JPH04352504A - Wide band directional antenna - Google Patents

Abstract

PURPOSE:To prevent beam width from being narrowed in the high frequency band of a used band. CONSTITUTION:Among radio waves made incident on a reflection plate 1, one part is absorbed by a radio wave absorber 3 stuck to the outer peripheral part of the reflection plate 1, and one part is reflected by the reflection plate 1 and made incident on a feeding part 2. The radio wave absorber 3 is formed by a material which radio wave absorbing rate is gradually increased with the increase of a frequency in the used band.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a broadband directional antenna, and more particularly to a broadband directional antenna that has a reflector and a primary feeder and covers a wide band of several octaves.

0002

2. Description of the Related Art A conventional broadband directional antenna has a feeding section having broadband radiation characteristics and a single reflecting plate formed in a parabolic shape with the feeding section as a focal point.

0003

Generally, in an antenna consisting of a reflector and a power feeding section, the beam half width θ of the beam pattern is expressed by the following equation, where f is the frequency and A is the uniform radiation aperture area.

[0004] θ=2・sin−1(133/f・A)
(1) Therefore, when the radiation aperture area A is constant, the beam width has a characteristic that as the frequency f becomes higher, the beam width becomes narrower. Therefore, when receiving radio waves in a high frequency band within the used band, there is a problem that the beam width becomes too narrow and the detection rate becomes poor.

[0005]

[Means for Solving the Problems] The broadband directional antenna of the present invention is a broadband directional antenna having a reflector and a feeding section, in which radio waves are placed on the outer periphery of the reflector as the frequency increases within the band of use. It is constructed by pasting a radio wave absorber that increases the absorption rate.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a diagram showing one embodiment of the present invention,
It is configured to include a reflector 1, a power feeding section 2, and a radio wave absorber 3 attached to the outer peripheral portion of the reflector 1.

The radio wave incident on the reflector 1 is divided into the radio wave reflected by the reflector 1 and the radio wave reflected by the radio wave absorber 3, which enter the power supply section 2 and are combined to form a pattern. .

By the way, the radio wave absorber 3 is formed of a material whose radio wave absorption rate increases as the frequency increases within the band of use. As a result, as the frequency of radio waves increases, the effective aperture area becomes smaller.
This can prevent the beam width from becoming narrower.

0010

Effects of the Invention As explained above, the present invention provides a reflection plate 1
By pasting a radio wave absorber 3 on the outer periphery of the device, the effective aperture area can be reduced in the high frequency band of the usage band, so the beam width does not become narrow. You can do it like this.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention.

[Explanation of symbols]

1 Reflector 2 Power supply part 3 Radio wave absorber

Claims (1)

[Claims] 1. A broadband directional antenna having a reflector and a power feeding section, wherein a radio wave absorber whose radio wave absorption rate increases as the frequency increases within the band of use is attached to the outer periphery of the reflector. A broadband directional antenna characterized by: