Method and device for determining the elevation angle and azimuth of interferometer direction finders

Abstract

Method for determining the elevation and azimuth angle of an incident electromagnetic wave, in an antenna circuit group (100) with m antenna elements, wherein the antenna elements each have a distance l from their directly adjacent antenna elements, comprising the following steps: a) Measuring the phase values ​​of the antenna elements, b) Forming the phase differences of the phase values ​​of the adjacent antenna elements, c) forming m interferometer arrays each consisting of three adjacent antenna elements, d) forming m virtual, rectangular interferometer arrays by virtually rotating the position of one of the two outer antenna elements of the three adjacent antenna elements of the respective interferometer array such that the distance between the virtually rotated position of one of the two outer antenna elements and the position of its directly adjacent antenna element of the respective interferometer array remains equal to l and such that the virtually rotated position of one antenna element and the positions of the other two antenna elements of the respective interferometer array form the vertices of an isosceles, right-angled triangle, e) Determining the virtual phase difference between the antenna element whose position is virtually rotated and its directly adjacent antenna element of the respective virtual, rectangular interferometer arrangement using the phase differences formed in step c) of the respectively directly adjacent antenna elements of the respective interferometer arrangement and the angle α = 2 π / m , f) Determining the elevation angle and / or the azimuth angle of the respective virtual, rectangular interferometer arrangement using the virtual phase difference and the phase difference of the phase values ​​of the directly adjacent antenna elements of the interferometer arrangement that are not virtually rotated.

Description

[0001] The invention relates to a method and a device for determining the elevation angle and the azimuth of an incident electromagnetic wave in interferometer direction finders.

[0002] In addition to determining the azimuth, interferometer direction finders also allow the calculation of the elevation angle of the incident wave. They belong to the category of direction finders that process directly measured phase differences of the individual, spatially distributed antennas. Various interferometer methods and arrangements are known. For example, [1] describes interferometer principles for various antenna configurations. To determine the azimuth and elevation unambiguously, interferometers require at least three parameters, for example, the phase differences between three antennas. To enable unambiguous phase measurements, the antenna base or the antenna spacing must not be greater than half the wavelength of the highest frequency to be processed. [1] describes an interferometer arrangement with three elements arranged at right angles in the Cartesian coordinate system.In [2] a method for an arrangement with three antennas arranged on an isosceles triangular base is given.

[0003] To improve direction finding accuracy using a larger antenna base, more than three antennas in different arrangements are often used. [1] describes methods for unambiguous azimuth and elevation determination with a large antenna base. In particular, methods and phase determinations for arrangements with antenna spacings smaller or larger than half the wavelength are described.

[0004] A particularly advantageous antenna arrangement is the circular base. By arranging the antennas evenly spaced on the circle, all antennas are treated equally, including in terms of coupling. There are no phase edge effects, as with line or rectangular arrays. To ensure unambiguous phase determination, the antenna spacing in circular arrays must also be less than half the wavelength.

[0005] In [1] and [2], elevation and azimuth calculations for simple antenna arrangements with three elements are explicitly specified. When using a circular base, various methods are available for elevation and azimuth evaluation. Examples include Doppler methods (in [1] from p. 148), correlative direction finding methods, high-resolution direction finding methods, etc. For example, [3] describes an interferometer with switchable antennas on a circular base, using high-resolution methods for evaluation.

[0006] A well-known method for calculating elevation and azimuth is shown using the example of Fig. 1 shown. Fig. Figure 1 shows a schematic plan view of an interferometer with three orthogonally arranged antennas and an antenna base 1. The electromagnetic wave DoA is incident at the azimuth angle ψ and the elevation angle ε.

[0007] Using the measured phase difference angles, Φ1 and Φ2 to Φ0, the elevation can be calculated: ε=arccos[(Φ2−Φ0)2+(Φ1−Φ0)22π1λ], where l is the distance between the directly adjacent antennas and λ is the wavelength of the incident electromagnetic wave DoA.

[0008] The azimuth is: ψ=arctan[Φ2−Φ0Φ1−Φ0] References: [1] - Grabau / Pfaff, radio direction finding technology; pp.173 - 183; [2] - HH Jenkins; Small - Aperture Radio Direction - Finding; pp. 136 - 137 [3] - US 6,989,789 B2, Anne Ferreol et al.;

[0009] DE 3322948 A1 relates to a large base direction finder with circularly arranged antennas. In this large base direction finder, the antennas, arranged equidistantly in a circle, are combined into antenna pairs. These antenna pairs are formed into at least two groups. The phase differences between the signals received by the antennas of each pair are measured. The measured values ​​of the two groups are combined, and the elevation-independent direction of incidence of the signal to be found in the azimuth plane is determined from the resulting values.

[0010] An object of the invention is the particularly efficient determination of the elevation angle and the azimuth angle of an incident wave in an interferometer antenna with m antenna elements arranged in a circular base.

[0011] The problem is solved with the features of the independent patent claims.

[0012] The invention is based on the idea of ​​transforming the measured phase differences of the circular array in such a way that a configuration of several rectangular sub-arrays—interferometer arrays—is created, whose elevation and azimuth are calculated. Subsequently, an average of these bearing values ​​is calculated. The number of sub-arrays depends on the available number of antenna elements.

[0013] The invention relates to a method for determining the elevation and azimuth angle of an incident electromagnetic wave in an antenna circuit group with m antenna elements, wherein the antenna elements each have a distance l from their directly adjacent antenna elements.

[0014] The method comprises the following steps: measuring the phase values ​​of the antenna elements, forming the phase differences of the phase values ​​of the respectively adjacent antenna elements, forming m interferometer arrangements from three adjacent antenna elements each, forming m virtual, right-angled interferometer arrangements by virtually rotating the position of one of the two outer antenna elements of the three adjacent antenna elements of the respective interferometer arrangement such that the distance between the virtually rotated position of one of the two outer antenna elements and the position of its directly adjacent antenna element of the respective interferometer arrangement remains equal to l and such that the virtually rotated position of one antenna element and the positions of the other two antenna elements of the respective interferometer arrangement form the corner points of an isosceles, right-angled triangle.

[0015] Further method steps are determining the virtual phase difference between the antenna element whose position is virtually rotated and its directly adjacent antenna element of the respective virtual, rectangular interferometer arrangement using the phase differences formed in the above step of the respectively directly adjacent antenna elements of the respective interferometer arrangement and the angle α = 2 π / m, as well as determining the elevation angle and / or the azimuth angle of the respective virtual, rectangular interferometer arrangement using the virtual phase difference and the phase difference of the phase values ​​of the directly adjacent antenna elements of the interferometer arrangement that are not virtually rotated.

[0016] An incident electromagnetic wave may be a radio wave, preferably in a frequency range of 1 MHz to 3 GHz.

[0017] The elevation and azimuth angles, or elevation and azimuth for short, together form the radio directionality. An antenna element can be, for example, a directional or direction-finding antenna. The antenna is not limited to a specific design.

[0018] The phase values ​​can be formed by a suitable single-channel phase meter either immediately one after the other or simultaneously by a suitable multi-channel phase meter.

[0019] The phase differences of the phase values ​​of the respective adjacent, ie directly adjacent, antenna elements can be measured sequentially or simultaneously by a device, e.g. a suitable phase differentiator or within a suitable processor unit.

[0020] The formation of m interferometer arrays is achieved by combining three adjacent antenna elements of the antenna array. The angle between the three adjacent antenna elements depends on the total number of antenna elements in the antenna array.

[0021] A virtual, rectangular interferometer arrangement is formed by a corresponding device in which this device virtually rotates the position of one of the two outer antenna elements of the three adjacent antenna elements of the respective interferometer arrangement formed in such a way, i.e. only purely mathematically, not really, e.g. by displacement, that the distance between the virtually rotated position of one of the two outer antenna elements and the position of its directly adjacent antenna element of the respective interferometer arrangement remains the same l. At the same time, this virtual rotation takes place exactly far enough that the virtually rotated position of one antenna element and the positions of the other two antenna elements of the respective interferometer arrangement form the corner points of an isosceles, right-angled triangle.

[0022] This virtual rotation, as well as the determination of the virtual phase difference between the antenna element whose position is virtually rotated and its directly adjacent antenna element of the respective virtual, rectangular interferometer arrangement as well as the determination of the elevation angle and / or the azimuth angle of the respective virtual, rectangular interferometer arrangement can be carried out by a single suitable processor unit or by individual interconnected components.

[0023] In a further embodiment, the elevation angles and / or azimuth angles of all virtual interferometer arrays are summed, and the sum of the elevation angles or azimuth angles is weighted. This weighting can preferably be performed by dividing by the number of virtual interferometer arrays. This corresponds to the case where all antennas are weighted equally. However, individual antenna elements can also be given special consideration by appropriate weighting.

[0024] In a further embodiment, the formation of virtual, rectangular interferometer arrangements, the determination of the virtual phase difference between the two antenna elements, as well as the determination of the elevation angle and / or the azimuth angle of the respective virtual, rectangular interferometer arrangement are carried out only for a number u < m of antenna elements, preferably with l < u < m.

[0025] In a further embodiment, the antenna circuit group consists of 7 antenna elements.

[0026] Furthermore, the invention relates to a device for determining the elevation and azimuth angle of an incident electromagnetic wave in an antenna circuit group with m antenna elements, which is preferably suitable for carrying out the steps of one of the above methods, with a multi-channel receiver which is connected to the m antenna elements and receives the m antenna signals of the m antenna elements, a phase meter which is connected to the multi-channel receiver and measures the phase of the antenna signal of the respective antenna element of the antenna circuit group, a device for forming the phase differences of the phase values ​​of the respectively adjacent antenna elements and a device for forming m interferometer arrangements from three adjacent antenna elements each,

[0027] The device also comprises means for forming m virtual, rectangular interferometer arrays by virtually rotating the position of one of the two outer antenna elements of the three adjacent antenna elements of the respective interferometer array such that the distance between the virtually rotated position of one of the two outer antenna elements and the position of its directly adjacent antenna element of the respective interferometer array remains equal to l and such that the virtually rotated position of one antenna element and the positions of the other two antenna elements of the respective interferometer array form the vertices of an isosceles, right-angled triangle.

[0028] Furthermore, the device comprises a device for determining the virtual phase difference between the antenna element whose position is virtually rotated and its directly adjacent antenna element of the respective virtual, rectangular interferometer arrangement using the above-formed phase differences of the respectively directly adjacent antenna elements of the respective interferometer arrangement and the angle α = 2 π / m, as well as a device for determining the elevation angle and / or the azimuth angle of the respective virtual, rectangular interferometer arrangement using the virtual phase difference and the phase difference of the phase values ​​of the directly adjacent antenna elements of the interferometer arrangement that are not virtually rotated.

[0029] In a further embodiment, the device further comprises a device suitable for summing the elevation angles and / or azimuth angles of all virtual interferometer arrays and weighting the sum of the elevation angles or azimuth angles. This weighting is preferably performed by dividing by the number of virtual interferometer arrays. However, other weightings are also conceivable, such as the corresponding weighting of individual antenna elements described above.

[0030] The invention also relates to a system for determining the elevation and azimuth angle of an incident electromagnetic wave, which is preferably suitable for carrying out one of the methods according to one of the methods described, with an antenna circuit group with m antenna elements, and a device as described above.

[0031] The invention also relates to a computer program product with program code for carrying out the method steps according to one of the described methods when the program is executed in a computer.

[0032] Furthermore, the invention relates to a computer program product with program code stored on a machine-readable carrier for carrying out the method according to one of the described methods when the program is executed in a computer.

[0033] A machine-readable medium is, for example, a CD-ROM, a recordable DVD-ROM, or a flash memory medium. Furthermore, the machine-readable medium can be integrated into an integrated circuit, e.g., an FPGA or a signal processor.

[0034] The invention is explained with reference to the drawings and the embodiments: Fig. 1 shows a top view of an interferometer with three orthogonally arranged antenna elements. Fig. Figure 2 shows a circular arrangement with seven antennas according to a preferred embodiment. Fig. 3 shows a circular arrangement with seven virtual, rectangular interferometer arrangements according to another preferred embodiment. Fig. Figure 4a shows a block diagram of a system for receiving radio signals according to a preferred embodiment. Fig. 4b shows a block diagram of a system for receiving radio signals according to another embodiment. Fig. Figure 2 shows an example of an antenna arrangement, also called an antenna array, with m (in the embodiment, m = 7) antenna elements arranged as an isosceles polygon. The direction of the incident electromagnetic wave is denoted by DoA (see Fig. 2). The antenna elements are labeled ch0 to ch6.

[0035] The angle a in the center of the polygon is: α=2πm

[0036] The internal angle β is given by the following relationship: β=π−α=(1−2m)π l=b⋅cos(β2)=b⋅sin(πm) where the length l of the polygon segment is given by (8) and b is the base diameter. With ΔΦ 06_ is the phase difference between the first antenna element ch0 and the seventh antenna element ch6. In general, the phase difference between the antenna elements ch k and ch k-1 with ΔΦ k k-1 designated.

[0037] The angle ψ is the azimuth angle, i.e., the angle between the propagation direction of the incident electromagnetic antenna and the orientation of the antenna array. The orientation of the antenna array can, for example, be the straight line from the center of the antenna array to the first antenna element ch0.

[0038] Based on Fig. 2, a preferred embodiment of a method for calculating the elevation and azimuth angle of an incident electromagnetic wave in an antenna array with seven antenna elements is explained by way of example. Fig. 2 is denoted by ΔΦ 06 corresponding to l0, the distance that the wave travels between the antenna elements ch0 and ch6 is called. In general, the distance that the wave travels between the antenna elements ch k and ch k-1 passes through, with l k , which is proportional to the phase difference ΔΦ k k-l .

[0039] In a first step, the phases Φ0, Φ1, Φ2, Φ3, Φ4, Φ5, Φ6 are measured and in a second step the phase differences ΔΦ 10 , ΔΦ 21 , ΔΦ 31 , ΔΦ 43 , ΔΦ 54 , ΔΦ 65 and ΔΦ 06 formed.

[0040] In a third step, three neighboring antenna elements, for example, ch0, ch1, and ch2, are combined to form an interferometer array. This is done in such a way that each of the seven antenna elements forms the basis of exactly one interferometer array. For example, ch1 forms the basis of the interferometer array ch0-ch1-ch2. In the interferometer array ch6-ch0-ch1, ch0 forms the basis. This creates m = 7 interferometer arrays.

[0041] The positions of the seven antenna elements are then virtually rotated such that the distance between the virtually rotated position of one of the two outer antenna elements and the position of its directly adjacent antenna element of the respective interferometer arrangement remains equal to l, and such that the virtually rotated position of one antenna element and the positions of the other two antenna elements of the respective interferometer arrangement form the vertices of an isosceles, right-angled triangle. For example, the position of antenna element ch0 is virtually rotated such that a virtual, right-angled interferometer arrangement is created by ĉh0-ch1-ch2.

[0042] The distance that the electromagnetic wave travels between the antenna elements k and the virtual antenna elements ĉh k-1 passes through, is denoted by l̂ k It is proportional to the phase difference Δ̇ k k-1between ĉh k-1 and ch k .

[0043] The angle between the propagation direction DoA of the incident electromagnetic wave and one side of the antenna polygon, the straight line between ch6 and ch0, is denoted by γ. With α =π-β, the following relations can be derived (see Fig. 3): l0l=sin(γ)l1l=sin(γ−α)⋯lkl=sin(γ−kα)⋯lm−1l=sin(γ−(m−1)α) l^0l=sin(γ+β−π2)=sin(γ−α+π2)=cos(γ−α)l^1l=sin(γ−2α+π2)=cos(γ−2 α)⋯l^kl=sin[γ−(k+1)α+π2]=cos[γ−(k+1)α]⋯l^m−1l=sin(γ+π2)=cos(γ)

[0044] From (9) and (10) follows: l1l=sin(γ−α)=sin(γ)⋅cos(α)−cos(γ)⋅sin(α) and cos(γ)=1sin(α)⋅[sin(γ)⋅cos(α)−l1l]=l^m−1l

[0045] For the k - th iteration of the preferred embodiment of the method presented above, one obtains: lk+1l=sin(γ−kα−α)=sin(γ−kα)⋅cos(α)−cos(γ−kα)⋅sin(α)cos(γ−kα)=1sin(α)[sin(γ−kα)cos(α)−lk+1l]=l^k−1l

[0046] From (9) and (10) follows: l^k−1=lk⋅cos(α)−lk+1sin(α) l^k=lk+1⋅cos(α)−lk+2sin(α)

[0047] With the phase difference ΔΦk=2πlkλ between antenna element k and k-1 along the distance l k or along the DoA propagation direction: ΔΦ^k=ΔΦk+1cos(α)−ΔΦk+2sin(α) and the elevation and azimuth for the k-th interferometer arrangement can be given as for a rectangular interferometer arrangement by: εk=arccos[(ΔΦk)2+(ΔΦ^k−1)22πlλ] and ψk=α(k+12)+arctan(ΔΦ^kΔΦk+1)

[0048] According to (12), (13) and (14), both the elevation and the azimuth depend only on the phase differences of the directly adjacent antenna elements of the respective interferometer arrangement and the angle α, which is given by the total number of antenna elements.

[0049] According to the invention, the elevation and the azimuth can be calculated by forming an average value from the bearing values, ie the elevation and the azimuth, of all m (in the embodiment m = 7) interferometer arrangements: ε=1m∑k=0m−1εkψ=1m∑k=0m−1ψk

[0050] According to the invention, the bearing values ​​of all interferometer arrays can also be calculated using weighting methods other than averaging, i.e., by summing all respective values ​​and dividing them by the number of virtual interferometer arrays. For example, individual antenna elements can be given special weighting by appropriate weighting.

[0051] The process can be extended as required with a larger number of antenna elements.

[0052] In Fig. 4a shows an example of a system for receiving radio signals. An antenna circuit group 100, in this embodiment with m = 7 antenna circuit elements, receives the radio signals to be located. The radio signals are then forwarded to a multi-channel receiver 200 connected to the antenna circuit group 100. A phase meter 300 measures the phase values ​​of the antenna signals of the antenna circuit elements of the antenna circuit group 100. The phase values ​​are then further processed in a processor unit 400. Devices 401 to 405 are integrated into this processor unit 400. Device 401 forms the phase differences of the phase values ​​of the adjacent antenna elements in the antenna circuit group, for example, the phase difference ΔΦ 21of the first and second antenna elements of the antenna circuit group 100. According to the invention, the devices 200, 300, and 401 can also be single-channel, so that the phase values ​​of the antenna elements are measured or formed in rapid, immediate succession instead of simultaneously. Device 402 forms the interferometer arrangements consisting of three adjacent antenna elements. According to the Fig. In the exemplary embodiment shown in Figure 4a, seven interferometer arrays are formed due to seven antenna elements. The m = seven virtual, rectangular interferometer arrays are then formed in device 403, and the virtual phase differences are calculated in device 404. The elevation and azimuth angles of the interferometer arrays are determined in device 405.

[0053] According to another study in Fig.In the embodiment shown in Fig. 4b, the elevation and azimuth angles of the interferometer arrangements are each summed and weighted in a further device 406.

[0054] Although the invention is illustrated and described in detail by means of the figures and the associated description, this illustration and this detailed description are to be understood as illustrative and exemplary and not as limiting the invention. It is understood that those skilled in the art may make changes and modifications without departing from the scope and spirit of the following claims. In particular, the invention also encompasses embodiments having any combination of features mentioned or shown above or below for various embodiments.

[0055] The invention also encompasses individual features in the figures, even if they are shown there in connection with other features and / or are not mentioned above or below. Furthermore, the alternative embodiments described in the figures and the description, and individual alternatives of their features, may be excluded from the subject matter of the invention or from the disclosed subject matter. The disclosure encompasses embodiments that exclusively comprise the features described in the claims or in the exemplary embodiments, as well as those that comprise additional other features.

Claims

[1] Method for determining the elevation and azimuth angle of an incident electromagnetic wave, in an antenna circuit group (100) with m antenna elements, wherein the antenna elements each have a distance l from their directly adjacent antenna elements, with the following steps: a) Measuring the phase values ​​of the antenna elements, b) Forming the phase differences of the phase values ​​of the adjacent antenna elements, c) forming m interferometer arrays each consisting of three adjacent antenna elements, d) forming m virtual, rectangular interferometer arrays by virtually rotating the position of one of the two outer antenna elements of the three adjacent antenna elements of the respective interferometer array such that the distance between the virtually rotated position of one of the two outer antenna elements and the position of its directly adjacent antenna element of the respective interferometer array remains equal to l and such that the virtually rotated position of one antenna element and the positions of the other two antenna elements of the respective interferometer array form the vertices of an isosceles, right-angled triangle, e) Determining the virtual phase difference between the antenna element whose position is virtually rotated and its directly adjacent antenna element of the respective virtual, rectangular interferometer arrangement using the phase differences formed in step c) of the respectively directly adjacent antenna elements of the respective interferometer arrangement and the angle α=2 π / m, f) Determining the elevation angle and / or the azimuth angle of the respective virtual, rectangular interferometer arrangement using the virtual phase difference and the phase difference of the phase values ​​of the directly adjacent antenna elements of the interferometer arrangement that are not virtually rotated. [2] Method according to claim 1, wherein the elevation angles and / or azimuth angles of all virtual interferometer arrangements are each summed up and the sum of the elevation angles or azimuth angles is weighted, preferably by division by the number of virtual interferometer arrangements. [3] Method according to claim 1 or 2, wherein steps d) to f) are carried out only for a number u < m of antenna elements, preferably with 1 < u < m. [4] Method according to one of claims 1 to 3, wherein the antenna circuit group (100) consists of 7 antenna elements. [5] Device for determining the elevation and azimuth angle of an incident electromagnetic wave in an antenna circuit group (100) with m antenna elements, which is preferably suitable for carrying out the steps of one of the methods according to one of the preceding claims, comprising: a) a multi-channel receiver (200) connected to the m antenna elements and receiving the m antenna signals of the m antenna elements, b) a phase meter (300) connected to the multi-channel receiver (200) and measuring the phase of the respective antenna element of the antenna circuit group (100), c) a device (401) for forming the phase differences of the phase values ​​of the respective adjacent antenna elements, d) means (402) for forming m interferometer arrays each comprising three adjacent antenna elements, e) a device (403) for forming m virtual, rectangular interferometer arrangements by virtually rotating the position of one of the two outer antenna elements of the three adjacent antenna elements of the respective interferometer arrangement such that the distance between the virtually rotated position of one of the two outer antenna elements and the position of its directly adjacent antenna element of the respective interferometer arrangement remains equal to l and such that the virtually rotated position of one antenna element and the positions of the other two antenna elements of the respective interferometer arrangement form the vertices of an isosceles, right-angled triangle, f) a device (404) for determining the virtual phase difference between the antenna element whose position is virtually rotated and its directly adjacent antenna element of the respective virtual, rectangular interferometer arrangement using the phase differences formed in step c) of the respectively directly adjacent antenna elements of the respective interferometer arrangement and the angle α=2 π / m, and g) means (405) for determining the elevation angle and / or the azimuth angle of the respective virtual, rectangular interferometer arrangement using the virtual phase difference and the phase difference of the phase values ​​of the directly adjacent antenna elements of the interferometer arrangement which are not virtually rotated. [6] Apparatus according to claim 5, further comprising means (406) adapted to sum the elevation angles and / or azimuth angles of all virtual interferometer arrangements respectively and to weight the sum of the elevation angles or azimuth angles, preferably by means of division by the number of virtual interferometer arrangements. [7] Device according to claim 5 or 6, wherein the antenna circuit group (100) consists of 7 antenna elements. [8] System for determining the elevation and azimuth angle of an incident electromagnetic wave, preferably suitable for carrying out a method according to any one of claims 1 to 4, comprising: a) an antenna circuit group (100) with m antenna elements, and b) a device according to any one of claims 5 to 7. [9] Computer program product with program code for carrying out the method steps according to one of claims 1 to 4 when the program is executed in a computer. [10] Computer program product with program code stored on a machine-readable carrier for carrying out the method according to one of claims 1 to 4 when the program is executed in a computer.

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