JPH1031768A - On-vehicle terminal equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-vehicle terminal equipment capable of reducing size and cost by sharing circuits in the case of receiving and processing an electric toll collection(ETC) radio wave from a road side device and either one of a road side beacon radio wave and a global positioning system(GPS) satellite radio wave. SOLUTION: In the case of respectively converting an ETC radio wave, a road side beacon radio wave and a GPS position measuring satellite radio wave into intermediate frequency components and supplying local oscillation signals corresponding to the ETC radio wave and the beacon radio wave or the GPS radio wave, the levels of the ETC radio wave and the beacon radio waves are respectively detected by a level detection circuit 201. When judged that the level of the ETC radio wave is higher than its reference value, a selection control circuit 48 selects a local oscillation signal corresponding to the ETC radio wave. When judged that the level of the beacon radio wave is higher than its reference value, the circuit 48 selects a local oscillation signal corresponding to the beacon radio wave. In the other case, a local oscillation signal corresponding to the GPS radio wave is selected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention reduces traffic congestion and toll collection work at tollgates on toll roads, and provides data necessary for driving assistance based on information obtained from roadside beacons and GPS positioning satellites. The present invention relates to a multi-function in-vehicle terminal device obtained and provided to a passenger.

[0002]

2. Description of the Related Art Conventionally, at a tollgate on a toll road, a vehicle-specific number is wirelessly communicated between a roadside device installed at a predetermined place of the tollgate and a vehicle-mounted terminal device, so that the tollgate is operated at the tollgate. There has been proposed a toll collection device for toll roads in which a vehicle is passed without stopping and toll collection is performed at another occasion (ETC; Electric Toll Collection. See Japanese Patent Publication No. 7-46394).

[0003] A communication device (hereinafter referred to as "roadside beacon") is installed on the road, and radio waves including position information and road information (hereinafter referred to as "beacon radio waves") are transmitted from the roadside beacon.
By radiating it toward a relatively small area, and receiving the radiated beacon radio wave at the vehicle, knowing the current position of the vehicle, displaying it to the passengers, as well as the location of the intersection, the name of the intersection, the shape of the intersection , Road regulation information,
BACKGROUND ART Road information useful for passengers, such as traffic congestion and accident information, has been obtained.

On the other hand, GPS (Global Positioning System)
m) There is known a technology for measuring a position of a user using radio waves from a satellite (hereinafter referred to as "GPS radio waves"). The principle is to measure its own two-dimensional or three-dimensional position by measuring the propagation delay time of radio waves emitted by a plurality of artificial satellites orbiting in a predetermined orbit. By receiving such GPS satellite radio waves, the current position of the vehicle is set and displayed based on the measured data.

However, radio waves from toll collection devices on toll roads (hereinafter referred to as "ETC radio waves"), beacon radio waves, and GPS radio waves have different frequencies.
Also, the signal modulation method and the reception level are different. Therefore, a radio frequency amplifier, a mixer, an oscillator, and a computer circuit for processing data are required for each radio wave. Therefore, the in-vehicle terminal device is substantially the same as mounting three expensive receivers such as an ETC transceiver, a roadside beacon receiver, and a GPS receiver on a vehicle, which increases the circuit scale and increases cost. Leads to. further,
Since power consumption also increases, members such as a heat radiating plate become large, and it is also difficult to secure an installation place.

Therefore, the roadside beacon radio wave and the GPS
In the case of receiving and processing both satellite radio waves, there has been proposed a vehicle information receiving apparatus which can be reduced in size by sharing a circuit and which can reduce the cost (Japanese Patent Laid-Open No. 6-317651). reference).

[0007]

However, as described above, when the toll collection device for a toll road is mounted on a vehicle, if the circuit of the toll collection device can be added and shared, the entire device will be used. The size can be further reduced, and the cost can be reduced. Therefore, the present invention solves the above technical problem, when receiving and processing any two or three of the radio wave of the roadside device of the tollgate of the toll road, the roadside beacon radio wave and the GPS satellite radio wave, It is an object of the present invention to provide an in-vehicle terminal device that can be downsized by sharing a circuit and that can reduce costs.

[0008]

[Means for Solving the Problems]

(1) An on-board terminal device of the present invention includes a first receiving circuit for receiving an ETC radio wave radiated from a roadside automatic toll collection system installed at a tollgate, and a radio wave radiated from a roadside beacon installed on a road. A second receiving circuit for receiving radio waves,
A third receiving circuit for receiving GPS radio waves, an ETC radio wave,
A conversion circuit for converting the radio wave of the roadside beacon and the radio wave of the GPS positioning satellite into an intermediate frequency, respectively;
A local oscillation circuit capable of supplying a local oscillation signal corresponding to a C radio wave, a beacon radio wave or a GPS radio wave, a data processing circuit, a level detection circuit for detecting levels of an ETC radio wave and a beacon radio wave, and the level detection circuit When it is determined that the level of the ETC radio wave is higher than the reference value, a local oscillation signal corresponding to the ETC radio wave is selected, and when it is determined that the level of the beacon radio wave is higher than the reference value, the local oscillation signal is selected. A selection control circuit for selecting a local oscillation signal and selecting a local oscillation signal according to the GPS radio wave when any of the signals is lower than the reference value (claim 1).

According to the above configuration, the GPS radio wave can be received at all times, but when it is determined that the level of the ETC radio wave is higher than the reference value, that is, when the vehicle enters the range of the roadside automatic toll collection system. When the local oscillation signal according to the ETC radio wave is selected and the level of the beacon radio wave is determined to be higher than the reference value, that is, when the vehicle enters the range of the roadside beacon, the local oscillation signal according to the beacon radio wave is selected. can do.

Therefore, the provision of the level detection circuit and the selection control circuit makes it possible to cope with three radio waves, so that the intermediate frequency amplification section after the conversion circuit can be shared. When it is determined that both the level of the ETC radio wave and the level of the beacon radio wave are higher than the reference values, it is preferable to select a local oscillation signal according to the ETC radio wave. (2) The level detection circuit demodulates a constant frequency amplitude modulation component included in the ETC radio wave and the beacon radio wave, and detects the level of the radio wave of the automatic toll collection system and the radio wave of the roadside beacon based on the amplitude modulation component. (Claim 2).

According to this configuration, it is possible to detect the presence of a radio wave without being affected by noise, based on the amplitude modulation component, focusing on the modulation method of the transmission signals of the ETC radio wave and the beacon radio wave. (3) the level detection circuit, a second level detection circuit that directly detects the level of the radio wave of the roadside beacon, and demodulates the amplitude modulation component contained in the radio wave of the automatic toll collection system and the radio wave of the roadside beacon, A first level detection circuit for detecting the level of the radio wave of the automatic toll collection system and the radio wave of the roadside beacon based on the modulation component, wherein the selection control circuit detects the level of the roadside based on the output of the first level detection circuit. When it is determined that the level of the radio wave of the beacon has become larger than the reference value, the local oscillation signal corresponding to the radio wave of the roadside beacon is selected. When the level detection circuit determines that the level of the radio wave of the roadside beacon has become smaller than the reference value, it switches to a local oscillation signal corresponding to the radio wave of the GPS positioning satellite. (Claim 3).

According to this configuration, when selecting the local oscillation signal according to the radio wave of the roadside beacon and when selecting the local oscillation signal according to the radio wave of the automatic toll collection system, the first
The selection is performed based on the output of the level detection circuit. When the local oscillation signal corresponding to the radio wave of the roadside beacon is selected, whether or not the local oscillation signal is out of the range of the roadside beacon is selected according to the second method.
Is performed based on the output of the level detection circuit.

The reason for this is that if the beacon radio wave is detected based on the amplitude modulation component of a constant frequency included in the beacon radio wave, the amplitude modulation component will erroneously decrease instantaneously when passing through the roadside beacon. In some cases, the second level detection circuit directly detects the level of the radio wave of the roadside beacon because the second level detection circuit operates. In addition, the meaning of "directly detect" means detecting the intensity of a radio wave without demodulating an amplitude modulation component. For example, the detection may be performed at a stage subsequent to the intermediate frequency amplification stage (in this case, since the detection is performed when switching to the radio wave of the roadside beacon, the radio wave of the roadside beacon is converted to the intermediate frequency). (4) The in-vehicle terminal device of the present invention includes a first receiving circuit for receiving a radio wave radiated from a roadside automatic toll collection system installed at a tollgate, and a third receiving circuit for receiving a radio wave from a GPS positioning satellite. Receiving circuit, radio wave of automatic toll collection system,
A conversion circuit for converting the radio waves of the GPS positioning satellites into intermediate frequencies, a local oscillation circuit capable of supplying a local oscillation signal corresponding to the radio waves of the automatic toll collection system or the radio waves of the GPS positioning satellites to the conversion circuit, A processing circuit, a radio wave of an automatic toll collection system, a level detection circuit for detecting a radio wave of a GPS positioning satellite, respectively, and when the level detection circuit determines that the level of the radio wave of the automatic toll collection system is higher than a reference value, The local oscillation signal corresponding to the radio wave of the automatic toll collection system is selected, and when it is determined that the level of the radio wave of the automatic toll collection system is lower than the reference value, the local oscillation signal according to the radio wave of the GPS positioning satellite is selected. And a selection control circuit (claim 4).

According to this in-vehicle terminal device, the GPS terminal is always used.
Although it is possible to receive radio waves, when it is determined that the level of the ETC radio waves is higher than the reference value, that is, when it is within the range of the roadside automatic toll collection system, select a local oscillation signal according to the ETC radio waves. Can be. Therefore, by providing the level detection circuit and the selection control circuit, it is possible to cope with the two radio waves of ETC and GPS, so that the intermediate frequency amplifier after the conversion circuit can be shared. (5) The level detection circuit demodulates a constant frequency amplitude modulation component included in the radio wave of the automatic toll collection system, and detects the level of the radio wave of the automatic toll collection system based on the amplitude modulation component. It is preferably present (claim 5).

According to this configuration, E from the toll collection device
Focusing on the modulation method of the transmission signal of the TC radio wave, the presence of the radio wave can be detected based on the amplitude modulation component without being affected by noise. (6) The in-vehicle terminal device of the present invention includes a first receiving circuit that receives a radio wave radiated from a roadside automatic toll collection system installed at a tollgate, and a radio wave radiated from a roadside beacon installed on the road. A second receiving circuit for receiving the radio wave, a conversion circuit for converting the radio wave of the automatic toll collection system and the radio wave of the roadside beacon to an intermediate frequency, respectively, and the conversion circuit responding to the radio wave of the automatic toll collection system or the radio wave of the roadside beacon; A local oscillation circuit capable of supplying a local oscillation signal, a data processing circuit, a level detection circuit for detecting the level of the radio wave of the automatic toll collection system and the level of the radio wave of the roadside beacon, and an automatic toll collection by the level detection circuit. If it is determined that the level of the radio wave of the system is higher than the reference value, select the local oscillation signal corresponding to the radio wave of the automatic toll collection system and When it is determined that the level of the radio wave of the beacon is higher than the reference value, the local oscillation signal corresponding to the radio wave of the roadside beacon is selected, and when both are lower than the reference value, the local oscillation signal corresponding to the radio wave of the roadside beacon is selected. Or a selection control circuit that does not select any of the local oscillation signals.

According to this vehicle-mounted terminal device, when it is determined that the level of the ETC radio wave is higher than the reference value, that is, when the vehicle enters the range of the roadside automatic toll collection system, E
A local oscillation signal corresponding to the TC radio wave can be selected,
When it is determined that the level of the beacon radio wave is higher than the reference value, that is, when the vehicle enters the range of the roadside beacon,
A local oscillation signal according to the beacon radio wave can be selected.

Therefore, by providing the level detection circuit and the selection control circuit, two levels of the ETC and the roadside beacon are provided.
Since it is possible to cope with two radio waves, the intermediate frequency amplifier after the conversion circuit can be shared. If neither of the local oscillation signals is selected when neither signal is received, for example, the power supply of only the level detection circuit and the data processing circuit is always turned on, and the other circuits (the conversion circuit and the local Always turn off the power of the oscillator circuit)
By turning on the power of the other circuits when the data processing circuit recognizes that the level detection circuit has operated, ordinary power consumption can be reduced. (7) The level detection circuit demodulates the amplitude modulation component of a constant frequency included in the radio wave of the automatic toll collection system and the radio wave of the roadside beacon, and based on the amplitude modulation component, the radio wave of the automatic toll collection system and the roadside beacon. It is preferable to detect the level of the radio wave (claim 7).

According to this configuration, it is possible to detect the presence of a radio wave without being affected by noise, based on the amplitude modulation component, focusing on the modulation method of the transmission signals of the ETC radio wave and the beacon radio wave. (8) The level detection circuit, a second level detection circuit that directly detects the level of the radio wave of the roadside beacon, and demodulates the amplitude modulation component contained in the radio wave of the automatic toll collection system and the radio wave of the roadside beacon. A first level detection circuit for detecting the level of the radio wave of the automatic toll collection system and the radio wave of the roadside beacon based on the modulation component, wherein the selection control circuit detects the level of the roadside based on the output of the first level detection circuit. When it is determined that the level of the radio wave of the beacon has become larger than the reference value, the local oscillation signal corresponding to the radio wave of the roadside beacon is selected. When the level detection circuit determines that the level of the radio wave of the roadside beacon has become smaller than the reference value, it switches to the local oscillation signal corresponding to the radio wave of the automatic toll collection system. It is preferable that none or any of the local oscillation signals is selected (claim 8).

According to this configuration, when selecting the local oscillation signal corresponding to the radio wave of the roadside beacon, the selection is performed based on the output of the first level detection circuit. When a signal is selected, it is determined whether the signal has left the range of the roadside beacon based on the output of the second level detection circuit. The reason for this is that if the beacon radio wave is detected based on the amplitude modulation component of a certain frequency included in the beacon radio wave, the amplitude modulation component will be instantaneously reduced when passing through the roadside beacon, and will operate incorrectly. Therefore, the level of the radio wave of the roadside beacon is directly detected by the second level detection circuit.

The advantage of "not selecting any local oscillation signal" is as described in claim 6. (9) The in-vehicle terminal device according to the present invention includes a first receiving circuit that receives a radio wave radiated from a roadside automatic toll collection system installed at a tollgate, and a radio wave radiated from a roadside beacon installed on the road. A second receiving circuit for receiving the radio wave, a conversion circuit for converting the radio wave of the automatic toll collection system and the radio wave of the roadside beacon to an intermediate frequency, respectively, and the conversion circuit responding to the radio wave of the automatic toll collection system or the radio wave of the roadside beacon; A local oscillation circuit that can supply a local oscillation signal, a data processing circuit, a level detection circuit that detects the level of radio waves of the automatic toll collection system, and the level detection circuit that adjusts the level of radio waves of the automatic toll collection system. When it is determined that the signal is higher than the reference value, a local oscillation signal corresponding to the radio wave of the automatic toll collection system is selected, and the level of the radio wave of the automatic toll collection system is selected. And a selection control circuit for selecting a local oscillation signal according to the radio wave of the roadside beacon when it is determined that the level is lower than the reference value.

According to this in-vehicle terminal device, when it is determined that the level of the ETC radio wave is higher than the reference value, that is, when the vehicle enters the range of the roadside automatic toll collection system,
When the local oscillation signal according to the TC radio wave is selected and the level of the ETC radio wave is determined to be lower than the reference value, that is, when the local oscillation signal is out of the range of the roadside automatic toll collection system, the local oscillation signal according to the beacon radio wave is transmitted. You can choose.

Therefore, the provision of the level detection circuit and the selection control circuit makes it possible to cope with two radio waves, so that the intermediate frequency amplifier after the conversion circuit can be shared. (10) The level detection circuit demodulates a constant frequency amplitude modulation component included in the radio wave of the automatic toll collection system, and detects the level of the radio wave of the automatic toll collection system based on the amplitude modulation component. (Claim 10).

According to this configuration, E from the toll collection device
Focusing on the modulation method of the transmission signal of the TC radio wave, the presence of the radio wave can be detected based on the amplitude modulation component without being affected by noise. (11) The selection control circuit may select the local oscillation signal only when the state where the level of the radio wave is higher or lower than the reference value continues for a certain period of time (claim 11). .

The level of the radio wave may suddenly and suddenly decrease due to interference with a reflected wave from a vehicle or the like or shielding of a vehicle running sideways. The invention of claim 11 prevents the selection control circuit from malfunctioning due to the instantaneous reduction of the radio wave level.

[0025]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. <Outline of System> First, FIG. 1 is a diagram showing an outline of a road-to-vehicle communication system at a tollgate on a toll road, in which lanes through which vehicles enter are arranged, and road facilities are arranged along each lane. . Although the number of lanes may be any, it is noted that FIG. 1 shows two lanes for convenience.

[0026] To explain by focusing on the back of the lane, road facilities, and vehicle intrusion detectors 2a to sense the entry of the vehicle into the zone Z _a, leave detector 4a for detecting the departure of the vehicle from the zone Z _a And These vehicle entry sensors 2
a, the leaving sensor 4a detects the presence of a vehicle by a photoelectric sensor, an ultrasonic sensor, or the like.
The change of the magnetic field due to the passage of the vehicle may be detected by a loop sensor embedded in the ground.

[0027] The road equipment, a vehicle type discriminating apparatus 1a-1, 1a-2 to determine the vehicle type of the vehicle that has entered the zone Z _a,
An antenna unit 5a for communicating with the in-vehicle terminal device;
A vehicle number reading camera 3a is provided. The vehicle type discriminating apparatus 1a measures the height of the vehicle by using a plurality of pairs of light emitting and receiving devices 1a-1 installed in a vertical direction, and the pressure sensor 1 embedded in a road.
The tire width, tread width, and number of shafts are detected by a-2 (see Japanese Patent Publication No. 4-68080). The vehicle number reading camera 3a is a camera used in a vehicle number reading system that detects a passing vehicle, cuts out the license plate frame, extracts a character area, and recognizes a number (Japanese Patent Laid-Open No. 3-265999). Gazette).

The communication between the on-road equipment and the on-board terminal device will be performed at a frequency of 2.5 GHz or 5.8 GHz, AM modulation, transmission power of 300 mW, and data rate of 1 MHz. Further road facilities, a roadside device 6a, the guide display board 7a for guiding display to a vehicle driver that leave the zone Z _a
And a display end sensor 8a. The display end sensor 8a is provided for confirming that the driver of the vehicle has finished viewing the display on the guidance display panel 7a and has proceeded with the vehicle further.
It is a vehicle sensor.

Although not shown, the on-road equipment is provided with an automatic toll-issuing machine and a camera for photographing vehicles. The automatic toll issuing machine is a facility used to issue a toll ticket by stopping the vehicle when it is determined that automatic toll collection cannot be performed, and an existing one can be used. The vehicle photographing camera is used at the time of issuance of a toll ticket and when there is an illegal act.

The above description focuses on one lane, but the same lane is also provided with the same on-road equipment (indicated by the suffix b in FIG. 1). Since the configuration of both on-road equipment is exactly the same, the description is omitted.
Next, an outline of the roadside beacon communication system will be described. As shown in FIG. 2, a roadside beacon antenna A is installed on a road, and a radio wave is radiated from the roadside beacon antenna A toward the road.

The radio wave radiated from the roadside beacon antenna A is received by a vehicle-mounted terminal device mounted on a vehicle traveling on a road. The reception level of the radio wave is, for example, an electric field intensity distribution spreading around the roadside beacon antenna A as shown in FIG. The reception level is set to a reference level. When a radio wave higher than the reference level can be received, the vehicle can use the roadside beacon electric wave without being affected by noise or the like, that is, within the service area of the roadside beacon. It is determined that the vehicle is traveling (within the range of ± D from the installation location of the antenna A).

In this embodiment, a roadside beacon is provided so that the original function of calibrating the current position of the vehicle to the installation position of the roadside beacon antenna when the vehicle comes directly below the installation position of the roadside beacon antenna can be performed accurately. The antenna is composed of two antenna elements having different main radiation directions, and an in-phase carrier (1.5 GHz) that is FSK-modulated or PSK-modulated by vehicle information is supplied to each antenna element. . Further, each carrier is amplitude-modulated by a signal of 1 kHz having an opposite phase to each other. Therefore, the in-vehicle terminal device detects the position of the vehicle and determines the traveling direction by extracting the phase change of the amplitude modulation component, and
Various data can be restored by extracting a K or PSK modulation component.
-71400 and JP-A-2-183182). With this method, it is possible to provide traffic information data to a vehicle as wide as possible while maintaining the accuracy of vehicle position detection. <First Embodiment> FIG. 4 shows an in-vehicle terminal device 10 according to the present invention.
FIG. 2 is a block diagram showing an in-vehicle device 12 in which is incorporated.

The in-vehicle terminal device 10 receives, demodulates and processes a beacon electric wave installed on the ground, an electric wave from a GPS satellite, and an ETC electric wave from an antenna unit of a tollgate. 11b is an antenna for receiving beacon radio waves (referred to as beacon antenna), 11a is an antenna for receiving GPS radio waves (referred to as GPS antenna), and 11c is E
Antenna that receives TC radio waves (called ETC antenna)
It is.

FIG. 5 shows an installation example of each antenna. According to the figure, a beacon antenna 11b is installed behind a rear seat, a GPS antenna 11a is installed above a rear fender of a vehicle body, and an ETC antenna 11c is installed on a dashboard. FIG.
As shown in FIG. 5, a disk 32 storing road map data and the like, reading of a road map in a predetermined range, vehicle position information obtained from the on-vehicle terminal device 10,
Various information such as input and processing of road information and toll information, creation of guidance display data for guiding a vehicle, voice guidance by a speaker 35, control of a display device 33, and control of a vehicle position detection unit (not shown). Controller 31 for controlling the vehicle and a display device 33 for displaying road information and toll information and displaying the detected vehicle position together with a map
And a remote controller 34.

FIG. 6 is an internal block diagram of the in-vehicle terminal device 10. The inside of the in-vehicle terminal device 10 is roughly divided into a GPS signal processing system, a beacon signal processing system, an ETC signal processing system, and a signal processing system. The GPS signal processing system includes a preamplifier 13 for amplifying a signal received by the GPS antenna 11a, a bandpass filter 14, a mixer 15 for mixing signals from the local oscillator 16, and an intermediate frequency filter 27.

The beacon signal processing system includes a band-pass filter 18 for band-passing a signal received by the beacon antenna 11b, a mixer 19 for mixing signals from the local oscillator 16, and an intermediate frequency filter 28.
The ETC signal processing system includes a switching circuit 23 for switching between transmission and reception based on a transmission / reception switching signal, and a bandpass filter 2.
4, a mixer 25 for mixing the signal from the local oscillator 16, an intermediate frequency filter 29, and a transmission circuit 26 for generating a return signal of fee information to road facilities.

The signal processing system includes a level detection circuit 20 for detecting the level of a GPS signal, a beacon signal or an ETC signal.
And a data demodulation circuit 21 for demodulating data included in the frequency-converted signal, a phase detection circuit 22 for detecting the phase of the frequency-converted signal, and a data processing circuit 17 for processing the demodulated signal. . The data processing circuit 17 is depicted as one block in each drawing attached to the present application. However, in practice, separate data processing circuits will be used for the ETC signal processing unit and the GPS signal and beacon signal processing units. This is because the processing of the ETC signal performs electronic commerce and therefore requires a high degree of reliability and security, and if integrated with the processing unit for the GPS signal and the beacon signal, the management becomes complicated. However, except for management reasons, the data processing circuit 1
7 (the cost reduction and the miniaturization by using an ASIC) are recognized.
It is fully conceivable to integrate 7. In the following embodiments, the description will be given on the assumption that the data processing circuit 17 is integrated.

The level detection circuit 20 has a built-in band-pass filter (not shown) for separating a GPS signal, a beacon signal or an ETC signal, and compares each level with a reference value. This level detection circuit 2
The comparison signal of 0 is input to the data processing circuit 17, which determines whether or not the vehicle is in the communication range (service area) of the roadside beacon by using the road-vehicle communication system at the tollgate on the toll road. Check if you are within range. Depending on the findings,
In order to receive a desired signal, the local oscillator 16
Change the oscillation frequency of

In the in-vehicle terminal device 10, the GPS radio wave received by the GPS antenna 11 a is amplified by the preamplifier 13, and the noise component is removed by the bandpass filter 14. Bandpass filter 1
4 is converted to an intermediate frequency by a mixer 15 and directly input to a data processing circuit 17, where
The GPS signal is decoded, and the current position and the like are detected.

On the other hand, when the vehicle passes near the roadside beacon, the beacon radio wave is received by the beacon antenna 11b, and unnecessary frequency components are removed by the band pass filter 18. The signal passed through the band-pass filter 18 is applied to the local oscillator 1 shared with the GPS circuit.
The signal is converted into an intermediate frequency by the signal of No. 6 and input to the data demodulation circuit 21 and the phase detection circuit 22 through the intermediate frequency filter 28.

The data demodulation circuit 21 is for demodulating an FSK-modulated or PSK-modulated data signal (including vehicle information) contained in the intermediate frequency. The phase detection circuit 22 is for demodulating the amplitude modulations of opposite phases superimposed on the carrier wave and detecting the point in time when the phase changes. The data processing circuit 17 detects the installation position information of the roadside beacon obtained from the phase detection circuit 22, detects the road information obtained from the data demodulation circuit 21, and transmits the information to the navigation controller 31. The navigation controller 31 causes the display device 33 to display the position of the vehicle, and outputs the road information to the speaker 3.
Announcement from 5 and so on.

Further, when an ETC radio wave from the antenna unit 5a at the tollgate on the toll road is received, the radio wave is received by the ETC antenna 11c, passes through the switching circuit 23, and an unnecessary frequency component is filtered by the band pass filter 24. Removed. The signal that has passed through the band-pass filter 24 is converted into an intermediate frequency by the signal of the local oscillator 16 and input to the data demodulation circuit 21.

The data demodulation circuit 21 is for demodulating an FSK-modulated or PSK-modulated data signal (including charge information) contained in the intermediate frequency. By the way, the GPS signal and the beacon signal may compete with each other. For example, there is a case where the vehicle travels in the service area of the roadside beacon and can effectively receive radio waves from GPS satellites. In this case, the data processing circuit 17 preferentially inputs information obtained from the roadside beacon. That is, the data processing circuit 17 always receives the output of the level detection circuit 20 and, when determining that the level of the beacon radio wave is higher than the reference value (within the service area of the roadside beacon), changes the frequency of the local oscillator 16. Switch to a frequency that can receive beacon signals.

When the ETC signal and the GPS signal compete with each other, the data processing circuit 17 preferentially inputs information obtained from the toll gate. That is, when the data processing circuit 17 determines that the level of the ETC signal is higher than the reference value (it is within the service area of the tollgate), the data processing circuit 17 switches the frequency of the local oscillator 16 to a frequency at which the ETC signal can be received.

When the ETC signal and the beacon signal compete with each other, information obtained from the toll gate is preferentially input. That is, the data processing circuit 17
When it is determined that the level of the ETC signal is higher than the reference value (it is within the service area of the tollgate), the frequency of the local oscillator 16 is switched to a frequency at which the ETC signal can be received.

With the above-described circuit configuration of the in-vehicle terminal device 10, it is possible to detect the current position and the like based on the GPS signal, and to obtain the installation position information and the road information when passing near the roadside beacon. Can be. When passing through a tollgate on a toll road, toll information can be exchanged. In this manner, one data processing circuit 17 can preferentially process any one of the ETC radio wave, the beacon radio wave, and the radio wave from the GPS satellite, and supply the processed radio wave to the navigation controller 31.

FIG. 7 is a block diagram showing a more specific configuration of the in-vehicle terminal device shown in FIG. The in-vehicle terminal device 10 shown in FIG.
3 and a signal line 52. The antenna unit 11
Beacon antenna 11b, GPS antenna 11a, ET
A preamplifier 1 in which a C antenna 11c is formed in the form of a printed antenna on one substrate and amplifies a GPS signal
3. a switching circuit 23 for switching between transmission and reception of the ETC signal;
The band-pass filters 14, 18, 24 and the hybrid 41 are formed on the same substrate.

By integrating the antenna on the substrate in this manner, the antenna needs to be installed in only one place, the antenna can be reduced in size, and the number of coaxial cables 42 and 43 for extracting signals can be reduced from three to two. The arrangement of the coaxial cable in the inside becomes easy, and the number of expensive high-frequency coaxial connectors connected to the in-vehicle terminal device 10 can be reduced from three pairs to two pairs.

The on-vehicle terminal device 10 changes the frequency of the local oscillation circuit using the selection circuit 48 (frequency synthesizer).
7, 47 are shared. Further, two types of level detection circuits, a first level detection circuit 201 and a second level detection circuit 202, are provided. More specifically, as shown in FIG. 7, the in-vehicle terminal device 10 includes a signal processing system including a selection circuit 48, a first level detection circuit 201,
And a second level detection circuit 202.

The signal processing system includes a broadband amplifier 4 for amplifying a signal input from the coaxial cable 42 (a signal from an antenna unit at a tollgate, a beacon signal, or a GPS signal).
4. Hybrid 45, mixer 46, narrow band intermediate frequency filter 27, intermediate frequency amplifier 47, data demodulation circuit 21 for demodulating data contained in the signal, phase detection circuit 22 for detecting the phase of the signal, and demodulated signal Has a data processing circuit 17 for processing.

The selection circuit 48 includes a frequency synthesizer and a CPU, and switches the frequency of the local oscillator 16 by selecting a frequency based on the output signals of the first level detection circuit 201 and the second level detection circuit 202. The first level detection circuit 201 demodulates an amplitude modulation component included in a radio wave and a beacon radio wave of the automatic toll collection system, and detects a level of a radio wave or a beacon radio wave of the automatic toll collection system based on the amplitude modulation component. , A detector 201a, a band-pass filter 201b for extracting a 1 kHz amplitude modulation component included in the beacon radio wave, a comparator 201c for comparing the level of this signal with a reference value, and a radio wave of the automatic toll collection system. It has a band-pass filter 201d for extracting an amplitude modulation component of 1 MHz, and a comparator 201e for comparing the level of this signal with a reference value. This is to check if you are in the area.

The reason why the amplitude modulation component is extracted and detected is that the band-pass filters 14, 18 and 24 are used.
Is a wide band (approximately 20 to 50 MHz), so there is a good possibility that undesired radio waves are mixed. For example, since there are frequency bands such as microwave ovens, medical devices, and wireless LANs near the frequency (2499.7 MHz) of the roadside beacon, these radio waves may be erroneously detected and malfunction. Therefore, if the amplitude modulation component is extracted and examined as described above, the presence of the area can be correctly detected without erroneous detection.

The comparator 201 of the first level detection circuit 201
When the output signal of “c” is input to the selection circuit 48, the selection circuit 48 sends a signal for switching the frequency of the local oscillator 16 to a frequency corresponding to the frequency of the roadside beacon, and outputs the signal of the comparator 201 e of the first level detection circuit 201. When the output signal is input to the selection circuit 48, the selection circuit 48 sends a signal for switching the frequency of the local oscillator 16 to a frequency corresponding to the frequency of the automatic toll collection system.

The second level detection circuit 202 is for directly detecting the level of the beacon radio wave when the vehicle is in the area of the roadside beacon and comparing it with the reference level. The level of the intermediate frequency of the beacon radio wave is monitored by the second level detection circuit 202 through the narrow-band intermediate frequency filter 27. Unlike the amplitude modulation component (see the broken line in FIG. 3), the level of the intermediate frequency does not drop sharply in front of the roadside beacon, and passes through the narrow-band intermediate frequency filter 27. It is not affected by radio waves. Therefore, the level of the beacon radio wave can be accurately detected and switched without being affected by other radio waves.

In this embodiment, the selection circuit 48 sets the frequency of the local oscillator 16 to a GPS signal or ETC.
When the frequency of the local oscillator 16 is switched to the frequency corresponding to the roadside beacon, the second level detection circuit responds to the output signal of the first level detection circuit 201 when the frequency is switched to the frequency corresponding to the signal of the roadside beacon. It has a logic characteristic of responding only to a decrease in the output signal of the output signal 202.

The operation of the in-vehicle terminal device 10 will be described with reference to a flowchart (FIG. 8). Coaxial cable 4
2, the signal is amplified by a wideband amplifier 44 and divided by a hybrid 45,
One of them is converted to the intermediate frequency of the GPS signal by the mixer 46.

The other signal divided by the hybrid 45 enters the first level detection circuit 201, where
A 1-kHz signal, which is an amplitude modulation component of the roadside beacon radio wave, is extracted by the band-pass filter 201b, and the level of the 1-kHz signal is constantly monitored by the comparator 201c. At the same time, a 1-MHz signal, which is the amplitude modulation component of the radio wave of the automatic toll collection system, is extracted by the band-pass filter 201d, and the level of the 1-MHz signal is constantly monitored by the comparator 201e (step S1).

If the monitoring level of the 1 kHz signal exceeds the reference value, it is determined that the vehicle has entered the roadside beacon service area, and the frequency of the local oscillator 16 is switched to a frequency corresponding to the frequency of the roadside beacon (step S3). . In this case, the level of the intermediate frequency of the roadside beacon converted to the intermediate frequency is the second level detection circuit 2
02 (Step S5). The detection level of the second level detection circuit 202 is the amplitude modulation component (FIG.
(See the broken line in FIG. 7)), which does not drop sharply in front of the roadside beacon, and because it passes through the narrow-band intermediate frequency filter 27, it is not affected by other radio waves. . Therefore, the level of the beacon radio wave can be accurately detected without being affected by other radio waves.

When the detection level of the second level detection circuit 202 falls below the reference value, it is determined that the vehicle has left the service area of the roadside beacon. At that time, step S1
The first level detection circuit 201 returns to 1 kHz.
The signal level of z and the signal level of 1 MHz are constantly monitored. If the monitoring level of the 1 MHz signal is higher than the reference value, it is determined that the vehicle has entered the service area of the automatic toll collection system, and the frequency of the local oscillator 16 is switched to the frequency of the ETC signal (step S).
2) Otherwise, unless the monitoring level of the 1 kHz signal exceeds the reference value, the frequency of the local oscillator 16 is switched to the frequency of the GPS signal (step S).
4).

As described above, the intermediate frequency filter 27
And the signal passing through the intermediate frequency amplifier 47 is normally GP
If the vehicle enters the service area of the roadside beacon, the signal becomes a reception signal of the roadside beacon. If the vehicle enters the service area of the automatic toll collection system, the signal becomes E.
It becomes a TC reception signal. The processing in the data demodulation circuit 21, the phase detection circuit 22, and the data processing circuit 17 is as follows.
Since the content is the same as that described with reference to FIG. 6, the description is omitted.

FIG. 9 is a block diagram showing a circuit configuration according to another embodiment. The circuit of FIG. 9 differs from the circuit of FIG. 7 in that the detector 51 is provided in the antenna unit 11 instead of the in-vehicle terminal device 10 and that the circuit for transmitting the ETC radio wave is omitted. The reason why the detector 51 is provided in the antenna unit 11 is that if the frequency of the ETC radio wave is increased from supposedly 2.5 GHz to 5.8 GHz in the future, the coaxial cable 43 is transmitted at a high frequency without causing a propagation loss. This is because the detector 201a is provided in the antenna unit 11 so as to reduce the frequency of the signal transmitted through the coaxial cable 43 and reduce the propagation loss. According to trial calculation, frequency 2.5GHz
, The transmission loss of a coaxial cable (outer diameter: 3.8 mm) is 0.9 dB per meter, and is 1.4 dB per meter at a frequency of 5.8 GHz. Assuming a 3 m coaxial cable, the difference in transmission loss is 1. It is estimated to be 5 dB. Also,
Since the detector 51 itself is also expensive, it is better to manufacture the antenna 51 by hybridizing it with other elements in the antenna unit 11.
This is because the manufacturing cost is also advantageous. Also, ETC
The transmission power of the radio wave is stronger than the transmission power of the radio wave of the beacon, which also depends on the fact that the AM modulated wave can be directly detected.

It should be noted that the reason for omitting the transmission circuit of the ETC radio wave is merely that a reception-only terminal device is used. It is of course possible to add a transmission circuit. <Second Embodiment> FIG. 10 is a block diagram showing an in-vehicle terminal device according to a second embodiment. This in-vehicle terminal device receives, demodulates and processes a GPS radio wave from a GPS satellite and an ETC radio wave from an antenna unit at a tollgate.
11a indicates a GPS antenna, and 11c indicates an ETC antenna.

The inside of the vehicle-mounted terminal device 10 is roughly divided into a GPS signal processing system, an ETC signal processing system, and a signal processing system. The GPS signal processing system includes a preamplifier 13 for amplifying a signal received by the GPS antenna 11a, a bandpass filter 14, a mixer 15 for mixing signals from the local oscillator 16, and an intermediate frequency filter 27.

The ETC signal processing system includes a switching circuit 23 for switching between transmission and reception based on a transmission / reception switching signal, a bandpass filter 24, a mixer 25 for mixing signals from the local oscillator 16, an intermediate frequency filter 29,
And a transmission circuit 26 for generating a return signal of the fee information in the road facility. The signal processing system is a GPS signal or ET
It has a level detection circuit 20 for detecting the level of the C signal, a data demodulation circuit 21 for demodulating data included in the frequency-converted signal, and a data processing circuit 17 for processing the demodulated signal.

The level detection circuit 20 outputs a GPS signal or E
A band pass filter (not shown) for separating the TC signal is built in, and each level is compared with a reference value. The comparison signal of the level detection circuit 20 is input to the data processing circuit 17 and the data processing circuit 1
7 checks whether the vehicle is within the communication range of the road-vehicle communication system at the tollgate on the toll road. According to the examination result, the oscillation frequency of the local oscillator 16 is changed so that a desired signal can be received.

In the in-vehicle terminal device 10, the GPS radio wave received by the GPS antenna 11 a is amplified by the preamplifier 13, and the noise component is removed by the bandpass filter 14. Bandpass filter 1
4 is converted to an intermediate frequency by a mixer 15 and directly input to a data processing circuit 17, where
The GPS signal is decoded, and the current position and the like are detected.

On the other hand, when receiving the ETC radio wave from the antenna unit 5a at the tollgate on the toll road, the radio wave is received by the antenna 11c and
, Unnecessary frequency components are removed by the band-pass filter 24. The signal that has passed through the band-pass filter 24 is converted into an intermediate frequency by the signal of the local oscillator 16 and input to the data demodulation circuit 21.

The data demodulation circuit 21 is for demodulating the FSK-modulated or PSK-modulated data signal (including charge information) contained in the intermediate frequency. If the ETC signal and the GPS signal conflict, the data processing circuit 1
7 preferentially inputs information obtained from a tollgate. That is, the data processing circuit 17
If it is determined that the signal level is higher than the reference value (it is within the service area of the tollgate), the frequency of the local oscillator 16 is switched to a frequency at which the ETC signal can be received.

With the above-described circuit configuration of the in-vehicle terminal device 10, the current position and the like can be detected based on the GPS signal, and when passing through the tollgate on the toll road, the toll information can be exchanged. it can. In this manner, one data processing circuit 17 can preferentially process either the ETC radio wave or the radio wave from the GPS satellite and supply the processed radio wave to the navigation controller 31.

FIG. 11 is a block diagram showing a more specific configuration of the in-vehicle terminal device of FIG. The in-vehicle terminal device 10 shown in FIG.
2 and 43 and a signal line 52. Antenna unit 1
1 is to form a GPS antenna 11a and an ETC antenna 11c on a single board in the form of a printed antenna,
A preamplifier 13 for amplifying a PS signal, a switching circuit 23 for switching between transmission and reception of an ETC signal, broadband bandpass filters 14 and 24, and a hybrid 41 are formed on the same substrate.

By integrating the antenna on the board as described above, only one installation place for the antenna is required, and the number of coaxial cables 42 and 43 for extracting signals can be reduced from three to two. The cable can be easily routed, and the number of expensive high-frequency coaxial connectors to be connected to the in-vehicle terminal device 10 can be reduced from three to two. The in-vehicle terminal device 10 changes the frequency of the local oscillation circuit using the selection circuit 48, and thus shares the mixer 46 and the intermediate frequency amplifiers 27 and 47. Further, two types of level detection circuits, a first level detection circuit 201 and a second level detection circuit 202, are provided.

More specifically, the in-vehicle terminal device 10 comprises:
As shown in FIG. 11, a signal processing system including a selection circuit 48,
First level detection circuit 201 and second level detection circuit 2
02. The signal processing system includes a broadband amplifier 44, a hybrid 45, a mixer 46, a narrow band intermediate frequency filter 27, and an intermediate frequency amplifier for amplifying a signal (a signal from an antenna unit at a tollgate or a GPS signal) input from a coaxial cable 42. 47, a data demodulation circuit 21, and a data processing circuit 17 for processing the demodulated signal.

The selection circuit 48 includes the first level detection circuit 20
1. The frequency of the local oscillator 16 is switched by selecting a frequency based on the output signal of the second level detection circuit 202. The first level detection circuit 201
Demodulates the amplitude modulation component included in the radio wave of the automatic toll collection system, detects the level of the radio wave of the automatic toll collection system based on this amplitude modulation component, and detects the detector 201a and the ETC radio wave. It has a band-pass filter 201d for extracting an amplitude modulation component of 1 MHz and a comparator 201e for comparing the level of this signal with a reference value, thereby checking whether or not the vehicle is in the area of the automatic toll collection system. is there.

The comparator 201 of the first level detection circuit 201
When the output signal of e is input to the selection circuit 48, the selection circuit 48 sends a signal for switching the frequency of the local oscillator 16 to a frequency corresponding to the frequency of the automatic toll collection system. As described above, the GPS signal is normally received, but when the vehicle enters the service area of the automatic toll collection system, the signal becomes an ETC reception signal. <Third Embodiment> FIG. 12 is a block diagram showing an in-vehicle terminal device according to a third embodiment. This in-vehicle terminal device receives, demodulates and processes a beacon radio wave installed on the ground and an ETC radio wave from an antenna unit at a tollgate. 11b is a beacon antenna, 11c is ET
4 shows a C antenna.

The inside of the in-vehicle terminal device 10 includes a beacon signal processing system, an ETC signal processing system, and a signal processing system.
It is roughly divided into two. The beacon signal processing system includes a band-pass filter 18 that band-passes a signal received by the beacon antenna 11b, a mixer 19 that mixes signals from the local oscillator 16, and an intermediate frequency filter 28.

The ETC signal processing system includes a switching circuit 23 for switching between transmission and reception based on a transmission / reception switching signal, a bandpass filter 24, a mixer 25 for mixing signals from the local oscillator 16, an intermediate frequency filter 29,
And a transmission circuit 26 for generating a return signal of the fee information in the road facility. The signal processing system is a beacon signal or E
A level detection circuit 20 for detecting the level of the TC signal; a data demodulation circuit 21 for demodulating data included in the frequency-converted signal; a phase detection circuit 22 for detecting the phase of the frequency-converted signal; And a data processing circuit 17 for processing signals.

The level detection circuit 20 has a built-in band pass filter (not shown) for separating a beacon signal or an ETC signal, and compares each level with a reference value. The comparison signal of the level detection circuit 20 is input to the data processing circuit 17 and the data processing circuit 1
7 checks whether or not the vehicle is in the communication range (service area) of the roadside beacon and in the communication range of the road-vehicle communication system at the tollgate on the toll road. According to the examination result, the oscillation frequency of the local oscillator 16 is changed so that a desired signal can be received.

In the on-board terminal device 10, when the vehicle passes near the roadside beacon, the beacon radio wave is received by the beacon antenna 11b, and unnecessary frequency components are removed by the band pass filter 18. The signal that has passed through the band-pass filter 18 is converted into an intermediate frequency by the signal of the shared local oscillator 16, and is input to the data demodulation circuit 21 and the phase detection circuit 22 through the intermediate frequency filter 28.

The data demodulation circuit 21 is for demodulating the FSK-modulated or PSK-modulated data signal (including vehicle information) contained in the intermediate frequency. The phase detection circuit 22 is for demodulating the amplitude modulations of opposite phases superimposed on the carrier wave and detecting the point in time when the phase changes. The data processing circuit 17 detects the installation position information of the roadside beacon obtained from the phase detection circuit 22, detects the road information obtained from the data demodulation circuit 21, and transmits the information to the navigation controller 31. The navigation controller 31 causes the display device 33 to display the position of the vehicle, and outputs the road information to the speaker 3.
Announcement from 5 and so on.

Further, when the vehicle enters the tollgate area of the toll road and receives an ETC radio wave from the antenna unit 5a, the radio wave is received by the ETC antenna 11c, passes through the switching circuit 23, and becomes unnecessary by the band pass filter 24. Frequency components are removed. The signal passing through the band-pass filter 24 is converted into an intermediate frequency by the signal of the local oscillator 16, and is input to the data demodulation circuit 21 through the intermediate frequency filter 29.

The data demodulation circuit 21 is for demodulating the FSK-modulated or PSK-modulated data signal (including charge information) contained in the intermediate frequency. When the ETC signal and the beacon signal compete with each other, information obtained from the toll gate is preferentially input. That is, when the data processing circuit 17 determines that the level of the ETC signal is higher than the reference value (it is within the service area of the tollgate), the data processing circuit 17 switches the frequency of the local oscillator 16 to a frequency at which the ETC signal can be received.

With the above-described circuit configuration of the in-vehicle terminal device 10, installation location information and road information can be obtained when passing near a roadside beacon, and when passing through a tollgate on a toll road, toll information is obtained. Can be exchanged.
Thus, the ET is performed by one data processing circuit 17.
Prioritize processing of either C radio wave or beacon radio wave,
It can be supplied to the navigation controller 31.

FIG. 13 is a block diagram showing a more specific configuration of the in-vehicle terminal device of FIG. The in-vehicle terminal device 10 shown in FIG.
2 and 43 and a signal line 52. Antenna unit 1
1 is a beacon antenna 11b and an ETC antenna 11
c is formed in the form of a printed antenna on one substrate, and a switching circuit 23 for switching transmission and reception of ETC signals,
The bandpass filters 18 and 24 and the hybrid 41 of a wide band are formed on the same substrate.

The on-vehicle terminal device 10 changes the frequency of the local oscillation circuit using the selection circuit 48, and thus shares the mixer 46 and the intermediate frequency amplifiers 27 and 47. Further, two types of level detection circuits, a first level detection circuit 201 and a second level detection circuit 202, are provided.
More specifically, as shown in FIG. 13, the in-vehicle terminal device 10 is roughly divided into a signal processing system including a selection circuit 48, a first level detection circuit 201, and a second level detection circuit 202.

The signal processing system includes a broadband amplifier 44 for amplifying a signal (a signal from a tollgate antenna unit or a beacon signal) input from the coaxial cable 42, a hybrid 45, a mixer 46, a narrow band intermediate frequency filter 2
7, an intermediate frequency amplifier 47, a data demodulation circuit 21 for demodulating data included in the signal, a phase detection circuit 22 for detecting the phase of the signal, and a data processing circuit 17 for processing the demodulated signal.

The selection circuit 48 includes a frequency synthesizer and a CPU, and switches the frequency of the local oscillator 16 by selecting a frequency based on the output signals of the first level detection circuit 201 and the second level detection circuit 202. The first level detection circuit 201 demodulates an amplitude modulation component included in a radio wave and a beacon radio wave of the automatic toll collection system, and detects a level of a radio wave or a beacon radio wave of the automatic toll collection system based on the amplitude modulation component. , A detector 201a, a band-pass filter 201b for extracting a 1 kHz amplitude modulation component included in the beacon radio wave, a comparator 201c for comparing the level of this signal with a reference value, and a radio wave of the automatic toll collection system. It has a band-pass filter 201d for extracting an amplitude modulation component of 1 MHz, and a comparator 201e for comparing the level of this signal with a reference value. This is to check if you are in the area.

The comparator 201 of the first level detection circuit 201
When the output signal of “c” is input to the selection circuit 48, the selection circuit 48 sends a signal for switching the frequency of the local oscillator 16 to a frequency corresponding to the frequency of the roadside beacon, and outputs the signal of the comparator 201 e of the first level detection circuit 201. When the output signal is input to the selection circuit 48, the selection circuit 48 sends a signal for switching the frequency of the local oscillator 16 to a frequency corresponding to the frequency of the automatic toll collection system.

When there are no output signals, the first
Only the level detection circuit 201 and the data processing circuit 17 are operated, and the other circuits (the transmission circuit 26, the local oscillator 1
6. It is preferable that the power of the mixer 46, the intermediate frequency amplifier 47, the second level detection circuit 202, the data demodulation circuit 21, the phase detection circuit 22 for detecting the phase of the signal, and the selection circuit 48) is always off. According to this, the first
By turning on the power of other circuits when the data processing circuit 17 recognizes that the level detection circuit 201 has been operated, ordinary power consumption can be reduced.

The second level detection circuit 202 directly detects the level of the beacon radio wave and compares it with the reference level. In this embodiment, when the frequency of the local oscillator 16 is switched to the frequency corresponding to the signal of the ETC, the selection circuit 48 outputs the first level detection circuit 20.
When the frequency of the local oscillator 16 is switched to the frequency corresponding to the signal of the roadside beacon in response to the output signal of No. 1, the logic characteristic is such that it responds only to the decrease of the output signal of the second level detection circuit 202. .
This operation is the same as that described above with reference to the flowchart (FIG. 8), and thus the description is omitted.

FIG. 14 is a block diagram showing still another specific configuration. The in-vehicle terminal device 10 of FIG.
The antenna unit 11 is connected to coaxial cables 42 and 43 and a signal line 52. The antenna unit 11 includes a beacon antenna 11b and an ETC antenna 11c in the form of a printed antenna on a single board, and includes a switching circuit 23 for switching transmission and reception of ETC signals, band-pass filters 18 and 24 for a wide band, and a hybrid 41 on the same board. It is formed above.

The on-vehicle terminal device 10 changes the frequency of the local oscillation circuit using the selection circuit 48, and thus shares the mixer 46 and the intermediate frequency amplifiers 27 and 47. Further, a first level detection circuit 201 is provided. More specifically, the in-vehicle terminal device 10 is roughly divided into a signal processing system including a selection circuit 48 and a first level detection circuit 201, as shown in FIG.

The signal processing system includes a broadband amplifier 44 for amplifying a signal (a signal from a tollgate antenna unit or a beacon signal) input from the coaxial cable 42, a hybrid 45, a mixer 46, a narrow band intermediate frequency filter 2
7, an intermediate frequency amplifier 47, a data demodulation circuit 21, and a data processing circuit 17 for processing a demodulated signal.

The selection circuit 48 includes the first level detection circuit 20
By selecting the frequency based on the output signal of
The frequency of the local oscillator 16 is switched. The first level detection circuit 201 demodulates the amplitude modulation component included in the radio wave of the automatic toll collection system, and detects the level of the radio wave of the automatic toll collection system based on the amplitude modulation component. A band-pass filter 201d for extracting a 1-MHz amplitude modulation component included in the ETC radio wave, and a comparator 201e for comparing the level of this signal with a reference value, whereby the vehicle enters the area of the automatic toll collection system. Is to check if it is.

The comparator 201 of the first level detection circuit 201
When the output signal of e is input to the selection circuit 48, the selection circuit 48 sends a signal for switching the frequency of the local oscillator 16 to a frequency corresponding to the frequency of the automatic toll collection system. As described above, the beacon signal is normally received, but when the vehicle enters the service area of the automatic toll collection system, the signal becomes an ETC reception signal.

As described above, one data processing circuit 17 can preferentially process either the ETC radio wave or the beacon radio wave and supply it to the navigation controller 31. <Modification> In the above embodiment, the selection circuit 48 has a time limit characteristic of switching the local oscillation signal only when the state where the radio wave level is higher or lower than the reference level continues for a certain period of time. May be.

[0096] Such a time limit characteristic can be obtained by using the on-board terminal device 10.
This is realized by a timer (not shown) provided in the system. Thus, it is possible to prevent the switching circuit from malfunctioning due to the instantaneous decrease in the radio wave level. The switching from the beacon to the GPS is slightly delayed due to the time limit characteristic. However, since any position where the GPS positioning satellite can be seen can be detected immediately, there is no major problem in position detection.

[0097]

As described above, according to the first aspect of the present invention, the provision of the level detection circuit and the selection control circuit makes it possible to deal with three radio waves. The amplifying unit can be shared, and downsizing and cost reduction can be achieved.

According to the second aspect of the present invention, the presence of a radio wave can be reliably detected based on the amplitude modulation components of the transmission signals of the ETC radio wave and the beacon radio wave without being affected by noise. According to the third aspect of the present invention, when the local oscillation signal corresponding to the radio wave of the roadside beacon is selected, it is possible to determine whether or not the vehicle is out of the range of the roadside beacon.

According to the fourth aspect of the present invention, the provision of the level detection circuit and the selection control circuit makes it possible to cope with two radio waves of ETC and GPS. Can be standardized,
The size and cost can be reduced. According to the fifth aspect of the present invention, the presence of a radio wave can be reliably detected based on the amplitude modulation component of the ETC radio wave without being affected by noise.

According to the sixth aspect of the present invention, the provision of the level detection circuit and the selection control circuit makes it possible to cope with the two radio waves of the ETC and the roadside beacon. The parts can be shared, and downsizing and cost reduction can be achieved. According to the present invention as set forth in claim 7, the presence of a radio wave is determined based on the amplitude modulation component of the transmission signal of the ETC radio wave and the beacon radio wave.
Detection can be performed reliably without being affected by noise.

According to the present invention, when a local oscillation signal corresponding to the radio wave of the roadside beacon is selected,
The determination as to whether or not the vehicle has left the range of the roadside beacon can be made without fail. According to the ninth aspect of the present invention, by providing the level detection circuit and the selection control circuit,
Since it is possible to cope with two radio waves, the intermediate frequency amplifying unit after the conversion circuit can be used in common, so that downsizing and cost reduction can be achieved.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a road-vehicle communication system at a tollgate on a toll road.

FIG. 2 is a diagram illustrating an outline of a roadside beacon communication system.

FIG. 3 is a graph showing a reception level of a radio wave of a roadside beacon.

FIG. 4 is a block diagram showing an in-vehicle device incorporating the in-vehicle terminal device of the present invention.

FIG. 5 is a diagram showing an example of installation of each antenna in a vehicle.

FIG. 6 is an internal block diagram showing an in-vehicle terminal device including four processing systems: a GPS signal processing system, a beacon signal processing system, an ETC signal processing system, and a signal processing system.

FIG. 7 is a block diagram showing a more specific circuit configuration of the vehicle-mounted terminal device of FIG. 6;

FIG. 8 is a flowchart illustrating a response operation of the selection circuit.

FIG. 9 is a block diagram illustrating a circuit configuration according to another embodiment in which a detector is provided in an antenna unit 11.

FIG. 10 is an internal block diagram showing an in-vehicle terminal device including three processing systems of a GPS signal processing system, an ETC signal processing system, and a signal processing system.

11 is a block diagram showing a more specific circuit configuration of the vehicle-mounted terminal device shown in FIG.

FIG. 12 is an internal block diagram showing an in-vehicle terminal device including three processing systems of a beacon signal processing system, an ETC signal processing system, and a signal processing system.

FIG. 13 is a block diagram showing a more specific configuration of the in-vehicle terminal device of FIG.

14 is a block diagram showing still another specific configuration of the vehicle-mounted terminal device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 On-board terminal device 11 Antenna part 11a GPS antenna 11b Beacon antenna 11c ETC antenna 15 Mixer 16 Local oscillator 17 Data processing circuit 20 Level detection circuit 23 Switching circuit 48 Selection circuit 51 Detector 201 First level detection circuit 202 Second level detection circuit

Claims (11)

[Claims] 1. A terminal device mounted on a vehicle and used for receiving a radio wave radiated from a roadside automatic toll collection system installed at a tollgate; and a terminal device installed on a road. A second receiving circuit for receiving a radio wave radiated from a roadside beacon; a third receiving circuit for receiving a radiowave from a GPS positioning satellite; a radio wave for an automatic toll collection system;
A conversion circuit for converting each radio wave of the PS positioning satellite into an intermediate frequency; and a local circuit capable of supplying a local oscillation signal corresponding to the radio wave of the automatic toll collection system, the radio wave of the roadside beacon, or the radio wave of the GPS positioning satellite to the conversion circuit. An oscillation circuit, a data processing circuit, a radio wave of the automatic toll collection system, a level detection circuit for detecting a radio wave level of the roadside beacon, respectively, and the level detection circuit determines that the level of the radio wave of the automatic toll collection system is higher than a reference value. If determined, select a local oscillation signal according to the radio wave of the automatic toll collection system,
When it is determined that the radio wave level of the roadside beacon is higher than the reference value, a local oscillation signal corresponding to the radio wave of the roadside beacon is selected. And a selection control circuit for selecting a signal. 2. The level detection circuit demodulates an amplitude modulation component of a constant frequency included in a radio wave of an automatic toll collection system and a radio wave of a roadside beacon, and based on the amplitude modulation component, a radio wave and a roadside of the automatic toll collection system. The in-vehicle terminal device according to claim 1, wherein the in-vehicle terminal device detects a level of a radio wave of a beacon. 3. The level detection circuit according to claim 1, wherein the second level detection circuit directly detects a level of a radio wave of the roadside beacon, and demodulates an amplitude modulation component included in a radio wave of the automatic toll collection system and a radio wave of the roadside beacon. A first level detection circuit for detecting a level of a radio wave of the automatic toll collection system and a radio wave of the roadside beacon based on the amplitude modulation component, wherein the selection control circuit is configured to detect a level of the radio wave based on an output of the first level detection circuit. When it is determined that the level of the radio wave of the roadside beacon has become larger than the reference value, the local oscillation signal corresponding to the radiowave of the roadside beacon is selected, and the local oscillation signal corresponding to the radiowave of the roadside beacon is selected. When the second level detecting circuit determines that the level of the radio wave of the roadside beacon has become smaller than the reference value, it switches to a local oscillation signal corresponding to the radio wave of the GPS positioning satellite. Vehicle terminal according to claim 1, characterized in that obtaining those. 4. A terminal device mounted and used in a vehicle, comprising: a first receiving circuit for receiving a radio wave radiated from a roadside automatic toll collection system installed at a tollgate; A third receiving circuit for receiving radio waves, a conversion circuit for converting the radio waves of the automatic toll collection system and the radio waves of the GPS positioning satellite to intermediate frequencies, respectively;
A local oscillation circuit capable of supplying a local oscillation signal corresponding to a positioning satellite radio wave, a data processing circuit, a level detection circuit for detecting a radio wave level of the automatic toll collection system, and an automatic toll collection by the level detection circuit When it is determined that the level of the radio wave of the system is higher than the reference value, a local oscillation signal corresponding to the radio wave of the automatic toll collection system is selected,
An on-board terminal device comprising: a selection control circuit for selecting a local oscillation signal according to a radio wave of a GPS positioning satellite when it is determined that a radio wave level of the automatic toll collection system is lower than a reference value. 5. The level detecting circuit demodulates an amplitude modulation component of a constant frequency included in the radio wave of the automatic toll collection system, and detects the level of the radio wave of the automatic toll collection system based on the amplitude modulation component. The in-vehicle terminal device according to claim 4, wherein 6. A terminal device mounted on a vehicle and used for receiving a radio wave radiated from a roadside automatic toll collection system installed at a tollgate; and a terminal device installed on the road. A second receiving circuit that receives a radio wave radiated from the roadside beacon; a conversion circuit that converts the radio wave of the automatic toll collection system and a radio wave of the roadside beacon to an intermediate frequency, respectively; Or a local oscillation circuit capable of supplying a local oscillation signal corresponding to the radio wave of the roadside beacon, a data processing circuit, a radio wave of the automatic toll collection system, a level detection circuit for detecting the level of the radio wave of the roadside beacon, respectively, If the level detection circuit determines that the level of the radio wave of the automatic toll collection system is higher than the reference value, Select the local oscillation signal according to
When it is determined that the radio wave level of the roadside beacon is higher than the reference value, a local oscillation signal corresponding to the radio wave of the roadside beacon is selected. A selection control circuit for selecting a signal or not selecting any of the local oscillation signals. 7. The level detection circuit demodulates an amplitude modulation component of a constant frequency included in the radio wave of the automatic toll collection system and the radio wave of the roadside beacon, and based on the amplitude modulation component, the radio wave and the roadside of the automatic toll collection system. 7. The in-vehicle terminal device according to claim 6, wherein a level of a radio wave of the beacon is detected. 8. The level detection circuit, wherein a second level detection circuit for directly detecting the level of the radio wave of the roadside beacon, and an amplitude modulation component included in the radio wave of the automatic toll collection system and the radio wave of the roadside beacon, A first level detection circuit for detecting a level of a radio wave of the automatic toll collection system and a radio wave of the roadside beacon based on the amplitude modulation component, wherein the selection control circuit is configured to detect a level of the radio wave based on an output of the first level detection circuit. When it is determined that the level of the radio wave of the roadside beacon has become larger than the reference value, the local oscillation signal corresponding to the radiowave of the roadside beacon is selected, and the local oscillation signal corresponding to the radiowave of the roadside beacon is selected. When the second level detection circuit determines that the level of the radio wave of the roadside beacon has become smaller than the reference value, the local oscillation signal corresponding to the radio wave of the automatic toll collection system Switch or any of the local oscillation signal to be in-vehicle terminal according to claim 6, characterized in that is not selected. 9. A terminal device mounted on a vehicle and used for receiving a radio wave radiated from a roadside automatic toll collection system installed at a tollgate, and a terminal device installed on the road. A second receiving circuit for receiving a radio wave radiated from the roadside beacon, a conversion circuit for converting the radio wave of the automatic toll collection system and a radio wave of the roadside beacon to an intermediate frequency, respectively, Or, a local oscillation circuit capable of supplying a local oscillation signal corresponding to the radio wave of the roadside beacon, a data processing circuit, a level detection circuit for detecting a radio wave level of the automatic toll collection system, and an automatic charge by the level detection circuit. If it is determined that the radio wave level of the toll collection system is higher than the reference value, a local oscillation signal corresponding to the radio wave of the automatic toll collection system is selected. ,
An on-vehicle terminal device comprising: a selection control circuit that selects a local oscillation signal according to a radio wave of a roadside beacon when it is determined that a radio wave level of the automatic toll collection system is lower than a reference value. 10. The level detecting circuit demodulates an amplitude modulation component of a constant frequency included in a radio wave of the automatic toll collection system, and detects a level of a radio wave of the automatic toll collection system based on the amplitude modulation component. The in-vehicle terminal device according to claim 9. 11. The selection control circuit according to claim 1, wherein the selection control circuit selects the local oscillation signal only when the state where the level of the radio wave becomes higher or lower than the reference value continues for a predetermined time. An in-vehicle terminal device according to any one of the above.