JP2811269B2 - Folded slot antenna with cavity - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relatively small cavity-equipped folded slot antenna suitable for use as an embedded antenna of an automobile.

[0002]

2. Description of the Related Art A conventional slot antenna with a cavity requires a cavity thickness of about 0.25 wavelength when the length of the slot is about 0.5 wavelength with respect to the wavelength of the resonance frequency. It had been. It is well known that, in a linear 0.5-wavelength slot antenna, the impedance measured at the center of the slot antenna is about several hundred ohms.
When power is supplied using an ohmic power supply line, an offset power supply method in which a power supply point is shifted from the center is used.

[0003]

However, according to such a feeding method, fine adjustment of the offset position is required due to the narrow usable frequency band of the linear 0.5-wavelength slot antenna. Further, as described above, the conventional slot antenna with a cavity requires a cavity height of about 0.25 wavelength, which is a negative factor in terms of occupied volume.

Further, the impedance of the linear 0.5-wavelength slot antenna rises to about twice as large as the antenna impedance (about several hundred ohms) in the case of single use by attaching a cavity resonator, and switching is performed. Therefore, there is a problem that the offset amount for this purpose is further increased than that when a single unit is used, and the adjustment of the offset position becomes more delicate.

[0005] It is an object of the present invention to provide a folded slot antenna with a cavity in which the problems of the prior art are improved.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a folded slot antenna with a cavity having one or a plurality of slots formed on one side surface of a conductor wall constituting a cavity. The gist is that a plurality of dielectric layers having different dielectric constants are laminated on the cavity, and a dielectric layer is formed on the non-cavity side of the conductor wall forming the slot.

[0007]

In the slot antenna, dielectric layers having different dielectric constants are arranged in layers inside the cavity, and a dielectric layer is provided on the non-cavity side to form a folded slot antenna. Can be
Further, since the dielectric has a hierarchical structure, the dielectric constant changes slowly and the radio wave radiation efficiency is good.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention shown in the drawings will be described below.
FIG. 1 shows an embodiment of a folded slot antenna with a cavity according to the present invention. In the figure, 1 is a rectangular metal cavity, 2 and 3 are dielectric layers having different dielectric constants formed in the cavity, 4 is a folded slot antenna, 5 is a dielectric layer, and 6 is a feeder. It is.

In this embodiment, for example, the length of each side of the cavity 1 is L3 = 0.5 to 0.6 wavelength, L4 =
0.5 wavelength to 0.6 wavelength, h1 = 0.02 wavelength to 0.0
At four wavelengths, a dimension L is provided at the center of one surface 1a
1, L2, W1, W2, W3, W4, and W5, a folded slot antenna unit 4 is configured. In the cavity 1, a plurality of dielectric layers 2 and 3 are provided with their height dimensions WI and W, respectively.
III is filled so as to have a wavelength of 0.01 to 0.02 wavelength, and a dielectric layer 5 has a height dimension W1 =
It is mounted so as to have a wavelength of 0.01 to 0.02 wavelength.

FIG. 2 shows a specific example in the case where the above embodiment is used in a 1.9 GHz band. In the figure, the metal cavity 1 has L3 = 90 mm, L4 = 90 mm, h1 = 3.
With a size of 2 mm, the folded slot antenna part 4 is L
1 = 0.4 wavelength to 0.6 wavelength, L2 = 0.3 wavelength to 0.
5 wavelengths, W1 = 0.01 wavelength to 0.03 wavelength, W2 =
0.03 wavelength to 0.07 wavelength, W3 = 0.01 wavelength to
0.02 wavelength, W4 = 0.01 wavelength to 0.02 wavelength, W
5 = dimension of 0.01 to 0.02 wavelength.

In the cavity 1, a dielectric layer 2 (relative permittivity εII: 1, height dimension hII: 1.6 mm) and a dielectric layer 3
(Relative permittivity εIII: 4.4 to 4.8, height dimension hIII:
1.6 mm) to form a layer in the height direction.

On the slot antenna forming surface 1a of the cavity 1, a dielectric layer 5 (relative permittivity εI: 4.4-4.
8, height dimension hI: 1.6 mm).

With the above configuration, the folded slot antenna section 4 can provide the feed section 6 near the center in the 1.9 GHz band, and the antenna is thin and small, having a thickness of about 5 mm. It is easy to adjust.

FIG. 3 shows the antenna impedance characteristics of the antenna of FIG. 2, and FIG. 4 shows the antenna directivity characteristics.

[0015]

As described above, according to the folded slot antenna with a cavity of the present invention, a plurality of dielectric layers having different dielectric constants are formed in an appropriate thickness in a hierarchical manner inside the cavity. Since a folded slot antenna having an appropriate size is formed on one surface of the cavity portion and a dielectric layer is provided thereon, a thin slot antenna having a total thickness of 0.03 to 0.06 wavelength can be used. realizable. For example, a cavity-equipped slot antenna having a thickness of about 13 mm at 1 GHz and a thickness of about 6 mm at 2 GHz can be obtained, and a thin antenna with few restrictions upon mounting can be obtained.

In the prior art, since the dielectric material is filled as a single medium inside the cavity resonator, the dielectric constant is large and discontinuous in the free space and the inside of the resonator in the slot portion. Will deteriorate. However, in the present invention, since the dielectric in the cavity has a hierarchical structure as described above, the change in the dielectric constant can be moderated, and the radio wave radiation efficiency improves.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of the present invention.

FIG. 2 is a schematic diagram showing a specific example of the embodiment of FIG. 1;

FIG. 3 is an antenna impedance characteristic diagram of the specific example of FIG. 2;

FIG. 4 is an antenna directivity diagram of the specific example of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal cavity part 2, 3, 5 Dielectric layer 4 Slot antenna part 6 Feeding part

Claims (1)

(57) [Claims] 1. A folded slot antenna with a cavity in which one or more slots are formed on one side surface of a conductor wall constituting a cavity, wherein the cavity has a plurality of dielectric layers having different dielectric constants. A folded slot antenna with a cavity, wherein a dielectric layer is formed on the non-cavity side of the conductor wall forming the slot.