Communications: electrical – Vehicle detectors
Reexamination Certificate
2000-08-09
2001-10-09
Hofsass, Jeffery (Department: 2632)
Communications: electrical
Vehicle detectors
C340S928000, C340S942000, C455S099000, C701S032000, C701S117000, C705S013000
Reexamination Certificate
active
06300882
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to an electronic toll collection system (hereinafter referred to as the ETC system in short) for an intelligent transport system (hereinafter also referred to as the ITS in short). More particularly, the present invention is concerned with a dedicated short-range communication apparatus (hereinafter also referred to as the DSRC apparatus) which is mounted on an automobile, a motor vehicle, a car or the like and which is designed to serve for disposing of payment of fee or charge or toll through cooperation with the ETC system. Hereinafter, the dedicated short-range communication apparatus will also be referred to as the DSRC apparatus or vehicle-onboard DSRC apparatus. Thus, in more concrete, the present invention concerns an improvement of the vehicle-onboard DSRC apparatus such that the receiving sensitivity thereof can be variably or adjustably set in dependence on the type or specie of the motor vehicle on which the DSRC apparatus is mounted for the purpose of suppressing or preventing error(s) which may otherwise occur in the radio communication with on-road transport managing equipment such as exemplified by the ETC system mentioned above which is installed stationarily on the ground in association with a road such as a toll road and which is usually incorporated in the intelligent transport system.
2. Description of Related Art
Heretofore, the vehicle-onboard DSRC apparatus is well known in the art which is designed to perform communication wirelessly with the on-road transport managing equipment such as the ETC system equipment installed in association with a road such as a toll road for the motor vehicles for exchanging or transferring various information with the on-road transport managing equipment or ETC system.
In general, the receiving sensitivity of the vehicle-onboard DSRC apparatus is set lower than −60.5 dBm inclusive in conformance with the stipulations of the Standards prescribed for such vehicle-onboard DSRC apparatus. Further, the non-response level is required to be lower than −70.5 dBm inclusive.
Under the circumstances, the sensitivity of the vehicle-onboard DSRC apparatus is so adjusted as to lie within a range of −60.5 dBm to −70.5 dBm in the manufacturing factory, i.e., before shipping of the vehicle-onboard DSRC apparatus. In this conjunction, it is however noted that in the stage of manufacturing of the DSRC apparatus, it is not yet known on what type or species of the motor vehicle the DSRC apparatus is destined to be mounted. For this reason, the sensitivity of the DSRC apparatus is ordinarily and generally set at an average value on the order of −65 dBm.
For better understanding of the concept underlying the present invention, description will first be made in some detail of the conventional vehicle-onboard DSRC apparatus known heretofore.
FIG. 4
of the accompanying drawings is a block diagram showing schematically and generally a structure of a conventional vehicle-onboard DSRC (Dedicated Short-Range Communication) apparatus which constitutes a part of an ETC (Electronic Toll Collection) system and which is comprised of a transmitting/receiving unit for performing communication with the ETC system (typical one of the on-road transport managing equipment) via a vehicle-onboard antenna and an overhead antenna unit of the ETC system (described hereinafter) and a control unit (not shown).
Referring to
FIG. 4
, the vehicle-onboard DSRC apparatus
10
includes a receiver section which is composed of a vehicle-mounted antenna
11
(i.e., antenna mounted on the vehicle) for receiving a radio signal sent from the on-road transport managing equipment such as the ETC system, a low-noise amplifier
12
for amplifying the received signal, a mixer circuit
13
for converting the frequency of the received signal into a low frequency by making use of a frequency of a local oscillator (not shown), a semi-fixed variable gain amplifier
14
for amplifying the signal outputted from the mixer circuit
13
, a detector circuit
15
for restoring received data from the received signal through demodulation or decoding, and a received data processing unit
16
for processing the received data.
FIG. 5
is a schematic side elevational diagram for illustrating in an outer appearance a general arrangement or configuration of a conventional ETC (electronic toll collection) system, a typical one of the on-road transport managing equipment. As can be seen in
FIG. 5
, automobiles or motor vehicles running on a road includes various species or types of motor vehicles such as, for example, a passenger car C
1
, a motor truck C
2
, a van and others.
In this conjunction, it is noted that the position at which the vehicle-onboard DSRC apparatus is installed differs from one to another type of the motor vehicle. By way of example, in the passenger cars C
1
and motor truck C
2
shown in
FIG. 5
, the positions at which the respective vehicle-onboard DSRC apparatuses
101
and
102
are installed differ from each other. More specifically, the height of the vehicle driving position (and hence the position of the vehicle-onboard DSRC apparatus) as measured from the ground level or road surface differs from one to another type or species of the motor vehicle, as indicated in
FIG. 5
by H1 and H2 for the passenger car C
1
and the motor truck C
2
, respectively. In addition, distances between the front tip or end of the motor vehicle and the location at which the vehicle-onboard DSRC apparatus is mounted differs in dependence on the vehicle types, as indicated by L1 and L2 for the motor vehicles C
1
and C
2
, respectively, in FIG.
5
.
In more concrete, in the case of the passenger car C
1
, the position at which the vehicle-onboard DSRC apparatus
101
is mounted is low because the position of the driver's seat is low. Consequently, in the passenger car C
1
, the height H1 of the position at which the vehicle-onboard DSRC apparatus
101
is mounted lower than the height H2 of the position at which the vehicle-onboard DSRC apparatus
102
of the motor truck C
2
is mounted.
Moreover, it is noted that in the passenger car C
1
, the distance between the driver's seat and the front end of the car C
1
(referred to as the nose distance) is long. In other words, in the passenger car C
1
, the distance L1 between the front end and the position at which the vehicle-onboard DSRC apparatus
102
is mounted is longer than the distance L2 between the front end of the motor truck C
2
and the vehicle-onboard DSRC apparatus
102
.
On the other hand, in a toll gate or the like system of a toll road, an overhead antenna unit ANT is installed as a part of the on-road transport managing equipment such as the ETC system, as can also be seen in FIG.
5
. Additionally installed at a position in front of the overhead antenna unit ANT with a distance of several meters (e.g. 4 m) therefrom is a vehicle detector D for detecting the front end portion of the vehicle such as the passenger car C
1
, the motor truck C
2
and the others. Needless to say, the vehicle detector D constitutes a part of the on-road transport managing equipment such as the ETC system.
The on-road transport managing equipment or the ETC system in this illustrative case is so designed as to perform communication with the vehicle-onboard DSRC apparatus such as
101
;
102
via the vehicle-mounted antenna
11
and the overhead antenna unit ANT, starting from the time point at which the front end of the motor vehicle such as the passenger car C
1
, the motor truck C
2
or the like has just traversed the vehicle detector D.
FIG. 6
is a characteristic diagram for illustrating profiles of the electric field intensities (received powers) of the radio signal emitted from the overhead antenna ANT and received by the vehicle-onboard DSRC apparatus as a function of the positions of the DSRC apparatus, wherein the position of the vehicle-onboard DSRC apparatus is taken along the abscissa with the electric field in
Goins Davetta W.
Hofsass Jeffery
Mitsubishi Denki & Kabushiki Kaisha
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