WO2005031921A1

WO2005031921A1 - Reflector antenna

Info

Publication number: WO2005031921A1
Application number: PCT/DE2004/001925
Authority: WO
Inventors: Lutz KÜHNKE; Markus Wintermantel
Original assignee: A.D.C. Automotive Distance Control Systems Gmbh
Priority date: 2003-09-25
Filing date: 2004-09-01
Publication date: 2005-04-07
Also published as: DE10344535A1; WO2005031921A8; DE112004002284D2; EP1665464A1

Abstract

The invention relates to a reflector antenna for bundling radar waves for distance sensors, especially distant view radar sensors for a motor vehicle. Said antenna comprises a main reflector and optionally one or more subreflectors. The main reflector and/or the optionally one or more subreflectors comprise at least one impurity that effects the broadening of the individual antenna beam, preferably a plurality of antenna beams, and/or a reduction of a side lobe of an antenna beam, preferably a plurality of antenna beams.

Description

reflector antenna

The present invention relates to a reflector antenna for bundling radar waves, in particular long-range vision radar sensors for a motor vehicle, with a main reflector and possibly one or more subreflectors.

The present invention also relates to a distance sensor, preferably a far-range radar distance sensor for a motor vehicle, in which

An angle measurement is carried out to compare the amplitude of adjacent antenna lobes.

The present invention also relates to a method for angle measurement with a radar sensor for a motor vehicle, in which the amplitudes of adjacent antenna lobes are compared and an angle measurement is carried out in accordance with the comparison.

Far-vision radar sensors with high concentration are frequently used for the motor vehicle sector, i.e. with the narrowest possible antenna beam to ensure a suitable resolution of targets in the field of view of the system.

A high concentration is z. B. achieved by means of lenses or by reflector antennas.

A method suitable for angle detection is based on the use of several separate antenna lobes which are offset in space and which are generated by spatially offset exciters for the radar waves in the lens or reflector system.

In systems of this type, the same antenna area or aperture is used for each beam. Therefore, the actual appearance of the rays and their characteristic values, e.g. Beam width, beam spacing and crossing points of the beams, not arbitrarily and not independently of each other.

A typical antenna pattern of a reflector system is shown in FIG. 1. With this plot of the amplitude A against the angle W of three individual beams (single lobes) 1, 2, 3 it can be seen that in for an angle detection important angle ranges there are very large amplitude ratios of directly adjacent individual beams. This is particularly pronounced at the locations of the maxima M1.M2.M3 of the individual beams 1, 2, 3.

The peculiarity shown arises in particular with lens antennas and

Arrangements with two reflectors, e.g. a planar folded reflector antenna as described in DE 198 48722 A1. Such antennas are designed for the smallest possible depth or focal length.

The antenna type is shown in more detail in Fig. 2. The antenna consists essentially of a main reflector 11, a plurality of exciters 12 and a subrefector 13. The subreflector 13 is realized by a carrier with an applied polarizer 16. The main reflector 11 and the sub-reflector 13 are at a distance 14 from one another. The main reflector 11 is formed by a planar dielectric with an arrangement of individual metallization structures 15, hereinafter also referred to as “metallizations”, on the front side, a so-called “reflect array”. With the arrangements of the metallization structures, when viewed from a radiation-optical point of view, a reflecting property of the reflector in question that varies continuously over the location on the surface in question is usually realized. The reflect array enables one

Rotation of the polarization plane of the radar waves by 90 °, so that they are first reflected on the sub-reflector 13 and can penetrate them unhindered after refection on the main reflector 11.

The spacing of the individual beams is decisively determined by the structural depth 14 and the design of the exciters 12, while the beam width is mainly dependent on the size of the main reflector 11. In particular, an antenna with a small overall depth 14, which is desirable for a compact overall arrangement, and at the same time with the largest possible dimension of the main reflector 11, which is necessary to achieve a large gain for the antenna, has the characteristic of the antenna beams described above. This leads to problems when evaluating several individual lobes for angle measurements based on amplitude information. If the information from two adjacent antenna beams with the greatest reception amplitude is used in each case in a sensor system, then angles from point sources can be unambiguously calculated over a specific spatial area from the amplitude ratio of the reception signals if the forms of the antenna diagram are known. The basic principle of such an angle measurement is known as a so-called diagram shift keying and is described in the literature, for example in Skolnik, MI, "Introduction to Radar Systems", McGraw-Hill Book Company, 1962.

For an antenna beam, small reception signals result in angular ranges with small values of the antenna pattern, which under certain circumstances can no longer be detected by a receiver. In other words, the range of the sensor system for the antenna beam under consideration is small in these areas. This is e.g. for angles close to 0 ° for the two outer rays 1, 3, e.g. in the area of intersection S1, the case. In this area, angles can no longer be determined at long measuring distances. In addition, problems with high side lobes can arise at relatively high frequencies, which are used in particular for motor vehicle radars. In the example shown, ambiguities in the amplitude ratios can arise, particularly for angles beyond ± 4 °, due to high side lobes which are unfavorably located at an angle.

In order to counter these problems, both broadening of the antenna beams and suitable control or limitation of the side lobe level are necessary. The broadening of the rays can be caused by

Reduction of the antenna area can be achieved, but there is quickly a significant reduction in profit and thus also a reduction in range. A spreading out of the individual beams of the antenna arrangement is therefore preferred, in particular for lower amplitude values.

The present invention is therefore based on the object of specifying a reflector antenna which enables sufficiently wide antenna beams in the low amplitude level and a low side lobe level without having to take into account the predetermined antenna area and the structural depth and the Total gain of the arrangement significant restrictions and deteriorations must be accepted. In addition, it is the object of this invention to provide a distance sensor and a method for forming an angle which works reliably for the entire detection area.

The task is solved by the independent claims. Preferred configurations are specified in the dependent claims.

The object is achieved according to the invention in that the main reflector and / or possibly the at least one sub-reflector has at least one defect which has an advantageous influence on the beam shape of the individual

Antenna beams, especially a broadening, from individual ones

Antenna beams and / or a reduction in at least one side lobe of the individual antenna beams. The term “fault location” is understood to mean a point or a region on the reflector or reflectors in question at which or in which the radiation properties differ from those of a conventionally designed, predetermined arrangement.

According to the invention, the main reflector and / or possibly the at least one sub-reflector has at least one metallization structure, preferably several

Metallization structures, and the metallization structure has at least one

Fault point.

According to the invention, at least one defect is on a main reflector by omitting at least one metallization structure, preferably several

Metallization structures, implemented in the arrangement of the metallization structures.

The main reflector is preferably designed as a "reflect array". The metallization structures on the main reflector are regularly arranged from rectangles, crosses, panes and the like on a grid with a preferably constant spacing. For certain applications, non-constant spacing and irregular arrangements are also provided. With the arrangements of the metallization structures according to the state of the art, one is usually considered optically in terms of radiation optics above the location on the respective one observed surface realizes continuously varying reflection properties of the respective reflector considered. In the case of such an arrangement, the term interference point is understood to mean a location or a region on the reflector of the antenna arrangement in question at which or in which the reflection properties deviate from those properties which continuously vary according to the prior art over the location on the surface in question in each case and / or the actual reflection location is varied in the direction orthogonal to the surface.

According to the invention, individual metallizations are omitted according to a deterministic method or a stochastic method with a defined probability distribution. This creates disturbances in the location-dependent behavior of the reflector, which leads to an undirected radiation of the power components present in the respective regions. In line with the requirements for the radiation diagrams described above, more and more imperfections are being used towards the edge of the reflector, as a result of which an overall decreasing amplitude assignment on the reflector arises. This leads to broader radar beams and lower beam lobes.

Depending on the desired diagram form, the omission of individual

Metallizations are used to a greater or lesser extent. Relatively few area portions of the metallizations are advantageously omitted in a range between 5% to 50%, preferably in a range between 5% to 35%, based on the total area of metallizations, as a result of which the antenna gain only compared to an arrangement with the same total area changed slightly.

It is also possible to achieve the desired effects e.g. B. primarily only for a certain cutting plane, e.g. B. to realize the sectional plane shown in Fig. 1, by the system or the exciter. In the orthogonal section plane, narrow antenna beams can still be used. So z. B. for azimuth and elevation of the antenna significantly different beam shapes can be realized. In addition, it is provided to arrange the interference points symmetrically to the antenna axis for certain embodiments.

Another preferred embodiment of the invention consists in not omitting individual metallization structures, but in changing their dimensions or shapes in a targeted manner according to a deterministic method or a stochastic method with a defined probability distribution, in relation to the dimensioning required for maximum gain of the antenna arrangement. With such a measure, an approximate extinction of individual scattered at the main reflector can be scattered in the far field of the arrangement

Performance shares are achieved. This results in a diagram formation in a very similar way as described above.

According to the invention, defects in the metallization structure on a main reflector, preferably in the form of a “reflect array”, are realized by means of a specific dimension and / or shape of the metallization structures. This means that the metallizations of the main reflector are purposefully and functionally dependent on the entire surface their dimensions or shapes. This leads to a defective phase assignment on the main reflector which is defective in comparison with a conventional design of the arrangement. When correctly designed, this essentially leads to the first side lobe of each antenna beam being fused to the main lobe and thus desired diagram shapes result.

According to the invention, the shape of one or more reflectors is changed in accordance with the circumferential angle of the respective reflector under consideration. Such a configuration is obtained if the boundary curve of the main reflector is not a circle, but rather is suitably shaped depending on the circumferential angle, so that, with reference to certain cutting planes, an outward decrease in amplitude assignment can also be realized. The entire

Reflector area is only moderately reduced, so the resulting loss of antenna gain is kept within acceptable limits and the antenna diagrams can be brought into the desired shape. It is provided according to the invention that a sub-reflector is used which, as a replacement or in addition to the main reflector, has at least one defect, in particular holes of very small diameter.

An advantageous development of the invention consists in impressing a suitable shape on the main reflector and / or the sub-reflector.

It is provided that defects are designed and / or arranged in such a way that they are only effective in one section plane of the antenna pattern.

The antenna is preferably a planar folded reflector antenna.

In another development of the invention, in the case of a folded reflector antenna, the subreflector on the side facing the main reflector is completely or partially covered with a dielectric of a suitable thickness.

Combinations of the measures described can also be used to optimally design the arrangement. The measures described can also be applied analogously to other antenna arrangements.

The object is also achieved by a distance sensor, in which it is provided that the angle measurement is carried out on the basis of a predetermined antenna lobe geometry and / or a determined or estimated antenna lobe geometry, the beam shape of the individual antenna beams being influenced, in particular widened and / or side lobes of the individual antenna beams have a reduced amplitude.

As a result, the sensor has no angular ranges with a significantly restricted range. In addition, it has a larger uniqueness range of the angle measurement compared to a conventional distance sensor. The object is also achieved by a method which is characterized in that an antenna lobe geometry is taken into account in the angle measurement, which is predetermined and / or determined or estimated, the beam shape of the individual antenna beams being advantageously influenced, in particular widened, and / or have a reduced amplitude in addition to lobes of the individual antenna beams. Signals from the two adjacent antenna lobes with the maximum reception amplitude are evaluated. The angle of incidence of a signal with known lobe geometries can then be clearly determined from the ratio of the associated amplitudes over a restricted angular range. For this purpose, the lobe geometries can either be approximated by angle-dependent functions or measured beforehand. When using an antenna arrangement according to the invention, this results in a distance sensor which, owing to the antenna properties described above, does not have any angular ranges with a significantly restricted range and, on the other hand, has a larger uniqueness range for the angle measurement than a conventionally designed arrangement.

Advantageous embodiments of the invention are explained by way of example on the basis of 3 illustrations (FIGS. 3 to 6).

3 shows an antenna diagram for a reflector antenna according to the invention.

Fig. 4 shows a reflector antenna according to the invention in a schematic representation in cross section.

FIG. 5 shows a top view of the main reflector of the planar folded reflector antenna according to FIG. 4.

FIG. 6 shows a plan view of the main reflector of the planar folded reflector antenna according to FIG. 4 with the targeted use of impurities. The plot of the amplitude A against the angle W in FIG. 3 shows three beams 5, 6, 7 with three maxima M5, M6, IVi7 which are distinguished from the diagram forms shown in FIG. 1 in the circumstances described by significantly better properties. There is a significantly higher intersection S2 of the outer lobes 5, 7 compared to the intersection S1 in FIG. 1 at 0 °. In addition, the first side lobes N6a, N6b of the middle beam only form at significantly larger angles. The facts are shown here using the example of three antenna lobes 5, 6, 7, but the principle also applies in the same way to a larger number of lobes.

The invention is explained below using a planar folded reflector antenna, as is known in principle from DE 198 48 722 A1 and to which reference is made here in full. The antenna is shown in FIG. 4. Analogously to the structure shown in FIG. 2, it has essentially three or fewer or more exciters 22, a subreflector 23 with an applied polarizer 26 and a main reflector 21, which is provided by a planar dielectric with an arrangement of individual metallization structures 25 on the front, a so-called reflect array. In the present example, this reflect array enables, in addition to locally varying reflection properties, a rotation of the polarization plane of the radar waves by 90 °, so that these are first reflected on the sub-reflector 23 and can pass through it unhindered after reflection on the main reflector 21. The locally varying reflection properties result from the locally different sizes of the metallization structures 25, as can be seen in FIG. 4 and the following figures in FIG. 6. In the case of a conventionally designed arrangement or reference design, the individual metallization structures are dimensioned such that they have reflection phases - which precisely compensate for the phase differences resulting from the different path lengths from the centrally attached exciter to the individual metallizations under consideration. In the context of the formula, the required reflection phase of the / th metallization results in π Φ, λ + W where λ is the free space wavelength, η is the distance between the exciter and the / th metallization and h is the distance 14 in FIG. 2.

With a given arrangement, this reference design leads to the greatest possible gain and the narrowest possible antenna beams, which leads to the problems explained above in an angle measurement based on amplitude comparison.

A preferred arrangement is to arrange the metallization structures 25 on the main reflector 21 regularly from rectangles, crosses, disks and the like on a grid with a constant spacing, but to omit individual metallizations according to a deterministic method or a stochastic method with a defined probability distribution.

This creates disturbances in the location-dependent behavior of the reflector, which leads to an undirected radiation of the power components present in the respective regions. Fig. 5 shows an embodiment without defects. FIG. 6 shows an embodiment based on FIG. 5 with defects according to the invention.

Alternatively or in addition, metallizations can also be specifically changed in their dimensions or shapes compared to their dimensioning required for maximum gain of the antenna arrangement according to a deterministic method or a stochastic method with a defined probability distribution. With such a measure, an approximate extinction of individual power components scattered at the main reflector can be achieved in the far field of the arrangement.

In contrast to the so-called “thinned arrays” described in some places in the literature (for example Skolnik, MI, “Introduction to Radar Systems”, McGraw-Hill Book Company, 1962), impurities are used here specifically for shaping the antenna beams in reflector antenna arrangements , whereby the defects are realized either by omitting them or by deliberately “detuning” metallizations. In a further embodiment, the metallizations of the main reflector are functionally, depending on the location, specifically changed in terms of their dimensions or shapes over the entire surface, which means an additional term dependent on r in the design specification given above. This is preferably done in addition to the formation of defects described above. This leads to a defined phase assignment on the main reflector which is defective in comparison with a conventional configuration of the arrangement, as a result of which the first side lobe of each antenna beam is fused to the main lobe and the desired diagram shape is obtained.

Claims

claims

1 . Reflector antenna for bundling radar waves, in particular remote view radar sensors for a motor vehicle, with a main reflector and possibly one or more subreflectors, characterized in that the main reflector and / or possibly the at least one subreflector has at least one fault location which advantageously influences the beam shape, in particular a broadening of individual antenna beams and / or a reduction in at least one side lobe of the individual antenna beams.

2. reflector antenna according to claim 1, characterized in that the main reflector and / or possibly the at least one sub-reflector has at least one metallization structure, preferably a plurality of metallization structures, which has at least one defect.

3. reflector antenna according to claim 2, characterized in that at least one defect on a main reflector is realized by omitting at least one metallization structure, preferably a plurality of metallization structures, in the arrangement of the metallization structures.

4. reflector antenna according to claim 2 or 3, characterized in that at least one defect on a main reflector is realized by a certain dimension and / or shape of at least one metallization structure.

5. reflector antenna according to one of claims 1 to 4, characterized in that at least one defect on a main reflector is functionally changed depending on the location compared to an interpretation required for maximum gain of the reflector antenna in its dimensions or shapes.

6. reflector antenna according to one of claims 1 to 5, characterized in that the shape of one or more reflectors is changed in accordance with the circumferential angle of the respective reflector under consideration.

7. reflector antenna according to any one of claims 1 to 6, characterized in that a sub-reflector has at least one defect.

8. reflector antenna according to one of claims 1 to 7, characterized in that the main and / or the sub-reflector has an embossed shape.

9. reflector antenna according to one of claims 1 to 8, characterized in that at least one fault location is formed and / or arranged so that it is effective only in one section plane of the antenna pattern.

10. reflector antenna according to one of claims 1 to 9, characterized in that the antenna is a planar folded reflector antenna.

11. Distance sensor, preferably long-range radar distance sensor for a motor vehicle, in particular with a reflector antenna according to one of the preceding claims, in which an angle measurement is carried out by comparing the amplitude of adjacent antenna lobes, characterized in that the angle measurement is based on a predetermined antenna lobe geometry and / or a determined or estimated Antenna lobe geometry takes place, the beam shape of the individual antenna beams being advantageously influenced, in particular widened, and / or side lobes of the individual antenna beams having a reduced amplitude.

2. Method for angle measurement with a radar sensor for a motor vehicle, in which the amplitudes of adjacent antenna lobes are compared and an angle measurement is carried out in accordance with the comparison, characterized in that an antenna lobe geometry is taken into account in the angle measurement, which geometry is predetermined and / or determined or is estimated, the beam shape of the individual antenna beams being advantageously influenced, in particular widened, and / or side lobes of the individual antenna beams having a reduced amplitude.