JPS63187708A - dual beam antenna - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a dual beam antenna, and more specifically, the present invention relates to a dual beam antenna, and more specifically, to a dual beam antenna installed in a roadside device installed at a predetermined location in a road transportation network and a dual beam antenna installed in a vehicle. The present invention relates to a dual beam antenna that is particularly suitably used in a roadside beacon system that allows data to be exchanged with an on-vehicle device.

<Prior Art> Conventionally, vehicles are equipped with a small computer and a display device, and road map data stored in a storage device such as a compact disk is read out and displayed on the display device, and the data is also read out from a vehicle speed sensor. The vehicle speed data and direction data from the direction sensor are input to calculate the vehicle position at each point in time and determine the running direction.Based on these calculation results and judgment results, the vehicle is displayed on the display device. 2. Description of the Related Art So-called navigation systems have come to be provided in which a display indicating a vehicle is added to a corresponding portion of a road map.

If such a navigation system is used, the current location and traveling direction of the vehicle can be easily identified visually, and the vehicle can be reliably reached the destination without getting lost.

However, in the navigation system with the above configuration, errors that the vehicle speed sensor and direction sensor inevitably have accumulate as the traveling distance increases, and when the traveling distance exceeds a predetermined distance, however, this predetermined distance is (It is determined by the degree of error of the vehicle speed sensor and direction sensor in each vehicle, and fluctuations in the atmospheric conditions at the location of each sensor, etc., and is not necessarily a fixed distance.) The vehicle display position on the display device may be the actual vehicle position. This results in a situation in which the device deviates significantly from its normal state, becomes unable to perform its original function, and becomes lost.

In order to solve these problems, roadside antennas are installed in the road transportation network at predetermined distances that are shorter than the distance at which the cumulative error exceeds a predetermined value, and signals containing various data are transmitted from the roadside antennas. , a so-called roadside beacon emits only in a relatively narrow range, receives the above signal with an antenna attached to the vehicle, imports it into a computer, and calibrates the vehicle's position and driving direction to correct data based on the received signal. It is proposed that the method be adopted.

If such a roadside beacon method is adopted, it is possible to display information based on accurate position data and direction data while the accumulated error is always below a predetermined value, thereby demonstrating the original performance of the navigation system. In particular, by installing roadside antennas in locations where large errors are likely to occur in the direction sensor, such as near railroad tracks or at railroad crossings, errors caused by external factors can be effectively eliminated. It has the advantage of being able to be calibrated.

<Problems to be Solved by the Invention> In the roadside beacon system with the above configuration, signals containing various types of data are constantly radiated by the roadside antenna, which has a fairly high directivity, and the vehicle is not covered by the radiated signal. The roadside antenna transmits and receives signals only when it passes through the area covered by the antenna, and can perform the necessary calibration based on the received signals. There is a problem in that the deviation of the signal receiving position relative to the current position becomes large, making it impossible to achieve a sufficient calibration effect.

To explain in more detail, the basic function of the roadside beacon method is to provide signals containing position data and road direction data to vehicles equipped with a navigation system, but the following functions can also be added to the roadside beacon system. This is required for effective use of the beacon method. In other words, ■ Assist the smooth operation of vehicles by providing the navigation system with additional traffic information such as road congestion, construction, and other road usage conditions around the location where the roadside antenna is installed. , ■ Add detailed map information, including residential locations and personal names, around the locations where roadside antennas are installed.
To make it easier to reach the final destination, ■ By adding road map information covering a fairly wide range, including the locations where roadside antennas are installed, and providing it to the navigation system, the road map displayed on the display device. It is being considered that the system will be updated to provide additional services such as smooth operation to remote areas, and if such additional services are to be provided,
It is essential to expand the transmission band of signals radiated from roadside antennas and to expand the area covered by transmitted and received signals.

As described above, when the transmission area is expanded and the area covered by the received and transmitted signals is expanded, the deviation of the signal reception position from the installation position of the roadside antenna becomes large, and the original purpose is not achieved. A problem arises in that the vehicle position cannot be calibrated accurately due to the influence of the deviation.

In addition, the arrangement of buildings near the location where the roadside antenna is installed and the driving conditions of vehicles in the pond may change significantly over time or depending on the installation location of the roadside antenna, causing radiation from the roadside antenna. As shown in Figure 7, in addition to being directly received by the on-vehicle antenna, the signal is also received by the on-vehicle antenna after being reflected by buildings, road surfaces, other vehicles, etc. Since the signals received through the roadside antenna have different amplitudes and positions, they are summarily or differentially superimposed, and as shown in Figure 8, the intensity distribution of the transmitted signal from the roadside antenna is This results in a signal with an intensity distribution that is significantly different from that of the above-mentioned superimposed signal (a fading phenomenon due to multipath occurs). The signal will have a high-level portion at a location far away from the roadside antenna, and a problem arises in that the vehicle position and traveling direction must be calibrated at the time this portion is detected.

In order to solve this problem, the applicant of this patent has created an antenna plate with the same shape that extends parallel to the ground plate and in opposite directions through a common shorting plate. A patent application has been filed for a dual beam antenna in which feeding points are provided between the antenna plate and the ground plate at symmetrical positions with respect to the mounting and shorting plate (1986).

Patent application dated May 70, title of invention "Antenna").

FIG. 9 and FIG. 10 are diagrams showing the configuration of the dual beam antenna, in which a shorting plate (22) is erected at a predetermined position of the grounding plate (21), and the shorting plate (22) is supported on the upper surface of the shorting plate (22). Antenna plates (23) extending in opposite directions are provided. Then, the coaxial connector (
24) and connect the center conductor (2) of the coaxial connector (24).
4a) is connected to the end of the antenna plate (23). Moreover, a shorting plate (22) for the grounding plate (21)
, and the antenna plate (23) are installed using bolts (25
a), and Natsu (25b).

In the dual beam antenna having the above configuration, by supplying modulated signals through the pair of coaxial connectors (24) while maintaining a predetermined phase relationship, the directivity is determined based on the phase relationship. can emit or receive radio waves.

However, if the dual beam antenna with the above configuration is actually used commercially as a product, the antenna plate (23
) is used with the cover (2B) attached to mechanically and electrically protect it and to improve its appearance, so installing the cover (2B) increases the number of parts. In addition to increasing costs, it becomes difficult to miniaturize the dual beam antenna as a whole, and even though it is necessary to miniaturize the antenna as an in-vehicle antenna, it becomes impossible to achieve sufficient miniaturization. There is a problem.

<Object of the invention> This invention was made in view of the above problems,
It is an object of the present invention to provide a dual beam antenna that can prevent an increase in the number of parts, achieve miniaturization as a whole, and achieve a desired directivity pattern.

(Means for solving the problem) In order to achieve the above object, the dual beam antenna of the present invention connects the ground plate to the ground plate through a common shorting plate.
Antenna plates of the same shape extending in parallel with the ground plate and in opposite directions are attached, and feeding points are provided between the antenna plate and the ground plate at symmetrical positions with the shorting plate as the center, and the connection Either the ground plate or the antenna plate is made of a conductive thin film formed at a predetermined position of the antenna cover.

However, the top surface of the casing containing the power feeding circuit is used as a grounding plate, and a conductive plate is provided at a predetermined position on the antenna cover, and a conductive plate is installed perpendicularly to the top surface on at least a portion of the periphery of the top surface of the casing. It may be made of a transparent thin film.

Further, as the conductive thin film, metal foil, metal vapor deposited film,
It may be made of metal mesh, conductive resin, conductive paint, or metallized fiber.

In the case of a dual beam antenna with the configuration described in (2) below, by feeding signals to both feeding points while maintaining a predetermined phase relationship with each other, the radiation direction determined based on the above phase relationship can be adjusted. can receive radio waves.

To explain in more detail, when signals of the same phase are fed to both feeding points, in a plane perpendicular to the antenna plate, the direction close to the direction perpendicular to the shorting plate is the main radiation 111J.
It is possible to obtain radiation directivity that is almost omnidirectional in a plane parallel to the antenna plate.

Conversely, when signals of opposite phases are fed to both of the feed points, a beam-like radiation directivity can be obtained in the normal direction of the antenna plate.

Therefore, signals that have been modulated using different methods,
By feeding power to both feeding points in a predetermined phase relationship, it is possible to radiate radiation with mutually different directivities.

Similar directivity can be obtained when the dual beam antenna described above is used for reception.

The upper surface of the casing containing the power supply circuit is used as a grounding plate, and a conductor plate is provided perpendicularly to the upper surface of the casing on at least a portion of the periphery of the upper surface of the casing. In the case where the conductor plate is made of a magnetic thin film, the effect of the difference in level between the ground plate and the metal plate can be eliminated by the conductor plate, and better directivity can be obtained.

Furthermore, the same effect as above can be achieved even when the conductive thin film is made of metal foil, metal vapor deposited film, metal mesh, conductive resin, conductive paint, or metallized fiber. can.

<Example> Hereinafter, embodiments will be described in detail with reference to the accompanying drawings showing examples.

FIG. 1 is a perspective view showing an embodiment of the dual beam antenna of the present invention, and FIG. ), and a cover (2) is provided to cover the ground plate (1) from above.

A conductive thin film constituting the antenna plates (3) (4) is provided on the surface of the cover (2) facing the ground plate (1), and the boundary between the antenna plates (G) and (4) and the ground plate. (1) A short circuit board is provided to connect the Furthermore, at a symmetrical position centering on the shorting plate, the antenna plate G
) (4) and the grounding plate (1) is provided with a coaxial connector that constitutes the feed point (■). Furthermore, (5') (6'
) is the feeder line.

The shape of each antenna plate is a square whose negative side is approximately equal to 1/4 wavelength, and the distance between each antenna plate and the ground plate (1), that is, the thickness of the dielectric plate, is equal to the wavelength. It is set to a smaller value compared to the

Further, the conductive thin film may be any film having a certain degree of conductivity, such as a metal foil bonded to a dielectric plate,
A metal mesh, a conductive resin film, a conductive paint film, a metallized fiber, a metal vapor-deposited film formed directly on the cover (2), etc. can be used.

Furthermore, the above-mentioned cover (■) may be made of, for example, polycarbonate, FR, which has been conventionally used as an antenna cover.
In addition to being able to be formed from P, ABS resin, etc., it is also possible to form from various materials that have a small effect on radiated radio waves.

Figure 3 is a diagram showing the radiation directivity obtained by the antenna with the above configuration. When the same phase signals are fed to both feeding points, the antenna In the plane perpendicular to the plate, the direction close to the direction perpendicular to the shorting plate (2) is the main radiation direction, and it is possible to obtain radiation directivity that is almost omnidirectional in the plane parallel to the antenna plate.

Furthermore, when signals having opposite phases are fed to the refeeding points (■), a beam-like radiation directivity can be obtained in the normal direction of the antenna plate, as shown in H in the figure.

In addition, Fig. 3 A and E are planes parallel to the shorting plate ■ (Y- in Fig. 1).
Figure B and D show the electric field strength distribution within
C shows the electric field strength distribution in the plane including the refeeding point ■ (see the X-X line in Figure 1), and C in the same figure shows the electric field strength distribution in the plane parallel to the antenna plate. The above measurement results were obtained with the device installed on a 1 mΦ metal disk modeled after the roof of an automobile.

Therefore, in the antenna with the above configuration, the refeed point ■
While feeding the first signals that are in phase with each other,
By feeding the second signals with mutually opposite phases, it is possible to achieve the radiation directivity shown in FIG. 3A to C for the first signal, and for the second signal, the radiation directivity shown in FIG. , 3rd figure, H
The radiation directivity shown in can be achieved.

As a result, the data transmission area can be widened by using the radiation directivity based on the first signal for data transmission, and the radiation directivity based on the second signal can be used for positioning. By doing so, highly accurate position determination can be performed.

As for the first and second signals, for example, one may be subjected to amplitude modulation, and the other may be subjected to constant amplitude modulation, in order to minimize interference between the two signals. This is preferable because it can suppress the

FIG. 4 is a longitudinal sectional view showing another embodiment of the dual beam antenna.The difference from the above embodiment is that a hanging plate part (8') is integrally formed in the center of the cover 8′
) The only difference is that conductive thin films constituting the shorting plate are provided on both sides of the short-circuit plate, and the structure of the other parts is the same.

Therefore, also in the case of this embodiment, the same directivity as the dual beam of the above embodiment can be obtained.

FIG. 5 is a longitudinal cross-sectional view showing still another embodiment of the dual beam antenna, and the difference from the embodiments of FIGS. 1 and 2 above is that the circumference of the cover The only difference is that a conductive thin film constituting a ground plate (1') extending vertically upward is provided on the inner surface of the side, and the configuration of other parts is the same.

Therefore, in the case of this embodiment, the influence of the level difference between the ground plate (1) and the metal plate (not shown) can be eliminated by the ground plate (1'), and better directivity can be obtained. Can be done.

FIG. 6 is a perspective view showing still another embodiment of the dual beam antenna.The difference from the above embodiment is that each antenna plate is semicircular, and both antenna plates are connected to the shorting plate (■). It is only the points that are made to be circular as a whole. Note that the length of the arcuate outer peripheral surface of each antenna plate is set to approximately one wavelength.

Also in the case of this embodiment, by feeding mutually in-phase signals to the refeeding points, the main radiation direction is in a direction close to the direction perpendicular to the shorting plate ■ in the plane perpendicular to the antenna plate. Therefore, it is possible to obtain radiation directivity that is almost omnidirectional in a plane parallel to the antenna plate. In addition, by feeding signals of mutually opposite phases to the refeeding points, it is possible to obtain beam-like radiation directivity in the normal direction of the antenna plate.

Even in the case of the above-mentioned embodiment, since the conductive thin film constituting the antenna plate is provided on the inner surface of the cover (■), it has sufficient mechanical strength and also In addition, the number of parts can be reduced, and there is no need to attach the antenna plate separately from the cover 〇, so the overall size of the dual beam antenna can be reduced. can do. Also, the cover ■
Since the center part of the ground plate (1) is directed by the shorting plate ■, sufficient mechanical strength can be obtained even if the thickness of the cover ■ is made thinner, and the thickness of the cover ■ can be changed. Otherwise, mechanical strength can be improved.

It should be noted that the present invention is not limited to the above-described embodiments, and can be applied to a case where it is necessary to change the directivity of an antenna in a desired field such as a roadside beacon system. In addition, various design changes can be made without changing the gist of the invention.

<Effects of the Invention> As described above, the present invention surrounds a dual beam antenna consisting of a pair of antenna plates connected to a ground plate by a common shorting plate with a cover, and also includes an antenna plate,
Since at least one of the ground plates is provided on the cover and made of a conductive thin film, initial directivity can be easily obtained, and the dual beam antenna as a whole can be made smaller. Furthermore, the manufacturing process can be simplified by reducing the number of parts, and since the cover is reinforced with a short circuit plate, sufficient mechanical strength can be obtained even if the cover is thin. It has the unique effect of being able to.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing one embodiment of the dual beam antenna of the present invention, Fig. 2 is a longitudinal cross-sectional view, Fig. 3 is a diagram showing radiation directivity, and Figs. 4 to 5 are respective examples of other embodiments. FIG. 6 is a perspective view showing another embodiment; FIG. 7 is a schematic diagram showing the relationship between the roadside antenna and the vehicle-mounted antenna; FIG. 8 is a diagram showing received waveforms according to the conventional example. , FIG. 9 is a perspective view showing the configuration of the dual beam antenna of the prior example, and FIG. 10 is a longitudinal sectional view along a plane including the refeeding point. (1)...Grounding plate, ■...Shorting plate, G) (4)・
...Antenna plate, ■■...Feeding point, ■...Cover Fig. 1 Fig. 2 Fig. 7 Fig. 8 Roadside antenna position

Claims (1)

[Claims] 1. Antenna plates of the same shape extending parallel to the ground plate and in mutually opposite directions are attached to the ground plate through a common shorting plate, and placed at symmetrical positions with the shorting plate as the center. A dual beam antenna with a feeding point provided between an antenna plate and a ground plate, characterized in that one of the ground plate and the antenna plate is composed of a conductive thin film formed at a predetermined position of the antenna cover. Dual beam antenna. 2. The top surface of the casing containing the feeder circuit serves as a grounding plate, and a conductive plate is formed at a predetermined position on the antenna cover on at least a portion of the periphery of the top surface of the casing, and is perpendicular to the top surface. 2. The dual beam antenna according to claim 1, wherein the dual beam antenna is made of a magnetic thin film. 3. Either of the above claims 1 or 2, wherein the conductive thin film is made of metal foil, metal vapor deposited film, metal mesh, conductive resin, conductive paint, or metallized fiber. Dual beam antenna as described in.