Method for checking the alignment of a secondary surveillance radar

Abstract

The invention relates to a method for checking the alignment of a secondary surveillance radar (2), wherein a radar object (28) with a known actual position (26) is detected by the secondary surveillance radar (2) and the radar position (36) of the radar object (28) is determined and compared with the actual position (26). In order to enable the radar alignment to be checked even if there is not a real radar object (8) present in the airspace captured by the secondary surveillance radar (2), it is proposed that the checking be performed with a virtual radar object (28).

Description

[0001] Procedure for checking the alignment of a secondary surveillance radar

[0002] The invention relates to a method for checking the alignment of a secondary surveillance radar, in which a radar object whose actual position is known is detected by the secondary surveillance radar and the radar position of the radar object is determined and compared with the actual position.

[0003] Aircraft are located using primary surveillance radars, which display the relative position of the aircraft in spherical coordinates. If an aircraft needs to be uniquely identified, a secondary surveillance radar is used, which actively queries an aircraft transponder for a code, such as an identity friend or foe (IFF) code. The secondary surveillance radar is typically mechanically integrated with the primary surveillance radar, ensuring that the alignments of the two radars are fixed and error-free, for example, parallel to each other.

[0004] In order for the secondary surveillance radar to reliably transmit a code query to a location designated by the primary surveillance radar, the orientation of the secondary surveillance radar must actually correspond to the assumed orientation. To ensure the actual orientation of the secondary surveillance radar, an alignment check is carried out from time to time. For this purpose, the position of a radar object, for example an aircraft with a transponder, is determined using a primary surveillance radar and a secondary surveillance radar, and the two determined radar positions are compared. If the two positions deviate by more than a permissible tolerance, the two surveillance radars must be realigned. If the actual position of the radar object in space is known, the orientation of the secondary surveillance radar can also be checked without the primary surveillance radar.For this purpose, the actual position of the radar object is compared with the radar position determined by the secondary surveillance radar. If the two positions differ by more than a permissible tolerance, the secondary surveillance radar must be realigned.

[0005] It is an object of the present invention to provide a method for checking the alignment of a secondary surveillance radar that is improved over the prior art.

[0006] This problem is solved by a method of the type mentioned above, in which, according to the invention, the radar object is a virtual radar object. This can be processed in the same way as a real radar object, e.g., an aircraft with a transponder. It is detected by the secondary surveillance radar, and the resulting radar position of the radar object is determined and compared with the known actual position of the virtual radar object. A deviation between the two positions can then be determined and compared, for example, with a permissible tolerance.

[0007] The invention is based on the idea that the alignment check of the secondary surveillance radar using a real radar object is only possible if the object is actually present and also has an active transponder that transmits the requested response code. However, in a confrontational military context or from an unfriendly aircraft, no code is transmitted, so the secondary surveillance radar receives no response to its request whose direction of origin could be verified. Depending on the scenario, there may be no aircraft within the range of the secondary surveillance radar for a long time that could be used to verify its alignment. It is therefore advantageous to be able to perform an alignment check that does not require a real radar object in the secondary surveillance.By using a virtual radar object, which is conveniently fed into the signal processing chain of the secondary surveillance radar and whose actual position is known, the radar's alignment can be checked.

[0008] With this solution, no real radar target is required, which is advantageous in a confrontational military context. Furthermore, the check can be performed passively, i.e., without emitting an active radar beam. Furthermore, the method can be immune to external interference, such as reflections. Depending on the design, the computing power of an assigned primary surveillance radar can also remain free, since the check can be performed solely with the secondary surveillance radar.

[0009] A real radar object is a real flying object, such as an aircraft, that reflects radar radiation and is detected by a surveillance radar. The virtual radar object simulates a real radar object within the surveillance radar and can operate without a real radar object. It can be a signal that is fed into the surveillance radar and subsequently processed, in particular in the same way as a signal triggered by a real radar object in the surveillance radar. A virtual radar object and a radar signal fed into the surveillance radar as such are considered synonymous, since the virtual radar object is only a signal. A radar object is detected by the surveillance radar when it is recognized as a radar object by the surveillance radar. A radar position can then be assigned to it. The virtual radar object can be generated by a radar object generator.This conveniently indicates not only the virtual radar object but also its target radar position. A test unit can compare the actual radar position of the virtual radar object with its target radar position and use this to determine any alignment error of the secondary surveillance radar.

[0010] A radar position can be a position in space that is or was determined by the surveillance radar in relation to a real or virtual radar object. It can be a relative position, for example relative to the position of the surveillance radar. The radar position can differ from the actual position of a real radar object or a virtual radar object by more than a permissible tolerance in the event of incorrect alignment of the surveillance radar. The actual position of a virtual radar object is assigned to the virtual radar object. It can be the simulation of a location of the simulated real radar object at the time the virtual radar object is fed into the surveillance radar. It therefore comprises data that specify the actual position of the simulated real radar object in space. It can result from the time the virtual radar object is fed into the surveillance radar orits signal processing chain and the alignment of the surveillance radar - or, in the case of an active radar, its radar beam - at that time.

[0011] The alignment of the surveillance radar is independent of its active radiation. For example, a radar antenna can rotate even without emitting radar radiation and thus have a rotating alignment. An exact alignment leads to a correct radar position, which corresponds to the real position of the radar object in space. This makes it clear that alignment is not just about the mechanical alignment of the antenna - this can even be neglected if necessary, as it is usually accurate enough - or the electronic alignment of a beam, but includes the entire signal processing chain, so that the alignment is characterized by the radar position of the radar object. If, for example, a real radar object is located at 10° azimuth, but the radar position is 12° in azimuth, i.e. the position of the radar object determined by the surveillance radar, the alignment is inaccurate by 2°.The alignment can be checked using a correlation coefficient, which characterizes whether the radar position and the actual position are sufficiently identical in their properties, such as the position in space.

[0012] The actual position of the virtual radar object is known and is compared – for example, in a test unit – with the radar position of the virtual radar object. This position is known from the feed-in time and the orientation of the radar antenna at that time. Or to put it another way: With a radar antenna orientation dependent on the actual position, the virtual radar object is fed into the surveillance radar, so that it resembles a radar signal received at that time from a real radar object.

[0013] The surveillance radar, i.e. the primary or secondary surveillance radar, can be any radar for monitoring airspace. For example, the secondary surveillance radar can be part of a Ground Based Air Defense (GBAD) radar or a fire control radar. If a primary surveillance radar is present in addition to the secondary surveillance radar, it is expediently mechanically coupled to the secondary surveillance radar so that both surveillance radars are aligned in a predetermined relationship to one another, e.g., parallel to one another. Both the primary surveillance radar and the secondary surveillance radar can each be a rotating radar or a non-rotating radar, for example, each with multiple antennas. In this case, it is expedient to use at least one virtual radar object per antenna.The alignment check of the surveillance radar is advantageously performed in the background during spatial surveillance by the primary surveillance radar, if present, and / or during code verification by the secondary surveillance radar. In an advantageous embodiment of the invention, the virtual radar object is additionally detected by a primary surveillance radar, and the radar position of the virtual radar object is determined in the primary surveillance radar. This also allows the alignment of the primary surveillance radar to be checked. This can be done based on the actual position of the virtual radar object, which is compared with the radar position determined by the primary surveillance radar. Advantageously, both checks are performed consecutively using the same actual position, in particular first that of the secondary surveillance radar and then that of the primary surveillance radar.

[0014] It is also possible to compare the two radar positions of both surveillance radars obtained from the virtual radar object, i.e., to compare the determined radar position of the primary surveillance radar with the radar position determined by the secondary surveillance radar. By comparing the two radar positions of both surveillance radars, the alignment of the secondary surveillance radar and / or the primary surveillance radar can be verified. These checks based on the two radar positions are conveniently performed in addition to the checks based on the actual position.

[0015] Depending on the actual aerial image, real flying objects may be within radar range of the surveillance radar(s), leading to radar positions in one or both surveillance radars. It is therefore advantageous if, in addition to checking one or both surveillance radars using the virtual radar object, one or both surveillance radars are checked using a real radar object. If the actual position of the real radar object is known, the check can be carried out based on the actual position. If the actual position of the real radar object is not known, a check can still be carried out by comparing both radar positions. The radar positions should be determined simultaneously or within a predetermined time window in order to work with the identical real position of the real radar object in both surveillance radars.

[0016] The virtual radar object is advantageously fed into the primary surveillance radar and the secondary surveillance radar in parallel and synchronously. This allows the same actual position of the virtual radar object to be used for both checks. Furthermore, the radar positions of both surveillance radars can be directly compared. It can happen that a real radar object leads to a radar position that is in the immediate vicinity of a radar position of a virtual radar object. In this case, it can become unclear which radar position corresponds to the actual position of the virtual radar object and thus whether the alignment is correct or incorrect. To avoid this confusion, it is advantageous to use a primary surveillance radar to determine at least the radar position of a real radar object and to position the virtual radar object depending on the radar position of the real radar object.It is advantageous to maintain a minimum distance between the two radar positions, i.e., between the determined radar position of the real radar object and the actual position of the virtual radar object. This allows both radar objects to be clearly distinguished from each other, avoiding confusion as to whether there is an alignment error or which radar position belongs to which radar object.

[0017] In general, the invention can also be used to check the alignment of a primary surveillance radar alone or of a secondary surveillance radar and a primary surveillance radar, i.e. not only in addition to checking the alignment of the secondary surveillance radar, but also instead of checking the secondary surveillance radar. This then involves a method, as described above and below, for checking the alignment of a surveillance radar in the form of a primary surveillance radar or secondary surveillance radar. In a method for checking the alignment of the two surveillance radars, these can be part of a surveillance radar system that includes a secondary surveillance radar and a primary surveillance radar. In the above and below, all details described also apply to the primary surveillance radar instead of or in addition to the secondary surveillance radar.

[0018] The critical elements of a surveillance radar with regard to alignment errors are not so much the antenna, but rather the hardware and software used to process a radar signal. To detect as many potential errors as possible, it is therefore advantageous if the virtual radar object is fed into a signal processing chain of the secondary surveillance radar and / or a primary surveillance radar between the radar antenna and the signal hardware. The virtual radar object is preferably fed into the signal processing chain before the first signal processing hardware. The virtual radar object should undergo the same signal processing steps as the radar signal of a real radar object. In this way, all process steps downstream of the feed can be checked, and all downstream error sizes can be covered by the check.Advantageously, the signal processing chain behind the feed point is identical for the virtual radar object or its signal and for the signal resulting from a real radar object; the signal processing is therefore identical for both signals. The virtual radar object passes through the surveillance radar's hardware and software in the same way as the real radar object or its signal.

[0019] A suitable feed point for the virtual radar object is located between a receiving antenna element and a preamplifier in a surveillance radar signal processing chain. The virtual radar object can be fed in as raw data. It conveniently passes through electrical circuits, such as an amplifier element in the antenna, signal digitization, or an A / D converter. It conveniently passes through signal processing software, such as a center of gravity search and a digital filter.

[0020] The actual position of the virtual radar object can be assigned to it, it can be part of the virtual radar object, or it can be additionally transferred to the surveillance radar. To enable error-free verification, the time at which the signal is fed into the surveillance radar should be selected so that the target orientation of the surveillance radar corresponds to the actual position. This can be achieved by detecting the orientation of a radar antenna of the surveillance radar, which can correspond to the orientation of the radar beam when the radar is actively transmitting. The virtual radar object is fed into the signal processing of the surveillance radar depending on its orientation. The detected orientation is the target orientation, which can differ from the actual orientation of the surveillance radar to be verified. The time at which the virtual radar object is fed into the surveillance radar can be controlled by an encoder, which can be an azimuth encoder.The encoder can be a hardware encoder or, in the case of electronic scanning of the radar beam, such as the beam control of an AESA antenna, a software encoder. The antenna home can be selected as the reference position for both the feed and the radar position.

[0021] A radar object generator is particularly suitable for feeding the virtual radar object into a signal processing chain of the surveillance radar. The radar object generator can be a hardware radar object generator. With multiple antennas or channels, a separate radar object generator can be provided for each channel, with these channels ideally feeding the same radar object.

[0022] The radar object generator can be integrated into the surveillance radar, for example, the secondary surveillance radar. Another possibility is for the radar object generator to be separated from the radar system, which includes the secondary surveillance radar and possibly also a primary surveillance radar. With such a device separation, the radar object generator and radar system are housed in two different devices, which are, for example, mobile relative to each other or housed in different buildings. A spatial separation, i.e., an arrangement in two vehicles, is also possible, for example, in a radar vehicle and a command post vehicle.

[0023] The radar object generator and a test unit, which compares the actual radar position of the virtual radar object with its target radar position, can form a test system that can also include other components. With such a test system, several radar systems, each containing a secondary surveillance radar, can be tested. For this purpose, the test system is expediently separated from the radar systems in terms of vehicle or building space. For example, the test system is housed in a command post and from there monitors several radar systems, each located in its own vehicle or building. It is also possible for only the test unit, instead of the test system, to be located separately from the radar systems in terms of vehicle or building space. In this case, the radar systems could each contain their own radar object generator, each connected to the test unit.

[0024] Depending on the data connection between the radar object generator and the secondary surveillance radar, the transmission of the current radar orientation, determined, for example, by an angle encoder, to the radar object generator and the virtual radar object to the secondary surveillance radar for input may take too long to produce an accurate test result. If the virtual radar object is input too late, the current radar position will not match the radar's target position, with the result that a possibly exact actual position will not match the target position. To avoid a time delay that could be detrimental to the test, a device can be installed on the secondary surveillance radar, such as an intelligent interface, that triggers the input. The target position is communicated to the device, and when the radar reaches this position or orientation, the input is triggered from the device.

[0025] It is therefore advantageous if the virtual radar object is fed into a signal processing chain of the secondary surveillance radar when it reaches an orientation predetermined by the radar object generator, wherein the orientation is determined by a device on the secondary surveillance radar, which then triggers the feed, whereas the radar object generator is separated in terms of vehicle space from a radar system containing the secondary surveillance radar.

[0026] The alignment of the surveillance radar should be checked at regular intervals, for example every 30 minutes. To avoid disturbing or confusing the surveillance radar operator or automated analysis, it is advisable not to display the virtual radar object on an operator display or in an analysis image that may only be available as data. It should therefore be removed from the set of radar objects to be displayed; this set can be zero, so that no radar object is displayed after removal. To achieve this, the virtual radar object must be distinguishable from real radar objects in some way. One possibility is for the virtual radar object to contain a code that identifies the radar object as a virtual radar object. This code should be encrypted and secret so that it cannot be misused to make a real radar object disappear.

[0027] The code can be an IFF code, i.e. a friend-or-foe code. A bandwidth or number of IFF codes can be used to identify virtual radar objects. If the code is detected, the radar object can be removed from the radar objects displayed on an operator's visual display. The removal from the radar objects to be displayed can occur in the signal chain before the operator's visual display. This option is particularly suitable for use in a secondary surveillance radar. In a primary surveillance radar, the virtual radar object can have a radar signature in a frequency channel that identifies the radar object as a virtual radar object. Surveillance radars have several frequency bands and, within these, a multitude of frequencies at their disposal. They can use these bands to illuminate a real radar object, which are then reflected and received accordingly.A portion of these frequencies can be reserved for identifying virtual radar objects. The radar object can be identified as a virtual radar object and removed from the radar objects to be displayed, especially before an operator's visual display. The frequency or frequency channel should be available in addition to all primary monitoring channels used for area surveillance, so that a jammer cannot identify this channel and jam it.

[0028] Another possible identification option is a temporal code, meaning the virtual radar object is identified as a virtual radar object based on a temporal coding of the image input to the secondary surveillance radar. This can be a predetermined pause in the image input, a flashing, or another temporal coding, so that the virtual radar object appears and disappears at intervals, thus clearly identifying it.

[0029] The previous check is aimed at verifying the alignment of the surveillance radar. However, it is also possible to use this method to check other radar parameters. In addition to the alignment check, the object speed and / or the object cross-section of the virtual radar object can be checked. The object cross-section can be a radiation cross-section. As described above, an actual object speed and / or an actual object cross-section is assigned to the virtual radar object and passed to the surveillance radar for verification. The surveillance radar then compares a measured radar speed with the actual object speed or a measured radar cross-section with the actual object cross-section.

[0030] The invention is also directed to a secondary surveillance radar with a signal processing chain for detecting a radar object and a unit configured to perform a radar alignment check by comparing the radar position of the radar object with its known actual position. The secondary surveillance radar is expediently equipped with a device for recognizing an IFF code of the radar object.

[0031] To improve the alignment check of the secondary surveillance radar, the secondary surveillance radar according to the invention includes a radar object generator for feeding a virtual radar object into the signal processing chain of the secondary surveillance radar. This generator then feeds the virtual radar object into the signal processing chain of the secondary surveillance radar, for example, as described. The surveillance radar can be configured to carry out the method described above. The description of advantageous embodiments of the invention given so far contains numerous features, some of which are summarized in several dependent claims.However, the features can also be expediently considered individually and combined into further meaningful combinations, particularly in the case of claims that refer back to one another, so that a single feature of a dependent claim can be combined with a single, multiple, or all features of another dependent claim. Furthermore, these features can each be combined individually and in any suitable combination with all methods according to the invention as well as with the device according to the invention according to the description and / or the independent claims. Thus, method features can also be viewed as objectively formulated properties of the corresponding device unit, and functional device features can also be viewed as corresponding method features.

[0032] The above-described properties, features, and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more readily understood in conjunction with the following description of the embodiments, which are explained in more detail in conjunction with the drawings. The embodiments serve to illustrate the invention and do not limit the invention to the combination of features specified therein, including with regard to functional features. Furthermore, suitable features of each embodiment can also be explicitly considered in isolation, removed from one embodiment, incorporated into another embodiment to supplement it, and / or combined with any of the claims.

[0033] They show:

[0034] FIG 1 shows a functional diagram of a secondary surveillance radar with a radar object generator and a test unit,

[0035] FIG 2 shows a secondary surveillance radar together with a primary surveillance radar, a radar object generator and a test unit, FIG 3 shows a flowchart of a method for checking the alignment of a surveillance radar,

[0036] FIG 4 a radar system with secondary surveillance radar and primary surveillance radar and a separately arranged test system with radar object generator and test unit and

[0037] FIG 5 a test system connected to two separate radar systems.

[0038] FIG 1 shows a secondary surveillance radar 2 of a GBAD air defense radar, which may additionally have a primary surveillance radar (not shown). The secondary surveillance radar 2 contains a radar antenna 4, which can be mechanically or electronically rotated or pivoted within a radar scene 6. The radar scene 6 is a space monitored by the secondary surveillance radar 2 and in which real radar objects 8, such as aircraft or other flying objects, move and are detected by the secondary surveillance radar 2. The radar antenna 4 is a transmitting and receiving antenna for actively transmitting radar radiation and for receiving a response signal from a radar object 8, for example, an IFF code from its transponder. The secondary surveillance radar 2 further comprises a signal processing unit 10, which may contain hardware units 12 and software units 14.The hardware units 12 contain, for example, amplifier elements in the radar antenna 4 and an A / D converter. The illustration in FIG. 1 is therefore a functional representation, whereby the signal processing unit 10 can also contain hardware elements of the radar antenna 4. The software units 14 can contain software for a center of gravity search and digital filters.

[0039] During operation of the secondary surveillance radar 2, it transmits radar radiation to detected real radar objects 8 in the radar scene 6 and receives their response signal, for example an IFF code. The response signal is received in the radar antenna 4 and forwarded to the signal processing unit 10. There, the radar signal is converted into a digital radar object, which is assigned a radar position 16 determined from the direction of reception of the response signal. A filter 18 determines whether the detected radar object 8 is a real radar object 8 or a virtual radar object. If it is a real radar object 8, it is displayed in its radar position 16 on a display 20 for an operator. As shown in FIG 1, the two real radar objects 8 visible in the radar scene 6 are displayed on the display 20 at their radar position 16.

[0040] An angle encoder 22 in the form of an azimuth encoder is arranged on the radar antenna 4. This can be a hardware encoder for a mechanically rotatable antenna 4 or a software encoder for an electronically pivotable antenna 4. The angle encoder 22 detects the antenna orientation of the antenna 4 as a two-dimensional angle in spherical coordinates relative to an antenna reference, for example, antenna home, and transmits this to the signal processing unit 10 and to a radar object generator 24. The radar object generator 24 contains information about when and at which actual position 26 it should output one or more virtual radar objects 28 and feed them into or in front of the signal processing unit 10.If the radar antenna 4 covers an angular range that contains a virtual radar object 28 in the radar object generator 24, this radar object 28 is fed as an input data set into the signal processing chain 30 for detecting the radar object 8 by the radar object generator 24. The input data is fed as if the virtual radar object 28 were a real radar object 8, such as a response signal from an aircraft. The input data is fed directly after the receiving antennas and before the preamplifier of the radar antenna 4.

[0041] The virtual radar object 28 passes through the signal processing chain 30, which runs from the antenna 4 and through the signal processing unit 10, for example, to the display 20 or another output unit for further processing. The virtual radar object 28 is a signal that is identical in nature to radar signals generated by the real radar object 8 in the radar antenna 4. This signal, or virtual radar object 28, then passes through the subsequent part of the signal processing chain 30 and the signal processing unit 10 in exactly the same way as the real radar object 8 or its signal. As a result, radar positions 16, 36 are calculated for all radar objects 8, 28 at which the radar objects 8, 28 are located in the radar scene 6 or in an overall radar scene 40.

[0042] In the embodiment of FIG 1, the radar object generator 24 generates eight virtual radar objects 28 that are distributed within the virtual radar scene 32, which represents an artificial air situation image in the radar-internal coordinate system and forms the target result of the generation of the radar positions 36 of the virtual radar objects 28. The virtual radar scene 32 is similar to the radar scene 6 apart from any real radar objects 8 that may be present there. The virtual radar objects 28 are, for example, distributed equidistantly around the edge of the radar scene 32. All virtual radar objects 28 are processed by the signal processing unit 10 in exactly the same way as the real radar object 8 or its signal, so that both the real radar objects 8 and the virtual radar objects 28 are output by the signal processing unit 10 in the form of radar positions 16, 36, as shown in FIG 1 for explanation in a test radar scene 34.The virtual radar objects 28 or their radar positions 36 are not output on the display 20, since the filter 18 recognizes the IFF code(s) assigned to the virtual radar objects 28 and filters these radar objects 28 or their radar positions 36 out of the image to be displayed.

[0043] The radar scene 34 shown is for illustrative purposes only. It shows the real radar objects 8 in their radar position 16 and the virtual radar objects 28 in their radar position 36. The respective radar position 36 of the virtual radar objects 28 should not be confused with the respective actual position 26 of the virtual radar objects 28 in the virtual radar scene 32 and the overall radar scene 40, because errors in the signal processing chain 30 can distort the actual position 26.

[0044] The test radar scene 34 is made available to a test unit 38, which checks the alignment of the secondary surveillance radar 2. In addition to the mechanical or electronic alignment of the radar antenna 4, the alignment also includes the signal processing chain 30, which generates the radar positions 16, 36 of the radar objects 8, 28. Below the test unit 38, the overall radar scene 40 is shown for illustrative purposes in FIG. 1. This scene is digitally evaluated in the test unit 38 and does not have to be present as a scene as shown, but can be present in any data format. The radar positions 16 of the two real radar objects 8 can be seen, which are represented as vertical crosses. Also shown are the radar positions 36 of the virtual radar objects 28, which are represented as diagonal crosses. Furthermore, the actual positions 26 of the virtual radar objects 28 are represented as diagonal hollow crosses.The actual positions 26 are the target positions of the radar positions 36 of the virtual radar objects 28.

[0045] There are no actual positions available for the radar positions 16 of the two real radar objects 8, so they cannot be verified. However, the actual positions 26 of the radar positions 36 of the virtual radar objects 28 are available. The radar positions 36 are then compared by the verification unit 38 with the actual positions 26, for example using a correlation coefficient, and a decision is made as to whether the alignment is correct or whether there is an unacceptable deviation. Since the processed air situation in the form of the test radar scene 34 and the artificial air situation in the form of the virtual radar scene 32 are located in the same radar-internal coordinate system, the verification unit 38 can compare these two data sets with regard to the angular deviations and taking into account defined tolerances, e.g. from the antenna pattern of the radar antenna 4, using a suitable mathematical method.

[0046] FIG 1 shows that, with the exception of one, the radar positions 36 coincide quite well with the actual positions 26. Here, the check is positive and the alignment of the secondary surveillance radar 2 is correct in these sectors. However, the check for one radar position 36 is negative; this radar position 36 is circled in FIG 1 for better visibility. It can be seen that there is a large deviation between the radar position 36 and the associated actual position 26, which exceeds a permissible tolerance. The entire check of the alignment of the secondary surveillance radar 2 is therefore negative, and the secondary surveillance radar 2 must be realigned.

[0047] In this way, the signal processing chain 30 of the secondary surveillance radar 2 is continuously monitored with the test loop consisting of radar object generator 24, test unit 38 and signal processing chain 30 and detects faulty deviations in the alignment of the secondary surveillance radar 2 caused by the hardware 12, software 14 or another area of ​​the processing. All this takes place without active radiation of the radar antenna 4, but can also take place during transmission operation.

[0048] FIG. 2 shows an exemplary embodiment with a radar system 42 that includes a secondary surveillance radar 2 and a primary surveillance radar 44. The secondary surveillance radar 2 includes the radar antenna 4, the signal processing chain 30, and the signal processing unit 10, and is constructed as described for FIG. 1. The primary surveillance radar 44 is not identical but is constructed in a similar manner, as can be seen in FIG. 2. The following description is essentially limited to the differences from the exemplary embodiment shown in FIG. 1, to which reference is made with regard to features and functions that remain the same. In order to avoid having to repeat what has already been described, all features of the previous exemplary embodiment are generally adopted in the following exemplary embodiment without being described again, unless features are described as differences from the previous exemplary embodiment.

[0049] Both surveillance radars 2, 44 are equipped with a radar antenna 4, which may be different but are provided with the same reference numeral in FIG. 2 for the sake of clarity. The same applies to their signal processing units 10. The radar antennas are four non-rotator primary surveillance radar antennas with four fixedly aligned AESA antennas or four non-rotator AESA secondary surveillance radar antennas. The angle encoder 22 is part of the radar antennas 4 and samples the control signal of the radar antennas 4 and determines their antenna alignment from this. The radar object generator 24 is connected to the signal processing chains 30 of both surveillance radars 2, 44 and feeds virtual radar objects 28 into both signal processing chains 30, preferably identical virtual radar objects 28 into both surveillance radars 2, 44 at identical times. However, the identity of the virtual radar objects 28 does not include their coding for their recognition.While the virtual radar object 28 for the secondary surveillance radar 2 is marked with an IFF code that identifies it as a virtual radar object 28, the virtual radar object 28 for the primary surveillance radar 44 is provided with a frequency or in a frequency range that identifies it as a virtual radar object 28. In this way, the virtual radar objects 28 or their radar positions 26 can be filtered out of the display 20 by the filter 18. At least one virtual radar object 28 is input for each of the radar antennas 4 of the two surveillance radars 2, 44 so that each radar antenna 4 can be checked. The virtual radar objects 28 are fed in as raw data directly after the A / D converter.

[0050] As in the previous embodiment, two real radar objects 8 are located in the radar scene 6, which are displayed on the display 20 in their radar position 16 for an operator. For the sake of simplicity, the representation of the virtual radar objects 28 in FIG. 2 is also the same as in the previous embodiment. However, the test radar scene 34 and the overall radar scene 40 differ from the embodiment of FIG. 1 in that the radar positions 46, 48 of the real radar objects 8 processed by the primary surveillance radar 44 and the virtual radar objects 28 are also shown there. For better understanding, the individual positions are listed in the form of a legend in FIG. 2:

[0051] The radar positions 16 of the real radar objects 8 from the secondary surveillance radar 2 The radar positions 46 of the real radar objects 8 from the primary surveillance radar 44

[0052] The radar positions 36 of the virtual radar objects 28 from the secondary surveillance radar 2

[0053] The radar positions 48 of the virtual radar objects 28 from the primary surveillance radar 44 and

[0054] The actual positions 26 of the virtual radar objects 28 from the radar object generator 24

[0055] It is shown that the radar positions 16, 46 of the real radar objects 8 from both surveillance radars 2, 44 are well aligned, so that there is no incorrect alignment of either of the two surveillance radars 2, 44. However, not all virtual radar objects 28 are processed correctly, so that their radar positions 36, 48 are partially incorrect. These errors are also circled in FIG 2. In the lower circle, the radar position 48 of a virtual radar object 28 from the primary surveillance radar 44 deviates significantly from the actual position 26 of the respective virtual radar object 28 from the radar object generator 24. In the upper circle, as in the previous exemplary embodiment, the radar position 36 of a virtual radar object 28 from the secondary surveillance radar 2 is too far away from the actual position 26, i.e. its target position, so that the tolerance bandwidth is exceeded and an incorrect alignment is thus output.

[0056] In the scenario illustrated in FIG 2, real radar objects 8 are present for both the primary surveillance radar 44 and the secondary surveillance radar 2, which are each processed into radar positions 16, 46. In principle, it is sufficient for an alignment check to compare the radar positions 16, 46 with each other. In the present case, this check is positive because the radar positions 16, 46 of all radar objects 8 are within a tolerance distance from each other. However, if no real radar object 8 is present for the secondary surveillance radar 2, as is common in a confrontational military scenario, the radar position 46 is omitted and the virtual radar objects 28 are necessary for the check. These also have the advantage that they can be distributed specifically across the radar scene 32, so that each antenna sector and its signal processing chain 30 can be specifically checked.In addition, the virtual radar objects 28 can be distributed such that they are not too close to a radar position 16, 46 of a real radar object 8. This can lead to confusion as to which radar object 8, 28 a radar position 16, 46 belongs, making it unclear whether an alignment error exists. In both figures, the actual positions 26 of the virtual radar objects 28 are selected such that they are at a minimum distance from the radar positions 16, 46 of all real radar objects 8, thus avoiding the described ambiguities.

[0057] FIG 3 shows a flowchart of a test method for checking the alignment of one of the surveillance radars 2, 44. The test method can be carried out in the same way for both surveillance radars 2, 44. In the first step 50, the angle encoder 22 is queried continuously or at fixed time intervals. This step 50 is carried out by the surveillance radar 2, 44, as shown on the right in the diagram. If the radar antenna 4 reaches an angular range which contains a virtual radar object 28 in the radar object generator 24, this radar object 28 is fed in the second step 52 as an input data set into the signal processing chain 30 for detecting the radar object 8, specifically by the radar object generator 24, as shown on the right. In principle, this process runs in a query loop, which has been omitted from the flowchart for the sake of clarity.

[0058] Steps 54 and 56, namely the hardware processing 54 and the software processing 56 of the radar objects 8, 28, take place again in the respective surveillance radar 2, 44. Using the filter 18 of the respective surveillance radar 2, 44, a query is made in step 58 as to whether the radar object 8, 28 is a real radar object 8 or a virtual radar object 28. If it is a virtual radar object 28, it is removed from the set of radar objects 8, 28 in step 60 and is not displayed. If it is a real radar object 8, it is not filtered out and is displayed on the display 20 in step 62.

[0059] Regardless of the outcome of this query, the method always proceeds to step 64, in which the alignment of the respective surveillance radar 2, 44 is checked by the test unit 38. For this purpose, the actual positions 26 provided by the radar object generator 24 are input to the test unit 38 in step 66. This compares - depending on the existing surveillance radar 2, 44: the radar positions 36 from the secondary surveillance radar 2 and / or the radar positions 48 from the primary surveillance radar 2 with the actual positions 26 of the virtual radar objects 28 from the radar object generator 24, the radar positions 36 of the virtual radar objects 28 from the secondary surveillance radar 2 with the radar positions 48 of the virtual radar objects 28 from the primary surveillance radar 2 and / or the radar positions 16 of the real radar objects 8 from the secondary surveillance radar 2 with the radar positions 46 of the real radar objects 8 from the primary surveillance radar 44.

[0060] The test can be performed in this or a different order. If all tested position deviations are within a predetermined tolerance range, the alignment is determined to be OK in step 68. If there is a position deviation that exceeds the predetermined tolerance range, the alignment is determined to be incorrect in step 70.

[0061] FIG. 4 shows a radar system 72 which, with regard to the surveillance radars 2, 44, can be designed identically to the radar system 42. A variation without a primary surveillance radar 44 is also possible, with the primary surveillance radar 44 also being shown in FIG. 4 to illustrate a possible embodiment. The exemplary embodiment from FIG. 4 differs from the preceding exemplary embodiments in that the radar object generator 24 and the test unit 38 are not integrated in the radar system 72, as in the radar system 42 from FIG. 2 or the secondary surveillance radar 2 from FIG. 1, but are present separately, in particular by a spatial separation in another building or vehicle. The radar object generator 24 and the test unit 38 are components of a test system 74 which is present separately from the surveillance radars 2, 44. Thus, the radar system 72 can be accommodated in one radar vehicle and the test system 74 in another vehicle.For example, radar object generator 24 and test unit 38 are arranged in a command post or a Higher Echolon Unit.

[0062] The radar object generator 24 and the test unit 38 are connected to the secondary surveillance radar 2 and, if present, also to the primary surveillance radar 44 via one or more wired or wireless data connections, such that the data exchange between radars 2 and, if applicable, 44 and the test system 74, as described in the preceding exemplary embodiments, takes place. The measured or acquired radar orientation is communicated to the radar object generator 24, which feeds the positions and, if applicable, the type of the virtual radar objects 28 into the signal processing chain 30 for the surveillance radar 2, 44. It is also possible for the radar object generator 24 to instruct the surveillance radar 2, 44 to feed the positions and, if applicable, the type of the virtual radar objects 28 into the signal processing chain 30 when the surveillance radar 2, 44 reaches a predetermined position or orientation.This can be achieved by an additional intelligent interface between radar object generator 24 and surveillance radar 2, 44 on surveillance radar 2, 44.

[0063] The surveillance radar 2, 44 sends the radar positions 36, 46, 48 to the test unit 38, which checks the alignment of the surveillance radar and classifies it as sufficient or insufficient. The result is sent from the test unit 38 to an interface 76, for example, to a visual output unit for an operator or a data interface for a combat unit. The radar positions 36, 46, 48 can also be sent to the interface 76, e.g., for visualization and / or verification.

[0064] Due to the separation of surveillance radar 2, 44 and test system 74 in terms of equipment and, if necessary, building or vehicle space, radar object generator 24 and test unit 38 can also be used separately for other radars. This is illustrated by way of example in FIG. 5.

[0065] FIG. 5 shows two radar systems 72, which, with regard to the surveillance radars 2, 44, can be designed identically to radar system 42—with or without primary surveillance radar 44. For the sake of simplicity, the details of radar systems 72 have been omitted from FIG. 5. Also shown is the spatially separated command post, although any separation of equipment is sufficient in principle. Surveillance radars 2, 44 and the test system 74 with radar object generator 24 and test unit 38 only need to be separated from each other in terms of equipment in such a way that at least one further radar can be connected to the test system 74, which is present in addition to the surveillance radar(s) of radar system 72.

[0066] The data exchange between the radar systems 72 and the test system 74 takes place as described for the previous embodiments, with the difference that the test system 74 processes the data from at least two radar systems 72, since, of course, more than two radar systems 72 can also be connected. In this way, the alignment of several radar systems 72 can be monitored with a single test system 74, e.g., in a command post.

[0067] 2 secondary surveillance radar

[0068] 4 radar antenna

[0069] 6 Radar scene

[0070] 8 real radar object

[0071] 10 Signal processing unit

[0072] 12 hardware units

[0073] 14 software units

[0074] 16 Radar position

[0075] 18 filters

[0076] 20 ad

[0077] 22 angle encoders

[0078] 24 Radar object generator

[0079] 26 Actual position

[0080] 28 virtual radar object

[0081] 30 Signal processing chain

[0082] 32 virtual radar scene

[0083] 34 Test radar scene

[0084] 36 radar position

[0085] 38 test unit

[0086] 40 Total radar scene

[0087] 42 radar system

[0088] 44 Primary Surveillance Radar

[0089] 46 Radar position

[0090] 48 radar position

[0091] 50 Query angle encoder 22

[0092] 52 Feeding a virtual radar object 28

[0093] 54 Hardware processing

[0094] 56 Software processing

[0095] 58 Checking the type of radar object 8, 28

[0096] 60 Filtering out virtual radar objects 28

[0097] 62 Display of real radar objects

[0098] 64 Checking the alignment

[0099] 66 Transfer of actual positions 26 to test unit 38

[0100] 68 Alignment OK

[0101] 70 Alignment not correct Radar system test system interface

Claims

Patent claims 1. Method for checking the alignment of a secondary surveillance radar (2), in which a radar object (28) whose actual position (26) is known is detected by the secondary surveillance radar (2) and the radar position (36) of the radar object (28) is determined and compared with the actual position (26), characterized in that the radar object (28) is a virtual radar object (28).

2. Method according to claim 1, characterized in that the virtual radar object (28) is additionally detected by a primary surveillance radar (44), the radar position (48) of the virtual radar object (28) is determined in the primary surveillance radar (44) and the alignment of the primary surveillance radar (44) is checked on the basis of the actual position (26) and / or the radar position (36) determined by the secondary surveillance radar (2).

3. Method according to claim 2, characterized in that in addition to checking the two surveillance radars (2, 44) using the virtual radar object (28), a check of both surveillance radars (2, 44) using a real radar object (8) is carried out by comparing the two radar positions (16, 46) of the real radar object (8).

4. Method according to claim 2 or 3, characterized in that the virtual radar object (28) is input into the primary surveillance radar (44) and the secondary surveillance radar (2) in parallel and synchronously.

5. Method according to one of the preceding claims, characterized in that at least the radar position (46) of a real radar object (8) is determined by means of a primary monitoring radar (44) and the virtual radar object (28) is positioned at a minimum distance from the radar position (46) of the real radar object (8).

6. Method according to one of the preceding claims, characterized in that the alignment of a primary surveillance radar (44) is checked instead of checking the alignment of the secondary surveillance radar (2).

7. Method according to one of the preceding claims, characterized in that the virtual radar object (28) is fed between the radar antenna (4) and a signal hardware into a signal processing chain (30) of the secondary surveillance radar (2), wherein the virtual radar object (28) undergoes the identical signal processing steps as a radar signal of a real radar object (8).

8. Method according to one of the preceding claims, characterized in that the virtual radar object (28) is fed into a signal processing chain (30) of the secondary surveillance radar (2) between a receiving antenna element and a preamplifier.

9. Method according to one of the preceding claims, characterized in that the orientation of a radar antenna (4) of the secondary surveillance radar (2) is detected and the virtual radar object (28) is fed into the signal processing chain (30) of the secondary surveillance radar (2) as a function of this orientation.

10. Method according to one of the preceding claims, characterized in that the virtual radar object (28) is fed into a signal processing chain (30) of the secondary surveillance radar (2) by a radar object generator (24) wherein the radar object generator (24) is separated in terms of vehicle space from a radar system (72) containing the secondary surveillance radar (2) and is also connected to a further radar system (72) containing a secondary surveillance radar (2) for inputting a virtual radar object (28) into this further secondary surveillance radar (2).

11. Method according to one of the preceding claims, characterized in that the virtual radar object (28) is fed into a signal processing chain (30) of the secondary surveillance radar (2) when it reaches an orientation predetermined by the radar object generator (24), the orientation being determined by a device on the secondary surveillance radar (2), which then triggers the feed, whereas the radar object generator (24) is separated in terms of vehicle space from a radar system (72) containing the secondary surveillance radar (2).

12. Method according to one of the preceding claims, characterized in that the virtual radar object (28) has a radar signature on a frequency channel and / or an IFF code which identifies the radar object (28) as a virtual radar object (28), and the radar object (28) is removed from the radar objects (8) to be displayed on an optical display (20) of an operator.

13. Method according to one of the preceding claims, characterized in that the virtual radar object (28) is identified as a virtual radar object (28) on the basis of a temporal coding of the input into the secondary surveillance radar (2).

14. Method according to one of the preceding claims, characterized in that in addition to the position check, a check of the object speed and the object cross-section of the virtual radar object (28) is carried out.

15. Secondary surveillance radar (2) with a signal processing chain (30) for detecting a radar object (28) and a test unit (38) which is arranged is to carry out a check of the radar alignment by comparing the radar position (36) of the radar object (28) with its known actual position (26), characterized by a radar object generator (24) for feeding a virtual radar object (28) into the signal processing chain (30).

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