CONTROL DEVICE, ANTENNA ARRAY AND METHOD FOR CONTROLLING AN ANTENNA ARRAY

Abstract

A control device (50) for digital beamforming of an antenna array (100) is disclosed. The antenna array (100) comprises at least a first sub-aperture (110) for generating a plurality of first antenna cones (210) and a second sub-aperture (120) for generating a plurality of second antenna cones (220). The control device is configured to alternately arrange the first antenna cones (210) and the second antenna cones (220) side by side, wherein the first sub-aperture (110) and the second sub-aperture (120) are configured to utilize different sampling frequencies (Fs1, Fs2) and to perform subsampling in each case.

Description

[0001] The present invention relates to a control device for digital beam shaping of an antenna array, to an antenna array and to a method for controlling the antenna array and, in particular, to a digital beam shaping antenna for radar systems for ESM applications (ESM, Electronic Support Measure). BACKGROUND

[0002] Conventional antenna systems include rotating antennas (so-called spinning antennas), linear interferometers, circular interferometers (e.g., arranged as circle groups), and sector antennas with amplitude diagram analysis. The latter are mechanically rigid and can only be used for a predetermined purpose. In particular, it is not possible to reprogram these antenna systems for other purposes. For example, an interferometer cannot be reprogrammed to be a high-gain antenna. Similarly, a high-gain mechanical antenna, such as a parabolic reflector or a horn antenna, cannot be converted or reconfigured to be a wide-field antenna. Broadband radiating apertures can be achieved, for example, by coupled dipoles or radiating slots (so-called "current sheet antennas").

[0003] Fig.Figure 7 shows examples of conventional antenna systems, with a so-called rotating antenna 710 at the top, which has a focused, rotatable radar beam (antenna cone) in its antenna characteristic. One advantage of this conventional antenna is its broadband capability, whereby the ratio between maximum and minimum frequency can be greater than 8:1, for example. With an example maximum frequency of 4 GHz and a minimum frequency of 0.5 GHz, a factor of 8 is thus achievable. Below is a conventional interferometer 720, which is typically implemented with spiral antennas. The interferometer 720 has low directivity. Other conventional antenna arrangements with spiral antennas include the so-called four-quadrant monopulse array 730, which is chosen when complete spatial coverage is required.

[0004] With conventional antenna systems, compromises must always be made or a compromise found (e.g., between sensitivity and wide coverage). The specific hardware used determines which aspects are guaranteed and which are not. This situation is unsatisfactory.

[0005] Therefore, there is a need for antenna systems that break with the paradigm and can be adapted situationally / flexibly to the needs. BRIEF DESCRIPTION OF THE INVENTION

[0006] At least some of the aforementioned problems are solved by a control device according to claim 1 and a method for controlling an antenna array according to claim 12. The dependent claims relate to advantageous embodiments of the subject matter of the independent claims.

[0007] The present invention relates to a control device for digital beamforming of an antenna array. The antenna array comprises at least a first sub-aperture for generating a plurality of first antenna cones and a second sub-aperture for generating a plurality of second antenna cones. The control device is configured to alternately arrange the first antenna cones and the second antenna cones side by side (e.g., as a fan), wherein the first sub-aperture and the second sub-aperture are configured to utilize different sampling frequencies and perform subsampling in each case. This operating mode is also referred to within the scope of this disclosure as the first mode, M1.

[0008] Within the scope of this disclosure, an antenna cone is understood to be a main lobe of the antenna. The beamforming determines the shape and direction of the antenna cones, whereby digital beamforming makes it possible to form multiple antenna cones for each sub-aperture (in contrast to analog beamforming), which can be selectively adjusted and also steered.

[0009] Undersampling means that the frequencies of the received signals do not all lie within the first Nyquist zone, but are distributed across several NYZs. This is equivalent to using a sampling frequency that is too low to unambiguously determine the spectrum of the received signals.

[0010] A sub-aperture can be defined, for example, by comprising a multitude of antenna elements (so-called radiators) that can be controlled together to generate one or more antenna cones (beams). The antenna elements are typically all arranged at a predetermined distance from one another, which can be chosen to suppress side lobes or side lobes in the antenna characteristic. The multitude of antenna elements of the antenna array can be flexibly divided into sub-apertures according to exemplary embodiments.

[0011] Optionally, the subsampling extends to three Nyquist zones, and the control device is designed to uniquely assign sampled received signals to the three Nyquist zones based on a frequency difference of samples for a received signal sampled at the different sampling frequencies, and to calculate a plurality of antenna cones belonging to the three Nyquist zones for each sampled received signal.

[0012] This resolves the ambiguity (aliasing) of sampled values ​​that arises from the overlapping of signals from higher Nyquist zones to lower Nyquist zones. Undersampling therefore does not lead to a loss of information or uniqueness.

[0013] Optionally, the control device is further developed to arrange the first and second antenna cones side by side (alternating or sequentially), with oversampling being performed in both the first and second subapertures. Due to the oversampling, all sampled values ​​lie within the first Nyquist zone, and no aliasing (ambiguity) occurs. This operating mode is also referred to as the second mode, M2, within the scope of this disclosure.

[0014] Optionally, the control device is further developed to overlap the first and second antenna cones. It is understood that overlapping antenna cones are aligned in the same direction (e.g., towards a position within an observation area). In particular, all antenna cones can overlap one or more sub-apertures or all sub-apertures to achieve high beam focusing. This operating mode is also referred to as the third mode, M3, within the scope of this disclosure.

[0015] If at least some antenna cones have the same direction of view, a coherent addition of the corresponding antenna signals (e.g., received signals) can optionally be performed.

[0016] Optionally, the antenna array includes a plurality of sub-apertures arranged along rows and / or columns, with the first sub-aperture and the second sub-aperture being adjacent along a row or a column.

[0017] According to further embodiments, the defined modes can be mixed as desired (in azimuth and / or elevation). For example, four sub-apertures can be present in two rows, with two sub-apertures in each row. Accordingly, the control device can be configured to operate the sub-apertures in the rows (or columns) as follows: - each in the first mode, - each in the second mode, - each in the third mode, - one line in first mode (or third mode) and the other line in second mode (or third mode), - any other combination of modes.

[0018] In particular, all antenna cones of all sub-apertures can optionally overlap. Optionally, all antenna cones can also be arranged next to each other in at least one row or at least one column to form multiple superimposed fans.

[0019] Optionally, the control device is further developed to perform a bearing based on at least one of the following methods: - a phase monopulse method, - an amplitude monopulse method (e.g. with antenna gain), - an interferometry (e.g. in elevation), - a 4-quadrant monopulse method (with a focused array).

[0020] It is clear to an expert that the amplitude monopulse method involves comparing the amplitude values ​​of a pulse (e.g., from a transmitter or emitter in the observation area) from different sub-apertures. If the antenna cones of the sub-apertures are oriented in different directions, the amplitude values ​​from one and the same source will differ considerably due to the antenna characteristics. Therefore, for example, adjacent sub-apertures of a fan array (second mode) are particularly well-suited for bearing in the direction of the fanning.

[0021] It is also clear to an expert that the phase monopulse method compares the phase angles of a pulse (e.g., from a transmitter or emitter in the observation area) from different sub-apertures. If the antenna cones of sub-apertures are aligned in the same direction, the amplitude values ​​differ little or not at all. However, the phase angle changes significantly due to the different distances of the spaced sub-apertures from the transmitter. Therefore, spaced sub-apertures with overlapping antenna cones (first mode or third mode) are particularly well-suited for bearing in the direction of the spacing.

[0022] The aforementioned direction-finding methods can also be combined. Direction finding can also be performed by sweeping. However, a major advantage of digital beamforming is that a large area can be scanned simultaneously, allowing for direction finding using a monopulse method. Furthermore, the size of the antenna cones (e.g., the beamwidth) can be adjusted to the coverage area.

[0023] Optionally, the control device can use each sub-aperture to constantly direct an antenna cone towards a specific observation object or track its movement by panning.

[0024] According to the exemplary embodiments, the antenna array can be operated in a frequency range from 350 MHz to 6 GHz. The different sampling frequencies can differ by 150 MHz to 300 MHz. The sampling frequencies used can be multiples of a clock signal (e.g., 125 MHz).

[0025] Exemplary embodiments also relate to an antenna array with digital beamforming, which has several adjacent sub-apertures, each comprising a plurality of antenna elements. Each sub-aperture is again configured to generate a plurality of antenna cones. Furthermore, the antenna array can include a control device as previously described.

[0026] Optionally, all adjacent antenna elements are arranged at a predetermined distance from each other. A predetermined distance can also exist between antenna elements of adjacent sub-apertures (e.g., 25 mm at 6 GHz and a wavelength of 5 cm).

[0027] Examples of implementation also relate to a method for controlling an antenna array as described previously. The method includes: - Arranging (or forming) the first antenna cones and the second antenna cones alternately next to each other (e.g. forming a fan); and - Sampling of received signals with different sampling frequencies in the first sub-aperture and in the second sub-aperture, with one subsampling being performed in each case.

[0028] Optionally, the procedure also includes selecting one of the following modes by controlling the antenna array accordingly: a first mode, as previously described (the first antenna cones and the second antenna cones are arranged alternately next to each other and undersampling takes place), a second mode where the first antenna cones and the second antenna cones are arranged side by side (alternating or sequentially to form a fan), with the first sub-aperture and the second sub-aperture each performing oversampling, a third mode, where at least some of the first antenna cones and the second antenna cones are arranged overlapping (beam focusing by overlapping).

[0029] It is understood that the modes can be selected at different times (earlier or later than the subsampling in the first mode).

[0030] This method, or at least parts thereof, can also be implemented or stored in the form of instructions in software or on a computer program product (e.g., a storage medium), wherein the stored instructions are capable of executing the steps of the method when the method is running on a processor. Therefore, the present invention also relates to a computer program product with software code (software instructions) stored on it, configured to execute one of the methods described above when the instructions are executed by a processing unit. The processing unit can be any type of computer or control unit that has a suitable microprocessor / programmable logic capable of executing software / firmware code.

[0031] Examples of such systems overcome the problems of conventional antenna systems through the flexible control of phased or timed array antennas for reconnaissance and direction finding of signal sources. These signal sources include, for example, civilian or military objects (e.g., an aircraft, a vehicle, a ground station, a mobile phone antenna) that emit electromagnetic signals at different frequencies and whose position needs to be determined for reconnaissance purposes.

[0032] Advantages of exemplary embodiments include the fact that the control device and thus the antenna array can be flexibly adapted to the intended use, in particular by switching between the following modes: - high area coverage, - high beam focusing, - Elevation determination.

[0033] Implementations with high spatial coverage (in azimuth or elevation) utilize a fan-shaped arrangement of the beam directions. Advantageously, these implementations employ multiple Nyquist zones, taking advantage of the overlapping of the analog-to-digital converters (ADCs). The resulting undersampling leads to a high instantaneous bandwidth. The ambiguity caused by the overlapping when using multiple Nyquist zones is resolved by employing multiple sampling rates. For example, adjacent beam directions in a fan beam can be sampled at different rates. Bearing information can be determined by evaluating the amplitude ratios (amplitude 1 / amplitude 2) for two adjacent or two different radar cones.

[0034] On the other hand, exemplary implementations achieve high beam focusing and thus high antenna gain, for example, by summing the antenna signal contributions of the sub-apertures in one spatial direction. Identical sampling rates can be used on the sub-apertures in this case. For this mode, bearing values ​​can be generated by evaluation using the four-quadrant monopulse method, whereby difference signals and sum signals can be used.

[0035] For elevation determination, exemplary embodiments can utilize a paired arrangement of the sub-aperture beam directions to form a two-row fan beam. The sampling rates of the paired beams can be the same and different for adjacent viewing directions. This allows received signals from different viewing directions to be sampled at different sampling rates.

[0036] Advantageously, these embodiments are also applicable to situations where each sub-aperture is used to observe a corresponding signal source. For example, four sub-apertures can be used to create four beam directions in order to continuously observe four signal sources.

[0037] Another advantage of exemplary embodiments is that any combination of the different modes becomes possible. For example, two sub-apertures in a first row can be operated in one mode, and the two sub-apertures below them in a second row can be operated in a different mode. The same applies to sub-apertures arranged next to each other in a row.

[0038] Another advantage of exemplary implementations is that subsampling combines high bandwidth with low processor resource consumption, thus enabling beam shaping with an FFT (Fast Fourier Transform).

[0039] Advantageously, exemplary embodiments allow the use of real-time delay elements, which can be implemented in digital beam shaping, for example, as fractional finite impulse response (FIR) filters. BRIEF DESCRIPTION OF THE FIGURES

[0040] The embodiments of the present invention are better understood with reference to the following detailed description and the accompanying drawings of the different embodiments, which, however, should not be understood as limiting the disclosure to the specific embodiments, but merely serve for explanation and understanding. Fig.Figure 1 shows an antenna array with digital beamforming according to embodiments of the present invention. Fig. Figure 2 illustrates further details of the antenna array as it can be used according to the embodiment examples. Fig. Figure 3 illustrates possible operating modes for the control device according to exemplary embodiments. Fig. Figure 4 illustrates a resolution of the ambiguity according to exemplary implementations. Fig. Figure 5 shows an example of a room view of the antenna array. Fig. Figure 6 shows a schematic flowchart for a method for controlling the antenna array according to exemplary embodiments. DETAILED DESCRIPTION

[0041] Fig.Figure 1 shows an antenna array 100 with digital beamforming, which, according to exemplary embodiments, is controlled by a control device 50 in various operating modes. The antenna array 100 comprises several adjacent sub-apertures 110, 120, 130, 140, each with a plurality of antenna elements (not shown). Each sub-aperture 110, 120, 130, 140 is configured to generate several antenna cones 210, 220, 230, 240. The control device 50 controls the digital beamforming of the antenna array 100 by activating one or more modes, which are described in detail below.

[0042] The antenna cones 210, 220, ... are the main lobes of the antenna characteristic, which are generated by the sub-apertures 110, 120, ... with their plurality of antenna elements. The antenna array 100 shown has, by way of example, four sub-apertures 110, 120, 130, 140, of which any two sub-apertures can be operated in any mode, while the remaining two can be operated in another mode. It is understood that the antenna array 100 can also be formed by more than four sub-apertures 110, ..., 140 or by an array (with rows and columns) of sub-apertures. Each sub-aperture 110, 120, 130, 140 is able, based on control by the control device 50, to generate or swivel the associated antenna cones 210, 220, 230, 240 with a desired opening angle (beam width) and in a desired number (see Fig. 1).

[0043] According to exemplary embodiments, the control device 50 can form an integral unit with the antenna array 100 (e.g., be housed in a common casing). For example, the control device 50 can be arranged on a rear side with respect to the front antenna cones 210, 220, ... It can also control the antenna array 100 remotely.

[0044] Fig. Figure 2 illustrates further details of the antenna array 100, as it can be used according to exemplary embodiments for the detection of signal sources in an observation area. The signal sources generate, for example, electromagnetic waves that can be received by the antenna array 100, with exemplary embodiments being particularly suitable for broadband detection, where a frequency band of, for example, several gigahertz is covered.

[0045] As the Fig.As shown in Figure 2 above, the antenna array 100 again comprises, by way of example, four sub-apertures 110, 120, 130, 140, each of which includes a plurality of antenna elements 111, 121, 131, 141 (radiators). Each sub-aperture 110, 120, 130, 140 is capable of generating several antenna cones 210, 220, ... with a desired opening angle (beam width) based on control by the control device 50. Only four sub-apertures are shown by way of example, with a first sub-aperture 110, a second sub-aperture 120, a third sub-aperture 130, and a fourth sub-aperture 140 arranged in two superimposed rows. However, it is also possible that there may be more or fewer sub-apertures than shown, or that the sub-apertures may also be arranged in a row. The exemplary embodiments are applicable to any arrangement of several sub-apertures 110, 120, ...

[0046] The sub-apertures 110, 120, ... themselves form an array of active antenna elements 111, 112, ..., around which neutral antenna elements 150 are arranged. Thus, according to the exemplary embodiments, each active antenna element 111, 112, ... has at least one neighboring antenna element on each side. In this way, the active antenna elements 111, 112, ... behave identically, and the antenna characteristics are improved (more homogeneous). It is understood that the number of antenna elements 111, 112, ... and the arrangement of the sub-apertures 110, 120, ... can be chosen arbitrarily and adapted to the specific requirements. For example, each sub-aperture 110, 120, ... can have an array of 32 (active) antenna elements 111, 112, ... so that a total of 128 (active) antenna elements 111, 112, ... can be present, with this number being arbitrarily changeable.

[0047] Since digital beamforming is used, each sub-aperture 110, 120, ... is able to generate a variety of antenna cones 210, 220, ... which can be aligned in different spatial directions and adjusted in their opening angle according to the needs.

[0048] Fig. Figure 2 below schematically illustrates a possible signal acquisition for the antenna array 100. The antenna elements 111 receive corresponding received signals from signal sources (distant emitters) and forward these signals to the respective input circuits 260 (Rx-front). There, initial signal conditioning (e.g., amplification) can take place before the analog signals are subsequently converted into digital signals by the respective analog-to-digital converters 270 (ADCs), which can then be stored in a memory 280. The ADCs 270, for example, perform sampling at one or more predetermined sampling frequencies.

[0049] The corresponding digital signals are read from this memory 280 and selectively weighted with corresponding weights W1, W2, ... in a beamforming unit 290 before the weighted digital signals are summed (in adder 295). This weighted addition creates linear combinations of input signals, resulting in beamforming. The result is a multitude of beams (radar cones 210, 220) which are output accordingly.

[0050] In this process, the weights Wi (i = 1, 2, 3, ... n) define the antenna cones 210, 220, ... with respect to their orientation as well as their width or beamwidth. The weight factors Wi can be adjusted according to the conditions and needs of the user (e.g., with regard to maximum coverage or high focus). This summation of weighted digital input signals is performed for each beam and is controlled by the control device 50, for example, by selecting the antenna elements 111, selecting the weights Wi, choosing the sampling frequency, etc.

[0051] As previously explained, one advantage of digital beamforming is that multiple radar cones (210, 220, ...) can instantly capture or cover an entire sector. Furthermore, it is possible to use dedicated radar cones for the continuous observation of specific targets. Bearing direction in digital beamforming can be determined, for example, using difference diagrams (e.g., using the amplitude monopulse or phase monopulse method), as is also known from four-quadrant monopulse systems.

[0052] Fig. Figure 3 illustrates possible operating modes as they can be implemented by control device 50 according to exemplary embodiments. The control device 50 can be arranged on the rear side of the antenna array 100, but is located in the Fig.Figure 3 is not shown. As an example, the antenna array again has four sub-apertures 110, 120, 130, 140, arranged in two rows and two columns and surrounded by boundary cells 150. As shown, the antenna array 100 can have a rectangular shape with a long and a short side, where the azimuth angle can be measured, for example, along the long side and the elevation perpendicular to it (along the short side). As usual, the azimuth angle can refer to an angular range of 360° horizontally and the elevation to an angular range of 180° vertically (in a standard polar coordinate system).

[0053] Each of these four sub-apertures can be controlled in one of the following modes M1, M2, M3 by the control device 50, which selects, for example, suitable weights Wi and / or suitable sampling frequencies. First mode M1

[0054] In the first mode M1 (left in the Fig. (as shown in Figure 3) the first antenna cones 210 and the second antenna cones 220 are arranged alternately next to each other, forming a fan. Furthermore, in this first mode M1, subsampling is performed for both the first sub-aperture 110 and the second sub-aperture 120, using different sampling frequencies. Received signals from the first sub-aperture 110 can be sampled with a first sampling frequency Fs1, and received signals from the second sub-aperture 120 can be sampled with a second sampling frequency Fs2, where Fs1 ≠ Fs2. Sampling takes place in the ADCs 270 (see Figure 3). Fig. 2).

[0055] Another fan beam is spanned by the third sub-aperture 130 and the fourth sub-aperture 140, with the third antenna cones 230 and the fourth antenna cone 240 alternating. These two sub-apertures 130 and 140 can also be controlled in the first mode M1, so that the third and fourth antenna cones 230 and 240 can each receive signals at different sampling frequencies (in the corresponding ADCs 270). For example, the first sampling frequency F1 can be used for sampling the first sub-aperture 110 and the third sub-aperture 130. Accordingly, the second sub-aperture 120 and the fourth sub-aperture 140 can use the second sampling frequency Fs2 to sample the received signals, with the second sampling frequency Fs2 and the first sampling frequency F1 again differing.

[0056] Using different sampling frequencies Fs1 and Fs2 makes it possible to resolve ambiguities resulting from undersampling. This will be discussed further below. Fig. 4 described in more detail.

[0057] The antenna cones 230 and 240 of the third sub-aperture 130 and the fourth sub-aperture 140 are, for example, aligned in the same direction as the antenna cones 210 and 220 of the first sub-aperture 110 and the second sub-aperture 120. The two cones are aligned, for example, along the same line in the observation area. Since the two antenna cones shown here overlap, no electronic sweep is performed during elevation. However, the bearing during elevation can be determined, for example, via a phase difference within the beamwidth (e.g., by using a phase monopulse method). For this purpose, a coherent evaluation of received signals from the first sub-aperture 110 and the third sub-aperture 130, as well as from the second sub-aperture 120 and the fourth sub-aperture 140, is used to utilize the corresponding phase differences for bearing determination. Second mode M2

[0058] In the Fig.Figure 3, in the center, shows the second mode, M2. In the second mode, M2, no subsampling is used; that is, the sampling frequency is chosen to be correspondingly high, or the received signals are filtered accordingly, so that the received signals lie only in the first Nyquist zone. For example, the first Nyquist zone can be in a range between 0.35 GHz and 1 GHz.

[0059] In the second mode 2, the first and second antenna cones 210, 220 (of the first and second sub-apertures 110, 120) are again fanned out to form a first fan 210, 220, whereby antenna cones 210, 220 of the individual sub-apertures 110, 120 can alternate, be arranged sequentially, or all overlap. The same applies to a second fan 230, 240, which is generated by the antenna cones 230, 240 of the third sub-aperture 130 and the fourth sub-aperture 140. The first fan 210, 220 can be arranged above the second fan 230, 240. Both fans 210, 220 / 230, 240 can also have the same viewing direction (overlap). The individual received signals from the overlapping antenna cones can be coherently added together, enabling bearing in elevation using the phase monopulse method. In azimuth, bearing can be performed using the amplitude monopulse method.

[0060] In the second mode 2, it is also possible for all sub-apertures 110, 120, 130, and 140 to jointly cover only one fan (e.g., along the azimuth). This offers the advantage that only fewer (e.g., four) antenna cones are required to cover the lateral field of view. A bearing can still be taken in the azimuth using the amplitude monopulse method. A sweep can be performed in the elevation. Third Mode M3

[0061] In the Fig. Figure 3 on the right shows the third mode M3, which differs from the first mode M1 and the second mode M2 ​​in that for each sub-aperture 110, 120, ... only one antenna cone 210-240 is formed.

[0062] All antenna cones 210, 220, 230, and 240 then point in the same direction. This achieves a high degree of beam focusing. Bearings in all directions, especially in azimuth and elevation, are possible simultaneously with this third mode, M3, as phase monopulse bearings. This third mode, M3, allows for a bearing accuracy that is better than, for example, one-tenth the beamwidth of a single antenna cone, 210-240. Another advantage of the third mode, M3, is a high signal-to-noise ratio. However, due to the strong beam focusing, only one line of sight is covered.

[0063] It goes without saying that the modes M1, M2, and M3 shown can be combined in any way. For example, the second mode, M2, can be used with a fan beam for the first sub-aperture 110 and the second sub-aperture 120, utilizing only the first Nyquist zone. Simultaneously or sequentially, the third sub-aperture 130 and the fourth sub-aperture 140 can be operated in the first mode, M1, utilizing multiple Nyquist zones. Similarly, the modes M1, M2, and M3 can be distributed differently along the rows and columns, or multiple modes can be used consecutively in a single row or column.

[0064] Fig. Figure 4 illustrates a resolution of the ambiguity when using a frequency bandwidth that spans multiple Nyquist zones (subsampling), as used, for example, in the first mode M1. Specifically, the Fig.4. A dependency of the sampled frequency values ​​Fout (sample values) on the frequency Fin of an input signal received at the antenna elements 111, 121, ... The frequencies Fin of the input signals can, for example, lie in a frequency range from 350 MHz to 6 GHz. Thus, the antenna array can receive and evaluate 100 signals from a frequency band of up to 6 GHz or even higher.

[0065] In the first mode 1, received signals are sampled with a first sampling frequency Fs1 and a second sampling frequency Fs2, each a multiple of a timer signal. If the timer signal is, for example, 125 kHz, then n * 125 MHz (n being a natural number) can be used as sampling frequencies. Frequency multipliers can be used for this purpose. For example, the first sampling frequency Fs1 and the second sampling frequency Fs2 can differ by 250 MHz. However, other values ​​can also be used.

[0066] If the first sampling frequency Fs1 is lower than the second sampling frequency Fs2, the first Nyquist zone NZ1 extends to a frequency of ½*Fs1 (half the first sampling frequency Fs1), the second Nyquist zone NZ2 extends from Fs1 / 2 to Fs1, and the third Nyquist zone NZ3 extends from Fs1 to 3 / 2*Fs1. Strictly speaking, the Nyquist zones for the second sampling frequency Fs2 are larger, but this will not be relevant here. Without loss of generality, the second sampling frequency Fs2 can also be chosen to be lower than the first sampling frequency Fs1.

[0067] For any input signal with a frequency f1 within the first Nyquist zone NZ1, both samples yield a unique sample value F1 (sampling is unique). An input signal with a frequency f2 within the second Nyquist zone NZ2 yields two samples: F2a for the first sampling frequency Fs1 and F2b for the second sampling frequency Fs2. The difference between the two samples is Δ=F2b−F2a>0 in NZ2, (since Fs2>Fs1). An input signal with a frequency f3 within the third Nyquist zone NZ3 also yields two samples: F3a for the first sampling frequency Fs1 and F3b for the second sampling frequency Fs2. Again, the difference yields Δ=F3b−F3a>0 in NZ3, (see Fig. 3) This results in the following table: Input frequency Sample value for Fs1 Sample value for Fs2 difference NZ1 f1 F1 F1 Δ = 0 NZ2 f2 F2a F2b Δ > 0 NZ3 f3 F3a F3b Δ < 0.

[0068] If more than three Nyquist zones are used, this pattern would continue accordingly. The sign of Δ changes from Nyquist zone to Nyquist zone, but the magnitudes of Δ become progressively larger. Therefore, differentiation would still be possible.

[0069] These exemplary implementations are thus able to resolve ambiguities arising from violations of the Nyquist-Shannon sampling theorem. If only one frequency is sampled, i.e., Δ = 0, it is a received signal in the first Nyquist zone, NZ1. If two frequencies are sampled with Δ > 0, it is a received signal in the second Nyquist zone, NZ2. If two frequencies are sampled with Δ < 0, it is a received signal in the third Nyquist zone, NZ3. Since the samples for each sampling frequency can be stored separately, assigning the samples to the sampling frequencies is also straightforward.

[0070] As from the Fig. As can be seen in Figure 3, this assignment is also applicable to the frequency range between Fs1 and Fs2 or between Fs1 / 1 and Fs2 / 2. Only the magnitude of Δ is correspondingly smaller there.

[0071] According to the exemplary embodiments, the signals can also be filtered. For example, high-pass filter 410 can be used to receive signals for multiple Nyquist zones. The antenna array 100 can accordingly be operated in the first mode M1. The first high-pass filter 410 can, for example, filter out all signals that lie below a lower frequency limit Fu, which is, for example, 300 MHz.

[0072] A bandpass filter 420 can also be used to utilize only signals from the first Nyquist zone NZ1 in the antenna array 100, thus enabling the antenna array 100 to operate in the second mode M2. The two modes M1 and M2 can also be mixed (e.g., using different sub-apertures in different arrays). In this situation, the bandpass filter 420 can be used to provide the signals for the second mode M2 ​​as a frequency band within the first Nyquist zone. A third high-pass filter 430 can then be used, which only allows signals above this frequency band to pass through. Since the frequency band does not cover the entire first Nyquist zone, the third high-pass filter 430 also allows signals from the first Nyquist zone to pass through. Using this high-pass filter 430, received signals for the second mode M2 ​​can be filtered out.

[0073] Advantageously, exemplary embodiments can utilize the so-called AESA setup (Active Electronically Scanned Array antenna), where analog combiners each combine signals from four antenna elements 111 (e.g., in one column of the sub-apertures from the Fig. 2 or Fig. 3) Combine and provide a broadband radiator array with broadband digitization. Furthermore, the weighted sums of the different channels enable beamforming and azimuth steering. As mentioned, three direction-finding methods can be used: an amplitude monopulse method for azimuth coverage with high antenna gain, interferometric direction finding for elevation direction finding, and a four-quadrant monopulse method with a focused antenna array.

[0074] Fig.Figure 5 shows an example of a spatial view of the antenna assembly 100 with the antenna elements 111, 121, 131, 141 of all apertures 110, 120, ... on a front view. Behind this is an analog electronics unit with the input circuits 260 for the initial signal processing. Behind this are the analog-to-digital converters 270, the memory 280, and the beamforming units 290. A power supply 510 with a power connector 512 and a digital output 530 for providing output signals are also present. The antenna assembly 100 further includes an air cooling system 520, which blows cooling air along the electronic components via air inlets by means of a fan.

[0075] Fig. Figure 6 shows a schematic flowchart for a procedure for driving an antenna array as described previously. The procedure includes: - Arrange S110 of the first antenna cones and the second antenna cones alternately next to each other; and - Sampling S120 of received signals with different sampling frequencies in the first sub-aperture 110 and the second sub-aperture 120, with one sub-sampling being performed in each case.

[0076] The method can also be computer-implemented, i.e., it can be implemented by instructions stored on a storage medium that are capable of executing the steps of the method when running on a processor. The instructions typically comprise one or more instructions that may be stored in different ways on different media in or peripherally to a control device 50 (containing a processor), which, when read and executed by the control device 50, cause the control device 50 to perform functions, functionalities, and operations necessary for carrying out a method according to the present invention.

[0077] It is understood that all previously described functions of the antenna array 100 and the control device 50 can be implemented as further optional process steps. Furthermore, it is understood that the order in which the process steps are listed does not necessarily imply a sequence in which they are executed. The steps can also be executed in a different order, or only a subset of the process steps may be carried out.

[0078] Advantageous aspects of exemplary embodiments can be summarized as follows: Received signals are first converted from analog to digital and linear combinations are formed, with the formation of these linear combinations occurring simultaneously for multiple antenna cones. This at least partially eliminates or circumvents limitations that exist for analog beamforming. - Examples of implementations can, for example, dynamically change the directivity of the antenna or switch between strong and weak directivity. - For direction finding methods, monopulse methods or interferometric methods, for example, can be used. - The dynamic range is increased on the digital side through summation. - The bandwidth to be used can be flexibly adapted to the signals to be observed (e.g. across several Nyquist zones). Finally, exemplary embodiments do not include rotating parts that may present problems such as icing, maintenance, safety and probability of failure, which is not the case in the exemplary embodiments. - Furthermore, exemplary implementations offer the advantage that, in digital beamforming, the number and direction of the antenna cones (beams) can be adjusted depending on the frequency or beamwidth. The functions can be provided via implementable firmware. The corresponding electronics include, for example, a highly integrated chip with 8 to 16 analog-to-digital converters up to a maximum frequency of 6 GHz. - Overall, these implementation examples offer the advantage that the reconnaissance performance - in the sense of a fast and sensitive detection of objects - is significantly increased compared to conventional antenna systems.

[0079] The features of the invention disclosed in the description, claims and figures may be essential for the realization of the invention, either individually or in any combination. REFERENCE MARK LIST 50 Control device 100 antenna array 110, 120, 130, 140 sub-apertures 111, 121, 131, 141 antenna elements 150 edge antenna elements 210, 220, 230, 240 antenna cones 260 input circuits (front end) 270 Analog-to-Digital Converters 280 storage 290 Beam shaping unit 295 Adders 410,430 High-pass filter 420 bandpass filters 510 Power supply 512 Power connection 520 Cooling 530 digital output 710 rotating antenna 720 Interferometer 730 Four-quadrant monopulse antenna Wi weights for beam shaping Fs1, Fs2 (different) sampling frequencies f1, f2, f3 Received signals F1,F2a,F2b,F3a,F3b Sampling frequency

Claims

[1] Control device (50) for digital beam shaping of an antenna array (100), the antenna array (100) comprising at least a first sub-aperture (110) for generating a plurality of first antenna cones (210) and a second sub-aperture (120) for generating a plurality of second antenna cones (220), the control device is configured to alternately arrange the first antenna cones (210) and the second antenna cones (220) side by side, wherein the first sub-aperture (110) and the second sub-aperture (120) are configured to utilize different sampling frequencies (Fs1, Fs2) and to perform subsampling in each case. [2] Control device (50) according to claim 1, wherein the subsampling extends to three Nyquist zones and the control device is configured to uniquely assign sampled received signals to the three Nyquist zones based on a frequency difference of sampling frequencies (F2a, F2b; F3a, F3b) of a received signal sampled at the different sampling frequencies, and to calculate for each sampled received signal a plurality of antenna cones (210, 220) belonging to the three Nyquist zones. [3] Control device (50) according to claim 1 or claim 2, further designed to to overlap the first antenna cones (210) and the second antenna cones (220); and / or to arrange the first antenna cones (210) and the second antenna cones (220) next to each other and to perform oversampling in the first sub-aperture (110) and the second sub-aperture (120) respectively. [4] Control device (50) according to claim 3, wherein at least some antenna cones (210, 220) have the same viewing direction and a coherent addition of associated antenna signals takes place. [5] Control device (50) according to one of claims 1 to 4, wherein the antenna array (100) has a plurality of sub-apertures (110, 120, 130, 140) arranged along rows and columns, wherein the first sub-aperture (110) and the second sub-aperture (120) are arranged adjacent along a row or a column. [6] Control device (50) according to claim 5, where all antenna cones (210, 220) of all sub-apertures (110, 120) overlap, and / or wherein all antenna cones (210, 220) are arranged next to each other in at least one row or at least one column to form several superimposed fans. [7] Control device (50) according to any one of claims 1 to 6, wherein the control device (50) is further designed to perform a bearing based on at least one of the following methods: - a phase monopulse method, - an amplitude monopulse method, - an interferometry, - a 4-quadrant monopulse method. [8] Control device (50) according to one of claims 1 to 7, which is further designed to direct an antenna cone (210, 220) constantly towards an observation object with each sub-aperture (110, 120). [9] Control device (50) according to one of claims 1 to 8, wherein the antenna array is operable in a frequency range from 200 MHz to 9 GHz or from 350 MHz to 6 GHz and the different sampling frequencies have a difference in the range of 150 MHz to 5,000 MHz or 250 MHz or 4,750 MHz. [10] Antenna array (100) comprising: several adjacent sub-apertures (110, 120), each comprising a plurality of antenna elements (111, 121), each sub-aperture (110, 120) being configured to generate a plurality of antenna cones (210, 220); and a control device (50) according to any one of claims 1 to 9. [11] Antenna array (100) according to claim 10, wherein all adjacent antenna elements (111, 121) have a predetermined distance. [12] Method for controlling an antenna array (100) according to claim 10 or claim 11, the method comprising: Arrange (S110) the first antenna cones (210) and the second antenna cones (220) alternately next to each other; and Sampling (S120) of received signals with different sampling frequencies (Fs1, Fs2) in the first sub-aperture (110) and the second sub-aperture (120), with one subsampling being performed in each case. [13] Method according to claim 12, wherein the method further comprises selecting one of the following modes by appropriately controlling the antenna array: a second mode (M2) where the first antenna cones (210) and the second antenna cones (220) are arranged side by side, with the first sub-aperture (110) and the second sub-aperture (120) each performing oversampling; a third mode (M3) where the first antenna cones (210) and the second antenna cones (220) are arranged overlapping; [14] Computer-readable storage medium with instructions stored thereon configured to execute the method of claim 12 or claim 13 when the instructions are executed on a data processing unit.

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