Communications: radio wave antennas – Antennas – With vehicle
Reexamination Certificate
1999-06-02
2001-04-10
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
With vehicle
C343S704000
Reexamination Certificate
active
06215450
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a glass window antenna system for motor vehicles, particularly to increase the sensitivity for an AM band in the system which may receive both AM and FM bands.
2. Description of the Prior Art
As a conventional glass window antenna system for motor vehicles which may receive both AM and FM bands, there is a glass window antenna system in which antenna patterns are provided in proximity to a defogging device (hereinafter referred to as “defogger”) so as to be capacitively coupled thereto. The defogger is consisted of heater wires and bus-bars provided on a rear window, the bus-bars applying a current to the heater wires. A choke coil is provided between the bus-bars and a DC power supply for the defogger.
This type of conventional glass window antenna system has various problems such as the decrease of S/N ratio due to an engine noise for the defogger, the decrease of a sensitivity for a FM band due to an interference between the antenna patterns and the defogger, and the difficulty for making the antenna system compact due to the big and heavy choke coil.
In order to dissolve these problems, there is provided a glass window antenna system for motor vehicles which may receive both AM and FM bands in Japanese laid-open publication No. 9-181513. There is shown in
FIG. 1
the antenna system disclosed in this publication. The antenna system comprises a glass plate of a rear window
1
, a circuit mounting component
2
, an antenna terminal/power supply terminal box
3
, a junction box for a second AM antenna
4
, a bus-bar
5
, a FM antenna
6
, a first AM antenna
7
, a second AM antenna
8
, a receiver
9
, a heater wire
10
, a flexible circuit board
11
, and a DC power supply
12
.
FIG. 2
shows a circuitry of the circuit mounting component
2
. The circuitry comprises an AM resonance inductor
13
, a damping resistor
14
, a high frequency inductor
15
to compensate the decrease of an impedance in an AM band wherein the AM resonance inductor
13
becomes capacitive, a damping resistor
16
, an AM resonance inductor
17
, a coupling capacitor
18
, a connection line
19
on the flexible circuit board
11
.
According to this glass window antenna system for motor vehicles, the first and second AM antennas
7
,
8
provided on the glass plate
1
are connected together by the line
19
on the flexible circuit board
11
. As a result, a series resonance is caused by the stray capacitance for the AM antennas
7
,
8
and the inductance of the AM resonance inductor
13
, and a parallel resonance is caused by the stray capacitance for AM antennas
7
,
8
and the inductance of the AM resonance inductor
17
. By these two kinds of resonance, i.e. the series resonance and parallel resonances, a flat sensitivity characteristic is achieved for one received frequency band. Therefore, both the AM antennas
7
,
8
and the FM antenna
6
may be used for receiving an AM broadcast while increasing the sensitivity thereto.
The conventional glass window antenna system disclosed in the Japanese laid-open publication No. 9-181513 has utilized both series and parallel resonances for receiving an AM band, so that it is difficult to set appropriately the inductance values of the resonance inductors
15
,
17
in order to establish both series and parallel resonance conditions, respectively.
SUMMARY OF THE INVENTION
The object of the present invention is to increase the sensitivity for an AM band in a glass window antenna system for motor vehicles by means of an extremely simple structure in a limited space other than the defogger on a rear window.
Another object of the present invention is to increase the sensitivity for an AM band in a very simple structure by using not only a rear window but also a side window(s).
According to the present invention, a glass window antenna system for motor vehicles comprises one AM/FM antenna pattern provided on a rear window which mainly receives a FM band while maintaining an AM receiving characteristic, and one or more AM antenna patterns provided on the rear window. The total occupied area of both the AM/FM antenna pattern and the AM antenna patterns has at least 0.2 m
2
. An AM voltage received by the AM/FM antenna pattern and an AM voltage received by the AM antenna patterns are synthesized by superimposing the AM received voltage of the AM antenna patterns to the AM received voltage of the AM/FM antenna pattern through a low-pass filter.
The receiving sensitivity may be increased by means of a very simple structure, because at least one AM/FM antenna pattern and one or more AM antenna patterns are provided to synthesize the AM voltages received by these antenna patterns. The sensitivity may be further enhanced by increasing the magnitude of synthesized voltages using a resonance circuit.
REFERENCES:
patent: 3771159 (1973-11-01), Kawaguchi et al.
patent: 5313217 (1994-05-01), Kakizawa
patent: 5719585 (1998-02-01), Tabata et al.
patent: 5793333 (1998-08-01), Taniguchi et al.
patent: 5905468 (1999-05-01), Ikawa et al.
patent: 5907308 (1999-05-01), Oka et al.
patent: 5933119 (1999-08-01), Fujii et al.
patent: 0 471 449 (1992-02-01), None
patent: 0 559 196 (1993-09-01), None
patent: 58-070643 (1983-07-01), None
patent: 9-181513 (1997-11-01), None
European Search Report, Sep. 20, 1999.
Nguyen Hoang
Nippon Sheet Glass Co. Ltd.
Ratner & Prestia
Wong Don
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