JP3322897B2 - Mirror modified antenna - Google Patents

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 There is a demand for antennas mounted on satellites used for satellite broadcasting, satellite communication, etc., to form a beam shape in accordance with the shape of Japan and efficiently radiate radio waves. As a solution to this request, an antenna for a broadcast satellite in Japan will be described below with an example.

[0003] Antenna for mounting on BS-2 (Reference 1, Kajikawa et al., "Development of antenna for mounting on broadcasting satellite 2 (BBM characteristics)", IEICE technical report A / P82-4
In 8), three horn antennas are used as the primary radiator of the parabolic reflector antenna, and the excitation amplitude and the excitation phase are performed by BFN (beam forming network), so that the mainland Japan and remote islands such as Okinawa and Ogasawara can be used. To form a shaped beam overlaid with a desired gain.
The antenna for mounting on BS-3 (Ref. 2, Miura et al., “Electrical characteristics of broadcasting antenna of broadcasting satellite No. 3 (Part 1)”, IEICE Technical Report A, P87-84) describes a parabolic reflector antenna. Two horn antennas are used as primary radiators, and a shaped beam is created by adjusting the excitation distribution of the horn antenna as in BS-2. What is common to these antennas is that a primary radiator composed of a plurality of antenna elements is used in a reflector antenna, and its excitation distribution is adjusted to form a beam conforming to the shape of Japan. The problem with this configuration is that a 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 the phase shifter cannot be ignored. Since the power loss in the BFN is generated as heat, problems of heat dissipation and heat control occur. In particular, in the case of a satellite-mounted device, a very high output is required for transmission, the heat radiation mechanism becomes complicated, and this has a significant effect on the satellite design.
It is necessary to minimize the power loss of N.

[0004] In contrast to the above-described method, a concept of using only one antenna element, which does not require a BFN, and performing beam shaping only by mirror surface modification has been studied as a future antenna for BS mounting. As an example of this, there is a report as shown in (Reference 3, Nishida et al., "Shaped beam antenna for on-board broadcasting satellite", IEICE Technical Report A / P90-23). In this case, it is reported that the power loss is small and that the beam shaping degree can obtain better characteristics than those of BS-2 and BS-3.
By the way, in the case of a satellite-mounted antenna, the problem of how to perform transmission and reception is also important. In the case of BS-2 and BS-3, the configuration is such that all of the reflector and the primary radiator are 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 as shown in FIG. 16 to finally separate the transmission / reception system. However, for satellite broadcasting, a large filter having a very high degree of separation is used for the demultiplexer because the transmission output is large. Need. In this case, in addition to the 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 power is applied, is B
This may be caused by a seam of a waveguide in the FN or the like, which may cause a problem that the transmission power goes around the receiver system.
In order to solve the above-mentioned problems, it is conceivable to adopt a configuration in which the antenna itself including the reflector is separated for transmission and reception, but in this case, two reflector antennas are required, and the satellite It is inconvenient when weight is taken into consideration.

[0005]

As described above, when the conventional mirror-modified antenna is used for both transmission and reception, a wide band characteristic that covers all the transmission and reception bands of the BFN components is used. In some cases, the configuration and design are complicated, and a duplexer having a large filter is required to obtain a high degree of separation, and the occurrence of PIM may be a problem. In the present invention, the above problems are solved, the antenna itself is not separated for transmission and reception, and the reflector is shared, a high degree of separation is realized for transmission and reception, and power loss is small. It is an object of the present invention to provide a mirror-modified antenna that realizes a desired shaped beam.

[0006]

In order to achieve the above object, the invention according to claim 1 transmits a radio wave of a first frequency.
Primary radiator for transmission and radio waves of the second frequency
A plurality of receiving primary radiators for receiving the
Pattern of transmitted radio wave transmitted from primary radiator
The surface irregularities have been corrected so as to optimize
While reflecting the radio wave in a desired first direction,
Primary radiation for reception by reflecting radio waves from a second direction
Mirror modified antenna having a reflecting mirror surface leading to a vessel.
The invention described in claim 2 is the same as the invention described in claim 1.
Thus, the primary radiator for reception includes a plurality of antenna elements.
And each of these multiple antenna elements
Beamforming network feeding with variable phase and amplitude
Mirror-modified antenna characterized by further comprising
The invention according to claim 3 provides a multi-beam antenna.
A plurality of primary radiators to be configured and the plurality of primary radiators
To reflect the transmitted radio waves,
Surface radio wave reflected and guided to each of the primary radiators.
A mirror-modified antenna having a reflecting mirror whose convexity has been corrected
It is.

[0007]

According to the present invention, by modifying the reflector, it is possible to form a desired beam shape for both transmission and reception, and since the primary radiators for transmission and reception are arranged separately, the antenna element and the feed system are separated. Design and production can be performed with simple procedures,
Generation of heat due to power loss can be suppressed.

In addition, by modifying the reflector only for transmission, a beam having a high degree of shaping conforming to the shape of Japan can be formed in a transmission band important for services such as broadcasting, and radio waves can be radiated efficiently. For the reception, a beam pattern that covers a certain area of the broadcast base station can be formed.

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

[0010]

An embodiment 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 FIG. 1, the antenna comprises a modified mirror surface 1, a primary radiator for transmission 2 and a primary radiator 3 for reception as primary radiators. Modified mirror surface 1
Is a modified parabolic surface 4, which is optimized 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 beam forming with a single modified mirror surface”, IEICE technical report A.
P89-71, 1989) and (Reference 5, ARCherrett).
e and others, `` 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) can be used.

A method for determining the amount of modification described in Reference 4 will be described below.

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

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

[0015]

(Equation 2) h (S _k ) is a desired value of the radiated power in the S _k direction. By setting the phase vector Ω so as to minimize the evaluation function Φ, a desired beam shape can be realized. Now, the phase vector is defined as follows.

[0016]

(Equation 3) In order to find Ω that minimizes Φ, the following repeated calculation may be performed.

[0017]

(Equation 4) Here, μ is a step amount. In this embodiment, since optimization is performed for both transmission and reception, Φ in the above equation is set as follows.

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

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

FIG. 1 shows the case where the aperture diameter of the parabolic surface 4 is 2.3 m and the F / D (the ratio between the focal length and the aperture diameter) is 0.61. FIGS. 4 and 5 show examples of analysis of the shaped beam patterns of the antennas for transmission, reception, and respective antennas. The frequency is 12 GHz for transmission and 17 GHz for reception. In transmission, a good pattern covering the direction in which the desired value of gain is set (marked in the figure) is obtained, and in reception, a good pattern covering Japan and low sidelobes in the direction of Korea is obtained. Can be

By optimizing the excitation phase of each micro-mirror surface 5 by the above procedure, a desired shaped beam pattern can be obtained in both the transmission and reception frequency bands. Here, the amount of modification of the micromirror surface 5 is set so that the optical path length from the wave source to the micromirror surface 5 changes by an amount corresponding to each phase amount.
It is obtained by moving in parallel in the axial direction. Since the modified mirror surface 5 obtained in this manner has a discontinuous mirror surface inclination, it is actually necessary to review the surface inclination of each minute mirror surface 5 in consideration of the smoothness of the mirror surface. The radiated electric field X _I of each micromirror surface 5 is obtained by this modification and the adjustment of the inclination of the mirror surface.
Since will change slightly, it is necessary to converge as further above procedure a desired shaped beam gets mirror repeat recalculates X _I again obtained.

In the method described above, a modified reflector having a smooth and continuous reflecting mirror surface can be set by selecting the micro mirror surface 5 to be sufficiently small. With this modified mirror surface, the radio waves from the primary radiators 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 arranged separately, there are the following advantages.

Since the primary radiation antenna element and the feed system component need only satisfy the required performance only in the transmission or reception band, the configuration and design are simplified. For example, considering the case where both transmission and reception are circularly polarized,
When a horn antenna is used, it is not necessary to use a corrugated horn that is heavy and difficult to manufacture in order to obtain good characteristics over a wide band, and a simple configuration of a step horn is sufficient. It is only necessary that circular polarization characteristics be maintained in a narrow band.

Since the primary radiator for transmission and reception is separated, a high degree of separation can be obtained between transmission and reception. The filter provided to prevent the transmission of the radio wave from transmission to reception can be configured much more easily than when the transmission and reception are shared.

The BFN and the duplexer become unnecessary, and the power loss can be minimized. In the case of onboard satellites, thermal design and thermal control are simplified, which is very convenient. Also, PIM does not occur in the power supply system and adversely affect the reception system.

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

Although the method shown in Reference 4 is used in designing the modified mirror surface, the same effect can be obtained by using a method extended from the method shown in Reference 5 so as to optimize both transmission and reception. . The difference between Literature 4 and Literature 5 is that, in Literature 4, the modified mirror surface was obtained by optimizing the phase distribution on the reflecting mirror surface. In Literature 5, the modified mirror surface was obtained by optimizing the phase distribution on the aperture surface. It is that you are.

In the above-described embodiment, a reflecting mirror having a circular projection surface is selected. However, the reflecting mirror may be formed into an elliptical shape or another shape, and the projection surface may be formed into a square shape or another shape in selecting a minute mirror surface.

Further, in the above-described embodiment, an example in which the correction is performed based on the offset parabola has been described, but this may be a 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 or a Grigorian antenna may be used instead. In this case, the mirror surface to be modified may be a main reflecting mirror or a sub-reflecting mirror. In this case, both the main reflecting mirror and the sub-reflecting mirror can be modified. In this case, the amplitude distribution can be optimized in addition to the phase distribution, so that the degree of freedom of design increases, and a good characteristic of the beam shaping degree can be obtained. Can be

Further, the above-described embodiment can cope with an arbitrary polarization. In other words, circular polarization or linear polarization may be used.

In this embodiment, since the primary radiator for transmission and reception is separated, the polarization may be different between transmission and reception, and the configuration is simple. For this reason, the degree of freedom in satellite design is large, which is convenient.

Further, in the above-described embodiment, weighting optimization may be performed on transmission or reception in the procedure for determining the amount of mirror surface modification. For example, in the case of an antenna mounted on a broadcasting satellite, it is desired that the antenna be designed so that transmission characteristics important for service can be preferentially obtained. In this case, the amount of modification may be weighted in equation (2) so that the evaluation function Φ _TX corresponding to the transmission greatly reflects.

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

In another embodiment of the present invention, the configuration 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, which 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 can be obtained for transmission. Although good beamforming cannot be performed for reception, 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 an offset parabolic reflector antenna having an aperture diameter of 2.3 m and F / D = 0.61 is modified by this method.
3 shows a shaped beam pattern in Hz. Here, the crosses indicate the points at which the desired gain value was 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 important for service in broadcasting and the like. FIG. 7 shows an antenna pattern at a receiving frequency f _TX = 17.0 GHz obtained by disposing the primary receiving radiator next to the primary transmitting radiator in this case. From this figure, it can be seen that an antenna pattern covering a part of the area can be obtained. In this case, it is preferable to arrange the primary receiving radiator adjacent to a direction corresponding to the direction in which the beam is elongated in the transmission shaped beam. Generally, in broadcasting, a transmitting station that transmits radio waves to a satellite is generally fixed. Therefore, it is sufficient if a pattern that can cover the transmitting station can be realized. In addition, since the transmitting station can be provided 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 a minimum necessary level and the degree of freedom of design is used to improve the characteristics of the transmitting antenna directly connected to the service as much as possible. In this embodiment, some additional primary radiators for transmission are additionally arranged, and in the transmission frequency band, the use of multi-beams to cover the national land can be easily performed.

Further, another embodiment will be described below.

In the above-mentioned embodiment, the beam of the receiving antenna covers only a part of the area. This applies, for example, to the case where a system in which radio waves are transmitted directly from a mobile broadcast station to a satellite is configured.

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

The difference from the configuration shown in FIG. 1 is that the primary radiator for reception is constituted by a plurality of antenna elements 3a and 3b and has a beam forming network (BFN) for giving a predetermined excitation distribution to these antenna elements. Features. In the example shown in FIG. 8, the receiving antenna elements 3a, 3b
Is connected to the receiving BFN 6. As shown in FIG. 9, the receiving BFN 6 is composed of phase shifters 7a and 7b and a power divider 8, and this configuration can set a predetermined excitation amplitude and excitation phase for the receiving antenna elements 3a and 3b. The reflecting mirror optimizes the modification of the mirror surface in transmission as in the other embodiments described above. Therefore, a good shaped beam pattern can be obtained in the transmission frequency band, and effective service can be provided. By using a plurality of antenna elements in the receiving 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 of a receiving 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 receiving frequency band. As a result,
A good shaped beam can be formed for both transmission and reception,
It is convenient for broadcasting and communication services. By further increasing the number of receiving antenna elements, it is possible to realize a pattern with a higher degree of shaping. Further, by adjusting the arrangement of the antenna elements and the excitation distribution, it is possible to form a beam having a low side lobe 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 components or lines of the BFN may be used.

For example, when a BFN is configured by 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 waveguide wavelength by changing the shape of the waveguide and changing 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-modified antenna is a multi-beam antenna having four beams (A, B, C, D), and primary radiators 9a, 9b, 9c and 9d are separately arranged independently. The modified mirror surface 1 is optimized so that each beam has a desired shape. The shape of the design (1) Distant evaluation function _{Φ Φ = Φ A + Φ B} + Φ C + Φ D in _{formula, Φ A, Φ B, Φ} C, Φ D corresponds to the primary radiators of each of the beams Is calculated. By setting the amount of modification that minimizes Φ to the reflector, a modified reflector that matches the desired shape of each beam can be obtained.

FIGS. 12, 13, 14, and 15 show examples of analysis of each beam pattern of the mirror-modified antenna of this embodiment. In this example, the beam shown in FIG. 12 shows Hokkaido and Tohoku, the beam shown in FIG. 13 shows Kanto, Chubu, and Kinki, the beam shown in FIG. 14 shows China, Shikoku, and Kyushu, and the beam shown in FIG. It covers each region of the archipelago, and at the same time shows that it is possible to create a shaped beam pattern that always has low sidelobes in the direction of Korea. Gain is improved because the beam width is small,
It is very effective because it can be transmitted and received by earth stations with low power. Further, as shown in this example, reduction of side lobes can be realized for 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 to operate both transmission and reception simultaneously. The characteristics of the multi-beam antenna can be improved, and the weight and the size can be reduced.

[0047]

According to the present invention, it is possible to realize a good shaped beam pattern corresponding to the form of satellite broadcasting or satellite communication service in transmission and reception. Here, by providing the transmitting and receiving primary radiators separately, it is possible to easily design and manufacture the primary radiator and the feed system component, and to realize good electrical properties in each band. It becomes easier. In addition, a high degree of separation between transmissions is achieved, and a filter for preventing radio waves from flowing from the transmission to the receiving system is small, which facilitates design and manufacture. further,
Since a shaped beam can be formed with a simple configuration using a single antenna element in transmission, power loss in the feed system can be reduced and heat generation can be minimized. The heat control and heat dissipation mechanism can be simplified in the satellite design, which is very effective.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a mirror-modified antenna of one embodiment of the present invention.

FIG. 2 is a diagram illustrating a state of division of a small mirror surface assumed when determining a modification amount of a mirror surface in one embodiment of the present invention.

FIG. 3 is a diagram illustrating an example of a modified amount of a reflector that has been modified.

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

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

FIG. 6: Aperture diameter 2.3 when only transmission is optimized
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 receiving frequency f _TX = 17.0 GHz obtained by arranging a primary receiving radiator next to a primary transmitting radiator when only the transmission is optimized.

FIG. 8 is a diagram showing a configuration of an embodiment when two primary radiators for reception are provided.

FIG. 9 is a block diagram showing a configuration of a reception BFN used in the configuration of FIG. 8;

FIG. 10 is a diagram showing a beam pattern in a reception frequency band obtained by the embodiment having the configuration shown in FIG. 8;

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.

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

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

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 illustrating a configuration of a conventional antenna in the case of using a primary radiator that is shared for transmission and reception.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Modified mirror surface 2 ... Primary radiator for transmission 3, 3a, 3b ... Primary radiator for reception 4: Parabolic surface 5 ... Micromirror surface 7a, 7b ... Phase shifter 8 ... Power distributor 9a, 9b, 9c, 9d: Primary radiator

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-170305 (JP, A) JP-A-63-82003 (JP, A) JP-A-3-192803 (JP, A) JP-A-1- 220903 (JP, A) JP-A-58-92106 (JP, A) JP-A-3-253107 (JP, A) JP-A-3-235506 (JP, A) JP-A-56-119504 (JP, A) JP-A-56-47106 (JP, A) JP-A-60-196003 (JP, A) JP-A-2-30621 (JP, U) JP-A-1-126714 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01Q 19/17 H01Q 15/14 H01Q 3/00 H01Q 25/00

Claims (3)

(57) [Claims] 1. A transmission for a primary radiator for transmitting a radio wave of a first frequency, and a plurality of reception primary radiator for receiving a wave of a second frequency, the transmission primary Transmitted radio beam transmitted from radiator
Surface irregularities have been modified to optimize the pattern
Is the radio waves transmitted while reflecting a desired first direction, shaped reflector antenna comprising a conductive Ku reflection mirror to a primary radiator for the reception by reflecting radio waves from a desired second direction . 2. A primary radiator for the reception is constituted by a plurality of antenna elements, characterized by further comprising a beam forming network to power by changing the phase and amplitude to each of the plurality of antenna elements to claim 1
Serial mounting shaped reflector antenna. 3. A plurality of primary radiators constituting a multi-beam antenna; and a radio wave transmitted from each of the plurality of primary radiators is reflected, and each of the primary radiators is reflected by reflecting an incoming radio wave. A mirror-correcting antenna comprising: a reflecting mirror whose surface irregularities have been corrected;