeters during the following 19 microseconds. If it is assumed that it is necessary to apply to the oscilloscope 10 volts to produce a deviation of one centimeter, (that is to say to represent 1 km. Of distance) the necessary sweep voltage should be rise from 0 to a value of 70 volts in the first 15 microseconds and then rise more slowly from 70 to 100 volts in the following 19 microseconds.



   It is clear that as the beam of the headlight turns farther so as to increase the angle p up to a value greater than the 32 previously assumed, the mode of operation described above must be reproduced with respect to the new series of objects which are then in line with the beam. The same applies to

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 all other values of the angle p a corresponding different curve of the scanning circuit is required.



   These curves do not only vary as the angle p changes, they also vary for different values of the distance.
C. So, if the distance C from the lighthouse to the aircraft is assumed to be 3 him. instead of 9 km. a different family of curves will apply.



   Although the curves vary in an apparently complicated way with the variations of p and, also, they change scale with the radiations of C, it turns out that they can practically be produced by the addition of two curves. very simple, as will be explained more fully below.



   The RLS reproduction production method can therefore be summed up in two stages:
1 - rotation of the oscilloscope deflector coil in synchronism with the beam rotation of the lighthouse on the ground, by means of any synchronization device -
2 - producing a nonlinear sweep, fast at the start and then slower.



   The shape of these curves, and therefore the speed of movement of the sweeps must vary at the different values of the angle p and the distance C. Thus, to obtain a correct indication, it is necessary that the airplane knows its own distance from the headlight, as well as its relative azimuth angle to the headlight (measured from the direction of the headlight beam at that time). This relative azimuth angle p is easily found, by rotating the beam uniformly and observing the times when it passes over the aircraft itself, and synchronizing an axis with this rotation. The distance C is determined by another mechanism, of a more or less usual type, described below.



   The need to really know the proper position of the airplane relative to the headlight, in order to obtain a correct RLS indication may, at first sight, appear to be a disadvantage. In

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 In reality, however, this is one of the extremely important advantages of the invention, as it makes it possible to verify the correctness of the proper position of the aircraft for an inexperienced operator, simply by noting whether the various fixed objects shown on the oscilloscope screen correspond in shape and relative position to the same objects on a map.

   If any error occurs in the aircraft own position determining apparatus which measures the aircraft's radial distance or its relative azimuth from the headlight, a corresponding distortion of the RLS indications will occur, so had natural obstacles and active and passive repeaters will no longer form an image corresponding to that printed on a map of the region. Indeed, no error or series of conceivable errors occurring in the mechanism can result in the correct form indication of the terrain, if the determination of the proper position of the airplane is incorrect.



   Although the two fundamental functions of the proposed system are the 3.PR and RLS functions, as performed by a three-way radar and a rotating beacon system, it has already been stated that in order to properly produce the RLS indication, the The fitting of the airplane requires knowledge of its own distance and of its azimuth relative to the lighthouse. Determining these two factors can be done in a variety of different ways, but the preferred way of proceeding is as follows:
The azimuth of the airplane is determined by noting the time elapsed between the moment when the headlight transmits a special signal 80, meaning that its beam is then crossing the North direction, or any other fixed reference direction, and the instant somewhat later where the beam from the rotating headlight passes over the plane.

   The distance to the aircraft is determined by means of a simple notched tracking device or dual acting self-regulating threshold device, a. well known manner, to constantly align with a previously selected pulse characterized by a particular delay time with respect to the reference pulse.

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   The most convenient is to apply this principle of the notch follower device to the pulses of special micrometric waves 39 which are emitted by the lighthouse in connection with the operation 3.PR of the system, since the time-distance relationship is linear for these pulses. . It is well known that notched follower devices do not operate as reliably when supplied with a very large number of pulses.



   Consequently, the only pulses that need to be applied to the slot trackers are the special micrometer wave pulses emitted by the lighthouse at the times when the beam of the latter is in alignment with the observer's plane. In Figure 1.B. this means that only the special microwave impulses 89, shown in column 62, should be applied to the notch follower mechanism All other types of pulses and all other special analog microwave pulses emitted during other parts of the cycle are eliminated by means of screens before application to the notched follower assembly.



   Usually, the results of this will be that only pulses representing the position of the observer's aircraft will be supplied to the track follower assembly, as there will usually not be more than two planes plus or minus. half a degree of the exact azimuthal angle of the observer's plane, unless there are more than 360 planes circling the field at the same time.



  However, to illustrate the most disadvantageous conditions, the diagram of Figure 1 has been drawn assuming that three different airplanes 71, 74 and 75 are in flight at the same time at the same azimuthal angle. Under these conditions, three separate pulses will be applied to the notch circuit at each pulse period, as shown in column 62. Even under these conditions, the notch follower mechanism will still correctly follow the pulse on which it is already settled.

   So if the plane is the only one in flight at its particular azimuthal angle at the time. he penetrates

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 in the effective field of the lighthouse, its notch, which then receives only the impulses corresponding to its own position will adjust correctly to the said impulses and will then follow them even during the time intervals where several other planes will occupy the same azimuth.



   Any tracking device with notches is theoretically exposed to the possibility of changing the runway so as to follow an unwanted airplane, if the said airplane comes to fly exactly above or below the desired airplane, so so that all of them coincide both in azimuth and in distance.

   For the sake of economy and simplicity, it is envisioned to employ in the proposed system a relatively simple form of notched follower device and, therefore, it is to be expected that said device will follow. notched vessel is subject to the runway changes mentioned above when any other aircraft is in flight within about 1/2 degree of the exact azimuth of the observer's aircraft and at the same time within 'a certain. critical distance zone extending from the observer's plane up to 480 km. beyond.



   More important than that of the frequency of the track change is the question of its amplitude. With the invent-ion system, the occurrence of a track change of the notched follower will be a nuisance, but not a danger. First, the pilot will see the image of his plane gradually approaching one of the other spots on the screen, until they merge. At this time, no error has occurred.



  When the combined spot divides again such that it appears as two spots gradually deviating, the pilot will be clearly warned that there is a possibility of an indication error. If the divergence of the two spots occurs in such a way that it results in different azimuths, the error, if any, will be immediately corrected. If the planes only separate from the point of view of their radial distances and the notch follows the wrong plane, this will be immediately revealed by

  <Desc / Clms Page number 22>

 a progressively increasing distortion of this RLS indication.



  The reason for this is that the RLS indication depends, as regards the correction of its shape, on the correct position of the notched follower device as previously mentioned.



   Whenever an incorrect track of the notch follower mechanism is thus observed, the pilot can return the notch to its correct track by hand, adjusting the system until the. The card takes the correct shape that can easily be checked by comparing it with the undistorted reproduction of the 3.PR on the same screen.



   It is therefore clear that the question of putting the notch on the wrong track is primarily a question of convenience, and not a question of false information. In fact, the system can be operated without any slotting device, if the pilot sets the system distance factor by hand, whenever he wishes to read the LRS indication.



   To summarize the operation of the radio beacon system sub-period, energy is transmitted in the form of a thin beam 69, from the transmitter 68. This transmitted energy can then be reflected by the various reflective objects and received on various planes. Simultaneously with the transmission of the beam energy 69, other energy is transmitted in a plurality of pulses, retort shown at 70, for the purpose of starting the scan circuit on the separate indicator receivers. .



  This pulse works to produce a linear sweep of the indicator.



   The pulses 70 are also repeated by each of the planes carrying the repeaters and these repeated pulses are received on other planes to produce the indications of the position of said planes. In this way, on the indicator receiver, for example, on the airplane 71; the synchronization pulses 70 triggering the scanning circuit and the reflected energy at the wavelength of the beam 69 as well as the radiated energy will be received.

  <Desc / Clms Page number 23>

 secondary of other airplanes. These secondarily reflected and otherwise radiated pulses are clocked in accordance with the spatial position of said objects relative to the scanning circuit, so that their position on the indicator will be clear.



  To understand the operation of the system in more detail, that of the main elements of the transmitter equipment of the lighthouse and of the receiving equipment on the observer's aircraft will be described in detail in conjunction with Figures 3 and 4 which are the diagrams. of operation of the transmitting and receiving apparatus as used at stations 68 and 71. As a complete cycle of rotation has 1,200 individual sub-periods, each of which is initiated by the emission of a synchronization pulse, but may include three successive complete transmissions and three receptions, it is clear that only a small part of the complete rotation cycle can be examined.



   The timing diagram of Figures 1.A, 1.B, 1.0 shows enough sub-periods to explain the effect of the special reference signals, or North signals, which are emitted at the instant the beam passes through North, and to explain the effect of the tracking circuit on the observer's aircraft which is excited only when the beam passes through the azimuthal angle of 15 occupied by that aircraft.

   To understand all of these interesting features, diagrams have been drawn to show the 1 -Z sub-periods, which takes place when the beam passes north and the 61 and 62 sub-periods which take place when the beam passes through azimuth direction 15, as well as sub-periods 66, 67, to cover part of the period after the beam leaves the observer's plane and explores another plane located at a slightly azimuth different .



   The full successive account of all these subperidoes would be longer than necessary and consequently, in the description which follows, we will only retrace in detail the subperiods 66 and 67, because these relate to a typical general case, in which the beam is not directed towards the North, nor towards the plane of

  <Desc / Clms Page number 24>

 the observer (see figure 1, C) but is in line with another plane and a natural obstacle. After a full examination of these two sub-periods 66 and 67, one will briefly note the special characteristics of other sub-periods.



   The period control circuit 94 of the transmitting station, FIG. 3, outputs control signals selectively on the conductors 95 to 100, to control the operation of the various parts of the assembly. The control circuit 94 can be any. as a cyclic switching circuit, preferably under the control of the motor 102, which also serves to rotate the beam 69. At the start of each sub-period 3.PR, except at the North position, the control signals are applied to conductors 94. 95.96 and 101. Sub-period 66 was chosen for particular consideration because it clearly illustrates the general principles.

   The control signals applied to conductor 95 from circuit 94 triggers the normal pulse width modulator 103 of the transmitter 104 and thereby emits a high power micrometer wave pulse of normal width W (e.g. 1. 1/2 microsecond). The control signal applied to the conductor 95 puts the electroinque switch 105 in the condition necessary to route these pulses to the beam radiator 106 and a powerful micrometer wave pulse is radiated in a narrow beam centered around an azimuthal angle of 15. 3/4 degrees.



  Assume, for the convenience of description, that this beam is exactly one degree wide, so that it narrowly avoids observer 71 (Figure 1.0) and the other two planes 74 and 75 to azinut 15. Suppose, however, that this beam strikes just another aircraft 76, in flight in an azimuth at 16, as shown in FIG. 1.C.



   While this beam of micrometric waves69 is emitted from the radiator 104, as indicated above, the control signal of the driver 96 actuates the pulse generator 107 and causes the transmitter 108 to deliver a synchronization pulse. - tion of width W and lower frequency (carrier frequency

  <Desc / Clms Page number 25>

 UHF) radiated in all directions by antenna 109. This pulse is represented by line 82 of the time diagram of Figure 1.C. The width of said pulse is chosen such that it characterizes the cycle as 3.PR cycle.



   In the receiver of figure 4, on the observer's plane the micrometric wave signal (we supposed to avoid, this plane) is not received, but the synchronization signal 3.PR of lower frequency is captured by the antenna 110 and then transmitted, through the coupler 111, to the UHF receiver 112. From the output of this receiver 112, this synchronization pulse 3.PR passes through the width selector 113 and triggers the linear scanning circuit 114 and the control signal timing apparatus 115. Further, this signal is also applied to the combiner circuit 116 through the coupler 117, and thence to the control gate 118 of the oscilloscope 119, so to produce a bright spot, but this is to no avail, as the beam has not yet started to move away from the center of the screen.



   The signal applied to the scanning circuit 114 causes the generation of a linear sweep which passes through the coupler 120 and the combiner circuit 121, towards the deflector coil 122 of the oscilloscope 119, thus causing the beam to travel towards the axis. exterior in a linear fashion.



   The signal applied to the control timer 115 causes the latter to deliver a certain number of blocking and limiting signals which arrange the circuit for the type of operation 3.PR, as follows: first of all, the blocking signal applied by line 123 to couplers 117 and 124 prevents this combiner circuit 116 from letting, during the following 800 microseconds, any signal other than the special micrometric wave signals of width W3, characteristic of three-way operation ap - folded through the coupler 125:

     Second, the signal applied through line 126 to. limiter 127 prepares this limiter to be opened by a micrometric wave signal of maximum intensity

  <Desc / Clms Page number 26>

 such as that produced when the beam is pointed at the aircraft.



  As this is not the case during the present cycle, this signal applied to limiter 127 remains without result. Third, the blocking signal applied from the timer 105, through the sign 128, to the input coupler 129, of the combiner circuit 124 blocks the latter with respect to the input line 128, so that only, the linear sweep waves from the sweep circuit 114 can pass through this combiner circuit to the diverter coils 122.



   Thus, in response to the very high frequency synchronization signal of width w2, the receiving apparatus of the aircraft only begins a linear sweep outward from the oscilloscope beam and prepares to remain unresponsive to all subsequent signals except the special micrometric wave signals responsible for the 3.PR function.



   Referring now to FIG. 1.c, it will be noted that the pulse of micrometric waves with high beam power first strikes the airplane 76 and then the mountain 72. The reflections which take place on the mountain , as shown in the second image of column 66, and in the time diagram at the bottom of this column, have no effect, because the receiving equipment is now in a condition to indicate only the special micrometric wave signals. of width 93. Aircraft 76, however, responds to the powerful micrometer beam pulse as follows (for the time being, the diagram of Figure 4 can be considered to represent l equipment carried by the aircraft 76).



   Aircraft 76 receiver equipment circuitry receives the strong micrometer wave signal and the very high frequency synchronization signal 3.PR almost simultaneously. The synchronization signal 3.PR produces the same effects which were explained previously with regard to the airplane of the observer 71.

   Direct then healthy directed radiation from the lighthouse is picked up by antenna 130 and received by receiver 131 from where it passes through normal width selector 131, line 132 and triggers very high frequency transmitter 133 , thus producing a very high frequency response as shown in the second frame

  <Desc / Clms Page number 27>

 in column 66 of Figure 1.C and at 82 on the corresponding time graph of that figure. It should be noted that the transmitter 133 requires, for its triggering, a high voltage and, therefore, can only be triggered by `` the direct impulse of the headlight which is several thousand times higher in energy than the impulses corresponding reflections.

   Microwave receiver signal 131 also passes through maximum signal selector circuit 134, to perform certain functions, but these will not be considered at this time, as they have no relation to the response sent by the. plane. The corresponding effect of the observer airplane 72 will be described later, in connection with cycle 62.



   If we now refer to Figure 1, we see that the response of the aircraft 76 returns to the lighthouse 68 and causes the emission of a special micrometric wave signal 93, of width W3. The corresponding effect takes place as follows in the diagram of figure 3.



  The incoming very high frequency wave (response) is picked up by antenna 135 and received by receiver 136, from which it is transmitted not only to suitable indicating equipment on the ground 137, but also to the special signal modulator. pulse width W3 138 of the transmitter 104. As a result, this transmitter 104 transmits a pulse of micrometer waves of special width, for example 2 microseconds. This pulse passes through the electronic switch 103, then in its normal position, towards the circular diagram radiator 139, so as to propagate in all directions, as shown in FIG. 1.C.



   In the receiver equipment of the observer's airplane, this special micrometric wave pulse is picked up by the antenna 130, received by the receiver 131 and applied, through the special width selector 140 and the coupler 125 to the combinator circuit 116.



   Although said circuit 116 is blocked with respect to its other inputs 117, 124, it is not blocked with respect to its input 125 and, therefore, routes the signal to the gate.

  <Desc / Clms Page number 28>

 intensity control 118 of the oscilloscope 119. As a result, a bright spot is produced on the screen of said oscilloscope, representing the position of the aircraft 76, signaled by the beacon 68.



   As the deflector coil 122 of said oscilloscope has been energized by a linear sweep from 114, at the time of arrival of the synchronization pulse 3.PR. the degree of radial deviation of this beam will correspond, at this instant, to the time elapsed between the arrival of said 3PR synchronization pulse and the arrival of the special micrometric wave signal. This delay is proportional to the radial distance of the aircraft 76 from the lighthouse, as can be seen from the timing diagram of Figure 1.C. and, therefore, the spot then produced on the observer's aircraft oscilloscope 72 is correct with respect to its degree of radial deviation.

   With regard to the correction of this spot in azimuth, the rotation of the coil 122 is practically synchronized with the rotation of the headlight beam, so as to indicate this spot in the correct angular direction. How to ensure this synchronism will be described later.



   The 3.PR cycle is now almost complete. At the end of the 800 microsecond interval, the timer 115 removes the various blocking and limiting signals which have temporarily prepared the equipment for this mode of operation and the receiver is then ready for a new cycle. .



   Cycle control circuit 94 of Fig. 3 outputs control signals through leads 95, 96, 99 and 100 at the start of each RLS sub-period as indicated in columns 1, 61 and 67 of Fig. 1.C. Sub-period 67 was chosen as the best illustration of the general principles. As before, the control signals on leads 95 and 96 cause a powerful pulse of micrometric beams to be emitted from radiator 106.

   The control signal on lead 99 also causes simultaneous radiation in all directions from antenna 109 of a very high frequency sync pulse, but in this case it is the frequency modulator.

  <Desc / Clms Page number 29>

 RLS width 141 of the transmitter 108 which performs the trigger and, consequently, the widthW4 of the pulse is such as to signify the beginning of an RLS type cycle. The control signal applied to the conductor 100 serves to block the other high frequency receiver 136 for 800 microseconds, so as to avoid the emission, from the headlight, of special micrometric wave pulses which are only necessary. in 3.PR cycles.



   In the receiver of the observer's aircraft 71, the RLS synchronization signal is received by the receiver 112 as in the previous step, but this time it passes through the width selector 142, instead of 113, because it has a width W4 characteristic of the RLS cycle. The energy supplied by the width selector 142 triggers the linear sweep circuit 114 in the same way as in the previous case, but does not energize the control timer 115. Therefore no part of the combiner circuit 116, nor of the combiner circuit 121 is not blocked. Likewise, limiter 127 is not prepared for possible operation.



   When the linear scan circuit 114 begins to produce a sawtooth voltage to the combiner circuit 121, it simultaneously supplies a voltage analogous to the cubic law scan circuit 143 and, accordingly, the latter begins to produce. to reduce a suitable corrective tension, of curved characteristics, which will be examined in more detail later. This curved voltage supplied by circuit 143 is of such form that, when added to the sawtooth scanning voltage produced by circuit 114, with a suitable recovery to ensure the sum of the two voltages towards the negative, l The resulting wave is then suitable for the sweep required for RLS operation.

   Accordingly, the voltage supplied by the DC combiner and restorer circuit 121 is applied to the deflector coil 122.



   Referring now to figure 1.0, we see that the beam 69 representing the pulse of powerful micrometric waves propagates outwards so as to strike the plane 76

  <Desc / Clms Page number 30>

   -and the mountain 72. The airplane responds as before when it has been struck by said beam, and, as before, the mountain reflects part of the energy of micrometric waves which strikes it.

   Thus, a reflected pulse of micometric waves and a response pulse of very high frequency but lower frequency are transmitted in all directions from the plane and from the mountain, respectively, so that they; of which received by all the other planes of the vicinity.



   As the aircraft 76 is closer to the lighthouse 68 than the assembly 72, its reflected impulse reaches the observer's airplane 71 earlier than the micrometer wave pulse reflected from the mountain. The reception of these pulses will therefore be examined in the corresponding order.



   When the repeated pulse by the aircraft 76 reaches the observer's aircraft 71, it is picked up by the antenna 110 and transmitted through the coupler 111, to the receiver 112, from where it passes to the coupler of input 117 of combiner 116, and from Ia to intensity control grid 118 of oscilloscope 119. Since the proper sweep voltage has been applied to deflector coil 122, the radial deflection of the beam at this instant is that suitable for the correct representation of the distance between the aircraft and the headlight 68. The deflector coil 122 rotating in suitable synchronism with the headlight beam, ensures the correct indication of the asimuth.

   In this way, a spot appearing on the oscilloscope will correctly represent the airplane 76, both in azi- and / mut in radial distance.



   A short time later, the energy of micrometric waves reflected on the mountain reaches the aircraft 71. Said energy is picked up by the antenna 130, received by the receiver 131 and applied, through the width selector. 131.A, to the input coupler 124 of the combiner circuit 116. Since no part of this combinator circuit is then blocked, the pulse passes through to the intensity control electrode 118 of I. oscilloscope 119. As

  <Desc / Clms Page number 31>

 in the case of the repeated pulse of aircraft 76, this pulse also produces a correct indication of distance and azimuth, but generally of somewhat lower intensity.

   By providing separate intensity control in the input couplers of circuit 116, the representations of natural objects and passive repeaters can be adjusted to any desired brightness regardless of the brightness employed in the representation of active repeaters and others. airplanes, following the LRS principle and also regardless of the brightness used for the 3.PR indication.



   In the foregoing description, the operation of 3.PR and RLS has been traced without explaining in detail all of the characteristics. For example, we have assumed a synchronous rotation of the coil 122. We will now describe the way in which this synchronism can be obtained.



   Referring to figure 1A, we see that, when the beam of the lighthouse passes through the North, the successive periods of the said lighthouse are executed as usual, except that the normal signal of synchronization '3.PR usually transmitted to. start of each even sub-period is temporarily replaced by a slightly modified signal intended to characterize the north orientation of the beam.



   This special North synchronization signal may be of a width W5 somewhat different from the width W2, such that it passes through the width selector 113 of the receiving apparatus and the. 3.PR cycle takes place in the same way as usual.



  This special North signal, however, also passes through the width selector 144, so as to energize the start-stop clutch 145 through the line 146. The width selector 144 is made more selective than the selector 113, as such. so that the pulses - of width W2 do not pass.



   A precise speed motor 147, with reduction gear and speed control, drives the input shaft 148 and the clutch 145 at a speed very slightly greater than the rotation of the beam, which in the example chosen, is 50 revolutions per minute.

  <Desc / Clms Page number 32>

 



  When the system is first put into operation, the engine rotates the input shaft 148 of the clutch 145, but the output shaft 149 cannot rotate until the clutch is actuated. by an electrical impulse. The next time the headlight beam passes north, the clutch is actuated to allow the output shaft to make one revolution. As the headlight beam is supposed to rotate at exactly 50 rpm, while the engine is running slightly faster, the start-stop clutch output shaft completes its turn a few milliseconds before the headlight beam reaches North direction again and the tree stops for a corresponding short interval of time before being released again to begin another turn.

   In this way, the output shaft 149 of the clutch 145 rotates practically in synchronism with the beam of the headlight and its angular position corresponds exactly at all times to that of the beam of said headlight.



   In the particular arrangement shown, the output shaft 149 of the clutch 145 is connected directly to the magnetic deflection coil 122, so that a "fixed map" indication is produced with the steering. North in a fixed position with respect to the screen, that is to say always at the top of it. This mode of indication has the advantage of being consistent with the mode of representation of the lighthouse in the center, which naturally results from the simple forms of the 3.PR and PLS indications. To indicate the heading of the airplane, as well as its position on such a fixed map image, a heading indicator 150 is provided. The latter can have the form of a transparent disc bearing, lightly engraved on its surface. a large number of arrows.

   Said heading indicator dial is driven by a compass repeater 151, controlled by any type of compass.



   It is clear that a self-orienting map can be given if preferred by the provision of a differential gear train between the clutch 145 and the coil 122 and, by the connection of the compass 151 with the so-called gear train. The indication will orient itself

  <Desc / Clms Page number 33>

 - itself in such a way that the top of the screen corresponds to the heading of the aircraft. In this case, the direction of North would be indicated on the screen by a dial such as 150, or by any other suitable means.



   To produce the radio beacon indications, remember that the indicator scanning circuit must take into account the distance 0, indicated in figure 2. As the receiver is normally on a moving airplane, this distance must be determined continuously. According to the invention, when the beam from the headlight 68 actually passes over the observer's plane
71, certain additional operations are performed, in order to determine the position of said aircraft. One of these special operations, the determination of the azimuth of the airplane, is carried out at each sub-period. The other special operation, distance determination, is accomplished by means of the slotted follower assembly, which is only actuated during even sub-periods.

   The description of the sub-period 62 will therefore serve to explain these two operations.



   In general, sub-period 62 occurs in the same way as all the other 3.PR sub-periods described in connection with sub-period 66. Since the powerful pulses of beam micrometer waves coming directly from the headlamp strike the aircraft during this cycle, some additional operations take place.



   When such a powerful impulse arrives at the observing aircraft, it is picked up by antenna 130 and received by receiver 131. From the output of this receiver, the powerful impulse passes through the selector switch. width 131.2 until ordering the transmitter
133, thereby causing the transmission of a response signal, as previously described. In. In addition, two important effects are produced on board the observer aircraft. One of these effects is the determination of azimuth, and the other is the determination of distance.



   In order to determine the azimuth, the powerful pulse from the -131 receiver is applied to a maximum selector of

  <Desc / Clms Page number 34>

 signal 134, biased so as to select only the most powerful of the pulses produced during a complete rotation cycle.



  From the output of said selector 134, the pulse is applied to the start-stop clutch 153, through line 154. This star ts top clutch is similar to the clutch 145 mentioned above. , and it is driven by the same motor 147. The output shaft of 154 is therefore synchronized in much the same way as the output shaft of 148. except that the timing reference point n ' is not the moment when the beam from the lighthouse passes through the North, but rather the moment when the said beam passes over the observer's plane. In this way, the angular position of the output shaft 155 of said clutch 153 constantly corresponds to the angle p of FIG. 2.

   As the angle p is one of the necessary parameters in the case of LRS operation, the rotation of said shaft can be applied to the cubic law sweep circuit 143.



   The other parameter required by said scanning circuit 143 is the radial distance of the observer's plane from the lighthouse. This parameter is also obtained during the brief period when the beam from the headlight passes over the observer's plane. Only the 3.PR type cycles occurring during this interval are employed, which considerably reduces the number of pulses applied to the notch follower 152, so as to improve the operation of the latter.



   In order to let pass only the special impulses. micrometric waves emitted by the lighthouse during the moments of passage of the beam on the observer's plane, the limiting circuit 127 is provided, which opens only when it simultaneously receives the signal voltages control signal timer 115 and maximum signal selector 134, applied through derivative line 156. As selector 134 only provides signals when the strong pulses of the direct beam hit the aircraft and the clock 115 only provides its blocking limitation control signals during cycles of type 3.PR, it is clear that the

  <Desc / Clms Page number 35>

 Limiter 127 will only allow through the maximum pulses occurring during the 3.PR interval.

   Additional security is provided by the use of the special width selector 140 which allows only special micrometric wave pulses, width W3, to pass.



   It can be seen from Figure 1.B that the only signals of micrometric waves 90-92, which are received simultaneously with the strong pulses of micrometric waves are the signals shown in column 62, which represent the radial positions of the three airplanes assumed to be placed at azimuth angle 15. In the receiver apparatus of FIG. 4 therefore, the only pulses which from the receiver 131 can pass through the special width selector 131.A and the limiter 127 are the three successive pulses representing the positions of these three planes.



   In order to provide the necessary reference pulse to the slot follower circuit, the sync pulse from width selector 113 is applied to assembly 152 through line 157.



   The control timing pulses applied to limiter circuit 127 through line 126 are clocked based on width sync pulses W2. These pulses are the rectangular pulses of average width 158 of Figure 6 They occur only during the time when the narrow directional radiation is handled for three-way radar operation, so that only the pulses occurring during this interval of the sub-period will be present when the manipulated pulses are applied to limiter 127.



  In addition, the maximum selector circuit shown in FIG. 4 also produces a monitoring pulse only during the relatively narrow interval during which the micrometer wave beam is directed to the indicating receiver. This pulse, although relatively short compared to a complete cycle of rotation, is very long compared to the pulses 158 and can

  <Desc / Clms Page number 36>

 be as shown at 159, Figure 6. These two positive pulses 158 and 159 serve to bias the limiter circuit 127, so as to pass the received signal pulses from the width selector 140. As shown in Figure 6 it There are three of these pulses: 160, 161, 162.

   Because of the notched limiter system, it is desirable that only one of these three pulses is selected, to the exclusion of the others. Assuming that pulse 160 is the repeated pulse corresponding to the transmission from the observer's aircraft, it is this pulse that must be selected. In order to obtain this selection, and to have it followed by the device, so as to maintain the indication in a position representative of the distance, the notched follower assembly 152. As shown in FIG. 5, has been provided. the selected sun-chronization pulses, of width W2. can be applied through line 157 to a variable delay device 163.

   Said variable delay device is driven by a motor 164, which rotates to advance the delay of the variable delay device by half the width of the selected pulse 160, for each normal rotation of the radio beacon, when it is driven in one direction, and to delay the delay by half of this distance, when said beacon is driven in the other direction. The selected pulses 160 therefore normally fall between two control pulses applied to the notch limiter circuit 164, 165.



   These limiter control pulses are shown in Figure 6 at 166 and 167. The pulses 166 and 167 can be derived directly from the incoming pulses. The pulses delivered by the variable delay device 163. which may for example be a trigger circuit of the multi-vibrator type, are generally relatively wide pulses with inclined sides so that they can be suitably used in the control. , these pulses should be narrowed, preferably to a width less than the separation to be maintained between airplanes using the

  <Desc / Clms Page number 37>

 -system. It is clear, however, that these pulses must be sufficiently long in time, so that the airplane cannot pass beyond one pulse in two or three seconds.

   This is to be desired because, if the signal were to fade for two or three turns of the headlight transmitter, the airplane could go completely beyond the notch limiter control and, thus, the follower operation could not fail. accomplish properly. As a result, the output pulses from the delay device 6 pass through a shaping network 168 serving to restore the shape of these output pulses and to narrow them. These output pulses of 168 are applied to the notch limiter 164, so as to bias it sufficiently in the positive direction to pass any pulses applied to it.

   In this way, any output pulses of limiter 127 which occur during the application of pulse 166 to notch limiter 164 are therefore transmitted to the inverter control mechanism of motor 169.



   The output pulses of the delay device 163 are also applied through a fixed delay circuit 170, to a second shaping circuit 171, and, beyond, to the notch limiter 165. These pulses correspond to 167, FIG. 6 and they are sufficiently delayed to give rise to a time interval greater than the width of the output pulses of the limiter circuit 127. The pulses of 127 are also applied to the notch limiter 165 and, if they are applied during the present interval of the pulses 167, they are transmitted to the reverse gear command of the motor 169, to cause the motor 164 to make a revolution in the opposite direction from that produced by the pulses of the notched limiter 164.

   It can therefore be seen that, as long as a pulse 160, is suitably placed in time with respect to the pulses 166 and 167, the motor 164 remains stationary and its shaft 172 corresponds in angular position to the distance between the receiver and the radio. -headlight. However. , as the vehicle carrying the

  <Desc / Clms Page number 38>

 receiver moves, the pulse 160 can be moved to one side, retort indicates on the right side of figure 3, which causes the pulse 160 to coincide with the pulse 166. This voltage increase passes through the slotted limiter 164 and is applied to the motor reverse command, rotating motor 164 in a given direction by one turn.

   This causes the displacement of the variable delay device to be sufficient for the notch limiter pulses 166 and 167 to be displaced by half the width of the pulse 166. Accordingly, if the airplane does not move for the next turn of the lighthouse, the pulse 160 falls into the notch again and the axis remains stationary. However, if the airplane continues to move in distance, which tends to displace pulse 160, limiter pulses 166 and 167 tend to follow, so as to keep shaft 172 at all times substantially in alignment. with distance indication.



   The notched limiter pulses 166 and 167 are aligned at the start by means of a manual control 173. This knob can be controlled in position by observing the indications produced on the indicator 119, the adjustment being made until. when the indications suitably coincide with the position on the map. It is clear that, if desired, the whole notch follower system can be omitted, the settings being made la: zain for each reading. However, this involves rather tiring observation of the apparatus and does not allow it to operate as quickly as is desired.



   If no signal fading is required, the limiter system;. notches can be greatly simplified. With such an arrangement, it is not necessary to provide a single pulse limiter circuit with two notches shown in FIG. 5.



  The motor 164 can then be made to advance the notch by half the width of the pulse applied to each turn of the headlight. If the impulse did not appear in the notch, then the engine would be turned back one revolution,

  <Desc / Clms Page number 39>

 which would take the delay device back one step.



  The axis 172 would thus be kept oscillating from a small distance forward to a small distance behind the receive distance. However, the use of a single pulse would also allow distance measurements to be made more accurately, so that less separation could be assumed between airplanes facing the same azi- mut.



   In the foregoing description of the RLS type of operation, the mode of operation of the scanning circuit 143 of Fig. 4 has not been described, but it has simply been assumed that. this circuit produces the necessary correction voltage under the control of the axes representing the angle p and the distance C, figure 2.



  The necessary correction voltage was then indicated as combined in circuit 121 with the sawtooth linear sweep voltage of sweep circuit 114. Combiner circuit 121 was also assumed to bring the axis back to zero in the same way. known. The resulting output voltage in circuit 121 was assumed to correspond to the necessary cubic law sweep voltage.
To examine more precisely the mode of obtaining these sweep voltages, we will consider the trigonometric relationships relating to FIG. 2.

   In the triangle whose sides are C, M, P and the opposite angles c, m, p, the usual cosine law for the determination of one of the sides (as a function of the two other sides and of the angle that they understand) can be written as follows:
 EMI39.1
 P = \ /. 02 + MZ - 2 CJIÍ cos p If D represents the difference between the discharges of the direct pulse. te from L to A and the indirect impulse from L passing through 0 in FIG. 2, it is clear that D = P + M -0;

   and if ¯ is the corresponding delay observed between the arrivals of the direct and indirect pulses
 EMI39.2
 = (P + M - 0) / V

  <Desc / Clms Page number 40>

 (or v at the propagation speed in kilometers per microsecond, i.e. approximately 300). From the definitions of D and of it appears that
P = C + D - M = C + v ¯ - M
By replacing P with this value in the original equation,
 EMI40.1
 we obtain :

   C + v A-M = V7 + D.2 - 2CU, cos p
This equation can be solved for M, which gives:
M = 1/2 v ¯ (vA + 2 C) / (vA + 2 C 1/2 (1 - cos p)
This is the basic cubic equation which determines the shape of the sweep curves, since it defines the raial distance 1, ± of any obstacle from the lighthouse, as a function of the proper radial distance of the plane C, the easily measurable angle p and the observed pulse delay ¯. But this equation expresses the distance of the object directly in kilometers.



   To determine the corresponding deviation voltage needed, it suffices to assume a scaling factor which can be defined as the number of volts that must be applied to the indicator element of the oscilloscope to produce the deviation that l 'Or wants to represent a distance of one kilometer. If one wishes, for example, to use a scale to 100,000, and if the sensitivity of the indicator is such that 30 volts are required for 1 cm. of deviation, the factor S will correspond to 15.8 volts per km. indication.

   By inserting this scale factor S in the last equation obtained, we can write it as follows:
SM = 1/2 Sv¯ (v ¯ + 2C) / v ¯ + 2 C 1/2 (1 - these p)
As if! is the deviating voltage to be applied to the oscilloscope indicator at the instant when the impulse reflected on the obstacle 0 is received, (that is to say that the deviating voltage has asked microseconds after the start of the period) it is clear that this equation defines the voltage-time relationship necessary for the cubic law sweep.

   This equation can be written again as:

  <Desc / Clms Page number 41>

 
 EMI41.1
 -SM = [1/2 1/2 cos .SM = [l / 2 Sv A] - L 1/2 Sv 4Y + SC 1/2 (1 - cos 71. Fl / 4 2 "C2. 2 -J 1 / 4 S 222 C sin p 1 [1/4. 1 (Sa 1/2 (1-oosp 1
This latter form of the equation very clearly represents how the desired voltages are produced.



   By considering the four terms in brackets, we will see that the first corresponds only to a linear sweep, like the output voltage of circuit 114 of FIG. 4. The second term between parantheses is a fraction whose denominator is made up of by the same linear scanning voltage, plus a constant voltage depending on the distance C and the angle p. The third term between parentheses is a multiplication factor that also depends on 0 and p. The fourth term in parentheses is equal and of opposite sign to the value of all the rest of the equation at the start of the period (ie when ¯ = 0).

   Thus, the term in four parentheses corresponds only to a direct current recovery effect, or to a sufficient axis displacement to bring the start value of all the sweep voltage to zero.



   In FIG. 7, the circuit members shown inside the broken line corresponding to a possible form of sweep assembly which can be used instead of the assembly 144 of FIG. 3. The axes 172 and 155 entering this assembly of Figure 4 are again shown in Figure 5.



   Faders 174, 175 and 176 are endless faders whose sliders 177, 178 and 179 can rotate continuously in one direction and whose windings 180, 181 and 182 form closed arcs with taps at two dia- metrally opposed. The potentiometer 176 can be a low resistance potentiometer whose law of decrease is such that it outputs on line 183 a voltage proportional to SC, when its axis 172 is maintained at an angle corresponding to the distance C.



  The 174 potentiometer has a much higher impedance winding

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 high, whose law of decrease is such that it produces a potentiometric action proportional to 1/2 (1 - cos p) of the angle adopted by its control axis. The bias voltage SC hav p of the output of potentiometer 174 is added to the sawtooth sweep voltage coming from circuit 114, by means of a simple diode and capacitor circuit 184, 185 of the usual type used. for the restoration of direct current, which results in a voltage 1/2 Sv2À - SC 1/2 (1 - cos p).



   The only part of the circuit requiring special comment is tube 186, which is a cathode ray tube having a wide bible electrode 187, somewhat analogous to the tube known as a monoscope used for television testing. This type of tube can be set up to produce any operating relationship between the output voltage delivered by the target electrode and the deflected position of the cathode ray tube.



  Usually these tubes are arranged to give two-dimensional diagrams. In accordance with the present invention, the tube is arranged to produce an output voltage which varies according to an inverse law with respect to the deflection voltages applied to a pair of deflector plates 181. The other deflector plates 189 could be left at potential. fixed, so that the cathode beam would explore a single line of the goal. Preferably, however, a beam spread oscillation at oscillator 190 is applied to these other plates 189, so as to spread the beam as a wide, flat fan which can be run over the target electrode. under the control of a combined voltage of potentiometer 174 and scanning circuit 114.



   The output voltage of the target of the monoscope 186 is amplified in a stabilized amplifier 191, the gain of which is varied precisely, by means of the axis 172 so as to maintain said gain equal to S C. The attenuator potentiometer 175 can be bevelled, so as to give a transmission factor proportional to 1/4 swin2p '

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The energy delivered by the above-described cubic-law sweep assembly 143 can then be combined with the sawtooth sweep of circuit 114 of FIG. 4, in a confined current combiner and recovery circuit. 121. The resulting voltage produced will be of the form suitable for its application to an electrostatic controlled oscilloscope.

   For the operation) of the electromagnetically controlled oscilloscope, a power amplifier 192 is incorporated in the output circuit, in a known manner, with prior anti-distortion device, to compensate for the self-induction of the deflector coil. 122.



   The circuit of Figure 8, showing a typical width selector which can be used to advantage, preferably includes a limiter stage 193, serving as an input coupler and limiting all input pulses to virtually no. the same amplitude. If the input pulses are of positive polarity, as indicated at 9a, FIG. 9, the coupler stage 193 also serves to reverse their polarity, as indicated by the pulses of curve 9b. This output pulse energy of stage 193 is applied through a resistor R, to an LC circuit. 195 shock excited. Connected to the terminals of the tuned circuit 195, is a vacuum tube 196, the cathode 197 of which is connected to the input side of the circuit 195 and the anode 198 being connected to the opposite side 199 of the tuned circuit.



  The. side 199 is also connected to an anode voltage source 200.% of the pulse energy, curve 9b, of the anode connection 194 is applied to the grid of the tube 196, so as to block the conduction between the cathode 197, and the The anode 198, when pulse energy is applied to circuit 199. Ripples produced in circuit 199 in response to pulse energy applied by the anode connection are collected by connection 201 and applied to a stage threshold limiter amplifier 202. The polarization of the gate 203 is controlled by adjustment of the resistor 204.

   At the output 205 of the stage 202 is disposed a pulse width shaper 206, the operation of which is described below!

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It will be assumed, by way of example, that the widths of the pulses of curves 9a and 9b correspond, respect! vein different channels W1W2 W3 W4 W5. It will also be assumed that circuit 195 is tuned for the selection of the pulse width W3. Curve 9c represents the output voltage of circuit 195, when this circuit is tuned for selection of pulse width W3. The curve shows the different sor ripples. tie for the different pulse widths of the curve 9b.



  When the leading edge 207 of the pulse W3 is applied to the negative polarity circuit 195, an initial ripple 2D8 is produced; normally followed by ripples 209, 210, etc ... in the form of a damped wave. When the circuit is tuned to a frequency whose period is exactly twice the width w3, trailing edge 211 occurs at the point where the triggered oscillatory energy intersects the zero axis of ripple 208 through ripple 209. As the trailing edge 211 shock excites the circuit in the same direction at this point, the ripple 212 produced in the circuit 195 is added algebraically to the ripple 209 to produce the ripple 213.

   The following pairs of ripples produced by the leading and trailing edges of the pulse width W3 would normally tend to produce a negative ripple 214 which would continue in a damped waveform, retort indicated at 215. However, the damper tube 196 eliminates the oscillations which follow, so that they do not mix with those produced by the following pulses, applied to circuit 195.



   A pulse width less than the. width W3 and such; for example, the widths W1 and W2 will not produce maximum ripples as large as the ripple 213 for the tuning setting corresponding to the pulse width W3. This fact is illustrated by the oscillations 216 and 217 produced in response to the pulse widths W1 and W2. The reason is easily apparent, because the shock excitations produced by the front and rear flanks impulse widths less than W3. oppose

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 partly to each other, as indicated by the broken lines associated with corrugations 216 and 217.

   The ripples 218 and 219 produced in response to the larger pulse widths W4 and W5 are also smaller than the ripple 213, because, here again, the oscillations produced in response to the leading and trailing edges of the larger pulse widths. larger in part oppose each other, so that their algebraic sum is less than in the case of the ripples produced in response to the pulse width W3.



   The threshold limiter stage 202 is set to limit to a level 22, which produces and amplifies the 21µlA peak of ripple 213, as indicated by curve 9b. The pulse shaper 206 is preferably of such a nature that it differentiates the pulse 213a producing the pulse shape 213.B from the curve 9e. The converter also includes the limiter stage for suppressing the positive portion of the pulse shape 213.B at level 221, thereby producing a low width pulse 213.C time synchronized with the pulse width W3. .

   It is evident that by adjusting the tuning of circuit 195 to another frequency whose period is twice the duration of any of the other pulse widths of curve 9b, a corresponding output pulse can be produced, which represents the pulses of the selected pulse width. If two pulses which differ little in width are to pass through the same width discriminator, the limiting level 220 can be adjusted to choose the two ripple peaks, which differ little in amplitude.



   The figure obtained on the screen of the cathode-ray oscilloscope will be of the form shown in Figures 10 and 11. Figure 10 shows the type of figure PLS and Figure 11 refers to the corresponding image 3.PR.



   For the sake of simplicity, the number of characteristics to be indicated has been reduced to a minimum. The geographical conditions are

  <Desc / Clms Page number 46>

 - assumed to be the same as those shown in the images on fig. 1, but it was assumed that the apparatus was set for large-scale reproduction, covering a relatively small radius around the lighthouse. Thus, the great mountain 72 and the three planes 75, 75, 76 in flight outside this radius, are not represented.



   Figure 10 shows only the plane of the observer 71, three other planes 77, 78, 79 part of the hill 73, two active ground repeats 222,223 marking the ends of the runway and eight parasitic repeaters 224, marking the boundaries of said track.



   It will be understood, however, that switching devices allowing the pilot to pass a smaller scale reproduction covering a larger area will be provided.



   The representations of hill 73 and passive repeaters 224 can be ordered separately from those of other objects: airplanes and active repeaters. Thus, if desired, the hill and passive repeaters can be "put on hold" to further highlight active planes and repeaters.



   If desired, repeaters can be illustrated in successive bursts to distinguish them from airplanes, but even without this, airplanes can be distinguished by their movement.



   Lighthouse 68 is represented by the bright crescent-shaped spot in the center of the screen, and the observer's plane 71 is shown as a bright spot at the other end of the dim ellipse of Figure 10. This ellipse represents the blind region mentioned above, which is inherent in the LRS breeding pattern. A semi-luminous ellipse joining the lighthouse and the observer's receiver will ordinarily be observed, although its glow may fade halfway between the two ends. ne Inside this ellipse, the LRS 'principle makes it possible to see no representation of obstacles or airplanes.



   The 3.PR reproduction type, shown in Figure 11, provides a very satisfactory means of eliminating the blind region of the LRS reproduction. As this reproduction 3.PR is essentially analogous to radar retransmission, but with elimination

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   . of the weakest pulses and half-toh effects, its only blind region is the small circular spot normal to the center of the screen representing the position of the beacon 68. All planes 77, 78, 79 seeing outside this central spot are seen clearly, perhaps even with greater finesse than in the typical RLS representation.



   The only major drawback of the 3.PR type representation when it is used alone is that it does not give a positive identification of the observer's aircraft. Thus, a pilot considering only the reproduction of FIG. 11 would not be able to determine in a simple and certain way which of the spots represents it itself. By combining the indications of Figures 10 and 11 on a single screen, the main disadvantages of both types of reproduction are eliminated. In addition, several other important advantages result.



   In the first place, it becomes much easier for the pilot to immediately notice any distortion of the indications of the RLS reproduction, since the two reproductions are superimposed and thus the distortion of one of them results in a very lack of coincidence. apparent. It has been said that one of the main reasons! The choice of the RLS principle as the main navigation aid is that any malfunction in the system necessarily results in reproduction distortion. It would be possible to control such distortion by comparing the reproduction of Figure 10 with a printed map showing the lighthouse, the mountain, the two repeaters on the ground and the passive repeaters bordering the runway.

   (In practice, of course, we would have a much larger number of representations of each of these categories of objects). However, this would require superimposing the map on the screen, to achieve sufficient convenience.



   The two reproductions could be shown alternately, at intervals corresponding to the rotation of the headlight beam (eg, about 50 times per minute); but, in the example

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 Now, it is assumed that these two reproductions are intermixed at the pulse rate of 1,200 frames per second, so that they appear simultaneously present.



   Although only one particular example of a system according to the invention has been described above, it should be understood that many variations are possible in the transmitter and in the receiver, as well as in the apparatus. indicators used, as technicians will realize. In addition, although pulse modulations of different widths have been described in particular, with the aim of distinguishing between them the different signals it is obvious that other characteristics such as amplitude or frequency can be used. Finally, the different transmitting functions, using separate antennas, can be combined on a common antenna, provided with suitable switching arrangements, if such a system is considered more advantageous.


    

Claims (1)

ABSTRACT. The present invention relates to improvements to radio-beaconing systems and in particular to those providing the observer with the reproduction of a formation of planes in the vicinity of said beaconing organization. It provides for the use of the energy of the emitter of a single beacon to produce, for example, on a serial device, the reproduction of a whole system of reflecting objects with their relative position, analogous to the azimuthal radar reproduction. that would be obtained directly at the lighthouse radio station. To remedy the defects of each of the reproduction systems that may be used, the invention provides for the superposition, on the screen of a receiving oscilloscope, of the same indications obtained according to two different systems. The invention further provides, to. as new industrial products, radio-beaconing devices comprising, separately or together <Desc / Clms Page number 49> ¯ combination, the stated improvements.