Communications: radio wave antennas – Antennas – With vehicle
Reexamination Certificate
1999-09-03
2001-03-13
Le, Hoanganh (Department: 2821)
Communications: radio wave antennas
Antennas
With vehicle
C343S704000, C343S860000
Reexamination Certificate
active
06201505
ABSTRACT:
The present invention relates to a glass antenna device for an automobile suitable for receiving signals in, for example, a long wave broadcast band (150-280 kHz), a middle wave broadcast band (520-1700 kHz), a short wave broadcast band (3-30 MHz), an FM broadcast band of Japan (76-90 MHz), an FM broadcast band of U.S.A. (88-108 MHz), a TV-VHF band (90-108 MHz, 170-222 MHz), a TV-UHF band (470-770 MHz) and so on, which is of high sensitivity and low noise and which is rich in productivity.
As a glass antenna device for an automobile which is capable of improving the sensitivity by utilizing resonance, there has been proposed a glass antenna device for an automobile as shown in
FIG. 7
(JP-Y-4-53070).
In this conventional example, a defogger
90
comprising heater strips
2
and bus bars
15
a
,
15
b
,
15
c
is provided on a rear window glass sheet
1
fitted to a rear window opening of an automobile. There are the bus bar
15
a
at a lower portion and the bus bar
15
b
at an upper portion on a left side of the defogger
90
. The lower bus bar
15
a
is connected to the automobile body as the earth and the upper bus bar
15
b
is connected to an anode of a d.c. power source
10
. A fed current flows from the upper bus bar
15
b
through the bus bar
15
c
at a right portion to the lower bus bar
15
a
in a channel-like form. The defogger shown in
FIG. 7
is in a so-called channel-like form.
In the glass antenna device shown in
FIG. 7
, a choke coil
9
is connected between the bus bars
15
a
,
15
b
and the d.c. power source
10
for the defogger
90
, and by increasing the impedance of the choke coil
9
in a high frequency band region, a direct current is allowed to pass from the d.c. power source
10
to the defogger
90
but a current in the high frequency band region such as a broadcast band region or the like is blocked whereby the defogger
90
is utilized as an antenna.
Further, a parallel resonance is generated by the stray capacitance to ground (hereinbelow, referred simply as the stray capacitance) of the defogger
90
and a coil
71
in a middle wave broadcast band, and a received signal in the middle wave broadcast band is passed in association with coil
72
, a capacitor
73
and a resistor
74
. Reference numeral
11
designates a capacitor for cutting noises. In the conventional example having such construction as in
FIG. 7
, an attempt has been made to improve the sensitivity and to reduce noises.
In the conventional example, however, the stray capacitance of a cable connecting the defogger
90
to a receiver constituted a main factor to cause the parallel resonance. Further, the S/N ratio was poor and the sensitivity was insufficient because there was a parallel resonance frequency in the middle broadcast band.
Further, when the defogger
90
was used as an antenna commonly used for the middle wave broadcast band and the FM broadcast band and if the shape of the defogger
90
was optimized for receiving middle wave broadcast signals, there were problems that the sensitivity and directivity for FM broadcasting were insufficient in a case of receiving FM broadcast signals.
It is an object of the present invention to eliminate the above-mentioned drawbacks of the conventional technique, and to provide a glass antenna device for an automobile which is of high sensitivity; reduces noises and is good in productivity.
In accordance with a first aspect of the present invention, there is provided a glass antenna device for an automobile wherein an electric heating type defogger having heater strips and bus bars for feeding a current to the heater strips, and an antenna conductor are provided on a rear window glass sheet fitted to a rear window opening of an automobile, and a choke coil is connected to at least one between a bus bar and a d.c. power source and between the bus bar and the automobile body as the earth so that a signal in a first frequency band and a signal in a second frequency band which is higher in frequency than the first frequency band are received, the glass antenna device being characterized in that the defogger functions as an antenna so that it receives a signal in at least the first frequency band and sends the signal to a receiver, and the antenna conductor receives a signal in at least the second frequency band and sends the signal to the receiver; a first inductance element and a second inductance element are provided; a first resonance is generated by a resonance element which comprises the impedance of the defogger and the inductance of the first inductance element; a second resonance is generated by a resonance element which comprises the impedance of the defogger and the inductance of the second inductance element; the resonance frequency of the first resonance and the resonance frequency of the second resonance are determined so that the sensitivity of signal in the first frequency band is increased, and a filter circuit for blocking or attenuating a signal in the second frequency band is electrically connected between the antenna conductor and the defogger.
In accordance with a second aspect of the present invention, there is provided a glass antenna device for an automobile wherein an electric heating type defogger having heater strips and bus bars for feeding a current to the heater strips, and an antenna conductor are provided on a rear window glass sheet fitted to a rear window opening of an automobile; a choke coil is connected to at least one between a bus bar and a d.c. power source and between the bus bar and the automobile body as the earth, and the antenna conductor and a receiver are connected with a cable so that a signal in a first frequency band and a signal in a second frequency band which is higher in frequency than the first frequency band are received, the glass antenna device being characterized in that the defogger functions as an antenna so that it receives a signal in at least the first frequency band and sends the signal to the receiver, and the antenna conductor receives a signal in at least the second frequency band and sends the signal to the receiver; a first inductance element and a second inductance element are provided; a first resonance is generated by a resonance element which comprises the impedance of the defogger and the inductance of the first inductance element; a second resonance is generated by a resonance element which comprises the impedance of the cable and the inductance of the second inductance element; the resonance frequency of the first resonance and the resonance frequency of the second resonance are determined so that the sensitivity of signal in the first frequency band is increased, and a filter circuit for blocking or attenuating a signal in the second frequency band is electrically connected between the antenna conductor and the defogger.
Further, in accordance with a third aspect of the present invention, there is provided a glass antenna device for an automobile wherein an electric heating type defogger having heater strips and bus bars for feeding a current to the heater strips, and an antenna conductor are provided on a rear window glass sheet fitted to a rear window opening of an automobile, and a choke coil is connected to at least one between a bus bar and a d.c. power source and between the bus bar and the automobile body as the earth so that a signal in a first frequency band and a signal in a second frequency band which is higher in frequency than the first frequency band are received, the glass antenna device being characterized in that the defogger functions as an antenna so that it receives a signal in at least the first frequency band and sends the signal to a receiver, and the antenna conductor receives a signal in at least the second frequency band and sends the signal to the receiver; a filter circuit for blocking or attenuating a signal in the second frequency band and the first inductance element are electrically connected between a line connecting the defogger to the receiver and the defogger by interposing at least one of a line and a circuit element, and
Ikutame Nobuyasu
Terashima Fumitaka
Asahi Glass Company Ltd.
Le Hoang-anh
Nguyen Hoang
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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