JPH02226804A - Parabolic antenna device - Google Patents

Abstract

PURPOSE:To improve the gain by employing a two-wire type backfire helical antenna which can be given axial symmetry as a primary radiator. CONSTITUTION:The two-wire type backfire helical antenna 2A which has the axial symmetry is arranged at the focus of a parabolic reflecting mirror 1. A coaxial line 3 is connected to the feeding point of this backflre helical antenna 2A on the reflecting mirror side through a balun circuit 10 and the coaxial line 3 is led out to the back side of the reflecting mirror. Then the two-wire type backfire helical antenna 2A is employed as the primary radiator, so the gain can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a circularly polarized parabolic antenna device 1 used for microwave communication such as reception of satellite broadcasting.

(Summary of the Invention) The present invention provides a micro TV for receiving satellite broadcasting, etc. In the circularly polarized parabolic antenna device used in this communication,
A linear backfire helical antenna is used as the -order radiator to improve gain.

(Prior Art) Conventionally, as this type of SHF circularly polarized parabolic antenna device, there has been one that uses an end 7T ear helical antenna as a -order radiator, as shown in Japanese Patent Laid-Open No. 11α56-93402. Ta. This parabolic antenna device has problems such as a large loss in the primary radiator and a problem in the support strength of the -order radiator.As a solution to these problems, the present applicant has proposed the method disclosed in Japanese Patent Application Laid-Open No. 62-32707. So, the next radiator is a single wire back 7 year helical 7
We have already proposed something that uses an antenna.

FIG. 7 shows a conventional example of a parabolic antenna device using a single-wire backfire helical antenna as a primary radiator. In this figure, a single-wire backfire helical antenna 2 is placed at the focal point of a parabolic reflector 1, and the reflection w of this pack 7 fire helical antenna 2 is
A coaxial line (for example, a semi-linod cable, a linrad cable, etc.) 3 is connected to the feeding point of gA. The coaxial line 3
is led out to the back side of the reflecting mirror along the central axis of the reflecting fil. Note that the central axis of the pack 7 fire helical antenna 2 and the central axis of the reflecting mirror 1 coincide.

Here, the single-wire type backfiring helical antenna 2 is connected to a matching disk (ground plate) 7 and a center conductor 3B, which are connected to the outer conductor 3A of the coaxial line 3, as shown in FIGS. 8 and 9. It consists of one spiral conductor 8 with a main rope on the power feeding point side. Here, Du is the cylindrical diameter when the entire spiral conductor is considered to be cylindrical.
Dg is the diameter of the matching disk, a is the pitch angle, and θ is the taper angle.

(Problem to be Solved by the Invention) Now, in the conventional parabolic antenna device shown in FIG. 7, the antenna aperture angle is represented by 2W, and the aperture angle 2XV is 18
As the temperature approaches 0 degrees, the amount of protrusion of the primary radiator relative to the aperture of the parabolic reflector 1 decreases, and the front surface of the reflector becomes a groove that can be easily covered with a radome for protection against wind, rain, and snow. However, if the antenna aperture angle is made thicker, the pitch angle a of the single-wire back 7-fire helical antenna 2 used as the -order radiator must be made thicker. As is clear from the perspective view, the helix of the helical conductor 8 becomes sparse and becomes asymmetrical with respect to the central axis of the packfire helical antenna 2.

The tISio diagram shows the radiation pattern of the single-wire B-7 fire helical antenna itself, with a beam width of 10 dB (B
W, ,) is shown as 197 degrees, but due to the asymmetry mentioned above, the characteristics (indicated by arrows P and Q) toward the aperture periphery of the parabolic reflector 1 are asymmetrical. ing.

Here, Du=0.3183A, Dg=0.1736
Person, a = 24 degrees, θ, = 12.5 degrees, taper part number of turns N
t=1, number of turns of uniform part (same diameter part) Nu=6,
Radius of the conductor itself ρ = 0.012A, input (electromagnetic wave wave)
−25 msa. In addition, Fig. 11 uses a single-wire backfire helical antenna 2 having a radiation pattern of Pt510 diagram as the primary radiator, and has an aperture diameter of 75 cm.
, ■ The radiation pattern of the parabolic antenna device with the mouth angle 2v = 180 degrees is shown by the solid line, and the cross-polarization characteristics are shown by the dotted line, and the horizontal axis θ is the angle from the central axis of the parabolic reflection fit. be. However, the measurement frequency was 12 GHz.

The asymmetry of the radiation characteristics shown in FIG. 10 described above deteriorates the efficiency when receiving circularly polarized electromagnetic waves, leading to a decrease in gain (
There was a dislike. Furthermore, the radiation pattern and cross-polarization characteristics shown in FIG. 11 are also necessarily asymmetrical.

The present invention improves the symmetry of the radiation pattern of the -order radiator by employing a linear back 7T ear helical antenna with axial symmetry as the -order radiator, thereby improving the gain. The purpose of the present invention is to provide a parabolic antenna device that achieves the following objectives.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a pair of spiral conductors with a tapered or flared shape in a cylindrical or circular shape on the side where the focal point of the reflecting mirror exists. A wire-type bar/reverse 7-year helical antenna is arranged so that the feeding point is on the reflecting mirror side.

(Function) The wire type backfire helical antenna used in the present invention has directivity toward the feeding point I (toward the rear end), that is, the main rope faces toward the feeding point. Moreover, even if the helical pitch of the helical conductor is sparse (the pitch angle a is large) in the case of a wide aperture angle (when the antenna depth dimension is small), the wire type back 7 fire helical antenna is axially symmetrical. The radiation pattern of the -order radiator can be obtained as an axially symmetrical radiation pattern, and the gain can be improved.

(Example) Hereinafter, an example of a parabolic antenna device according to the present invention will be described with reference to the drawings.

In the tpJ1 diagram, a back-firing helical antenna 2A of the single-wire type is arranged at the focal point of the parabolic reflector 1, and a coaxial line (for example, a semi-rigid (such as a power cable or a linod cable) 3 are connected via a balun circuit 10. The coaxial line 3 is led out along the central axis of the reflecting mirror 1 to the rear side of the reflecting mirror. Note that the balun circuit 10 is fixed to the tip of the coaxial line 3, and a configuration such as a slit balun or a super top balun can be adopted. Further, the central axis of the linear backfire helical antenna 2A and the central axis of the reflecting mirror 1 coincide.

Here, the two wire-type back 7-fire helical antennas are an axially symmetric pair of balun circuits 10 integrated at the tip of the coaxial #l path 3, as shown in FIGS. 2 and 3. Consisting of two (-N) spiral conductors 8A and 8B connected to the feeding end of the They are axially symmetrical and are shifted 180 degrees from each other. Here, Du is the diameter of the circular part when the entire spiral conductor is considered to be cylindrical, a is the pitch angle, and θ is the taper angle. 0.5 people ≦ x Du ≦ 1.2 people 3 degrees ≦ α It is desirable to set the angle to satisfy the following conditions: ≦40 degrees 0 degrees≦θt≦45 degrees (where π: pi). Outside these ranges, the front-to-back ratio deteriorates and the gain decreases.

Figure 4 shows the radiation pattern of the linear backfire helical antenna itself, with a -10 dB beam [(BW+o)
Since the pair of spiral conductors 8A and 8B are arranged axially symmetrically,
Characteristics (arrow P,
(denoted by Q) are symmetrical.

Here, Du; 0.3183λ, 0228 degrees, θ, =
12.5 degrees, taper part number of turns N.

= 1, number of turns Nu of uniform part (same diameter part) = 6, radius of conductor plain wood ρ = 0.012^, λ (wavelength of electromagnetic wave) =
It was set to 25 mm. Figure 5 also shows a two-rope packfire helical antenna 2 with the radiation pattern shown in Figure 4.
Use A as the primary radiator, aperture diameter 75cm, aperture angle 2
The radiation pattern of the parabolic antenna device of the example where 1 = 180 degrees is shown as a solid line, and the cross polarization characteristic is shown as a dotted line, and the horizontal axis θ is the angle from the central axis of the parabolic reflection 11!1. The angle is 9. However, the measurement frequency was 12 GHz.

The radiation patterns shown in Figures 4 and 5 are both axially symmetrical, and do not deteriorate the efficiency when receiving circularly polarized electromagnetic waves (as compared to the conventional single-wire backfire system).
Gain can be improved more than that using a helical antenna. Further, from FIG. rPJ5, it can be seen that the cross polarization characteristics and side rope characteristics are superior to the conventional characteristics shown in FIG. 11.

Figure 6 shows the relationship between the antenna frontage angle 2mm and the gain for a parabolic antenna device in the case of an example using a wire-type back 7-year helical antenna 2A, and for a back 7-year helical antenna of IN type 19. This is a comparison with a conventional example using 2. In this figure, curve a shows the example, and curve #1b shows the conventional example when the -10 dB beam width (BW, . . . ) is bowed at 85 degrees. Further, curve C is the example, and curve lid is the conventional example, when the beam width is -10 dB (I3W1.) and the power bow is 97 degrees. From these curves, it can be seen that the gain is higher in the embodiment using the 2#i backfire or helical antenna as the primary radiator.

In addition, the wire system bar 7 illustrated in riS2 diagram and Figure 3
The 7-year helical antenna does not have a flare, but if necessary, the helical diameter of the spiral conductor at one elbow can be gradually thickened toward the tip (towards the opposite angle of the feed point) to form a flare. Good too.

(Effects of the Invention) As explained above, according to the parabolic antenna device of the present invention, by employing a 2@-type backfire helical antenna that can have axial symmetry as a -order radiator, It is possible to improve the symmetry of the radiation pattern of the primary radiator when the aperture angle is large, and thus to improve the gain. Furthermore, it is also possible to improve the characteristics by modifying the mirror surface of the reflecting mirror.

[Brief explanation of the drawing]

The PtSi diagram is a side sectional view showing an embodiment of the parabolic antenna device according to the present invention, FIG. 2 is a perspective view showing a wire type back 7T ear helical antenna used as a primary radiator in the embodiment, and FIG. is the same side view, FIG. 4 is a radiation pattern diagram of the primary radiator in the case of the embodiment, FIG. 5 is a radiation pattern diagram of the parabolic antenna device of the embodiment, and FIG. 6 is a diagram of the radiation pattern of the embodiment of the present invention and the conventional example. 7 is a side sectional view showing a conventional example of a parabolic antenna device, and FIG. 8 is a graph showing the relationship between the antenna aperture angle and gain in the conventional example. FIG. 9 is a perspective view showing the antenna, FIG. 9 is a side view thereof, Pt510 is a radiation pattern diagram of a primary radiator in a conventional example, and FIG. 11 is a radiation pattern diagram of a conventional parabolic antenna device. 1... Parabolic reflector, 2... Single wire back 7 eye. Ya helical antenna, 2A...2#X type backfire helical antenna, 3...Coaxial line, 8
．． 8A, 8.8... spiral conductor, 10... balun circuit.

Claims (2)

[Claims] (1) A two-wire backfire helical antenna consisting of a pair of helical conductors wound in a cylindrical shape or with a tapered or flared shape at the end of the cylindrical shape is installed as a feeding point on the side where the focal point of the reflecting mirror exists. 1. A parabolic antenna device characterized in that the parabolic antenna is arranged so that the antenna is on the reflecting mirror side. (2) Du
, where α is the pitch angle, θ_t is the angle of the taper, and λ is the wavelength of the electromagnetic wave, 0.5λ≦πDu≦1.2λ 3 degrees≦α≦40 degrees 0 degrees≦θ_t≦45 degrees (However, π: The parabolic antenna device according to claim 1, wherein the parabolic antenna device is: