JPH05152835A - Mirror surface correction antenna - Google Patents

Abstract

PURPOSE:To obtain the mirror surface correction antenna with less power loss in which a desired shaped beam is realized for both the transmission and reception by providing a transmission primary radiator and a reception primary radiator separately to the antenna so as to use a reflecting mirror in common for the transmission and reception thereby realizing a high separation between the transmission and reception. CONSTITUTION:The antenna consists of a corrected mirror surface 1, a transmission primary radiator 2 and a reception primary radiator 3 being primary radiators. The corrected mirror surface 1 is a corrected parabolic face 4, which is optimized to obtain a desired shaped beam for both the transmission and reception. A desired beam is shaped both for the transmission and reception by correcting the reflecting mirror, and since the transmission primary radiator and the reception primary radiator are arranged separately, the design and the manufacture of the antenna element and the feeding system are simply attained and generation of heat due to a power loss is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna mounted on a satellite or the like.

[0002]

2. Description of the Related Art Satellite-mounted antennas used for satellite broadcasting, satellite communications, etc. are required to have a beam shape that matches the shape of Japan and efficiently radiate radio waves. As a solution to this requirement, an antenna for mounting a broadcasting satellite in Japan will be described below with an example.

BS-2 mounting antenna (Reference 1, Kajikawa et al., "Development of broadcasting satellite 2 mounting antenna (BBM characteristic)", IEICE Technical Report A ・ P82-4
In 8), three horn antennas were used as the primary radiator of the parabolic reflector antenna, and the excitation amplitude and excitation phase were measured by BFN (Beam Forming Network) to the mainland Japan and remote islands such as Okinawa and Ogasawara. To form a shaped beam with a desired gain.
In the BS-3 onboard antenna (Reference 2, Miura et al., "Electrical Characteristics of Broadcast Antenna of Broadcast Satellite 3 (Part 1)", IEICE Technical Research Report A, P87-84), the parabolic reflector antenna Two horn antennas are used as the primary radiator, and a shaped beam is created by adjusting the excitation distribution of the horn antenna as in the BS-2. What these antennas have in common is that the reflector antenna uses a primary radiator composed of a plurality of antenna elements, and its excitation distribution is adjusted to form a beam conforming to the shape of Japan. The problem with this configuration is that the BFN is required to set the excitation distribution, and the power loss that occurs in the power supply components such as the power distributor and phase shifter cannot be ignored. The power loss in the BFN is generated as heat, which causes problems of heat radiation and heat control. Especially when mounted on a satellite, a very high output power is required for transmission, the heat dissipation mechanism becomes complicated, and this greatly affects the satellite design.
The power loss of N should be as small as possible.

In contrast to the above method, the idea of using only one antenna element that does not require BFN and performing beam shaping by only mirror modification is being researched as a future BS mounting antenna. As an example of this, there is a report as shown in (Document 3, Nishida et al., “Shaped Beam Antenna for Broadcasting Satellite”, IEICE Technical Research Report A / P90-23). It has been reported that in this case, the power loss is small, and the beam forming degree is better than those of BS-2 and BS-3.
By the way, in the case of an antenna mounted on a satellite, the problem of how to perform transmission and reception is also important. In the case of BS-2 and BS-3, the reflector and the primary radiator are all used for both transmission and reception. In this case, a horn, a circular polarizer, a power divider and the like must be used from the transmission frequency band to the reception frequency band, which complicates the design and configuration. In this case, a demultiplexer is required to finally separate the transmission / reception system, as shown in FIG. 16, but for satellite broadcasting, since the transmission output is large, the demultiplexer has a large filter with a high degree of separation. Need. In this case, in addition to the problems of shape and weight, power loss due to the duplexer is also a problem.
Furthermore, PIM (passive intermodulation), which is an unnecessary harmonic component when a large amount of power is input,
This may occur due to the seams of the waveguides in the FN and the like, which may cause a problem that the transmission power goes around to the receiver system.
In order to solve the above problems, it is conceivable that the antenna itself including the reflecting mirror is separated for transmission and reception, but in this case, two reflecting mirror antennas are required, and It is not convenient when considering the weight.

[0005]

As described above, when the conventional mirror-finished antenna is used for both transmission and reception, the BFN component has a wide band characteristic that covers all the transmission and reception bands. It is necessary to obtain a complicated structure and design, a demultiplexer having a large filter is required to obtain high isolation, and the occurrence of PIM may be a problem. The present invention solves the above problems and realizes a high degree of separation for transmission and reception without separating the antenna itself for transmission and reception and sharing the reflecting mirror, resulting in low power loss. An object of the present invention is to provide a mirror-modified antenna that realizes a desired shaped beam.

[0006]

In order to achieve the above-mentioned object, a first invention is a transmitting primary radiator for transmitting a radio wave of a first frequency and a radio wave of a second frequency. And a receiving primary radiator for reflecting the radio wave transmitted from the transmitting primary radiator in a desired first direction and reflecting a radio wave from a desired second direction for the reception. A second aspect of the present invention is a mirror-modified antenna, comprising: a reflecting mirror surface having a surface irregularity-corrected surface that is guided to a primary radiator; A third aspect of the present invention is a mirror-modified antenna, which is a correction optimized based on a beam pattern of a radio wave transmitted from a transmitting primary radiator. The radiator consists of multiple antenna elements. A shaped reflector antenna further comprising a beam forming network to power by changing the phase and amplitude to each of the plurality of antenna elements.

[0007]

According to the present invention, by modifying the reflecting mirror, it is possible to form a desired beam shape for both transmission and reception. Since the primary radiators for transmission and reception are separately arranged, the antenna element and the feeding system Design and manufacture can be done by simple procedure,
Generation of heat due to power loss can be suppressed.

Further, by modifying the reflecting mirror only for transmission, it is possible to form a beam with a high degree of shaping that conforms to the shape of Japan in a transmission band important for services such as broadcasting, and radiate radio waves efficiently. It is possible to form a beam pattern for reception that covers a certain area of the broadcasting base station.

Further, by using a plurality of antenna elements as a primary radiator for reception and providing a beam forming network for setting the excitation distribution, a beam with a high degree of shaping is formed even in the reception band, and interference radio waves are generated. It is possible to reduce the side rope in a specific area for the purpose of suppressing it.

[0010]

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

FIG. 1 is a block diagram showing an embodiment of a mirror-modified antenna according to the present invention.

As shown in the figure, this antenna comprises a modified mirror surface 1, a transmitting primary radiator 2 and a receiving primary radiator 3 as primary radiators. Modification mirror surface 1
Is a modification of the parabolic surface 4 and is optimized so as to obtain a desired shaped beam in both transmission and reception. For the method of determining the amount of modification, see, for example, “Reference 4, Shogi et al.,“ Two frequency band beamforming using a single modified mirror surface ”, IEICE Technical Report A.
P89-71, 1989) and (Reference 5, ARCherrett
e et al., `` A Method for Producing a Shaped Contour Ra
diaton PatternUsing a Single Shaped Reflector and
a Single Feed, IEEE Transactions on Antennas and
Propagation, Vol.37, No.6 June 1989) etc. can be used.

The method of determining the modification amount described in Document 4 will be described below.

The parabolic surface 4 is divided into N minute mirror surfaces 5 as shown in FIG. Assuming that each micro mirror surface 5 is a plane mirror, it is assumed that the projection areas of each micro mirror surface 5 on the opening surface are equal. Assuming that the electric field component radiated as a far field from the primary radiator via the I-th minute mirror surface 5 is X _I (S) and the excitation phase is θ _I , the electric power of the radiation field from the entire reflecting mirror 4 in the S direction. The component P (S) is expressed by the following equation. (Here, S represents a vector.)

[Equation 1] Here, * indicates a complex conjugate. The evaluation function Φ is defined as follows.

[0015]

[Equation 2] h (S _k ) is the desired value of the radiated power in the S _k direction. A desired beam shape can be realized by setting the phase vector Ω that minimizes this evaluation function Φ. Now, the phase vector is defined as follows.

[0016]

[Equation 3] In order to find Ω that minimizes Φ, the following iterative calculation may be performed.

[0017]

[Equation 4] Here, μ is the step amount. In this embodiment, since both transmission and reception are optimized, Φ in the above equation is set as follows.

Φ = Φ _RX + Φ _TX (2) Here, Φ _RX and Φ _TX are the evaluation functions corresponding to reception and transmission, respectively, and when each frequency and the primary radiator are used, equation (1) is used. Is a value calculated by. The features of the present invention are:
Here, the primary radiator is provided separately for transmission and reception, and as shown in Document 4, the primary radiator is not used for both transmission and reception.

FIG. 3 is a diagram showing an example of the modification amount of the reflecting mirror which has been modified as described above.

The figure shows the case where the aperture diameter of the parabolic surface 4 is 2.3 m and the F / D (ratio of focal length and aperture diameter) is 0.61. An example of analysis of the shaped beam pattern of each antenna for transmission and reception is shown in FIGS. The frequency is 12 GHz for transmission and 17 GHz for reception. A good pattern that covers the direction in which the desired value of gain is set (marked with X in the figure) is obtained in transmission, and a good pattern that covers Japan and a low sidelobe in the direction of South Korea is obtained in reception. Be done.

By the above procedure, the excitation phase of each micro mirror surface 5 is optimized to obtain a desired shaped beam pattern in both the transmission and reception frequency bands. Here, the amount of modification of the micro mirror surface 5 is set so that the optical path length from the wave source to the micro mirror surface 5 changes by an amount corresponding to each phase amount.
It is obtained by translating in the axial direction. Since the modified mirror surface 5 thus obtained has the discontinuity of the mirror surface inclination, it is necessary to actually review the surface inclination of each micro mirror surface 5 in consideration of the mirror surface smoothness. By this modification and adjustment of the mirror surface inclination, the radiated electric field X _I of each micro mirror surface 5
Changes subtly, so it is necessary to recalculate X _I and repeat the above procedure to converge the modified mirror surface so that the desired shaped beam can be obtained.

In the method described above, by selecting the minute mirror surface 5 to be sufficiently small, it is possible to set a modified reflecting mirror having a smooth reflecting mirror surface. With this modified mirror surface, the radio waves from the primary radiators that are separately arranged for transmission and reception are shaped so as to have a desired beam shape in each frequency band. Here, since the transmitting and receiving primary radiators are separately arranged, there are the following advantages.

Since the primary radiating antenna element and the feeding system component only have to satisfy the required performance within the transmission or reception band, the configuration and design are simplified. For example, considering the case of circular polarization for both transmission and reception,
When using a horn antenna, it is not necessary to use a corrugated horn, which is heavy and difficult to manufacture in order to obtain good characteristics in a wide band, and a step horn with a simple structure is sufficient. It suffices that the circular polarization characteristic is maintained in a narrow band.

Since the primary radiators for transmission and reception are separated, a high degree of separation can be obtained between transmission and reception. The filter provided to prevent radio waves from wrapping around from transmission to reception can be configured much more easily than in the case where transmission and reception are shared.

The BFN and the duplexer are unnecessary, and the power loss can be minimized. In the case of mounting on a satellite, the thermal design and thermal control become simple, which is very convenient. In addition, PIM does not occur in the power supply system and adversely affect the reception system.

The following modifications may be made in the above-described embodiment.

Although the method shown in the document 4 is used in the design of the modified mirror surface, the same effect can be obtained by using the method shown in the document 5 extended to optimize both transmission and reception. .. The difference between Document 4 and Document 5 is that the modified mirror surface is obtained by optimizing the phase distribution on the reflecting mirror surface in Document 4, whereas the modified mirror surface is obtained by optimizing the phase distribution on the aperture surface in Document 5. It is that you are.

In the above-mentioned embodiment, a reflecting mirror having a circular projection surface is selected, but it may be an ellipse or another shape, and the projection surface may be a square or another shape in selecting a micro mirror surface.

Further, in the above-mentioned embodiment, the example in which the correction is performed with the offset parabola as a reference is shown, but this may be used as the center feed.

Further, as the antenna element of the primary radiator, any of a horn antenna, a microstrip antenna and other antenna elements may be used.

Although the case where a single reflecting mirror is used has been described, a system having a plurality of reflecting mirrors such as a Cassegrain antenna and a Grigorian antenna may be used instead. In this case, the mirror surface to be modified may be the main reflecting mirror or the sub-reflecting mirror. Both the main and sub-reflecting mirrors can be modified here. In this case, the amplitude distribution can be optimized in addition to the phase distribution, increasing the degree of freedom in design and obtaining good beam shaping characteristics. Be done.

Further, the above-mentioned embodiment can cope with any polarized wave. That is, circular polarization or linear polarization may be used.

Further, in this embodiment, since the transmitting and receiving primary radiators are separated, the polarized waves may be different between transmitting and receiving, and the configuration is simple. Therefore, the degree of freedom in satellite design is large, which is convenient.

Furthermore, in the above-described embodiment, optimization may be performed with weighting for transmission or reception in the procedure for determining the amount of modification of the mirror surface. For example, in the case of an antenna mounted on a broadcasting satellite, it is desirable to design such that transmission characteristics important for services are preferentially obtained. In this case, weighting may be performed in the expression (2) so that the evaluation amount Φ _TX corresponding to the transmission largely reflects the modification amount.

Next, another embodiment of the present invention will be described.

In another embodiment of the present invention, the structure of the antenna is the same as that shown in FIG. The difference from the previous embodiment is the method of modifying the mirror surface, and the mirror surface is modified so that a desired shaped beam can be obtained only in transmission. That is, in equation (2), Φ = Φ _TX .

In this case, a very good shaped beam pattern is obtained for transmission. Good beamforming cannot be performed for reception, but it is easy to obtain a beam pattern that covers a part of the area. This will be described with a specific example. FIG. 6 shows a transmission frequency f _TX = 12.0 G obtained when the offset parabolic reflector antenna with an aperture diameter of 2.3 m and F / D = 0.61 is modified by this method.
3 shows a shaped beam pattern at Hz. Here, the x mark indicates the point where the desired gain value is set in the design. As is clear from this figure, a good shaped beam is realized, and it can be seen that radio waves can be effectively radiated in a transmission frequency band that is important for services in broadcasting and the like. FIG. 7 shows an antenna pattern at the reception frequency f _TX = 17.0 GHz obtained by arranging the reception primary radiator next to the transmission primary radiator in this case. It can be seen from this figure that an antenna pattern covering a part of the area can be obtained. In this case, it is advisable to arrange the receiving primary radiators adjacent to each other in the direction corresponding to the direction in which the beam is elongated in the shaped beam for transmission. Generally, in broadcasting, a transmitting station that transmits radio waves to a satellite is usually fixed. Therefore, it is sufficient to realize a pattern that can cover the transmitting station in this way. Further, since the transmitting station can be installed with a relatively large output and antenna, the gain may be low. This embodiment is important in that the characteristics of the receiving antenna are kept to the minimum necessary and the degree of freedom in design is used to improve the characteristics of the transmitting antenna directly connected to the service as much as possible. In this embodiment, the primary radiator for transmission may be additionally provided and the land area may be covered with multiple beams in the transmission frequency band.

Further, another embodiment will be described below.

Although the beam of the receiving antenna covers only a part of the area in the above-mentioned embodiment, there are cases where there is a request for beam shaping for reception. This is the case, for example, when configuring a system in which a mobile broadcast station transmits radio waves directly to a satellite.

FIG. 8 is a diagram showing the structure of the antenna in such a case.

The difference from the configuration shown in FIG. 1 is that the receiving primary radiator is composed of a plurality of antenna elements 3a and 3b and has a beam forming network (BFN) which gives these antenna elements a predetermined excitation distribution. Characterize. In the example shown in FIG. 8, the receiving antenna elements 3a and 3b are used.
Is connected to the receiving BFN 6. As shown in FIG. 9, the reception BFN 6 is composed of phase shifters 7a and 7b and a power divider 8. With this configuration, a predetermined excitation amplitude and excitation phase can be set for the reception antenna elements 3a and 3b. As in the other embodiments described above, the reflecting mirror optimizes the modification of the mirror surface in transmission. Therefore, a good shaped beam pattern can be obtained in the transmission frequency band, and effective service can be performed. By using a plurality of antenna elements in the reception frequency band and setting a predetermined excitation distribution, a shaped beam pattern can be realized as a composite pattern thereof. FIG. 10 is a diagram showing a shaped beam pattern in the reception frequency band obtained by this embodiment. As can be seen from this figure, it is possible to realize a shaped beam pattern that covers Japan even in the reception frequency band. As a result,
A good shaped beam can be formed in both transmission and reception,
Convenient for broadcasting and communication services. By further increasing the number of receiving antenna elements, it is possible to realize a pattern with a better degree of shaping. Further, by adjusting the arrangement of the antenna elements and the excitation distribution, it is possible to form a beam with a low side rope in a predetermined direction, which is effective in suppressing an interference wave from a specific direction. In the configuration shown in FIG. 9, power loss occurs in the BFN for reception, but unlike transmission, heat is not generated and there is no problem in satellite design.

In this embodiment, any component or line of the BFN may be used.

For example, when the BFN is formed of a waveguide system, an arbitrary distribution ratio can be set by using a directional coupling type power divider, a septum type power divider or the like as the power divider. As the phase shifter, a method of inserting a metal screw or a method of changing the shape of the waveguide and changing the wavelength in the tube to change the passing phase amount can be used.

FIG. 11 is a diagram showing the configuration of still another embodiment.

As shown in the figure, this mirror-finished antenna is a multi-beam antenna having four beams (A, B, C, D), and primary radiators 9a, 9b corresponding to the respective beams, 9c and 9d are separated and arranged independently. The modified mirror surface 1 is optimized so that each beam has a desired shape. The design of this shape is such that the evaluation function Φ in equation (1) is Φ = Φ _A + Φ _B + Φ _C + Φ _D , and Φ _A , Φ _B , Φ _C , and Φ _D correspond to the primary radiator of each beam. Calculated. By setting the amount of modification that minimizes Φ in the reflecting mirror, a modified reflecting mirror that matches the desired shape of each beam can be obtained.

12, FIG. 13, FIG. 14, and FIG. 15 are diagrams showing an example of analysis of each beam pattern of the mirror-modified antenna of this embodiment. In this example, the beam shown in FIG. 12 is used for Hokkaido / Tohoku, the beam shown in FIG. 13 is used for Kanto / Chubu / Kinki, the beam shown in FIG. 14 is used for Chugoku / Shikoku / Kyushu, and the beam shown in FIG. 15 is used for Okinawa / southwest. It covers each region of the islands, and at the same time shows that it is possible to form a shaped beam pattern that always has a low side lobe in the Korean direction. Since the beam width is smaller, the gain is improved,
It is very effective because it can be transmitted and received by the earth station with low power. Further, as shown in this example, low side lobes can be realized in each beam, which is convenient for preventing unnecessary interference. In this embodiment, each beam can be used for both transmission and reception, and the mirror-modified antenna can be configured so that transmission and reception can be operated simultaneously. The characteristics of the multi-beam antenna can be improved, and the weight and weight can be reduced.

[0047]

According to the present invention, it is possible to realize a good shaped beam pattern corresponding to the service form of satellite broadcasting or satellite communication in transmission and reception. Since the primary radiators for transmission and reception are provided separately, it is possible to easily design and manufacture the primary radiators and the components of the power feeding system, and realize good electrical properties in each band. It will be easier. In addition, a high degree of separation is achieved between the transmissions, and the filter for preventing the radio waves that go around from the transmission to the reception system is small, which facilitates the design and manufacture. further,
Since a shaped beam can be formed by a simple configuration with a single antenna element during transmission, it is possible to reduce power loss in the power feeding system and minimize heat generation. It is very effective because the heat control and heat dissipation mechanism can be simplified in the satellite design.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a state of division of a micro mirror surface that is assumed when determining a modification amount of a mirror surface according to an embodiment of the present invention.

FIG. 3 is a diagram showing an example of a modification amount of a reflecting mirror which has been modified.

FIG. 4 is a diagram showing a transmission beam pattern obtained by the reflecting mirror shown in FIG.

5 is a diagram showing a reception beam pattern obtained by the reflecting mirror shown in FIG.

[Figure 6] Aperture diameter 2.3 when optimized only for transmission
m, is a diagram illustrating a shaped beam pattern in the transmission frequency f _TX = 12.0 GHz obtained when retouching an offset parabolic reflector antenna of F / D = 0.61.

FIG. 7 is a diagram showing an antenna pattern at a reception frequency f _TX = 17.0 GHz obtained by disposing a reception primary radiator next to a transmission primary radiator when only transmission is optimized.

FIG. 8 is a diagram showing a configuration of an embodiment in which two receiving primary radiators are provided.

9 is a block diagram showing a configuration of a reception BFN used in the configuration of FIG.

10 is a diagram showing a beam pattern in a reception frequency band obtained by the embodiment having the configuration shown in FIG.

FIG. 11 is a diagram showing a configuration of a multi-beam antenna having four radiators according to another embodiment of the present invention.

12 is a diagram showing one of beam patterns generated by the multi-beam antenna having the configuration shown in FIG.

FIG. 13 is a diagram showing one of beam patterns generated by the multi-beam antenna having the configuration shown in FIG. 11.

14 is a diagram showing one of beam patterns generated by the multi-beam antenna having the configuration shown in FIG.

15 is a diagram showing one of beam patterns generated by the multi-beam antenna having the configuration shown in FIG.

FIG. 16 is a diagram showing a configuration of a conventional antenna when a primary radiator for both transmission and reception is used.

[Explanation of symbols]

 1 ... Modified mirror surface 2 ... Transmitting primary radiator 3, 3a, 3b ... Receiving primary radiator 4 ... Parabolic surface 5 ... Micro mirror surface 7a, 7b ... Phase shifter 8 ... Power distributor 9a, 9b, 9c, 9d ... Primary radiator

Claims (3)

[Claims] 1. A transmitting primary radiator for transmitting a radio wave of a first frequency, a receiving primary radiator for receiving a radio wave of a second frequency, and the transmitting primary radiator. First desired radio wave transmitted from
And a reflection mirror surface having irregularities on the surface thereof, which reflects the radio wave from the desired second direction and guides it to the receiving primary radiator. 2. The mirror-finished antenna according to claim 1, wherein the irregularities on the surface of the reflecting mirror surface are optimized based on the beam pattern of the radio wave transmitted from the transmitting primary radiator. 3. The primary radiator for reception is composed of a plurality of antenna elements, and further comprises a beam forming network for feeding each of the plurality of antenna elements by changing the phase and the amplitude. The mirror-finished antenna according to any one of 1 to 3.