JPH10154909A - Antenna system for on-vehicle equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the interference to an adjacent line by using a micro stripped antenna having nonfeed elements on a transmitting/receiving antenna for an on-vehicle antenna system. SOLUTION: The micro stripped antenna 27 is composed of a dielectric board 14, radiation elements 25a and 25b, an earth conductor 26 and the nonfeed elements 16a and 16b provided on the micro stripped antenna. By attaching the nonfeed elements 16a and 16b, Q is reduced, the wideband characteristic of an input impedance is obtained as well as gain is increased. The resonant frequency of the nonfeed element is decided by an equivalent dielectric constant which is determined from three dielectric layers, the dielectric board 14 of a radiation element, the 2nd dielectric board 15 of the nonfeed element and a space 28. Since the space is generally an airspace and its dielectric constant is 1, its equivalent dielectric constant steeply lowers. The value is approximately 1.2, and the dimensions of the nonfeed elements are determined from this equivalent dielectric constant and equivalently to be a low dielectric constant, so that the aperture of antenna is to be large, a beam is to be narrow and gain is to be high.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-stop automatic toll collection system, and more particularly to the transfer of toll information between a roadside device provided in a tollgate area and a vehicle-mounted device provided in a vehicle. The present invention relates to the antenna of the above-mentioned in-vehicle device.

[0002]

2. Description of the Related Art Conventionally, on a highway or the like, a magnetic card type toll collection system has been introduced. Regarding this collection system, for example, Toshiba Review (40
No.) Showa 60, pp. 189-192, "Magnetic Card System Toll Collection System" or Mitsubishi Heavy Industries Technical Report VOL. 22
NO. 6 (1985-11), pages 127 to 132, "System Technology in Magnetic Card Type Toll Collection Machine".

In such a conventional system, when entering an expressway from a general road or conversely, when exiting from an expressway, the train must be temporarily stopped at a tollgate to receive a toll ticket or pay a toll. Must be carried out, which often results in many cars lining up in front of the toll booth. In order to improve such a problem, a non-stop automatic toll collection system that can collect tolls without stopping at a tollgate for some time has been proposed.

For such a system, for example,
Mitsubishi Heavy Industries Technical Report VOL. 32 NO. 4 (1995-7)
P264-267 "Needs and Technical Development in Expressway Traffic Management Systems", NIKKEI BUSINES
S, November 13, 1995, pages 155 to 158, "Information is transmitted from the road to the car,""A battle for initiative in Japan, the United States, and Europe", or published patent publication 5-508492, "Electric vehicle toll collection device and method." In particular, Japanese Patent Application Laid-Open No. 5-508492 discloses a detailed description.

In order to realize such a system,
It is necessary to transmit information between a roadside machine provided in the tollgate area and a vehicle-mounted machine mounted on the vehicle. FIG. 9 shows a conventional example. Yacoubi, "An Ele
ctonic Tolland Traffic M
analysis System ”, Microwa
ve Journal, pp. 64-72, July
9 shows information transmission between a roadside device and a vehicle-mounted device of the non-stop toll collection system shown in 1994. In FIG. 9, 1 is an automobile, 2 is a motorcycle, and 3a and 3b are automobiles and on-vehicle devices mounted on the motorcycle, respectively. 4 is a road machine, 5 and 6 are transmitting and receiving antennas respectively provided on the road machine, 7 is a column provided on the road machine, 8 is a driving lane, 9 is an island for separating lanes,
10 is an adjacent lane. Information is transmitted between the on-road antenna and the on-vehicle antenna, and non-stop fee collection is performed without stopping.

FIG. 10A is an external view of a non-stop toll collection system in which the in-vehicle device is installed on, for example, a dashboard in an automobile, and FIG. 10B is a configuration diagram of the in-vehicle device. 23 and 24 are transmitting antennas and receiving antennas installed inside the vehicle-mounted device, 11 is a transceiver, 12 is a display for displaying the payment amount or balance of the tollgate,
Reference numeral 13 denotes a power supply cable for obtaining an in-vehicle device from inside the vehicle.

Next, the operation will be described. An in-vehicle device antenna is required to be small, thin, and low in cost. or,
Circular polarization is employed to reduce interference. The microstrip antenna is composed of a ground conductor, a dielectric plate, and a radiation conductor and has a simple configuration. Usually, the microstrip antenna can be easily manufactured only by etching a dielectric substrate, and thus cost reduction can be achieved. A dipole antenna, a slot antenna, and the like are also conceivable, but a reflector is required to radiate light in one direction. Generally, the distance between the antenna element and the reflector is 0.25 wavelength, and 12.5 mm in the C band, so that the thickness cannot be reduced. Since it is suitable for an antenna requiring a thin or small size, it is suitable as an in-vehicle device antenna. In order to excite circularly polarized waves, a method of loading a degenerate separation element with one-point power supply or a method of providing two-point power supply with a phase difference of 90 degrees with a feed line or the like at an orthogonal position may be used. Also has the feature that it can be easily manufactured by etching.

[0008]

The non-stop automatic toll collection system is under joint development by the public and private sectors in Japan, and its practical use is said to be from 1997 onward. On the other hand, in some overseas countries, a system as shown in the above publication is operated.

In this non-stop automatic toll collection system, it is necessary to transmit and receive information using a radio wave between a car entering the toll booth area and the toll booth. To do so, an antenna with little interference in the adjacent lane is required. Naturally, it is desirable that the on-road antenna provided on the road has a shaping beam for irradiating only the own lane. However, since the shaping of the beam increases the antenna size, there is a practical limit. Further, even if an antenna side lobe of about -30 dB is realized, if the level is reduced to such a level, the surrounding environment is affected. In addition, interference may occur even when a large vehicle passes through the adjacent lane. Furthermore, since it is mounted inside the vehicle, multiple reflections occur on the vehicle body, glass, steering wheel, bonnet, etc., so that the radiation characteristics are disturbed, and there is a problem that interference in adjacent lanes increases. In order to reduce this interference, it is desirable that the on-vehicle unit antenna also be a beam-forming antenna capable of reducing interference from an adjacent lane. However, the size of the antenna becomes large in order to form it,
Low cost is a condition and is not possible for antenna beam shaping.

Accordingly, it is an object of the present invention to obtain an on-vehicle device antenna device which causes less interference with an adjacent lane.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an on-vehicle unit antenna apparatus according to a first aspect of the present invention uses a microstrip antenna in which a parasitic element is attached to a transmitting antenna and a receiving antenna. is there.

A vehicle-mounted device antenna device according to a second aspect of the present invention uses a microstrip antenna having a parasitic element mounted on the back or front surface of a radome for protecting the transmitting antenna, the receiving antenna, or both microstrip antennas. It is.

Further, the antenna device for a vehicle-mounted device according to a third aspect of the present invention is configured such that a microstrip antenna provided with a parasitic element is fed at two points by a feed circuit using a microstrip line.

A vehicle-mounted device antenna device according to a fourth aspect of the present invention is a microstrip antenna in which two or more parasitic elements are provided on the transmission antenna and / or the reception antenna to perform diversity reception or diversity transmission. is there.

The vehicle-mounted device antenna device according to the fifth invention is an array antenna in which two or more microstrip antennas provided with parasitic elements are arranged.

A vehicle-mounted device antenna device according to a sixth aspect of the present invention is configured such that a microstrip antenna provided with a parasitic element is an array antenna in which two or more elements are arranged, and a null in an adjacent lane direction is formed by changing an element interval. It was done.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 is a schematic configuration diagram showing Embodiment 1 of the present invention. In the figure, 14 is a dielectric substrate, 25
a and 25b are radiation elements, 26 is a ground conductor, and these constitute a microstrip antenna 27. Fifteen
Is a second dielectric substrate, 16a and 16b are parasitic elements provided above the microstrip antenna, and 28 is a space between the dielectric substrate 14 and the second dielectric substrate 15. or,
11 is a transceiver.

Next, the operation will be described. The directivity gain without loss of the microstrip antenna is about 6-7.
It is about dB, and has a higher gain than a dipole antenna or a slot antenna. However, actually, the gain is reduced due to the dielectric loss or the conductor loss. This loss is determined by the dielectric constant of the substrate and tan δ. A Teflon-based substrate or a ceramic substrate has a relatively small loss, whereas a glass-epoxy-based substrate has a large loss, sometimes several dB. Therefore, if the directivity gain is about 7 dB
Even if it is of the order, it is expected that it will be reduced to about 0 dBi due to the loss of the substrate or multiple reflections in the surroundings.

In order to increase the gain in a microstrip antenna, it is necessary to reduce the dielectric constant of the substrate. Honeycomb substrates have a low dielectric constant and are suitable but expensive.
Therefore, as another method for increasing the gain, there is a method using a parasitic element. Generally, this parasitic element is often used for widening the input impedance. By adding a parasitic element, Q is reduced, and broadband characteristics can be obtained. Here, the purpose is to increase the gain in addition to the broadband. It is considered that radiation is mainly performed from the parasitic element by attaching the parasitic element. Therefore, the resonance frequency of the parasitic element is determined by the equivalent dielectric constant determined by the dielectric substrate 14 of the radiating element, the second dielectric substrate 15 of the parasitic element, and the three dielectric layers of the space 28. Generally, the space is often an air layer, and since the air layer has a dielectric constant of 1, the equivalent dielectric constant sharply decreases. The value is about 1.2, and the parasitic element dimensions can be almost determined from the equivalent permittivity. Since the dielectric constant is equivalently reduced in this way, the aperture of the antenna is enlarged, and the beam is squeezed to increase the gain.

FIG. 2 (a) shows a vehicle 1 running in a driving lane 8, an adjacent lane 10, and a roadside machine 4 and a vehicle-mounted machine 3.
Vehicles on the traveling lane need to communicate only with the road units in the own lane, and radio waves from road units in the adjacent lanes cause interference. Of course, it is desirable that the antenna provided on the roadside machine has a shaped beam characteristic that irradiates only the own lane. For this reason, the size of the antenna becomes large and some interference occurs. Therefore, the antenna provided in the on-vehicle device can receive only the own lane as much as possible, and a low radiation level in the adjacent lane direction is desired. The adjacent angle to the on-road unit 4 in the adjacent lane as viewed from the on-board unit 3 installed on the traveling lane is about 50 °.

FIG. 2B shows calculated values of the gain in the traveling lane and the gain in the 50 ° direction when the dielectric constant of the substrate of the microstrip antenna is changed. When the permittivity is increased, the gain of the traveling lane decreases, but the gain in the 50 ° direction increases, that is, the interference with the adjacent lane increases. On the other hand, it can be seen that when the dielectric constant becomes low, the gain in the traveling lane increases, the gain in the 50 ° direction decreases, and interference can be reduced. From this figure, it can be seen that several dB interference can be reduced by using a parasitic element to reduce the dielectric constant.
The present invention does not depend on the type of the substrate and the shape of the antenna. Also, the present invention is effective for power supply lines such as a coaxial power supply, a microstrip line, and a triplate line regardless of the power supply method.

Embodiment 2 FIG. FIG. 3 is a schematic configuration diagram showing Embodiment 2 of the present invention. In the figure, reference numeral 17 denotes a radome. The surface of the antenna needs a radome to protect the antenna. Although the second dielectric substrate 15 for the parasitic element was necessary as in the first embodiment in order to form the parasitic element, here, the radome is also used as the substrate for the parasitic element. It is. This eliminates the need for the second substrate, thereby simplifying the configuration and reducing the cost. The parasitic element may be a copper foil tape or a seal, and can be easily attached to the radome. Here, an example of a circular microstrip antenna is shown, but the present invention is also effective for a square, a triangle, an ellipse, and the like without depending on the shape. In FIG. 3, the spacer between the dielectric substrate 14 and the second dielectric substrate 15 is exaggerated for simplicity.
Actually, it is sufficiently smaller than the size of the microstrip antenna, about 1 to 2 mm, and keeps a thin shape.

Embodiment 3 FIG. FIG. 4 is a schematic diagram showing Embodiment 3 of the present invention. In the figure, reference numerals 18a and 18b denote feed circuits for exciting circularly polarized waves for transmission and reception, respectively. There are one-point feeding and two-point feeding for exciting circularly polarized waves. The one-point feeding method is a method in which a circularly polarized wave is excited by providing a notch or the like to solve the degeneracy of orthogonal modes. In this system, the frequency width at which circularly polarized waves occur is narrow in principle. In the case of an in-vehicle antenna, antenna characteristics are greatly degraded due to multiple reflections by walls, glass, and a human body in the vehicle. Therefore, it is necessary to minimize antenna characteristic degradation in an environment with multiple reflections. Therefore, a configuration using two-point power supply is shown in the figure. The two-point feeding method is a method of exciting two orthogonal points with a phase difference of 90 degrees. This method can increase the bandwidth by several times as compared with the single-point feeding method. Therefore, deterioration of antenna characteristics is reduced even in an environment of multiple reflection. This two-point power supply method can also be easily processed by etching, similarly to the one-point power supply method. The present invention is effective even if a Wilson-type power supply circuit or a hybrid coupler that can achieve a wider band is used in addition to the T-branch circuit type in the two-point power supply system.

Embodiment 4 FIG. 5 is a schematic configuration diagram showing Embodiment 4 of the present invention. In the figure, reference numerals 20a and b denote diversity receiving antennas, reference numerals 21a and b denote diversity transmitting antennas, and reference numeral 19 denotes respective transceivers, which are integrally shown. Diversity includes polarization diversity, space diversity, directivity diversity, frequency diversity, and the like, and is used for various systems including mobile phones. The interior of the automobile is covered with a metal body, and there are many reflectors such as glass and steering wheel, so that a standing wave is generated. In such an environment, a standing wave is generated about every 1/2 wavelength, so that the reception level is greatly reduced at the position of the valley of the standing wave. A decrease in the reception level leads to an increase in the error rate, which has a great effect on the system. Space diversity is effective in such an environment, and an example of the configuration is shown in FIG. By arranging two antennas at a certain interval of about half a wavelength, detecting the reception level and selecting the higher reception level, one antenna is temporarily located at the position of the valley of the standing wave. But because the other antenna is a standing wave peak,
It can always be received at a certain level or higher. Therefore, since the reception level can be secured, the error rate can be reduced. Other diversity combining methods include equal gain combining method, maximum ratio combining method, and the like, and this combining is possible in any of the RF band, IF band, and baseband. Although an example of a two-element array has been described, it goes without saying that diversity is effective even with three or more elements.

Embodiment 5 FIG. FIG. 6 is a schematic configuration diagram showing Embodiment 5 of the present invention. Embodiments 1 and 2 show a method of increasing the gain by using a parasitic element. However, here, an example is shown in which two elements of an antenna are combined in phase to further increase the gain in the front direction. By using a two-element array, a gain can be obtained without using a parasitic element, so that the thickness can be extremely reduced. 3d by using a two-element array
The gain above B can be increased.

Embodiment 6 FIG. FIG. 7 is a schematic configuration diagram showing Embodiment 6 of the present invention. In the figure, reference numeral 22 denotes an element interval between two elements. The gain can be increased by using a two-element array as in the fifth embodiment. However, by arranging two elements in the lane width direction and changing the element interval, the radiation pattern in the lane width direction can be changed. FIG. 8 shows a radiation pattern when the element interval is set to 0.65 wavelength. The peak gain is 10.2 dBi, which is about 3 dB higher than that of one element. Further, a null is formed in the direction at an angle of 50 °. This angle is the direction of the on-road unit in the adjacent lane, and thus interference from the on-road unit in the adjacent lane can be suppressed. In this configuration, of course, a parasitic element may be used, and interference can be further reduced. The present invention is effective in any case without depending on the type of the substrate, the shape of the antenna, or the power supply method.

[0027]

According to the first aspect of the invention, the gain can be increased with a simple configuration by using a microstrip antenna in which a parasitic element is attached to a transmitting antenna and a receiving antenna, and interference from adjacent lanes can be reduced. There is.

According to the second aspect of the present invention, the use of a microstrip antenna having a parasitic element attached to the back or front surface of the radome for protecting the transmitting antenna, the receiving antenna, or both microstrip antennas reduces costs. There is an effect that can be achieved.

According to the third aspect of the present invention, the microstrip antenna provided with the parasitic element is of a two-point feeding type, so that the axial ratio can be broadened.

According to the fourth aspect, the transmitting antenna and / or the receiving antenna is a microstrip antenna provided with two or more parasitic elements, and is used for diversity reception or diversity transmission / reception. There is an effect that the transmission level or the reception level can be increased even in a certain environment.

According to the fifth aspect of the present invention, a high gain can be obtained and interference from an adjacent lane can be reduced while the thickness is reduced by arranging two or more microstrip antennas provided with parasitic elements. There is.

According to the sixth aspect of the present invention, an array antenna in which two or more microstrip antennas each having a parasitic element are arranged is arranged, and a null in an adjacent lane direction is generated by changing an element interval to further reduce interference. There is an effect that can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing Embodiment 1 of an in-vehicle device antenna device according to the present invention.

FIG. 2 is a diagram showing a calculation example of a gain of the in-vehicle device antenna device according to the first embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing a vehicle-mounted device antenna device according to a second embodiment of the present invention;

FIG. 4 is a schematic configuration diagram showing Embodiment 3 of an on-vehicle apparatus antenna device according to the present invention.

FIG. 5 is a schematic configuration diagram showing a vehicle-mounted device antenna device according to a fourth embodiment of the present invention.

FIG. 6 is a schematic configuration diagram showing Embodiment 5 of an in-vehicle device antenna device according to the present invention.

FIG. 7 is a schematic configuration diagram showing Embodiment 6 of an in-vehicle device antenna device according to the present invention.

FIG. 8 is a diagram illustrating a calculation example of a radiation pattern according to a sixth embodiment of the in-vehicle apparatus antenna device according to the present invention.

FIG. 9 is a diagram showing an outline of an information transmission system for receiving a fee nonstop.

FIG. 10 is a schematic configuration diagram showing a configuration example of an antenna of a conventional vehicle-mounted device.

[Explanation of symbols]

1 Automobile, 2 Motorcycle, 3 Onboard Machine, 4 Roadside Machine, 5
Transmitting antenna, 6 receiving antenna, 7 prop, 8 running lane, 9 island, 10 adjacent lane, 11 transceiver, 12 display, 13 supply power cable, 1
4 Dielectric substrate, 15 Second dielectric substrate, 16
(A), (b) Parasitic element, 17 radome, 18
Feeding circuit, 19 diversity transceiver, 20 diversity transmission antenna, 21 diversity reception antenna, 22 element spacing, 23 transmission antenna, 24 reception antenna, 25 (a), (b) radiation element, 26 ground conductor, 27 microstrip antenna, 28 spaces.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H01Q 19/00 H01Q 19/00 21/06 21/06 21/24 21/24 (72) Inventor Akio Inage Chiyoda-ku, Tokyo 2-6-2, Machi, Mitsubishi Electric Engineering Co., Ltd.

Claims (6)

[Claims] 1. An antenna of an on-vehicle device for exchanging information related to tolls between a road device provided in an area of a tollgate and an on-vehicle device provided on a vehicle, wherein the antenna of the on-vehicle device is grounded. A microstrip antenna comprising a conductor, a dielectric substrate provided on a ground conductor, and a radiating element provided on the dielectric substrate is used, and a parasitic element is provided above the radiating element of the microstrip antenna. An antenna device for a vehicle-mounted device, comprising: 2. The antenna of the on-vehicle device for exchanging information related to tolls between the on-road device provided in the tollgate area and the on-vehicle device provided in the vehicle, wherein the antenna of the on-vehicle device is grounded. A microstrip antenna composed of a conductor, a dielectric substrate provided on a ground conductor, and a radiating element provided on the dielectric substrate is used, and the antenna is protected above the radiating element of the microstrip antenna. An antenna device for an in-vehicle device, comprising: a radome to be provided, and a parasitic element provided on a rear surface or a front surface of the radome. 3. The microstrip antenna according to claim 2, wherein two substantially orthogonal positions are fed with a phase difference of substantially 90 degrees using a microstrip antenna line to excite circularly polarized waves. An antenna device for a vehicle-mounted device according to claim 1. 4. The microstrip antenna is composed of a plurality of two or more antennas, and one of the two or more antennas is selected to perform diversity reception, diversity transmission, or diversity transmission and reception. The antenna device for an in-vehicle device according to claim 1, wherein: 5. The on-vehicle vehicle according to claim 1, wherein the microstrip antenna is composed of two or more microstrip antennas, and the two or more microstrip antennas are combined in phase. Machine antenna device. 6. The microstrip antenna comprising two or more microstrip antennas is synthesized in phase, the element spacing of the two or more microstrip antennas is changed, and nulls are formed in the adjacent lane direction. The antenna device for an in-vehicle device according to any one of claims 1 to 5, wherein: