Separation of transmit and receive apertures at different heights along a horizontal antenna aperture

Abstract

The invention relates to an antenna structure (100) for a vehicle radar system with distributed radar antennas (140, 150, 160), wherein the radar antennas (140, 150, 160) comprise separately configured transmitting antennas (150, 150-n) and receiving antennas (160, 160-n), wherein the transmitting antennas (150, 150-n) and receiving antennas (160, 160-n) are each spaced apart from one another along a spatial direction (330), wherein the receiving antennas (160, 160-k) arranged and spaced apart from one another along the one spatial direction (330) have a distance transverse to the one spatial direction (330) from transmitting antennas (150, 150-n) arranged adjacent with respect to the one spatial direction (330), which are spaced apart from one another along the one spatial direction (330). are arranged at a distance from each other.

Description

[0001] The invention relates to radar antenna structures, in particular distributed radar antenna structures, which form a distributed, preferably sparsely populated, antenna aperture.

[0002] Radar systems with distributed radar antennas, also known as "distributed" or "bi-static" multiple-input multiple-output (MIMO) radar systems, observe potential locations in the surrounding area from different angles to minimize fluctuation losses. Calculating the object coordinates before coherently summing the individual signals is significantly more complex and computationally intensive compared to monostatic radar systems due to the different signal propagation times between the various antennas. This is also true for radar systems where the transmitting and receiving antennas are located at the same or nearly the same position.

[0003] Due to the operating mode of common automotive radar systems, continuous transmission and reception processes occur simultaneously based on a frequency-modulated signal model. Radar signal information is transmitted from a central station to transmitting modules, which determine the transmission of the radar signals. Receiving modules, coupled with receiving antennas, then transmit echo information derived from radar echo signals back to the central station for joint evaluation.

[0004] Due to the simultaneous transmission and reception, and as a consequence of the high integration density of the transmitting and receiving antennas and their associated spatial proximity, crosstalk of the emitted signal power from a transmitting antenna directly into a receiving antenna and its receiver unit can occur. This is disadvantageous because the crosstalk signal power can interfere with the signal power of the radar echo signal, potentially completely masking the useful signal in the form of the radar echo signal, rendering it undetectable, or causing components in the receiver module to become saturated as a result of the crosstalk and interference.

[0005] The invention is therefore based on the objective of creating an improved radar antenna structure in which the evaluation of the useful signals in the form of radar echo signals is improved.

[0006] The invention is solved according to the invention by a radar antenna structure with the features of claim 1. Advantageous embodiments of the invention are set forth in the dependent claims.

[0007] The invention is based on the idea of ​​spatially separating transmitting and receiving antennas arranged adjacent to and nested below each other along a spatial direction in the prior art, such that the transmitting antennas are at least locally spaced from the adjacent transmitting antennas arranged along the same spatial direction, perpendicular to the arrangement direction of the transmitting antennas along that spatial direction. If the antennas are arranged, for example, along a horizontal line, then the transmitting and receiving antennas are at least locally spaced from each other vertically.

[0008] In particular, an antenna arrangement or antenna structure for a vehicle radar system with distributed radar antennas is proposed, wherein the radar antennas comprise separately designed transmitting and receiving antennas, transmitting antennas being arranged spaced apart from one another along one spatial direction, and receiving antennas being arranged spaced apart from one another along one spatial direction, wherein the receiving antennas arranged and spaced apart from one another along one spatial direction are at least a distance transverse to that spatial direction from transmitting antennas arranged adjacent to one another along that spatial direction. This antenna structure or antenna arrangement offers the advantage that crosstalk from the transmitting antennas to the receiving antennas can be almost completely eliminated.

[0009] In an antenna structure with a two-dimensional design, where part of the radar antennas are oriented along one spatial direction and another part along a different spatial direction, preferably oriented almost perpendicular to the first spatial direction, only the transmitting and receiving antennas of the first spatial direction are spaced apart from each other at least locally, perpendicular to that first spatial direction. In a vehicle radar system, this first spatial direction typically coincides with a horizontal line.

[0010] The individual radar antennas preferably have a preferred direction with regard to their positioning, which corresponds to the direction perpendicular to the one spatial direction along which a main emission of the radar signal is focused.

[0011] In real-world antenna structures, where radar antennas are integrated into vehicle components, such as a bumper or along an edge or edges of a windshield, the structural elements that define at least the arrangement of the transmitting or receiving antenna positions are often curved. This means that, for example, the transmitting antennas or, alternatively, the receiving antennas located at the top edge of a windshield, arranged along the horizontal axis (one spatial direction), are not all aligned in a straight line. Rather, they are arranged along one or two curves with a slight curvature along that single spatial direction.Nevertheless, in a preferred embodiment, the arrangement of the transmitting antennas and the receiving antennas is such that the receiving antennas, which are arranged apart from each other along one spatial direction, are spaced apart from all transmitting antennas perpendicular to that one spatial direction, which are arranged apart from each other along that one spatial direction.

[0012] In order to define a spatial direction in real antenna structures, one embodiment provides that the spatial direction coincides with a straight line resulting from an approximation where the sum of the squared distances of the antenna positions of the receiving antennas or the transmitting antennas or the transmitting and receiving antennas together is minimal from the approximated straight line, taking into account the respective transmitting and / or receiving antennas that are arranged separately from each other along this approximated spatial direction.

[0013] Particularly suitable antenna structures are obtained in an embodiment in which a receiving antenna plane and a transmitting antenna plane exist, aligned parallel and spaced apart perpendicular to one spatial direction, wherein the receiving antennas, spaced apart from each other along one spatial direction, lie in a receiving antenna plane or are spaced closer to it than to the transmitting antenna plane, and the transmitting antennas, spaced apart from each other along one spatial direction, lie in the transmitting antenna plane or are spaced closer to it than to the receiving antenna plane. The planes, i.e., the receiving antenna plane and the transmitting antenna plane, can be designed for such an arrangement such that the specified conditions are met.

[0014] Preferably, the arrangement is configured such that the transmitting antenna plane and the receiving antenna plane are spaced sufficiently apart that, when a transmit signal is radiated with a specified radiated power via a transmitting antenna located in one of the transmitting antenna planes, the crosstalk of the transmit signal in each of the receiving antennas located in the receiving antenna plane is on the order of the noise of the receiving antenna signal that would be detected without transmitting a signal via any of the receiving antennas of the antenna arrangement. This preferably also applies if there is a slight curvature in the array curves on which the receiving and transmitting antennas are arranged at a distance from each other. The two array curves for the transmitting and receiving antennas are preferably oriented parallel to each other and have a corresponding separation along a direction perpendicular to them.All along the arrangement curves, the transmitting and receiving antennas, which are arranged at the same position along the arrangement curves, preferably have the same distance perpendicular to the arrangement curves.

[0015] Preferably, however, the transmitting and receiving antennas are arranged in parallel and spaced-apart planes, namely the transmitting and receiving antenna plane and the receiving antenna plane. If the transmitting and / or receiving antennas have a preferred orientation, e.g., a dipole-like characteristic, then the orientation perpendicular to one spatial direction is preferably parallel to this dipole orientation of the transmitting and / or receiving antennas. This results in minimal crosstalk from the transmitting antennas and their transmit power to the receiving antennas and their processing electronics in receiver modules.

[0016] The invention is explained in more detail below with reference to a drawing. The drawing shows: Fig. 1 an antenna diagram of an antenna element with a widened main lobe and widely extending side lobes; Fig. 2 an antenna diagram of an antenna element with a narrow main lobe and side lobes, the latter being able to propagate into neighboring antennas; Fig. 3 a schematic representation of an antenna structure consisting of sparsely distributed transmitting and receiving antennas along a spatial direction, spaced apart from each other perpendicular to that spatial direction; Fig. 4 Another embodiment of an antenna arrangement with sparsely distributed transmitting and receiving antennas spaced apart from one another transversely to one spatial direction, wherein a portion of the receiving antennas forms a uniform linear antenna array; and Fig. 5 Another schematic representation of an antenna arrangement of transmitting and receiving antennas along a spatial direction, wherein the transmitting antennas and the receiving antennas are separated from each other transversely to that spatial direction, wherein at least some of the receiving antennas are spaced apart from each other by a distance equal to half a wavelength or an integer multiple of half the wavelength of the radar radiation used for emission.

[0017] Fig. Figure 1 schematically shows an antenna diagram. An angular range 20 from -90° to +90° is plotted. A zero-angle position 21 indicates the desired radiation direction of a transmitting antenna 50 located at antenna position 51. The radial distance of a position on the antenna diagram is correlated with the radiated power at the angle that the position exhibits on the antenna diagram within the angular range 20. The in Fig. The antenna diagram shown in Figure 1 has a wide main lobe (60°) and weak side lobes (70°).

[0018] In Fig. Figure 2 shows another schematic antenna diagram 10. Identical technical features are indicated in all figures with the same reference numerals. In this embodiment of the antenna, a narrow main lobe is radiated in the desired direction at 0°. However, this antenna exhibits narrow, pronounced side lobes.

[0019] Antennas that match the two antenna diagrams 10 after Fig. 1 and Fig. 2 correspond, tend to cause crosstalk of radiated radar signal power into a neighboring receiving antenna, which is arranged adjacently along the +90° / -90° direction corresponding to a horizontal axis 30. Such crosstalk of the radiated radar signal directly into one of the neighboring receiving antennas (not shown) can cause radar echo signals, which represent the useful signal, to be masked and / or saturate electronic components of a receiver module coupled to the receiving antenna.

[0020] Fig. Figure 3 shows an antenna arrangement or antenna structure 100 with antennas 140. The antennas 140 comprise transmitting antennas 150, 150-n and receiving antennas 160, 160-k. n and k are indices for numbering the individual transmitting and receiving antennas, respectively. The transmitting antennas 150 and the receiving antennas 160 are each formed separately. The transmitting antennas 150, 150-n are spaced apart from each other along a spatial direction 330. The receiving antennas 160, 160-k are also spaced apart from each other along this same spatial direction 330.

[0021] One spatial direction coincides with a y-axis 230 of a coordinate system 200. An x-axis 220 points in a direction corresponding to the intended radiation direction of the transmitting antennas, i.e., their 0° position. A z-axis 240 is perpendicular to the x-axis 220 and the y-axis 230 at an origin 210 of the coordinate system 200.

[0022] In this embodiment, all transmitting antennas 150, 150-n are arranged in a transmitting antenna plane 450. The receiving antennas 160, 160-k are arranged accordingly in a receiving antenna plane 460. The transmitting antenna plane 450 and the receiving antenna plane 460 are oriented parallel to each other and spaced apart perpendicular to one principal direction 330, i.e., along a transverse direction 340. A distance along the transverse direction 340, i.e., perpendicular to one spatial direction 330, between the transmitting antennas 150 and the receiving antennas 160, is preferably selected such that, when radiating a target transmit power corresponding to a maximum intended transmit power of the transmitting antenna, crosstalk into a receiving antenna that is immediately adjacent, for example, with respect to one spatial direction in the coordinate system 200, has the same y-coordinate value.at the same position with respect to one spatial direction 330, a signal caused by crosstalk in the receiving antenna is not greater than a detected noise of this receiving antenna when no radar signal is emitted via any of the transmitting antennas.

[0023] In the illustrated embodiment, an arrangement curve 350, defined by the antenna positions of the transmitting antennas, and an arrangement curve 360, defined by the antenna positions of the receiving antennas, are straight lines. They lie in the transmitting antenna plane 450 and the receiving antenna plane 460, respectively. Thus, in the illustrated embodiment, neither arrangement curve 350 nor 360 is curved. If an antenna structure is integrated, for example, into the windshield of a motor vehicle, such that the receiving or transmitting antennas follow, for example, an upper edge of the windshield, the arrangement curves in real embodiments often exhibit a slight curvature. In this case, both the arrangement curve 350 of the transmitting antennas 150 and the arrangement curve 360 ​​of the receiving antennas 160 are preferably curved in the same way. With such a configuration, one spatial direction can be determined, or...These are defined such that they coincide with or are parallel to a straight line adapted to the transmitting antenna positions, the receiving antenna positions, or both, with the approximation preferably being performed in such a way that the squared distances of the antenna positions to the approximated line are minimized. Only the transmitting and / or receiving antennas that are also arranged along one spatial direction in the antenna structure are considered. This applies to situations in which the antenna structure spans a two-dimensional antenna aperture, with the transmitting and receiving antennas arranged along the second spatial direction, for example, along the z-axis in the example shown.It should be noted that, in order to avoid crosstalk, of course no transmitting antenna is arranged along the z-axis in such a way that it is not spaced perpendicular to one spatial direction with respect to the receiving antennas that are arranged along this one spatial direction.

[0024] Each transmitting antenna is connected to a transmitting module 500, and each receiving antenna is connected to a receiving module 600. Their operation will be roughly described here for embodiments typical of an antenna structure used with a photonic multi-input multi-output radar system.

[0025] In this process, radar signal information is transmitted via an optical carrier signal on an optical fiber 510 to the corresponding transmitter module. This fiber is coupled to the transmitter module at a fiber connector 520. At a coupling element 530, the carrier signal is coupled into the semiconductor structure 505, which may include an integrated photonic electronic semiconductor circuit. At a converter device 540, which is designed, for example, as a photodiode 541, the radar signal information is separated from the optical carrier signal and converted into an electronic signal. This electronic signal is preferably multiplied with respect to frequency at a frequency multiplier 550 and amplified in a transmitter amplifier 560 before being emitted as a radar signal via the corresponding transmitting antenna 150.

[0026] A receiver module 600 is also coupled to an optical fiber 610, which is connected to the semiconductor structure 605 of the receiver module 600 via a fiber connector 620. A coupling element 640 ensures that the optical carrier signal with the radar signal information modulated on it is coupled into the semiconductor structure 605 of the receiver module. At a converter device 640, which is also preferably designed as a photodiode 641, the radar signal information is again separated and converted into an electronic signal, which is fed to a mixer 670. A radar echo signal received at the receiving antenna 160 is also forwarded to the mixer 670 via a receiving amplifier 660. The mixer derives an intermediate frequency signal from the radar echo signal by means of a mixing process, in which echo information is contained.This signal is modulated, for example, onto the optical carrier signal looped through the semiconductor structure 605 via a further coupling device 680 and transmitted to the central station for evaluation via another optical fiber 700, which is connected to another fiber connector. Due to the use of one or more optical carrier signals, all provided by the central station, a coherent evaluation of the received signals from all receiving antennas is possible together at the central station.

[0027] Preferably, the transmitting and receiving antennas are arranged along one spatial direction in such a way that they form a sparsely populated antenna array, so that the largest possible virtual antenna aperture can be created with as few antennas as possible.

[0028] In Fig. 4 and Fig. Figure 5 shows further embodiments of antenna structures in which the receiving antennas 160 and the transmitting antennas 150 are spaced apart from each other transversely to one spatial direction 330, along which they are arranged spaced apart from each other. In the embodiment according to Fig. 4. A portion of the receiving antennas 160-3 to 160-6 forms a so-called uniform linear array (ULA). This array is characterized by the fact that longitudinal spacings 336-3 to 336-5, i.e., the spacings between the receiving antenna pairs 160-3, 160-4; 160-4, 160-5; 160-5, 160-6, are equal and correspond to half the wavelength of the emitted radar signal. Such a substructure of a uniform linear array offers advantages for some evaluation methods.

[0029] In Fig.Figure 5 shows a further embodiment in which a virtual uniform linear antenna structure is created by having a portion of the receiving antennas 160-1, 160-2, 160-3 either have a longitudinal spacing 336-k, for example 336-2, between the receiving antennas 160-2 and 160-3, which corresponds to half the wavelength of the emitted radar radiation, or the longitudinal spacing 336-k, for example 336-1, corresponds to an integer multiple of the wavelength of the emitted radar radiation, as is the case between the receiving antenna 150-1 and the receiving antenna 150-2 in the illustrated embodiment. The remaining receiving antennas can be spaced apart at any longitudinal distance 336-k from this, as is indicated, for example, for the distance between the receiving antenna 160-3 and the receiving antenna 160-4, whose longitudinal distance 336-3 corresponds to a real multiple of half the wavelength of the emitted radar radiation.Overall, the arrangement is designed to create an optimal, sparse antenna array that spans the largest possible virtual antenna aperture.

[0030] It is understood by those skilled in the art that only exemplary embodiments are described and that the features shown in connection with the various embodiments can be combined arbitrarily. Reference symbol list 10 Antenna diagram 11 Chart line 20 Angle range / Azimuth angle 21 0° position 30 horizontal axis 40 radial spacing (measure of power) 50 transmitting antenna 51 Antenna position 60 broad main leg 61 Narrow Main Leg 70 weak side clubs 71 narrow, pronounced side clubs 100 antenna structure 140 antennas 150, 150-n transmitting antennas 160, 160-k receiving antennas 200 coordinate system 210 Origin 220 x-direction 230 y-direction 240 z-direction 330 a spatial direction 335-h longitudinal spacing 336-k longitudinal spacing 340 transverse direction 350 Arrangement curve 351 approximated straight line 360° arrangement curve 351 approximated straight line 450 transmitting antenna level 460 Receiving antenna level 500 transmitter module 505 Semiconductor structure 510 optical fiber 520 fiber connectors 530 coupling element 540 converter unit 541 Photodiode 550 frequency multipliers 560 transmitting amplifiers 600 receiver module 610 optical fiber 620 fiber connectors 630 coupling element 640 converter unit 641 Photodiode 660 receiver amplifiers 670 mixers 680 additional coupling devices 690 additional fiber connectors 700 more fibers

Claims

Antenna structure (100) for a vehicle radar system with distributed radar antennas (140, 150, 160), wherein the radar antennas (140, 150, 160) comprise separately configured transmitting antennas (150, 150-n) and receiving antennas (160, 160-n), wherein transmitting antennas (150, 150-n) are arranged spaced apart from one another along one spatial direction (330) and receiving antennas (160, 160-n) are arranged spaced apart from one another along one spatial direction (330), characterized in that the receiving antennas (160, 160-k) arranged and spaced apart from one another along one spatial direction (330) are at least a distance perpendicular to one spatial direction (330) from transmitting antennas (150, 160-n) arranged adjacent with respect to one spatial direction (330). 150-n) which are spaced apart from each other along one spatial direction (330). Antenna structure (100) according to claim 1, characterized in that the receiving antennas (160, 160-k), which are arranged apart from each other along one spatial direction (330), are spaced apart from all transmitting antennas (150, 150-n) transversely to one spatial direction (330), which are arranged apart from each other along one spatial direction (330). Antenna structure (100) according to claim 1 or 2, characterized in that one spatial direction (330) coincides with a straight line resulting from an approximation in which the sum of the squared distances of the antenna positions of the receiving antennas (160, 160-k) or the transmitting antennas (150, 150-n) or the transmitting and receiving antennas (160, 160-k) together is minimal from the approximated straight line, taking into account the respective transmitting and / or receiving antennas (160, 160-k) that are arranged separately from each other along this approximated spatial direction (330). Antenna structure (100) according to one of the preceding claims, characterized in that a receiving antenna plane (460) and a transmitting antenna plane (450) exist, which are aligned parallel and spaced apart transversely to one spatial direction (330), wherein the receiving antennas (160, 160-k), which are spaced apart from each other along one spatial direction (330), lie in a receiving antenna plane (460) or have a smaller distance to it than to the transmitting antenna plane (450), and the transmitting antennas (150, 150-n), which are spaced apart from each other along one spatial direction (330), lie in the transmitting antenna plane (450) or have a smaller distance to it than to the receiving antenna plane (460). Antenna structure (100) according to one of the preceding claims, characterized in that the transmitting antennas (150) and the receiving antennas (160) are separated from each other transversely to one spatial direction (330) to such an extent that when a transmit signal with a nominal radiation power is emitted via a transmitting antenna (150, 150-n) arranged along one spatial direction (330), the crosstalk of the transmit signal in each of the receiving antennas (160, 160-k) arranged along one spatial direction (330) is on the order of the noise of the receiving antenna signal that is detected without an emission of a transmit signal via one of the receiving antennas (160, 160-k) of the antenna arrangement. Antenna structure (100) according to one of the preceding claims, characterized in that the receiving antennas (160, 160-k) are spaced apart from the receiving antennas (160, 160-k) parallel to a “dipole direction” or distinction direction of the transmitting antennas (150, 150-n). Antenna structure (100) according to one of the preceding claims, characterized in that a part of the receiving antennas (160, 160-k) form a uniform linear antenna array in which the receiving antennas (160, 160-k) adjacent with respect to one spatial direction (330) have the same longitudinal spacing 336-k in pairs, which is less than or equal to half a wavelength of the radar signal radiation emitted via the transmitting antennas (150, 150-n). Antenna structure (100) according to claim 7, characterized in that the wavelength of the radar signal radiation in a frequency-modulated radar signal corresponds to the wavelength corresponding to the mean frequency.

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