JPH08195621A - Multibeam antenna - Google Patents

Abstract

PURPOSE: To receive satellite radio waves from plural satellites at the same time without any great decrease in gain even when the satellites have relatively large elongation as to the multibeam antenna which is used to receive radio waves from plural satellites. CONSTITUTION: Two 1/2 reflectors 20 and 20" of a lower half part obtained by halving the reflector of a unifocal type offset parabolic antenna into two upper and lower parts along the bisector of its major axis are joined together on their division lines to form an elliptic reflector 21 which has two focuses F and F" and is horizontally and vertically symmetrical. The reflector 21 is installed having its length direction aligned with the satellite orbital axis 13 of a communication satellite CS and a broadcasting satellite BS; and a CS horn 22 for communication satellite reception is arranged at one focus F and a BS horn 23 for broadcasting satellite reception is arranged at the other focus F".

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-beam antenna used for simultaneously receiving radio waves from a plurality of satellites having a relatively wide satellite separation angle such as a communication satellite (CS) and a broadcasting satellite (BS). .

[0002]

2. Description of the Related Art In a conventional satellite receiving antenna, in order to receive satellite radio waves obtained from a plurality of satellites, a dedicated antenna is installed for each of the plurality of satellites, or one satellite parabolic reflector is used. Then, a plurality of primary radiators having different beam incident positions are attached to form a multi-beam antenna.

FIG. 3 is a diagram showing the structure of a conventional multi-beam antenna. In the conventional multi-beam antenna in FIG. 3, the horn-type primary radiators 11a and 11b are respectively displaced with respect to the focus F of the one-focus type offset parabolic reflecting mirror 10 to deflect the reception beam.
The major axis 12 of the reflecting mirror 10 is installed so as to coincide with the vertical axis of the earth, and the horn primary radiators 11a and 11b are arranged to be displaced from the focal point F of the reflecting mirror 10 in a direction opposite to the inclination of the satellite orbital axis 13. It is what makes me.

As a result, the receiving beams are deflected in two ways by the primary radiators 11a and 11b whose beam incident positions are different from each other so that, for example, radio waves from a communication satellite and a broadcasting satellite can be simultaneously received.

Here, the deviation amount L due to the primary radiators 11a and 11b is expressed by the following equation 1. L = tan α · (→) MF · BDF (Equation 1) where α is the satellite departure angle at the receiving point and BDF is the beam deflection coefficient.

That is, the deviation amount L increases as “α” or “(→) MF” increases.
When the communication satellite (CS) and the broadcast satellite (BS) are received, “α” is large, so the deviation amount L is also large.

In such a multi-beam antenna using the one-focal parabolic reflector 10, when the deviation amount L of the primary radiators 11a and 11b becomes large, the gain is significantly reduced.

[0008]

Therefore, in the conventional multi-beam antenna using the conventional one-focus parabolic reflector 10, when the deviation amount L of the primary radiators 11a and 11b is increased, the gain is remarkably reduced. There is a problem that a multi-beam antenna with a wide satellite separation angle cannot be realized.

The present invention has been made in view of the above-mentioned problems, and even for a plurality of satellites having a relatively wide satellite separation angle, the respective satellite radio waves can be simultaneously transmitted without causing a significant decrease in gain. It is an object to provide a multi-beam antenna capable of receiving.

[0010]

That is, a multi-beam antenna according to the present invention corresponds to a lower half of a reflector of a one-focus offset parabolic antenna divided into upper and lower parts corresponding to the bisector of its long axis. Two half reflectors are used, and the two half reflectors are joined together at their respective dividing lines, and the longitudinal direction of the two half reflectors is the orbit axis of the communication satellite (CS) and broadcasting satellite (BS). , A CS mirror for communication satellite reception arranged with its irradiation axis aligned with one of the focal points of the bifocal reflector, and the other of the bifocal reflector. It is configured by including a BS horn for receiving a broadcasting satellite, which is arranged with its irradiation axis aligned with the focus.

[0011]

That is, the CS horn and the BS horn arranged at each of the focal points of the bifocal reflector formed by joining two 1/2 reflectors to each other, the CS wave and the BS wave having a relatively wide satellite separation angle α are obtained. However, simultaneous reception is possible without impairing the C / N ratio.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a multi-beam antenna of the present invention. In this multi-beam antenna, the reflection mirror of a normal one-focus type offset parabolic antenna is divided into upper and lower parts corresponding to the bisector of the long axis, and the lower half is divided into two parts.
The ½ reflectors 20 and 20 ″ are joined together at their respective dividing lines to form a vertically and horizontally symmetrical elliptical reflector 21. The longitudinal direction of the reflector 21 is a communication satellite (CS). And the satellite orbital axis 13 of the broadcasting satellite (BS).

A reflector 21 of a multi-beam antenna in which the 1/2 reflectors 20 and 20 "are joined has two focal points F and F", and one focal point F has a horn for receiving a communication satellite. A type primary radiator (CS horn) 22 is arranged, and a horn type primary radiator (BS horn) 23 for receiving a broadcasting satellite is arranged at the other focus F ″.

With this configuration, the communication satellite (CS)
The radio wave from the half reflection mirror 20 on the side of the point M from the joining line O
Then, the light beam is reflected and focused on one focus point F where the CS horn 22 is arranged. At this time, however, the 1/2 reflection mirror 20 ″ on the M ″ point side causes an aberration in the radio wave reflected to the one focus point F.

Further, the radio waves from the broadcasting satellite (BS) are reflected and focused on the other focal point F "where the BS horn 23 is arranged at the 1/2 reflecting mirror 20" on the M "side from the joining line O.
At this time, the 1/2 reflection mirror 20 on the side of the point M causes aberration in the radio wave reflected to the other focus F ″.

That is, although the beam is deflected and the gain is reduced due to the aberration of the received radio wave, both the CS horn 22 and the BS horn 23 focus the radio wave reflected by the entire surface of the reflecting mirror 21.

Next, the principle of the multi-beam antenna having the above structure will be described. FIG. 2 is a diagram showing longitudinal section coordinates corresponding to the satellite orbital axis 13 of the multi-beam antenna.

First, with respect to the X-Z axis coordinates, X ² = 4
Draw a mirror coordinate curve of the FZ reflection mirror, define the point with the coordinates on the + side as DXZ, and then draw the curve (X ² = 4FZ)
A point UXZ corresponding to the opening diameter is determined along the line and its curve (DXZ
The middle point of (-UXZ) is defined as CXZ.

On the X axis, the Z'axis is drawn at a position twice as large as the CXZ, and the coordinates of the XZ 'axis are
A mirror surface coordinate curve of X ² = 4F′Z ′ is drawn, and if DXZ ′ is defined at the same position as DXZ on the curve (X ² = 4F′Z ′) on the minus side, the curve (X ² = 4F'Z ')
Intersect at the midpoint CXZ of the curve (DXZ-UXZ).

That is, the curve (DXZ-CXZ) and the curve (DXZ'-CXZ) are symmetrical with respect to CXZ. In this state, when the satellite radio wave arrives from the right direction of the coordinate, the reflected wave by the curve (DXZ-CXZ) is focused on the point F, and the reflected wave by the curve (DXZ'-CXZ) is focused on the point F '. It

Then, the curve of the X-Z'-axis coordinates (DX
When Z′-CXZ) is transformed by θ degrees around the point CXZ, the focal point F ′ moves to F ″ as the point DXZ ′ overlaps the point UXZ.

As a result, the curve (DX
Z′-CXZ) focuses the satellite radio waves coming from the direction rotated by θ degrees in the clockwise direction from the coordinate right direction to the focal point F ″.

Here, the satellite orbit axis cross section of the 1/2 reflecting mirror 20 on the M point side of the multi-beam antenna shown in FIG.
Corresponding to the coordinate curve (DXZ-CXZ) in FIG. 2, the satellite orbit axis cross section of the ½ reflecting mirror 20 ″ on the M ″ side is the solid line portion of the coordinate curve (CXZ−UXZ), that is, θ.
This corresponds to the curve (DXZ'-CXZ) after the degree coordinate conversion.

Therefore, C having a relatively wide separation angle of θ degrees
The S wave and the BS wave are reflected and focused on the focal points F and F ″, respectively. On the other hand, when the satellite separation angle α at the receiving point of the CS wave and the BS wave is set, the coordinate conversion amount θ of the reflecting mirror is Required by.

Θ = (beam deflection angle due to α-aberration) / BDF (2) Then, the θ can be varied by setting DXZ and reflecting mirror focal length F, as shown in the following Expression 3, and DXZ
Is large, θ is large, and when F is large, θ is small but the aberration is small.

Θ = 180−tan ⁻¹ {CXZ (X) −DXZ (X) / CXZ (Z) −DXZ (Z)} −tan ⁻¹ {UXZ (X) −CXZ (X) / UXZ (Z) −CXZ (Z)} Equation 3 When the value of θ has to be increased, if DXZ is increased, the axial ratio (major axis / minor axis) of the reflecting mirror becomes very large. In order to avoid this, the shortage of θ may be made to correspond to the satellite departure angle α by displacing the BS horn 23 from the focal point F ″ perpendicularly to the horn irradiation axis to deflect the reception beam.

In this case, even if the BS reception antenna gain is slightly lower than the CS reception antenna gain due to the deviation of the BS horn 23, the effective secondary power of the BS wave (EI.
R. Since P) is larger than that of the CS wave, there is no problem.

Therefore, according to the multi-beam antenna having the above-mentioned structure, the reflecting mirror of the one-focal-type offset parabolic antenna is divided into the upper and lower parts corresponding to the bisector of the major axis of the reflecting mirror. ½ reflecting mirror 20, 20 ″,
Each of the dividing lines is connected to each other and has two focal points F and F ″.
And a symmetrical elliptical reflecting mirror 21 having
The reflecting mirror 21 is installed so that the longitudinal direction thereof corresponds to the satellite orbit axes 13 of the communication satellite (CS) and the broadcasting satellite (BS),
Since the CS horn 22 for receiving the communication satellite is arranged at one focus F and the BS horn 23 for receiving the broadcasting satellite is arranged at the other focus F ″, the satellite departure angle α is relatively small. Wide CS and BS waves without impairing the C / N ratio
You will be able to receive at the same time.

[0029]

As described above, according to the present invention, the reflecting mirror of the one-focal-type offset parabolic antenna is divided into upper and lower parts corresponding to the bisector of its long axis, which corresponds to the lower half.
By using a CS horn and a BS horn arranged at each of the focal points of a bifocal reflecting mirror formed by joining two reflecting mirrors,
Even for a plurality of satellites having a relatively wide satellite separation angle, it is possible to simultaneously receive the respective satellite radio waves without significantly lowering the gain.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a multi-beam antenna according to an embodiment of the present invention.

FIG. 2 is a view showing longitudinal section coordinates corresponding to a satellite orbit axis of the multi-beam antenna.

FIG. 3 is a diagram showing a configuration of a conventional multi-beam antenna.

[Explanation of symbols]

13 ... Satellite orbit axis, 20, 20 "... 1/2 reflector, 21
... 2-focal reflecting mirror, 22 ... CS horn, 23 ... BS horn, O ... Reflecting mirror joining line, F ... CS reflecting focus, F "...
BS reflection focusing focus.

Claims (3)

[Claims] 1. A single-focal type offset parabolic antenna reflecting mirror is divided into upper and lower parts corresponding to the bisector of its long axis, and two half reflecting mirrors corresponding to the lower half are used. ½ reflecting mirror is joined with each dividing line,
Communication satellite (CS) and broadcasting satellite (BS) in the longitudinal direction
A mirror having two focal points installed corresponding to the orbital axis of the satellite, a CS horn for receiving a communication satellite arranged with its irradiation axis aligned with one focal point of the bifocal mirror, and the bifocal mirror A multi-beam antenna comprising: a BS horn for receiving a broadcasting satellite, which is arranged so that its irradiation axis is aligned with the other focal point. 2. A mirror coordinate curve (X ² = 4F) in the XZ axis coordinate plane is defined as one end point and the other end point in the longitudinal direction corresponding to the satellite orbital axis of the bifocal reflector and its midpoint, respectively.
Z) on DX), UXZ and CXZ, the angle θ formed between the reception beams with respect to the communication satellite (CS) and the broadcasting satellite (BS) is θ = 180-tan ^-1 {CXZ (X)- DXZ (X) / CXZ (Z) -DXZ
The multi-beam antenna according to claim 1, wherein the multi-beam antenna is adjusted based on (Z)}-tan ^-1 {UXZ (X) -CXZ (X) / UXZ (Z) -CXZ (Z)}. 3. The multi-beam antenna according to claim 2, wherein the BS horn is disposed so as to be deviated from the other focus in a direction perpendicular to the horn irradiation axis.