JPH0795652B2 - Horn antenna - Google Patents

Description

TECHNICAL FIELD The present invention relates to a horn antenna used in a microwave band parabolic antenna or the like.

[Prior Art] A horn antenna is widely used as a primary radiator such as a microwave parabolic antenna. The conical horn antenna is excited by the TE ₁₁ mode wave, which is the fundamental mode of a circular waveguide. In this case, the beam width of the E surface is narrower than the beam width of the H surface and higher than the side lobes of the E surface. In addition, the cross polarization level in the 45 ° plane is also high, and in the case of circular polarization, the elliptic polarization ratio increases when it is displaced from the front direction.

In order to solve such an inconvenience, a multimode horn antenna or a hybrid mode horn antenna such as a corrugated horn antenna has been used.

[Problems to be Solved by the Invention] In the conventional multimode horn antenna, the TE ₁₁ mode wave which is the fundamental mode of the circular waveguide and the TM ₁₁ mode wave which is one of the higher modes are used for the aperture plane. In order to be in phase with each other, a stepped discontinuity is provided in the circular waveguide, a dielectric sleeve is loaded on the inner wall of the horn, multiple flares are used, iris and flare. Although many types such as those using and have been proposed, all of them have problems such as time-consuming processing and lack of stability.

On the other hand, the corrugated horn antenna has thin fins in the shape of comb teeth on the inner wall of the circular waveguide to propagate the EH ₁₁ mode wave which is one of the hybrid modes. When λ / 4 (λ = wavelength), the axially symmetric beam and cross polarization characteristics are good, but the antenna structure becomes complicated and the cost becomes high.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a horn antenna having good antenna characteristics while having a sufficiently simple structure.

[Means for Solving the Problems] The electrolytic distribution on the aperture plane of the EH ₁₁ mode wave has a Gaussian distribution in the radial direction and an axially symmetric shape that does not change in the circumferential direction. That is, in the corrugated horn, E _θ , H
The distribution of _θ is symmetric. In the waveguide loaded with the dielectric film, the tangential components E _θ and E _Z of the electric field are 0 at the inner wall (r = b) of the waveguide, but H _θ and H _Z are present.

FIG. 5 shows the characteristics of a normal horn antenna. In the case of a normal horn antenna in the state of "r = b" where the inner wall of the waveguide is not subjected to any special treatment, "Y / b = 1.0" as shown in the figure.
Then, “E _θ = 0”, which is not symmetrical with H _θ . Therefore, in order to make the distribution of E _θ and H _θ symmetrical as in a corrugated horn, E _θ should be raised to the same level as H _θ , or
Alternatively, it is possible to reduce H _θ to the same level as E _θ .

FIG. 6 shows the concept of the electric field E _θ generated on the waveguide wall. As shown in the figure, when H _Z exists on the tube wall of the waveguide, a current density J is generated and flows in the circumferential direction. If the tube wall is a perfect conductor (R = 0), “E _θ = 0”. However, if a resistive film is formed on the tube wall, a potential difference is generated there and an electric field E _θ is induced in the circumferential direction.

The present invention takes advantage of this point by forming a dielectric film on the inner wall of the antenna formed of a conductor with a resistive film interposed therebetween, and inducing an electric field E _θ on the waveguide wall to generate E _θ and H _θ. The distribution of is symmetric.

[Operation] According to the above, a horn antenna having an axisymmetric beam and good cross polarization characteristics can be obtained without a complicated structure.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the structure of one embodiment. FIG. 1 (A) shows an axial cross section, and FIG. 1 (B) shows an opening cross section taken along line I-I of FIG. 1 (A). Indicates. In the figure, 11 is a conical horn antenna made of a conductor, 12 is a resistor film mounted on the entire inner wall of the conical horn antenna 11, and 13 is a resistor film.
It is a dielectric film which is also mounted on the entire inner wall of the conical horn antenna 11 with 12 interposed.

With this structure, the tangential components E _θ and E _Z of the electric field on the tube wall of the conical horn antenna 11 are 0, but H _θ and H _Z are present. When this H _Z exists, a current flows in the opening of the conical horn antenna 11 in the circumferential direction. At this time, since the conical horn antenna 11 is provided with the resistor film 12 as described above, a potential difference is generated,
A circumferential electric field E _θ is induced. Therefore, the resistor film 12
By properly selecting the film thickness of and the resistance value is set, “E _θ ≈H _θ ” can be obtained. This allows
The TE mode and TM mode in the waveguide have the same amplitude and are symmetrical, the beam widths of the E and H planes are made equal, and the cross polarization characteristics are significantly improved by adding a circular polarization generator. You can

Further, the dielectric film 13 can change the surface impedance by changing its thickness, and can control the size of H _Z.

FIG. 2 shows the directional characteristics of the above embodiment. Frequency 12 GHz, Conical horn antenna 11 opening inner diameter 75 m
m, the resistor film 12 is made of ferrite and has a thickness of 1 mm, and the dielectric film 13 is made of polyethylene and has a thickness of 3 mm. The Z direction is the front and the directivity angle is 0 °. When the relative electric field strength was measured, the directivities of the E and H planes were almost symmetrical as shown in the figure. This is an improvement of several dB within the range of ± 50 °, as compared with the case of only the conical horn antenna 11 in which the resistor film 12 and the dielectric film 13 are not attached.

The following FIG. 3 shows the structure of another embodiment.
FIG. 3A is a sectional view in the axial direction, and FIG. 3B is the same sectional view.
3 shows an opening cross section taken along line III-III of FIG. In the figure, 21 is a pyramidal horn antenna made of a conductor, 22 is a resistor film mounted on a pair of facing inner walls of the pyramidal horn antenna 21, and 23 is also a pyramid with the resistor film 22 interposed. A horn antenna (21) is a dielectric film attached to a pair of facing inner walls of the horn antenna (21).

With this structure, the tangential components E _X and E _Z of the electric field on the tube wall of the pyramidal horn antenna 21 are 0,
E _X and E _Z come to exist. When this H _Z exists, a current flows in the circumferential direction in the opening of the pyramidal horn antenna 21.
At this time, the pyramidal horn antenna 21 for as resistor film 22 mentioned above is provided, a potential difference induces circumferential direction of the electric field E _X. Therefore, by appropriately selecting the film thickness of the resistor film 22 and setting the resistance value thereof, it is possible to obtain “E _X ≈
H _X ". As a result, the TE mode and the TM mode in the waveguide have the same amplitude and are symmetric, and the beam widths of the E plane and the H plane are made equal. Therefore, from the right side of FIG. 3 (A), by generating an electric field of E _X = H _X by the circular polarization generator, the horn antenna is excited by circular polarization, and radio waves with good cross polarization characteristics are obtained. Can be emitted.

Although the pyramidal horn antenna 21 is used as the horn antenna here, the same effect can be obtained with the fan-shaped horn antenna, and the description thereof will be omitted.

The next FIG. 4 also shows the structure of another embodiment. FIG. 4 (A) is a cross section in the axial direction, and FIG. 4 (B) is a line IV-IV of FIG. 4 (A). 3 shows an opening cross section along. 31 in the figure
Is a conical horn antenna made of a conductor, 32 is a pair of resistor films mounted so as to face the inner wall of the conical horn antenna 31, and 33 is also a conical horn antenna 31 with the resistor film 32 interposed. Is a pair of dielectric films mounted so as to face the inner walls of the.

With such a structure, the tangential components E _X and E _Z of the electric field on the tube wall of the conical horn antenna 31 are 0,
H _X and H _Z come to exist. When H _Z exists, a current flows in the opening of the conical horn antenna 31 in the circumferential direction.
At this time, since the conical horn antenna 31 is provided with the resistor film 32 as described above, a potential difference is generated and the electric field E _{X in the} circumferential direction is induced. Therefore, “E _X ≈H _X ” can be obtained by appropriately selecting the film thickness of the resistor film 32, setting the resistance value, and supplying power in the TE ₁₁ mode, for example.

It is also possible to connect another antenna such as a corrugated horn antenna to this horn antenna and use it as a symmetrical mode generator.

[Effects of the Invention] According to the present invention as described in detail above, since the dielectric film is formed on the inner wall of the antenna formed of the conductor with the resistor film interposed, the structure is sufficiently simple and wide. It has an axially symmetric beam and good cross polarization characteristics over the frequency band, and is a great frequency reuse technology using two orthogonal polarizations, linear polarization or circular polarization, used in satellite communications and satellite broadcasting. A horn antenna capable of obtaining the effect can be provided.

[Brief description of drawings]

FIG. 1 (A) is a sectional view showing the structure of one embodiment of the present invention,
FIG. 1 (B) is a sectional view of the opening along the line I-I of FIG. 1 (A), and FIG. 2 is a directivity characteristic diagram of the horn antenna of the first head,
3A is a sectional view showing the structure of another embodiment of the present invention, FIG. 3B is a sectional view taken along the line III-III in FIG. 3A, and FIG. ) Is a sectional view showing the structure of another embodiment of the present invention, FIG. 4 (B) is an opening sectional view taken along the line IV-IV in FIG. 4 (A), and FIGS. 5 and 6 show the present invention. It is a figure for showing the concept of. 11,31… Conical horn antenna, 12,22,32… Resistance film, 1
3,23,33 ... Dielectric film, 21 ... Pyramidal horn antenna.

Claims (4)

[Claims] 1. A dielectric film is formed on an inner wall of a horn-shaped antenna made of a conductor, with a resistor film interposed therebetween, and a tangential component (E _θ ) of an electric field and a tangential component (H _θ ) of a magnetic field are substantially equal to each other. Therefore, the horn antenna is characterized in that the resistance value and size of the resistor film and the dielectric constant and size of the dielectric film are determined. 2. The horn antenna is a conical horn antenna, and the dielectric film with the resistor film interposed is formed on the entire inner wall of the antenna.
The described horn antenna. 3. The horn antenna is a quadrangular pyramid horn antenna, and the dielectric film with the resistor film interposed is formed on the opposing surfaces of the inner wall of the antenna. Horn antenna. 4. The horn according to claim 1, wherein the horn antenna is a conical horn antenna, and the dielectric films with the resistor film interposed are formed on opposite surfaces of an inner wall of the antenna. antenna.