JPH04240925A - Beacon receiver - Google Patents

Abstract

PURPOSE:To obtain an excellent reception output without arranging an antenna onto a roof. CONSTITUTION:A front antenna 10 and a rear antenna 12 are provided for use switchingly in response to the reception output. Without arrangement of the antennas on the roof, a reception output always exceeding a prescribed value is obtained, The beautiful appearance of the roof is attained and no countermeasure for leaking of rain is required.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beacon receiving device used in a road-to-vehicle information communication system, which receives radio waves transmitted from a beacon station on a moving vehicle.

0002

2. Description of the Related Art Road-to-vehicle information communication systems have been known. This system is a system in which a sign post is installed on the roadside, and a vehicle receives radio waves (beacon) transmitted by a roadside transmitter (beacon station) installed at the post. The transmitted and received radio waves convey information indicating, for example, road congestion. Therefore, by using this system, vehicle operators and the like can obtain information useful for driving, and safe and smooth vehicle and traffic operations can be realized.

In the road-to-vehicle information communication system, a beacon receiving device is mounted on the vehicle because it is necessary to receive radio waves. This device receives radio waves from a beacon station, demodulates the digitally modulated received signal, and obtains necessary information. The obtained information is displayed on the front panel of the vehicle for use by the driver, or provided to the vehicle's steering control system.
This information is treated as the basis for vehicle steering control.

[0004] As described above, in the conventional road-to-vehicle information communication system, the vehicle acquires information useful in the operation of the vehicle by receiving radio waves from the beacon station.

[0005]

However, in the conventional beacon receiving apparatus, there is a problem in that when attempting to receive radio waves from a beacon station in a suitable manner, the aesthetic appearance of the vehicle is spoiled. This problem is caused by the fact that the beacon receiving device conventionally has only one receiving antenna. That is, especially in a situation where the vehicle is far from the beacon station, when trying to ensure suitable reception of radio waves from the beacon station, it is preferable to install the receiving antenna on the roof of the vehicle. The roof of the vehicle provides the best view of the vehicle, and therefore, if the reception antenna is placed there, radio waves from the beacon station can be received most optimally. However, the appearance of the vicinity of the roof of a vehicle has a large influence on the aesthetic appearance of the vehicle. A vehicle design in which a receiving antenna protrudes from the roof is generally not considered aesthetically pleasing.

[0006] Furthermore, the arrangement of the receiving antenna on the roof poses an obstacle to lowering the price. That is, if the receiving antenna is placed on the roof, the receiving antenna is exposed to rain during rain. Therefore, it is necessary to take measures to prevent rainwater from entering the vehicle interior through the inlet for introducing the signal cable connected to the reception antenna into the vehicle interior. Adding a structure to prevent rainwater from entering results in new parts costs and manufacturing costs.

[0007] The present invention has been made with the aim of solving these problems, and while ensuring reception performance, the receiving antenna is not placed on the roof, and therefore the aesthetic appearance of the vehicle is improved. The purpose of the present invention is to provide a beacon receiving device that is secure and does not require rainwater countermeasures.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a front antenna having directivity toward the front of the vehicle, a rear antenna having directivity toward the rear of the vehicle, and a signal received by the rear antenna. The front antenna is selected when the strength is less than a predetermined value and the signal strength received by the front antenna exceeds a predetermined value, and the signal strength received by the front antenna is less than a predetermined value and the signal strength received by the rear antenna is a predetermined value. means for selecting the rear antenna when the value exceeds the value, means for storing the selected antenna, and performing predetermined processing such as demodulation on the output of the currently selected antenna among the front antenna and the rear antenna. The beacon station is equipped with a receiving means that outputs information wirelessly transmitted from the beacon station, and a receiving strength determiner that determines whether the received signal strength is equal to or higher than a predetermined value based on the output of the receiving means, and receives radio waves transmitted from the beacon station. It is characterized by diversity reception.

[0009]

In the present invention, the outputs of the front antenna and the rear antenna are selected according to predetermined conditions, and the output of the receiving means related to the output of the selected antenna is used for information output. Here, the selection of the antenna is performed as follows. That is, when the received signal strength from the front antenna is strong and exceeds a predetermined value, the front antenna is selected, and when the received signal strength from the rear antenna is strong and exceeds the predetermined value, the rear antenna is selected. However, if the currently selected antenna has a received signal strength that exceeds the specified value,
Even if the received signal strength exceeding the predetermined value is obtained by another antenna, there is no need to perform a new selection of the antenna. Therefore, only when the received signal strength is below a predetermined value is the selection of changing to another antenna performed.

Therefore, in the present invention, a received signal strength always exceeding a predetermined value can be obtained, and suitable beacon reception can be realized. For example, when a vehicle equipped with the device of the present invention approaches a beacon station, the strength of the received signal from the front antenna increases first, so the front antenna is selected. As the vehicle passes in front of the beacon station, at some point the strength of the signal received by the forward antenna begins to decrease. When the received signal strength falls below a predetermined value, a determination is made regarding the received signal strength by the rear antenna, and when the received signal strength exceeds the predetermined value, the rear antenna is selected. In this way, as the vehicle approaches and passes the beacon station, a received signal strength that always exceeds a predetermined value is ensured.

[0011] The receiving signal strength securing effect in the present invention is as follows:
Regarding the arrangement of the antenna, it is unnecessary to arrange it on the roof of the vehicle. That is, sufficient received signal strength can be obtained without placing the antenna on the roof. In addition, since each antenna has directivity toward the front or rear of the vehicle,
There is no reduction in reception strength related to information acquisition due to shielding by the vehicle body.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a beacon receiving device mounted on a vehicle according to an embodiment of the present invention. The device shown in this figure includes two antennas, a front antenna 10 having a directivity toward the front of the vehicle, and a rear antenna 12 having a directivity toward the rear of the vehicle. These antennas 10 and 12 are both connected to a reception demodulator 16 via an antenna switch 14. That is, in this embodiment, by switching the antenna switch 14,
One of the antennas 10 and 12 is selectively used.

The reception demodulator 16 demodulates the antenna 10 or 12 output (beacon signal) supplied via the antenna switch 14. The reception demodulator 16 performs predetermined processing on this signal, extracts and outputs traffic information. Here, traffic information is information transmitted by a beacon signal from a beacon station. The traffic information is output to the traffic information display 18 and displayed. The traffic information display 18 is an LCD, C
It is a display device such as RT, and therefore traffic information is given to the driver of the vehicle in the form of characters, graphics, etc. A driver or the like executes necessary vehicle operation according to the displayed information. In this embodiment, traffic information is used only for vehicle operation, but it may also be supplied to a vehicle steering control device or the like.

The reception demodulator 16 is connected to a traffic information display 18 as well as a reception strength determiner 20. The reception strength determiner 20 takes in the amplitude of the beacon signal from the reception demodulator 16 as the reception signal strength, and executes a predetermined threshold determination. That is, the reception output e1 of the front antenna 10 or the reception output e2 of the rear antenna 12 is set to a predetermined threshold value TH.
is exceeded based on the received signal strength of each antenna 10 or 12. If the reception output e1 or reception output e2 exceeds the threshold TH, the reception strength determiner 20 outputs "1", and otherwise outputs "0".
The output of the reception strength determiner 20 is taken into the antenna number storage controller 22.

The antenna number storage controller 22 has a storage capacity of at least 1 bit. If the stored information is "0", the antenna number storage controller 22 controls the antenna switch 14 to switch the forward antenna 10 to the reception demodulator 16.
Connect to. Conversely, if the stored information is "1", the antenna number storage controller 22 controls the antenna switch 14 to connect the rear antenna 10 to the reception demodulator 16.

The antenna number storage controller 22 maintains the stored content when the output of the reception strength determiner 20 is "1",
If it is "0", the stored contents are inverted. Therefore, the reception output e1 or e2 exceeds the predetermined threshold TH by the antenna 10 or 12 currently connected to the reception demodulator 16.
If this is obtained, the state of the antenna switch 14 is maintained, and reception by the currently used antenna 10 or 12 is continued. If the threshold value TH is not exceeded, the antenna switching device 14 is sequentially inverted and switched in accordance with the operating clock of the antenna number storage controller 22. As a result, at the time of switching, the reception output e1 or e2 exceeds the threshold TH by the other antenna 10 or 12.
is obtained, the antenna 10 of the other party is newly obtained.
or 12 is subsequently performed.

The characteristic operation of this embodiment is the selection switching operation of the antennas 10 and 12, as shown in the flowchart in FIG.

First, when the apparatus of this embodiment starts operating by turning on the power or the like (100), a selection operation 102 of the front antenna 10 is executed. When the front antenna 10 is selected, determination 104 is first performed. Determination 104 is a determination as to whether or not the received output of the front antenna 10 exceeds the threshold value TH, and is executed by the received strength determiner 20 as a determination of received signal strength. If it exceeds, the reception strength determiner 20 outputs "1", so that the stored contents of the antenna number storage controller 22 are maintained. That is, the process returns to step 102.

If it is determined in the determination 104 that the received strength has not been exceeded, that is, if the reception strength determiner 20 outputs "0", the contents stored in the antenna number storage controller 22 are inverted. That is, the antenna switch 14 is switched by the antenna number storage controller 22 so that the rear antenna 12 is selected (106).

When the rear antenna 12 is selected, a determination operation similar to step 104 is performed for the rear antenna 12 (108). In judgment 108, the rear antenna 12
If it is determined that sufficient receiving output cannot be obtained by
The process moves to step 102. Therefore, the antenna 10 or 1
2, at the moment when the received output e1 or e2 exceeding the threshold TH cannot be obtained, the other antenna 12 or 1
If the reception output e1 or e2 exceeding the threshold value TH is obtained by 0, the antenna 10 or 12 is switched, and if not, the antenna switch 14 is switched alternately to standby.

FIG. 3 shows changes in the received outputs e1 and e2 of the antennas 10 and 12 and the threshold value TH when a vehicle C equipped with the device according to this embodiment passes through the front P0 of the antenna B of the beacon station. The relationship between

As shown in this figure, the electric field strength E of the beacon signal transmitted from the antenna B of the beacon station is:
It has a maximum value at the front P0 of the antenna B. In this embodiment, since the antenna 10 has a directivity in front of the vehicle C, and the antenna 12 has a directivity in the rear of the vehicle C, the reception outputs e1 and e of each antenna 10 and 12 are
2 has a maximum value before and after the front P0. Therefore, the sections in which e1 and e2 exceed the threshold TH are different, and the section for the received power e1 of the antenna 10 arrives before the section for the received power e2 of the antenna 12.

In this embodiment, the antennas 10 and 12 are used alternately according to the operation described above with reference to FIG. Therefore, the received output e1 of the antenna 10 is the threshold value TH
Before reaching (~P1), the antennas 10 and 12 are alternately switched. Next, the reception output e1 of the antenna 10
In the section (P1 to P2) after reaching the threshold value TH until it becomes less than the threshold value TH again, the front antenna 10
is used. At point P2, the content of the antenna number storage controller 22 becomes "0" instantly, and the rear antenna 12
The switch to is executed. At this time, the rear antenna 12
has a received output e2 that exceeds the threshold TH, so
After this, the reception output e2 of the rear antenna 12 becomes the threshold value TH.
The rear antenna 12 is used in the following sections (P2 to P3). When reaching point P3, the process shifts to the same standby operation as before point P1. Note that in the switching control operation by the antenna number storage controller 22, a waiting time may be provided in order to avoid antenna switching operations that are sensitive to instantaneous interruptions in beacon signals, etc.

[0025]

[Effects of the Invention] As explained above, according to the present invention,
Two types of antennas, front and rear, are provided and are selectively used depending on the strength of the received signal, so that it is possible to secure a predetermined strength of the received signal without placing the antenna on the roof of the vehicle. This makes it possible to maintain the beauty of the vehicle and eliminate the need for rain leakage measures. Further, even if the radio waves from the beacon station are blocked by the vehicle body when viewed from one antenna, suitable reception using the other antenna is possible. As a result, an inexpensive and high-performance device is obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a beacon receiving device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of this embodiment.

FIG. 3 is a diagram showing the relationship between received output change and threshold value in this embodiment.

[Explanation of symbols]

10 Forward aerial 12 Rear aerial 14　Antenna switcher 16 Reception demodulator 20 Reception strength determiner 22 Antenna number storage controller e1 Front antenna reception output e2 Reception output of rear antenna TH threshold

Claims (1)

[Claims] Claim 1: A forward antenna having directivity in front of the vehicle;
The rear antenna has directivity toward the rear of the vehicle, and when the received signal strength from the rear antenna is less than a predetermined value and the received signal strength from the front antenna exceeds a predetermined value, the front antenna is selected, and the received signal from the front antenna is means for selecting the rear antenna when the strength of the signal received by the rear antenna is below a predetermined value and the strength of the received signal from the rear antenna exceeds the predetermined value; a means for storing the selected antenna; Receiving means for performing predetermined processing such as demodulation on the output of the selected antenna and outputting information wirelessly transmitted from the roadside transmitting device; and determining whether the received signal strength is equal to or greater than a predetermined value based on the output of the receiving means. What is claimed is: 1. A beacon receiving device comprising: a receiving strength determiner for performing diversity reception of radio waves transmitted from a roadside transmitting device.