AN ANTENNA WITH AN OPTIMIZED ANTENNA ARRAY

Abstract

The present invention relates to an antenna with an antenna array, for example, an Active Electronically Scanned Array (AESA). The antenna can be used for communication, radar, or electronic support. The antenna array comprises at least a first arrangement of antenna elements of the first type and a second arrangement of antenna elements of the second type. The antenna array is thus composed of at least two types of antenna elements.

Description

TECHNICAL FIELDThe present invention relates to an antenna having an antenna array-for example an active electronically scanned array (AESA) or a passive electronically scanned array (PESA), which are also called an active or passive electronically controlled or scanned array. The antenna may be for communication, or may be used for radar, or may be used for electronic assistance measures. The antenna array of the antenna is optimized for more efficiency, a smaller radar cross section and a better field of view of the antenna.BACKGROUNDThe AESA or PESA technologies represent a significant advance in the field of antennas and offer numerous advantages over conventional antennas. For example, by integrating an AESA into an antenna, an improvement in the performance, flexibility and efficiency of the antenna can be achieved. Antennas with AESA are of great interest for a variety of applications, for example for communication systems, radar systems, wireless networks, electronic interference systems, or electronic reconnaissance.Antennas with AESA are however in need of improvement with regard to their efficiency, the occurrence of undesired side lobes (also called sidelobes) alongside the main beam in operation, and their field of view.BREAKDOWNIt is therefore an object of the present invention to provide an improved antenna having an antenna array, such as an AESA. In particular, the antenna is to be improved with respect to its efficiency compared to a conventional antenna. In addition, undesired side lobes next to the main beam should be suppressed to the greatest possible extent during operation of the antenna. A larger steering angle of the antenna is another goal to improve the field of view of the antenna. In this case, scanning losses over the field of view of the antenna should also be minimized. Finally, the antenna should allow a smaller radar cross section.These and other objects are achieved by the solutions of the present invention described in the independent claims. Advantageous embodiments are further described in the dependent claims.The solutions of the present invention are generally based on the finding that a disadvantage of a conventional antenna having an antenna array, for example an AESA, is that the antenna array is constructed with antenna elements of the same type.Such a structure of the antenna array can result in a lack of efficiency of the antenna, since all antenna elements have the same radiation characteristic and it can be difficult to achieve optimum radiation power and energy utilization, in particular in specific directions or in specific requirements. Also, due to the uniform structure of the antenna array, pronounced side lobes may occur during operation, which may impair the signal quality of the antenna. Furthermore, the antenna elements of the same type of antenna array can also lead to a limited steering angle, as a result of which the coverage and detection of signals can be restricted to an excessively narrow angle range.It could be confirmed by mathematical derivations, simulations and tests of assembled antennas that an antenna array of an antenna can be optimally constructed in another way, namely with different types of antenna elements. Thus, with optimum suppression of side lobes during operation, amplifiers of the antenna array can be used, for example. AESA can be optimally controlled, so that the efficiency of the antenna is increased. In addition, by configuring the antenna array in this way, a better field of view of the antenna can be achieved, i.e. the antenna array can be optimized in such a way that it can better capture signals from specific directions or can radiate in these directions with more gain, less side lobes and more efficiency.Accordingly, a first aspect of the present invention provides an antenna comprising an antenna array. The antenna is suitable for communication and / or for radar and / or for electronic assistance measures. The antenna array of the antenna has at least a first arrangement of antenna elements of the first type and a second arrangement of antenna elements of the second type.The structure of the antenna array with the antenna elements that are not similar makes it possible to achieve the advantages explained above, in particular a higher efficiency of the antenna, a better field of view, less pronounced side lobes, and a smaller radar cross section.In an embodiment of the antenna, the antenna array is an AESA. In another embodiment of the antenna, the antenna array is a PESA. In another embodiment of the antenna, the antenna array is a parallel plate waveguide (PPW) array.In an embodiment of the antenna, the first arrangement is arranged in the center of the antenna array and the second arrangement is arranged around the first arrangement.In particular, the antenna elements of the second type can be arranged at the edges or an edge region of the antenna array and the antenna elements of the first type can be arranged in the center or a central region of the antenna array. By appropriately selecting the antenna elements of the first type or of the second type, the mentioned advantageous properties of the antenna can be optimized.In an embodiment of the antenna, the antenna elements of the first type of the first arrangement of antenna elements are configured to radiate out of the plane of the antenna array and the antenna elements of the second type of the second arrangement of antenna elements are configured to radiate into the plane of the antenna array.For example, the first arrangement can thus be designed to radiate out of the plane, for example perpendicular to the plane of the antenna array, and the second arrangement can be designed to radiate into the plane, for example parallel to the plane of the antenna array. The antenna elements of the first type can be longitudinal radiators, the antenna elements of the second type can be transverse radiators with respect to the antenna array plane. The antenna can thus have a higher efficiency with simultaneously less pronounced side lobes.In an embodiment of the antenna, the antenna array further comprises a third arrangement of antenna elements of a third type.A third type of antenna elements allows a further optimization of the advantageous properties of the antenna.In an embodiment of the antenna, the third arrangement is arranged around the first arrangement and the second arrangement is arranged around the third arrangement.In particular, the antenna elements of the third type can be arranged outside the center of the antenna array and the antenna elements of the second type can be arranged at the edges of the antenna array or an edge region of the antenna array. The three arrangements can be arranged annularly or circularly around one another. However, square or rectangular arrangements are also possible.In an embodiment of the antenna, the antenna elements of the third type of the third arrangement of antenna elements are designed to radiate at an angle to the plane of the antenna array.For example, the antenna elements of the third type can be designed to radiate at an angle to the plane of the antenna array.The antenna elements of the third type can be helical radiators with respect to the antenna array plane and can be combined with transverse radiators and / or longitudinal radiators in the other arrangements.In one embodiment of the antenna, the antenna elements of the first type, the antenna elements of the second type and, if present, the antenna elements of the third type are different from one another and are each selected from the following group: broad-side antenna elements (also called broadside antenna elements); end-line antenna elements (also called directional antenna elements); Yagi antenna elements; pyramid antenna elements; Vivaldi antenna elements; butterfly antenna elements; fan antenna elements (also called bow-tie antenna elements); patch antenna elements (also called planar antenna elements); helix antenna elements; monoconus antenna elements; sinusoidal antenna elements; camouflage antenna elements (also called camouflage-cap-suitable antenna elements).In an embodiment of the antenna, the first array is a broadside array and the second array is an end-fire array.An end-fire array is also referred to as a directional antenna array. The antenna elements of the end-fire array may be longitudinal radiators, while the antenna elements of the broad-side array may be transverse radiators.In an embodiment of the antenna, the first array has Yagi antenna elements as the first type antenna elements and the second array has mono-cone antenna elements as the second type antenna elements.This is an advantageous example of an antenna with an antenna array constructed from non-similar antenna elements.In an embodiment of the antenna, the first array has broadside antenna elements as the first type antenna elements, the second array has end-fire antenna elements as the second type antenna elements, and the third array has Yagi antenna elements or pyramid antenna elements as the third type antenna elements.These are further advantageous examples of antennas having an antenna array which is constructed from antenna elements which are not of the same type.In one embodiment of the antenna, the antenna is configured to attenuate side lobes from outside the center of the antenna array or antenna elements arranged at the edges or in an edge region of the antenna array during operation of the antenna.For example, the side lobes are attenuated compared to antenna elements arranged in the center or a central region of the antenna array. Thus, the antenna can be operated overall with less pronounced side lobes with simultaneously higher efficiency.In one embodiment of the antenna, the antenna is designed for use in an aircraft or a flying platform.In one embodiment of the antenna, the antenna is designed for use in a ground-bound vehicle and / or in a water-bound vehicle and / or in a land-bound structure.A second aspect of the invention provides a method of operating an antenna according to the first aspect, the method comprising: operating the first array of antenna elements of the first type arranged in the centre of the antenna array, wherein the antenna elements of the first type of the first array radiate out of the plane of the antenna array during operation, for example perpendicularly to the plane of the antenna array; and operating the second array of antenna elements of the second type arranged around the antenna elements of the first type, wherein the antenna elements of the second type of the second array radiate into the plane of the antenna array during operation.In an embodiment of the method, the method further comprises attenuating side lobes of the second array compared to side lobes of the first array in operation.Overall, the antenna according to the invention or the method according to the invention achieves one or more of the advantages mentioned at the beginning compared to conventional antennas or methods. For example, improved efficiency, a larger field of view, less scanning losses over the field of view, weaker side lobes, and a reduced radar cross-section.BRIEF DESCRIPTION OF THE DRAWINGSThe above-described aspects and embodiments will now be described in more detail with reference to the following drawings. Fig. 1 schematically shows an antenna according to the present invention with an antenna array constructed of different kinds of antenna elements. Fig. 2 shows a first example of an antenna according to the present invention with an antenna array constructed of three different types of antenna elements. FIG. 3 shows signal levels (amplitude) of side lobes for antenna elements arranged at different positions of the antenna array of an antenna according to the first example. Fig. 4 shows a second example of an antenna according to the present invention, having an antenna array constructed of three different kinds of antenna elements. FIG. 5 shows a radiation characteristic of an antenna with antenna array according to the present invention. FIG. 6 shows signal levels (amplitude) of side lobes for antenna elements arranged at different positions of the antenna array of an antenna according to the second example. Fig. 7 shows radiation angles for antenna elements of different type of an AESA of an antenna according to the present invention. Fig. 8 shows a third example of an antenna according to the present invention, having an antenna array constructed of two different kinds of antenna elements. Figure 9 illustrates a method of operating an antenna with an antenna array in accordance with the present invention.DETAILED DESCRIPTIONFigure 1 shows an antenna 10 according to the present invention. The antenna 10 can be used in various ways. For example, the antenna 10 can be used for communication. The antenna 10 may be, for example, part of a communication system, for example, operating in a wireless communication network. The antenna 10 can also be used for radar applications, however, that is to say can be suitable for radar. The antenna 10 may be part of a radar system for this purpose. The antenna 10 can also be used for electronic assistance measures, for example for disturbing or elucidating signals.The antenna 10 can be used-regardless of which of the above-mentioned applications it is used-either in an aircraft, or in a flying platform, or in a ground-bound vehicle, or in a water-bound vehicle, or in a land-bound structure. The antenna 10 can be adapted to the respective location of use with regard to, for example, its size, or its power, or its electronic control. The antenna 10 can also be integrated into an antenna system already existing at this location of use.The antenna 10 comprises at least one antenna array 11. The antenna array 11 may be an AESA (also referred to as an active electronically scanned array). The antenna array may alternatively be a PESA or a PPW array. The antenna array 11 has at least a first arrangement 12 and a second arrangement 14 of antenna elements. Both arrangements 12 and 14 may be sub-antenna arrays of antenna array 11. The arrays 12 and 14 differ in the type of antenna elements from which they are constructed, which are therefore also called basic elements. The antenna array 11 thus has at least two different types of antenna elements. Each of the arrays 12 and 14 may include a plurality of antenna elements arranged in a plane. This plane is the plane of the antenna array 11. the antenna elements of each arrangement 12 or 14 or of the antenna array 11 as a whole can be arranged, for example, in rows and / or columns. The antenna elements can be individually controlled by the antenna 11.For example, the antenna elements of an AESA can be used as antenna array 11 to electronically control a main beam radiated from antenna 10. By precisely matching phases and amplitudes of the individual antenna elements, the main beam can be aligned, tilted and adapted to different requirements. The AESA 11 thus enables rapid target detection, precise coverage of a directional range, and effective interference suppression.The first arrangement 12 contains antenna elements of the first type 13 and the second arrangement 14 contains antenna elements of the second type 15 (as indicated by the enlargement in FIG. 1 ). The antenna elements of the first type 13 are different from the antenna elements of the second type 15, in particular different in their radiation characteristic, but preferably also in their shape or structure. The antenna 10 thus comprises antenna elements 13 and 15 of different types. Each arrangement 12 or 14 preferably contains only the antenna elements of one type 13 or 15.Various types of antenna elements may be, for example, the following: broadside antenna elements, or end-line antenna elements, or Yagi antenna elements, or pyramid antenna elements, or Vivaldi antenna elements, or butterfly antenna elements, or fan antenna elements, or patch antenna elements, or helix antenna elements, or monoconus antenna elements, or sinusoidal antenna elements, or camouflage antenna elements.As further exemplarily shown in FIG. 1, the second assembly 14 may be disposed around the first assembly 12. For example, the antenna elements of the first type 13 of the first arrangement 12 can be arranged in the center of the antenna array 11, while the antenna elements of the second type 15 of the second arrangement 14 are arranged outside the center or at the edges of the antenna array 11, wherein the terms "center" and "edges" as shown not only strictly denote the center of the antenna array 11 or the outer sides of the antenna array 11, but rather describe a central region of the antenna array 11 or an outer region or edge region of the antenna array 11. It is also possible to realize other arrangements of the antenna elements 13, 15 of the antenna array 11.The first array 12 may be a wide page array and the second array 14 may be an end-fire array. By mixing broadside and end-edge arrays, a greater field of view of the antenna can be achieved. Due to the various antenna elements having different individual radar cross-sectional characteristics (RCS characteristics), a smaller overall radar cross-section of the antenna 10 may be achieved.Fig. 2 shows a first example of an antenna 10 according to the present invention, which is constructed on the antenna 10 shown in Fig. 1.The antenna 10 of Fig. 2 includes three different arrangements of antenna elements. The antenna 10 contains a first arrangement 12 of antenna elements of the first type 13 and a second arrangement 14 of antenna elements of the second type 15, as already the antenna from FIG. 1.The first type antenna elements 13 in this first example are broadside antenna elements, the second type antenna elements 15 are end-edge antenna elements, and the third type antenna elements 22 are pyramid antenna elements. The third type antenna elements 22 are arranged between the first type antenna elements 13 and the second type antenna elements 15. The third type antenna elements 22 of the third arrangement 21 are arranged, for example, around the first arrangement 12 and the second type antenna elements 15 of the second arrangement 14 are arranged around the third arrangement 22. The first arrangement 12 can be arranged here in the center (or a central region) of the antenna array 11, the third arrangement can be arranged outside the center and around the center (for example in an intermediate region), and the second arrangement 14 can be arranged at the edges of the antenna array 11 (or in an edge region of the antenna array 11).FIG. 3 shows signal levels (amplitudes) of side lobes for individual antenna elements at different positions of an AESA as the antenna array 11 in an antenna 10 according to the first example. The antenna 10 for FIG. 3 also contains three different arrangements 12, 14, 21 of antenna elements of the first type 13, second type 15 and third type 22, respectively, like the antenna from FIG. 2. the number of antenna elements of the antenna array 11 can, however, be different for the antennas 10 from FIGS. 2 and 3.In particular, FIG. 3 shows, for each antenna element of the antenna 10, a normalized amplitude (grayscale) of the side lobes of this antenna element. The antenna 10 is configured such that side lobes of antenna elements that are seated outside the center of the AESA 11, for example, seated at the edges of the AESA 11, can be attenuated, i.e., have a lower amplitude than side lobes of antenna elements in the center (or in a central region) of the AESA 11. In particular, the side lobes of the antenna elements of the second type 15 can be attenuated compared to side lobes of the antenna elements of the first type 13. The tape ring can be implemented in such a way that, for example, a damping of the side lobes increases from the center or a central region of the AESA 11 to the edges or an edge region of the AESA 11.The tapering thus performed results in the suppression of the side lobes of antenna elements located off-center, i.e., they are most suppressed. The aim here, with optimum side lobe suppression, is to optimally control the amplifiers of the AESA. This can advantageously result in an increased radiated RF energy of the main beam due to higher amplification levels of the amplifiers of the AESA 11 for the main beam, as well as a reduced radar cross section, since a plurality of antenna element types can be combined in an optimized manner. In addition, the scanning loss over the field of view of the AESA 11 can be minimized.Fig. 4 shows a second example of an antenna 10 according to the present invention, which is constructed on the antenna 10 of Fig. 1.The antenna 10 of Fig. 4 includes three different arrangements of antenna elements. The antenna 10 comprises a first arrangement 12 of antenna elements of the first type 13 and a second arrangement 14 of antenna elements of the second type 15, as already the antenna from FIG. 1.The first type antenna elements 13 here are broadside antenna elements, the second type antenna elements 15 are end-line antenna elements, and the third type antenna elements 22 are Yagi antenna elements. The antenna elements of the third type 22 are arranged between the antenna elements of the first type 13 and the antenna elements of the second type 15, as already shown in FIG. 2. The third type antenna elements 22 of the third array 21 are arranged around the first array 12 and the second type antenna elements 15 of the second array 14 are arranged around the third array 22. The first arrangement 12 can be arranged in the center (or in a central region) of the antenna array 11, the third arrangement can be arranged outside the center of the antenna array 11 and around the center (for example in a central or intermediate region of the antenna array 11), and the second arrangement 14 can be arranged at the edges of the antenna array 11 (or in an outer region or edge region of the antenna array 11).FIG. 5 shows a radiation characteristic of an antenna 10 having an AESA as the antenna array 11 according to the second example. The emission characteristic in all three spatial directions is shown. It can be seen that the suppression of side lobes achieves an extremely directional emission of the AESA 11, i.e. a very narrow main beam. This also enables a smaller radar cross section.FIG. 6 again shows the signal levels (amplitudes) of side lobes for antenna elements at different positions of the AESA 11 of an antenna 10 according to the second example. The antenna 10 of Fig. 6 also has three different arrangements of antenna elements of first type 13, second type 15 and third type 22, respectively, which types are as in the antenna 10 according to the second example shown in Fig. 4. The number of antenna elements is different from the antenna 10 of FIG. 4.FIG. 7 demonstrates how, for an antenna 10 with an AESA 11 as antenna array and with three arrangements of antenna elements, the antenna elements of the first type 13, the second type 15 and the third type 22 can be chosen in an advantageous manner. This applies, for example, to the antenna 10 of FIG. 2 or the antenna 10 of FIG. 4, but is applicable to any such antenna 10.In particular, Figure 7 shows that the antenna elements of the arrays 14 and 21 are chosen such that the arrays have different radiation angles with respect to a plane of the AESA. It can be seen that the first type antenna elements 13 of the first arrangement 12 are configured to radiate out of the plane of the AESA 11 (e.g. perpendicular to the plane of the AESA 11), the second type antenna elements 15 of the second arrangement 14 are configured to radiate into the plane of the AESA 11, and the third type antenna elements 22 of the third arrangement 21 are configured to radiate at one or more angles to the plane of the AESA 11.As a result, the influences of the individual antenna element types on the radiation characteristic of the entire antenna array 11 can be optimized. Lower sidelobe signal levels can be achieved by such a combination of different types of antenna elements having different individual radiation properties - preferably in combination with the above described tapering, i.e. attenuating sidelobes of outer antenna elements.Fig. 8 shows a third example of an antenna 10 according to the present invention, which is constructed on the antenna 10 of Fig. 1.The antenna 10 of Fig. 2 includes two different arrangements of antenna elements. The antenna 10 includes a first array 12 of first type antenna elements 13 and a second array 14 of second type antenna elements 15, like the antenna of Figure 1.The first type antenna elements 13 are Yagi antenna elements and the second type antenna elements 15 are mono-cone antenna elements. The first arrangement 12 is arranged in the center of the antenna array 11 or a central region of the antenna array 11, while the second arrangement 14 is arranged in an outer region or an edge region of the antenna array 11. The second assembly 14 is disposed about the first assembly 12.Figure 9 shows a method 90 in accordance with the present invention. The method 90 is configured to operate an antenna 10 as described above. For this purpose, the method 90 has at least one first step 91 of operating the first arrangement 12 of antenna elements of the first type 13, which are arranged in the center (or a central region) of the antenna array 11, wherein the first arrangement 12 radiates out of the plane of the antenna array 11 during operation. Furthermore, the method 90 has a second step 92 of operating the second arrangement 14 of antenna elements of the second type 15 which are arranged at the edges of the antenna array 11 (or an outer region or edge region of the antenna array 11) around the antenna elements of the first type 13, wherein the second arrangement 14 radiates into the plane of the antenna array 11 during operation.In summary, the advantages of the present invention are a larger antenna field of view, a lower scanning loss over the entire field of view of antenna 10, a higher efficiency of antenna 10, a higher efficiency of antenna 10, lower sidelobe levels of radiation of antenna 10, and a lower radar cross-section.In both the claims and the description of the present invention, the word "comprise" or "have" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single element can fulfil the functions of several units or articles mentioned in the claims. The mere fact that certain measures are recited in the various dependent claims does not mean that a combination of these measures cannot be used in an advantageous embodiment.

Claims

Antenna (10) for communication and / or for radar and / or for electronic assistance measures, wherein the antenna (10) comprises: an antenna array (11) which comprises at least a first arrangement (12) of antenna elements of the first type (13) and a second arrangement (14) of antenna elements of the second type (15).The antenna (10) of claim 1, wherein the first array (12) is disposed at the center of the antenna array (11), and the second array (14) is disposed around the first array (12).Antenna (10) according to claim 1 or 2, wherein the first type antenna elements (13) of the first arrangement (12) are configured to radiate out of the plane of the antenna array (11) and the second type antenna elements (15) of the second arrangement (14) are configured to radiate into the plane of the antenna array (11).Antenna (10) according to one of Claims 1 to 3, wherein the antenna array (11) furthermore has a third arrangement (21) of antenna elements of the third type (22).The antenna (10) of claims 2 and 4, wherein the third array (21) is disposed around the first array (12) and the second array (14) is disposed around the third array (21).Antenna (10) according to claim 5, wherein the third type antenna elements (22) of the third arrangement (21) are configured to radiate at an angle to the plane of the antenna array (11).Antenna (10) according to any of claims 1 to 6, wherein the first type antenna elements (13), the second type antenna elements (15) and, if present, the third type antenna elements (22) are different from each other and are each selected from the group consisting of: broadside antenna elements; end-line antenna elements; yagi antenna elements; pyramid antenna elements; vivaldi antenna elements; butterfly antenna elements; fan antenna elements; patch antenna elements; helix antenna elements; monoconus antenna elements; sinusoidal antenna elements; camouflage antenna elements.The antenna (10) of any of claims 1 to 7, wherein the first array (12) is a broadside array and the second array (14) is an end-fire array.The antenna (10) of any of claims 1 to 7, wherein the first array (12) comprises Yagi antenna elements as the first type antenna elements (13) and the second array (14) comprises mono-cone antenna elements as the second type antenna elements (15).The antenna (10) according to any one of claims 4 to 7, wherein the first array (12) has wide-side antenna elements as the first type antenna elements (13), the second array (14) has end-fire antenna elements as the second type antenna elements (15), and the third array (21) has Yagi antenna elements or pyramid antenna elements as the third type antenna elements (22).Antenna (10) according to one of Claims 1 to 10, wherein the antenna (10) is configured to damp side lobes from outside the center of the antenna array (11) or antenna elements arranged at the edges of the antenna array (11), respectively, during operation of the antenna (10).The antenna (10) of any of claims 1 to 11, wherein the antenna (10) is configured for use in an aircraft or a flying platform.Antenna (10) according to any of claims 1 to 11, wherein the antenna (10) is adapted for use in a ground-based vehicle and / or in a water-based vehicle and / or in a land-based structure.A method (90) of operating an antenna (10) according to any one of claims 1 to 13, the method (90) comprising: operating (91) the first array (12) of first type antenna elements (13) arranged in the centre of the antenna array (11), the first type antenna elements (13) of the first array (12) radiating out of the plane of the antenna array (11) in operation; and operating (92) the second array (14) of second type antenna elements (15) arranged around the first type antenna elements (13), the second type antenna elements (15) of the second array (14) radiating into the plane of the antenna array (11) in operation.The method (90) of claim 14, wherein the method (90) further comprises: attenuating side lobes of the second array (14) compared to side lobes of the first array (12) in operation.

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