JP2013098782A - Relay satellite and satellite communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a relay satellite having high frequency utilization efficiency in the case of performing broadcast communication.SOLUTION: A relay satellite comprises: a group of reception signal conversion means for receiving a signal from a transmission station in a reception beam area and performing frequency conversion processing; a group of division means for performing division into a plurality of signals; a digital switch matrix part 300 for allocating a frequency band to each signal having been divided and outputting the signal in units of a transmission beam area that is to be a transmission destination; a group of delay means for performing delay processing on the signal output in units of the transmission beam area; a group of combination means for combining signals after the delay processing has been performed; and a group of transmission means for converting the signal after being combined to that in a radio frequency band, and transmitting the converted signal to the transmission beam area that is the transmission destination. When a broadcast signal is transmitted to two or more reception stations; the digital switch matrix part 300 allocates each broadcast signal generated by copying the broadcast signal to the same frequency band, and the group of the delay means gives the copied broadcast signals time delay differing from each other.

Description

  The present invention relates to a relay satellite that transmits a signal received from a transmitting station to the receiving station.

  Conventionally, there is a multi-beam satellite system that relays using multi-beams, and a technique for effectively using the frequency in such a system is disclosed in Non-Patent Document 1 below. Specifically, effective utilization of the frequency is realized by collecting a plurality of adjacent beams as one cluster and repeatedly using the same frequency in the plurality of clusters. The allocation frequency to each beam in one cluster needs to be allocated with a different frequency so as not to overlap between the beams. For example, when the system band allocated to the satellite system is Bs and one cluster is configured by M beams, the total band that can be used by M beams is Bs. In this case, the average bandwidth available per beam is Bs / M.

Hitoshi Miyoshi et al. "Onboard Equipment Technology in Next Generation Mobile Satellite Communication Systems" IEICE Technical Report SAT 2003-113, October 2003

  However, according to the above-described conventional technology, the same applies to 1-to-M broadcast communication that distributes the same signal from one ground station to each mobile station in M beams, such as broadcasting, and in the downlink, It is necessary to arrange the frequency so that the frequency of the broadcast signal does not overlap among the M beams. Therefore, if the broadcast signal bandwidth is Bb, the bandwidth required for one-to-M broadcast communication is M * Bb, and the remaining bandwidth available for M beams is Bs-M * Bb. There was a problem that the frequency could not be fully utilized (however, * means multiplication).

  The present invention has been made in view of the above, and an object of the present invention is to obtain a relay satellite capable of improving frequency utilization efficiency when performing broadcast communication.

  In order to solve the above-described problems and achieve the object, the present invention is configured so that signals received from transmitting stations existing in N (N is an integer of 2 or more) receiving beam areas are N ′ (N ′ is An integer greater than or equal to 2) A relay satellite that transmits to a receiving station existing in one transmitting beam area, receives a signal from a transmitting station in one receiving beam area, and converts the frequency of the received signal A reception signal conversion means group including N reception signal conversion means for sampling a signal subjected to processing and band limitation processing, and the reception signal conversion means are connected in a one-to-one relationship, and the sampled signal is a plurality of signals. A demultiplexing means group including N demultiplexing means, and a frequency band is assigned to each signal after demultiplexing input from the demultiplexing means group, in units of transmission beam areas as transmission destinations. Digital switch for controlling output A delay unit group including N ′ delay units for performing delay processing on a signal output in units of the transmission beam area, and a one-to-one connection with the delay unit. A multiplexing means group comprising N ′ multiplexing means for multiplexing the delayed signals output in area units is connected to the multiplexing means on a one-to-one basis, and the combined signals are analog. A transmission means group including N ′ transmission means for transmitting the signal converted into a signal and further converted into a radio frequency band to a transmission beam area of a transmission destination, and a broadcast signal received from the transmission station or When transmitting a broadcast signal generated by itself to two or more receiving stations, the digital switch matrix means assigns each broadcast signal obtained by duplicating the broadcast signal to the same frequency band, and the receiving station of the transmission destination Transmit beam area included Output to the delay means connected to the multiplexing means connected to the transmission means capable of transmitting to, each delay means that received the duplicated broadcast signal gives different time delay to the broadcast signal, It is characterized by that.

  According to the present invention, there is an effect that the frequency use efficiency can be increased when performing broadcast communication.

FIG. 1 is a diagram illustrating a configuration example of a receiving side of a relay satellite and each upstream transmitting station. FIG. 2 is a diagram illustrating a configuration example of the transmission side of the relay satellite and each downlink receiving station. FIG. 3 is a diagram illustrating the flow of each relay signal for which the relay satellite performs signal relay processing. FIG. 4 is a diagram showing the flow of each relay signal in the signal relay processing of the conventional satellite communication system. FIG. 5 is a diagram illustrating an example of demultiplexing characteristics in each demultiplexing circuit unit when the number of demultiplexing (m) is four. FIG. 6 is a diagram illustrating an example of signal demultiplexing at the reception port 2. FIG. 7 is a diagram showing a flow from switch processing to delay processing and multiplexing processing for each signal. FIG. 8 is a diagram showing the delay time provided in each delay circuit unit. FIG. 9 is a diagram illustrating a configuration example of a receiving station. FIG. 10 is a diagram illustrating a configuration example of the synthesis unit. FIG. 11 is a diagram showing the beam pattern of each antenna and the position of the receiving station. FIG. 12 is a diagram illustrating an example when a receiving station existing in the beam area performs cross-correlation. FIG. 13 is a diagram illustrating a combined signal vector output from the combining unit. FIG. 14 is a diagram showing a frame format of the broadcast signal A transmitted by the broadcast transmission station. FIG. 15 is a diagram illustrating a configuration example of a receiving station.

  Embodiments of a relay satellite according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
In the present embodiment, a relay satellite and a satellite communication system capable of distributing broadcast signals at the same frequency to a plurality of beams will be described. Here, a case where M = 3 forming one cluster with three beams will be described. However, this is an example, and M is not limited to this, and any value may be used as long as it is an integer of 2 or more. .

  FIG. 1 is a diagram illustrating a configuration example of the reception side of the relay satellite and each upstream transmission station according to the present embodiment. The relay satellite 200 receives N (N is an integer of 2 or more) receiving antenna units 210-0, 210-1, 210-2 that receive uplink signals from the beam areas 100, 102 on the receiving side. ..., 210- (N-1), N reception amplifier units 220-0, 220-1, 220-2, ..., 220- (N-1) for amplifying the received signal, and a filter N band-pass filter (BPF) units 230-0, 230-1, 230-2, ..., 230- (N-1) for removing unnecessary frequency bands, and source oscillation generation for generating source oscillation signals Unit 240, reception local signal generation unit 250 that generates a reception local signal based on the original oscillation signal, and N mixer units 260-0, 260-1, 260- that multiply the received signal and the reception local signal 2, ..., 260- (N-1) , N low-pass filter (LPF) units 270-0, 270-1, 270-2,..., 270- (N-1) that remove unnecessary frequency bands using filters, and digital signals as analog signals. N analog / digital (A / D) converters 280-0, 280-1, 280-2,..., 280- (N-1) to be converted into a plurality of signals. 290- (N-1), and a digital switch matrix unit 300 that performs a switch process on the input signal. For example, when N = 2, there are only two suffixes “0” and “1” for each component.

  In FIG. 1, a broadcast transmission station 101 that transmits a broadcast signal A is arranged in the beam area 100, and unicast transmission stations 103, 104, 105 that perform normal bidirectional communication in the beam area 102. Is arranged. In addition, the control station 110 that controls the relay satellite 200 connects to the relay satellite 200 via a separate line that does not pass through the receiving antenna units 210-0, 210-1, 210-2,..., 210- (N−1). The control station 110 transmits a command signal and controls switch processing of the digital switch matrix unit 300 of the relay satellite 200.

  FIG. 2 is a diagram illustrating a configuration example of the transmission side of the relay satellite and each downstream receiving station according to the present embodiment. The relay satellite 200 performs N ′ (N ′ is an integer of 2 or more) delay circuit units 310-0, 310-1, 310-2,..., 310- (N ′) that performs delay processing on the input signal. -1), N ′ multiplexing circuit units 320-0, 320-1, 320-2,..., 320- (N′−1) that multiplex a plurality of input signals, and analog digital signals N ′ digital / analog (D / A) converters 330-0, 330-1, 330-2,..., 330- (N′−1) for converting signals and unnecessary frequencies using filters N ′ low-pass filter (LPF) units 340-0, 340-1, 340-2,..., 340- (N′−1) for removing bands and a transmission local signal are generated based on the original oscillation signal. A transmission local signal generator 350, a signal to be transmitted and a transmission local signal N ′ mixer units 360-0, 360-1, 360-2,..., 360- (N′−1) to be calculated, and N ′ bandpasses for removing unnecessary frequency bands using a filter Filter (BPF) units 370-0, 370-1, 370-2, ..., 370- (N'-1), and N 'transmission amplifier units 380-0, 380-1, amplifying signals to be transmitted, 380-2,..., 380- (N′−1), and N ′ transmit antenna units 390-0 that perform transmission to the beam areas 400, 402, 404 on the transmitting side, the N′-th beam area, and the like. 390-1, 390-2, ..., 390- (N'-1). For example, when N ′ = 2, the end of the code of each component is only two, “0” and “1”.

  In FIG. 2, a receiving station 401 is arranged in the beam area 400, a receiving station 403 is arranged in the beam area 402, and a receiving station 405 is arranged in the beam area 404.

  Next, signal relay processing in the relay satellite 200 will be described. FIG. 3 is a diagram illustrating the flow of each relay signal for which the relay satellite performs signal relay processing. Specifically, a case will be described in which the relay satellite 200 realizes the simultaneous relay of signals shown below with the frequency arrangement shown in FIG.

  (1) The relay satellite 200 replicates the broadcast signal A from the broadcast transmission station 101 in the beam area 100 into three, the reception station 401 in the beam area 400, the reception station 403 in the beam area 402, the beam Transmission is performed after giving different delays to the receiving station 405 in the area 404. The broadcast signals A subjected to the delay processing are referred to as broadcast signals A0, A1, and A2, respectively.

  (2) The relay satellite 200 transmits the signal B from the unicast transmitting station 103 in the beam area 102 to the receiving station 403 in the beam area 402.

  (3) The relay satellite 200 transmits the signal C from the unicast transmission station 104 in the beam area 102 to the reception station 405 in the beam area 404.

  (4) The relay satellite 200 transmits the signal D from the unicast transmitting station 105 in the beam area 102 to the receiving station 401 in the beam area 400.

  In addition, although the case where the receiving stations 401, 403, and 405 simultaneously receive the broadcast signal A and one of the signals D, B, and C will be described, the present invention is not limited to this. For example, the receiving station that receives the broadcast signal A and the receiving station that receives the signals B, C, and D do not need to be the same station, and may exist separately in each beam area.

  Further, a case will be described in which unicast transmission stations 103, 104, and 105 are all present in one beam area 102, but the present invention is not limited to this. For example, the unicast transmission stations 103, 104, and 105 may exist in different beam areas.

Also, as shown in FIG. 3, here, each signal band is expressed based on the system band Bs allocated to the satellite communication system. That is, when the system band Bs is 1.0, the band Bb of the broadcast signal A is represented as 0.25, and the bandwidths of the signals B, C, and D are represented as 0.25. As is apparent from FIG. 3, this embodiment is characterized in that the relay satellite 200 arranges the broadcast signals A0, A1, A2 subjected to delay processing on the same frequency (f ₀ ).

Here, the frequency arrangement of each signal when signal relay processing is performed in a conventional satellite communication system will be briefly described. FIG. 4 is a diagram showing the flow of each relay signal in the signal relay processing of the conventional satellite communication system. In a conventional satellite communication system, the broadcast signal A is arranged at a frequency different from f ₀ , f ₁ , and f _{2 in} order to avoid interference due to the same frequency. In this case, a bandwidth of 0.75 (= 0.25 * 3) is consumed for broadcast communication with respect to the system bandwidth of 1.0. For this reason, the remaining bandwidth 0.25 (= 1.0-0.75) must be used for communications other than broadcast communications. For example, as shown in FIG. 4, in the conventional satellite communication system, only the relay of the signal B from the unicast transmitting station 103 to the receiving station 403 can be realized using the surplus bandwidth 0.25.

On the other hand, in this embodiment, as shown in FIG. 3, the relay satellite 200 arranges the broadcast signals A0, A1, and A2 on the same frequency (f ₀ ). Only 0.25 bandwidth is consumed, and the remaining bandwidth 0.75 (= 1.0-0.25) can be used for other communications other than broadcast communication. For example, as shown in FIG. 3, the relay satellite 200 receives not only the signal B from the unicast transmission station 103 to the reception station 403 but also the reception from the unicast transmission station 104 using the remaining bandwidth 0.75. The relay of the signal C to the station 405 and the relay of the signal D from the unicast transmitting station 105 to the receiving station 401 can be realized. As a result, the frequency can be used effectively and an increase in system capacity can be realized.

  Specifically, assuming that the total bandwidth that can be used by M beams is Bs and the broadcast signal bandwidth is Bb, the bandwidth required in the conventional satellite communication system is M * Bb. On the other hand, since the bandwidth required in the present embodiment is reduced from M * Bb to Bb, the frequency utilization efficiency of broadcast communication is improved M times. As a result, the remaining bandwidth that can be used by the M beams increases from “Bs−M * Bb” to “Bs−Bb”. As a result, the system capacity is increased to “(Bs−Bb) / (Bs−M * Bb”. ) "Can be doubled.

  Regarding the operation of signal relay processing in the relay satellite 200, first, the operation on the receiving side of the relay satellite 200 will be described with reference to FIG. In the relay satellite 200, the broadcast signal A transmitted from the broadcast transmission station 101 from the beam area 100 is received by the reception antenna unit 210-0 and amplified by the reception amplifier unit 220-0.

  In the relay satellite 200, the broadcast signal A is amplified by the reception amplifier unit 220-0, subjected to band processing by the BPF unit 230-0 at the reception Port 0, and output to the mixer unit 260-0. Here, the reception local signal generation unit 250 generates a reception local signal for realizing a frequency conversion process, which will be described later, based on the original vibration signal from the original vibration generation unit 240, and the mixer units 260-0 and 260-. 1, 260-2, ..., 260- (N-1).

  The mixer section 260-0 multiplies the input broadcast signal A and the received local signal, and outputs the multiplied signal to the LPF section 270-0. In the relay satellite 200, the broadcast signal A is frequency-converted from a radio frequency band to an intermediate frequency (IF) band or a baseband band by band-processing the signal after multiplication by the LPF unit 270-0, and at the same time A band-limited signal can be obtained with the system band Bs = 1.0.

  Next, in the relay satellite 200, the broadcast signal A after frequency conversion is sampled by the A / D conversion unit 280-0 and output to the branching circuit unit 290-0. Here, when the input signal is an intermediate frequency (IF) signal, the A / D converter 280-0 samples the IF signal. In addition, when the input signal is a baseband signal, the A / D conversion unit 280-0 samples the baseband signal with two types of in-phase (I) and quadrature (Q).

  The configuration from the reception antenna unit 210-0 to the A / D conversion unit 280-0 described above is collectively expressed as reception signal conversion means for convenience. That is, it is assumed that the relay satellite 200 includes N received signal conversion means. However, the number of the original vibration generation unit 240 and the reception local signal generation unit 250 is one.

  The demultiplexing circuit unit 290-0 samples the signal including the out-of-band signal in the A / D conversion unit 280-0. Extract. The demultiplexing circuit unit 290-0 outputs the broadcast signal A after the demultiplexing process to the digital switch matrix unit 300.

  For convenience of explanation, the number of demultiplexing (m) is four, but is not limited to this. The number of demultiplexing may be any value as long as it is an integer of 2 or more. However, when there are a plurality of transmitting stations in the beam area (for example, the beam area 102) on the receiving side, it is desirable to be able to demultiplex more than the number of transmitting stations existing in the beam area. FIG. 5 is a diagram illustrating an example of demultiplexing characteristics in each demultiplexing circuit unit when the number of demultiplexing (m) is four. The horizontal axis represents frequency and the vertical axis represents amplitude. Demultiplexing circuit units 290-0, 290-1, 290-2,..., 290- (N-1) represent signal spectra input to the demultiplexing circuit units (1) to (4) in the figure. Is demultiplexed with the four frequency characteristics shown in FIG.

  Further, the frequency characteristics of each branching circuit unit are not limited to the characteristics shown in FIG. As long as the signal spectrum input to each demultiplexing circuit unit can be demultiplexed into four, it may be demultiplexed with characteristics other than those shown in FIG. However, by demultiplexing with the characteristics shown in FIG. 5, the original demultiplexed signal can be restored.

  Specifically, as shown in FIG. 5, the characteristics of the filters used in each demultiplexing circuit unit are designed such that the characteristics overlap between adjacent filters, and the amplitude at which the characteristics of each filter intersect is zero. .5, and the filter design is such that the sum of the frequency vs. amplitude characteristics of each filter in the overlap region is 1. Furthermore, if the frequency vs. phase characteristic of each filter shown in FIG. 5 is not discontinuous and is designed to be a straight line, for example, even if the wideband signal is once decomposed into four, the subsequent multiplexing circuit unit 320-0 , 320-1, 320-2,..., 320- (N′−1) can restore the original wideband signal. Due to such properties, the relay satellite 200 does not necessarily have a signal bandwidth that can be relayed less than 0.25, and can implement signal relay of various bandwidths within a bandwidth up to 1.0. is there.

  Although the case where the broadcast signal A is received from the broadcast transmission station 101 has been described, the relay satellite 200 performs the same process as described above even when a signal from another unicast transmission station is received. In the relay satellite 200, the reception antenna unit 210-2 receives the signal B from the unicast transmission station 103 from the beam area 102, the signal C from the unicast transmission station 104, and the signal D from the unicast transmission station 105. Then, the signal is amplified by the reception amplifier unit 220-2. Although not shown, the relay satellite 200 receives a plurality of signals from other beam areas in the same manner in the other receiving antenna units 210-1, 210- (N-1) and the like, and amplifies them in the receiving amplifier unit in the subsequent stage. To do.

  In relay satellite 200, reception amplifier section 220-2 amplifies signal {B, C, D}, performs band processing in BPF section 230-2 at reception Port 2, and outputs the result to mixer section 260-2. Mixer section 260-2 multiplies input signal {B, C, D} and the received local signal, and outputs the multiplied signal to LPF section 270-2. In the relay satellite 200, the signal {B, C, D} is frequency-converted from the radio frequency band to the intermediate frequency band or the baseband band by performing band processing on the signal after multiplication by the LPF unit 270-2, At the same time, a band-limited signal can be obtained with the system band Bs = 1.0. FIG. 6 is a diagram illustrating an example of signal demultiplexing at the reception port 2. It shows a flow until a signal received from each unicast transmitting station by the receiving antenna unit 210-2 is demultiplexed by the demultiplexing circuit unit 290-2. As shown in FIGS. 6A and 6B, in the analog filter by the BPF unit 230-2 and the LPF unit 270-2, the signal {B, C, D} is extracted, and there is an unnecessary wave in the adjacent frequency band. If so, remove unwanted waves.

  Next, in relay satellite 200, signal {B, C, D} after frequency conversion is sampled by A / D conversion section 280-2 and output to branching circuit section 290-2. The demultiplexing circuit unit 290-2 uses the four filters indicated by the dotted lines in FIG. 6C for the signal {B, C, D} shown in FIG. 6B sampled by the A / D conversion unit 280-2. Depending on the characteristics, the signal is decomposed into four signals shown in FIG. In this way, the demultiplexing circuit unit 290-2 decomposes (demultiplexes) the signal {B, C, D} shown in FIG. 6C into three signals B, C, and D.

  Next, switch processing in the digital switch matrix unit 300 will be described. FIG. 7 is a diagram showing a flow from switch processing to delay processing and multiplexing processing for each signal. The digital switch matrix unit 300 receives the broadcast signal A output from the demultiplexing circuit unit 290-0 and the signals B, C, and D output from the demultiplexing circuit unit 290-2 as shown in FIG. The switch processing shown is performed.

  Specifically, the digital switch matrix unit 300 replicates the broadcast signal A into three for transmission to the beam areas 400, 402, and 404, and transmits the transmission ports {0, 1, 2} shown in FIG. Are connected to frequency 0. Further, the digital switch matrix unit 300 sets the signal B output from the demultiplexing circuit unit 290-2 to the frequency No. 3 of the transmission Port1 shown in FIG. 7A and the signal C to the transmission Port2 shown in FIG. The signal D is connected to the frequency No. 2 of the transmission port 0 shown in FIG.

  Next, the operation on the transmission side of the relay satellite 200 will be described with reference to FIG. Each of the delay circuit units 310-0, 310-1, 310-2,..., 310- (N′−1) gives a time delay to m (here, m = 4) input signals. Each time delay amount is arbitrarily set by a command signal from the ground control station 110 shown in FIG. In addition, the flexibility of signal processing in the relay satellite 200 can be increased by adopting a configuration in which the setting can be changed during operation.

  The delay circuit units 310-0, 310-1, 310-2,..., 310- (N′−1) mainly act on the replicated broadcast signal A, and the replicated broadcast signal A On the other hand, different time delays are given. Here, the delay circuit units 310-0, 310-1, and 310-2 give three different time delays to the broadcast signal A replicated in three. FIG. 8 is a diagram showing the delay time provided in each delay circuit unit. The delay circuit unit 310-0 gives a time delay τ (0, 0) to the broadcast signal A, and outputs the signal after giving this delay as the broadcast signal A0. The delay circuit unit 310-1 Then, a time delay τ (0, 1) is given to the broadcast signal A, and the signal after this delay is given is output as the broadcast signal A1, and the delay circuit unit 310-2 The time delay τ (0, 2) is given, and the signal after giving this delay is outputted as the broadcast signal A2. As shown in FIG. 8, the delay times τ (0,0), τ (0,1), and τ (0,2) are different values.

  Although only one broadcast signal (broadcast signal A) is shown here, the present invention is not limited to this. When a plurality of broadcast signals are relayed, different delays are similarly given to the respective broadcast signals in each delay circuit unit. As a result, the relay satellite 200 can handle a plurality of broadcast signals.

  In addition, since signals other than the broadcast signal such as signals B, C, and D are used in different frequency bands, it is not necessary to delay them by each delay circuit unit, and the delay time may be set to zero. FIGS. 7B, 7C, and 7D show processing relating to each delay circuit unit. Since the signals B, C, and D do not need to be delayed, the time delay is indicated by a dotted line. However, like the broadcast signal A, each signal may be delayed.

  Next, the operation of the multiplexing circuit units 320-0, 320-1, 320-2, ..., 320- (N'-1) will be described. The multiplexing circuit units 320-0, 320-1, 320-2,..., 320- (N′−1) each synthesize four input signals by arranging them at a frequency interval of 0.25. In addition, each multiplexing circuit unit has a circuit design in which the frequency-to-phase characteristic of the combined signal is a straight line, similar to the above-described demultiplexing circuit unit. Here, the combining circuit unit 320-0 combines the signal A0 and the signal D with the frequency arrangement shown in FIG. 7E, and the combining circuit unit 320-1 displays the signal A1 and the signal B in FIG. The signals are combined in the frequency arrangement shown in f), and the multiplexing circuit unit 320-2 combines the signal A2 and the signal C in the frequency arrangement shown in FIG.

  As for these multiplexing processing or demultiplexing processing, for example, “" Examination of demultiplexing / multiplexing method for flexible satellite repeater ”, IEICE General Conference 2011 B-3-3, March 2011 "" Study of demultiplexing / combining system suitable for regenerative / non-regenerative repeater for satellite installation ", IEICE 2011 General Conference B-3-10, September 2011. Further, it can be realized by a tree-type filter bank system based on half-division / two-way multiplexing.

  Next, in the relay satellite 200, a signal obtained by combining the broadcast signal A0 and the signal D in the combining circuit unit 320-0 in the D / A conversion unit 330-0 is converted from a digital signal to an analog signal, and the LPF unit 340 is converted. -0 outputs to the mixer unit 360-0 after band processing. Here, the transmission local signal generation unit 350 generates a transmission local signal for realizing a frequency conversion process to be described later based on the original vibration signal from the original vibration generation unit 240, and the mixer units 360-0 and 360-. 1, 360-2,..., 360-(N′−1).

  The mixer unit 360-0 multiplies the signal obtained by combining the broadcast signal A0 and the signal D and the transmission local signal, and outputs the multiplied signal to the BPF unit 370-0. In the relay satellite 200, the signal after multiplication by the BPF unit 370-0 is band-processed to convert the signal into a radio frequency band signal, and the signal converted into the radio frequency band is transmitted via the transmission amplifier unit 380-0. Transmission from 390-0 toward the beam area 400 is performed.

  Similarly, in the relay satellite 200, a signal obtained by combining the broadcast signal A1 and the signal B by the combining circuit unit 320-1 is converted into a D / A conversion unit 330-1, an LPF unit 340-1, and a mixer unit 360-1. Then, after conversion to the radio frequency band via the BPF unit 370-1, the transmission is performed from the transmission antenna unit 390-1 toward the beam area 402 via the transmission amplifier unit 380-1.

  In the relay satellite 200, a signal obtained by combining the broadcast signal A2 and the signal C by the combining circuit unit 320-2 is converted into a D / A conversion unit 330-2, an LPF unit 340-2, a mixer unit 360-2, After conversion to the radio frequency band via the BPF unit 370-2, transmission is performed from the transmission antenna unit 390-2 toward the beam area 404 via the transmission amplifier unit 380-2.

  Note that the configurations from the D / A conversion unit 330-0 to the transmission antenna unit 390-0 described above are collectively expressed as transmission means for convenience. That is, it is assumed that the relay satellite 200 includes N ′ number of transmission units. However, one transmission local signal generation unit 350 is sufficient.

  Further, for convenience of explanation, the number of multiplexing is four, but the number of multiplexing is not limited to this. Any value may be used as long as it is an integer of 2 or more.

As described above, when relaying the broadcast signal A to the three beam areas, the relay satellite 200 transmits the same frequency (f ₀ ) shown in FIG. 3 after giving different time delays. Thereby, the use efficiency of the frequency can be enhanced as compared with the conventional case.

  When the three beam areas 400, 402, and 404 are adjacent to each other, generally, the broadcast signal A for the adjacent beam area becomes an interference source with respect to the broadcast signal A for the own beam area. Communication quality will be degraded. However, by giving the above-mentioned time delay in the relay satellite 200, the receiving station conversely combines the broadcast signal A for the adjacent beam area with the broadcast signal A for the own beam area, thereby improving the communication quality. , And the transmission power reduction effect of the satellite can be realized.

  Next, the configuration of the receiving station that receives a signal from the relay satellite 200 will be described. FIG. 9 is a diagram illustrating a configuration example of a receiving station. Here, the case where the broadcast signal A is a spread spectrum signal will be described as an example. Although the receiving station 403 will be described, the receiving stations 401 and 405 have the same configuration as the receiving station 403.

  The receiving station 403 includes a receiving antenna unit 500 that receives a signal from the relay satellite 200, a receiving amplifier unit 501 that amplifies the received signal, and a bandpass filter (BPF) that removes unnecessary frequency bands using a filter. Unit 502, reception local signal generation unit 503 for generating a reception local signal, mixer unit 504, low-pass filter (LPF) unit 505 for removing unnecessary frequency bands using a filter, and converting an analog signal into a digital signal An analog / digital (A / D) conversion unit 506 for converting, a demultiplexing circuit unit 507 for demultiplexing an input signal into a plurality of signals, and unicast demodulation units 508 and 509 for demodulating a unicast signal, A broadcast signal demodulator 510 that demodulates the broadcast signal. The broadcast signal demodulator 510 also includes a cross-correlator 511 that obtains a cross-correlation data sequence, and a vector phase detection that detects the number of cross-correlation vectors, the arrival time of each vector, and each vector phase angle from the cross-correlation data sequence. 512, a synthesis unit 513 that vector-synthesizes each correlation vector of the cross-correlation data sequence using each information of the number of vectors, vector arrival time, and vector phase angle, and data demodulation by performing synchronous detection or delay detection And a detector 514 for performing the operation.

  FIG. 10 is a diagram illustrating a configuration example of the synthesis unit. The synthesizing unit 513 includes delay units 600 and 601 that delay the cross-correlation data by a designated delay time, phase shift units 610 and 611 that shift the cross-correlation data after the delay process, cross-correlation data and the shift An addition unit 620 that adds the signals after the phase and a latch unit 630 that extracts a correlation peak value after vector synthesis from the cross-correlation data series after the addition.

  Specifically, the operation of the reception process using the reception station 403 will be described. The receiving station 403 existing in the beam area 402 receives the signal {A1, B} obtained by combining the broadcast signal A1 and the signal B by the receiving antenna unit 500, and amplifies the signal by the receiving amplifier unit 501. In the receiving station 403, the amplified signal {A1, B} is subjected to band processing by the BPF unit 502, the signal after band processing is multiplied by the received local signal in the mixer unit 504, and further band processing is performed in the LPF unit 505. Thus, the frequency of the signal {A1, B} is converted from the radio frequency band to the intermediate frequency or baseband. Then, the A / D conversion unit 506 samples the signal {A1, B} after the frequency conversion, and the demultiplexing circuit unit 507 separates the broadcast signal A1 and the signal B from the signal {A1, B}. To wave.

  If a signal for an adjacent beam area that is an interference source is also received, the reception station 403 performs the above-described reception processing on the signal for the adjacent beam area together with the signal {A1, B}. .

  The unicast demodulation unit 508 demodulates the signal B demultiplexed by the demultiplexing circuit unit 507. As apparent from FIG. 3, the signal B is not subject to the same frequency interference from the signal for the adjacent beam area, so that data demodulation can be realized by a general demodulation method. On the other hand, the broadcast signal demodulation unit 510 performs demodulation using not only the signal A1 for the own beam area but also the signals A0 and A2 of the same frequency for the adjacent beam areas.

  Specifically, the demodulation processing in the broadcast signal demodulation unit 510 will be described in detail. First, as a premise, the control station 110 notifies each receiving station 401, 403, 405 of the delay amount information set in the delay circuit units 310-0 to 310- (N′−1) of the relay satellite 200. It shall be. Similarly, the control station 110 notifies the receiving stations 401, 403, and 405 of the number of broadcast signals that can arrive from adjacent beam areas in each beam area.

  In broadcast signal demodulator 510, cross-correlator 511 starts despreading processing. The cross-correlation unit 511 performs cross-correlation processing using the same sequence as the spread sequence of the broadcast signal A at a sampling speed several times the chip rate for spreading (performs sliding correlation).

  FIG. 11 is a diagram illustrating the beam pattern of each antenna and the position of the receiving station 403. The beam pattern 701 is a beam pattern for the beam area 402 transmitted from the transmission antenna unit 390-1, and the beam pattern 702 is a beam pattern for the beam area 400 transmitted from the transmission antenna unit 390-0. The beam pattern 703 is a beam pattern for the beam area 404 transmitted from the transmission antenna unit 390-2. Further, for example, regarding the beam area for the beam area 402, the magnitude of the antenna gain by other beam patterns at each point when the antenna gain by the beam pattern 701 is Y [dBi] is shown.

  FIG. 12 is a diagram illustrating an example when the receiving station 403 existing in the beam area 402 performs cross-correlation. 12A shows the cross-correlation vector characteristic, and FIG. 12B shows the cross-correlation power characteristic. When the receiving station 403 performs cross-correlation processing using the same sequence as the spread sequence of the broadcast signal A, a cross-correlation vector C1 that is a correlation value with the broadcast signal A1 addressed to the own beam area is obtained (FIG. 12). (A)). At the same time, a cross-correlation vector C0 that is a correlation value with the broadcast signal A0 transmitted to the beam area 400 and a cross-correlation vector C2 that is a correlation value with the broadcast signal A2 transmitted to the beam area 404 are also shown in FIG. As shown in a) and (b), although the correlation power is smaller than that of the vector C1, it is obtained by being temporally separated. This time separation is obtained by the delay difference (τ (0,0), τ (0,1), τ (0,2)) given by the relay satellite 200, and each time difference of the three correlation vectors is , “Τ (0,1) −τ (0,0)” between the vector C1 and the vector C0, and “τ (0,2) −τ (0,1)” between the vector C1 and the vector C2. "

  The vector phase detector 512 determines the number of cross-correlation vectors shown in FIG. 12A, the arrival time of each vector, and each vector from the cross-correlation data series (FIG. 12A) obtained by the cross-correlator 511. The phase angle is detected and notified to the synthesis unit 513.

  Note that the vector phase detector 512 may use information from the control station 110 when detecting the arrival time of the vector and the vector phase angle. Specifically, each information of each delay amount set in the delay circuit units 310-0 to 310-2 of the relay satellite 200 and the number of broadcast signals that can arrive from the adjacent beam area (here, three). By using these pieces of information, the number of vectors, the arrival time of the vectors, and the vector phase angle can be detected more accurately than in the case of detecting without using these pieces of information.

  The synthesizing unit 513 uses each information of the number of vectors detected by the vector phase detecting unit 512, the arrival time of the vector, and the vector phase angle, and each cross correlation vector of the cross correlation data series output from the cross correlation unit 511. Are combined and output.

  An operation example of the combining unit 513 will be described with reference to FIG. The cross correlation data series is input to the delay units 600 and 601. The delay unit 600 performs time delay control to match the first path vector that arrives first with the arrival time of the third path. Specifically, based on the time difference information of the vector detected by the vector phase detection unit 512, the vector phase detection unit 512 performs the delay amount “τ (0,2) −τ (0,0) of the first path. To the delay unit 600. Similarly, the delay unit 601 performs time delay control for matching the second path vector to the arrival time of the third path. Specifically, based on the time difference information of the vector detected by the vector phase detection unit 512, the vector phase detection unit 512 determines the delay amount “τ (0,2) −τ (0,1) of the second path. Is provided to the delay unit 601.

  In this way, by the delay control processing of the cross-correlation data series branched into three, the positions of the three correlation vectors can be all aligned with the vector positions of the third path. However, since the correlation vector phase angles are not aligned, the vector phase angles are further aligned by the following processing.

  The phase shift unit 610 matches the vector phase angle of the first path that arrives first with the vector phase angle of the third path. Specifically, based on the vector phase angle information detected by the vector phase detection unit 512, the vector phase detection unit 512 gives the phase shift amount of the first path to the phase shift unit 610. Similarly, the phase shifter 611 matches the vector phase angle of the second path with the vector phase angle of the third path. Specifically, the vector phase detection unit 512 gives the phase shift amount of the second path to the phase shift unit 611.

  By performing such vector phase shift control, the vector phase angles of the three-correlated cross-correlation data series can all be aligned with the vector position of the third path.

  Adder 620 adds the three cross-correlation data sequences subjected to the above-described time delay control and phase shift control, and latch 630 adds based on the arrival time of the vector detected by vector phase detector 512. A correlation peak value after vector synthesis is extracted from the subsequent cross-correlation data series.

  Here, the broadcast signal demodulation processing of the receiving station 403 existing in the beam area 402 has been described. However, the broadcast signal demodulation processing of the receiving station 401 existing in the beam area 400 and the receiving station 405 existing in the beam area 404 are described. The broadcast signal demodulation process can be realized in the same manner. In this case, at the receiving station 401 existing in the beam area 400, the correlation vector C0 for the own beam area is the highest, and at the receiving station 405 existing in the beam area 404, the correlation vector C2 for the own beam area is the highest correlation power. Will be shown.

  FIG. 13 is a diagram illustrating a combined signal vector output from the combining unit. As a result of the above processing, the combined signal vectors output from the combining unit 513 are aligned as shown in FIG. 13, so that a signal without a decrease in signal level can be obtained.

  The downstream detection unit 514 receives the combined signal vector output from the combining unit 513 in the spreading code period (L [μsec]) as input, performs synchronous detection or delay detection, and demodulates the data.

  Thus, by the delay control for each broadcast signal of the relay satellite 200 and each signal processing of the receiving station 403, in the satellite communication system, not only the broadcast signal addressed to the own beam area but also the same in each receiving station. In order to demodulate the broadcast signal after synthesizing the broadcast signal arriving from the adjacent beam area by frequency, it realizes good communication quality for broadcast communication with effective use of frequency (Fig. 4 → Fig. 3) be able to. Further, by synthesizing broadcast signals arriving from adjacent beam areas at the same frequency, the power of the broadcast signals A0, A1, A2 transmitted from the relay satellite 200 is reduced to the minimum necessary as compared with the case of not synthesizing. Can be reduced to the communication quality level. Thereby, low power consumption of the relay satellite 200 can also be realized. In addition, if each broadcast signal arriving from adjacent beam areas at the same frequency is separated and the quality of the broadcast communication is sufficiently secured without combining signals from adjacent beam areas, each receiving station It is also possible to omit the synthesis process.

  Each receiving station can also estimate the position of its own station using the correlation power information. For example, when the receiving station 403 receives the broadcast signal {A0, A1, A2} at the position (1) under the condition of the antenna pattern shown in FIG. 11, as shown in FIG. The correlation power P1 obtained from the broadcast signal A1 for the area is b [dB] higher than the correlation powers P0 and P2 received from the adjacent beam areas, and the correlation powers P0 and P2 are both b [dB] lower levels. It becomes. Next, when the receiving station 403 moves from the position (1) in FIG. 11 to the position (2), the correlation power P1 obtained from the broadcast signal A1 for the own beam area and the broadcast for the adjacent beam area 404 are transmitted. While the correlation power P2 obtained from the signal A2 decreases, the correlation power P0 obtained from the broadcast signal A0 for the adjacent beam area 400 increases (FIG. 12 (c)). Further, when the receiving station 403 moves to the position of (3) in FIG. 11 which is the boundary between the beam area 400 and the beam area 402, the correlation power P1 and the correlation power P2 further decrease, while the correlation power P0 increases ( FIG. 12 (d)). In this case, as shown in FIG. 12 (d), the correlation powers P0 and P1 are at a level lower by a [dB], and the correlation power P2 is at a level lower by c [dB]. Thus, even if the receiving station moves to any position, any one of the correlation powers P0, P1, and P2 is maintained, so that it is clear that stable broadcast communication can be realized. Furthermore, the position of the receiving station can be estimated using each piece of correlation power information.

  In the present embodiment, when each correlation power shown in FIG. 12B is obtained, the own station is in the center of the beam area 402, and when each correlation power shown in FIG. Can be said to be located at the boundary between the beam area 402 and the beam area 404. Thus, the position of the own station can be estimated from the correlation power information of each correlation power P0, P1, and P2. Not only the correlation power but also the timing information of each correlation value may be used together.

  The generation timing of the correlation powers P0, P1, and P2 is dominated by each time delay given by the satellite, but strictly speaking, varies slightly depending on the position of the receiving station. The position of the own station may be estimated by using not only the correlation power but also the fluctuation information.

  By the way, in the present embodiment, although it is expressed one-dimensionally, in reality, the position of the own station is broadcast using broadcast signals from adjacent beam areas allocated two-dimensionally in the east, west, north, and south directions. It can be detected by the signal demodulator 510. Thereby, unlike the conventional GPS system using a plurality of satellites, the position estimation can be realized using one relay satellite 200, so that the cost of the system can be suppressed.

  As an application example, the receiving station estimates the position of its own station using signals from three satellites in the GPS system. However, the receiving station uses a combination of two GPS satellites and this satellite (relay satellite 200). May be estimated. When two GPS satellites are used, the uncertainty of the position of the own station occurs on the circumference, but the range of uncertainty can be narrowed by adding the above-described position estimation information.

  As described above, in the present embodiment, when one broadcast signal is transmitted to a plurality of receiving stations, the broadcast signal is duplicated in the relay satellite, and each duplicated broadcast signal is sent to the same frequency band. It was decided that each broadcast signal assigned and copied was given a different delay time for transmission. Thereby, since the band used for communication of the broadcast signal can be reduced as compared with the conventional one, the frequency can be used effectively and the frequency use efficiency can be increased.

  In addition, in a satellite communication system including a relay satellite and a receiving station, in particular, in a multi-beam satellite communication system in which each beam area is arranged adjacently, by using a broadcast signal for adjacent beam areas, It is possible to improve the quality and stability of broadcast communications and reduce the power consumption of relay satellites. Furthermore, the position estimation of each receiving station can be realized.

  In this embodiment, three time delays are given to the broadcast signal with respect to the three beams. However, in the case of N beams, a maximum N time delays are given. When a broadcast signal for another beam area that is not adjacent to the own beam area and does not give the same frequency interference to the own beam area, the broadcast signal for the own beam area and the broadcast signal for the other beam area Different time delays may not be given (the same time delay setting may be used). Therefore, when the number of beams for transmitting broadcast signals from the satellite is N, N time delays are not necessarily given.

  Also, depending on the beam area, it may not be necessary to transmit a broadcast signal. Therefore, it is not always necessary to transmit the broadcast signal A by copying and delaying all the beams. By controlling connection to the matrix unit 300, the broadcast signal A is duplicated and transmitted only to the necessary beam area.

  In this embodiment, the delay circuit units 310-0, 310-1, 310-2,..., 310- (N′−1) are replaced with the digital switch matrix unit 300 and the multiplexing circuit units 320-0, 320. −1, 320-2,..., 320- (N′−1), and a configuration in which independent delays are given to m input signals has been described. It is not limited. For example, the delay circuit units 310-0, 310-1, 310-2,..., 310- (N′−1) are combined with the multiplexing circuit units 320-0, 320-1, 320-2,. You may install after N'-1) instead of before. In this case, the signal to be delayed is one signal after multiplexing, and an independent delay cannot be given to m signals. Therefore, other unicast signals also have the disadvantage that the same delay as the broadcast signal is given, but the circuit scale of the delay circuit unit can be reduced to 1 / m times. In the present embodiment, the broadcast signal is transmitted from the broadcast transmission station 101 in the beam area 100 to the plurality of beam areas via the relay satellite 200. However, the broadcast signal is transmitted to the relay satellite. It may be generated inside 200. The broadcast signal in this case is, for example, a signal obtained by modulating information (terrain image data or the like) observed by the relay satellite 200 itself. The broadcast signal generated inside the relay satellite 200 is directly input to the digital switch matrix unit 300 and thereafter transmitted to each beam area together with other multicast signals as described above.

Embodiment 2. FIG.
In the first embodiment, the signal processing when the broadcast signal A is a spread spectrum signal has been described. In the present embodiment, the case where the broadcast signal A is a PSK modulated signal that does not perform spread spectrum will be described. A different part from Embodiment 1 is demonstrated.

  FIG. 14 is a diagram showing a frame format of the broadcast signal A transmitted by the broadcast transmission station 101. As shown in FIG. 14, the broadcast transmission station 101 transmits a PSK modulated signal with a transmission path equalizing preamble added thereto, and the relay satellite 200 performs the same processing as in the first embodiment, Relay signal A.

  Next, the configuration of the receiving station will be described. FIG. 15 is a diagram illustrating a configuration example of the receiving station 401 in the present embodiment. Here, as an example, a case where the broadcast signal A is a PSK modulated signal will be described. Although the receiving station 401 will be described, the receiving stations 403 and 405 have the same configuration as the receiving station 401.

  The reception station 401 includes a reception antenna unit 500, a reception amplifier unit 501, a BPF unit 502, a reception local signal generation unit 503, a mixer unit 504, an LPF unit 505, an A / D conversion unit 506, a demultiplexing unit, A circuit unit 507; unicast communication demodulation units 508 and 509; and a broadcast signal demodulation unit 520 that demodulates the broadcast signal. Also, the broadcast signal demodulator 520 includes a cross-correlator 521 that obtains a cross-correlation data sequence, a transmission path estimator 522 that detects a transmission path estimation value, and a received signal equalization process using the transmission path estimation value. And an equalizer 523 that performs demodulation on the equalized broadcast signal A.

  The difference from the receiving station 401 in the first embodiment is only the broadcast signal demodulator 520. The operation of the broadcast signal demodulator 520 will be described with reference to FIG.

  The cross-correlation unit 521 performs a cross-correlation process between the received signal and the known preamble using the same preamble added to the PSK modulation signal to obtain a cross-correlation data sequence.

  Next, the transmission path estimation unit 522 extracts the cross-correlation characteristic between the preamble and the known preamble included in the received signal from the cross-correlation data series by detecting the cross-correlation power, and uses the extracted cross-correlation characteristic as the transmission path. Save as an estimate. At this time, since the transmission path estimation unit 522 can obtain the correlation vector of each broadcast signal as shown in FIG. 12 at the time of receiving the preamble, as in the first embodiment, using the cross-correlation information of the preamble, As in Embodiment 1, it is possible to realize position estimation of the own station.

  The equalization unit 523 performs equalization processing on the received signal using the transmission path estimation value. For example, after the received signal is converted from the time domain to the frequency domain, the received signal converted to the frequency domain is divided by the transmission path estimation value converted to the frequency domain, thereby realizing equalization processing in the frequency domain. . By this equalization processing, the original broadcast signal A can be restored from the broadcast signals A0, A1, A2 received at the same frequency. The data series after division is again converted from the frequency domain to the time domain in the equalization unit 523 and then output to the detection unit 524.

  Since the phase discontinuity in the broadcast signal A band is eliminated by the equalization unit 523, the detection unit 524 can realize demodulation of the equalized broadcast signal A by general demodulation processing. .

  As described above, even in the case where the broadcast signal is a PSK modulated signal that does not perform spread spectrum, similarly to the first embodiment, by using the broadcast signal for the adjacent beam area, the high quality of the broadcast communication is achieved. And high stability can be realized. In the present embodiment, the relay of the PSK modulation signal has been described, but the signal to be relayed may be OFDM (Orthogonal Frequency Division Multiplexing). Also in the case of OFDM, the frame format is a combination of the preamble and data shown in FIG. 14, and the receiving station can be realized with the same configuration as in FIG. Demodulation is performed in the detection unit 524 by FFT processing unique to OFDM.

Embodiment 3 FIG.
In the first and second embodiments, in a multi-beam satellite communication system using a relay satellite, particularly when each beam area is arranged adjacent to each other, effective use of frequency, high quality of broadcast communication, high stability Furthermore, the method for realizing the position estimation of each ground receiving station has been described. However, it is also possible to provide a relay device installed on the ground with the same configuration as the relay satellite. Moreover, it is also possible to apply to a terrestrial radio system using this relay apparatus.

  In this case, in the relay apparatus implemented with the same configuration as that of the first embodiment, the broadcast signal from the transmission station is converted into another frequency, and then a delay difference is given, and the directional antenna is directed in a plurality of directions. Transmit on the same frequency.

  As a result, even in a terrestrial radio system using a relay apparatus having the same configuration as that of the relay satellite, it is possible to realize effective use of frequency, high quality and high stability of broadcast communication.

  As described above, the relay satellite according to the present invention is useful for relaying signals, and is particularly suitable for relaying signals from a plurality of transmitting stations to a plurality of receiving stations.

100, 102 Beam area 101 Broadcast transmission station 103, 104, 105 Unicast transmission station 110 Control station 200 Relay satellite 210-0, 210-1, 210-2, ..., 210- (N-1) Receiving antenna section 220 , 220-1, 220-2,..., 220- (N-1) reception amplifier unit 230-0, 230-1, 230-2,..., 230- (N-1) BPF unit 240 Source oscillation generation Unit 250 reception local signal generation unit 260-0, 260-1, 260-2, ..., 260- (N-1) mixer unit 270-0, 270-1, 270-2, ..., 270- (N-1) LPF unit 280-0, 280-1, 280-2, ..., 280- (N-1) A / D conversion unit 290-0, 290-1, 290-2, ..., 290- (N-1) Demultiplexer circuit unit 300 Digital Switch matrix section 310-0, 310-1, 310-2, ..., 310- (N'-1) Delay circuit section 320-0, 320-1, 320-2, ..., 320- (N'-1) Multiplexing circuit units 330-0, 330-1, 330-2, ..., 330- (N'-1) D / A conversion units 340-0, 340-1, 340-2, ..., 340- (N ' -1) LPF unit 350 transmission local signal generation unit 360-0, 360-1, 360-2, ..., 360- (N'-1) mixer unit 370-0, 370-1, 370-2, ..., 370 -(N'-1) BPF section 380-0, 380-1, 380-2, ..., 380- (N'-1) transmission amplifier section 390-0, 390-1, 390-2, ..., 390- (N'-1) Transmitting antenna unit 400, 402, 404 Beam area 401, 403, 4 5 receiving station 500 receiving antenna section 501 receiving amplifier section 502 BPF section 503 received local signal generating section 504 mixer section 505 LPF section 506 A / D conversion section 507 demultiplexing circuit section 508, 509 unicast demodulating section 510 for broadcast signal Demodulator 511 Cross-correlator 512 Vector phase detector 513 Synthesizer 514 Detector 520 Broadcast signal demodulator 521 Cross-correlator 522 Transmission path estimator 523 Equalizer 524 Detector

Claims (10)

Signals received from transmitting stations existing in N (N is an integer of 2 or more) receiving beam areas are transmitted to receiving stations existing in N ′ (N ′ is an integer of 2 or more) transmitting beam areas. A relay satellite that
Receive signal conversion comprising N reception signal conversion means for receiving a signal from a transmission station in one reception beam area and sampling a signal obtained by performing frequency conversion processing and band limitation processing on the received signal. A group of means;
A demultiplexing means group comprising N demultiplexing means connected to the received signal converting means in a one-to-one relationship and demultiplexing the sampled signal into a plurality of signals;
Digital switch matrix means for performing control to assign a frequency band to each signal after demultiplexing input from the demultiplexing means group, and to output in units of transmission beam areas as transmission destinations;
A delay means group including N ′ delay means for performing a delay process on a signal output in units of the transmission beam area;
A multiplexing unit group comprising N ′ coupling units that are connected to the delay units in a one-to-one relationship and that combine the delayed signals output in units of the transmission beam area;
N ′ transmission means connected to the multiplexing means on a one-to-one basis, converting the combined signal into an analog signal, and further transmitting the signal converted into the radio frequency band to the transmission beam area of the transmission destination Transmission means group,
With
When transmitting a broadcast signal received from the transmitting station or a broadcast signal generated by itself to two or more receiving stations,
The digital switch matrix means assigns each broadcast signal obtained by duplicating the broadcast signal to the same frequency band, and combines with a transmission means capable of transmitting to a transmission beam area including a destination receiving station; Output to connected delay means,
Each delay means that receives the duplicate broadcast signal gives different time delays to the broadcast signal,
A relay satellite characterized by this. If there are two or more transmitting stations in one receive beam area,
The demultiplexing means enables demultiplexing to the number of signals equal to or greater than the number of transmitting stations included in the reception beam area.
The relay satellite according to claim 1. The demultiplexing means demultiplexes so that the frequency characteristics of each filter to be demultiplexed overlap between adjacent filters, and the sum of the amplitudes of each filter in the overlap region is 1.
The relay satellite according to claim 1 or 2. The delay means, when a unicast signal other than the broadcast signal and the broadcast signal is input from the digital switch matrix means, gives the same time delay as the broadcast signal to the unicast signal,
The relay satellite according to claim 1, 2, or 3. A satellite communication system comprising the relay satellite according to any one of claims 1 to 4 and a receiving station in the transmission beam area,
The receiving station is
Received signal conversion means for receiving a signal from the relay satellite and sampling a signal obtained by performing frequency conversion processing and band limitation processing on the received signal;
A demultiplexing unit that demultiplexes the sampled signal into a signal before the multiplexing process by the multiplexing unit of the relay satellite;
Broadcast signal demodulating means for demodulating the broadcast signal;
Unicast demodulation means for demodulating a unicast signal other than the broadcast signal;
With
The demodulating means for the broadcast signal is included in the broadcast signal transmitted from the relay satellite and included in the signal for the transmission beam area where the local station exists and the signal for the transmission beam area where the local station does not exist Demodulating the broadcast signal using the broadcast signal,
A satellite communication system. When the broadcast signal is a spread spectrum signal,
The broadcast signal demodulating means includes:
Cross-correlation means that performs cross-correlation processing using the same sequence as the spread sequence of the broadcast signal, and obtains a cross-correlation vector that is a correlation value for the broadcast signal transmitted to each beam area;
Vector phase detection means for detecting the number of cross-correlation vectors, the arrival time of each vector, and each vector phase angle from the cross-correlation vector;
Combining means for synthesizing each cross-correlation vector output from the cross-correlation means using each number of the cross-correlation vectors, arrival time of each vector, and each vector phase angle information;
A detection means for performing detection on the combined signal vector and demodulating the data;
The satellite communication system according to claim 5, comprising: The receiving station is
Based on the correlation power information obtained by the cross-correlation process in the cross-correlation means, estimate the position of the own station,
The satellite communication system according to claim 6. When the broadcast signal is a PSK modulated signal or an OFDM signal,
The broadcast signal demodulating means includes:
Cross-correlation means for performing a cross-correlation process between a received signal and a known preamble using the same preamble added to the PSK modulation signal to obtain a cross-correlation data sequence;
A transmission path estimation means for extracting a cross-correlation characteristic between a preamble included in a received signal and a known preamble from the cross-correlation data series by cross-correlation power detection and obtaining a transmission path estimation value;
An equalization means for dividing the received signal converted from the time domain into the frequency domain by the transmission path estimation value converted into the frequency domain, and further converting from the frequency domain to the time domain;
A detection means for performing detection on the signal converted into the time domain and demodulating the data;
The satellite communication system according to claim 5, comprising: further,
Control for instructing the digital switch matrix means of the relay satellite to assign a frequency band to each signal after demultiplexing, and for instructing the delay means group the amount of time delay in each delay means Bureau,
The satellite communication system according to any one of claims 5 to 8, further comprising: The control station notifies the information of the time delay amount to the receiving station,
The satellite communication system according to claim 9.

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