JP4954099B2 - Multi-beam antenna device for satellite installation - Google Patents

Description

  The present invention relates to a satellite-mounted multi-beam antenna device mounted on a space device such as an artificial satellite or a spacecraft.

  Conventionally, multi-beam communication using satellites has been carried out overseas, and mobile satellite communication services (MSS: Mobile Satellite Service) using the L band (conventional wavelength band castle) are provided by Thuraya, AceS (satellite). Mobile phones) (see, for example, Non-Patent Document 1 and Non-Patent Document 2).

In order to provide satellite broadband services at a low cost, it is necessary to efficiently allocate satellite system resources such as system frequency band and satellite transmission power.
The multi-beam system can improve the communication capacity of the entire system by repeatedly using the frequency band, and a promising method for realizing next-generation large-capacity satellite communication has also been proposed (for example, Non-Patent Document 3).

  However, in multi-beams, inter-beam interference using the same frequency has a great influence on communication quality. Therefore, system resources must be allocated in consideration of power interference from surrounding beams. In mobile satellite communications, users in the service area are unevenly distributed and fluctuate, so in multi-beam, in response to uneven traffic distribution such as traffic concentration on a specific beam, It is necessary to allocate system resources so that the communication capacity is always maximized.

For example, in the Frequency Division Multiple Access (FDMA) system, frequency repetition is performed so that the use frequency bands do not overlap between adjacent beams, and repetition of three colors, four colors, and seven colors is being studied.
In order to use the frequency repeatedly, it is necessary to consider interference between beams using the same frequency (or the same time slot and the same code).

  In addition, considering the characteristics of mobile communication satellites, it is necessary to flexibly cope with temporal and geographical traffic fluctuations. From this background, it is assumed that interbeam interference and traffic fluctuations due to multi-beams are assumed. Resource allocation is required. As an antenna having such performance and function, there is a satellite-mounted multi-beam antenna device including an offset parabolic reflector and a feed element array.

  In addition, ATC (Ancillary Terrestrial Component) has been proposed by MSV (Mobile Satellite Ventures) in the United States as a system that uses the terrestrial system that is allowed only by satellite communication carriers in the satellite mobile communication (MSS) frequency band. ing.

ATC is a system in which satellite and terrestrial frequencies are switched for each beam and the same frequency is shared. That is, the satellite viewing area uses satellite communication, and the shadowing area of the satellite signal in the building uses ground communication with the ATC base station.
In order to realize such an ATC system, it is necessary to use a multi-beam with a narrower beam, and it is necessary to consider interference from an ATC base station on the ground.

  In order to increase the communication capacity, it is necessary to reduce the beam width and increase the frequency repetition. On the other hand, an artificial satellite always performs attitude control, but the attitude cannot be fixed completely. Further, when a large deployable antenna having an outer diameter of 10 m to 20 m is used, although this is also slight, thermal deformation on the orbit occurs, and the beam direction fluctuates. Such fluctuation is called a pointing error, and the directivity of the beam fluctuates.

  In general, in the case of multi-beams, a coverage range EOC (Edge of Coverage) is often covered with a beam width of 3 dB to 4 dB. In this coverage range EOC, the beam directivity varies, The center of the actual beam is deviated from the target center line, and the coverage range EOC changes. Such a change in the coverage range EOC causes a decrease in antenna gain.

  Furthermore, in the case of a large deployable antenna as described above, the beam width becomes an extremely thin beam of about 0.5 [degree] to 1.0 [degree], and when a pointing error occurs with a narrow beam width, the gain change amount is , It becomes several dB or more. As a result, the gain decrease due to the pointing error becomes several dB, and the influence on the communication capacity and communication quality is great.

Yasui et al., “Development of N-STARc and Satellite Control System”, NTT DoCoMo Technical Journal, Vol. 11, no. 11, pp. 67-76, Nov. 2003. Suzuki et al., “Independent pointing control beam forming device for phased array-fed reflector antenna mounted on Engineering Test Satellite VIII”, Theory of Science (B), Vol. J87-B, no. 8, pp. 1053-1062, 2004. M.M. Ueba, et al, “Broadband and scalable mobile satellite communication system for future access networks”, AIAA 2004-3154, 2004.

  In a conventional satellite-mounted multi-beam antenna device, in order to increase the communication capacity, it is necessary to reduce the beam width and increase the number of repetitions. However, for satellite mounting using a large deployable antenna having an outer diameter of 10 to 20 m. In the multi-beam antenna device, the beam width is extremely narrow, about 0.5 to 1.0 [degree], and when a pointing error occurs at this narrow beam width, the gain reduction amount due to the pointing error can be several dB or more. Therefore, there has been a problem that the communication capacity and the communication quality are deteriorated due to the gain reduction accompanying the pointing error.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a satellite-mounted multi-beam antenna device with improved communication capacity and quality by reducing gain reduction due to a pointing error. To do.

A multi-beam antenna device for satellite installation according to the present invention comprises an antenna for radiating multi-beams, a feed array for feeding power to the antenna, and a control means for controlling the feed array, and repeatedly uses the frequency band of the multi-beam. In the satellite-mounted multi-beam antenna apparatus that performs mutual communication with the ground terminal , the feed array is adjacent to the first frequency beam and the first frequency beam under the control of the control means. The antenna beam is supplied to the antenna so that the crossover point where the beam of the frequency of the frequency crosses has a coverage range of about 1 dB, and the same frequency, the same time slot for repeatedly using the frequency band, or , in a direction having the same code, Mar for satellite forming a null of the antenna beam A beam antenna device, a feed array, under the control of the control means, the same frequency at which the repeated use of the frequency band, same time slot, or a plurality of antenna beams having the same code, between each other an orthogonal relationship Between the multiple antenna beams, and between the beams that have other frequencies and repeat the frequency band. The beams are arranged so as to have an orthogonal relationship .

  According to the present invention, it is possible to reduce a gain decrease due to a pointing error, and it is possible to improve communication capacity and quality.

Embodiment 1 FIG.
FIG. 1 is an explanatory diagram showing a satellite-mounted multi-beam antenna device to which Embodiment 1 of the present invention is applied, and schematically shows the overall configuration of a multi-beam communication system using an artificial satellite 1.

In FIG. 1, an artificial satellite 1 includes a satellite-mounted antenna (described later) and is configured to be able to communicate with each other between a satellite gateway station 2 and a ground terminal 3 for satellite communication (for example, a mobile phone). ing.
The multi-beam 4 formed by the satellite-mounted antenna of the artificial satellite 1 includes beams (cells) 5a to 5f to which the same frequency is assigned.

Since the same frequency is assigned to each of the beams 5a to 5f, the frequency can be effectively used. However, for that purpose, since the same frequency is used, it is necessary to reduce the inter-beam interference to a desired level.
As shown in FIG. 1, in order to form many multi-beams, it is necessary to set the antenna aperture diameter D of the satellite-mounted antenna larger than the wavelength λ of the operating frequency. In general, the beam width BW [degree] of a multi-beam is approximately expressed by the following formula (1).

  BW = 70 (λ / D) (1)

  As is clear from the equation (1), it can be seen that the beam width BW is inversely proportional to the antenna aperture diameter D. Therefore, as the antenna aperture diameter D increases, the beam width BW decreases, so that the number of multi-beams can be increased.

On the other hand, if the power and frequency bandwidth allocation of each beam is set to be the same, assuming that the i-th beam is an evaluation beam and the j-th beam is an interfering beam, the signal / interference C in the i-th evaluation beam / I ratio (C / I) _i is expressed by the following equation (2) using the gain G in the evaluation area.

(C / I) _i = _Gij / Σj _{= 1 Gij} (2)

  Therefore, based on the beam width BW given by the equation (1) and the C / I ratio given by the equation (2), the beam layout of the frequency repetition and the size of the region are determined.

FIG. 2 is an explanatory view showing a general artificial satellite 1 and shows a state where a large deployable antenna 6 (hereinafter simply referred to as “antenna 6”) for forming a multi-beam is mounted.
In FIG. 2, a feed array (or defocus feed array) 7 constitutes an antenna feeding unit for creating a multi-beam.
The antenna 6 is accommodated when the artificial satellite 1 is launched, and is deployed on the orbit after the artificial satellite 1 is launched. The antenna 6 is a mesh antenna having an outer diameter of 10 m to 20 m and constitutes a large deployment reflector.

  The feed array 7 is composed of several elements including a radiating element and a diplexer in order to control power feeding to the antenna 6. The radiating element (element antenna 8 described later) has a plurality of array arrangements, and elements such as a dipole, a helical, and a horn are employed. A diplexer that separates transmission / reception frequencies is connected to the radiating element, and a transmission amplifier (usually a multiport amplifier is used) and a reception LNA (low noise amplifier) are connected.

The feed array 7 is generally arranged in the vicinity of the focal point of the antenna 6, but may be defocused by several wavelengths in order to obtain beam flexibility.
FIG. 3 is a plan view showing an arrangement example of the element antennas 8 constituting the feed array 7.
In FIG. 3, the element antenna 8 is configured by arranging elements such as dipoles, helicals, and horns in a triangular arrangement, and here, a case is shown in which 37 elements are arranged in a regular hexagon. .

FIG. 4 is a block diagram showing a specific configuration example of the feed array 7 applied to the first embodiment of the present invention.
In FIG. 4, a feed array 7 includes m element antennas 8 that cooperate with an antenna (reflector) 6, and a feed element 20 that includes m amplifiers (AMP) connected to each element antenna 8. And a beam forming circuit 21 made of BFN (Beam Forming Network) connected to the feed element 20.

  A control circuit 9 for controlling the feed array 7 is connected to the feed array 7. Although not shown here, a diplexer for switching between transmission and reception is inserted between the feed element 20 and each element antenna 8.

  The feed element 20 and the beam forming circuit 21 constituting the feed array 7 are switched under the control of the control circuit 9. That is, the feed element 20 functions as a high-power amplifier when transmitting, and functions as a low-noise amplifier when receiving. FIG. 4 shows a signal flow in the case of transmission.

The beam forming circuit 21 distributes the n multi-beams B1 to Bn as beam signals b1 to bm for m elements. Further, the beam forming circuit 21 constitutes a power feeding circuit for exciting the plurality of element antennas 8 so that a desired excitation amplitude is obtained for each of the beams B1 to Bn.
The beam forming circuit 21 may be configured as an analog line, or may be digitally formed as a DBF (Digital Beam Forming) configured by an ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array). You may apply.

  The beam signals b1 to bm formed by the beam forming circuit 21 are amplified by the feed element 20 and simultaneously emitted as n multi-beams B1 to Bn from each element antenna 8. The multi-beams B1 to Bn are radiated through the antenna 6 in an arrangement as shown in the figure, for example.

5 and 6 are explanatory views showing inter-beam interference. FIG. 5 shows inter-beam interference by the normal method, and FIG. 6 shows inter-beam interference in the method according to the first embodiment of the present invention. ing.
FIG. 5 shows beams 10a and 10b (see solid lines) that use the same frequency, and a beam 11 (see broken lines) having a frequency different from that of the beams 10a and 10b. Here, since the beams 10a and 10b use the same frequency, it is necessary to arrange them at a predetermined interval or more.

This is because, in general, the beams 10a and 10b have interference levels (side lobes) 12a and 12b in addition to the main beam, and the side lobes 12a and 12b enter the beam using the same frequency, so This is because interference occurs at the lobe level. Since this interference wave includes different signals, if the intensity of the interference wave becomes higher than a certain threshold value, communication quality deteriorates due to deterioration of BER (Bit Error Rate), and communication becomes impossible. Therefore, it is necessary to increase the beam interval so that the interference wave is below a certain level.
On the other hand, by separating the beams 10a and 10b, the number of repetitions of the frequency is reduced, so that the frequency utilization efficiency is lowered. In general, repetition with seven colors is often performed.

  The level at which beams cross between adjacent beams is defined as crossover. Multiple beams are placed at a certain level of crossover. The problem here is that as the crossover level becomes smaller, the EOC gain in the coverage decreases, so it is necessary to set the crossover level as high as possible. Usually, a crossover of about 3 dB to 4 dB (FIG. 5). Often).

  This is because if the crossover is set higher than 3 dB, the interference between the beams of the same frequency becomes too large and the BER deteriorates. Conversely, if the crossover is set smaller than 3 dB, the EOC gain becomes too small. This is because the BER is deteriorated and the communication quality is deteriorated for the user at the edge of the beam.

  In general, when the antenna 6 (FIG. 2) is used as a reflector, in addition to the fluctuation caused by the attitude fluctuation of the artificial satellite 1, a fluctuation in the beam direction due to the thermal deformation of the antenna 6 occurs, and the pointing error due to such fluctuation is 0. It is known that about 1 [degree] occurs.

  In particular, as is clear from the above-described equation (1), in the case of the antenna 6 having an outer diameter of 10 to 20 m, the beam width BW is 0.5 to 1.0 [degree] when the S band (2 GHz band) frequency is reached. The degree becomes extremely thin. Therefore, even if the pointing error is about 0.1 [degree] at most, it cannot be ignored with respect to the beam width BW, and the gain reduction due to the pointing error is several dB.

Therefore, in the first embodiment of the present invention, as shown in FIG. 6, in order to reduce the gain reduction due to the pointing error, the crossover level between the beams is about 1 dB (in fact, there is a variation depending on the beam, The beams 13a, 13b, 14, and 15 are arranged densely so that it is desirable to set 1 dB ± 0.5 dB.
In FIG. 6, beams 13a and 13b (see solid lines) using the same frequency are spaced apart from each other, but beams 14 and 15 (see broken lines) having different frequencies are each beam 10a, 10b in FIG. 11 is more densely arranged.

As shown in FIG. 6, by arranging the beams 13a, 13b, 14, and 15 densely, the interference of the beams 13a and 13b having the same frequency is suppressed, and the crossover level becomes high.
By arranging the beams densely, fluctuations in the crossover level due to pointing errors are suppressed and reduced, and gain reduction is reduced. However, if the beam interval is set to be narrow and dense, the beam interval of the same frequency is narrowed accordingly, so that interference increases, and there is a problem that communication cannot be performed due to deterioration of the C / I ratio due to interference.

  Therefore, as shown in FIG. 6, by adjusting the excitation amplitude phase of the feed array 7, the interference levels (side lobes) of the nulls 16a and 16b are formed in the direction of the beam using the same frequency.

  That is, since the beams 13a and 13b using the same frequency are determined in advance, the excitation amplitude phase is adjusted so that the nulls 16a and 16b of the beam are formed in the specific direction. Thereby, interference can be reduced.

  Here, the nulls 16a and 16b are for reducing the side lobe level of the radiation pattern and are not necessarily null, but are expressed as “null” in the sense of reducing the level. In addition, when the beam is formed so as to form a null, the peak direction of the beam may shift, so whether to place emphasis on null control or to adjust the peak direction of the beam in consideration of the gain in the user direction , Depending on the beam forming method.

FIG. 7 is an explanatory diagram showing an example of a radiation pattern, and shows a relationship between a radiation pattern (power [dB]) and a pointing error (angle [degree]).
In FIG. 7, when the coverage range EOC is “3 dB” and the pointing error is 0.1 [degree], the gain reduction amount due to this fluctuation is about 3 dB.
On the other hand, when the coverage range EOC is “1 dB” and the pointing error is 0.1 [degree], the gain reduction amount due to this fluctuation is about 0.5 dB.
Thus, it can be seen that by setting the crossover level between the beams to about “1 dB”, the amount of gain reduction is improved (3 dB → 0.5 dB).

FIG. 8 is an explanatory diagram showing the area of the interference area depending on the presence or absence of null control, and shows an example of calculating the interference level in the beam using the same frequency.
In FIG. 8, the horizontal axis represents the C / I ratio, and the vertical axis represents the ratio [%] of the area satisfying the desired C / I ratio among the beam areas using the same frequency. A solid line indicates a characteristic without null control, and a broken line indicates a characteristic with null control.

As is clear from FIG. 8, the coverage range [%] changes depending on the presence or absence of null control in the same frequency direction. By performing null control, the C / I ratio is about twice as high as the desired value. It can be seen that the area increases.
Therefore, according to the satellite-mounted multi-beam antenna device according to the first embodiment of the present invention, the crossover level can be increased, so that the EOC gain is increased and the gain reduction due to the pointing error is reduced. Can do.

In addition, although the example of the aperture diameter D and S band frequency of the antenna 6 was shown here, it cannot be overemphasized that the same effect is acquired also outside this range.
Further, the configuration of the feed array 7 may be an active array that directly uses an amplifier other than a semi-active array that uses a multi-port antenna.

  As described above, the satellite-mounted multi-beam antenna device (see FIGS. 1 to 4) according to Embodiment 1 of the present invention has a multi-beam frequency band for the purpose of improving the communication capacity of the entire communication system. Are used repeatedly to perform mutual communication with the ground terminal 3, an antenna 6 for radiating multi-beams, a feed array 7 for feeding power to the antenna 6, and a control circuit for controlling the feed array 7 ( Control means) 9.

  The feed array 7 has a coverage range in which the crossover point where the beam of the first frequency and the beam of the second frequency adjacent to the beam of the first frequency cross is around 1 dB under the control of the control circuit 9. The antenna beam is supplied to the antenna 6 so as to have EOC (see FIG. 6), and the null of the antenna beam is used in the direction having the same frequency, the same time slot, or the same code in which the frequency band is repeatedly used. Form.

In this way, frequency repetition is performed so that the EOC covered by the beam is covered around 1 dB from the peak, and a null of the antenna beam is formed in the same frequency, the same time slot, or the same code direction where the frequency repetition is used. Since the crossover level can be increased by reducing the interference at the same frequency, it is possible to increase the EOC gain and reduce the gain reduction due to the pointing error.
Therefore, the communication capacity of the entire communication system can be improved, and the communication capacity and quality can be improved.

Embodiment 2. FIG.
Although not particularly mentioned in the first embodiment (FIG. 6), as shown in FIG. 9, a plurality of beams are formed so that the peaks of two or more beams having the same frequency f1 coincide with the null points. May be.
FIG. 9 is an explanatory diagram showing inter-beam interference according to the second embodiment of the present invention. In forming a multi-beam, the beams are arranged so that the peaks of the beams of the same frequency f1 overlap in the null direction of a certain beam. Indicates the state. The overall configuration of the satellite-mounted multi-beam antenna device according to Embodiment 2 of the present invention is the same as that described above (see FIGS. 1 to 4).

  In FIG. 9, the beams 31a and 31b having the same frequency f1 are arranged on both sides of the beam 32 having a frequency different from the frequency f1, and the peak positions (see dotted lines) of the beams 31a and 31b coincide with the peak positions. Nulls 33a and 33b are formed as shown. That is, the null 33b of the beam 31a matches the peak position of the beam 31b, and the null 33a of the beam 31b matches the peak position of the beam 31a.

  In this manner, the beams 31a and 31b are formed so that the peaks of the two or more beams 31a and 31b having the same frequency f1 coincide with the null points 33a and 33b, and the orthogonality between the beams is obtained, so that the beams Inter-beam interference can be further reduced by utilizing the orthogonality between the beams.

  FIG. 10 is an explanatory diagram showing a calculation example in which a null is formed. In order to reduce interference with respect to three beams using the same frequency (see a dashed line, a broken line, and a solid line), the excitation amplitude phase is controlled, A state is shown in which nulls 34a, 34b, and 34c that coincide with the peaks (see dotted lines) of the respective beams are formed.

In FIG. 10, it can be seen that the nulls 34a, 34b, 34c are formed in the peak direction of each beam having the same frequency. That is, the null 34c of the broken line beam coincides with the peak position of the one-dot chain line beam, and the nulls 34a and 34c of the broken line beam coincide with the respective peak positions of the solid line beam and the one-dot chain line beam. The beam null 34b coincides with the peak position of the broken beam.
A beam (not shown) having a different frequency is disposed between three beams (see the dashed line, the broken line, and the solid line).

  As described above, the feed array 7 (see FIG. 4) according to the second embodiment of the present invention uses the same frequency f1 (or the same time slot or the same time slot) that repeatedly uses the frequency band under the control of the control circuit 9. A plurality of antenna beams 31a and 31b having the same code) are arranged so as to maintain an orthogonal relationship between them, and a plurality of other beams having a plurality of other frequencies are provided between and around the plurality of antenna beams 31a and 31b. The beam 32 is disposed (see FIG. 9). Further, the beams are arranged so as to have an orthogonal relationship between the beams having other frequencies and repeatedly using the frequency band.

In this way, the beams are arranged so that the peaks of the beams of the same frequency overlap in the null direction of a certain beam, and the beams are formed so that the peaks of two or more beams of the same frequency coincide with the null points. Inter-beam interference can be further reduced by obtaining orthogonality between beams and utilizing orthogonality between beams.
Therefore, the communication capacity of the entire communication system can be improved, and the communication capacity and quality can be improved.

  Here, an example in which the beam widths of the multi-beams are almost the same and the crossover level is the same is shown. However, basically, the beam width does not depend on the beam width, and multiple beams having different beam widths are used. The present invention can be applied even when they are arranged or when the beam width is different for each beam. For example, in areas where urban areas are concentrated (Kanto, Kinki, etc.), many beams are placed to increase the crossover level, and in other land and ocean areas, the crossover level is reduced to reduce interference. The beam may be arranged so as to be lowered or the beam width may be arranged so as to reduce the number of beams.

Embodiment 3 FIG.
Although not particularly mentioned in the first and second embodiments (FIGS. 6 and 9), a null may be formed at a detected point only during the time when the same frequency is used.
Normally, in the case of a super multi-beam exceeding 100 beams, there are a large number of inter-beam interferences, but since the transmission power is limited, the number of beams that are actually communicated is limited. Therefore, there are many assignments of beams using the same frequency, which are determined in advance. However, the assignment beams of the same frequency used at the same time are limited, and this assignment beam changes every moment.

Therefore, in order to dynamically suppress interference only in the area of the beam that is actually used, it is desirable to provide a null only in the beam direction using the same frequency at the same time.
In this case, the interference level in the same frequency beam direction that is not used increases instantaneously, but there is no problem because it is not used.
In the first embodiment, since the null direction is fixed, it is not possible to cope with interference level fluctuations due to interference or fluctuations from a strong signal. However, by performing dynamic control, interference can be reduced. And the deterioration of C / I can be suppressed.

The third embodiment of the present invention will be described below with reference to FIG. 11 together with FIGS.
In this case, the control circuit 9 detects a point where the same frequency is used as a point where the null is formed, and feeds so as to form a null at the detected point only during the time when the same frequency is used. The array 7 is controlled.

FIG. 11 is an explanatory diagram showing an example of C / I analysis according to Embodiment 3 of the present invention. The C / I when the number of spots of the same frequency beam to be null-controlled is changed to 5, 10, and 16 points. An example of I analysis is shown.
In FIG. 11, when the number of points is 5 (refer to the characteristics of black triangle points), the coverage range EOC is the largest, and C / I can be improved by reducing the direction in which nulls are formed. I understand. Therefore, C / I can be improved by detecting only the direction using the same frequency and dynamically forming a null.

As described above, the control circuit 9 according to the third embodiment of the present invention controls the antenna beam null to be formed in the same frequency, the same time slot, or the same code direction in which frequency repetition is used, The instant at the time of communication is monitored, and a null is adaptively formed at the detection point only during the time when the same frequency is used.
As described above, by performing dynamic null control, it is possible to reduce interference only at the point where the interference is suppressed, and thus it is possible to suppress a decrease in gain.

Embodiment 4 FIG.
Although not particularly mentioned in the first to third embodiments, the crossover point is set to approximately 3 dB by forming a plurality of beams using the same element by changing the beam direction by amplitude phase control. The beam forming network may be configured to cover an area of the coverage range.
The fourth embodiment of the present invention will be described below with reference to FIG. 12 together with FIGS.

  In this case, the feed array 7 includes a plurality of element antennas 8 selected by the control circuit 9, and the plurality of element antennas 8 form a beam having a crossover point of around 1 dB under the control of the control circuit 9. Thus, the amplitude phase control is performed, and the amplitude phase control is changed, whereby the beam direction is changed to form a plurality of beams. The plurality of beams is composed of four circular beams (or three circular beams, two elliptical beams), and the beam forming network covers the area 40 of the coverage range where the crossover point is approximately 3 dB. Configure.

  Generally, in order to reduce side lobes, it is necessary to adjust the excitation amplitude phase, and to form one beam, it is necessary to excite a plurality of element antennas 8. In addition, when the number of elements is small, the beam formation is restricted, so that the side lobe is reduced by using 10 elements or more.

  At this time, as the number of beams increases, the scale of the beam forming circuit (BFN) 21 increases. The beam forming circuit 21 can be an analog method when the number of beams is small. However, when the beam size is 100, the hardware size increases when the beam size is 100, and the application of the DBF that forms the beam by the digital method is appropriate. .

In the case of DBF, beam formation is performed by a digital circuit, so even if the number of beams increases, it can be handled by increasing the digital circuit scale. However, as the number of beams increases, a problem arises that the circuit scale becomes complicated and the weight and power consumption increase.
Here, when the crossover level is set to 1 dB, the number of beams is about four times that in the case of 3 dB. A system configuration according to Embodiment 4 of the present invention for reducing the scale of the beam forming circuit will be described below.

  When the crossover level is set to 1 dB, the excitation element antenna is not determined for each beam, but by using the excitation element antenna in the case of the crossover level of 3 dB, the amplitude phase of the excitation element antenna is changed to 4 Beams can be created at the same time.

FIG. 12 is an explanatory diagram showing an example in which each of the areas 41a to 41d is formed by four beams.
In FIG. 12, an area 40 indicated by a broken-line contour indicates the beam coverage range when the crossover level is 3 dB.
On the other hand, areas 41a to 41d indicated by solid line contours indicate beam coverage ranges when the crossover level is 1 dB.

As is apparent from FIG. 12, by setting the crossover level of each beam to 1 dB, the area (coverage range) 40 in the case where the crossover level is 3 dB is covered with 4 beams as in the areas 41a to 41d. I understand.
At this time, even if there are four beams, the area (coverage range) 40 covered by each beam does not substantially change. Therefore, by using only the same element antenna, only the excitation amplitude phase is changed, so that four beams are formed simultaneously. can do.

Although FIG. 12 shows a case where the area 40 is covered with a plurality of circular beams (crossover level is 1 dB), the present invention is not limited to this.
For example, as shown in FIG. 13, the area 40 may be covered by areas (coverage ranges) 42a to 42c of a plurality of beams having a crossover level of 1.5 dB.
Further, as shown in FIG. 14, the same area 40 may be covered with two beams 43a and 43b made of elliptical beams.

  In both cases of FIGS. 13 and 14, as in the case of FIG. 12, three or two beams can be simultaneously formed by changing only the excitation amplitude phase. The number of beams can be increased 2 to 4 times without increasing the size.

FIG. 15 is an explanatory diagram showing an example of the arrangement of multi-beams on a specific map, showing an example in which the crossover level of each beam is 3 dB.
FIG. 16 is an explanatory view showing an example of multi-beam arrangement in the case where a plurality of beams are generated simultaneously, and only the excitation amplitude phase is changed using the same element antenna 8 as the element antenna forming the multi-beam in FIG. Thus, an arrangement example in the case where four beams are generated simultaneously is shown.
As shown in FIGS. 15 and 16, a beam with a high crossover can be produced.

  15 and 16 show the case where the beam width (crossover level) is the same, the crossover level may be changed for each beam. For example, a large number of beams may be set in areas where urban areas are concentrated (Kanto, Kinki, etc.), and a small number of beams may be set in other land areas.

In the marine region, the number of beams may be set to be smaller, and more beams may be formed in an area having a larger communication capacity, and the number of beams may be set to be smaller in an area having a smaller communication capacity. Thereby, the total number of beams can be reduced, and the beam forming circuit scale can be further reduced. Thus, even if the crossover level is changed for each area corresponding to the communication amount, the necessary communication amount can be ensured.
The above concept is common to the above-described first to third embodiments, and needless to say, is common to the fifth and sixth embodiments described later.

  As described above, the feed array 7 according to the fourth embodiment of the present invention includes the plurality of element antennas 8 selected by the control circuit 9, and the plurality of element antennas 8 are under the control of the control circuit 9. A crossover point where a beam having a frequency and a beam having a different frequency adjacent thereto are crossed is selected to form a beam having about 1 dB, and a beam having a crossover point having about 1 dB is formed. Amplitude phase control is performed, and the amplitude phase control is changed to change the beam direction to form a plurality of beams.

The plurality of beams is composed of four circular beams (or three circular beams, two elliptical beams), and the beam forming network covers the area 40 of the coverage range where the crossover point is approximately 3 dB. Configure.
In this manner, by forming a plurality (2 to 4) of beams using the same element antenna 8 (feeding element), the configuration of the beam forming circuit (BFN) 21 can be reduced in size.

Embodiment 5 FIG.
Although not particularly mentioned in the first to fourth embodiments, as illustrated in FIGS. 17 and 18, when a reception signal received at the first frequency f1 is extracted, the first beam 50 is adjacent. A new beam may be formed by combining the diversity reception so that it is substantially in phase with the first frequency f1 received by one or more beams 51.
The fifth embodiment of the present invention will be described below with reference to FIGS. 17 and 18 together with FIGS.

In general, when the crossover level is 3 dB, the gain of adjacent beams is the same level when the crossover point is 3 dB down, but of course, the gain immediately decreases with the angle.
However, when the crossover level is 1 dB, the adjacent crossover points are 1 dB down, and the gain does not rapidly decrease with the angle.

Therefore, if a receiver that receives the same frequency is provided for adjacent beams, the adjacent beams can be received at a relatively high level.
Therefore, if the maximum ratio combining is performed so that the reception levels of adjacent beams other than the desired beam are in phase, the reception level can be increased. Since noise is not coherent, it is only synthesized in terms of power.

FIG. 17 is a block diagram schematically showing a receiver 60 according to the fifth embodiment of the present invention, and shows a configuration when the feed array 7 (see FIG. 4) functions as a receiver.
Here, among the plurality of beams 50 to 53 (frequency f0 to f3), the first and second receivers 61 and 62 corresponding to the first beam 51 (first frequency f1), and the second beam 52 are used. Paying attention to the third and fourth receivers 63 and 64 corresponding to (second frequency f2), the output signals (received signals) S1 and S2 and the synthesis of the first and fourth receivers 61 and 64 The signal S3 (= S1 + S2) is shown.

  In FIG. 17, a receiver 60 constituted by the feed array 7 includes a first receiver 61 that receives the first frequency f <b> 1 in relation to the first beam 51 of the multi-beams, A second receiver 62 for receiving the frequency f0 adjacent to the frequency f1 and a third receiver for receiving the second frequency f2 in relation to the second beam 52 adjacent to the first beam 51. A receiver 63 and a fourth receiver 64 that receives the frequency f1 of the first beam 51 are provided.

First and second receivers 61 and 62 having frequencies f1 and f0 are connected to the first beam 51, and second beams 52 adjacent to the first beam 51 are connected to first beams 51 having frequencies f2 and f1. 3 and 4th receivers 63 and 64 are connected.
In other words, the fourth receiver 64 having the first frequency f1 is also connected to the second beam 52 adjacent to the first beam 51.

  When the reception signal received at the first frequency f1 is taken out, it is substantially in phase with the first frequency f1 received by the second beam 52 (one or more beams) adjacent to the first beam 51. Thus, a new beam composed of the combined signal S3 (= S1 + S2) is formed by combining the output signals S1 and S2 of the first and fourth receivers 61 and 64 with diversity reception.

In this way, the maximum reception of the output signals S1 and S2 from the first and fourth receivers 61 and 64 is combined so as to be in phase, thereby increasing the final reception level of the combined signal S3. it can.
In the case of a normal crossover of about 3 dB, since the gain of adjacent frequency beams is small, improvement in reception level cannot be expected even if they are combined, but according to the fifth embodiment of the present invention, as described above. By setting the crossover level to a high value, the merit of synthesis is demonstrated.

FIG. 18 is an explanatory diagram showing the antenna reception gain at the time of combining the diversity maximum ratio, and shows the gain increase of the combined signal S3 when the reception output signals S1 and S2 of the two adjacent beams 51 and 52 are combined in phase. Yes.
In FIG. 18, it can be seen that the reception level is increased by about 5 dB by combining the two beams 51 and 52 by electric field synthesis. However, this synthesis increases the noise level by about 3 dB, so the C / N ratio increases by about 2 dB.

Needless to say, not only the first beam 51 (first frequency f1) but also other beams can be obtained in the same manner based on the adjacent beams, and the same effect can be obtained.
Further, not only the second beam 52 adjacent to the first beam 51 but also the third beam 53 adjacent to the second beam 52 is provided with a receiver (not shown) having the first frequency f1. The reception level may be further increased by combining the three beams.

  As described above, according to the fifth embodiment (FIG. 17) of the present invention, in relation to the first beam 51, the first receiver 61 that receives the first frequency f1, and the first reception. With a second (one or more) receiver 62 receiving another frequency f0 adjacent to the machine 61 and in relation to the second beam 52 adjacent to the first beam 51, the first A third receiver 63 that receives the second frequency f2 adjacent to the first frequency f1, and a fourth receiver 64 that receives the first frequency f1.

  Then, when extracting the signal received at the first frequency f1, the output signals S1, S2 of the first frequency f1 received by one or more adjacent first and second beams 51, 52 are: Diversity reception combining is performed so as to be substantially in phase, thereby forming a new beam (combined signal S3) with high gain.

  Note that, here, an example is shown in which signals are combined after reception of two beams formed at the same time, but the beam may be combined by switch switching with only one receiver. Further, the beam may be formed by scanning the beam direction as described in the fourth embodiment, and a high gain beam can be obtained without increasing the number of receivers. Furthermore, as an example of diversity, the case of maximum ratio combining has been shown as an example, but it is effective even with selective combining by switch switching, equal gain combining, or time diversity.

In this way, two or more receivers are provided in relation to one beam, and the same frequency component is received from the receiver 60 connected to the first beam 51 to be used and the second beam 52 adjacent thereto. When there is a receiver to receive, the gain at the time of reception can be improved by combining the beams 51 and 52 with the maximum diversity ratio.
Further, since the reception gain at the satellite is equivalently improved, G / T (total performance index) is improved, and the ground terminal 3 (see FIG. 1) can be downsized.

Embodiment 6 FIG.
In the fifth embodiment (FIG. 17), a plurality of adjacent beams are combined to form a reception signal. However, as shown in FIG. 19, two orthogonal linearly polarized waves (or right and left rotations are included). A pair of feeding terminals (hereinafter simply referred to as “terminals”) 71 and 72 having first and second polarizations corresponding to two circular polarizations) are provided in each element antenna 8, First and second receivers 75 and 76 for synthesizing and receiving output signals and an output circuit 77 are provided, and a first polarized wave (an output signal of the terminal 71) of each element antenna 8 is synthesized. The received beam signal S13 may be formed on the basis of the beam signal S11 and the second beam signal S12 obtained by synthesizing the second polarized wave (output signal of the terminal 72) of each element antenna 8.

The sixth embodiment of the present invention will be described below with reference to FIG. 19 together with FIGS.
FIG. 19 is a block diagram schematically showing a functional configuration of a feed array 7 (receiver) according to Embodiment 6 of the present invention, and shows a case where the feed array 7 functions as a receiver.
In FIG. 19, of the first and second beams B11 and B12 (same frequency) to be communicated, the first beam B11 (solid line) indicates the first polarized beam, and the second beam B12. (Dotted line) indicates the second polarized beam.

The plurality of element antennas 8 (receiving antennas) are provided with a terminal 73 having a first polarization and a terminal 74 having a second polarization.
The first and second polarized waves correspond to two orthogonal linearly polarized waves (vertical and horizontal) or two circularly polarized waves including right and left rotations.

The output signals from the terminals 71 of the element antennas 8 are combined by the first combining circuit 73 and input to the first receiver 75. That is, combining a plurality of element antennas in one beam formation is as described in the first embodiment.
Similarly, each output signal from the terminal 72 of each element antenna 8 is combined by the second combining circuit 74 and input to the second receiver 76.

The first receiver 75 synthesizes the first polarization of each element antenna 8 in cooperation with the first synthesis circuit 73, thereby generating the first beam signal S11 corresponding to the first beam B11. Form.
Similarly, the second receiver 76 synthesizes the second polarization of each element antenna 8 in cooperation with the first synthesis circuit 74 to thereby generate the second beam corresponding to the second beam B12. A signal S12 is formed.

  The output circuit 77 compares the reception levels of the first and second beam signals S11 and S12 and selects the beam having the higher reception level or outputs the first and second beam signals S11 and S12 in phase. Or by adjusting both the phase and amplitude so as to increase the reception level, and output as a received beam signal S13.

  In this case, the output circuit 77 has the same addition function as described above (see FIG. 17), and the first beam signal S11 obtained by synthesizing the first polarized wave (output signal of the terminal 71) of each element antenna 8; The second beam signal S12 obtained by synthesizing the second polarized wave (the output signal of the terminal 72) of each element antenna 8 is synthesized with a diversity circuit that forms the received beam signal S13 by synthesizing the second beam signal S12 so as to be in phase. ing.

  In general, the antenna used for the ground terminal 3 for mobile communication (see FIG. 1) is a circularly polarized wave instead of a linearly polarized wave in the case of satellite communication, and also when the ground terminal 3 is a mobile phone, A circularly polarized antenna is used. In the case of using circularly polarized waves, it is known that the antenna configuration becomes more complicated and larger than that of linearly polarized waves.

When the ground terminal 3 is a mobile terminal, a small antenna is particularly required, but it is difficult to reduce the circularly polarized antenna. The mobile phone on the ground uses linearly polarized waves, and some antennas have built-in antennas. However, circularly polarized antennas are usually thick and protrude from the terminal. Therefore, even in the case of circular polarization, it is conceivable to reduce the size of the terminal antenna by using a linearly polarized antenna for the portable terminal.
However, since the artificial satellite 1 is circularly polarized, a polarization loss of about 3 dB may occur and communication performance may deteriorate. Accordingly, increasing the transmission power in the portable terminal hinders the miniaturization of the terminal. Therefore, in order to reduce the size of the portable terminal, it is necessary to increase the reception capability on the artificial satellite 1 side. .

In the sixth embodiment of the present invention, in view of the above problem, the artificial satellite 1 receives two polarized waves (first and second polarized waves) to compensate for the polarization loss. That is, if the artificial satellite 1 can receive two circularly polarized waves (right-handed and left-handed), even if the ground terminal 3 is linearly polarized, it can be received without causing a polarization loss.
Moreover, even if the artificial satellite 1 has two orthogonal linearly polarized waves, polarization loss can be eliminated by performing polarization control.

  Therefore, by providing terminals 71 and 72 having two polarizations in each element antenna 8, the first beam B11 (first polarization) is used for the first beam B11 using the plurality of element antennas 8. By forming the signal S11, forming the second beam signal S12 with respect to the second beam B12 (second polarization), and performing polarization diversity in the output circuit 77 (diversity circuit), polarization loss It is possible to form the reception beam signal S13 without the above.

  In FIG. 19, after the beams from the terminals 71 and 72 are combined, the output circuit 77 performs polarization diversity. However, each element antenna 8 is provided with a diversity circuit, and the polarization diversity is first performed. The same diversity effect can be obtained by combining the beam signals from the element antennas 8 after the diversity.

  As described above, the feed array 7 according to the sixth embodiment of the present invention is provided in each of the plurality of element antennas 8 and the plurality of element antennas 8, and two orthogonal linearly polarized waves, or right-handed and left-handed. A pair of terminals 71 and 72 having first and second polarizations corresponding to two circular polarizations including the first and second receivers 75 provided on each of the pair of terminals 71 and 72, 76 and an output circuit 77 for selecting or synthesizing the output signals of the first and second receivers 75 and 76.

The first receiver 75 forms the first beam signal B11 by synthesizing the first polarization of each element antenna 8, and the second receiver 76 sets the second polarization of each element antenna 8. A second beam signal B12 is formed by combining the waves.
The output circuit 77 compares the reception levels of the first and second beam signals B11 and B12 and selects the beam having the higher reception level or outputs the first and second beam signals B1 and B12 in phase. And are output as a received beam signal S13.

Here, an example is shown in which signal combining is performed after reception of two simultaneously formed beams of polarized waves. However, the beam may be combined by switch switching with only one receiver, thereby reducing the number of receivers. A beam with high gain can be obtained without increasing it.
Further, as an example of diversity, the case of maximum ratio combining has been shown as an example, but it is effective even with selective combining by switch switching, equal gain combining, or time diversity.
Furthermore, although the case of the reception beam signal is shown here, even in the case of the transmission beam, it is possible to perform polarization diversity so as to increase the gain of the ground terminal.

Further, in the case of a transmission beam, even if the power supply circuit transmits only one of right-handed and left-handed circularly polarized waves, if the ground terminal is a linearly polarized wave, only a polarization loss of about 3 dB occurs. Therefore, there is an advantage that the configuration of a high-power satellite feeding circuit can be simplified.
When it is desired to increase the transmission EIRP (Equivalent Isotropy Radiated Power) of a specific beam, the polarization loss can be compensated by doubling the transmission power of the beam. In this way, it is possible to change the feeding circuit configuration of the reception and transmission beams.

In this way, by providing two or more receivers 75 and 76 corresponding to each polarization in one element antenna 8 and diversity combining the beam signals S11 and S12 of each polarization, gain improvement at the time of reception is achieved. Can be realized.
Further, since the reception gain at the artificial satellite 1 is equivalently improved, the G / T at the artificial satellite is improved, and the antenna of the ground terminal 3 can be downsized.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows the multi-beam communication system with which Embodiment 1 of this invention is applied. It is a block diagram which shows the satellite system to which Embodiment 1 of this invention is applied. It is a top view which shows the example of an arrangement | sequence of the element antenna which comprises the feed array which concerns on Embodiment 1 of this invention. It is a block diagram which shows the specific structural example of the feed array which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the interference state between the beams by the normal system without beam control. It is explanatory drawing which shows the interference state between beams at the time of reducing the interference between beams by Embodiment 1 of this invention. It is explanatory drawing which shows the relationship between the radiation pattern by Embodiment 1 of this invention, and a pointing error. It is explanatory drawing which shows the area | region of the interference area by the presence or absence of null control by Embodiment 1 of this invention. It is explanatory drawing which shows the orthogonality of the beam by Embodiment 2 of this invention. It is explanatory drawing which shows the example of calculation of the orthogonality of the beam by Embodiment 2 of this invention. It is explanatory drawing which shows the example of analysis of C / I at the time of changing the number of points which carry out null control by Embodiment 3 of this invention. It is explanatory drawing which shows beam arrangement | positioning at the time of covering 3 dB contour with 1 dB contour 4 beams by Embodiment 4 of this invention. It is explanatory drawing which shows beam arrangement | positioning at the time of covering 3 dB contour with 1.5 dB contour 3 beam by Embodiment 4 of this invention. It is explanatory drawing which shows the beam arrangement | positioning at the time of covering 3 dB contour with the elliptical contour 2 beam by Embodiment 4 of this invention. It is explanatory drawing which shows the example of beam arrangement | positioning at the time of making each beam into 3 dB contour by Embodiment 4 of this invention. It is explanatory drawing which shows the example of beam arrangement | positioning at the time of covering 3 dB area | region with four beams by Embodiment 4 of this invention. It is a block diagram which shows the feed array structure which performs the diversity maximum ratio synthesis | combination by Embodiment 5 of this invention. It is explanatory drawing which shows the antenna receiving gain at the time of performing diversity maximum ratio combining by Embodiment 5 of this invention. It is a block diagram which shows the feed array structure which performs the polarization diversity by Embodiment 6 of this invention.

Explanation of symbols

  1 artificial satellite, 3 ground terminal, 4 multi-beam, 5 beam using the same frequency, 6 antenna (large deployment reflector), 7 feed array, 8 element antenna, 9 control circuit, 13a, 13b beam of the same frequency f1, 14 different Beam of frequency f2, 15 Beam of different frequency f3, 16a, 16b Null, 20 Feed element (amplifier), 21 Beam forming circuit (BFN), 31a, 31b Beam of the same frequency f1, 32 Beam of different frequency f2, 33a, 33b Null, 40 area (3 dB contour), 41a, 41b, 41c, 41d 4 beam area (1 dB contour), 42a, 42b, 42c 3 beam beam area (1 dB contour), 43a, 43b 2 elliptical beams Beam area (1dB contour ), 51 1st beam, 52 2nd beam, 60 receiver, 61 1st receiver, 62 2nd receiver, 63 3rd receiver, 64 4th receiver, S1, S2 output Signal (reception level), S3 combined signal (maximum ratio combined output), B11, B12 combined beam, 71, 72 terminals, 73, 74 combining circuit, 75 first receiver, 76 second receiver, 77 output circuit (Diversity circuit).

Claims (5)

An antenna for radiating a multi-beam, a feed array that feeds power to the antenna, and a control unit that controls the feed array are provided, and the frequency band of the multi-beam is repeatedly used to communicate with a ground terminal. A satellite-mounted multi-beam antenna device for communication,
The feed array is under the control of the control means,
The antenna beam with respect to the antenna has a coverage range in which the crossover point where the beam of the first frequency and the beam of the second frequency adjacent to the beam of the first frequency cross is about 1 dB. And supply
In order to form a null of the antenna beam in the direction having the same frequency, the same time slot, or the same code that repeatedly uses the frequency band ,
A plurality of antenna beams having the same frequency, the same time slot, or the same code that repeatedly use the frequency band are arranged so as to maintain an orthogonal relationship between each other,
Arranging a plurality of beams having a plurality of other frequencies between and around the plurality of antenna beams;
A satellite-mounted multi-beam antenna apparatus , wherein beams are arranged so as to have an orthogonal relationship between beams having the other frequencies and repeatedly using the frequency band . The control means includes
Detecting the point where the same frequency is used as a point to form the null,
The satellite-mounted multi-beam antenna device according to claim 1 , wherein the feed array is controlled so that a null is formed at the detected point only during a time when the same frequency is used. The feed array comprises a plurality of element antennas selected by the control means;
The plurality of element antennas are under the control of the control means,
Amplitude phase controlled so as to form a beam having the crossover point around 1 dB,
By changing the amplitude phase control, the beam direction is changed to form a plurality of beams,
The plurality of beams includes four circular beams, three circular beams, or two elliptical beams, and covers a coverage area where the crossover point is approximately 3 dB. multibeam antenna device for satellite according to claim 1 or claim 2, characterized in that it constitutes a. The feed array is
A first receiver that receives a first frequency f1 and a second receiver that receives a frequency f0 adjacent to the first frequency f1 in relation to a first beam of the multi-beams; With
A third receiver for receiving a second frequency f2 in relation to a second beam adjacent to the first beam; and a fourth receiver for receiving the frequency f1 of the first beam. Prepared,
When extracting a reception signal received at the first frequency f1, the phase is substantially in phase with the first frequency f1 received by one or more beams adjacent to the first beam. The satellite-mounted multi-purpose satellite according to any one of claims 1 to 3 , wherein a new beam is formed by combining the output signals of the first and fourth receivers with diversity reception. Beam antenna device. The feed array is
A plurality of element antennas;
A pair of terminals provided on each of the plurality of element antennas and having first and second polarized waves corresponding to two orthogonal linearly polarized waves or two circularly polarized waves including right and left rotations;
First and second receivers provided at each of the pair of terminals;
An output circuit for selecting or combining output signals of the first and second receivers,
The first receiver forms a first beam by combining first polarizations of the plurality of element antennas;
The second receiver forms a second beam by combining the second polarizations of the plurality of element antennas;
The output circuit compares the reception levels of the first and second beams and selects a beam having a higher reception level, or combines the first and second beams so as to be in phase. or synthesized by such received signals by adjusting both amplitude and phase is maximized, according to any one of the outputs as a reception beam from claim 1, wherein up to claim 3 Multi-beam antenna device for satellite use.

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