Abstract:
The invention relates to an antenna system for motor vehicles. This system allows mobile reception of television and radio broadcasts and of data of geostationary satellites independently of the operating condition of the vehicle. The system is for an antenna arrangement for the frequency range greater than 10 Ghz with quasi-omni-radiation in the horizontal direction.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an antenna system for motor vehicles, in particular for the reception of television and radio broadcasts and for the data transfer via geo-stationary satellites in the frequency range greater than 10 Ghz. 
     2. The Prior Art 
     For antennas for receiving transmissions from geo-stationary satellites, the elevation angle in central Europe lies at 30 degrees. Known and customarily employed satellite receiving antennas are the parabolic mirror antennas and, to a lesser extent, the planar antennas. Now, if one wanted to arrange somewhere on the body of a motor vehicle a parabolic mirror antenna with the geometry and size required for adequate gain, this would not be accepted according to current design ideas and for aerodynamic reasons. 
     Planar antennas are more compact; however, they are just as little suitable with their radiation lobes disposed orthogonally relative to the aperture as well. If one were to integrate a planar antenna, for example in a horizontal position in the roof of a vehicle, the direction of radiation would be wrong. If one would position it with the correct elevation, one would have the same problems as with the parabolic mirror antennas. 
     In addition, an antenna with directional characteristic arranged in or on the vehicle is also required to continually react to changes in the direction of radiation in accordance with the constant changes in direction occurring when the vehicle is in operation. 
     Antennas with directional characteristic are known from the field of radar technology where an omnidirectional radiation effect is achieved by cintinuously rotating the emitter or reflector. Such antennas combine the high, or at least adequate gain achievable with the directional effect, with an azimuth scanning of 360 degrees. The antenna, in most cases a parabolic mirror antenna, is rotated with mechanical means with a constant speed and direction. 
     However, said principle is not suitable for motor vehicles, in particular not for passenger cars because of the form in which the antenna is constructed. Furthermore, one needs to think of the relatively high rotational speeds at which the system would have to rotate for satellite reception, as well as of the expenditure connected therewith. 
     In central Europe, the reception of signals from geostationary satellites by the motor vehicle has been possible heretofore only by parking the vehicle and then extending or setting up a satellite antenna of the described type and then aligning it like a stationary antenna by hand or automatically depending on the degree of comfort offered by the equipment. This is customarily done, for example in connection with recreational motor vehicles (RV&#39;s). 
     SUMMARY OF THE INVENTION 
     The purpose of the present invention is to permit the mobile reception of television and radio broadcasts and of data of geostationary satellites independently of the operating condition of the vehicle. The invention is based on the problem of realizing for motor vehicles an antenna arrangement for the frequency range of greater than 10 Ghz with quasi-omni-radiation in the horizontal radiation diagram at an azimuth scanning of 360 degrees. The antenna arrangement is to be integrated in the structure of the vehicle in such a way that it is not visually noticeable. 
     Said problem is solved with the features specified in the main claim. The dependent claims contain preferred design variations and details. 
     By bundling a multitude of individual emitters with high packing density on a surface, the invention provides an overall compact structure. The individual emitters all have the same elevation angle, which is equal to the elevation of the overall arrangement. The required receive output is assured by a defined number of individual emitters depending on the density of the power flux, with the apertures of said emitters being added up. 
     With mechanical rotational motion of the arrangement, for example if all individual emitters are mounted with the same direction of radiation on a base plate intermittently moving about an axis, the number of emitters actually directed at the signal source can be equal to the total number of emitters. 
     With electronic rotation, groups have to be formed from the total number of emitters which, in case of reception, each supply the required gain on their own, and whose directional characteristics add up to the full circle, with a certain overlap in each case. 
     The basis of the direction-selective reception with intermittent change of the direction of radiation as defined by the invention are the diversity principle as well as the combined urilization of a gyromagnetic sensor and the global positioning system (GPS), by which means it is possible to detect and compensate changes in the direction of travel of the vehicle and thus the azimuth angle for the antennas with respect to a selected satellite. With the gyromagnetic sensor and with the support of the GPS-unit, a control signal for a change of the receive parameters is generated when the driving direction is changed. The diversity circuit, when the actual receive quality is reduced, additionally scans the environment of the direction of radiation and the group of emitters switched to reception, and, when the reception is falling short of a threshold value, reverses to a more favorable group of emitters. This applies to the variation of electronic rotation. With mechanical rotation, a control signal is generated for the motor of the base plate, and the system swings into the new receive direction by mechanical rotation. 
     The advantages of the invention are obvious: Most of all, a possibility was found for assuring a stable reception of transmissions from geostationary satellites in the moving vehicle also under conditions of low geographic elevation, for example in central Europe. The spatial dimensions of the antenna arrangement as defined by the invention are still within acceptable limits even under unfavorable conditions, i.e. low gain of the individual emitter along the edge of the supplied region and thus a high number of required emitters, and can be realized also on the average types of passenger motor vehicles. This applies even under the precondition that the system has to assure at least 30 dBi antenna gain. 
     A further advantage consists in that the total or overall arrangement can be divided into sectors or segments with emitter groups which are integrated in different structural parts of the body and connected via a central management. This provides for high variability of association and integration of the antenna units. 
     The principle as defined by the invention is shown in the present claims and exemplified embodiments in variations and details, by which the function and the advantages have already been tested and demonstrated. However, this does not mean that the idea of the invention does not also comprise further designs and variations. Conceivable is mainly also the integration in vertical elements of the body such as the side parts or, for example in a bus, the vertical arrangement behind the large-sized windowpanes inclusing the front and the rear windowpanes, where antenna systems such as the flat planar antennas switched or connected together as defined by the invention are conceivable as well. Planar antennas, which are rectangular in most cases, failed to gain successful acceptance for home use; however, they may be found to be advantageous for certain motor vehicles because of their simple construction and possible low mass. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings. It is to be understood, however, that the drawing is designed as an illustration only and not as a definition of the limit of the invention. 
     FIG. 1 shows an antenna system consisting of horn emitters on a circulr base plate, for electronic rotation. 
     FIG. 2 shows a horn emitter on a circular base plate, for mechanical rotation. 
     FIG. 3 shows design details of an arrangement with strip conductor antennas (patch antennas), for electronic rotation. 
     FIG. 4 is a horn emitter for 11.7 GHz; and 
     FIG. 5 shows a group of patch antennas for 11.7 GHz. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the schematic representation in FIGS. 1 and 2, it is assumed that the antenna systemis completely integrated as a compact structural unit in a substantially horizontal surface of the vehicle body such as, for example the roof. In FIGS. 1 and 2, the horn emitters  2  (of the pyramid horn type) are arranged on the circular base plate  1 , and path antennas  3  in the example according to FIG.  3 . The patch antennas are combined in groups each comprising four antennas. 
     With the horn-type emitters, the elevation angle of about 30 degrees is obtained by setting the funnel-like zones accordingly. With the patch antennas, the flat segments are grouped on the carriers  4 , which are peripherally supported on plate  1  on the annular corrugations  5  with the cross section of a prism. 
     In the arrangement according to FIG. 1, the full circle is divided into reception-effective sectors with the help of the feed line network, with the lobes of said sectors overlapping each other in each case in the 3-dB range. The emitter sectors can be separated in terms of connection technology also in such a way that when the azimuth angle changes, the groups are displaced sideways by an angle smaller than the sector angle. The hollow conductors of the emitters are arranged “standing” in FIG. 1, and “lying” on base plate  1  in FIG.  2 . 
     With the antenna system according to FIG. 2, the base plate with the emitters is mechanically driven by the drive  5 . The drive has to be light, low in inertia and reliable, and the location in which it will be arranged on the body of the vehicle or on base plate  1  will depend on the premises of the individual case. 
     What has been stated above with respect to the groups and the feed line network for the exemplified embodiment according to FIG. 1 applies as well to the system with patch antennas, of which FIG. 3 shows a sector and details of the structural elements. 
     It is clearly shown at the same time in FIG. 3 that with electronic scanning of the azimuth, it is possible to form emitter groups which, in terms of space, are not concentrated to form a full circle. The base plate is divided into sectors with either one or several reception-effective groups in each sector, and the sectors are positioned on different elements of the body. The precondition is mainly that the fictitious omni-radiation effect is obtained again overall; that the feed line network is managable; and that no serious differences occur with respect to the running time. Said problems are solved by connecting each area sector to its own converter. Connecting the converters together at the level of the intermediate frequency can be managed in a simple way with connection technology known per se. 
     FIGS. 4 and 5 show examples for the dimensional relations of the individual emitters or an elementary group. With emitters of this structure, shown here in a simplified representation, wide-band reception is possible in one polarization in each case. The practical design itself and the selection of the materials and dimensional corrections resulting therefrom, and the physical optimization of the emitters and the system are then still decisively influenced by the space conditions, the reception spectrum and also by technological factors, which are problems which have to be solved with the means of the prior art known per se and available to the developer within the meaning of optimization of the system. 
     In FIG. 4, reference numerals 2.1 denote the hollow conductor conforming to 11.7 GHz; 2.2 the funnel-like widening; and 2.3 the decoupling element with tying to the feed line network. 
     The diameter of a base plate  1  with patch antennas having the structure described herein, and for electronic rotation comes to approximately 600 millimeters. 
     Accordingly, while only one embodiment of the present invention has been shown and described, it is obvious that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention.