Three-dimensional antenna arrangement

Abstract

Three-dimensional antenna arrangement (1) for a device (5) with several transmitting antenna elements (2A) and several receiving antenna elements (2B), wherein the transmitting antenna elements (2A) and the receiving antenna elements (2B) are arranged on a regular three-dimensional grid (3) and a virtual antenna arrangement of virtual antenna elements (4) is obtained by a geometric folding of an arrangement of the transmitting antenna elements (2A) and an arrangement of the receiving antenna elements (2B), wherein a phase difference of the virtual antenna elements (4) of the virtual antenna arrangement is measurable in a third spatial dimension.

Description

[0001] The invention relates to a three-dimensional antenna arrangement and in particular a fractal 3D MIMO antenna arrangement for radar applications. State of the art

[0002] Planar antenna arrays are typically used for MIMO radar systems. Two-dimensional, fractal antenna arrays can be used for the optimization of MIMO radar systems by generating circle-like virtual arrays on a hexagonal grid, as described in DE102020102033 A1.

[0003] A multi-element antenna utilizes the phase shift Δϕ of the transmitting elements arranged in a matrix to achieve beam focusing through interference. The transmitted energy is amplified in the desired direction, while unwanted directions are canceled out by destructive interference. The individual transmitting elements do not require any beam focusing devices.

[0004] However, the angular resolution of planar array antennas decreases with increasing elevation and / or azimuth angles due to aperture projection. Furthermore, excessive spacing between antenna elements in planar array antennas leads to periodic ambiguities that are difficult to resolve during signal processing. Additionally, in planar MIMO configurations, multipath paths with different transmit and receive directions result in undesired ghost destinations. Disclosure of the invention

[0005] According to a first aspect, the invention provides a three-dimensional antenna arrangement with several transmitting antenna elements and several receiving antenna elements, wherein the transmitting antenna elements and the receiving antenna elements are arranged on a regular three-dimensional grid and a virtual antenna arrangement of virtual antenna elements is obtained by a geometric folding of an arrangement of the transmitting antenna elements and an arrangement of the receiving antenna elements, wherein a phase difference of the virtual antenna elements of the virtual antenna arrangement is measurable in a third spatial dimension.

[0006] A 3D MIMO arrangement of the antenna elements makes it possible to measure the phase difference of the antenna elements of the virtual antenna array in an additional third spatial dimension. This also allows the wave vector of the transmitted and received waves to be determined in three dimensions.

[0007] The antenna arrangement according to the invention also makes it possible to achieve a constant angular resolution over a very wide angular range in azimuth and / or elevation (>180°) due to the three-dimensional arrangement of the transmitting antenna elements and the receiving antenna elements.

[0008] The three-dimensional antenna arrangement according to the invention allows for the unambiguous classification and filtering of ambiguities, which in turn enables an increase in the element spacing between antenna elements. This allows the angular resolution of a MIMO radar or other device that processes the received signals from the three-dimensional antenna arrangement to be improved with the same number of transmitting and receiving antenna elements.

[0009] At the same time, the inventive approach allows direct paths to be distinguished from multipath paths with different transmit and receive directions and filtered, thereby reducing ghost destinations.

[0010] In one possible embodiment of the three-dimensional antenna arrangement according to the invention, the transmitting antenna elements and the receiving antenna elements each have a fractal arrangement of the antenna elements.

[0011] A fractal antenna array is a configuration of antenna elements that utilizes the principles of fractal geometry to achieve specific advantages in antenna technology. Fractal geometry is characterized by structures that are self-similar and often complex, although they consist of simple, repeating patterns.

[0012] Fractal antennas have a structure that is similar across different scales. This means that parts of the antenna look similar to the entire antenna, only on a smaller scale. Due to the fractal structure, the antenna arrangement according to the invention can be designed more compactly, which is particularly important in applications where space is a factor, such as in mobile devices.

[0013] The three-dimensional fractal arrangement of antenna elements on an optimal regular grid maximizes the distance between ambiguities for a given number of transmitting and receiving antenna elements. At the same time, coupling and mutual shadowing of the antenna elements are avoided.

[0014] In one possible embodiment, the fractal arrangement of the antenna elements allows for a simple realization of the three-dimensional arrangement of the antenna elements based on a planar antenna arrangement with attached linear waveguides, which can be realized, among other things, using waveguide technology.

[0015] Furthermore, in a possible embodiment with a fixed feed network, antenna elements with a wide radiation pattern in azimuth and / or elevation can be realized.

[0016] In one possible embodiment of the three-dimensional antenna arrangement according to the invention, the three-dimensional grid has a face-centered cubic FCC grid.

[0017] In the face-centered cubic (FCC) lattice, the antenna elements are located at the corners and in the center of each of the six faces of a cube in the three-dimensional lattice. Each antenna element on a face is shared with neighboring cubes of the lattice, meaning that each antenna element on a face belongs to two cubes of the lattice.

[0018] The face-centered cubic FCC grid is characterized by a high packing density, allowing a large number of antenna elements to be accommodated in a given volume of the three-dimensional antenna arrangement.

[0019] In one possible embodiment of the three-dimensional antenna arrangement according to the invention, the three-dimensional grid has an HCP grid.

[0020] In hexagonal close-packed (HCP) antennas, the antenna elements are arranged in a hexagonal structure, with each element surrounded by twelve other elements. The elements are stacked in two layers: a first hexagonal layer followed by a second hexagonal layer oriented to fill the gaps in the first.

[0021] The HCP grid is also characterized by a high packing density, so that a large number of antenna elements can be accommodated in a given volume of the three-dimensional antenna arrangement.

[0022] In one possible embodiment of the three-dimensional antenna arrangement according to the invention, the transmitting antenna elements and / or the receiving antenna elements form a tetrahedron consisting of at least four antenna elements in the three-dimensional grid.

[0023] In one possible embodiment of the three-dimensional antenna arrangement according to the invention, the virtual antenna arrangement resulting from spatial folding of the tetrahedral arrangement of the transmitting antenna elements and the tetrahedral arrangement of the receiving antenna elements forms a Sierpinski tetrahedron.

[0024] A Sierpinski tetrahedron is a geometric figure created by repeatedly dividing and subtracting parts of a regular tetrahedron. Despite its complex fractal antenna elements, the antenna arrangement according to the invention can be easily manufactured in this embodiment because it is based on simple geometric rules. In one embodiment, a Sierpinski triangle antenna, based on the Sierpinski triangle fractal, is used for the fractal antenna arrangement. This antenna arrangement is particularly useful in telecommunications applications as well as in radar and satellite systems, where it is important to support multiple frequencies and minimize the physical size of the antenna arrangement.

[0025] In one possible embodiment of the three-dimensional antenna arrangement according to the invention, the transmitting antenna elements and / or the receiving antenna elements are arranged rotated about one of the three spatial axes.

[0026] In one possible embodiment of the three-dimensional antenna arrangement according to the invention, the three-dimensional antenna arrangement comprises a three-dimensional MIMO (Multiple Input Multiple Output) antenna arrangement.

[0027] In one possible embodiment of the three-dimensional antenna arrangement according to the invention, a wave vector of the emitted waves and the received waves can be determined three-dimensionally by means of the virtual antenna arrangement.

[0028] According to a further aspect, the invention provides a radar device with a three-dimensional antenna arrangement comprising several transmitting antenna elements and several receiving antenna elements, wherein the transmitting antenna elements and the receiving antenna elements are arranged on a regular three-dimensional grid and a virtual antenna arrangement of virtual antenna elements is obtained by a geometric folding of an arrangement of the transmitting antenna elements and an arrangement of the receiving antenna elements, wherein a phase difference of the virtual antenna elements of the virtual antenna arrangement is measurable in a third spatial dimension.

[0029] According to a further aspect, the invention provides a communication device with a three-dimensional antenna arrangement comprising multiple transmitting antenna elements and multiple receiving antenna elements, wherein the transmitting antenna elements and the receiving antenna elements are arranged on a regular three-dimensional grid and a virtual antenna arrangement of virtual antenna elements is obtained by a geometric folding of an arrangement of the transmitting antenna elements and an arrangement of the receiving antenna elements, wherein a phase difference of the virtual antenna elements of the virtual antenna arrangement is measurable in a third spatial dimension.

[0030] The above embodiments and further developments can be combined with one another as appropriate. Further possible embodiments, further developments, and implementations of the invention also include combinations of features of the invention described previously or subsequently with regard to the exemplary embodiments, even if not explicitly mentioned. In particular, those skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the present invention. The present invention is explained in more detail below with reference to the exemplary embodiments shown in the schematic figures of the drawings.

[0031] They show: Fig. 1A to 1D wave vectors for different scenarios; Fig. 2A to 2C different possible grids for placing antenna elements in a three-dimensional antenna arrangement; Fig. 3 a tetrahedron with four vertices for providing antenna elements; Fig. 4A, Fig. 4B a Sierpinski tetrahedron as a possible embodiment of a fractal arrangement of triangular antenna elements; Fig. 5A, Fig. 5B a Sierpinski tetrahedron as a possible embodiment of a fractal arrangement of cube-shaped antenna elements; Fig. 5C a possible implementation of a signal feed to a fractal arrangement of antenna elements; Fig. 6A to 6D a planar MIMO array with four transmit antenna elements and four receive antenna elements; Fig. 7A to 7C have a virtual group factor for a square arrangement of the antenna elements; Fig. 8A to 8C a virtual group factor with increased element spacing between the antenna elements; Fig. 9A to 9D a fractal MIMO array with four transmit antenna elements and four receive antenna elements resulting from the displacement of two transmit antenna elements and two receive antenna elements of the planar MIMO array in the z-direction according to an embodiment of the antenna arrangement according to the invention; Fig. 10A to 10C a virtual group factor of the in Fig. 9 fractal antenna arrangement shown; Fig. 11A to 11C a virtual group factor with an increased element spacing between the antenna elements in the Fig. 9 fractal antenna arrangement shown; Fig. 12A to 12D one by rotation of the in Fig. The fractal antenna arrangement shown in Figure 9 represents a further possible embodiment of an antenna arrangement according to the invention; Fig. 13A to 13C a virtual group factor of the in Fig. 12 fractal antenna arrangements shown; Fig. 14A to 14C a virtual group factor of the in Fig. 12 fractal antenna arrangements shown in another plane; Fig. 15A to 15C a virtual group factor with an increased element spacing between the antenna elements in the Fig. 12 fractal antenna arrangements shown; Fig. 16A, Fig. Figure 16B shows an optimal regular scanning grating, such as can be used in the antenna arrangement according to the invention, and an associated reciprocal grating in the 3D spatial frequency space; Fig. Figures 17A to 17F show a planar arrangement of antenna elements and a fractal Sierpinski tetrahedral arrangement of antenna elements according to a possible embodiment of the antenna arrangement according to the invention; Fig. Figures 18A to 18F show further representations of possible antenna element arrangements to illustrate a possible embodiment of the antenna arrangement according to the invention; Fig. Figures 19A to 19C show a combination of a basic arrangement to illustrate an antenna arrangement according to the invention; Fig. 20A to 20C show further variants of possible antenna element arrangements; Fig. Figures 21A to 21C show a combination of a basic arrangement to illustrate an antenna arrangement according to the invention; Fig. 22A, Fig. 22B shows possible implementation examples of the in the Fig. 18 fractal 3D MIMO antenna arrangements shown; Fig. 23 a schematic representation of a device which has a three-dimensional antenna arrangement according to the invention.

[0032] The accompanying drawings are intended to provide a further understanding of the embodiments of the invention. They illustrate embodiments and, in conjunction with the description, serve to explain the principles and concepts of the invention. Other embodiments and many of the advantages mentioned will become apparent with reference to the drawings. The elements of the drawings are not necessarily shown to scale.

[0033] In the figures of the drawing, identical, functionally equivalent and similarly acting elements, features and components - unless otherwise stated - are each provided with the same reference symbols.

[0034] According to a first aspect, the invention provides a three-dimensional antenna arrangement 1 with antenna elements 2. The three-dimensional antenna arrangement 1 can be provided in a device 5, as described in Fig. 23 is shown schematically.

[0035] The antenna elements 2 of the antenna arrangement 1 comprise transmitting antenna elements 2A and receiving antenna elements 2B. The transmitting antenna elements 2A and the receiving antenna elements 2B are arranged on a regular three-dimensional grid 3. A virtual antenna arrangement of virtual antenna elements 4 results from a geometric folding of an arrangement of the transmitting antenna elements 2A and an arrangement of the receiving antenna elements 2B. A phase difference of the virtual antenna elements 4 of the virtual antenna arrangement comprising the virtual antenna elements 4 is measurable in a third spatial dimension and can be evaluated by a signal processing unit 6 of the device 5.

[0036] A 3D MIMO arrangement of the antenna elements 2 makes it possible to measure the phase difference of the antenna elements 4 of the virtual antenna array in an additional third spatial dimension. This also allows the wave vector of the transmitted and received waves to be determined in three dimensions.

[0037] The antenna arrangement 1 according to the invention further enables a constant angular resolution to be achieved over a very wide angular range in azimuth and / or elevation (>180°) due to the three-dimensional arrangement of the transmitting antenna elements 2A and the receiving antenna elements 2B.

[0038] The three-dimensional antenna arrangement 1 according to the invention allows for the unambiguous classification and filtering of ambiguities, which in turn enables an increase in the element spacing between antenna elements 2. This allows the angular resolution of a MIMO radar device or other device that processes the received signals of the three-dimensional antenna arrangement 1 to be improved with the same number of transmitting antenna elements 2A and receiving antenna elements 2B.

[0039] At the same time, the inventive approach allows direct paths to be distinguished from multipath paths with different transmit and receive directions and filtered, thereby reducing ghost destinations.

[0040] In one possible embodiment of the three-dimensional antenna arrangement 1 according to the invention, the transmitting antenna elements 2A and the receiving antenna elements 2B each have a fractal arrangement of the antenna elements.

[0041] The three-dimensional fractal arrangement of antenna elements 2 on an optimal regular grid 3 maximizes the distance between ambiguities for a given number of transmitting antenna elements 2A and receiving antenna elements 2B. At the same time, coupling and mutual shading of the antenna elements 2 are avoided.

[0042] In one possible embodiment, the fractal arrangement of the antenna elements 2 enables a simple realization of the three-dimensional arrangement of the antenna elements 2 based on a planar antenna arrangement with attached linear waveguides, which can be realized, among other things, using waveguide technology.

[0043] Furthermore, in a possible embodiment with a fixed feed network, antenna elements 2 with a wide radiation pattern in azimuth and / or elevation can be realized.

[0044] In one possible embodiment of the three-dimensional antenna arrangement 1 according to the invention, the three-dimensional grid 3 has a face-centered cubic FCC grid.

[0045] In one possible embodiment of the three-dimensional antenna arrangement 1 according to the invention, the three-dimensional grid 3 has an HCP grid.

[0046] In one possible embodiment of the three-dimensional antenna arrangement 1 according to the invention, the transmitting antenna elements 2A and / or the receiving antenna elements 2B form a tetrahedron consisting of at least four antenna elements 2 in the three-dimensional grid 3.

[0047] In one possible embodiment of the three-dimensional antenna arrangement 1 according to the invention, the antenna is formed by spatial folding of the tetrahedral arrangement of the transmitting antenna elements 2A and the tetrahedral Sierpinski tetrahedron.

[0048] A Sierpinski tetrahedron is a geometric figure created by repeatedly dividing and removing parts of a regular tetrahedron. The Sierpinski tetrahedron can be constructed and implemented as follows.

[0049] One begins with a regular tetrahedron, which consists of four equilateral triangles.

[0050] Each of the four equilateral triangles of the tetrahedron is divided into four smaller equilateral triangles by bisecting one edge of each and connecting the new vertices. This results in a total of 4 * 4 = 16 smaller triangles.

[0051] The above step is repeated for each of the newly created triangles, subdividing each one into four smaller triangles. This results in increasingly smaller and more detailed versions of the original tetrahedron.

[0052] After several iterations, a pattern emerges that is known as the Sierpinski tetrahedron. It is a self-similar fractal with a three-dimensional tetrahedral structure, where each smaller tetrahedron is a scaled-down version of the original tetrahedron.

[0053] In one possible embodiment of the three-dimensional antenna arrangement 1 according to the invention, the transmitting antenna elements 2A and / or the receiving antenna elements 2B are arranged rotated about one of the three spatial axes.

[0054] In one possible embodiment of the three-dimensional antenna arrangement 1 according to the invention, the three-dimensional antenna arrangement comprises a three-dimensional MIMO antenna arrangement.

[0055] In one possible embodiment of the three-dimensional antenna arrangement 1 according to the invention, a wave vector of the emitted waves and the received waves can be determined three-dimensionally by means of the antenna elements 4 of the virtual antenna arrangement.

[0056] According to a further aspect, the invention provides a radar device with a three-dimensional antenna arrangement 1 with several transmitting antenna elements 2A and several receiving antenna elements 2B, wherein the transmitting antenna elements 2A and the receiving antenna elements 2B are arranged on a regular three-dimensional grid 3 and a virtual antenna arrangement of virtual antenna elements 4 is obtained by a geometric folding of an arrangement of the transmitting antenna elements 2A and an arrangement of the receiving antenna elements 2B, wherein a phase difference of the virtual antenna elements 3 of the virtual antenna arrangement is measurable in a third spatial dimension.

[0057] According to a further aspect, the invention provides a communication device with a three-dimensional antenna arrangement 1 with several transmitting antenna elements 2A and several receiving antenna elements 2B, wherein the transmitting antenna elements 2A and the receiving antenna elements 2B are arranged on a regular three-dimensional grid 3 and a virtual antenna arrangement of virtual antenna elements 4 is obtained by a geometric folding of an arrangement of the transmitting antenna elements 2A and an arrangement of the receiving antenna elements 2B, wherein a phase difference of the virtual antenna elements 4 of the virtual antenna arrangement is measurable in a third spatial dimension.

[0058] Fig. Figure 1A shows wave vectors WV (TX-WV and RX-WV) for a conventional planar MIMO antenna arrangement with ambiguities. Fig. Figure 1B shows wave vectorsWV in asymmetric multipath propagation

[0059] Fig. Figure 1C shows wave vectors for a 3D MIMO antenna array. Fig. Figure 1D shows wave vectors in asymmetric multipath propagation.

[0060] Accordingly Fig. 1A to Fig. In 1D, the wave vectors WV of the direct paths lie on a spherical shell with a radius twice the wave number.

[0061] The planar antenna arrangement measures the projection of the wave vector WV in the plane, which makes it impossible to resolve the 2D periodic ambiguities.

[0062] The three-dimensional antenna arrangement 1 according to the invention, however, can uniquely resolve the 3D periodic ambiguities if they do not lie on the spherical shell. Since the pattern of ambiguities is known and the periodicity exists in the Cartesian spatial directions, ambiguities on the hemispherical shell can also be uniquely resolved. This allows for a significantly larger spacing of the antenna elements 2, thereby improving the angular resolution.

[0063] In multipath systems with different transmit and receive directions, the wavenumber vectors are not parallel to each other, as in Fig. 1B and Fig. 1D recognizability means that these paths lie within the hemisphere and can therefore be identified. This method is significantly more robust compared to multipath estimation based on the amplitude ratios of the directional characteristics.

[0064] To filter out ambiguities and asymmetric multipath paths, the three-dimensional spatial frequency spectrum can be calculated using a 3D FFT of the IF signals based on the virtual antenna positions, and the hemispherical shell can be evaluated for arbitrary azimuth and elevation directions. This form of beamforming can be efficiently implemented directly onto an arbitrary grating in azimuth and elevation using a NUFFT. Alternatively, an angle estimation can be performed after range-Doppler processing, which takes the additional spatial frequency dimension into account.

[0065] The Fast Fourier Transform (FFT) is an efficient algorithm for calculating the Discrete Fourier Transform (DFT) and its inverse. A 3D FFT extends this algorithm to three-dimensional data, meaning the Fourier transform is performed along all three spatial dimensions. Zero Frequency (IF) or Intermediate Frequency (IF) signals are signals that have been downconverted from a high carrier frequency to a lower, more manageable frequency.

[0066] To calculate a three-dimensional spatial frequency spectrum, the following steps can be performed in a possible implementation of the device according to the invention. First, three-dimensional IF signals are collected from antenna elements 2, which are arranged in a grid 3 of points in the three spatial dimensions (x, y, z). If necessary, the obtained IF signals can be processed to reduce noise or to normalize the data. A 3D FFT is applied to the 3D data to calculate the frequency spectrum in all three dimensions. This transforms the data from spatial space (spatial position) to frequency space (spatial frequencies). For each voxel (volume pixel) in the 3D space, a Fourier transform can be calculated, which decomposes the signal into a sum of sine and cosine components.The resulting three-dimensional frequency spectrum shows the distribution of the frequency components of the original signal in all three spatial dimensions. This spectrum can be used to identify features in the original 3D data space. Signal processing can be performed by a processor or an ASIC of a signal processing unit 6 of a device 5, as shown schematically in Figure 1. Fig. 23 is shown.

[0067] In one possible embodiment of the antenna arrangement 1 according to the invention, the concept of a fractal antenna arrangement can be extended to three dimensions in order to additionally measure the phase difference in a third spatial dimension.

[0068] Preferably, a regular three-dimensional grid 3 is used. This grid 3 preferably has the densest possible sphere packing in order to maximize the spacing of ambiguities in the spatial frequency space of the arrangement. In one possible embodiment, this property is fulfilled by a face-centered cubic (FCC) grid, as described in Fig. 2A is represented, or by a hexagonal closest packing (HCP), as shown in Fig. 2C is shown. Depending on the application and available space, other three-dimensional lattice structures can also be used.

[0069] Both in the Fig. 2A, Fig. The lattices 3 shown in Figure 2C are closely related to each other and generate an arrangement of ambiguities in the spatial frequency domain corresponding to their reciprocal lattice, the body-centered cubic (BCC) lattice, as shown in Figure 2C. Fig. 2C is shown.

[0070] Analogous to a triangular arrangement in 2D (2-simplex), a basic arrangement of four antenna elements 2 in the shape of the vertices of a tetrahedron (3-simplex) can be used in the three-dimensional antenna arrangement 1 according to the invention. For this purpose, the antenna elements 2 are mounted on an FCC grid ( Fig. 2A) or on an HCP grid ( Fig. 2C) arranged, wherein all antenna elements 2 preferably have the same distance from each other.

[0071] The in Fig. 3 depicted tetrahedra T with 2 2 =4 can be considered an efficient subset of the equidistant sampling cube with 2 3 =8 corners are considered.

[0072] Larger arrays with 4n antenna elements in the form of the Sierpiński Tetrahedron ST can be generated by self-similar arrangement of the tetrahedron array, as shown in the Fig. 4A, Fig. Figure 4B shows that this self-similar or fractal arrangement of the antenna elements 2 also lies on the FCC grid or the HCP grid, respectively. As already shown in Fig. The arrangement of the three depicted tetrahedra T possesses the unique property that the projections onto three orthogonal Cartesian axes correspond to a square arrangement with a square grid of 4n elements. A Sierpiński tetrahedron ST with two projection views results in a square arrangement for the principal Cartesian axes.

[0073] Each tetrahedron here corresponds to an antenna element arrangement, as found in the Fig. 4A, Fig. Figure 4B shows that the angular resolution and sidelobe pattern of the fractal antenna arrangement correspond to this square arrangement. The arrangement in the form of the Sierpiński tetrahedron ST thus extends the square arrangement by 2 n *2 nelements into the third dimension, thereby achieving an optimal thinned spatial scan of a cube 2 n * 2 n * 2 n with only 2 n * 2 n Antenna elements. The Fig. 5A, Fig. Figure 5B shows a Sierpiński tetrahedron ST with cubes ( Fig. 5B) instead of triangles ( Fig. 5A).

[0074] This property also allows for implementation by extending a planar array antenna with attached straight waveguides, such as circular waveguides in the form of a milled plate with holes of varying depths or a metallized injection-molded component. Alternatively, the feed can also be in the form of an H-tree fractal with branches twisted relative to each other, as in Fig. 5C is shown.

[0075] The virtual MIMO array is created by folding the transmit and receive arrays. Here too, by appropriately scaling the element spacing, arrays in the form of a Sierpiński tetrahedron ST with 4 elements can be achieved. n transmitting elements and 4 m Receiving elements for a Sierpinski tetrahedron with 4 (n+m) Virtual antenna positions can be combined. Furthermore, the fractal arrangements can be combined as subgroups with conventional planar arrangements to obtain additional degrees of freedom in the design.

[0076] One possible approach to generating the Sierpiriski tetrahedral antenna array is as follows: • Providing a first tetrahedral arrangement with four antenna elements spaced d apart. • Providing a second tetrahedral array with four antenna elements at a scaled spacing d4=2d. • Performing a spatial folding of both tetrahedron arrangements, resulting in a Sierpiriski tetrahedron ST with 4*4=16 antenna elements.

[0077] This can be generalized as follows: • Provision of an initial Sierpiński tetrahedron with 4 n elements and a distance d. • Provide a second Sierpiński tetrahedron with 4 m elements and distance d4. • Performing a spatial folding of both arrangements, resulting in a Sierpiński tetrahedron ST with 4 (n+m) elements and distance d results.

[0078] Further variations of the inventive antenna arrangement 1 result from an optional rotation of the arrangements by 90° (around the x, y, or z axis). This optional rotation allows for the creation of alternative 3D fractal arrangements in each combination, which, however, exhibit the same projection properties as the Sierpiriski tetrahedron ST and possess the Hausdorff dimension 2.

[0079] The Fig. 6A to 6D represent a planar MIMO array with four transmit and four receive elements spaced 0.5λ apart. The positions of the transmit antenna elements 2A (tx pos), the receive antenna elements 2B (rx pos), and the virtual antenna elements 4 (virtual pos) are indicated.

[0080] Fig. 7A, Fig. 7B, Fig. Figure 7C illustrates a virtual group factor GF of the quadratic arrangement for a target at elevation 0° and azimuth 0°. The group factor has no resolution in the kz direction. The angular resolution decreases with increasing azimuth and elevation angle due to the plane aperture. The uniqueness range is 2k in the kx and ky directions, thus enabling unambiguous angle determination.

[0081] If the element spacing is increased to 1.5λ, the ambiguities within the hemisphere with radius 2k can no longer be resolved as in the Fig. 8A, Fig. 8B, Fig. 8C can be seen. In the kx-ky plane, it becomes clear that there are now eight ambiguities within the hemisphere.

[0082] Fig. Figures 9A to 9D show a fractal MIMO array 1 with four transmit antenna elements and four receive antenna elements, achieved by shifting two transmit and two receive elements of the planar array in the z-direction. The positions of the transmit antenna elements 2A (tx pos), the receive antenna elements 2B (rx pos), and the virtual antenna elements 4 (virtual pos) are shown.

[0083] Fig. 10A, Fig. 10B, Fig. Figure 10C shows the virtual group factor GF of the fractal antenna array for a target at elevation 0° and azimuth 0° (kx=0, ky=0, kz=2k). The group factor has identical resolution in the kx, ky, and kz directions. The angular resolution is therefore constant for all directions and is identical to the minimum resolution of the planar array with the same number of antenna elements. The spacing of the ambiguities is also identical in the kx, ky, and kz directions and is 2k.

[0084] If the element spacing is increased to 1.5λ, the ambiguities within the hemisphere with radius 2k can be filtered out using the kz component, as in the Fig. 11A, Fig. 11B, Fig. 11C is recognizable.

[0085] The angular resolution is improved by a factor of 3 through scaling in azimuth and elevation. Ambiguities that partially intersect the hemispherical shell 2k reduce the sidelobe spacing of the virtual group factor. Therefore, here too, the improved angular resolution is achieved at the cost of a poorer sidelobe spacing. Compared to the planar square array, the ratio is significantly better for the fractal 3D antenna array 1, since point-like ambiguities must intersect the hemispherical shell 2k. In the planar array, line-like ambiguities always intersect the hemispherical shell if the element spacing is greater than 0.5 λ.

[0086] An alternative implementation can be achieved by rotating the fractal antenna arrangement. Now, three of the four elements lie in the z=0 plane, and only the element at x=y=0 rises above the plane.

[0087] To better decouple the transmitting and receiving arrangements, these can also be shifted relative to each other without fundamentally changing the virtual arrangement, as in the Fig. Figures 12A to 12D show the positions of the transmitting antenna elements 2A (tx pos), the receiving antenna elements 2B (rx pos), and the virtual antenna elements 4 (virtual pos).

[0088] Fig. 13A, Fig. 13B, Fig. 13C represents the virtual group factor GF of the rotated antenna array 1 at an element spacing of 0.5λ. In general, the entire sphere 2k can also be evaluated for the 3D arrays if corresponding antenna elements 2 have a radiation pattern > 180° in azimuth and / or elevation. The 3D phase evaluation also allows for a clear distinction between the positive and negative kz components, as in the Fig. 14A, Fig. 14B, Fig. 14C is recognizable.

[0089] Fig. 15A, Fig. 15 B, Fig. Figure 15C shows a virtual group factor GF of the rotated antenna array 1 at an element spacing of 1.5λ. Here, a hexagonal arrangement of the ambiguities is evident in the kz=0 and ky=0 planes. In the kx=0 plane, the ambiguities are arranged in the form of a rectangular grid.

[0090] Overall, the fractal virtual group factor GF shows intersection planes of the ambiguities of the BCC grid, which maximizes the distance of the ambiguities and thus represents an optimum.

[0091] Fig. 16A, Fig. Figure 16B shows an optimal regular scanning grating, such as can be used in the antenna arrangement 1 according to the invention, and an associated reciprocal grating in the 3D spatial frequency space.

[0092] Fig. 16A represents an optimal regular scanning grid in 3D. The in Fig. 16 A shown face-centered cubic lattice (FCC) 3 corresponds to the closest packing of spheres.

[0093] Fig. Figure 16B shows a reciprocal grating in 3D spatial frequency space, which corresponds to a body-centered cubic (BCC) grating as described in Fig. Figure 2B shows the distance between the six nearest lattice lobes. This distance is identical and therefore maximum.

[0094] The Fig. 17A to 17F show a planar arrangement of antenna elements ( Fig. 17A to 17C) and a fractal Sierpinski tetrahedral arrangement ( Fig. 17C to 17F) of antenna elements according to a possible embodiment of the antenna arrangement according to the invention 1.

[0095] The Sierpiński terahedron ST achieves a sparse scanning of the FCC grating. The orthogonal projections (x,y,z) correspond to the planar square arrangement. Mutual shadowing is minimized. Since each antenna element 2 is visible from the six orthogonal directions, the antenna arrangement 1 according to the invention offers an advantage over a conventional conformal antenna arrangement with regard to mutual shadowing perpendicular to the main beam direction.

[0096] Fig. Figure 17A shows a square planar arrangement with four antenna elements. Fig. Figure 17B shows a square planar arrangement with sixteen antenna elements.

[0097] Fig. Figure 17C shows a square planar arrangement with sixty-four antenna elements.

[0098] Fig. Figure 17D shows a first-order Sierpinski tetrahedron ST with four antenna elements 2 to illustrate a possible embodiment of the antenna arrangement 1 according to the invention.

[0099] Fig. Figure 17E shows a second-order Sierpinski tetrahedron ST with sixteen antenna elements 2 to illustrate a possible embodiment of the antenna arrangement 1 according to the invention.

[0100] Fig. Figure 17F shows a third-order Sierpinski tetrahedron ST with sixty-four antenna elements 2 to illustrate a possible embodiment of the antenna arrangement 1 according to the invention.

[0101] The Fig. Figures 18A to 18F show further representations of possible antenna element arrangements to illustrate a possible embodiment of the antenna arrangement according to the invention 1.

[0102] Fig. Figure 18A shows a planar arrangement of four transmitting antenna elements.

[0103] Fig. Figure 18B shows a planar arrangement of four receiving antenna elements.

[0104] Fig. Figure 18C shows a planar arrangement of 16 virtual antenna elements, which are formed by spatial folding of the elements in the Fig. 18A and Fig. 18B depicted real antenna elements.

[0105] Fig. Figure 18D shows a three-dimensional arrangement of four transmitting antenna elements 2A of a transmitting antenna array.

[0106] Fig. Figure 18E shows a three-dimensional arrangement of four receiving antenna elements 2B of a receiving antenna array.

[0107] Fig. Figure 18F shows a three-dimensional arrangement of sixteen virtual antenna elements 4, which are formed by spatial folding of the elements in the Fig. 18D and Fig. 18E shown real antenna elements 2A, 2B, to illustrate a possible embodiment of a three-dimensional antenna arrangement according to the invention 1.

[0108] The Fig. Figures 19A to 19C show a combination of a basic arrangement to illustrate an antenna arrangement according to the invention. Fig. Figures 19A to 19C show a combination of the basic arrangement with a conformal Rx arrangement for better resolution in azimuth (x-direction) and main beam direction in z-direction.

[0109] Fig. Figure 19A shows an arrangement of four transmitting antenna elements 2A in a 3D transmitting antenna array.

[0110] Fig. Figure 19B shows an arrangement of four receiving antenna elements 2B in a 3D receiving antenna array.

[0111] Fig. Figure 19C shows a 3D virtual antenna array with sixteen virtual antenna elements 4 to illustrate a possible embodiment of a three-dimensional antenna arrangement 1 according to the invention.

[0112] Fig. Figures 20A to 20C show further variants of possible antenna element arrangements.

[0113] Fig. Figure 20A shows an arrangement of four transmitting antenna elements 2A in a 3D transmitting antenna array.

[0114] Fig. Figure 20B shows an arrangement of four receiving antenna elements 2B in a 3D receiving antenna array.

[0115] Fig. Figure 20C shows a 3D virtual antenna array with sixteen virtual antenna elements 4 to illustrate a possible embodiment of a three-dimensional antenna arrangement 1 according to the invention. A variant with a planar Rx arrangement and better resolution in azimuth (x-direction) is shown, with the main beam direction being in the y-direction.

[0116] Fig. Figures 21A to 21C show a combination of a basic arrangement to illustrate an antenna arrangement 1 according to the invention. One can recognize a combination of the basic arrangement with a linear Rx arrangement in diagonal orientation, better resolution in azimuth (x=y-diagonal), wherein the main beam direction is in the z-direction.

[0117] Fig. Figure 21A shows an arrangement of four transmitting antenna elements 2A in a 3D transmitting antenna array.

[0118] Fig. Figure 21B shows an arrangement of four receiving antenna elements 2B in a 3D receiving antenna array.

[0119] Fig. Figure 21C shows a 3D virtual antenna array with sixteen virtual antenna elements4 to illustrate a possible embodiment of a three-dimensional antenna arrangement according to the invention 1.

[0120] Fig. 22A, Fig. 22B show possible embodiments of the features described in the Fig. 18 fractal 3D MIMO antenna arrangements shown.

[0121] Fig. 22A, Fig. Figure 22B shows an example of the realization of the fractal 3D MIMO antenna arrangement 1 from Fig. 18 with linear circular waveguides projected from the xy plane. The transmitting arrangement (top) and the receiving arrangement (bottom) can be stacked on top of each other (elevation plane) for better decoupling and reduced mutual shadowing. Feeding can be done from the plane by adding additional waveguides. The added waveguide structure can also be integrated, e.g., as a partially metallized injection-molded part.

[0122] Fig. Figure 23 schematically shows a device 5 with an integrated three-dimensional antenna arrangement 1, in which antenna elements 2 are provided in a three-dimensional grid 3. The device 5 has a signal processing unit 6 for processing the signals received by the antenna arrangement 1 and for providing the signals emitted by the antenna arrangement 1. In one possible embodiment, the three-dimensional antenna arrangement 1 is integrated into a housing of the device 5. Alternatively, the three-dimensional antenna arrangement 1 can be connected to the signal processing unit 6 via an interface.

[0123] The in Fig. The device 5 shown in Figure 23 can be a mobile device, for example a mobile communication device, in particular a mobile telephone (cell phone). The device 5 can also be a radar device or any other device that transmits and / or receives signals via antenna elements.

[0124] Although the present invention has been fully described above with reference to preferred embodiments, it is not limited thereto, but can be modified in many ways. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 102020102033 A1

[0002]

Images