Communications: radio wave antennas – Antennas – With coupling network or impedance in the leadin
Reexamination Certificate
2002-01-17
2003-09-23
Nguyen, Hoang (Department: 2821)
Communications: radio wave antennas
Antennas
With coupling network or impedance in the leadin
C343S713000
Reexamination Certificate
active
06624794
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an antenna device. More particularly, the present invention relates to an antenna device having at least one vertical radiator.
2. Description of the Related Technology
Antennas which are intended for sending and receiving high frequency signals, especially in mobile radio telephone ranges (0.8-1.9 GHz), are known from practice in various versions as rod antennas or integrated antennas. Rod radiators in a straight or kinked version for mobile radio telephone service are used especially as &lgr;/4-long or short thick monopoles (“stub antennas”) which are made alternatively for installation in a hole on a body part, for example the motor vehicle roof, for cementing to the vehicles windows as so-called “on-glass” antennas, or as integrated antennas (for example as described in German patent application 198 41 187.1.
Quarter wave monopoles with respect to their radiation power are optimum at the lower frequencies of the mobile radio telephone ranges, but due to their vertical length of up to roughly 8 cm are not suited for installation in flat spaces, for example, between a motor vehicle roof and its inner lining, the so-called head liner.
Shortened monopole antennas with a length of roughly &lgr;/10 or less, which are possible mechanically for flat space installation sites, however, do not have the desired or the required radiation power. This also applies to bent monopoles with a total length which can be &lgr;/4, but with a vertically polarized portion of the radiation power which is too small for many applications due to the length of the vertical radiator part.
SUMMARY OF THE INVENTION
An object of the invention is therefore to devise an antenna of the initially mentioned type in which the vertical radiators have a radiation power comparable to a &lgr;/4 monopole, but with a length in the vertical direction which is as small as possible and thus is suitable for installation at installation sites with a low height.
This and other objects may be achieved by providing an antenna with at least one vertical radiator, wherein one end of said at least one vertical radiator is connected to a ground and the other end is connected, via an impedance transformation means (which has an electrical length of about one-fourth of the average operating wavelength or an odd multiple thereof) to a vertical conductor which is supplied against said ground.
As a result of the arrangement of at least one vertical radiator at an electrical distance of &lgr;/4 from the supplied vertical conductor of the antenna in conjunction with matching by impedance transformation means, a large current flows through each vertical radiator at a current filling capacity which is roughly constant over its entire length and thus causes a high radiation power in the vertical polarization direction. Moreover, the supplied vertical conductor between the terminal site of the feed source and the impedance transformation means delivers a vertically polarized radiation portion so that the antenna overall at a length of at least one vertical radiator of less than &lgr;/10 at the lowest mobile radio telephone frequency has a radiation power comparable to the &lgr;/4 monopole. This minimized construction of the antenna in the vertical direction of a maximum height of roughly 2.2 cm enables its installation in shallow cavities or flat spaces, for example between the roof and the inside lining of motor vehicles.
The impedance transformation means in an electrical circuit can consist of discrete circuit elements or can be made as a high frequency line with the corresponding wave impedance which is especially feasible when it is to operate permanently without interference regardless of climatic conditions and vibration movements, as in motor vehicles.
The vertical radiator or radiators can consist of wire, but with respect to mechanical stability and low ohmic losses, it is more favorable to make it or them either as thick, for example cylindrical metal parts, or to produce them from sheet metal strips.
Advantageous embodiments and developments of the antenna as claimed in the invention are given in the dependent claims.
According to one aspect of the invention, the antenna may comprise two vertical radiators disposed equidistant from the supplied vertical conductor.
Thus, the arrangement is indeed longer and more complex, but has better matching to a 50 ohm feed source and a symmetrical radiation pattern which is desired or even necessary in many cases.
According to another aspect of the invention, the unit consisting of the vertical radiators, the supplied vertical conductor, and the impedance transformation means is made as an integral punched beat part from metal.
This construction results in an especially simple and economically producible antenna structure which moreover is mechanically stable and has low ohmic losses, wherein its vertical radiator can be easily connected to ground for example by soldering or spot welding. In addition, it is possible without added costs to make the individual sheet metal parts in a certain shape.
According to another aspect of the invention, the antenna may include a metallic reflector, whereby a directional effect which is desired in many applications can be produced and can be adapted within limits to the requirements of the individual case by the arrangement and shape of the reflector.
In accordance with one feature of the invention, the reflector is located between the vehicle interior and the unit consisting of the vertical radiator, impedance transformation means and supplied vertical conductor, whereby the radiation which can penetrate into the motor vehicle interior is greatly reduced. As will be appreciated by one of ordinary skill in the art; this at least in the case of transmission represents an important protection for the passengers and moreover protects against equipment interference.
According to another feature of the invention, one especially simple structure is realized by having the reflector serve as the ground surface.
Since motor vehicle antennas are always located in the vicinity of the body, it may be advantageous to use it as a grounding surface wherein the reflector is electrically connected to the metallic motor vehicle body. According to the invention, it can be connected either conductively or capacitively to the reflector. The latter alternative may be preferable since the enameling of the body which took place before antenna installation need not be removed at the terminal site for conductive contact-making.
The arrangement of the antenna between the covered openings of motor vehicles transparent to electromagnetic radiation may be preferable because it doesn't interfere with its operation but protects the antenna from environmental effects, manipulations and damage. Due to the cover, the antenna is not visible from the outside and thus gives no unwanted indication that the motor vehicle is equipped with a mobile phone. Preferred installation sites include the metallic edge areas of motor vehicle windows, plastic roofs of motor vehicles, or other plastic areas (for example sliding roofs) of metallic motor vehicle roofs.
For screening of motor vehicle windows, for example, conventionally black printing of the affected area is not only especially simple and economical, but moreover protects against glare.
According to the invention, advantageous positioning of the antenna between the motor vehicle opening and interior lining molded parts, wherein the reflector is shaped to match the interior lining molded part, projection into the vehicle interior may be avoided with minimum cost. In addition, arrangement between the body and inside lining ensures adequate holding of the antenna even without special fasteners.
According to one aspect of the invention, one especially suitable installation site for motor vehicle mobile radio telephone antennas is in the vicinity of the roof edge of the front or rear window. According to this aspect, a partial area of the reflector advantageously ad
Kuhn Martin
Pfletschinger Markus
Riedhofer Peter
Wendt Dirk
Fulbright & Jaworski LLP
Hirschmann Electronics GmbH & Co. KG
Nguyen Hoang
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