JPS61205006A - Circularly polarized wave antenna - Google Patents

Abstract

PURPOSE:To obtain a circularly polarized wave antenna having a wide band and high gain as a whole by using a meandering line having an axial ratio characteristics of a wide band as well as a hollow waveguide and therefore reducing the feeder loss due to the dielectric loss. CONSTITUTION:The width and the thickness of the opening face of a pill box antenna 2 are referred to W and (t), where the W is larger enough than the wavelength with the (t) set approximately equal to the wavelength. The ratio waves radiated through the slots 4 are set in the normal line direction on the surface of the slot 4, and the space between slots 4 is equal to an integer multiple of lambdag. Here an axis Z is set in the axial direction of the antenna 2, that is, in the traveling direction of the wave reflected by the antenna 2. Thus the space lambdag is equal to the intra-tube wavelength of a rectangular waveguide 3 for reflected waves. The electric power which is not connected by the slots 4 or not radiated through those slots 4 is absorbed by a terminator 7. Here a plane antenna is obtained owing to the large W and small (t). The length of the slot 4 usually equal to the half wavelength of a using frequency. Then the waveguide 3 has an oversize since the width W is larger than the wavelength.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a high-gain antenna for receiving weak radio waves, and in particular has wide-band axial ratio characteristics suitable for receiving circularly polarized radio waves from satellites. The present invention relates to a circularly polarized antenna having a circularly polarized wave antenna.

[Conventional technology]

In recent years, with the start of satellite broadcasting, there has been a strong desire to reliably receive radio waves from satellites using antennas with a simple configuration. Here, when receiving radio waves from a satellite, it is important to have a high gain because the radio waves are extremely weak.

Furthermore, since radio waves from satellites are often circularly polarized waves, the axial ratio characteristics of the receiving antenna need to be wideband accordingly. The antenna for receiving satellite broadcasting is required to be a circularly polarized antenna with high gain and wideband axial ratio characteristics.

Conventionally, the antenna of this article has been used, for example, one having a parabolic configuration, a side view of which is shown in FIG. The antenna with this parabolic configuration includes a parabola 10, a conical horn 1) which constitutes a primary radiation system, a circularly polarized wave generator 12. It is composed of a horn dome 13 and a support column 14 that fixes the positional relationship between this primary radiation system and the parabola 10.

However, since the antenna having such a parabola 10 must face the satellite, snow tends to accumulate on the parabola 10 and the horn dome 13 when installed outdoors. If snow falls on these parts, the gain will decrease and the side ropes will deteriorate. Furthermore, since the parabola 10 is erected at a certain angle, it is easily exposed to wind, causing the antenna to vibrate due to the wind. and,
In order to reduce the vibration of the antenna due to wind pressure,
There is a problem in that the installation work becomes extensive and complicated.

Snow accretion is a solution to this kind of problem.

Planar antennas that take wind pressure into consideration have been developed.

As shown in the front and bottom views of FIGS. 7(a) and 7(b), this planar antenna has a strip line 17 and a radiation source on one side of a double-sided steel laminate 16 in which copper plates are laminated on both sides of a dielectric substrate 15. The element 18 is formed by etching. Therefore, the other side of the dielectric substrate 15 is the copper plate 19.
remains covered. In addition, the dielectric substrate 1
5) formed by etching on one side of 5) I
The J tube line 17 branches off from a receptacle 20 provided at the feed point. Note that 21 is a terminator provided at the tip of the strip line 17.

In the planar antenna constructed in this manner, circularly polarized waves are generated because the radiating elements 1B are provided in pairs, two on each side of the strip line 17, in a V-shape. Since each radiating element 18 has an angle of 45° with respect to the propagation direction of the IJ tube line 17, the pair of radiating elements 18 forming the shape of . The difference is Furthermore, the distance in the propagation direction between the pair of radiating elements 18 forming this V-shape is λg/4.
(where λg is the propagation wavelength), the phase difference is 90°, so circularly polarized waves are generated.

[Problem that the invention seeks to solve]

However, in the planar antenna configured above,
Since the condition is that the phase difference is 90°,
If the frequency changes, the condition of 90° phase difference will no longer be satisfied, which will generate circularly polarized waves with opposite rotation.
Gain reduction also occurs due to unnecessary parts. Furthermore, when the above-mentioned planar antenna is used in a high frequency band, there are problems such as an increase in power feeding loss due to the dielectric substrate and a significant decrease in gain i.

The present invention was made to solve the above problems, and an object of the present invention is to obtain a circularly polarized antenna having high gain and wideband axial ratio characteristics.

[Means for solving problems]

Therefore, the circularly polarized antenna according to the present invention uses a waveguide instead of a double-sided steel-clad laminate (printed circuit board) in which copper plates are laminated on both sides of a dielectric substrate, and has radiating elements arranged in a V-shape. A meander line is used instead of a circularly polarized wave generator.

[Effect]

In a nine-circularly polarized antenna configured in this way, the waveguide is made of a metal conductor, so the feed line loss due to dielectric loss can be reduced, and the meander line is used to generate broadband frequencies. As a result, a circularly polarized antenna with a wide band and high gain can be obtained as a whole.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 1 is a current-type linear antenna placed at point O, 2 is a billbox antenna that is a laboratory cylinder whose focal point is point 0, and 3 is connected to the aperture of billbox antenna 2. It is a rectangular waveguide. 4 is a slot provided on the wall of one side of the rectangular waveguide 30, 5 is a radome that protects this slot 4, and 6 is a meander line etched on the upper surface of the radome 5. T is a terminator that absorbs the power not coupled by the slot 4, and is constituted by a radio wave absorber.

FIG. 2 shows the radiation section in FIG. 1, and each part is the same as in FIG. 1. Here, the width of the aperture of the bill box antenna 2 is W1, and the thickness is t. However, W
is sufficiently larger than the wavelength, and t is about the wavelength. Here, the radio waves radiated from the slot 4 are in the normal direction to the surface of the slot 4. Therefore, the spacing between the slots 4 in two directions is an integral multiple of λg. ζ Here, the two axes are the axial directions of the bill box antenna 2, that is, the traveling directions of reflected waves in the bill box antenna 2, and λg is the wavelength within the rectangular waveguide 3 of this reflected wave. Note that the power that is not coupled by the slot 4, that is, the power that is not radiated, is absorbed by the terminator T. Here, since the width W is large and the thickness t is /J% small, it becomes a planar antenna.

Further, the length of the slot 4 is often used at half the wavelength of the operating frequency, and the width W is larger than the wavelength, so the rectangular waveguide 3 becomes oversized.

FIG. 3 is an upward view of the radome 5, in which the meander line 6 is installed at an angle with respect to two axes. It usually forms an angle of 45° with respect to the two axes. Furthermore, when the linearly polarized waves from each slot 4 pass through the meander line 6, they become circularly polarized waves.

This principle and broadband property are well known.

FIG. 4 is a perspective view of only the radiating part showing another embodiment of the circularly polarized antenna according to the present invention, and the same parts as in FIG. 2 are indicated using the same symbols. In the same figure, radome 5,
The meander line 6 is the same as that in FIG. 1, except that the billbox antenna 2 in the radiating section is replaced with a lens antenna.

8 is a horn, and 9 is a lens made of a dielectric material provided near the aperture surface of the hole 78. By changing the thickness of the dielectric material, this lens 9 can reduce the radio waves from the aperture surface by 2.
Let it be a parallel ray along the axis. The radio waves of this parallel light beam are
As shown in the figure, the radio waves are coupled to the slot 4 and radiated, and the uncoupled radio waves are absorbed in the terminator 7.

FIG. 5 is a schematic configuration diagram showing still another embodiment, in which a rectangular waveguide 3 to which power is fed by the billbox antenna 2 or the lens 9 is provided with metal teeth 22. Since the width W of this rectangular waveguide 30 is sufficiently larger than the wavelength, the guide wavelength λg becomes approximately equal to the free space wavelength λ. Therefore, since the interval between each slot is approximately an integral multiple of the wavelength λ, side lobes are generated in the positive and negative directions of the two axes.

In order to suppress such grating lobes, it is necessary to make the tube wavelength λg smaller than the wavelength λ.

Since the metal tooth profile 22 has such a surface slow wave effect, grating lobes are eliminated. Alternatively, a dielectric material may be applied instead of the metal tooth profile 22.

Further, in the above embodiment, the meander line 6 is shown as a single layer, but it goes without saying that this may also be used in a stacked manner.

〔Effect of the invention〕

As explained above, the circularly polarized antenna according to the present invention uses a meander line having a wide band axial ratio characteristic, so it has a wide band, and because it uses a hollow waveguide, it can reduce the feed line loss. Since the antenna becomes extremely small, it has the excellent effect of providing a circularly polarized antenna that is planar as a whole and has a wide band and high gain.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing an embodiment of the circularly polarized antenna according to the present invention, Fig. 2 is a perspective view of the bill box antenna shown in Fig. 1, Fig. 3 is a plan view of the same, Fig. 4, $5 The figure is a schematic perspective view of main parts showing another embodiment of the circularly polarized antenna according to the present invention, FIG. 6 is a side view showing a conventional circularly polarized antenna, and FIG. 7 (&) I (b) is the same. They are a front view and a bottom view. 1 is a linear antenna, 2 is a bill box antenna, 3 is a rectangular waveguide, 4 is a slot, 5 is a radome, 6 is a meander line, 7 is a terminator, 8 is a horn 9 is a lens, and 22 is a metal tooth shape.

Claims (4)

[Claims] (1) A terminator consisting of an oversized rectangular conduit and a radio wave absorber is connected to the opening surface of a building box antenna consisting of a linear antenna and a parabolic cylinder, and a terminator consisting of an oversized rectangular conduit and a radio wave absorber is connected to the metal side of one side of the rectangular conduit along the tube axis direction. In a planar antenna in which a plurality of slot rows are arranged adjacently in parallel, each row has a plurality of slots arranged at an interval of an integral multiple of the channel wavelength.
A circularly polarized antenna characterized in that a radome made of a dielectric is provided in front of the slot row, and a meander line for generating circularly polarized waves is formed on the radome. (2) The circularly polarized antenna according to claim 1, characterized in that radomes each having a meander line are stacked in multiple layers. (3) The circularly polarized antenna according to claim 1, characterized in that a lens antenna made of a dielectric material is used in place of the bill box antenna. (4) The circularly polarized antenna according to claim 1, wherein a delay circuit made of a dielectric or a metal tooth-shaped structure is provided in an oversized rectangular waveguide.