Communications: radio wave antennas – Antennas – With vehicle
Reexamination Certificate
2000-06-05
2001-06-05
Phan, Tho (Department: 2821)
Communications: radio wave antennas
Antennas
With vehicle
C343S704000
Reexamination Certificate
active
06243043
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a glass antenna device for an automobile suitable for received signals in a long wave broadcast band (LW band)(150-280 kHz), a middle wave broadcast band (530-1630 kHz), a short wave broadcast band (SW band)(2.3-26.1 MHz), an FM broadcast band (76-90 MHz, (Japan)), an FM broadcast band (88-108 MHz (U.S.A.)), a TV-VHF band (90-108 MHz and 170-222 MHz) and a TV-UHF band (470-770 MHZ), which has a high signal receiving sensitivity and a noise suppressing property and which is rich in productivity.
DISCUSSION OF THE BACKGROUND
As a glass antenna device for an automobile which is capable of improving the signal receiving 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 in a rear window glass sheet
1
of an automobile, a choke coil
9
is connected between the bus bars
15
a
,
15
b
and a d.c. power source
10
for the defogger
90
wherein the impedance of the coke coil
9
is increased in a high frequency band region to thereby allow a direct current to flow from the d.c. power source
10
to the defogger
90
, and to stop a current of high frequency band region such as a broadcast frequency band region, in which the defogger
90
is utilized as an antenna.
Further, a parallel resonance is generated by the stray capacitance to ground (hereinbelow, referred to simply as the stray capacitance) of the defogger
90
and a coil
71
in a middle wave broadcast band. Further, a received signal in the middle wave broadcast is passed by the coil
71
, a capacitor
73
and a resistor
74
. Reference numeral
11
designates a capacitor for cutting noises.
In the conventional example shown in
FIG. 7
, which employs the above-mentioned construction, an attempt has been made to improve the signal receiving sensitivity and to reduce noises.
However, in the conventional example, the stray capacitance of a cable which connects the defogger
90
to a receiver was an element to generate the parallel resonance. Further, the S/N ratio was poor because the parallel resonance frequency existed in a middle broadcast band, and the receiving sensitivity was insufficient because the resonance occurred in a single portion.
Further, when the defogger
90
was utilized as an antenna commonly used for a middle wave broadcast band and FM broadcast band and even when the shape of the defogger
90
was optimized for receiving middle wave broadcast signals, there were problems that the signal receiving sensitivity and the directivity for a FM broadcast were insufficient in a case of receiving middle wave broadcast signals.
SUMMARY OF THE INVENTION
It is an object of the present invention to eliminate the above-mentioned drawback of the conventional technique, and to provide an improved glass antenna device for an automobile which is of high signal receiving sensitivity, reducing noises and excellent productivity.
In accordance with the present invention, there is provided a glass antenna device for an automobile which comprises:
a first coil; a second coil; a first antenna conductor provided in a window glass sheet fitted to an opening of an automobile; and a second antenna conductor provided in the window glass sheet, wherein a first resonance is generated by the impedance of the first antenna conductor and the inductance of the first coil as resonance elements;
a second resonance is generated by the impedance of the second antenna conductor and the inductance of the second coil as resonance elements;
the second antenna conductor has a length and a shape for a first received signal frequency band;
the first antenna conductor has a length and a shape for a second received signal frequency band which is higher in frequency than the first received signal frequency band;
a resonance frequency which causes the first resonance and a resonance frequency which causes the second resonance are frequencies by which the sensitivity to the first received signal frequency band is increased; and
the first antenna conductor is electrically connected to the second antenna conductor.
In the above-mentioned invention, the first antenna conductor is electrically connected to the second antenna conductor by at least one selected from the group consisting of 1) a capacitive coupling of both antenna conductors due to a close position, 2) the connection of a capacitor, 3) the connection of a resistor, and 4) the connection of a coil.
Further, in accordance with the present invention, there is provided a glass antenna device for an automobile which comprises:
a first coil; a second coil; a first antenna conductor provided in a window glass sheet fitted to an opening of an automobile; and a second antenna conductor provided in the window glass sheet, wherein a first resonance is generated by the impedance of the first antenna conductor and the inductance of the first coil as resonance elements;
a second resonance is generated by the impedance of the second antenna conductor and the inductance of the second coil as resonance elements;
a received signal in a first received signal frequency band and a received signal in a second received signal frequency band which is higher in frequency than the first received signal frequency band are supplied from the first antenna conductor to a receiver;
a resonance frequency which causes the first resonance and a resonance frequency which causes the second resonance are frequencies by which the sensitivity to the first received signal frequency band is increased; and
a filter circuit for blocking or attenuating the received signal in the second frequency band is electrically connected between the first antenna conductor and the second antenna conductor.
In the above-mentioned invention, the first coil is electrically connected between the first antenna conductor and a receiver, and the second coil is electrically connected between the second antenna conductor and the automobile body as the earth.
Further, in the above-mentioned invention, the first resonance is a series resonance and the second resonance is a parallel resonance.
Further, in the above-mentioned invention, the first received signal frequency band is a middle frequency band and the second received signal frequency band is at least one selected from the group consisting of an FM broadcast band, a TV-VHF band and a TV-UHF band.
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Tabata Kohji
Terashima Fumitaka
Yamamoto Tsuyoshi
Asahi Glass Company Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Phan Tho
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