JPS6130441B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a cosecant beam horn antenna whose radiation power pattern has cosecant beam directivity. Conventionally, dipole array antennas, slot array antennas, and the like have been proposed as antennas having such cosecant beam directivity. However, with any of the conventional antennas, there is a problem that the entire device becomes large in size, and there is also a problem that only a low gain and a narrow band can be obtained. The present invention aims to solve these problems, and aims to provide a compact, high-gain, wide-band cosecant beamhorn antenna. Therefore, in the cosecant beam horn antenna of the present invention, a dielectric material is inserted into the antenna body.
Both sides of the radio wave emission port at the tip of the antenna body are formed with curves corresponding to the permittivity of the dielectric material, so that the radiation power pattern from the radio wave emission port has cosecant characteristics. The curve is characterized by satisfying the following relational expression. r/r ₀ = exp {∫ _p tanθ _i d} Here, tanθ _i = n・sin(θ−)/ {1−n・cos(θ−)} However, r(): From the wave source point to the radio wave emission port Distance to r ₀ : Distance from the wave source point to the radio wave emission port when = 0 : Aperture angle of the antenna n : 1/√ _s ε _s : Permittivity of the dielectric in the antenna body θ : Angle of depression In addition, the present invention In the cosecant beam horn antenna, a dielectric material is inserted into the antenna body, and both sides of the radio wave emission port at the tip of the antenna body are made of the dielectric material so that the radiated power pattern from the radio wave emission port has cosecant characteristics. In order to attenuate side lobes in the directional characteristics, the radio wave is transmitted from the top of the tip of the antenna body to It is characterized by a protruding radio wave absorber that covers the front upper part of the radiation port. r/r ₀ = exp {∫ _p tanθ _i d} Here, tanθ _i = n・sin(θ−)/ {1−n・cos(θ−)} However, r(): From the wave source point to the radio wave emission port Distance to r ₀ : Distance from the wave source point to the radio wave emission port when = 0 : Aperture angle of the antenna n : 1/√ _s ε _s : Permittivity of dielectric material inside the antenna body θ : Angle of depression Below, according to the drawing To explain the embodiments of the present invention, Figs. 1 to 4 show a cosecant beam horn antenna as the first embodiment, Fig. 1 is a perspective view thereof, Fig. 2 is a diagram of its principle, and Fig. 3 ，
FIG. 4 is a perspective view showing a modification thereof. As shown in FIG. 1, a dielectric material 2 is inserted and filled into a fan-shaped horn antenna body 1 made of a copper plate. As the dielectric material 2, a material having low power loss and a small dielectric constant ε _s of about 1.5 to 4 is used, and examples thereof include polytetrafluoroethylene, acrylic, paraffin, and the like. Also, at the tip of the antenna body 1, there is a magnetic field direction H.
A radio wave emission opening 3 is formed along the . Note that a flange 4 for connecting to a waveguide (not shown) is provided at the base end of the antenna body 1. By the way, both sides 3a, 3a of the radio wave emission port 3 along the magnetic field direction H are formed by curved lines that satisfy the following relational expression. r/r ₀ =exp{∫ _p tanθ _i d} ……(1) Here, tanθ _i =n・sin(θ−)/ {1−n・cos(θ−)} ……(2) However, r(): Distance from wave source point O to radio wave emission port 3 r ₀ : Distance from wave source point O to radio wave emission port when = 0: Antenna aperture angle n: 1/√ _s ε _s : Antenna body Dielectric constant θ of dielectric body 2 in antenna 1: angle of depression Next, the design principle of this antenna will be explained using FIG. The design principle of this antenna uses optical vector approximation based on the principle of geometric optics. That is, by utilizing the difference in refractive index between the dielectric material 2 inside the horn antenna body 1 and the free space, the optical vector radiated from the wave source point O is adjusted to each point of the radio wave emission port 3 of the horn antenna body 1. The magnetic field direction H of the radio wave emission port 3 is set so that the radio wave is refracted and radiated in any direction.
This determines the shape of both sides 3a along the radiation area, and by doing so, it is possible to distribute the electric field uniformly in the radiation area, thereby making it possible to obtain a so-called cosecant beam. The details are as follows. First, assuming that reflection can be ignored between the incident energy from the line wave source point O and the radiated energy at a minute portion of the boundary surface of the radio wave emission port 3 of the antenna, the following equation holds. I()d=K・P(θ)dθ ...(3) Here, I() is a function indicating the directivity of the power radiated from the line wave source point O, and P(θ) is the boundary of the radio wave emission port 3. It is a function indicating the directivity of power radiated from a surface at an angle of depression θ, and the constant K satisfies equation (4). K=∫ ¹ ₂ I()d/∫〓 ¹ 〓 ₂ P(θ)dθ
...(4) Also, the range of incidence from the wave source point O is [ ₂ ,
], the energy balance relationship is as follows. ∫ ₂ I()d=K∫〓〓 ₂ P(θ)dθ
...(5) Furthermore, in order to obtain a cosecant beam, P(θ)=cosec ² θ ...(6). Also, from the radiated electric field density inside the H-plane fan-shaped horn antenna main body 1, I() becomes equation (7) from FIG. I()=cos ² {π・[− ( ₁ + ₂ )/2]/( ₁ − ₂ )} …(7) Therefore, from equations (4) to (7), the angle of depression θ is (8 ). θ=tan ^-1 {1/[cotθ ₂ + (cotθ ₁ − cotθ ₂ ) ×∫ ₂ I()d/ ∫ ¹ ₂ I()d]} ...(8) On the other hand, at the refraction point P, Snell According to the law, the following relational expression holds true. tanθi=n・sin(θ−)/{1−n・cos(θ−)}……(9) Here, n is 1/√ _s , and ε _s is the antenna body 1
This is the dielectric constant of the dielectric material 2 within. Therefore, the differential equation satisfied by the curve r() on the boundary surface of the radiation port 3 is 1/r・dr/d=tanθi...(10), and by equations (8) and (9), r() is From equation (10),
Do as in equation (11). r/r ₀ =exp{∫ _p tanθid}...(11) However, r ₀ =r(0) This leads to the above-mentioned equation (1). In this way, two types of antennas were prototyped, each having an aperture angle of 60° and 70° for the radio wave emission port 3. Its dimensions are shown in Table 1. Note that dielectric 2
For this, paraffin was used.

[Table] Table 2 shows the results of obtaining the gain, standing wave ratio, etc. for these prototype antennas No. 1 and No. 2.
The H-plane directivity characteristics 5 and 6 of each antenna are shown by dotted lines in FIGS. 6 and 7.

[Table] From Table 2 and FIGS. 6 and 7 above, it can be seen that this antenna can obtain a significantly higher gain than the conventional omnidirectional antenna, and can also have a cosecant characteristic in its radiation power pattern. In this way, both sides 3a, 3a along the magnetic field direction H of the radio wave emission port 3 at the tip of the antenna main body 1 are curved according to the dielectric constant of the dielectric material 2 [Equations (1), (2) and (9),
(11)] By forming the radio wave emission port 3
The radiation power pattern from the radiation source can be made to have a cosecant characteristic, and as a result, the electric field can be uniformly distributed in the radiation area. In addition, as shown in Fig. 1, this antenna is
Instead of being configured as a plane cosecant beam horn antenna, it can also be configured as an E plane cosecant beam horn antenna, as shown in FIG. That is, in the one shown in FIG. 3, the radio wave emission port 3' is provided along the electric field direction E, and both sides 3'a, 3'a along the electric field direction E have almost the same relational expression as described above. It is formed by a curve that satisfies the following. When designing this E-plane cosecant beam horn antenna, the above-mentioned I() was set to 1 and the acceleration of electrons was taken into consideration. Almost the same. Also in the case of the E-plane cosecant beam horn antenna shown in FIG. 3, an antenna with high gain can be obtained. Note that in FIG. 3, the same reference numerals as in FIG. 1 indicate substantially the same parts. The antenna body can also be a pyramidal horn type antenna body 1', as shown in FIG.
In FIG. 4, the same reference numerals as in FIGS. 1 and 3 indicate substantially similar parts. 5 to 7 show a cosecant beam horn antem as a second embodiment of the present invention.
The figure is a perspective view of the antenna, and FIGS. 6 and 7 are H-plane directivity characteristic diagrams for explaining the operation in comparison with the antenna of the first embodiment.
The same reference numerals as in Figures 3 and 4 indicate almost the same parts. In the antenna of this second embodiment, a radio wave absorber 8 is provided on the antenna main body 1 via a support 7, and this radio wave absorber 8 covers the front upper part of the radio wave emission port 3 from the top of the tip of the antenna main body 1. It is placed so that it protrudes like this. As the radio wave absorber 8, for example, a foamed polystyrene material whose outer surface is coated with graphite is used. In the case of this second embodiment, two types of antennas with the same dimensions as those of the first embodiment were prototyped, but the gain, standing wave ratio, etc. of these prototype antennas No. 1 and No. 2 were determined. The obtained results are shown in Table 3 together with those of the above-mentioned first embodiment without the radio wave absorber 8,
Furthermore, the H-plane directivity characteristics 5' and 6' of each antenna are
It is shown by a solid line in Figure 7. In addition, in FIGS. 6 and 7, the characteristics indicated by two-dot chain lines are design curves.

[Table] From Table 3 and Figures 6 and 7 above, it can be seen that this antenna can obtain a high gain, make its radiated power pattern cosecant, and attenuate the sidelobes in the H-plane directivity characteristic. It can also be seen that it can be kept small. That is,
By installing the radio wave absorber 8 in this manner, it was possible to obtain a high-performance cosecant beam horn antenna with side lobes of approximately -25 dB or less. It goes without saying that this second embodiment can be applied to an H-plane cosecant beam horn antenna as well as an H-plane cosecant beam horn antenna. As detailed above, according to the cosecant beam horn antenna of the present invention, the following effects and advantages can be obtained. (1) It is small, lightweight, and has a simple structure, making it highly economical. (2) Very high aperture efficiency and wideband characteristics. (3) The range of cosecant beam characteristics can be easily changed by design. (4) By installing an appropriate radio wave absorber, side lobes can be significantly attenuated. (5) Since a dielectric material is inserted into the antenna body, there is no need to install a radome to protect against snow and rain. (6) The half-value width of the E-plane directivity characteristic can be easily designed according to the application.

[Brief explanation of the drawing]

1 to 4 show a cosecant beam horn antenna as a first embodiment of the present invention.
The figure is its perspective view, Figure 2 is its principle diagram, and Figures 3 and 4.
The figures are all perspective views showing modifications thereof, and Figs. 5 to 7 show a cosecant beam horn antenna as a second embodiment of the present invention, and Fig. 5 is a perspective view thereof, and Figs. Figure 7 shows H for explaining the effect in comparison with the antenna of the first embodiment.
It is a surface directivity characteristic diagram. 1, 1′...Antenna body, 2...Dielectric material,
3, 3'... Radio wave emission port, 3a, 3a'... Both sides of the radio wave emission port, 4... Flange, 5, 5', 6,
6'... H plane directivity characteristic, 7... Pillar, 8... Radio wave absorber, E... Electric field direction, H... Magnetic field direction.

Claims (1)

[Scope of Claims] 1. A dielectric material is inserted into the antenna body, and both sides of the radio wave emission port at the tip of the antenna main body are arranged so that the radiated power pattern from the radio wave emission port has a cosecant characteristic. A cosecant beam horn antenna formed of a curve corresponding to a dielectric constant, and characterized in that the curve corresponding to the dielectric constant satisfies the following relational expression. r/r ₀ = exp {∫ _p tanθ _i d} Here, tanθ _i = n・sin(θ−)/ {1−n・cos(θ−)} However, r(): From the wave source point to the radio wave emission port Distance to r ₀ : Distance from the wave source point to the radio wave emission port when = 0 : Aperture angle of the antenna n : 1/√ _s ε _s : Permittivity of dielectric material inside the antenna body θ : Angle of depression 2 Inside the antenna body A dielectric material is inserted into the antenna body, and both sides of the radio wave emission port at the tip of the antenna body are formed with curves corresponding to the permittivity of the dielectric material so that the radiation power pattern from the radio wave emission port has cosecant characteristics. In addition, a curve corresponding to the same dielectric constant satisfies the following relational expression, and in order to attenuate side lobes in the directional characteristics, a curve protrudes from the top of the tip of the antenna body to cover the front top of the radio wave emission port. A cosecant beam horn antenna characterized by being provided with a radio wave absorber. r/r ₀ = exp {∫ _p tanθ _i d} Here, tanθ _i = n・sin(θ−)/ {1−n・cos(θ−)} However, r(): From the wave source point to the radio wave emission port Distance to r ₀ : Distance from the wave source point to the radio wave emission port when = 0 : Aperture angle of the antenna n : 1/√ _{s ε s} : Permittivity θ of the dielectric material inside the antenna body : Angle of depression