JP2023042071A - satellite repeater - Google Patents

Abstract

To provide a satellite repeater for attaining reduction of transmission deterioration regarding two demodulation signals transmitted in overlapped frequencies from a transmission device relating to satellite digital broadcasting or satellite digital communications, and repeating and transmitting the signals to a reception device by performing layer division multiplexing so as to perform high-output repetition and transmission while maintaining excellent transmission characteristics.SOLUTION: A satellite repeater 1 of the present invention comprises: a receive antenna 11 for receiving two modulation signals for high layer and low layer from a transmission device 10; a first amplifier 12 for amplifying the modulation signal for high layer to predetermined standardized power; a second amplifier 13 for amplifying the modulation signal for low layer until it has a predetermined power difference with respect to the amplified modulation signal for high layer; and a transmit antenna 14 for transmitting to a reception device 20 a modulation signal of a layer division multiplexing system obtained by synthesizing the amplified modulation signal for high layer and the amplified modulation signal for low layer through space synthesis or signal synthesis.SELECTED DRAWING: Figure 2

Description

The present invention relates to a satellite repeater that hierarchically divides and multiplexes a plurality of modulated signals transmitted at overlapping frequencies from a transmitter for satellite digital broadcasting or satellite digital communication, and relays the signals to a receiver.

Currently, frequency division multiplexing (FDM) used in Japan's terrestrial digital broadcasting and time division multiplexing used in BS digital broadcasting are used as hierarchical transmission systems for the realization of flexible services and broadcasting/communications. There is a division multiplex (TDM: Time Division Multiplex). In addition to this, ATSC 3.0, the next-generation terrestrial digital broadcasting in the United States, has developed and adopted layered division multiplex (LDM).

Hierarchical division multiplexing (LDM) is a technique for multiplexing signals in overlapping frequencies by using a plurality of modulated signals and dividing and allocating power to each modulated signal. Hierarchical transmission schemes combining frequency division multiplexing (FDM) and hierarchical division multiplexing (LDM) are also under study (for example, see Non-Patent Document 1).

In the hierarchical division multiplexing (LDM) system in digital terrestrial broadcasting in Japan, carrier modulation is performed for each LDM modulation signal, and those signals are combined into one signal and OFDM-modulated. Therefore, in a hierarchical transmission system that combines frequency division multiplexing (FDM) and hierarchical division multiplexing (LDM) disclosed in Non-Patent Document 1, one modulation signal obtained by combining two modulated signals is transmitted from the LDM modulation device on the transmitting side. A modulated signal is generated. Therefore, it is amplified and transmitted as one modulated signal in the transmitter or ground repeater connected to the subsequent stage.

In addition, as a general LDM signal configuration, two modulated signals are used. The power difference between modulated signals is called IL (Injection level).

Such hierarchical division multiplexing (LDM) schemes may have both UL and LL with the same or different digital modulation schemes, e.g. both UL and LL with the same digital modulation scheme (e.g. QPSK). FIG. 4 shows an example constellation at this time. In FIG. 4, a hierarchical division multiplexing (LDM) modulation signal is shown as a signal point sequence signal that can be expressed as signal points of an in-phase component I and a quadrature phase component Q on an IQ plane. As shown in FIG. 4, the modulated signal after combining the UL and LL is based on the modulated signal of the high hierarchy (UL), centering on the high hierarchy (UL) (♦ shown in FIG. 4), and the low hierarchy (LL). The modulated signal becomes a signal point (● in FIG. 4) plotted with the power difference of IL (6 dB in this example).

By the way, digital terrestrial broadcasting has conventionally used multi-level modulated signals such as 64QAM, and there is no limit to power supply when using amplifiers having nonlinear characteristics in high-output terrestrial transmission stations and terrestrial relay stations. For this reason, in digital terrestrial broadcasting, by using an amplifier that has a maximum output that exceeds the operating output, it is operated at an output operating point that is significantly lower than the power-efficient saturation point (maximum output). As a result, although the power efficiency is lowered, nonlinear characteristics are hardly generated, so that good transmission characteristics can be maintained. That is, even when LDM is used in digital terrestrial broadcasting, it can be used by terrestrial transmitting stations and terrestrial relay stations that operate amplifiers similar to conventional FDM.

On the other hand, in satellite digital broadcasting or satellite digital communication via a satellite repeater, it is necessary to effectively use the limited power generated by the satellite repeater. It is required to operate the amplifier mounted on the repeater at an operating point close to the saturation point with high power efficiency. Therefore, for example, in the BS digital broadcasting that started in 2000, modulation is performed only with the phase component as a modulation signal, and by applying PSK (8PSK, QPSK, etc.) that is less susceptible to the nonlinear characteristics of the amplifier, the satellite repeater uses a TWTA with a saturated output equivalent to the operational output (120 W).

In addition, in the new 4K8K satellite broadcasting that started in 2018, APSK, which modulates both amplitude and phase components as a modulation signal, is applied in order to expand the transmission capacity per band. Considering this, it becomes necessary to use a TWTA having a saturated power (200 W) higher than the operational power (120 W) for the satellite transponder, and a satellite transponder having a higher generated power is used.

However, in a satellite repeater compatible with the new 4K8K satellite broadcasting, the output backoff of the amplifier (TWTA) is assumed to be about 2.0 dB (see, for example, Non-Patent Document 2). In this case, the operational output is limited to 125W.

Akihiko Sato, 11 others, “Study on application of LDM for next-generation terrestrial broadcasting”, Institute of Image Information and Television Engineers, Institute of Image Information and Television Engineers ITE Technical Report, Vol.41, No.6 , Session ID: BCT2017-34, pp.45-48, announced on February 23, 2017 Masaaki Kojima, 7 others, “APSK Transmission Experiments over 12GHz-band Satellite Channel Compared TWTA and SSPA”, International Communications Satellite Systems Conferences (ICSSC); 16-19 October 2017, Trieste, Italy,35th AIAA International Communications Satellite Systems Conferences; AIAA 207-5405, published online October 23, 2017

As described above, regarding terrestrial digital broadcasting, a hierarchical transmission system combining frequency division multiplexing (FDM) and hierarchical division multiplexing (LDM) has been studied, and its specific configuration is also disclosed in Non-Patent Document 1. ing. As described above, even when LDM is applied to digital terrestrial broadcasting, it is possible to use terrestrial transmission stations and terrestrial relay stations that operate amplifiers in the same manner as conventional FDM.

On the other hand, in satellite digital broadcasting or satellite digital communication via a satellite repeater, it is necessary to effectively use the limited power generated by the satellite repeater. Considering a hierarchical transmission system combining time division multiplexing (TDM) and hierarchical division multiplexing (LDM) in satellite digital broadcasting or satellite digital communication, in this case also, UL and LL are synthesized by the hierarchical division multiplexing (LDM) system. The resulting signal is modulated by both amplitude and phase components, but it is necessary to consider deterioration due to nonlinear characteristics as in APSK. This creates a need to construct satellite transponders with TWTAs that have a higher saturation power than the current operational power.

On the other hand, in the LDM constellation shown in FIG. 4, for example, there are 16 LL signal points. Since 2.0 dB is assumed, for example, a TWTA with a saturated power of 200 W would be limited to an operational power of 125 W. For this reason, a demand that contradicts the above is generated.

Therefore, in view of the above-mentioned problems, an object of the present invention is to reduce the transmission deterioration of two modulated signals transmitted at overlapping frequencies from a transmission device related to satellite digital broadcasting or satellite digital communication, and to improve transmission. To provide a satellite repeater capable of repeating transmission at high output while maintaining good characteristics.

The satellite repeater of the present invention hierarchically divides and multiplexes two modulated signals for high and low hierarchies transmitted at overlapping frequencies from a transmission device for satellite digital broadcasting or satellite digital communication, and relays them to a receiving device. A satellite repeater for transmission, comprising: a receiving antenna for receiving two modulated signals for high hierarchy and low hierarchy transmitted at overlapping frequencies from the transmitting device; a first amplifier that amplifies to a normalized power, a second amplifier that amplifies the modulated signal for the low hierarchy to a predetermined power difference with respect to the modulated signal for the high hierarchy after the amplification, and the amplification a transmitting antenna for transmitting, to the receiving device, a modulated signal of hierarchical division multiplexing, which is obtained by synthesizing the modulated signal for the later high hierarchy and the modulated signal for the low hierarchy after the amplification. do.

Further, in the satellite transponder of the present invention, the modulated signal of the hierarchical division multiplexing method is generated by spatial synthesis in the transmitting antenna, or is generated between the first amplifier and the second amplifier and the transmitting antenna. is configured to be generated by signal synthesis by a synthesizer provided in .

Further, in the satellite transponder of the present invention, the receiving antenna receives the two modulated signals for the high hierarchy and the low hierarchy as modulated signals of phase modulation, and the first amplifier and the second amplifier wherein a predetermined power difference is set between the first amplifier and the second amplifier, and a traveling wave tube amplifier having a saturated output corresponding to the power difference. .

According to the present invention, as a hierarchical transmission system using layer division multiplexing (LDM) in satellite digital broadcasting or satellite digital communication, an amplifier is used for a signal after combining modulation signals of each layer in a satellite repeater. Instead, the modulated signal for each layer is received independently, and the modulated signal for each layer is power-amplified by a predetermined power difference using a dedicated amplifier and then combined. As a result, deterioration due to non-linear characteristics in the satellite transponder is reduced, and each amplifier is brought close to the saturation point while maintaining good transmission characteristics by amplifying and then synthesizing the modulated signals of each layer. Operation at the operating point becomes possible.

1 is a block diagram showing a schematic configuration of a transmission system that realizes hierarchical division multiplexing (LDM) signal transmission via a satellite transponder of an embodiment according to the present invention; FIG. 1 is a block diagram showing a schematic configuration of a satellite transponder of Example 1 according to the present invention; FIG. FIG. 4 is a block diagram showing a schematic configuration of a satellite transponder of Example 2 according to the present invention; It is a figure which shows an example of the constellation of a hierarchical division multiplexing (LDM) system.

A satellite transponder 1 according to an embodiment of the present invention will be described in detail below with reference to the drawings.

[Transmission system]
FIG. 1 is a block diagram showing a schematic configuration of a transmission system 100 that realizes hierarchical division multiplexing (LDM) signal transmission via a satellite transponder 1 according to one embodiment of the present invention. The transmission system 100 of one embodiment shown in FIG. 1 can be a transmission system related to satellite digital broadcasting or satellite digital communication. An example conforming to S3 or the like will be described.

A transmission system 100 of one embodiment shown in FIG. Prepare.

The transmission device 10 is configured in the same manner as a transmission device related to current satellite digital broadcasting or satellite digital communication, and transmits TS packets (or A modulated signal is generated by inputting transmission data composed of IP packets) as a main signal. However, the transmission device 10 in the transmission system 100 of the present embodiment generates independent modulation signals for high hierarchy (UL) and low hierarchy (LL) for configuring LDM, and outputs them to power amplifier 10a. Output. The power amplifier 10a amplifies the high hierarchy (UL) modulation signal and the low hierarchy (LL) modulation signal output from the transmission device 10, and outputs them as uplink signals to the satellite repeater 1 via the transmission antenna 10b. Send to Here, amplitude phase shift keying (APSK) is not used for the high layer (UL) modulated signal and the low layer (LL) modulated signal output from the transmission device 10, and BPSK, QPSK, 8SPK, 16PSK, etc. are used. shall be used.

A satellite transponder 1 according to an embodiment of the present invention receives an uplink signal and generates an independent high layer (UL) modulated signal and low layer (LL) modulated signal for forming an LDM band. Extract and receive. Then, the satellite transponder 1 uses two types of amplifiers (TWTA) for separately power-amplifying the band-extracted modulated signal for high hierarchy (UL) and modulated signal for low hierarchy (LL) to obtain a predetermined power difference. (IL=6 dB in this example). Then, the satellite repeater 1 removes out-of-band unnecessary frequency components (spectrum regrowth) from the power-amplified high-level (UL) modulated signal and low-level (LL) modulated signal if necessary. A modulated signal that constitutes the LDM that is combined after being suppressed is generated, and transmitted as a downlink signal to a receiving device 20 in a terrestrial receiving facility.

The basic configuration and operation of the receiving device 20 are the same as those disclosed in Non-Patent Document 1. That is, the receiving device 20 receives the downlink signal from the satellite transponder 1 via the receiving antenna 20a, demodulates the modulated signal (combined signal including both the upper layer and the lower layer) forming the LDM, and first The data transmitted for the upper layer (UL) is restored by demodulating and error correction decoding from the upper layer. Next, the receiving device 20 again error-correction-encodes and re-modulates the decoded data for the upper layer (UL), reproduces only the modulated signal of the upper layer, and reproduces the modulated signal (upper layer) constituting the original LDM. By subtracting this regenerated modulated signal of the upper layer from the composite signal including both the layer and the lower layer, the modulated signal of only the lower layer is obtained, and demodulation and error correction decoding are performed for the lower layer (LL). Restore transmitted data.

As described above, the satellite transponder 1 according to one embodiment of the present invention is a hierarchical transmission system using hierarchical division multiplexing (LDM) in satellite digital broadcasting or satellite digital communication. Instead of using an amplifier for the signal, the modulated signal of each layer is received independently, and the modulated signal of each layer is amplified by a predetermined power difference using a dedicated amplifier and then combined. do. As a result, in the satellite repeater 1 according to the embodiment of the present invention, the deterioration due to the non-linear characteristics of the satellite repeater is reduced, and the modulated signals of each layer are amplified and then synthesized, thereby improving the transmission characteristics. It is possible to operate each amplifier at an operating point close to the saturation point while maintaining good .

In the following, the configurations of Examples 1 and 2 of the satellite transponder 1 according to one embodiment of the present invention will be described in order together with the operation thereof.

(Example 1)
FIG. 2 is a block diagram showing a schematic configuration of the satellite transponder 1 of Example 1 according to the present invention.
The satellite transponder 1 of Example 1 shown in FIG. In Example 1 shown in FIG. 2, an LDM using two QPSKs for each layer is taken as an example of the LDM modulated signal shown in FIG.

The receiving antenna 11 receives an uplink signal from the earth station shown in FIG. (LL) modulation signal is band-extracted and received, the high hierarchy (UL) modulation signal is sent to the first amplifier 12, and the low hierarchy (LL) modulation signal is sent to the second amplifier 13. Output.

Here, the receiving antenna 11 has an antenna pattern shape for band extraction of the modulated signal for high hierarchy (UL) and the modulated signal for low hierarchy (LL), or band extraction for the signal received by the antenna. Assume that an input filter (IMUX) is connected to the output stage.

The first amplifier 12 is composed of a traveling wave tube amplifier (TWTA), and for a modulated signal for high hierarchy (UL) obtained via the receiving antenna 11, a predetermined standardized power (in this example, the current power of TWTA Approximately 80% of the saturated output equivalent to the operational output), and if necessary, an output filter (OMUX) that suppresses out-of-band unwanted frequency components (spectrum regrowth) is interposed, and then to the transmitting antenna 14. Output.

The second amplifier 13 applies a predetermined power difference to the amplified high hierarchy (UL) modulated signal (e.g., LL is 6 dB less than UL, about 20%) to amplify the modulated signal for the low hierarchy (LL) obtained via the receive antenna 11 and, if necessary, out-of-band undesired frequencies. After interposing an output filter (OMUX) that suppresses the component (spectrum regrowth), it is output to the transmission antenna 14 .

The transmitting antenna 14 spatially separates the amplified high hierarchical (UL) modulated signal obtained from the first amplifier 12 and the amplified low hierarchical (LL) modulated signal obtained from the second amplifier 13 . A combined LDM modulated signal is generated by combining, and transmitted as a downlink signal to a receiving device 20 in a ground receiving facility.

(Example 2)
FIG. 3 is a block diagram showing a schematic configuration of the satellite transponder 1 of Embodiment 2 according to the present invention. Components similar to those shown in FIG. 2 are given the same reference numerals. The satellite transponder 1 of Example 2 shown in FIG. Compared with the first embodiment shown in FIG. 2, the satellite repeater 1 of the second embodiment shown in FIG. is provided, and the LDM modulated signal is transmitted from a transmission antenna 16. Other configurations are the same. Also in the second embodiment shown in FIG. 3, LDM using two QPSKs for each layer is taken as an example of the LDM modulated signal shown in FIG.

The receiving antenna 11 shown in FIG. 3 is configured in the same manner as in Embodiment 1 described above, and receives an uplink signal from the earth station shown in FIG. The modulated signal for the high hierarchy (UL) and the modulated signal for the low hierarchy (LL) are band-extracted and received independently, and the modulated signal for the high hierarchy (UL) is sent to the first amplifier 12, the low hierarchy The modulated signal for (LL) is output to the second amplifier 13 .

The first amplifier 12 is configured in the same manner as in the first embodiment described above, and for a modulated signal for high hierarchy (UL) obtained via the receiving antenna 11, a predetermined standardized power (in this example, the current power of TWTA Approximately 80% of the saturated output equivalent to the operational output), and if necessary, an output filter (OMUX) that suppresses out-of-band unwanted frequency components (spectrum regrowth) is interposed. Output to combiner 15 .

The second amplifier 13 is configured in the same manner as in the first embodiment described above, and for the modulated signal for low hierarchy (LL) obtained via the receiving antenna 11, the modulated signal for high hierarchy (UL) after amplification is amplifies to a predetermined power difference (for example, LL is 6 dB smaller than UL, about 20% of the saturated output, which is equivalent to the current operational output of TWTA), and if necessary, out-of-band unwanted frequency components (spectrum reverb). After interposing an output filter (OMUX) for suppressing the growth, the signal is output to the combiner 15 in this embodiment.

The combiner 15 combines the amplified high hierarchy (UL) modulated signal obtained from the first amplifier 12 and the amplified low hierarchy (LL) modulated signal obtained from the second amplifier 13 . A combined LDM modulated signal is generated by combining and output to the transmitting antenna 16 .

The transmitting antenna 16 receives the LDM modulated signal obtained from the combiner 15 and transmits it as a downlink signal to the receiving apparatus 20 in the receiving facility on the ground.

In the satellite transponders 1 according to the first and second embodiments described above, the modulation signals of the high hierarchy (UL) shown in FIGS. 2 and 3 (corresponding to ♦ shown in FIG. 4) The modulated signal (● shown in FIG. 4) is spatially combined by the transmitting antenna 14 or signal-combined by the combiner 15 to generate the LDM modulated signal after combining the UL and LL. Then, as shown in FIG. 4 described above, the LDM modulated signal after combining the UL and LL is based on the high hierarchical (UL) modulated signal (♦ shown in FIG. 4) centering on the high hierarchical (UL), The modulated signal of the low layer (LL) becomes a signal point (● in FIG. 4) plotted with the power difference of IL (6 dB in this example).

Thus, in the satellite transponders 1 according to the first and second embodiments, the first and second amplifiers 12 and 13 are provided independently for high hierarchy (UL) and low hierarchy (LL). By doing so, it is possible to perform amplification in a state that is less susceptible to the influence of nonlinear characteristics. Also, when setting the first and second amplifiers 12 and 13 according to the power difference IL between the high hierarchy (UL) and the low hierarchy (LL), the total output is the saturated output of the amplifier (TWTA). By setting them to be the same, it is possible to make them the same as the current operational output, and to avoid an increase in generated power. From the viewpoint of stable operation, it is preferable to use spatial combining by the transmitting antenna 14 as shown in FIG. 2 and signal combining by the combiner 15 as shown in FIG. However, various other combining methods are possible. For example, a configuration may be adopted in which two types of transmission antennas are prepared and an LDM modulated signal is generated as an output thereof.

(Summary)
As described above as the prior art and the problem of the present application, when a signal obtained by combining UL and LL of LDM in a satellite repeater is amplified by one amplifier, the combined signal is modulated by both amplitude and phase components. , resulting in the need to use amplifiers with higher saturated power than the current operating power. On the other hand, in the LDM constellation shown in FIG. 4, for example, there are 16 LL signal points. Since 2.0 dB is assumed, for example, a TWTA with a saturated power of 200 W would be limited to an operational power of 125 W.

On the other hand, in the satellite transponder 1 of each embodiment according to the present invention, the UL and LL of the LDM are amplified by separate amplifiers, and at the stage of amplification, the PSK (modulated only with the phase component) signal is amplified. If so, it is possible to use an amplifier for each stratum that has a saturated power equivalent to the current operational power. In particular, the first amplifier 12 and the second amplifier 13 can set their respective saturated outputs according to a predetermined power difference (IL) set in the first amplifier 12 and the second amplifier 13. Therefore, it is preferable to set the operational output to be equal to the saturated output. For example, by setting the total output of the first and second amplifiers 12 and 13 that respectively amplify the UL and LL modulated signals to 200 W, the IL is 6 dB in the LDM shown in FIG. By setting the saturation power of the first amplifier 12 to be used to 160 W, which is about 80%, and the saturation power of the second amplifier 13 to be used for LL, to 40 W, which is about 20%, the total output of 200 W is allocated as it is to the operation output. becomes possible.

Therefore, according to the satellite transponder 1 of each embodiment of the present invention, deterioration due to nonlinear characteristics is reduced, and transmission characteristics are maintained well by amplifying modulated signals of each layer and then synthesizing them. However, it is possible to operate each amplifier at an operating point close to the saturation point.

Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above-described embodiments, and can be variously modified without departing from the technical idea thereof. For example, in the above description, as a preferred example, when setting the first and second amplifiers 12 and 13 according to IL, which is the power difference between high hierarchy (UL) and low hierarchy (LL), each saturated output is An example of setting to be equal to the operational output was explained. In the above description, as a preferred example, amplitude phase modulation is applied to the high layer (UL) modulated signal and the low layer (LL) modulated signal output from the transmission device 10 so as to be equivalent to the current operational output. (APSK) is not used. However, the actual operation of the satellite transponder 1 according to the present invention does not need to be limited to this. If it can be determined with a margin from the saturation output of , not only phase modulation (PSK) but also amplitude phase shift keying (APSK) can be used for the modulation signal of each layer.

Accordingly, the present invention should not be construed as limited by the above-described embodiments, but only by the appended claims.

According to the present invention, by combining the modulated signals of each layer after amplifying them individually, it is possible to operate each amplifier at an operating point close to the saturation point while maintaining good transmission characteristics. , for hierarchical division multiplexing (LDM) signaling applications.

1 satellite repeater 10 transmitting device 10a power amplifier at earth station 10b transmitting antenna at earth station 11 receiving antenna at satellite repeater 12 first amplifier at satellite repeater 13 second amplifier at satellite repeater 14 transmission at satellite repeater Antenna 15 Combiner in satellite repeater 16 Transmitting antenna in satellite repeater 20 Receiving device in receiving facility 20a Receiving antenna in receiving facility 100 Transmission system

Claims (3)

A satellite repeater that hierarchically divides and multiplexes two modulated signals for high and low hierarchies that are transmitted at overlapping frequencies from a transmission device for satellite digital broadcasting or satellite digital communication, and relay-transmits the signals to a receiving device. ,
a receiving antenna for receiving two modulated signals for high hierarchy and low hierarchy transmitted on overlapping frequencies from the transmitting device;
a first amplifier that amplifies the modulation signal for high hierarchy up to a predetermined normalized power;
a second amplifier that amplifies the modulated signal for the low hierarchical level to a predetermined power difference with respect to the modulated signal for the high hierarchical level after the amplification;
a transmitting antenna configured to transmit a hierarchical division multiplexing modulated signal obtained by synthesizing the amplified modulated signal for high hierarchy and the amplified modulated signal for low hierarchy to the receiving device;
A satellite repeater comprising: The modulated signal of the hierarchical division multiplexing method is generated by spatial combining in the transmitting antenna, or is combined by a combiner provided between the first amplifier and the second amplifier and the transmitting antenna. 2. A satellite transponder as claimed in claim 1, characterized in that it is configured to generate by: The receiving antenna receives the two modulated signals for the high hierarchy and the low hierarchy as modulated signals of phase modulation,
Said first amplifier and said second amplifier have a predetermined power difference set between said first amplifier and said second amplifier, and a traveling wave tube having a saturated output corresponding to the power difference. 3. A satellite transponder according to claim 1 or 2, characterized in that it comprises an amplifier.

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