JP2817514B2 - Beacon receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beacon receiver for receiving radio waves radiated from a roadside transmitter of a road traffic information communication system (VICS).

[0002]

2. Description of the Related Art There is known a beacon receiver which receives a radio wave from a beacon transmitter installed along a road to obtain position information and road information (for example, Japanese Patent Laid-Open No. Hei 2
-71400). As the position information in the VICS, an amplitude inverse modulation method is considered. As shown in FIG. 5, a normal-phase transmission wave and a negative-phase transmission wave are radiated from a beacon transmission antenna. The beacon receiver detects the phase of the amplitude modulation component of the received signal, determines the position where the phase has changed as the position immediately below the beacon transmitter, corrects the current position of the vehicle, and moves the vehicle from the normal phase region to the reverse position. The information corresponding to the traveling direction of the vehicle is extracted from the road information and provided to the occupant depending on whether the vehicle has moved to the phase region or from the reverse region to the normal region.

[0003]

However, the signal level of the transmission wave actually radiated from the beacon transmitter is shown in FIG.
As shown in FIG. 6, it does not have an ideal characteristic such that a dip point at which the signal level sharply drops exists immediately below the transmitter, and as shown in FIG. 6, a width of about ± 5 m immediately below the transmitter. There is a region where the signal level of the transmitted wave is very unstable. This area is usually called a gray zone, and the phase of the transmitted wave cannot be accurately detected in the gray zone.

However, the conventional beacon receiver detects how the phase of the transmission wave radiated from the beacon transmitter has changed and determines the traveling direction of the vehicle. If the vehicle passes through the gray zone immediately below at a low speed, correct phase detection is not performed, and there is a possibility that the determination of the traveling direction may be erroneous.

This will be described in more detail with reference to FIG. Now, assuming that the vehicle is traveling at a low speed from the in-phase region immediately below the beacon transmitter to the anti-phase region, first, in the beacon receiver, the reception level of the in-phase transmission wave exceeds the threshold Th,
The positive-phase transmission wave is detected thereafter as the vehicle advances, and it is determined that the vehicle is traveling in the positive-phase region. However, when the vehicle reaches the gray zone immediately below the transmitter, the phase cannot be detected, and the previously determined normal phase region is canceled. However, in the gray zone, for example, when the vehicle reaches the position P1, the signal level of the negative-phase transmission wave exceeds the threshold Th, and the negative-phase transmission wave is still detected since the vehicle is traveling at a low speed. It is determined that the vehicle is traveling in the reverse phase region. Next, when the signal level of the negative-phase transmission wave decreases when the vehicle reaches the position P2 and a positive-phase transmission wave is detected instead, it is determined that the phase has switched from the negative phase to the normal phase. In other words, it is determined that the vehicle is actually traveling from the reverse phase region to the normal phase region although the vehicle is actually traveling from the normal phase region to the reverse phase region.

It is an object of the present invention to provide a beacon receiver which accurately detects the traveling direction of a vehicle and displays information corresponding to the traveling direction from various road information.

[0007]

Means for Solving the Problems The present invention will be described with reference to FIG. 1 which is a claim correspondence diagram. The present invention relates to a receiving means 100 for receiving a beacon signal radio wave containing various information.
Phase detecting means 101 for detecting the phase of the amplitude modulation component from the beacon signal received by the receiving means 100
A traveling direction determining means 102 for determining the traveling direction of the vehicle based on the detected phase of the phase detecting means 101; and a traveling direction determined by the traveling direction determining means 102 from the various information received by the receiving means 100. The present invention is applied to a beacon receiver including extraction means 103 for extracting corresponding information and display means 104 for displaying the information extracted by the extraction means 103. And in order to achieve the above purpose,
If a plurality of successive detection phases by the phase detection means 101 are the same, a phase determination means 105 for determining the phase is determined.
And when the phase is not detected by the phase detecting means 101 after the phase is determined by the phase determining means 105, there is provided a distance measuring means 106 for measuring a traveling distance of the vehicle from that point. Means 106
Before the predetermined traveling distance is measured by the phase detecting means 101
If a phase opposite to the determined phase is detected, the traveling direction of the vehicle is determined based on the determined phase.

[0008]

If the detected phase is the same for a plurality of successive detections, the phase is determined. After that, from the point where the phase is not detected by the phase detecting means 101, the determined phase is determined before the vehicle travels a predetermined distance. When the opposite phase is detected, the traveling direction of the vehicle is determined based on the determined phase. by this,
The traveling direction of the vehicle is accurately detected.

[0009]

An embodiment of the present invention will be described with reference to FIGS. FIG. 2 shows the configuration of one embodiment. In the figure, an antenna 1 is installed in a rear parcel or the like of a vehicle and receives a radio wave radiated from a beacon transmitter. Amplifier 2 amplifies the signal received by antenna 1 and outputs it to data demodulator 3, modulated signal demodulator 4, and level determiner 5. The data demodulator 3 demodulates the first modulated wave signal generated by the beacon transmitter. The first modulated wave signal is obtained by amplitude-modulating, frequency-modulating, or phase-modulating a carrier with a transmission data frame. Synchronous detector 6
Detects the element synchronization or the frame synchronization, restores the transmission data, and outputs the data to the microcomputer (hereinafter referred to as CPU) 7 and the modulation signal reproducer 8. The modulated signal regenerator 8 regenerates the amplitude modulated signal used when the beacon transmitter generates the second modulated wave signal, based on the received data frame and the frame synchronization signal based on the received data frame. The second modulated wave signal is obtained by performing positive-phase or reverse-phase amplitude modulation on the first modulated wave signal. The configuration of the beacon transmitter for transmitting position information by the amplitude inverse modulation method and the method of modulating the transmission wave are known in the above-mentioned Japanese Patent Application Laid-Open No. 2-71400, and the description thereof is omitted here.

The modulation signal demodulator 4 demodulates the second modulation wave signal and extracts an amplitude modulation signal. The phase comparator 9 compares the phase of the amplitude modulation signal extracted by the modulation signal demodulator 4 with the phase of the amplitude modulation signal reproduced by the modulation signal regenerator 8. Is determined, and
If the phase is inverted by 180 degrees, it is determined that the transmission wave is an inverted transmission wave. Level determiner 9 outputs a control signal to CPU 7 when the signal level of the received signal amplified by amplifier 2 exceeds threshold value Th. The vehicle speed sensor 10 generates a pulse signal every predetermined traveling distance of the vehicle, and the counter 11
Vehicle speed sensor 1 based on the count control signal from U7
The pulse signal of 0 is counted, and the traveling distance of the vehicle is detected. The CPU 7 controls each component device of the beacon receiver described above, detects a traveling direction of the vehicle by executing a control program described later, and detects the traveling direction from various reception data read from the synchronization detector 6. The data such as road information and traffic information corresponding to the information is extracted and displayed on the display unit 12.

FIGS. 3 and 4 are flowcharts showing a control program executed by the CPU 7. The operation of the embodiment will be described with reference to this flowchart. When the main switch (not shown) is turned on, the CPU 7 starts executing the control program, and in step S1, the level determination unit 5 determines whether the reception level has exceeded a preset threshold Th. If it is determined that the reception level has exceeded the threshold value Th, the process proceeds to step S2, and a timer built in the CPU 7 is started. This timer measures the time from when the received signal first exceeds the threshold Th. Here, the threshold value Th may be set to a signal level that allows a phase comparison. In step S3, the phase of the received signal is detected and stored by the phase comparator 9, and in the following step S4, the received signal level is still at the threshold T.
h is determined, and if it exceeds the threshold Th, the process proceeds to step S5; otherwise, the process proceeds to step S5.
Return to 1.

In step S5, it is determined whether or not the timer has expired, that is, whether or not a preset time T1 has elapsed since the received signal first exceeded the threshold value Th. Go to step S3, otherwise return to step S3. In step S6, it is determined whether or not the phases of the reception signals repeatedly detected during the set time T1 after the reception signal first exceeds the threshold Th are all the same. Otherwise, return to step S1. In step S7, the phase that is repeatedly detected during the set time T1 is determined. As shown in FIG. It is judged that it is in the area.

Next, in step S8, it is determined whether or not the vehicle has reached the gray zone and the phase comparator 9 cannot detect the phase.
Proceed to. In step S9, the counting of the counter 11 for detecting the traveling distance is started, and the subsequent step S10
Then, it is determined whether or not the received signal level has exceeded the threshold value Th again. If the received signal level exceeds the threshold value Th again while traveling in the gray zone, the process proceeds to step S11, and the phase of the received signal is detected. Step S1
In step 2, the detected phase is compared with the phase determined in the above-described step to determine whether or not the phase has been inverted. If the phase is inverted, the process proceeds to step S13 in FIG. 4, and if not, the process returns to step S10.

In step S13 of FIG.
It is determined whether or not the vehicle has traveled the preset traveling distance K1. If the traveling of the preset distance K1 has already been completed, the process returns to step S1 in FIG. 3, and otherwise proceeds to step S14. If the phase is reversed before the vehicle has traveled the set distance K1 after reaching the gray zone, step S
At 14, the point where the phase inversion is detected is determined to be immediately below the beacon transmitter, the current position of the vehicle is corrected, and the traveling direction of the vehicle is determined based on the phase determined in the above step. That is, if the deterministic phase is positive, it is determined that the vehicle is progressing from the normal phase to the negative phase, and if the deterministic phase is negative, it is determined that the vehicle is progressing from the negative phase to the normal phase. I do. Here, the set distance K1 is, for example, 10 m. In step S15, data such as road information and traffic information corresponding to the traveling direction of the vehicle is extracted from the received data read from the synchronization detector 6, and in step S16, the extracted road information and traffic information are extracted. Display on the display 12 and FIG.
Return to step S1.

As described above, if the phases detected in a plurality of successive phase detections during the predetermined time T1 are all the same, the phase is determined, and then the vehicle is moved from the point where the phase is no longer detected to the predetermined position. If the phase opposite to the definite phase is detected before the vehicle travels by the distance, the traveling direction of the vehicle is determined based on the definite phase, so that the traveling direction of the vehicle can be accurately detected.

In the above-described embodiment, if the phases repeatedly detected during the set time T1 after the reception signal exceeds the threshold value Th are all the same, the phase is determined. If all the phases repeatedly detected during the travel of the predetermined distance after the reception signal exceeds the threshold value Th are the same, the phase may be determined.

In the configuration of the above embodiment, the antenna 1
Is a receiving means, a data demodulator 3, a modulated signal demodulator 4, a synchronization detector 6, a modulated signal regenerator 8 and a phase comparator 9 are phase detecting means, the microcomputer 7 is a phase determining means, a traveling direction determining means and The extracting means, the vehicle speed sensor 10 and the counter 11 serve as the distance measuring means, and the display 12
Constitute display means.

[0018]

As described above, according to the present invention, if a plurality of consecutive detected phases are the same, the phase is determined, and then the vehicle is detected from the point where the phase is no longer detected by the phase detecting means. If the vehicle detects a phase opposite to the final phase before traveling a predetermined distance, the traveling direction of the vehicle is determined based on the final phase, so that the traveling direction of the vehicle can be accurately detected.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims.

FIG. 2 is a block diagram showing a configuration of one embodiment.

FIG. 3 is a flowchart illustrating an example of a control program executed by the microcomputer.

FIG. 4 is a flowchart showing an example of a control program executed by the microcomputer.

FIG. 5 is a diagram showing signal levels of a normal-phase transmission wave and a negative-phase transmission wave around a beacon transmitter.

FIG. 6 is a diagram illustrating a gray zone immediately below a beacon transmitter.

FIG. 7 is a diagram illustrating erroneous determination of the phase of a conventional beacon receiver in a gray zone.

[Description of Signs] 1 Antenna 2 Amplifier 3 Data Demodulator 4 Modulation Signal Demodulator 5 Level Judgment Device 6 Synchronization Detector 7 Microcomputer (CPU) 8 Modulation Signal Regenerator 9 Phase Comparator 10 Vehicle Speed Sensor 11 Counter 12 Display 100 Receiving means 101 Phase detecting means 102, 102A Traveling direction determining means 103 Extracting means 104 Display means 105 Phase determining means 106 Distance measuring means

Claims (1)

(57) [Claims] A receiving means for receiving a beacon signal radio wave including various information; a phase detecting means for detecting a phase of an amplitude modulation component from the beacon signal received by the receiving means; A traveling direction determining means for determining the traveling direction of the vehicle based on the detected phase; and extracting information corresponding to the traveling direction determined by the traveling direction determining means from the various information received by the receiving means. In a beacon receiver provided with an extracting unit and a display unit for displaying the information extracted by the extracting unit, a phase for determining the phase if a plurality of consecutive detection phases by the phase detecting unit is the same. Determining means for determining the traveling distance of the vehicle from the point when the phase is not detected by the phase detecting means after the phase is determined by the phase determining means. The traveling direction determination means, before a predetermined traveling distance is measured by the distance measuring means, when the phase detection means detects a phase opposite to the final phase, the definite phase A beacon receiver which determines a traveling direction of the vehicle based on the beacon.