JP3230965B2 - Front end for roadside beacon system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a front end for a roadside beacon system used for a roadside beacon for obtaining road information using radio waves in a quasi-microwave band, and more particularly to a roadside beacon system having a predetermined gain even in a low elevation angle direction. Regarding the front end.

[0002]

2. Description of the Related Art In recent years, various communication systems such as various data communication between a base station and a vehicle-mounted station using radio waves or light and communication between vehicle-mounted valleys have been considered. Among them, a radio wave beacon system that receives various data transmitted from the roadside antenna toward the vehicle with the onboard antenna and between the infrared light emitting / emitting element installed on the road and the infrared light emitting / emitting element provided on the onboard equipment side It is highly expected that an optical beacon system for performing various data communications will be put to practical use. This type of roadside beacon system is disclosed in Japanese Patent Publication No. 04-39119 and Japanese Patent Publication No. 04-39719.

An outline of such a radio beacon system and an optical beacon system will be described below. FIG.
FIG. 2 is a schematic diagram showing how communication is performed between each beacon of the optical beacon system and the radio beacon system and a vehicle. Referring to FIG. 7, a signal from radio beacon 61 or optical beacon 62 is provided to running vehicle 63. As is apparent from the figure, the radio wave beacon 61 is generally installed at a higher position than the optical beacon 62, and its radio wave reach area is wide. On the other hand, in the case of the optical beacon 62, the communication area is narrow as shown in the figure.

FIG. 7 is a view taken in the direction of the arrow VII shown in FIG. Referring to FIG. 7, a radio beacon 61 is generally provided on the road side and covers the entire plurality of lanes in one traveling direction. On the other hand, the optical beacon 62 is provided above each lane, and performs communication for each lane.

[0005] On the left and right sides of the installation location of the radio wave beacon 61 shown in FIG. Therefore, the passage of the radio wave beacon 61 can be detected in the receiving vehicle 63 by detecting the phase inversion. The traveling direction can be identified by recognizing the phase inversion direction.

Next, a specific example of the radio beacon receiver will be described with reference to FIG. FIG. 8 shows "Development of beacon receiver" (Sumitomo Electric, No. 141, pp. 135-14).
Radio beacon receiver 2 disclosed in US Pat.
FIG. 2 is a diagram showing an example of the example No. 02. Referring to FIG. 8, radio beacon receiver 202 includes in-vehicle antenna 20 and receiving circuit 21.
And a coaxial cable 22 for transmitting the signal received by the on-vehicle antenna 20 to the signal receiving circuit 21. As the on-vehicle antenna 20, a microstrip antenna using a dielectric substrate is considered, and the receiving circuit 21 is configured by an electronic circuit such as a band-pass filter, a low-noise amplifier, a mixer, and a demodulator.

[0007] The quasi-microwave band signal received by the on-vehicle antenna 20 is guided to a receiver 23 by a coaxial cable 22 of about several meters. The signal input to the receiver 23 is subjected to processing such as low-noise amplification, band limitation, and frequency conversion. The road information included in the signal is demodulated and displayed on a display (not shown) mounted on a vehicle.

[0008]

In such a conventional receiver, a planar antenna using a printed circuit board is used. In the case of a general microstrip antenna as a planar antenna using a printed circuit board, the gain in the low elevation angle direction in the angle direction orthogonal to the plane of polarization is essentially low. In the roadside beacon, since the transmitting antenna has directivity, the direction of the transmitter viewed from the receiver at the periphery of the service area where the electric field level is lowest has a low elevation angle of about 10 °.

Therefore, there is a problem that the gain is reduced in a low elevation angle direction where the gain of the receiving antenna is required.

[0010] In addition, since transmission is performed between the antenna and the receiver using a coaxial cable, there is a problem in that characteristics are deteriorated due to transmission loss of the coaxial cable. In addition, when using an optical beacon and a radio beacon together, it is necessary to separately prepare receivers corresponding to each system.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a front end for a roadside beacon system in which the gain does not decrease in a low elevation angle direction. It is another object of the present invention to provide a front end for a roadside beacon system in which characteristic deterioration due to transmission loss does not occur. Still another object of the present invention is to provide a front end that can use both an optical beacon and a radio beacon.

[0012]

A front end for a roadside beacon system according to the present invention for receiving road information transmitted from a radio transmitter provided on a roadside on a vehicle side has a conductor pattern formed on a surface of a dielectric substrate. Having a microstrip antenna, a rectangular ground conductor plate on which a dielectric substrate is mounted, and a microstrip antenna feed section disposed at a position deviated from a center of the microstrip antenna in a direction intersecting with a vehicle traveling direction. Including. The long side of the ground conductor plate is arranged in a direction crossing the traveling direction of the vehicle, and the microstrip antenna is arranged at the center of the ground conductor plate.

The feeding points of the patches forming the conductor pattern are deviated in the long side direction of the rectangular ground plane, and the long side direction of the rectangular ground plane is arranged in a direction intersecting the vehicle traveling direction. Thereby, the gain in the low elevation angle direction required for the radio beacon can be increased.

Preferably, a low noise amplifier is provided on the ground conductor plate,
An electronic circuit including a frequency converter and a demodulator is provided. The frequency converter includes a crystal oscillator and a band-pass filter, and the crystal oscillator and the band-pass filter are arranged on the same plane as the microstrip antenna.

An electronic circuit including a low-noise amplifier, a frequency converter, and a demodulator is provided on the surface of a rectangular ground conductor plate, and tall components such as a crystal oscillator and a band-pass filter of the electronic circuit are arranged on the same surface as the antenna. By doing so, it is possible to provide a small-sized front end for a roadside beacon system that has a low profile and low loss and is not easily affected by unnecessary radiation from a crystal oscillator.

Further, it is preferable to use a plate-shaped inverted F antenna as a receiving antenna of the microstrip antenna. By using this antenna, a small front end for a roadside beacon system can be provided.

More preferably, the housing including the support of the microstrip antenna and the electronic circuit is integrally formed of synthetic resin. Conductive foil is stretched on the surface of the synthetic resin,
Thereby, a shield case for the antenna and the electronic circuit is formed.

The antenna support and the housing of the electronic circuit are integrally formed of synthetic resin, and a conductor foil is provided on the surface of the synthetic resin to form a shield case for the antenna and the electronic circuit.

[0019] More preferably, the front end for the roadside beacon system includes light receiving means for receiving and emitting light signals and light emitting means. Part of the shield case or the microstrip antenna has a function of concentrating and reflecting light, whereby the optical beacon system front end is integrated with the roadside beacon system front end. By providing a light receiving / emitting means at the front end for the roadside beacon system and configuring a shield case or the like so as to concentrate and reflect light, the front end for the optical beacon system and the front end for the roadside beacon system can be easily integrated.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a first embodiment of a front end for a roadside beacon system (hereinafter abbreviated as “roadside beacon”) according to the present invention.

Referring to FIG. 1, a road-side beacon front end 31 according to the present invention includes a microstrip antenna 32, a rectangular ground conductor plate (hereinafter abbreviated as "rectangular ground plate") 3 for holding microstrip antenna 32, and And electronic circuits 5a and 5b provided on the rectangular ground plate 3.

The electronic circuit 5a includes a dielectric filter 7 and a low-noise amplifier IC 8, and is covered by a shield case 4a. The electronic circuit 5b includes the crystal oscillator 9 and is covered by the shield case 4b. A coaxial cable 6 for transmitting a received signal is connected to the electronic circuit 5b.

The microstrip antenna 32 includes a dielectric substrate 1 and a conductor patch 2 having a conductor pattern provided on the dielectric substrate 1, and is deflected in one direction from a center point 10 on the conductor patch 2. Power is supplied at the supplied power supply point 11.

The shape of the conductor patch 2 of the microstrip antenna 32 may be a circle, a square, a rectangle, or the like, and a type that is excited in the fundamental mode is often used. In this embodiment, a similar conductor patch is used.

When the power is supplied while the power supply point 11 is deviated from the center 10 of the conductor patch 2, a current flows from the power supply point 11 in a direction including the center 10, and the fundamental mode is excited. As the antenna directivity, the electric field plane directivity is obtained with respect to the plane including the current, and the magnetic field plane directivity is obtained in a plane perpendicular to the electric field plane, and the antenna is installed so that the magnetic field plane direction becomes the directivity in the vehicle traveling direction. .

The signal received by the conductor patch 2 is guided to electronic circuits 5a and 5b inside the shield cases 4a to 4c and an electronic circuit (not shown) on the back surface. The received signal is guided to the dielectric filter 7, the low noise amplifier IC 8, and the like. The circuits provided in the electronic circuits 5a and 5b and the like are composed of functional blocks for band limitation, low noise amplification, frequency conversion and the like. With these functional blocks, processing such as band limiting and low noise amplification is performed, mixed with the signal of a local oscillator composed of a crystal oscillator 9 and the like, frequency-converted to an intermediate frequency with little cable loss, and transmitted to the coaxial cable 6. I will Thereafter, the data is input to a demodulator (not shown), and the road information is demodulated.

The directivity of the microstrip antenna 32 changes depending on the ground plane. For this reason, it is sufficient for the size of the dielectric substrate 1 to be large enough to form the conductor patch 2, and it is preferable that the size is small in consideration of the material cost. Specifically, the minimum size of the conductor patch 2 is about 15 mm, and the size of the dielectric substrate 1 at that time is about 20 mm. As described above, the dielectric substrate forming the microstrip antenna has a minimum size in which the conductor patch 2 can be formed, and the dielectric substrate 1 is disposed at the center of the rectangular ground plate 3 so that the area of the expensive dielectric substrate is minimized. , The directivity in the short side direction of the rectangular ground plate 3 can be widened.

In a general case where the microstrip antenna can be regarded as being installed on an infinite ground plane, the directivity in the magnetic field plane is the directivity shown in FIG.

In the radio beacon, the value of θ in FIG.
A radio wave arrives from a portion of 0 degrees or less. Therefore, it is desired from the viewpoint of reception performance that the gain of that portion be as high as possible.

When the size of the rectangular ground plate 3 is finite as in this embodiment, the directivity changes due to diffraction from inside the rectangular ground plate 3. When the base plate 3 is formed in a rectangular shape in which a side parallel to the magnetic field surface is a short side and a side orthogonal to the long side is a long side, the magnetic field surface directivity becomes the directivity shown in FIG. The gain in the portion where the medium θ is large increases. The larger the ratio of the long side to the short side, the larger the gain increase. When the ratio of the long side to the short side is 4/3 or more, the gain increase is about 10 dB or more at θ ≒ 80 °.

The position of the dielectric substrate 1 with respect to the rectangular ground plate 3 is preferably located at the center in the long side direction since the directivity of the electric field surface becomes symmetric. Further, since the magnetic field plane directivity changes depending on the installation position with respect to the short side direction, the directivity can be directed to a desired direction, for example, the direction of the front window, which is the traveling direction of the vehicle, by arranging the magnetic field plane at a biased position. Further, it is desirable that the position where the coaxial cable 6 is pulled out is arranged near the center in the long side direction in order to maintain the symmetry of the electric field plane directivity.

Even if the shield cases 4a and 4b for accommodating the electronic circuits 5a and 5b are provided on the rectangular base plate 3, the antenna directivity hardly changes. By arranging a low-noise amplifier, a band-pass filter, and the like near the antenna, the length of the feed line can be shortened, and the loss due to the feed line can be reduced, so that the reception performance can be improved.

The electronic circuits 5a and 5b are surface mount (SMT) parts such as transistors, resistors, capacitors, and ICs, and are low-profile parts having a height of about 1 to 2 mm;
It is made of a high-tall component such as a crystal oscillator 9 having a height of 4 to 5 mm or more. The dielectric substrate 1 has a substrate thickness of 3 mm or more. Therefore, by arranging the tall component on the same surface as the antenna and arranging the SMT component on the back surface of the antenna, it is possible to minimize an increase in the thickness of the front end caused by integrating the antenna and the electronic circuit.

Further, the crystal oscillator 9 is arranged in the electronic circuit 5b on the surface of the rectangular base plate 3, and the low-noise amplifier IC 8 is connected to the rectangular base plate 3.
Is arranged in the electronic circuit on the back surface of the crystal oscillator 9.
, Etc., can be made less susceptible to unnecessary radiation such as higher-order oscillation signals.

FIG. 3 is a diagram showing a configuration of a roadside beacon front end 33 according to a second embodiment of the present invention. FIG. 4 is a view of the road-side beacon front end 33 shown in FIG. 3 as viewed from the opposite side, in which a plate-shaped inverted-F antenna is used as an antenna. Since the road-side beacon front end 33 according to the second embodiment is basically the same as the road-side beacon front end 31 according to the first embodiment, the same portions will be denoted by the same reference numerals and redundant description will be omitted.

Referring to FIG. 3 and FIG. 4, the road-side beacon front end 33 includes a resin housing 12 and a resin housing 12.
Conductor pattern 14 provided on the shield case 1
5 and a short-circuit through hole 13. The shield case 15 operates as a ground plane of the antenna and serves as a case for housing the electronic circuits 5a and 5b. The short-circuit through hole 13 is a conductor through hole for short-circuiting the shield case 15 and the conductor pattern 14. In the conductor pattern 14, the distance between the side where the short-circuiting through hole 13 is provided and the side opposite to the side is approximately λ / 4 with respect to the wavelength λ to be used.

The resin housing 12 holds the conductor pattern 14, the shield case 15, and the short-circuiting through hole 13 at regular intervals. The conductor pattern 14 and the shield case 15 are manufactured by applying a metal plating such as copper to the resin housing 12 and forming a pattern by etching the formed copper foil or the like. You. In addition to the pattern formation, there is a method of forming a conductive foil on a part of the resin housing 12 by an additive method.

The directivity of the plate-shaped inverted-F antenna is almost the same as that of the microstrip antenna, and the plane parallel to the perpendicular drawn from the feed point 11 to the side where the short-circuit through hole 13 is provided is the electric field plane directivity. , The plane perpendicular to the perpendicular line becomes the magnetic field plane directivity. When the shape of the shield case 15 is a rectangular shape in which a side parallel to the magnetic field surface is a short side and a side perpendicular to the magnetic field surface is a long side, the gain of the magnetic field plane directivity in a low elevation angle region is increased similarly to the microstrip antenna. The reception signal of the antenna is taken out from the feeding point 11.

FIG. 5 is a view showing a road-side beacon front end according to a third embodiment of the present invention, in which a radio beacon and an optical beacon receiver are integrated. Third
Also in the embodiment, the front end 35 is the road-side beacon front ends 31, 3 of the first and second embodiments.
3 is basically the same as that of FIG. Referring to FIG. 5, front end 35 according to the third embodiment is a dielectric substrate 1 having a short-circuited ground plate 3 and a conductor patch 2 provided on short-circuited ground plate 3.
, Shield cases 4a to 4c, and an IRED (infrared light emitting diode) 16 which is a light emitting element of an optical beacon.

In the optical beacon system, the wavelength is 850 nm.
Near infrared rays are used for transmitting and receiving information. In the third embodiment, a metal material having a high reflectance of infrared light is used for the shield cases 4a and 4b and the conductor patch 2, and as shown by arrows in FIG. The upper surfaces of the shield cases 4a and 4b and the conductor patch 2 have an inclined structure or a curved surface structure so that infrared rays arriving in the direction 2 are reflected and emitted to the front. Thereby, IRED16
Can be efficiently used for communication. Further, it is possible to arrange a light receiving element such as a photodiode in place of the IRED 16 to efficiently receive the transmission light.

[0041]

In the front end for the roadside beacon system according to the first aspect, the feeding point of the patch forming the conductor pattern is deviated in the long side direction of the rectangular ground plane, and the long side direction of the rectangular ground plane is changed. It is arranged in a direction that intersects with the vehicle traveling direction. Thereby, the gain in the low elevation angle direction required for the radio beacon can be increased. As a result, a front end for a roadside beacon system without lowering the gain in the low elevation angle direction can be provided.

According to a second aspect of the present invention, there is provided a roadside beacon system front end provided with an electronic circuit including a low-noise amplifier, a frequency converter, and a demodulator on the surface of a rectangular ground conductor plate. Place tall components such as filters on the same plane as the antenna. As a result, it is possible to provide a small-sized front end for a roadside beacon system which has a low profile and low loss and is hardly affected by unnecessary radiation from a crystal oscillator.

The front end for the roadside beacon system according to the third aspect uses a plate-shaped inverted F antenna, so that the front end can be downsized.

In the front end for a roadside beacon system according to a fourth aspect, the antenna support and the housing of the electronic circuit are integrally formed of synthetic resin, a conductor foil is provided on the surface of the synthetic resin, and a shield case for the antenna and the electronic circuit. By forming the front end, it is possible to provide a roadside beacon system front end having a structure suitable for mass production with a small number of assembling steps.

In the front end for the roadside beacon system according to the fifth aspect, a light receiving / emitting means is provided on the front end, and a shield case or the like is formed so as to concentrate and reflect light. Therefore, since the front end for the optical beacon system and the front end for the roadside beacon system can be easily integrated, a single front end can support the optical beacon system and the radio beacon system.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a roadside beacon front end according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating the directivity of a road-side beacon front end.

FIG. 3 is a diagram illustrating a configuration of a road-side beacon front end according to a second embodiment.

FIG. 4 is a diagram showing a configuration of a roadside beacon front end according to a second embodiment.

FIG. 5 is a schematic diagram illustrating a configuration of a front end according to a third embodiment.

FIG. 6 is a schematic diagram showing an outline of a beacon system.

FIG. 7 is a schematic diagram showing an outline of a beacon system.

FIG. 8 is a diagram showing a conventional radio beacon receiver.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dielectric substrate 2 Conductor patch 3 Rectangular ground plane 4 Shield case 5 Electronic circuit 6 Coaxial cable 7 Dielectric filter 8 Low-noise amplification IC 9 Crystal oscillator 10 Center of conductor patch 11 Feeding point 31, 33 Front end for roadside beacon 32 Microstrip Antenna 35 Front end

Continuation of the front page (72) Inventor Yasushi Miyakawa 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (56) References JP-A-63-136199 (JP, A) JP-A-58-104504 (JP) JP-A-54-139359 (JP, A) JP-A-6-45824 (JP, A) JP-A-1-245705 (JP, A) JP-A-6-260949 (JP, A) JP-A-7-273535 (JP, A) JP-A-4-115185 (JP, A) JP-A-6-252630 (JP, A) JP-A-7-221535 (JP, A) A) Jikatsu Hei 7-29918 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01Q 13/08 G01S 1/68 G08G 1/0968 H01Q 1/32 H01Q 9/36 JICST File (JOIS)

Claims (5)

(57) [Claims] 1. A front end for a roadside beacon system which receives road information transmitted from a radio transmitter provided on a roadside on a vehicle side, comprising: a microstrip antenna having a conductor pattern on a surface of a dielectric substrate; A rectangular ground conductor plate on which the dielectric substrate is mounted, and a feeder of the microstrip antenna disposed at a position deviated from a center of the microstrip antenna in a direction crossing a vehicle traveling direction. A long side of the ground conductor plate is disposed in a direction intersecting with a traveling direction of the vehicle, and the microstrip antenna is disposed at the center of the ground conductor plate. 2. The ground conductor plate includes an electronic circuit including a low noise amplifier, a frequency converter, and a demodulator provided thereon, the frequency converter includes a crystal oscillator and a band-pass filter, and the crystal oscillator The front end for a roadside beacon system according to claim 1, wherein a bandpass filter and a bandpass filter are provided on the same surface as the microstrip antenna. 3. The front end for a roadside beacon system according to claim 2, wherein the receiving antenna of the microstrip antenna is a plate-shaped inverted-F antenna. 4. The microstrip antenna and a housing including the electronic circuit are integrally formed of synthetic resin, and a conductive foil on the surface of the synthetic resin forms a shield case for the microstrip antenna and the electronic circuit. The front end for a roadside beacon system according to claim 1, wherein: 5. A light receiving and receiving means for receiving and emitting an optical signal, wherein said shield case or a part of said microstrip antenna has a function of concentrating and reflecting light, whereby a front end for an optical beacon is provided. The front end for a roadside beacon system according to any one of claims 1 to 4, wherein the front end is integrated with a roadside beacon system.