Communications: directive radio wave systems and devices (e.g. – Return signal controls external device – Radar mounted on and controls land vehicle
Reexamination Certificate
2002-05-09
2004-01-06
Gregory, Bernarr E. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Return signal controls external device
Radar mounted on and controls land vehicle
C343S704000, C343S872000, C343S873000
Reexamination Certificate
active
06674392
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a motor-vehicle radar system.
BACKGROUND INFORMATION
Motor-vehicle radar systems are used within the framework of an automatic cruise control system of a vehicle for detecting vehicles driving ahead. A system of this type is also known as Adaptive Cruise Control (ACC). To influence the electromagnetic waves used and occasionally to protect the radar system from weather influences, as well, usually a member is situated in the beam path of the electromagnetic waves. This member is often a component of a housing which surrounds such a motor-vehicle radar system.
The German Published Patent Application No. 197 24 320 describes a method for producing a heatable antenna lens. A heatable antenna lens is described made of a dielectric member which possesses an arrangement of electrical conductor tracks therein. The arrangement of electrically conductive tracks is situated as near as possible to the outer surface of the lens to be heated, a reduction of heating power thereby resulting by introducing the energy close underneath the surface to be heated. Also resulting from this is an accelerated heat-up characteristic. It is furthermore described that easy adaptability of the heating power can be achieved by using wires having a desired resistance characteristic. For example, it can be a resistance wire.
The German Published Patent Application No. 196 26 344 describes a lens for focusing millimetric waves, particularly for distance sensors for motor vehicles, which are made at least partially of a ceramic material or a plastic, e.g. polypropylene or polycarbonate, filled with ceramic material. For example, aluminum oxide with magnesium-oxide and potassium-oxide constituents is provided as ceramic material. Lenses made purely of a ceramic material can be produced according to German Published Patent Application No. 196 26 344 by pressing, tempering or sintering, and lenses made of plastics filled with ceramic material can be produced in the injection-molding process. One specific embodiment of German Published Patent Application No. 196 26 344 provides for applying a protective coating on the surface of the lens which protects the outwardly-directed lens surface at least from weather influences. Hexamethyl disiloxane is applicable for the protective coating in particular for plastic lenses filled with ceramic material. A further form of German Published Patent Application No. 196 26 344 provides for a convex-plane lens, the convex or the plane surface being alternatively subject to the weather influences in the installed state. To reduce reflection losses, German Published Patent Application No. 196 26 344 allows for providing at least one surface of the lens with grooves which can be filled with a dielectric material in order to lend a plane surface to the lens. The dielectric material can have an inhomogeneous distribution of the dielectric constant in the direction of the optical axis of the lens and/or transverse thereto.
The German Patent No. 197 41 081 describes a method for producing an antenna lens. The method provides that a rigid shell, predetermining the shape of the lens and forming the anti-reflection layer, is produced, and that the cavity of the shell is filled in with a liquefied, powdery or pasty material forming the lens core. The shell can be made of a plastic (for example, plexiglass, polycarbonate or similar materials), while, for example, plastics and mixtures of plastic with ceramic materials (e.g. polyethylene, polypropylene, Al
2
O
3
, TiO
2
or CaZO
x
) are provided as material for the lens core. According to German Patent No. 197 41 081, the surface of the shell can be designed both to be smooth, and can have any structure at all, for example, a Fresnel structure. So that the shell forms an ideal anti-reflection layer for the lens, German Patent No. 197 41 081 C1 proposes that the shell be manufactured from a plastic whose dielectric constant corresponds to the square root of the dielectric constant of the actual lens material (the filling). Furthermore, it can be inferred from German Patent No. 197 41 081 that, by very high dielectric constants (&egr;>9) of the dielectric lens material, compact designs can be implemented having short focal lengths.
From the German Patent No. 196 44 164, a motor-vehicle radar system is known having at least one send/receive element for sending and/or receiving electromagnetic waves, a lens-shaped dielectric member being arranged in the beam path of the at least one send/receive element to focus or scatter the electromagnetic waves. The lens-shaped dielectric member, which additionally protects the send/receive element from weather influences, has an arrangement of electrically conductive tracks whose breadth is tenth wave at the most, and whose distances from one another are at least a quarter wave, Lambda designating the free-space wavelength of the electromagnetic waves. The electrically conductive tracks are arranged predominately in a direction perpendicular to the polarization direction of the electromagnetic waves. Depending on the desired use, the arrangement of electrically conductive tracks can be disposed on the inner side of the dielectric member, i.e. the side facing the send/receive elements, the outer side, or even within the dielectric member. If a heating current flows through the electrically conductive arrangement, the dielectric member can thereby be freed from coatings such as ice, snow or slush. In the same way, the dielectric member can be dried or kept dry with the aid of a heating current. It is also disclosed that the electrically conductive arrangement may be subdivided into at least two portions separate from each other. When working with this configuration, if the arrangement of electrically conductive tracks is on the outer side of the dielectric member, it is possible to infer a so-called loss angle tan &dgr; of the coating material on the basis of the measurement of the capacitance between the two separate portions of the arrangement. In other words, a soiling of the dielectric member can be determined. In dependence on this determined soiling, i.e. a determined dirt coating, a heating current can be switched on which flows through the electrically conductive arrangement. On the other hand, due to the division into at least two regions, the heating power can be varied, for example, to quickly heat up an ice-covered lens using a high heating power, and subsequently keeping the lens free using a reduced heating power. It is further known from German Patent No. 196 44 164 that when working with a lens member made of ceramic, the electrical conductor tracks are applied using known thick-film technology, while for members made of plastic, likewise known, cost-effective methods can be used for imprinting the electrical conductor tracks. It can be inferred from one exemplary embodiment in German Patent No. 196 44 164 that a lens can be provided, composed of two partial lenses, which is made of two plane-convex partial lenses of different materials. In this case, the electrical conductor tracks can be arranged in one plane between the plane surfaces of the two partial lenses.
German Published Patent Application No. 197 24 320, German Published Patent Application No. 196 26 344, German Patent No. 197 41 081 and German Patent No. 196 44 164 describe various forms of antenna lenses which can be used in a motor-vehicle radar system. German Published Patent Application No. 197 24 320 and German Patent No. 196 44 164 each include an arrangement of electrical conductor tracks which can be used, inter alia, to free the side of the antenna lens exposed to the influences of weather from coatings such as snow, ice or slush. Both patents describe the possibility of regulating the heating power, either in that the heating power can be adapted by wires having a desired resistance characteristic, or in that the electrically conductive arrangement is subdivided into at least two portions separate from one another.
SUMMARY OF THE INVENTION
Given a motor-vehicle r
Lucas Bernhard
Schmidt Ewald
Schneemann Joerg
Voigtlaender Klaus
Gregory Bernarr E.
Kenyon & Kenyon
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