Communications: electrical – Traffic control indicator – Combined
Reexamination Certificate
2000-06-26
2003-12-02
Lobo, Ian J. (Department: 3662)
Communications: electrical
Traffic control indicator
Combined
C340S933000, C340S935000
Reexamination Certificate
active
06657554
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a road antenna for use with an electric toll collection (ETC) system, which system can automatically collect a toll through radio communication without involvement of temporary stopping of a traveling vehicle which is passing through a tollgate of a turnpike.
The present invention also relates to a transmitter, a receiver, a radio system, and a method of setting a communications area, all of which are applied to narrow-band communication, such as that realized by a turnpike electric toll collection system (hereinafter referred to simply as an “ETC system”), and which controls an output of radio transmission established between a cell station and a mobile station.
Further, the present invention relates to a travel-speed support system which determines whether or not a vehicle is traveling in excess of a speed limit for vehicles set on a turnpike or an ordinary road and sends a notice to the driver of the vehicle when the vehicle is traveling in excess of the speed limit, as well as to an antenna for use with the system.
A traveling vehicle has conventionally been required to temporarily stop at a tollgate of a turnpike and receive a highway ticket from or pay a toll to an official, thus greatly contributing to a traffic jam. Against such a backdrop, attempts have been made to put an electronic toll collection system (ETC) into actual use as a nonstop tollgate system which eliminates a necessity for temporarily stopping a vehicle.
FIG. 27
shows an example ETC system scheduled to be put into practical use. In this drawing, a vehicle
1
is equipped with an on-vehicle radio device
2
. A road antenna
4
is mounted on a post
3
and at a position above a road R. Radio communication is established between the on-vehicle radio device
2
and the road antenna
4
. A vehicle sensor
5
is disposed on either side of the road R for optically detecting passage of the vehicle
1
.
The antenna
4
establishes radio communication with on-vehicle radio device
2
mounted in a vehicle
1
which is passing through the post
3
, to thereby specify the owner of the vehicle
1
through use of the radio device
2
. For example, ID information to be used for specifying the owner of the vehicle
1
is written in the on-vehicle radio device
2
.
A toll and information for specifying the owner of the vehicle
1
are written into a storage area of the antenna
4
every time the vehicle
1
passes through the post
3
. The toll and the vehicle owner ID information, which have been acquired while the vehicle
1
passes through the post
3
, are transmitted to an unillustrated center by way of the antenna
4
. The unillustrated center summarizes tolls and on a monthly basis collects the tolls from the owner of the vehicle
1
that has passed through the post
3
.
In this system, after a vehicle detector
5
disposed on the road of a turnpike has detected passage of the vehicle
1
, radio communication pertaining to a toll is established between the antenna
4
and the on-vehicle radio device
2
. Accordingly, collection of tolls is performed smoothly without involvement of temporary stopping of a traveling vehicle.
In terms of design of the ETC system, there is specified a coverage area of radio communication established between the on-vehicle radio device
2
and the road antenna
4
.
FIG. 28
is a plan view showing an example coverage area. A hatched communications area F
1
is a range within which radio communication can be established between the on-vehicle radio device
2
and the road antenna
4
. The remaining area; i.e., a non-response area F
2
, is a range in which radio communication is not permitted.
An electric field level of the road antenna
4
chiefly determines whether or not radio communication is feasible. In a case where the electric field of the road antenna
4
is greater than a predetermined level, the on-vehicle radio device
2
can perform a receiving operation, thus enabling radio communication. In contrast, in a case where the electric field of the road antenna
4
is less than a predetermined non-response level, the on-vehicle radio device
2
cannot perform a receiving operation. Accordingly, the area where the on-vehicle radio device
2
cannot establish radio communication is taken as a non-response area.
In the previously-described case, the road antenna
4
has a sharp directional pattern, and an angle at which the road antenna
4
is mounted on the post
3
greatly affects the distribution of electric field.
FIG. 29
shows an example road antenna
4
mounted on the post
3
.
FIG. 30
shows an example distribution of receiving electric field at a position
1
meter elevated from the road R and with respect to the direction in which the vehicle travels.
As shown in
FIG. 30
, an electric field level L
1
designates a communicable threshold level, and an electric field level L
2
designates a non-response threshold level. From
FIG. 30
, it is understood that the communications area F
1
and the non-response area F
2
, which are shown in
FIG. 28
, are embodied by reference to these threshold levels.
FIG. 31
shows an example distribution of an electric field produced in a case where only an angle &thgr; at which the road antenna
4
is mounted and is shown in
FIG. 29
is changed. In this case, the predetermined communications area F
1
shown in
FIG. 28
is not ensured, and receiving power—which is greater than the communicable threshold value level L
1
and at which the on-vehicle radio device
2
can perform a receiving operation—exists in the non-response area F
2
. There is a possibility of the ETC system yielding a failure.
For example, as shown in
FIG. 32
, in a case where a vehicle
1
A having no on-vehicle radio device and a vehicle
1
B having an on-vehicle radio device passe through the ETC system while the vehicle
1
B is following close behind the vehicle
1
A, the vehicle sensors
5
detect the vehicle
1
A. However, radio communication is established between the road antenna
4
and the on-vehicle radio device
2
of the vehicle
1
B. As a result, the ETC system yields a failure, thereby permitting passage of the vehicle
1
A without charge.
In order to prevent a failure, means for ascertaining in advance an angle &thgr; at which the road antenna
4
is mounted (hereinafter referred to simply as a “mount angle”) becomes necessary. At the time of installation of the road antenna
4
, the post
3
standing at a height of 5 m or more is fixed through use of a bucket vehicle or a like vehicle. After installation of the road antenna
4
, the mount angle &thgr; of the road antenna
4
cannot be readily ascertained. However, it is thought that after installation the mount angle &thgr; of the road antenna
4
may be changed by a blow or an earthquake.
FIG. 33
is a plan view showing an example coverage area. As shown in
FIG. 33
, in terms of design of the ETC system, there is specified a coverage area of radio communication established between the on-vehicle radio device
2
and the road antenna
4
. A communications area F
1
is a range within which radio communication can be established between the on-vehicle radio device
2
and the road antenna
4
. The remaining area is a range in which radio communication is not permitted.
In the previous ETC system, the communications area F
1
must be covered by means of the directivity of the road antenna
4
. However, the transmission power of the road antenna
4
is changed for reasons of environmental or secular changes, the range of the communications area F
1
is also changed, thereby resulting in a system failure. Further, depending on variation in the angle at which the road antenna
4
is mounted, the communications area F
1
is greatly changed, thereby interfering with radio communication established by a vehicle which is traveling on an adjacent lane.
FIG. 34
shows a commonly-employed transmission circuit
50
. In
FIG. 34
, reference numeral
51
designates a radio section;
52
designates a level control attenuator; and
53
designates an antenna
Hirano Yoshiteru
Inui Akihiro
Takemoto Makoto
Terashima Masaki
Lobo Ian J.
Matsushita Electric - Industrial Co., Ltd.
Pearne & Gordon LLP
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