JP2003168917A - Multi-frequency common antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the gains of antenna elements operating in a plurality of frequency bands at the same time. <P>SOLUTION: The multi-frequency common antenna having a GPS antenna (wavelength λ<SB>1</SB>) 10, a VICS antenna (wavelength λ<SB>2</SB>) 20 and an ETC antenna (wavelength λ<SB>3</SB>) 30 formed on a ground plate 4 surface comprises a reflective conductor plate 5 with a distance (d) from the ground plate 4 so as to meet the equations (1)-(3), thereby improving the gains of the GPS and the VICS antennas at an elevation angle of 90° and the ETC antenna at an elevation angle of 60° at the same time, wherein (m), (n), (k) are natural numbers. ((2m-1)/4-0.1)λ<SB>1</SB>≤d≤((2m-1)/4+0.1)λ<SB>1</SB>... (1) ((2n-1)/4-0.1)λ<SB>2</SB>≤d≤((2n-1)/4+0.1)λ<SB>2</SB>... (2) (k/2-0.1)λ<SB>3</SB>≤d≤(k/2+0.1)λ<SB>3</SB>... (3). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-frequency shared antenna that can operate in a plurality of frequency bands.

[0002]

2. Description of the Related Art Conventionally, for example, a GPS has been used as an antenna for in-vehicle communication equipment.
(Global Positioning System) signal and VICS (Vehic
le Information and Communication System) A common antenna that can receive each signal has been developed. In-vehicle antenna, especially when installing the antenna in the vehicle,
It is necessary to meet the contradictory requirements of miniaturization and high gain of the antenna in consideration of the space limitation and the influence of the metal constituting the vehicle body. As such a shared antenna, Japanese Patent Application Laid-Open No. 7-297631 discloses an antenna in which a plate-shaped slot antenna for VICS signals is provided on a microstrip antenna for GPS signals. In this conventional technique, the GPS antenna is designed in advance to have a high sensitivity in the upward direction (that is, the elevation angle of 90 °), and the VICS antenna is designed to have a high sensitivity in the horizontal direction. It does not take into account the antenna gain in the case of installation.

As another conventional technique, a metal plate is arranged on the ground plate side of the microstrip antenna with a distance of λ / 4 to λ / 8 (where λ is the wavelength of the radio wave used) from the ground plate. Therefore, the zenith direction (elevation angle 9
There is one in which the reception sensitivity in the 0 ° direction is higher than that in the low elevation angle direction (Japanese Patent Laid-Open No. 2000-244229). But,
It is not shown that a shared antenna that receives a plurality of frequencies has a desired gain in any frequency band.

In view of the above points, it is an object of the present invention to simultaneously improve the gain in a specific direction of a plurality of antenna elements that operate in a plurality of frequency bands.

[0005]

In order to achieve the above object, the invention according to claim 1 is characterized in that the first surface is provided on the ground plate.
A first antenna element and a second antenna element operating in a band including frequency
A multi-frequency shared antenna provided with a second antenna element that operates in a band including a frequency, wherein a reflective conductor plate is provided on the back side of the ground plate in parallel with the back face at a predetermined distance d, and the predetermined The distance d is ((2m−1) /4−0.1) λ ₁ ≦ for the respective wavelengths λ ₁ and λ ₂ in the free space of the first frequency and the second frequency and the natural numbers m and n. d ≦ ((2m-
1) /4+0.1) λ ₁ and ((2n−1) /4−0.1) λ ₂ ≦ d ≦ ((2n−
It is characterized in that 1) /4+0.1) λ ₂ is satisfied.

According to the present invention, both the first antenna element and the second antenna element are radiated from the antenna element and the reflection conductor plate by the reflection conductor plate provided at a predetermined distance d from the ground plate. Since the reflected wave from is in phase with the front direction of the antenna, that is, with the elevation angle of 90 °, it is possible to simultaneously improve the gain in the front direction of either antenna element.

According to the second aspect of the invention, the first antenna element operating in the band including the first frequency and the second antenna element operating in the band including the second frequency are provided on the surface of the ground plate. A multi-frequency shared antenna provided,
A reflective conductor plate is provided on the back surface side of the ground plate in parallel with the back surface at a predetermined distance d, and the predetermined distance d has respective wavelengths λ ₁ , in the free space of the first frequency and the second frequency,
With respect to λ ₂ and natural numbers m and n, ((2m−1) /4−0.1) λ ₁ ≦ d ≦ ((2m−
1) /4+0.1) λ ₁ and (n / 2-0.1) λ ₂ ≦ d ≦ (n / 2 + 0.1) λ ₂ are satisfied.

According to this invention, the radiation wave from the first antenna element and the reflection wave from the reflection conductor plate are directed toward the front of the antenna, that is, the elevation angle, by the reflection conductor plate provided at a predetermined distance d from the ground plate. Since the same phase is obtained in the 90 ° direction, the gain in the front direction can be improved, and the radiation wave from the second antenna element and the reflection wave from the reflection conductor plate have opposite phases in the front direction of the antenna element. The gain in the front direction is reduced, and the gain in the direction of the elevation angle of 60 ° can be improved.

Further, as in the invention described in claim 3,
A first antenna element operating in a band including the first frequency, a second antenna element operating in a band including the second frequency, and a third antenna element operating in a band including the third frequency on the surface of the ground plate; Is a multi-frequency shared antenna, wherein a reflection conductor plate is provided on the back side of the ground plate in parallel with the back face at a predetermined distance d, and the predetermined distance d is a free space having first to third frequencies. At wavelengths λ ₁ , λ ₂ , λ ₃ and natural numbers m, n, k at ((2m−1) /4−0.1) λ ₁ ≦ d ≦ ((2m−
1) /4+0.1) λ ₁ and ((2n−1) /4−0.1) λ ₂ ≦ d ≦ ((2n−
1) /4+0.1) λ ₂ and (k / 2−0.1) λ ₃ ≦ d ≦ (k / 2 + 0.1) λ ₃ are satisfied, the first and second antenna elements are The gain in the elevation angle direction of 90 ° and the gain of the third antenna element in the elevation angle direction of 60 ° can be simultaneously improved.

In this case, the effect of improving the gain of each antenna element can be enhanced by making the area of the reflective conductor plate larger than the area of the ground plate as in the invention of claim 4. it can.

[0011]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described in detail with reference to the drawings. As shown in the perspective view of FIG. 1, the multi-frequency shared antenna 1 according to the present embodiment has a surface of a ground plate 4 as an antenna substrate having a size of 40 mm × 40 mm.
A GPS antenna element 10 that receives a GPS signal in the 575 GHz band, a VICS antenna element 20 that receives a VICS signal in the 2.4997 GHz band, and an ETC antenna element 30 that sends and receives an ETC (Electronic Toll Collection) signal in the 5.8 GHz band. Are formed. these,
In the GPS antenna element 10, the VICS antenna element 20, and the ETC antenna element 30, the radiating elements 11, 21, 31 are arranged on the surfaces of the dielectric layers 12, 22, 32 formed on the surface of the ground plate 4, respectively. In the following, the wavelengths of the respective signals in free space are the wavelength λ _{1 of the} GPS signal λ ₁ = 190 (mm) and the wavelength λ _{2 of the} VICS signal λ ₂ = 122.
(Mm) and the wavelength of the ETC signal is λ ₃ = 52 (mm).

Further, a reflective conductor plate 5 having a size of 200 mm × 200 mm is arranged on the back surface side of the ground plate 4, that is, the back surface side of the multi-frequency shared antenna 1, at a distance d from the ground plate 4. When the ground plate 4 is projected vertically on the reflective conductor plate 5, the projection surface is arranged so as to be completely included in the reflective conductor plate 5.

Here, the relationship between the antenna gain and the distance d between the ground plate 4 and the reflective conductor plate 5 will be described by taking the GPS antenna element 10 as an example. 2, FIG. 3, and FIG.
Directivity in the case of only the GPS antenna element 10 not using the reflective conductor plate 5, in the case of d = 0.25λ ₁ = 48 (mm), and in the case of d = 0.5λ ₁ = 95 (mm) It is a diagram showing the measured value of.

By placing the reflection conductor plate 5 at the position of d = 0.25λ ₁ , the radiation wave from the antenna and the reflection conductor plate 5 can be obtained.
It can be seen that the reflected wave from is in phase with the elevation direction of 90 ° in the front direction and the gain in the front direction is improved (see FIG. 3).

Further, FIG. 5 shows the GPS antenna element 10
In, the result of measuring the periodic change of the gain in the direction of the elevation angle of 90 ° with respect to the distance d is shown. From FIG. 5, 2-3 dB
It is in the range of d = 0.15λ to 0.35λ and d = 0.65λ to 0.85λ that the gain of i or more, that is, the effect of improving the gain in the front direction is obtained. It is considered that the change appears periodically every half wavelength.

From the above, the distance d between the ground plate 4 and the reflective conductor plate 5 capable of improving the gain in the direction of elevation angle of 90 ° is
Wavelength λ and natural number m of the target radio wave in free space
For (m = 1, 2, ...), ((2m−1) /4−0.1) λ ≦ d ≦ ((2m−1)
/4+0.1)λ can be set.

Therefore, the wavelengths λ _{1 of} different frequency bands,
In order to simultaneously improve the gain in the direction of the elevation angle of 90 ° for the radio wave of λ ₂ , for natural numbers m, n (m, n = 1, 2, ...),

[0018]

## EQU1 ## ((2m-1) /4-0.1) λ ₁ ≤d≤
((2m-1) /4+0.1) λ ₁ and

[0019]

## EQU2 ## ((2n-1) /4-0.1) λ ₂ ≤d≤
The distance d may be determined so as to satisfy ((2n−1) /4+0.1) λ ₂ .

On the other hand, the reflective conductor plate 5 is placed at the position of d = 0.5λ.
When, is placed, the radiated wave and the reflected wave have opposite phases in the front direction, so the gain in the front direction decreases and the gain increases in the elevation angle direction of 60 ° (see FIG. 4).

Therefore, the distance d between the ground plate 4 and the reflection conductor plate 5 capable of improving the gain in the direction of elevation angle of 60 ° is the wavelength λ ₃ of the target radio wave in the free space and the natural number k.
For (k = 1, 2, ...),

[0022]

Equation 3] _{(k / 2-0.1) λ 3 ≦} d ≦ (k / 2 + 0.1) it can be determined within a region defined by a lambda _3.

By the way, the GPS antenna and VICS
Since the GPS satellites and radio wave beacon antennas, which are the radio wave sources thereof, are present in the zenith direction of the vehicle (that is, in the elevation angle 90 ° direction), the antenna must have a large gain in the elevation angle 90 ° direction during operation. Further, since the ETC antenna communicates when the antenna of the toll gate, which is a radio wave source, has an elevation angle of about 60 ° from the vehicle, it is necessary to have a large gain at an elevation angle of 60 °.

From the above, the GPS signal (1.575
GHz, λ ₁ = 190 mm), VICS signal (2.49)
97 GHz, λ ₂ = 122 mm) and the ETC signal (5.8 GHz, λ ₃ = 52 mm) can be simultaneously received. A range of a distance d in which the gain of the GPS antenna element 10 and the VICS antenna element 20 in the direction of an elevation angle of 90 ° is improved, and a range of a distance d in which the gain of the ETC antenna element 30 is improved in the direction of an elevation angle of 60 °, which are defined by Expression 3. Is indicated by an arrow in FIG.
In the figure, each antenna gain becomes maximum near the midpoint of each arrow range.

From this, the multi-frequency common antenna 1 is GPS
2 of the antenna element 10 and the VICS antenna element 20
In the case of one antenna element, if the reflective conductor plate 5 is arranged at the positions where d is about 40 mm and 140 to 164 mm, the gains of both antenna elements in the elevation angle 90 ° direction can be simultaneously improved.

Further, the multi-frequency shared antenna 1 includes the GPS antenna element 10, the VICS antenna element 20 and the ETC.
When the antenna element 30 includes three antenna elements,
If the reflective conductor plate 5 is arranged at a position where d is about 155 mm,
GPS antenna element 10 and VICS antenna element 2
0 in the direction of the elevation angle of 90 ° and the ETC antenna element 30
It is possible to simultaneously improve the gain in the direction of the elevation angle of 60 °. In this case, the optimum position where the desired gain is obtained may exist near d = 30 mm. However, as shown in FIG. 5, in the range where d is smaller than 0.15λ, the gain drastically changes depending on the size of d. It is necessary to pay particular attention to the placement of antenna elements.

As described above, in a multi-frequency shared antenna in which a plurality of antenna elements having different operating frequencies are on the same substrate (ground plate), the above equations (1) to (3) considering the periodicity of each wavelength are simultaneously satisfied. By arranging the reflective conductor plate at the position on the back side of the antenna to be used, it is possible to improve the gain of all the antenna elements in the necessary directions,
For example, even an antenna device that is miniaturized to be placed in a vehicle compartment can compensate for a decrease in gain due to the influence of the windshield around the antenna, a metal member of the vehicle body, and the like, and a good gain as an on-vehicle antenna can be secured.

The reflective conductor plate 5 may be a conductive flat plate having a predetermined area, and a metal inside the vehicle, that is, below the dashboard, such as a car audio equipment casing or a vehicle body reinforcement plate, may be used. You can

[Brief description of drawings]

FIG. 1 is a perspective view showing an overall configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing the directivity in the elevation direction of a GPS antenna element.

FIG. 3 is d = 0.25λ on the back side of the GPS antenna element
It is a figure showing the directivity in an elevation angle direction when a reflective conductor plate is arrange | positioned at the position of.

FIG. 4 is a diagram showing directivity in an elevation direction when a reflective conductor plate is arranged at a position of d = 0.5λ on the back side of the GPS antenna element.

FIG. 5 is a diagram showing a relationship between a gain of a GPS antenna element in the direction of an elevation angle of 90 ° and an arrangement position d of a reflective conductor plate.

FIG. 6 GPS antenna, VICS antenna and ET
It is a figure which shows the position of the reflective conductor board which can obtain each desired gain of C antenna.

[Explanation of symbols]

1 ... Multi-frequency shared antenna, 10 ... GPS antenna element,
20 ... VICS antenna element, 30 ... ETC antenna element, 11, 21, 31 ... Radiating element, 12, 22, 32 ...
Dielectric layer, 4 ... Ground plate (antenna substrate), 5 ... Reflective conductor plate.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shinji Fukui             14 Iwatani Shimohakaku-cho, Nishio-shi, Aichi Stock Association             Company Japan Auto Parts Research Institute (72) Inventor Koji Taketomi             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO (72) Inventor Akihiko Hayashi             1-1, Showa-cho, Kariya city, Aichi stock market             Inside the company DENSO F-term (reference) 5J045 AA05 AA21 DA08 DA10 FA08                       NA01 NA02

Claims (4)

[Claims] 1. A multi-frequency shared antenna having a surface of a ground plate provided with a first antenna element operating in a band including a first frequency and a second antenna element operating in a band including a second frequency. A reflective conductor plate is provided on the back surface side of the ground plate in parallel with the back surface at a predetermined distance d, and the predetermined distance d is the respective wavelengths λ ₁ , λ in the free space of the first frequency and the second frequency. ₂ and natural numbers m and n
With respect to ((2m−1) /4−0.1) λ ₁ ≦ d ≦ ((2m−
1) /4+0.1) λ ₁ and ((2n−1) /4−0.1) λ ₂ ≦ d ≦ ((2n−
A multi-frequency shared antenna, characterized in that it satisfies 1) /4+0.1) λ ₂ . 2. A multi-frequency shared antenna having a surface of a ground plate provided with a first antenna element operating in a band including a first frequency and a second antenna element operating in a band including a second frequency. A reflective conductor plate is provided on the back surface side of the ground plate in parallel with the back surface at a predetermined distance d, and the predetermined distance d is the respective wavelengths λ ₁ , λ in the free space of the first frequency and the second frequency. ₂ and natural numbers m and n
With respect to ((2m−1) /4−0.1) λ ₁ ≦ d ≦ ((2m−
1) /4+0.1) λ ₁ and (n / 2-0.1) λ ₂ ≦ d ≦ (n / 2 + 0.1) λ ₂ are satisfied. 3. A first antenna element operating in a band including a first frequency, a second antenna element operating in a band including a second frequency, and a second antenna element operating in a band including a third frequency on a surface of a ground plate. A multi-frequency shared antenna provided with an antenna element of No. 3, wherein a reflective conductor plate is provided on the back surface side of the ground plate in parallel with the back surface at a predetermined distance d, and the predetermined distance d is from the first to the first. Wavelengths λ ₁ , λ ₂ , λ ₃ in free space of three frequencies, and a natural number m,
For (n, k), ((2m-1) /4-0.1)? ₁ ? d? ((2m-
1) /4+0.1) λ ₁ and ((2n−1) /4−0.1) λ ₂ ≦ d ≦ ((2n−
1) /4+0.1) λ ₂ and (k / 2−0.1) λ ₃ ≦ d ≦ (k / 2 + 0.1) λ ₃ are satisfied. 4. The multi-frequency shared antenna according to claim 1, wherein an area of the reflective conductor plate is larger than an area of the ground plate.