JP3877196B2 - antenna - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an antenna having a function of shielding or enhancing electromagnetic waves having a predetermined frequency depending on purposes.
[0002]
[Prior art]
With the spread of mobile communication and the like, there is a concern about electromagnetic interference and the like, and it is necessary to shield specific electromagnetic waves depending on places such as railway vehicles, route buses, and hospitals. In order to prevent electromagnetic waves from entering the inside of a building or vehicle, an electromagnetic shielding material is sometimes used for the wall surface.
[0003]
[Problems to be solved by the invention]
However, adding a shielding characteristic to a window or the like impairs the function of the window intended for lighting. For this reason, invasion of electromagnetic waves from the window is inevitable. Even if it is covered with a shielding material, the shielding material does not have frequency selectivity, and electromagnetic waves having a frequency required for information communication are simultaneously shielded. Furthermore, even in the case where it is necessary to increase the sensitivity in communication, there have been almost no cases where an enhancement function is added to a wall surface, a window or the like.
[0004]
An object of the present invention is to provide an antenna having a function of shielding or enhancing an electromagnetic wave having a specific frequency without depending on the polarization plane of the electromagnetic wave, by being attached to a wall or window of a building or a vehicle. .
[0005]
[Means for Solving the Problems]
The antenna of the present invention is characterized in that an antenna element having a closed loop shape made of a conductive material and having a circular shape, an elliptical shape, and an N-square shape (N is an integer of 3 or more) is formed on an insulating substrate. .
[0006]
The antenna of the present invention is characterized in that the effective length around the antenna element in consideration of the dielectric constant of the substrate is substantially equal to one wavelength of the electromagnetic wave at the operating frequency.
[0007]
In the antenna of the present invention, when the line width w of the antenna element satisfies the relationship represented by w ≦ 4 · λ · e ^−4.5 with respect to the effective length λ around the antenna element, a shielding function is obtained, and w> 4 When the relationship shown by λ · e ^−4.5 is satisfied, an enhancement function is obtained.
[0008]
In the antenna of the present invention, when the distance between the centers of the nearest antenna elements having the same operating frequency is defined as the antenna element interval, the antenna elements satisfy the relationship of λ / π ≦ d ≦ 5 · λ / π. Has been placed.
[0009]
In the antenna of the present invention, the antenna element has a single or a plurality of sizes and has a single or a plurality of operating frequencies.
[0010]
Further, a light-transmitting material can be used for the substrate, or a light-transmitting material can be used for the antenna element.
[0011]
In the antenna of the present invention, a material satisfying a resistivity ρ of ρ ≦ 10 ⁻² Ω · cm is used for the antenna element. This is because if the resistivity value is too large, the phase when the antenna element receives and re-radiates the radio wave deviates from the optimum value, and the effect of shielding or enhancement becomes small.
[0012]
Furthermore, the antenna according to the present invention can also be configured with a substrate made of a wall surface member including a wallpaper member of a building.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0014]
The antenna of the present invention is composed of a parasitic antenna whose feeding point is short-circuited and an antenna element utilizing both properties of a loop antenna. The received radio wave is re-radiated from a parasitic antenna whose feeding point is short-circuited. The phase of the re-radiated radio wave depends on the line width of the antenna, and can be in phase with or opposite to the incident wave, unlike the phase of the received radio wave. At the rear of the antenna, the transmitted wave of the incident wave and the re-radiated wave are combined, so if the phases are opposite to each other, the antenna exhibits a shielding effect, and if the transmitted wave of the incident wave and the re-radiated wave are in phase, , An enhancement effect will be shown.
[0015]
That is, when the effective length around the antenna element is λ, an antenna satisfying the expression (1) has a shielding function, and an antenna satisfying the expression (2) has an enhancement function.
[0016]
w ≦ 4 ・ λ ・ e ^-4.5 (1)
w> 4 · λ · e ^-4.5 (2)
[0017]
The degree of each of the antenna shielding effect and enhancement effect is determined by the balance between the antenna transmitted wave and the antenna re-radiated wave. The balance characteristic between the antenna transmitted wave and the antenna re-radiated wave depends on the antenna element interval d defined by the distance between the centers of the nearest antenna elements whose operating frequencies are equal to each other, and the line width w. It is possible to adjust within the range shown.
[0018]
λ / π ≦ d ≦ 5 · λ / π (3)
[0019]
In the plane of the shorted loop antenna, since the antenna has no directionality, the antenna has no polarization dependency in the plane.
[0020]
Further, since the operating frequency of the antenna is determined by the loop size, it is possible to operate in a plurality of frequency bands by coexisting antenna elements having a plurality of loop sizes.
[0021]
FIG. 1 is a plan view showing a basic configuration of an antenna according to the present invention. In FIG. 1, an antenna 10 is configured by arranging a plurality of loop-shaped antenna elements 12 on an insulating substrate 11. A plurality of antenna elements 12 intersect with each other at an angle of 60 degrees, and a plurality of antenna elements 12 are arranged so that their centers coincide with each intersection of a group of straight lines forming a plurality of equilateral triangles. As shown in FIG. 1, the antenna element interval is d.
[0022]
FIG. 2 is a plan view of the antenna according to the embodiment of the present invention. In FIG. 2, the antenna 20 is formed with two types of antenna elements 22 and 23 on a glass epoxy substrate 21. The antenna elements 23 having a radius (r ₂ ) of 25 mm and a line width (w ₂ ) of 0.5 mm are arranged with an antenna element interval (d ₂ ) of 100 mm. Another type of antenna element 22 has a radius (r ₁ ) of 53 mm, a line width (w ₁ ) of 1.0 mm, and is arranged with an antenna element interval (d ₁ ) of 200 mm. As shown in FIG. 2, the antenna element 22 is arranged concentrically with the antenna element 23.
[0023]
The antenna 20 satisfies the expressions (1) and (3) according to the geometric values.
[0024]
FIG. 6 is a diagram showing a measurement system for evaluating the pass characteristics of each antenna. An antenna sample 4 is inserted between the transmitting antenna 1 and the receiving antenna 2 to measure pass characteristics. The direct connection between the transmitting antenna 1 and the receiving antenna 2 was used as a reference when measuring the pass characteristics.
[0025]
FIG. 3 is a diagram showing the pass characteristics of the antenna 20 shown in FIG. According to FIG. 3, the antenna 20 according to the present embodiment has a shielding effect in two frequency bands of a center frequency of 780 MHz and 1610 MHz. In other frequency bands, electromagnetic waves are transmitted, and it can be seen that the antenna 20 functions as a dual-frequency shield antenna. Considering the relative dielectric constant of the glass epoxy substrate 21 used, the effective perimeter of the loop antenna elements 22 and 23 corresponds to approximately one wavelength of the operating radio wave for each of the two frequencies where the shielding effect is obtained. ing. Since the loop-shaped antenna elements 22 and 23 are employed, the characteristics do not change even if the antenna 20 is rotated in the plane.
[0026]
FIG. 4 is a plan view of an antenna according to another embodiment of the present invention. In FIG. 4, the antenna 30 has an antenna element 32 having a radius (r) of 12 mm and a line width (w) of 6 mm formed on a glass substrate 31 with an antenna element interval (d) of 62 mm.
[0027]
It can be seen that the antenna 30 satisfies the equations (2) and (3) according to the respective geometric values, and exhibits an enhancement function as shown in FIG.
[0028]
FIG. 5 is a diagram showing the pass characteristic of the antenna 30 shown in FIG. 4 measured using the measurement system of FIG. The passing characteristic when the antenna sample 4 is inserted is measured with the reference value (0 dB) when there is no antenna sample 4. According to FIG. 5, the antenna 30 according to the present embodiment shows an enhancement effect of about 6 dB at a single frequency of about 4300 MHz. Regarding the operating frequency, the effective perimeter of the loop-shaped antenna element 32 is substantially equal to one wavelength of the operating radio wave. Since the loop-shaped antenna element 32 is employed, this characteristic does not change even if the antenna 30 is rotated in the plane.
[0029]
Note that the loop-shaped antenna element is not limited to a circular shape, and may have an elliptical shape or an arbitrary polygonal shape for manufacturing, aesthetic reasons, or the like.
[0030]
In many cases, copper and aluminum are used for the antenna element. The resistivity ρ of copper or aluminum at room temperature is about 1.5 × 10 ^{−6 to} 3.5 × 10 ⁻⁶ Ω · cm, and the resistivity according to claim 10, ρ ≦ 10 ⁻ The condition of ² Ω · cm is satisfied. If the resistivity value is too large, the phase of the re-radiated radio wave will deviate from the optimum value, and the effect of shielding or enhancement will be reduced.
[0031]
Furthermore, by using a light-transmitting material such as glass as the substrate and using a transparent conductive material such as ITO for the antenna element, the shielding effect or the enhancement effect can be obtained without impairing the light transmittance. An antenna having the same can be realized. Even if such an antenna is attached to a window, lighting is not hindered.
[0032]
Similarly, the antenna according to the present invention can be realized by utilizing the advantage that it is a thin plate, and an antenna using a member constituting a wallpaper or a wall surface of a building as a substrate can be realized. An antenna using these materials as a substrate can be incorporated into an inner wall and an outer wall of a building as they are. Buildings and rooms that shield or enhance electromagnetic waves of a specific frequency can be realized, and the electromagnetic waves can be effectively used such as sharing the same line inside and outside the wall surface and improving reception sensitivity.
[0033]
【The invention's effect】
As described above, according to the present invention, an antenna having a function of shielding or enhancing an electromagnetic wave having a specific frequency without depending on the polarization plane of the electromagnetic wave is attached to a wall or window of a building or a vehicle. can get.
[Brief description of the drawings]
FIG. 1 is a plan view showing a basic configuration of an antenna according to the present invention.
FIG. 2 is a plan view of an antenna according to an embodiment of the present invention.
FIG. 3 is a diagram showing pass characteristics of the antenna shown in FIG. 2;
FIG. 4 is a plan view of an antenna according to another embodiment of the present invention.
FIG. 5 is a diagram showing pass characteristics of the antenna shown in FIG. 4;
FIG. 6 is a diagram showing a measurement system for evaluating the pass characteristic of an antenna.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Transmission antenna 2 Reception antenna 3 Network analyzer 4 Antenna sample 10 Antenna 11 Board | substrate 12 Antenna element 20 Antenna 21 Glass epoxy board | substrates 22 and 23 Antenna element 30 Antenna 31 Glass board 32 Antenna element

Claims (9)

An antenna comprising one or more closed loop antenna elements made of a conductive material on an insulating substrate, the effective length λ around the antenna element taking into account the dielectric constant of the substrate Is substantially equal to one wavelength of the electromagnetic wave of the operating frequency, and the line width w of the antenna element satisfies the relationship represented by w> 4 · λ · e ^−4.5 , and the enhancement function for the electromagnetic wave of the operating frequency behind the antenna An antenna comprising:   The antenna according to claim 1, wherein a shape of the antenna element is a circle or an ellipse.   The antenna according to claim 1, wherein the antenna element has an N-gon shape in which N is an integer of 3 or more. The antenna element is arranged so as to satisfy λ / π ≦ d ≦ 5 · λ / π, where d is the distance between the centers of the nearest antenna elements having the same operating frequency. The antenna according to any one of claims 1 to 3 . The antenna according to any one of claims 1 to 4 , wherein the antenna element has a single size or a plurality of sizes. The substrate antenna according to any one of claims 1 to 5, characterized in that it is composed of a light-transmitting material. The antenna according to any one of claims 1 to 6 , wherein the antenna element is made of a light-transmitting and conductive material. The antenna element, the resistivity [rho is, the antenna according to any one of claims 1 to 7, characterized in that it consists of a material that satisfies ρ ≦ 10 ^-2 Ω · cm. The antenna according to any one of claims 1 to 8 , wherein the substrate is configured by a member for a wall surface of a building.

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