281525/ Method for protecting a vehicle by an identification as a friend or foe The invention relates to a method for protecting a vehicle by an identification as a friend or foe, in which an aerial vehicle with a tracking system, which includes a tracking sensor and a control unit, engages the vehicle in an attack. In military conflicts, there is the danger of so-called “friendly fire”, in which an aerial vehicle mistakenly classifies a friendly vehicle as hostile and fires on it. In order to avoid such accidents, it is known that a mistakenly attacked vehicle emits a radio identification as a friend, which is received by a fire control radar controlling the attacking aerial vehicle, the fire control radar detects the identification as a friend as such, identifies the vehicle as friendly and aborts the attack. An object of the invention is to provide a quickly acting method for protecting a vehicle by an identification as a friend or foe. This object is achieved by a method of the type mentioned at the beginning in which, according to the invention, the aerial vehicle detects an emitter launched by the vehicle as a flying object which is separate from the vehicle and receives from it the signal with the identification as a friend, detects the identification as a friend as such and, on the basis of the detection, aborts the attack. The fact that the attacking aerial vehicle already detects the identification as a friend as such means that an attack can be aborted very quickly. For example, an attack that is already at a very advanced stage can still be aborted shortly before the triggering of an explosive charge. Protection by means of identification as a friend or foe is implemented to the extent that the vehicle previously classified as a foe by the aerial vehicle is then reclassified as a friend on the basis of the identification as a friend being identified, so that the attack can be aborted. The aerial vehicle receives the friend signal, i.e. the signal with the identification as a friend, from the emitter launched by the vehicle. That is to say that the launched emitter emits the signal with the identification as a friend. The emitter may be a radar emitter or an IR emitter, for example a decoy, such as a flare.
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This idea is based on the consideration that the emission of a friend signal should be well disguised, since otherwise an enemy vehicle could during battle receive the friend signal of another vehicle and make it its own. If the enemy vehicle is then attacked, it can deceive the attacker by emitting the misappropriated friend signal and successfully defend itself against the in fact correct attack. To avoid this, it is advantageous if the friend signal is sent in the same way as a defensive measure of a vehicle against an attack is usually sent. A customary defensive measure against an attacking aerial vehicle is the launching of decoys. A decoy emits radiation by means of which a seeker head of the attacking aerial vehicle is jammed. For example, an IR seeker head is deceived by a launched decoy in the form of flares. The interference signal is encountered in the evaluation of the tracking sensor by the control unit of the aerial vehicle and makes it more difficult or possibly prevents a correct evaluation that would enable a successful attack to be still possible. If the identification as friend is hidden in such a defensive signal, it is perceived by observing third parties as a customary defensive measure, without the friend signal within the defensive measure being detected. A launched emitter may be a decoy, that is to say such an element launched by the vehicle which emits radiation which is at least similar to deception radiation which is emitted to deceive an attacking aerial vehicle. A launched emitter for emitting the friend signal may in any case be understood as a decoy if it is launched together with multiple other decoys and in particular behaves in a similar manner to the decoys. The emitter may be a flare, that is to say a pyrotechnic element, or a radar body which actively emits radar radiation or passively reflects radar radiation. The vehicle may be a ground vehicle, such as a radar vehicle or a tracked vehicle. It may however also be a water craft or an aircraft. An identification as a friend or foe may be understood in a military sense, in which a distinction is drawn between a friend and a foe, with the intention of firing on a foe and not firing on a friend. An identification takes place when an object previously classified as a foe is identified as a friend. The aerial vehicle may be a manned or unmanned aircraft, a rocket, a guided missile, guided bomb or some other device that can be guided through the air. A tracking system may be a system designed for acquiring and tracking a target, for example a vehicle. It may be sensitive in the spectral range of infrared, visible radiation or radar radiation, that is to say use radiation from one or more of the spectral ranges
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mentioned in order to detect and track the target. A tracking sensor may be a sensor that is sensitive in at least one such spectral range, expediently an imaging sensor. The tracking system includes a control unit, which in particular evaluates data of the tracking sensor and carries out a tracking, that is to say tracking of a target. An attack may be regarded as aborted if an action on the part of the aerial vehicle is executed in such a way that the vehicle is no longer attacked, for example the aerial vehicle is guided in such a way that it no longer engages the vehicle. Or the aerial vehicle destroys itself before it reaches the vehicle. In order that the aerial vehicle can engage the vehicle, it is expedient if the aerial vehicle acquires the vehicle with the tracking sensor, that is to say detects it as a target. Tracking may be performed by electronic tracking of a signature of the vehicle, for example an IR signature or a radar reflection, in particular by multiple images depicting the vehicle. The aerial vehicle may track the vehicle in particular on the basis of data of the tracking sensor. This may involve the aerial vehicle making the direction of its flight follow movements of the vehicle, that is to say the direction of flight is influenced by movements of the vehicle. The control unit of the aerial vehicle may detect the identification as a friend of the vehicle as such from the data of the tracking sensor or some other sensor. For this, the identification as a friend expediently contains a code that is stored in the aerial vehicle as identification as a friend and on the basis of which the control unit can detect the identification as a friend as such. The aerial vehicle can to this extent evaluate the identification as a friend and classify the vehicle as a friend. Dependent on the detection, the aerial vehicle may abort an attack on the vehicle that has already been initiated. Depending on the type of sensor channel, the identification as a friend may be for example an IR signal or a radar signal. In the case of an IR signal, a friend emitter may be a decoy in the form of a flare. In the case of a launched emitter, on the receiver side there are two possibilities: The aerial vehicle receives the identification as a friend from the launched emitter and has also detected that a flying object which is separate from the vehicle exists, but it does not distinguish whether it comes directly from the vehicle or from the launched emitter. This action is sufficient to protect the vehicle. And the presence of the separate flying
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object can already be taken as an indication that the identification as a friend has been emitted by the separate flying object so that the identification as a friend – implicitly – originates from the vehicle under attack and thus is taken seriously by the attacking aerial vehicle. Or the attacking aerial vehicle directly detects the identification as a friend as emitted by an emitter that the vehicle has launched. If for example a flare emits the identification as a friend, the aerial vehicle detects the flare as a further flying object that is emitting IR radiation. So if the aerial vehicle can detect from which of the two or more objects the identification as a friend comes, it can for example engage the flare emitting the identification as a friend instead of the vehicle, so that the vehicle is protected. The same also applies to other decoys, for example a radar body. It is to this extent advantageous if, in addition to the vehicle, the aerial vehicle tracks a further flying object that emits the signal with the identification as a friend, and in particular, in order to protect the vehicle, after detecting the identification as a friend, engages the further flying object instead of the vehicle. In general, in an advantageous embodiment of the invention, to this extent the aerial vehicle detects the identification as a friend as having been emitted by a launched emitter and also uses this information to determine the identification as a friend. In order to achieve good disguise of the identification as a friend, it is advantageous if the signal with the identification as a friend is emitted in a frequency range in which defensive measures against an attack usually take place. Since such measures are usually directed against the activity of the tracking sensor, it is to this extent advantageous if the signal with the identification as a friend is emitted in a frequency range in which the tracking sensor of the aerial vehicle is sensitive. By analogy, it is advantageous on the receiver side if the signal with the identification as a friend is received in a frequency range in which the tracking sensor of the aerial vehicle is sensitive. This frequency range is referred to hereinafter as the sensor channel. The evaluation of an identification as a friend in the sensor channel can take place in a number of ways. If the tracking sensor is a highly specialized sensor, it may be advantageous to receive the identification as a friend by another friend sensor. If for example the tracking sensor integrates over a wide frequency range, to be able even to track down very sensitively vehicles that are far away, it may be difficult to resolve an
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identification as a friend with a sharp frequency peak by the tracking sensor. Although the identification as a friend is in the sensor channel, and is therefore also received by the tracking sensor, it is not resolved sufficiently reliably by it. A sensor especially tuned to the frequency of the friend signal will however reliably resolve the identification as a friend, so that the control unit can identify it as such. In other words, it is possible that the aerial vehicle has in addition to the tracking sensor a friend sensor, which is prepared for receiving the identification as a friend. The tracking signal, that is to say the IR or radar radiation of the vehicle signature, and the identification as a friend, that is to say the signal with the code that describes the vehicle as a friend of the aerial vehicle, can therefore be received and processed by different sensors. Such a configuration can have the advantage that a tracking evaluation of the data of the tracking sensor is not influenced or even restricted by an evaluation of the friend signal. In a second case, only a part of the overall frequency spectrum of the tracking sensor, that is to say the sensor channel, is used for the tracking of the vehicle. For example, a spectral filter filters out a narrow frequency range, which is used for the identification as a friend or foe. The remaining range can be used for the tracking. The sensor channel is therefore divided into a friend channel, in which the identification as a friend is sought, and a tracking channel, which is used for the tracking. In other words: the frequency range in which the tracking sensor is sensitive may be relatively wide, in particular in the case of an infrared sensor (IR sensor) for detecting an IR signature, in order to obtain a high spatial resolution by integration over a wide frequency range. By contrast, it may be sufficient to send the identification as a friend over a much narrower band. In the case of a narrow-band identification as a friend, there is the possibility of setting the friend channel, that is to say the frequency range in which the identification as a friend is sent, along with the tracking channel, that is to say the frequency range that is used for the tracking, with or without an overlap of the two channels. By means of channel separation, for example by a beam splitter or filter, the two channels can be separated and evaluated separately. In a third case, the tracking channel and the friend channel overlap. For example, the friend channel lies completely in the tracking channel. With the evaluation of the signals of the tracking sensor by the control unit for the purpose of tracking, the friend signal can also be identified. The signal with the identification as a friend may be received in
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the frequency range that is used for the tracking of the vehicle. To this extent, the friend channel and the tracking channel lie one over the other or one within the other. In this way it is possible to dispense with channel division, and the detection of the identification as a friend can be performed from the same data that are used for the tracking. It is possible in the second and third cases to dispense with an additional friend sensor because the signal is received by the tracking sensor. In the third case, this involves the control unit detecting the identification as a friend as such from the data of the tracking sensor. An identification as a friend can in this way be achieved in a simple form, without sensory modifications having to be carried out on the aerial vehicle. All three possibilities are meaningful and advantageous to the extent that the signal with the identification as a friend is sent and received in a frequency range in which the tracking sensor of the aerial vehicle is sensitive, that is to say usually interfering measures also take place, so that as a result the friend signal remains disguised. If a vehicle launches decoys, this generally takes place by multiple decoys being launched in quick succession shortly before the attacker strikes. These decoys usually radiate with a similar signature to that with which the vehicle also radiates. One or more launch parameters may be used as coding parameters for the identification as a friend. Or taken from the receiver side: at least one launch parameter of multiple emitters may be investigated as a coding parameter for determining the identification as a friend. The following may be used as launch parameters: the number of emitters launched, a launch sequence of the emitters launched, that is to say time intervals between the individual launches, launching directions of the emitters launched and/or launching speeds of the emitters launched, that is to say how far they fly away from the vehicle in a certain time. For example, if the launch sequence is used as launch parameter, the aerial vehicle can determine the identification as a friend from a launch sequence in which multiple emitters are launched by the vehicle, or can determine the launch sequence at least as part of the identification as a friend. Protecting a vehicle by an identification as a friend or foe can be described in an equivalent way from the sender side and the receiver side, from the sender side by the emission of the identification as a friend and from the receiver side as the detection of the identification as a friend. While the invention has so far referred predominantly to
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the detection on the receiver side, the invention is described hereinafter from the sender side. An object of the invention is to provide a quickly acting method for protecting a vehicle by an identification as a friend or foe. This object is achieved by a method for protecting a vehicle by an identification as a friend or foe, in which the vehicle classifies an aerial vehicle as an aerial vehicle attacking the vehicle and emits a signal with an identification as a friend. It is proposed that, according to the invention, the vehicle launches an emitter as a flying object and, after its launch, the emitter sends the signal with the identification as a friend. The identification as a friend can be received and detected directly by the aerial vehicle, and the attack can be aborted very quickly. The vehicle is expediently provided with a trigger to emit the signal with the identification as a friend. A trigger may be the classification of the aerial vehicle as an attacking aerial vehicle. This may take place automatically or manually, initiated by an operator, who for example instigates the emission of the identification as a friend. A classification as an attacking aerial vehicle may take place by the detection of a tracking operation. The aerial vehicle may engage the vehicle on the basis of data of the tracking sensor. This may involve the aerial vehicle making the direction of its flight follow movements of the vehicle, that is to say the direction of flight is influenced by movements of the vehicle. This can be detected by the vehicle and used as a trigger for sending the identification as a friend. It is likewise possible that the aerial vehicle actively directs a beam at the vehicle, for example a radar radiation beam, and the vehicle detects from the reception of the active radiation that it is being tracked and takes this as a reason for sending the identification as a friend. It is likewise possible that the vehicle detects a launching flash of a rocket motor and takes this is a classification of being tracked by an attacking aerial vehicle, to emit the identification as a friend. Aerial vehicles designed for destroying a vehicle may be understood as taking the form of aerial vehicles with a submunition, that is to say an explosive charge for destroying the vehicle, and or aerial vehicles that are prepared for colliding with the vehicle to destroy it. The launched emitter can be a decoy, with this being meaningful for reasons of disguise. A decoy can be a body which emits in such a way that its IR signature can be confused for that of a vehicle engine or its radar signature can be confused with that of a vehicle. The decoy may be a pyrotechnic body of which the radiation from its burn up
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contains the friend signal. It is likewise advantageous for the sake of good disguise if the emitter is launched together with multiple decoys that radiate at a frequency at which a seeker head of the aerial vehicle is sensitive. The identification as a friend may be generated by only one of a plurality of decoys. This allows the identification as a friend to be disguised particularly well. It is to this extent advantageous if the vehicle launches multiple different decoys, the decoys burn up different substances and only some of the decoys, in particular only a single decoy, thereby emit(s) radiation of which the radiation frequencies are part of the friend signal. It is also possible that – as already described at the beginning from the receiver side – the vehicle launches multiple emitters, it being possible for a launch parameter, such as their launch sequence, and/or illuminating frequencies to be part of the friend signal. It is however also possible that a single emitter launches multiple emitting bodies. For example, one of a plurality of flares break(s) up into multiple parts, which each independently emit. A flare may for example launch multiple elements, for example discs. Here, too, one or more launch parameters may contribute to the coding of the identification as a friend. But also different radiation frequencies may be at least part of a coding as a friend. Thus, each element may radiate at one or more frequencies that are separate from one another, the frequencies being in their specific composition at least part of the coding as a friend. If an emitter or multiple emitting elements is/are launched, either by the vehicle and/or by a launched emitter, one or more of the following parameters may be part of the coding as a friend, that is to say the code that makes up the identification as a friend as such. Emitting elements may be burning-up elements that radiate in the infrared and/or visual spectral range. Amplitude: multiple emitting elements radiate at the same time or at different times from one another with different intensities. Or only one emitter radiates so variably in its intensity over time that the intensity increases and decreases at least twice over a predetermined course of time. There is to this extent a modulation of the burning-up brightness in multiple different maxima and minima, the differentness of which is part of the friend signal. Number: a predetermined number of emitting elements is launched.
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Launch sequence: multiple emitters or emitting elements are launched and/or ignited in a fixed time sequence, so that the beginning of their radiation takes place in this sequence. The time intervals between launches or ignitions are expediently different. If the emitters or emitting elements have different radiating frequencies, the sequence of the launch or the ignition can therefore be fixed. Pulse width: multiple emitters or emitting elements radiate in pulses of different widths in terms of time. Radiating frequencies: multiple chemical elements or compounds of an emitter radiate sharp spectral lines, in particular in the visual and/or near infrared range. The substances may be admixed into the main explosive compound of a decoy, so that the decoy has in addition to its regular radiation characteristic a line characteristic, which is at least part of the identification as a friend. For example, lithium, sodium, potassium, rubidium, caesium, calcium, strontium, barium, thallium, indium, copper, zinc, lead, bismuth, selenium, boron, mercury, yttrium and/or some other rare earth metals may be admixed individually or as a compound into the explosive compound. In an advantageous embodiment of the invention, the signal with the identification as a friend is an amplitude-modulated IR signal, from the amplitude modulation of which the identification as a friend is detected as such. The signal can to this extent be detected from a predefined amplitude fluctuation, for example from a sequence of flashes of light, expediently within a disguising background signal, where in this connection the infrared range is also referred to as “light”. For example, the friend signal is modulated onto an interfering laser beam, so that it increases and decreases in its intensity in a predefined manner. A further possibility is that the signal with the identification as a friend is a frequency-modulated IR signal, from the frequency modulation of which the identification as a friend is detected as such. To keep with the example of the interfering laser or IR jammer, a colour code may be modulated onto the interference beam, for example a beam of constant amplitude but changing colour or frequency. The change of frequency may comprise the friend signal, which is consequently clearly detectable. Amplitude and frequency modulation can of course also be used together. However, the friend signal does not have to be modulated on a time basis, as described in the two cases above. It is also possible that the identification as a friend
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comprises a predefined compilation of frequency ranges. Such a predefined spectral compilation may include the identification as a friend independently of a temporal modulation. For example, IR radiation contains multiple sharp spectral peaks, the compilation of which – and possibly also amplitude in relation to another – at least partly include the identification as a friend. The evaluation of the individual frequency ranges can take place with the aid of at least one frequency filter, for example a spectral filter in the IR range and/or visual range. The tracking system may evaluate these frequency ranges individually – in particular separately from the tracking channel – where this can be understood as meaning a spectral resolution of the individual ranges. Advantageously, in the case of at least one of the parameters amplitude, launch sequence and pulse width, the modulation frequency is so high that the amplitude modulation of the burn-up remains hidden to a human eye. Frequencies higher than Hz, in particular higher than 50 Hz, are advantageous. Instead of launching an emitter radiating in the infrared and/or visual spectral range, a radar emitter that emits the signal with the identification as a friend may be launched. The emitter may be an active emitter, which is fed from an energy source and sends radar beams, or a passive emitter, which reflects received radar radiation in an unchanged or changed state as a response signal. In the case of a passive radar emitter, the identification as a friend may be achieved by the radar emitter reflecting tracking radiation of the aerial vehicle and thereby absorbing at least one radiation band within the frequency range of the tracking radiation. The absorption may be part of the friend signal or be the friend signal. A further possibility is that the radar emitter absorbs tracking radiation of the aerial vehicle and radiates it in a frequency-shifted form in the direction of the aerial vehicle. The frequency shift may in this case be part of the friend signal or be the friend signal. A temporal modulation of the radar response signal also comes into consideration as a possibility for identification as a friend. In this case, the radar emitter may absorb tracking radiation of the aerial vehicle – or in the case of an active emitter receive it – and radiate it in a time-shifted manner in the direction of the aerial vehicle. The time shift may be part of the friend signal or be the friend signal.
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All of these details can be carried out by a radar emitter from the vehicle or by one or more radar emitters that are launched by the vehicle. Even if radar emitters are launched and these emit the identification as a friend, this is understood as the identification as a friend being sent by the vehicle. In the case of active radar coding, it is advantageous if the vehicle uses incident radar radiation as a trigger for actively sending the identification as a friend. If the vehicle launches multiple radar emitters, it is advantageous if the pulsed tracking radiation incident on the radar emitters synchronizes active emitting units of the multiple launched radar emitters. Each emitter may for example have at least one emitting unit. The multiple emitting units are synchronized by the incident radiation. In order to make it more difficult to misappropriate the identification as a friend, it is advantageous if it can be changed. When an identification as a friend has been used, the same or other vehicles may be provided with one or more other identifications as a friend. On the receiver side, it is advantageous if the identification as a friend that is accepted is likewise changed, so that an obsolete identification as a friend is no longer accepted as such and no longer leads to the attack being aborted. It is simplest if the identification as a friend is programmable on the sender side and/or the receiver side. Programming may comprise changing software information that is processed by an identifying program. It may however also comprise changing mechanical elements, such as changing a transmitting antenna for radar radiation or providing pyrotechnic elements. In this way, an identification as a friend can be changed from an earlier, different identification as a friend to the current identification as a friend. This takes place before the emission of the identification as a friend, so that only the current identification as a friend is emitted. In the case of a pyrotechnic or radar emitter, the change can be made on the sender side, by a container, for example a canister, with at least one decoy being opened and the decoy replaced by another decoy with the current identification as a friend. For instance, a flare container may be provided with one or more different flares. Providing radar reflector containers with different reflectors or a different radar flare cartridge is also possible and meaningful.
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In the case of an electronic ignition unit, which ignites one or more pyrotechnic elements, it is advantageous if the change is made by an ignition unit being reprogrammed. If for example multiple emitters or emitting elements have different radiating frequencies, the sequence of the launch or the ignition can be changed. As a result, a new colour coding can be created. Changing a launch sequence is also advantageous. If reprogramming is not possible or desired, an igniter may be exchanged. For example, by changing a decoy igniter, a different ignition procedure, such as a different ignition sequence or different times between multiple ignitions, may be set. A radar emitter may of course also be changed by reprogramming or making a mechanical change. For instance, a change may be made by a radar circuit being reprogrammed. Or a change is made by a geometry of a radar reflector being changed, whereby its radiating frequency changes. The invention also relates to an aerial vehicle with a tracking system, including a tracking sensor and a control unit for tracking a vehicle to be attacked, a system of fins for aerial engagement of the vehicle and a submunition for destroying the vehicle. To make it possible for an attack to be quickly aborted when an identification as a friend is detected, it is proposed that the control unit is prepared for detecting an emitter launched by the vehicle as a flying object which is separate from the vehicle and for detecting a signal received from it as an identification as a friend. The identification as a friend may be exchanged directly between the vehicle and the aerial vehicle, so that the attack can be aborted very quickly. For receiving the identification as a friend, the tracking system may use the tracking sensor or an additional sensor, which is expediently also sensitive in the frequency range in which the tracking sensor is sensitive. The aerial vehicle may receive a signal with an identification as a friend, detect the identification as a friend as such and abort the attack on the basis of the detection. In this case, the signal with the identification as a friend may be received in a frequency range in which the tracking sensor of the aerial vehicle is sensitive. In order to achieve a reliable detection of the identification as a friend, it is advantageous if the tracking system has a frequency analyser, which is designed for
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detecting radiation frequencies. The detection may comprise filtering out of the frequencies. The control unit is thus advantageously prepared for detecting the friend signal from these radiation frequencies. The tracking channel may be different from the friend channel. For a tracking, the aerial vehicle may include an optical system for guiding incident ambient radiation onto the tracking sensor and a frequency filter, for example a beam splitter, which is prepared for splitting the radiation from the optical system to the tracking sensor on the one hand and to an identification-as-a friend sensor on the other hand, the control unit evaluating the identification-as-a friend sensor for detecting the friend signal. On the sender side, the invention is directed to an emitting system with an emitter, comprising a signal radiating unit and a coding unit, which is prepared for impressing an identification as a friend on a signal, and comprising a container for holding the emitter. The emitter may be launched from the container, so that it is possible for the emitter to be disguised as a decoy. In order to make it possible for an attack to be aborted quickly, it is proposed that the container is a launching container having a launching unit which is prepared for launching the emitter during travel into an environment of a bearing vehicle. Depending on the design, the emitter may be a pyrotechnic body or radar emitter. It may have an energy supply unit in the form of a pyrotechnic body or a battery. The signal radiating unit may be a pyrotechnic body or an antenna. The coding unit may comprise the composition of a pyrotechnic body or a launching unit or a circuit. The container may be a launching container. It is evident from this design that, in particular in the case of an IR decoy, the emitter has a pyrotechnic unit, which forms the signal radiating unit and the coding unit in one unit. Burning up of the pyrotechnic body, that is to say the pyrotechnic unit, generates a friend signal with the corresponding coding. Advantageously, the container has a launching unit, which is prepared for launching the emitter from the container. It is also advantageous if the emitter has a burning-up unit with a composition which, when it burns up, emits an amplitude-modulated and/or frequency-modulated IR signal
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that forms the friend signal. The burning-up unit may be part of a pyrotechnic unit, for example a flare. Easy reprogramming of the identification as a friend can be achieved if the container has multiple pyrotechnic emitting units with in each case an electronic igniter, which respectively set the timing for their pyrotechnic unit. The timing is expediently an ignition time after launching. Advantageously, the timings are at least part of the coding of the friend signal. In order to achieve a good disguise, it is also proposed that the container encloses multiple further decoys together with the emitter. In the case of a radar system, the container may enclose a multiplicity of radar reflectors. The emitter may have an electronic circuit, which controls the coding of the identification as a friend. The description given so far of advantageous refinements of the invention includes numerous features that are partly grouped together in a number of dependent claims. However, the features may expediently also be considered individually and combined into meaningful further combinations, especially where claims have dependency references, and therefore a single feature of a dependent claim can be combined with a single feature, several features or all the features of another dependent claim. Moreover, these features can each be combined individually and in any suitable combination both with the sender-side method according to the invention and with the receiver-side method according to the invention as well as with the devices according to the invention in accordance with the independent claims. Thus, sender-side method features can also be seen as characteristics of the corresponding receiver-side method, and vice versa. Furthermore, method features may also be also be regarded as worded in substantive terms as characteristics of the corresponding device unit, and functional device features as corresponding method features. The characteristics, features and advantages of this invention described above and the manner in which they are achieved will be more clearly and distinctly comprehensible in conjunction with the following description of the exemplary embodiments, which are explained in greater detail in conjunction with the drawings. The exemplary embodiments are used to explain the invention and do not restrict the invention to the
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combination of features, including functional features, that is specified therein. For this purpose, it is furthermore also possible for suitable features of each exemplary embodiment to be considered explicitly in isolation, removed from one exemplary embodiment, introduced into another exemplary embodiment in order to supplement the latter and/or combined with any one of the claims. In the drawings: FIG 1 shows an aircraft that is being attacked by a guided missile and has launched decoys for its protection, FIG 2 shows a container which has launched six, to some extent different decoys, FIG 3 shows a container which has launched a series of decoys, one of which has a different radiation characteristic than the others, FIG 4 shows a container which has launched a series of decoys, one of which has launched multiple emitting elements, FIG 5 shows a container in which an emitting element has been exchanged, and FIG 6 shows a container which has launched a multiplicity of radar reflectors, some of which are provided with passive radar modifiers. FIG 1 shows a vehicle 2 in the form of an aircraft, which during its flight is attacked by an aerial vehicle 4 in the form of a guided missile. Instead of an aircraft, the vehicle may also be a wheeled or tracked vehicle or a watercraft that is attacked. In the exemplary embodiment shown, the vehicle 2 has for example just taken off from an airport close to a metropolis and, because of a tense situation, has been wrongly classified by air surveillance radar as an attacking aircraft that represents a threat to the metropolis. A command centre has launched the guided missile, which has been guided to the aircraft by air control radar. Once it has come within a certain range, a seeker head of the aerial vehicle 4 has locked onto the vehicle 2 and a control unit of the aerial vehicle 4 has tracked an infrared imaging of the vehicle 2 on the basis of data of the seeker head, so that the aerial vehicle 4, guided by a system of fins 5, then pursues the vehicle 2 of its own accord until an explosive charge of its submunition 7 is detonated directly alongside the vehicle 2. Because of a mistaken assessment of the
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situation by the command centre, there is an imminent risk of a disaster involving the shooting down of a large-capacity aircraft by a friendly guided missile. The command centre is still unaware that a mistake has been made. About five seconds before impact, a monitoring unit of the vehicle 2 detected the incoming aerial vehicle 4 as a threat, in that it classified the aerial vehicle 4 as attacking, and began to emit a radio identification as a friend. About two seconds later, the identification as a friend is identified as such by the fire control radar and is passed on as a warning to the command centre. At the same time, the fire control radar checks the origin of the identification as a friend, in order to establish without doubt that it originates from the vehicle 2 being attacked and not from a unit interfering with the attack. Only when the identification as a friend of the vehicle 2 has been clearly identified is the fire control radar authorized to abort the attack of its own accord. This operation takes approximately five seconds, so that it takes too long to protect the vehicle 2. At the command centre, the warning is correctly assessed by an operator approximately three seconds after arrival, but the operator needs quite a long time to issue orders to abort the attack. This operation also takes too long to save the vehicle 2. At the same time as the identification as a friend was sent by radio, the vehicle 2 launched multiple emitters 6 in the form of pyrotechnic decoys. The decoys are burning flares. Other burning-up emitters 6 are also possible. Altogether, six emitters 6 were launched at respective intervals of 0.2 seconds and ignited on launching, although any other number of emitters 6 may also be launched in other sequences. The emitters need a few tenths of a second for their radiation to become fully functional, so that in the situation represented in FIG 1, for example, three seconds before impact the first four emitters 6 are already fully illuminating, while the last two are still building up their radiation. One of the emitters 6a differs from the other emitters 6. In the following text, the reference numeral 6 has been allocated to all of the emitters, and specific emitters 6a, 6b, and so on, have been provided with appended reference letters. If only the reference numeral 6 is given, the designation applies to all of the emitters 6, 6a, 6b, and so on, unless the description indicates otherwise, for example by stating “the other emitters 6”.
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The emitter 6a is provided with a pyrotechnic charge, which although essentially identical to the other emitters 6, has had lithium, potassium and yttrium compounds admixed with it. The radiation spectrum of this emitter 6a therefore contains a multiplicity of characteristic radiation curves in the range between 250 nm and 12nm, which the other emitters 6 do not emit. This is indicated in FIG 1 by longer radiation lines of the emitter 6a, which is intended to show the signal 12 that contains the identification as a friend. The difference in the spectra of the emitters 6, 6a is not visible to the human eye, since they all burn up with the same brightness and on average the same colour. The spectral differences of the emitters 6 are also not detectable for a customary seeker head. The spectral lines do lie in the sensor channel, that is to say in that spectral range in which the tracking sensor of the aerial vehicle 4 is sensitive. Nevertheless, since customary tracking sensors integrate over largely the entire sensed part of the infrared spectrum and cannot spectrally resolve, the radiation anomaly of the emitter 6 remains hidden from the tracking sensor. In customary use, the emitter 6a therefore may not be noticed. Since it also does not differ outwardly from the other emitters 6, under normal circumstances its presence remains undetected. However, the aerial vehicle 4 is provided in its seeker head with a tracking system 8, which has in the optical path of the seeker-head optical system a beam splitter, which diverts part of the spectrum focused by the optical system, a friend channel, onto a separate detector, which is prepared for the spectral resolution of the friend channel. There, the spectrum is examined for a number of predefined lines. If these spectral lines are detected, their intensity is compared with the average intensity of the overall spectrum. If the line intensity exceeds a predetermined quotient, the identification as a friend that consists of these spectral lines is considered to be detected. This detection takes place approximately 2.5 seconds before impact. The control unit 10, which has performed the evaluation of the spectrum, gives the command to abort the attack. For example, the emitter 6a is flown to and, when it is reached, flying continues straight ahead for a predetermined time period, for example four seconds, before the submunition of the aerial vehicle 4 is ignited, and it is therefore detonated outside the danger zone for the vehicle 2. Or the submunition is ignited when the emitter 6a is reached or already immediately after detection of the identification as a friend. The vehicle 2 has in this way survived the attack undamaged.
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An alternative emission of a signal 12 with an identification as a friend is represented in FIG 1. For this, the vehicle is provided with a built-in emitter, in the exemplary embodiment shown with an interfering laser 14. This radiates interfering IR radiation onto the incoming aerial vehicle 4 after detecting the aerial vehicle 4 as an attacking aerial vehicle 4, in order in this way to jam the seeker head of the aerial vehicle 4, so that the tracking of the vehicle 2 by the tracking system 8 is interrupted. In addition to the customary interfering component, the laser radiation emitted also contains a signal component, onto which an identification as a friend is modulated. This is indicated in FIG 1 by the interrupted line of the signal 12, which is intended to represent the identification as a friend. For example, radiation in the frequency range in which tracking sensors of such aerial vehicles 4 that are designed for destroying a vehicle are sensitive is emitted with the identification as a friend. Under some circumstances, its frequency range does not differ from that of the interfering radiation, but the modulation creates the difference. For example, the interfering signal 12 is amplitude-modulated, that is to say contains signal parts of different amplitudes. Or the signal 12 is pulse-width-modulated, that is to say contains radiation pulses of different widths in terms of time. Or the signal 12 is frequency-modulated and contains spectral lines, the frequencies of which together produce the identification as a friend. On the receiver side, the detection of the friend signal 12 can take place as described above. Or the identification as a friend is sensed by the tracking sensor, which can resolve the amplitude or pulse-width modulation and pass it on as data to the detecting control unit 10. For example, the emission beam “flashes” in a specified way, which, seen superficially, does not differ from the way in which a customary interfering laser “flashes”. It is possible to dispense with a spectral filter, for example a beam splitter. Keeping with the representation from FIG 1, the emitter 6a may also emit an identification as a friend in a way different from that described. For example, the pyrotechnic charge of the emitter 6a does not contain any substances that are spectrally different than those of the other emitters 6. It may, however, exhibit a different burning-up behaviour, which contains the identification as a friend in one or more burn-up parameters. For example, the emitter 6a radiates in multiple pulses with the parameters pulse amplitudes – that is to say brightnesses, pulse widths, intervals between the individual pulses and number of pulses. One of the parameters or a combination of the parameters may form the identification as a friend. On the receiver side, the friend signal can be received in the tracking channel, since its spectrum does not have to differ from that of the other emitters 6.
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To satisfy the generality of the invention, it should be mentioned that it is also possible to launch only the friend emitter 6a instead of the multiple emitters 6 or, in the case of the interfering laser 14, to dispense with interfering radiation and to emit only the identification as a friend. This does not stop the identification as a friend being detected by the aerial vehicle 4, since interfering signals 12 provided at the same time by a built-in or launched emitter 6 serve essentially for the obfuscation of the emission of the identification as a friend and do not necessarily contribute to the detection of the friend signal. FIG 2 shows a further exemplary embodiment, which in large parts is the same as that from FIG 1. The following description is essentially confined to the differences with respect to the exemplary embodiment from FIG 1, to which reference is made in relation to features and functions which remain the same. In order to avoid having to repeat what has already been described, all the features of a preceding exemplary embodiment are generally adopted in the respective following exemplary embodiment, without being described again, unless features are described as differences with respect to one or more preceding exemplary embodiments. Shown in FIG 2 is a container 16, which is fitted in the vehicle 2 or mounted therein. This may also be the case in the example from FIG 1. The container 16 contains a launching unit 17 (only shown schematically), which after receiving a control command, for example from a monitoring unit, launches one or more emitters 6. The identification as a friend may be contained in a launch sequence of the emitters 6. For example, multiple, in particular identical emitters 6 are launched in a predetermined time sequence and thereby ignited. The identification as a friend can thus be determined from a temporal ignition sequence of the emitters and also from a spatial interval between the emitters 6, provided that they are all launched from the container with the same momentum. In the case of the example from FIG 2, between the first two emitters 6 there is a small temporal or spatial interval, then followed by a moderate interval, then a large interval, then a small interval and then again a moderate interval. These intervals, that is to say temporal ignition intervals or spatial intervals, can contain the identification as a friend. It is likewise possible that one or more of the emitters 6 differ(s) from the others. In the case of the example from FIG 2, the two emitters 6b and 6c differ from the other
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emitters 6 in that they radiate more brightly (emitters 6c) or radiate less brightly (emitters 6b), which is indicated in FIG 2 by the radiation lines of different lengths in the case of the emitters 6, 6b, 6c. The identification as a friend may in this case consist not only of the different brightnesses as such, but also of the sequence of the brightnesses, here moderate – bright – moderate – moderate – dark – moderate. To detect a differentness of the emitters 6, it is necessary that the aerial vehicle 4 or its control unit 10 can distinguish the individual emitters 6 from one another and can individually resolve their radiation characteristics. Since the tracking system 8 is designed to track an infrared source and is also capable of tracking multiple infrared sources individually, individual sources can be evaluated for their radiation parameters. That is to say that the parameter values or profiles can be assigned to the individual sources. In the case of the example from FIG 2, the control unit 10 therefore detects six different sources and their different radiation intensity as well as their arrangement in space and also their ignition times. The identification as a friend can be composed of these parameters in any desired combination. The ignition of the emitters 6 may take place on launching or be controlled by igniters, expediently each launched emitter 6 having an igniter of its own, at least the friend emitter or emitters 6b, 6c. In this way, the ignition of the emitters 6 can be controlled individually and independently of launching, whereby a further parameter is made possible as part of the identification as a friend, to be specific a temporal ignition sequence. In the case of the exemplary embodiment from FIG 3, once again a number of emitters 6 have been launched by the launching unit 17 of the container 16, which is designed as in FIG 2. One of these differs from the others in that it contains at least one substance that burns up in a fluctuating manner over time. This produces a fluctuation in the brightness of the burn-up of the emitter 6d. The substance may also be different from the remaining burning-up substance insofar as its radiation spectrum differs from that of the remaining substance. While for example the basic substance burns up uniformly, the brightness of the signalling substance fluctuates. If the two spectra are analysed separately in the tracking system 8, the fluctuation of the signal can be detected as an identification as a friend. In the case of the example from FIG 3, the emitter 6d contains two signalling substances, which are composed in relation to one another in such a way that they
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radiate in an alternating fluctuating manner. When one of the signalling substances is radiating brightly, the other is radiating darkly, and vice versa. In FIG 3, the radiation profiles 18 of the radiation intensities of the two signalling substances over time are represented in a diagram by means of a dashed line (signalling substance 1) and a dotted line (signalling substance 2). The alternating fluctuation of the radiation intensities can be seen. This combination of two different spectra, in particular with alternating fluctuation, that is to say changing amplitude, forms here the identification as a friend. Since the added radiation intensity on average follows an essentially continuous profile, the fluctuation is not visible to an observer, for example a seeker head, that does not consider the spectra separately. A further exemplary embodiment with multiple pyrotechnic emitters 6 is represented in FIG 4. An emitter 6e contains multiple emitting elements 20, which are launched from a container 22 of the emitter 6e. When they are launched from the container 22, the emitting elements 20 are ignited and respectively burn up individually. Each of the emitting elements 20 has an individual burning-up spectrum as a result of its composition of the burning-up substance, so that the emitter 6e in the case of the example from FIG 4 radiates with three different signal spectra in addition to the basic spectrum of the other emitters 6. The composition of these signal spectra forms the identification as a friend that is detected by the aerial vehicle 4. For purposes of disguising the identification as a friend, it is meaningful if it is variable, so that an old identification as a friend can be exchanged for a current one. On the receiver side, this is possible relatively easily by feeding the corresponding information into the tracking system 8 or its control unit 10. On the sender side, in the case of pyrotechnic emitters 6, a change of identification generally requires a material exchange of identification emitters 6a, 6b, 6c, 6d, 6e, 6f, for example from the container 16, 22. In the case of programmable igniters, it is possible to dispense with an exchange and the emitters 6 are fed new ignition information. FIG 5 shows such an exchange by way of example. A container 16 contains five emitters 6, one of which is a signal emitter 6e. This is intended to be replaced by a new signal emitter 6f, which has different emitting elements 20, which therefore differ in their spectral combination from the emitting elements 20 of the old emitter 6e. Such an exchange can be easily accomplished, as FIG 5 shows: the old signal emitter 6e is removed from the container 16 and replaced by the new signal emitter 6f. The
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container 16 provided with new emitters in this way is inserted into the vehicle 2 and made ready for use. By analogy with an infrared identification as a friend, a radar identification as a friend is also possible if the attacking aerial vehicle 4 tracks the vehicle 2 with radar radiation. The previously described details of the protection of the vehicle 2 by means of identification as a friend or foe can also be transferred – with the exception of the pyrotechnic details – to radar identification, so that they are not repeated in the following text. Only the differences of the radar methods from the IR methods are described. In the following text, the emission of an identification as a friend as a radar signal is described on the basis of FIG 6. The aerial vehicle 4 actively emits radar radiation 24, which is reflected at the vehicle 2 and picked up by the tracking system 8 of the aerial vehicle 4 and evaluated. On the basis of the reflected radar radiation, the vehicle 2 is localized and tracked. For its own protection, the vehicle 2 emits an identification as a friend, either by means of a built-in radar or by means of launching an emitter 6. The identification as a friend is expediently sent at the frequency at which the tracking sensor of the aerial vehicle 4 is sensitive, so that direct, and consequently rapid communication takes place between the vehicle 2 and the aerial vehicle 4. By analogy with infrared flares, there is also the possibility of launching decoys in the radar range. For this purpose, for example, a multiplicity of metal foils can be launched, for their part reflect the radar radiation 24 and consequently create an area of radar clutter around the vehicle 2 to be protected. In the case of the exemplary embodiment from FIG 6, such decoys are launched from the container 16 as emitters 6. They are passive emitters 6, which reflect the incident radar radiation 24 and consequently emit it again as a radar response 26. Among the emitters 6 there is one, or expediently more than one, emitter 6g provided with a radar modification unit. The radar modification units are graphically indicated in FIG 6 on the emitters 6g and modify the incident radar radiation, so that this modification is impressed on the re-emitted radar radiation 26 as an identification as a friend. The emitters 6g may be active or passive emitters 6g. Active emitters 6g contain an energy store, the energy of which is used for actively generating radar radiation 26. Passive emitters 6g reflect incident radar radiation 24, possibly in a modified way.
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One possibility of modification is that an electronic circuit of the radar modification unit absorbs part of the incident radar radiation 24, so that only part of the frequency band of the incident radar radiation 24 is reflected again. In the case of the example from FIG 6, three small spectra are absorbed out of the overall frequency band of the incident radar radiation 24, so that the radar response 26 consists of four frequency bands separate from one another, as is indicated in FIG 6 by the interrupted lines of the radar response 26. Of course, the number of absorbed frequency gaps or of the reflected frequency bands is freely selectable. The absorption may take place by a resonant circuit that is tuned to an absorption frequency and absorbs this frequency. The radar response 26 is received by the tracking system 8 of the aerial vehicle 4, and the control unit 10 evaluates the radar response 26 for an identification as a friend, detects the frequency gaps and compares them with information stored as an identification as a friend. If the frequency gaps coincide in number, position and/or width with the stored information, the identification as a friend is detected as such and the aerial vehicle 4 aborts the attack. It is likewise possible that one or more absorption frequencies are later “re-reflected”, that is to say sent after a time delay. This may take place by the activation of the resonant frequency being controlled by the charging of a capacitive element. This produces more possibilities of combination, and consequently better coding methods. The charging may take place from a radiated-in, integrated RF output. For example, a diode and a control capacitor apply a voltage, which then activates the diode used for turning on the resonator. The identification as a friend can then be defined by the combination of the capacitance of the control capacitor and the resonant frequency. For disguising the identification as a friend, a multiplicity of emitters 6 may be launched, each containing a coding unit in the form of a radar modification unit, though the individual radar modification units emit modified signals that are all different or are different in groups. In this way, the radar response 26 contains a multiplicity of differently modified signals, a third of which do not reveal whether an identification as a friend is contained and if so which signal is the identification as a friend. All that is important here is that there is an adaptation between the emitters 6g and the tracking system 8 in such a way that the tracking system 8 is able to detect the identification as a friend – among many other signals.
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In an analogous way, the radar modification unit may generate the radar response in such a way that it is frequency-shifted in relation to the incident radar radiation 24. For example, the entire incident frequency band is reflected with a predetermined frequency shift with the aid of the electronic structural units on the emitters 6g. Moreover, a doubling – or more generally: multiplication – of the incident radar radiation 24 is possible. For example, an echo is added to the unchanged reflection as an additional radar response 26. Since the incident radar radiation 24 is usually pulsed, the echo can be clearly detected by the aerial vehicle 4 – if it takes place at a time before the next pulse. A predetermined time offset between the original reflection and the echo can be the identification as a friend or part thereof. In other words, tracking radiation of the aerial vehicle 4 is absorbed by the emitters 6g and radiated again in a time-shifted manner in the direction of the aerial vehicle 4, the time shift being part of the friend signal. Apart from a passive emission of the radar response 26, an active emission of the radar response 26 is also possible. If a coding unit of an active emitter 6g receives the radar radiation 24, this may trigger the effect of active sending – powered by an energy store. The energy store may be a battery, a pyrotechnic battery or a capacitor, for example a Gold Cap. The identification as a friend may in this case be generated by an electronic circuit on the emitters 6g and radiated. When multiple emitters 6g are in the air and emit a modified signal as a radar response 26, in particular if it is an active signal, it is important that the emission of the radar response 26 takes place in a synchronized manner, so that it can be clearly received by the aerial vehicle 4. For this purpose, incident pulsed tracking radiation may in particular synchronize the active emitting units of the multiple emitters 6. The emitters 6g radiate the identification as a friend in a synchronized manner, so that their signal is cumulative and arrives at the aerial vehicle 4 in a clearly receivable state. For changing the identification as a friend, the radar modification unit or an active emitting unit may be reprogrammed or be given new software with a new identification as a friend. It is likewise possible to only or additionally change the transmitting antenna of an emitter 6g, so that it emits at a different frequency. For example, the antenna is shortened, or a pattern is punched into or out of the antenna, or the antenna is otherwise geometrically changed. In general, such fashioning of the antenna allows
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the identification as a friend to be generated, even without subsequent changing of the geometry for changing the code.
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List of designations Vehicle Aerial vehicle System of fins 6, 6a-g Emitter Submunition Tracking system Control unit Signal 14 Interfering laser Container Launching unit Radiation profile Emitting element 22 Container Radar radiation Radar response