US 20050104795 A1
An antenna array, especially for spacing ascertainment or speed ascertainment in the surroundings of motor vehicles, includes devices for transmitting and/or receiving signal waves, which includes a shielding layer construction, made up of at least two layers, which includes the transmitting or receiving devices at least in part. To achieve above all a good immunity to interference, the antenna array includes a differential input buried in a dielectric layer and it includes a transmitting and/or receiving dipole, which is composed of two separate dipole halves.
1. An antenna array, for ascertaining vehicle spacing or vehicle speed in a surrounding of a motor vehicle, comprising:
at least one transmitting/receiving device to at least one of transmit and receive signal waves, wherein a shielding layer construction includes at least one dielectric layer, which includes the transmitting or receiving devices at least in part, and a shielding layer;
wherein the antenna array includes a differential input and a transmitting/receiving dipole to at least one of transmit and receive, wherein the dipole includes two separate dipole halves.
2. The antenna array of
3. The antenna array of
a dipole-patch coupling having a patch at a predetermined distance from the dipole.
4. The antenna array of
5. The antenna array of
6. The antenna array of
7. The antenna array of
8. The antenna array of
9. The antenna array of
10. The antenna array of
11. The antenna array of
12. The antenna array of
13. The antenna array of
14. The antenna array of
15. The antenna array of
The present invention relates to an antenna array and especially to an antenna array made by a layer construction method for ascertaining vehicle spacing or speed in the surroundings of motor vehicles.
There are systems in which the distance and the speeds are measured by radar (microwaves), especially short-range radar. In this context, above all, small antenna arrays in compact layer building method are used. In the antenna arrays in this field having microstrip feeding, coplanar feeding or slot coupling, asymmetrical excitation is always or generally involved. In asymmetrical excitation, the signal lines (feed lines and return lines) are not developed in the same way, as in symmetrical excitation, but rather, the signal is on the feed line and the “return line” is at ground, and is usually developed as a metallic plane. In asymmetrical excitation, what may be particularly disadvantageous is the susceptibility to failure by spurious radiation from outside, which corrupts the signal.
In a large-scale integration of circuit components, because of its immunity to interference, differential, i.e. symmetrical inputs and outputs may be used. In order to be able to carry out asymmetrical feeding, in this context, costly impedance-matching sections or external baluns (balance) have to be employed. An additional disadvantage of asymmetrical excitation is radiation losses in response to a patch coupling because of the required field vector rotation of the electrical field. By patches, one is given to understand metallic radiation-emissive surfaces which are mostly rectangular.
An example of an antenna array, constructed of several layers, having asymmetrical excitation, is referred to in German patent document no. 100 63 437, in which there are two potential surfaces at ground, the so-called earth planes, each outside and parallel to the plane of stratification. Close to below the earth plane, facing the transmitting direction, which has a coupling slot, an electrical connecting section is situated. The radiation exiting from the coupling slot couples into a patch lying above it. In this context, the patch is the transmitting and/or receiving device. It is true that, in response to this screening arrangement, to a certain extent, spurious radiation from outside is deterred and radiation of the useful radiation in undesired directions is delimited, but the disadvantages caused by the asymmetrical excitation are still not satisfactorily removed.
Using the measures described herein, an antenna array that is easy to manufacture in a layer construction method is made available, particularly for ascertaining distance apart and speed in the surroundings of motor vehicles, which has an improved immunity to interference. Besides the arrangements for transmitting and/or receiving, the antenna array includes layers of dielectric material. Conductive metal is used for shielding. In the differential input according to the exemplary embodiment of the present invention, two signal feeds running in parallel connect two separate dipole halves. The signals in the two lines are in phase opposition. Thereby, in the lines running parallel, an undesired radiation is delimited by a quenching signal addition. On the other hand, the signals supplement one another at the signal output, when they are subtracted from one another. However, spurious radiation from outside appears on both signal feeds in phase, so that it is eliminated by a subtraction.
Furthermore, because of the differential input of the antenna array according to the present invention, when using differential inputs and outputs for a large-scale integration of circuit components, the costly impedance-matching section or external baluns are unnecessary.
One exemplary embodiment is an integration of the two signal feeds of the input into the layer construction, which achieves a compact system, such as by microstrip feeding.
Another exemplary embodiment includes a dipole-patch coupling with a patch at a predetermined distance from the dipole. A relatively high bandwidth is achieved by a choice of geometry having two offset resonance frequencies. An especially good coupling comes about using a distance in the range of 0.01 to 0.2 times the wavelength of the radiation.
According to another exemplary embodiment, dipole and patch are positioned in parallel, and the dipole to the feed lines is oriented in such a way that the vector(s) of the electrical field lie in parallel in patch and dipole, and have the same direction. A field vector rotation and radiation losses connected therewith do not appear.
According to still another exemplary embodiment of the antenna array according to the present invention, the two signal feeds are a parallel system of two printed or etched lines, and in the layer construction, two symmetrically arranged dipole halves are provided in a subdivision (into smaller chambers), which are conductingly connected with one feed line each. In a layer construction, etched or printed lines are simple and well suited feedings. The common subdivision of the symmetrically situated dipole halves spatially limits the radiation and thereby improves the radiation characteristics.
According to another exemplary embodiment, the signal lines are buried in a di-electrical layer of the layer construction, so that the signal lines do not run along the surface, but in a lower layer. Thereby, according to the exemplary embodiment of the present invention, crossings of lines in a supply network are easy to achieve in the case of the interconnection of several antenna elements, without bonds or air bridges, in that a line is moved on a small scale in another plane of stratification.
Another exemplary embodiment of the present invention, in the form of the embodiment having buried signal lines, is an external earth plane that faces the transmission direction and is situated parallel to the dielectrical layer, which, as seen from opposite to the transmission direction, is located before the signal lines. Thereby, the signal lines in transmission direction lie behind a screening earth plane, which has the effect of decoupling between feeding and radiated radiation.
Yet another exemplary embodiment, with supply lines buried, includes a connection in the middle of the inner edge of the respective dipole halves using through-hole plating.
According to another exemplary development, the dipole is surrounded by a ground bordering that shields perpendicular to the layer between the two outer sides that exist parallel to the layering. Thereby shielding perpendicular to the plane of stratification is achieved, thus at the edge, for instance, on the right and left in
According to another exemplary embodiment, the dipole and/or the patch are on both sides, in a wedge-shaped manner, pointed towards the middle, in a planar manner. The bandwidth is increased by this biconical planar shape.
According to another exemplary embodiment, the distance between two signal supply lines is equivalent to about one tenth to one hundredth of the wavelength of the radiated radiation, and the lines are activated in phase opposition. Thereby, there occurs an extensive extinction of the far field of the leakage radiation outgoing from the signal lines.
According to yet another exemplary embodiment, the antenna array according to the present invention includes several transmitting and/or receiving devices that are positioned at a predetermined distance from one another. These, for example, form a series or a field. Because of that, the directivity characteristic and the gain of the radiation are further improved. It is especially advantageous to have an arrangement of the sending and/or the receiving directions in series, similar to a Bruce Array. By this arrangement of the neighboring transmitting and/or receiving devices at a distance of about one-half of a wavelength, one achieves an especially good supplementation of the emission in the provided radiation direction.
Although able to be used in any field of application in the antenna sector, the exemplary embodiment of the present invention and the problem on which it is based are explained with reference to an antenna array on board a motor vehicle to ascertain vehicle spacing or speed, in the surroundings of motor vehicles.
In the figures, the same reference numbers designate the same or functionally equivalent components. All the drawings are schematic, and, for the purpose of increased clarity of the topology of each respective layer configuration, the illustrations are not to scale.
The distance is not limited to this measure, but rather, it may vary. A range of from 0.01 to 0.2 of the wavelength is very suitable. The transmitted radiation has a frequency in a range about 26 GHz. Because of the dielectric load and coupling with dipole 5, patch 3 is a little shorter than the air wavelength, but measures approximately one-half of the wavelength of the transmitted radiation.
In this context, one takes into account reductions in wavelength because of end effects and slenderness factors. Patch 3, for example, is fastened to the unit housing (not shown) free above dipole 5, or, using a foam layer, on dipole 5. According to the exemplary embodiment of the present invention, dipole 5 is made up of two separate rectangular metal areas which are applied onto a dielectric substrate 11, such as a printed-circuit board, a ceramic or a soft board material. The dipole halves each have a length of approximately one-quarter of a wavelength. In this context, the wavelength is not assessed in air, but effectively loaded by the dielectric substance.
According to the exemplary embodiment of the present invention, each individual dipole half is fed using a signal supply line 7. The two signal supply lines 7 are situated in parallel, and thus, according to the exemplary embodiment of the present invention, they form a differential input. They run on the surface of substrate layer 11, and are, for instance, printed or etched. On substrate layer 11 there has also been applied a metallic earth plane 9 screening off the radiation, which has recesses only in the area of signal supply lines 7 and of dipole 5. In addition, there is a straight-through, screening off, metallic earth plane on the not visible back side of antenna array 1.
Dipole 5 and patch 3 are situated parallel to each other, and the two signal supply lines 7 run perpendicular thereto. With that, field vectors 13 of the electrical field of dipole 5, of patch 3 and of supply lines 7 lie parallel to one another, and point in the same direction.
A third exemplary embodiment of antenna array 1 according to the present invention is shown in
The two parallel running signal supply lines 7 may be recognized also in
The entire layer construction is shown in
Patch 3 is applied over the layers that are firmly connected to one another. The two dipole halves 5 are located to the right and the left of the middle of the uppermost layer, and enclose a central air gap. On the outside, too, there follows in each case an air gap that separates dipoles 5 from upper ground covering 9.
Lying below this, there follows a first substrate layer 11A which is interrupted by through-hole contacting 19 (vias), which lead to signal supply lines 7, which are situated in a still deeper following substrate layer 11B. Signal supply lines 7 are formed as relatively thin, lineal layer structure, in comparison to substrate layer thickness. Thus, the two signal supply lines 7 are in electrical contact with the halves of dipole 5 lying above with the aid of through-hole plating 19.
After an additional insulating substrate layer 11C, the layer construction closes towards the bottom with an additional metallic grounding bar 9. The two outside grounding bars 9 are connected conductingly to each other by metallic chamber strips 15 that run through substrate layers 11. The entire ground shielding 9, 15 forms a subdivision of dipole 5. It should still be added that all metal structures are shown quite in excess in their thickness (layer thickness). The metal layers may have a thickness of ca 1% to ca 20% of the thickness of the substrate layers.
The structure shown in
The distance between two adjacent dipoles 5 is approximately one-half wavelength of the transmitted radiation. The layer in which buried signal supply lines 7 run is shown schematically in the view of
According to the exemplary embodiment of the present invention, signal supply lines 7 lead parallel under the respective separate halves of central dipole 5, which are located in the above layer, and are connected to these using vias 19. In each case, from the outer side of one half of central dipole 5, vias 19 lead down to supply lines 17 in the line's plane of stratification, and the latter are led away from the antennas at right angles. These lead, via two additional right-angle bends in the wiring plane, under the outer edge of the respectively adjacent dipole 5, which is located in the layer above it (not shown), and are connected to it (the edge) using vias 19.
Such a conducting supply connection 17 repeats itself in each case to the outer dipoles 5. In this context, the length of the edges of the respective U-shaped supply line 17, which connects adjacent dipoles 5 to one another, amounts to about one-half a wavelength of the transmitted radiation. Due to this construction, the radiation is amplified in the direction of transmission, and the radiation of supply lines 17 perpendicular to this direction is largely suppressed because of mutual canceling out. The metallic chamber strips 15 which have cut-outs only at the breakthroughs of signal supply lines or supply lines 7, 17, form a lateral ground shielding.
Thus, the antenna array according to the exemplary embodiment of the present invention may have a whole field of transmitting and receiving devices. Antennas according to the exemplary embodiment of the present invention may, for example, also be used for a lifting height regulation, in the field of vehicle communications, for tire pressure data transmission or, for instance, for wireless engine data transmission.
Finally, the various features described herein may essentially be freely combined with one another, and not in the sequence presented in the present application, provided they are independent of one another.