Communications: radio wave antennas – Antennas – With ice clearer or preventer
Reexamination Certificate
2000-02-11
2001-03-27
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
With ice clearer or preventer
C343S713000
Reexamination Certificate
active
06208303
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-040133, filed Feb. 18, 1999, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a window glass antenna for vehicles which is mounted on a window glass of a vehicle such as an automobile.
A conventional vehicle window glass antenna is assembled by attaching an antenna element having a given pattern and constituted of narrow thin-film conductors on a rear window of an automobile.
Usually a defogger is attached to the rear window in order to defog a glass of the window. The defogger includes a plurality of horizontal wires constituted of narrow thin-film conductors which are arranged in parallel and at almost regular intervals on the rear window. First ends of the horizontal wires are connected together by one of paired bus bars, while second ends thereof are connected together by the other bus bar.
If a direct-current power supply voltage is applied to the bus bars from a car-mounted battery (12V), the horizontal wires generate heat to prevent the fogging of the window glass due to condensation.
The vehicle window glass antenna is provided between the uppermost portion of the defogger and the window frame. The narrow thin-film conductors are formed on the window glass in a given pattern such that the antenna can receive radio waves of a predetermined frequency, and used as antenna elements. A feeding point of the antenna elements is connected to a tuner of a receiver set through a feeder formed of a coaxial cable.
In most cases, a desired antenna characteristic cannot be obtained from the above conventional vehicle window glass antenna, since the surroundings of the antenna are varied with vehicle types and other conditions, even though the antenna itself is accurately assembled based on a fixed standard. The window glass is usually surrounded with a metallic car body; therefore, it is difficult to design the antenna only by the antenna theory. For this reason, the actual state is that the antenna characteristic such as an impedance is adjusted using a cut-and-try method. More specifically, when the antenna is mounted on the window glass, a characteristic measuring instrument, such as an impedance meter, is connected to an end portion of the feeder in place of the tuner, and the antenna characteristic is controlled by correcting the pattern, length or the like of the antenna using the cut-and-try method.
A technique of utilizing the defogger as an antenna element is also proposed. In this technique, too, the antenna characteristic has to be adjusted using the cut-and-try method in order to acquire a desired antenna characteristic.
As described above, in the conventional vehicle window glass antenna, the antenna characteristic had to be adjusted using the cut-and-try method according to the types of vehicles on which the antenna was to be mounted, in order to obtain a desired antenna characteristic. Furthermore, the conventional antenna had the problem that it was very difficult and took a long period of time to adjust a frequency band of use by the above cut-and-try method.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a window glass antenna apparatus for vehicles which is capable of quickly and accurately adjusting the setting of a desired characteristic.
According to one aspect of the present invention, there is provided a window glass antenna apparatus for vehicles, comprising a defogger attached to a window glass of a vehicle, for defogging the window glass, the defogger including a plurality of horizontal wires constituted of a plurality of thin, narrow conductors and arranged parallelly and horizontally at regular intervals, and a pair of bus bars for connecting both ends of the plurality of horizontal wires together, a power supply unit which supplies power to the defogger to heat the defogger, a separating coil which separates the power supply unit and the defogger from each other at high frequencies, a vertical center wire constituted of a thin, narrow conductor and crossing the horizontal wires in a middle portion of the defogger and in a horizontal direction thereof, a pair of short stub conductors constituted of thin, narrow conductors and provided at right and left positions a ¼ wavelength of a wave applicable to transmission/reception away from the vertical center wire so as to cross the horizontal wires of the defogger, and a pair of grounding capacitors which ground the pair of short stub conductors at high frequencies.
According to another aspect of the present invention, there is provided a window glass antenna apparatus for vehicles, comprising a defogger, attached to a window glass of a vehicle, which defogs the window glass, the defogger including a plurality of horizontal wires constituted of a plurality of thin, narrow conductors and arranged parallelly and horizontally at regular intervals, and bus bars for connecting both ends of the plurality of horizontal wires together, a power supply unit which supplies power to the defogger to heat the defogger, a separating coil for separating the power supply unit and the defogger from each other at high frequencies, and a vertical center wire constituted of a thin, narrow conductor and crossing the horizontal wires in a middle portion of the defogger and in a horizontal direction thereof, wherein the bus bars cross the horizontal wires of the defogger at right and left positions a ¼ wavelength of a wave applicable to transmission/reception away from the vertical center wire to serve as short stub conductors, and a pair of grounding capacitors is provided to ground the bus bars serving as the short stub conductors, at high frequencies.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
REFERENCES:
patent: 5029308 (1991-07-01), Lindenmeier et al.
patent: 5581263 (1996-12-01), Maeda et al.
patent: 5581264 (1996-12-01), Tabata et al.
patent: 5801663 (1998-09-01), Lindenmeier et al.
Ahrabian Mahmood
Tachihara Hiroyuki
Harada Industry Co. Ltd.
Pennie & Edmonds LLP
Wimer Michael C.
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