Digital signal transmission device

Abstract

To provide a digital signal transmission device capable of improving required C / N on the receiving side while reducing spectrum regrowth on a broadcast transmission line by compensating for distortion in a broadcast transmission line in a satellite broadcasting transmission system.SOLUTION: A transmission device 1 according to the present invention includes a data signal generator 11 that converts transmission data into an IQ data signal, a first distortion compensation unit 16 that pre-compensates an error in the IQ signal point caused by a satellite repeater 2 on a broadcast transmission path for the IQ data signal, a waveform shaping unit 13 that performs waveform shaping on the signal of the IQ data by the processing of the first distortion compensation unit 16, a second distortion compensation unit 17 that pre-compensates the error of the IQ signal point caused by a high power amplifier 1a of the earth station on the broadcast transmission path for the IQ data signal after the waveform shaping, and a transmission signal generation unit 14 that generates a modulated wave signal for the IQ data signal that has undergone distortion compensation by the processing of the second distortion compensation unit 17, and transmits the modulated wave signal to the high power amplifier 1a.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a digital signal transmission device for compensating for distortion of a broadcast transmission path in a satellite broadcast transmission system.

Background Art

[0002] Among the transmission devices related to digital broadcasts of various standards currently in operation, the digital signal transmission device for satellite broadcasts uses a satellite repeater provided on a broadcast satellite to multiplex broadcast wave signals so that a plurality of broadcasters can transmit independent TS (Transport Stream). The standards for this satellite digital broadcast include ISDB-S, ISDB-S3, DVB-S2, DVB-S2X, etc. both at home and abroad.

[0003] Generally speaking about the components in the broadcast transmission path in the satellite broadcast transmission system that conforms to these standards, there is a high-power amplifier (HPA) of an earth station used for power amplification of an uplink signal as a ground transmission path, and a satellite repeater that receives the uplink signal as a satellite transmission path, amplifies the power, relays it, and generates and radiates a downlink signal toward each receiving device on the ground.

[0004] With reference to FIG. 5, a schematic configuration of a conventional transmission device 10 generalized for satellite broadcasts conforming to the ISDB-S3 system will be described. FIG. 5 is a block diagram showing a schematic configuration of a conventional transmission device 10 for satellite broadcasts in a prior art without a distortion compensation function.

[0005] The conventional transmission device 10 includes a data signal generation unit 11, an upsampling unit 12, a waveform shaping unit 13, and a transmission signal generation unit 14.

[0006] The data signal generation unit 11 takes as the main signal the transmission data that constitutes the digital signal with TS packets such as video, audio, and data broadcasts in the TS for each broadcaster, performs predetermined preprocessing including error correction encoding on the information bit sequence of the main signal to generate a signal of the encoded bit sequence, and performs mapping using a mapping table based on a predetermined modulation method to convert it into a signal of IQ data (a digital data signal that can be represented as a signal point sequence of the in-phase component I and the quadrature phase component Q and represented as a signal point on the IQ plane). It is a functional unit equipped with a transmission preprocessing unit 111 and a mapping unit 112.

[0007] The transmission preprocessing unit 111 takes as the main signal the transmission data that constitutes the digital signal, assigns the main signal to modulation slots in block units that make up a predetermined transmission frame, performs predetermined preprocessing including error correction encoding on the information bit sequence including the synchronization signal and the main signal assigned in that block unit to generate a signal of the modulation slot of the encoded bit sequence, and outputs it to the mapping unit 112.

[0008] The mapping unit 112 performs mapping on the signal of the modulation slot obtained from the transmission preprocessing unit 111 using a mapping table based on a predetermined modulation method to convert it into a signal of IQ data and outputs it to the upsampling unit 12. Although not shown in the figure, a modulation slot for the TMCC (Transmission and Multiplexing Configuration and Control) signal is also generated separately from the modulation slot for the main signal. The modulation method for the main signal is specified by the control information shown in the TMCC signal, and there are π / 2 shift BPSK, QPSK, 8PSK, 16APSK, and 32APSK. Also, the modulation method for the TMCC signal is π / 2 shift BPSK. Then, the signals of the modulation slots for the main signal and the modulation slots for the TMCC signal of each modulation method are transmitted in time-division multiplexing.

[0009] The upsampling unit 12 performs upsampling by a factor of two or more on the sample points of the IQ data signal obtained from the mapping unit 112, and outputs the result to the waveform shaping unit 13.

[0010] The waveform shaping unit 13 performs waveform shaping to remove unnecessary high-frequency components by applying a predetermined band-limiting filter process to the IQ data signal including the upsampled non-sample points obtained from the upsampling unit 12, generates an IQ data signal after waveform shaping, and outputs it to the transmission signal generation unit 14. As the band-limiting filter, a digital filter generally having a root roll-off characteristic is used. In ISDB-S3, a root roll-off filter with a roll-off rate of 0.03 is used.

[0011] The transmission signal generation unit 14 is a functional unit that generates a modulated wave signal according to the predetermined modulation method for the IQ data signal after waveform shaping by the waveform shaping unit 13, and includes an orthogonal modulation unit 141, a DA (digital / analog) conversion unit 142, and a frequency conversion unit 143.

[0012] The orthogonal modulation unit 141 generates a baseband IQ signal based on orthogonal modulation processing according to the predetermined modulation method for the IQ data signal after waveform shaping obtained from the waveform shaping unit 13, and outputs it to the DA conversion unit 142.

[0013] The DA conversion unit 142 performs digital / analog conversion processing on the baseband IQ signal obtained from the orthogonal modulation unit 141 to generate a modulated wave signal, and outputs it to the frequency conversion unit 143.

[0014] The frequency conversion unit 143 frequency-converts the modulated wave signal obtained from the DA conversion unit 142 into a modulated wave signal in the radio frequency band of the uplink signal, and transmits it to the high-power amplifier (HPA) of the earth station. For example, in the transmission system of the ISDB-S3 satellite broadcast, the radio frequency of the uplink signal is in the 17 GHz band.

[0015] Then, the high-power amplifier (HPA) of the earth station generates an uplink signal obtained by power-amplifying the modulated wave signal obtained from the transmission signal generation unit 14, and uplinks it to the satellite repeater of the broadcast satellite. The satellite repeater receives the uplink signal, power-amplifies and relays it, and generates and radiates a downlink signal directed to each receiving device on the ground. Then, each receiving device receives and demodulates the downlink signal, performs a decoding process corresponding to the reverse process of each process in the transmission device 10, and restores the transmission data transmitted by the transmission device 10.

[0016] In addition, the satellite repeater of an actual broadcast satellite (actual satellite) includes an input multiplexer filter (hereinafter referred to as "IMUX filter"), which is an input filter placed in front of a traveling wave tube amplifier, a traveling wave tube amplifier (hereinafter referred to as "TWTA"), an output multiplexer filter (hereinafter referred to as "OMUX filter"), which is an output filter placed behind the traveling wave tube amplifier, and the like. Then, the satellite repeater extracts the band for each channel from the received uplink signal by the IMUX filter, performs power amplification for each channel by the TWTA, suppresses unnecessary frequency components outside the band (spectrum regrowth) by the OMUX filter, synthesizes the broadcast wave signals for all channels by a synthesizer following the OMUX filter, and transmits a downlink signal (broadcast wave signal) to a plurality of receiving devices on the ground.

[0017] Here, FIG. 6 shows an example of the input / output characteristics of the high-power amplifier (HPA) of the earth station, that is, the characteristics of the normalized output power with respect to the normalized input power (AM / AM characteristics) normalized so as to be within a predetermined power, and the characteristics of the phase shift of the normalized output with respect to the normalized input power (AM / PM characteristics).

[0018] Further, FIG. 7 shows an example of the input / output characteristics of the traveling wave tube amplifier (TWTA) in the satellite repeater of the actual satellite, that is, the characteristics of the normalized output power with respect to the normalized input power (AM / AM characteristics) normalized so as to be within a predetermined power, and the characteristics of the phase shift of the normalized output with respect to the normalized input power (AM / PM characteristics).

[0019] Further, FIG. 8 shows, as frequency responses caused by the input / output characteristics of the IMUX filter and the OMUX filter in the satellite repeater of the actual satellite, an example of a frequency-versus-amplitude characteristic showing the amplitude with respect to a normalized frequency normalized to be within a predetermined band, and a frequency-versus-group-delay characteristic showing the group delay with respect to the normalized frequency.

[0020] The high-power amplifier (HPA) of the earth station and the satellite repeater of the actual satellite are indispensable in the satellite broadcast transmission system. On the other hand, as understood from FIGS. 6 and 7, as input / output characteristics, due to the influence of the output power (amplitude) and its phase shift, a deviation occurs from the desired IQ signal point as the modulated wave signal of the transmission device 10. In particular, as shown in FIG. 8, in the IMUX filter and the OMUX filter, inter-symbol interference occurs due to the influence of frequency amplitude, group delay characteristics, etc., and a spread occurs from the desired IQ signal point.

[0021] And it is known that these deviations and spreads of the IQ signal points affect each other on the broadcast transmission path, resulting in an increase in the required C / N on the receiving device side and deterioration of the transmission quality (see, for example, Non-Patent Document 1).

[0022] Furthermore, in the case of modulation schemes of multi-value amplitude phase modulation such as 16APSK and 32APSK, power amplifiers such as the high-power amplifier (HPA) of the earth station and the TWTA in the satellite repeater of the actual satellite generally attempt to operate with backoff. Also, in the non-linear amplification of the high-power amplifier (HPA) of the earth station, apart from the problem of the increase in the required C / N caused by the non-linear characteristics, a problem of an increase in spectral regrowth also occurs because no output filter is provided.

[0023] Here, the back-off in the high-power amplifier (HPA) of the terrestrial station and the traveling-wave tube amplifier (TWTA) in the satellite repeater of the actual satellite will be described in detail below. In principle, it is desirable for the high-power amplifier (HPA) and the TWTA to perform power amplification processing such that the relationship between the input level and the output level is a proportional relationship. However, this input-output characteristic actually exhibits non-linear characteristics where the gain decreases as the input level increases, and at the same time, the phase of the output signal with respect to the input signal also rotates. Therefore, when the input level is gradually increased, the output level also increases up to a certain level, but when the input level exceeds a certain level, the output level conversely decreases. The operating point immediately before such a decrease in the output level occurs is generally referred to as the output saturation point. Also, the case of operating with the input level reduced by X [dB] from this output saturation point is called "input back-off X [dB]", and similarly, the case of operating with the input level restricted and the output level reduced by Y [dB] is called "output back-off Y [dB]".

[0024] It is also known that when attempting such an operation with back-off, the output power decreases, and as a result, the received C / N margin in the receiving device becomes smaller (see Non-Patent Document 1). On the receiving device side in the satellite broadcast transmission system, generally, the aperture diameter of the receiving antenna is as small as 45 cm, and even on a sunny day, the received C / N margin is as small as about 20 dB. For this reason, these required C / N and the output back-off are in a trade-off relationship, and an operation in which the added value of the required C / N and the output back-off is as small as possible is advantageous in terms of line design (see Non-Patent Document 1).

[0025] Therefore, the receiving device can continuously monitor the control information of the TMCC signal multiplexed and transmitted together with the main signal transmitted as a broadcast wave signal, and can switch the receiving method (such as switching the modulation method and the coding rate of the error correction code) accordingly even if various transmission controls are performed on the transmitting device side.

[0026] Incidentally, as a transmission device of the prior art, a transmission device having a distortion compensation function for transmission path distortion generated in a satellite repeater is also disclosed (see, for example, Patent Document 1). FIG. 9 is a block diagram showing a schematic configuration of a satellite broadcast transmission device 10A with a distortion compensation function for a satellite repeater in the prior art, which is generalized for understanding in comparison with that shown in FIG. 5. In FIG. 9, the same reference numerals are assigned to the same components as those of the transmission device 10 shown in FIG. 5.

[0027] The transmission device 10A shown in FIG. 9 is different from the transmission device 10 shown in FIG. 5 in that a distortion compensation unit 15 (however, including the function of the upsampling unit 12) is provided between the data signal generation unit 11 and the waveform shaping unit 13, and other components are configured similarly.

[0028] For the signal of the IQ data obtained from the mapping unit 112, the distortion compensation unit 15 first performs waveform shaping in an upsampled state in the same manner as the function of the upsampling unit 12, and generates a signal that pseudo-causes transmission path distortion caused by the satellite repeater using the input / output characteristics of a pseudo-satellite repeater that pseudo-represents the satellite repeater of the actual satellite. Subsequently, the distortion compensation unit 15 performs waveform shaping on the signal that pseudo-causes transmission path distortion caused by the satellite repeater, and performs a first vector operation of subtracting the corresponding original IQ data signal point from the IQ signal point obtained by downsampling so as to correspond to the original IQ data signal to obtain an error vector. Then, for the error vector, the distortion compensation unit 15 performs a second vector operation of subtracting the error vector multiplied by a predetermined coefficient weight from the original IQ data signal point in order to use the inverse vector from the ideal transmission signal point (hereinafter referred to as the "ideal signal point") as the correction vector, thereby generating a distortion-compensated IQ data signal, and performs upsampling on the distortion-compensated IQ data signal in the same manner as the function of the upsampling unit 12 and outputs it to the waveform shaping unit 13.

[0029] Therefore, the transmission device 10A shown in FIG. 9 has a function of generating a signal of distortion-compensated IQ data by causing a distortion compensator 15 in the stage before the waveform shaping unit 13 to generate transmission path distortion in the actual satellite in advance using the input / output characteristics of the pseudo satellite repeater, and then correcting the signal points of the original IQ data by vector calculation. As a result, in the downlink signal (broadcast wave signal) radiated from the satellite repeater of the actual satellite, the deviation and spread of the IQ signal points due to the satellite repeater of the actual satellite are canceled, so that the receiving device side can converge to the ideal signal points, and the required C / N on the receiving device side can be improved.

Prior Art Documents

Patent Documents

[0030]

Patent Document 1

Non-Patent Documents

[0031]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0032] A conventional DPD (Digital Pre-Distortion) technology incorporated in Patent Document 1 and Non-Patent Document 1 related to a satellite broadcast transmission system targets only the satellite transmission path (satellite repeater) for distortion compensation, and the high-power amplifier (HPA) at the earth station is not targeted for distortion compensation. The reason for this is generally considered to be that the high-power amplifier (HPA) at the earth station can take more back-off compared to the satellite repeater. For example, according to Non-Patent Document 2, the output back-off of the satellite repeater is set at 2.2 dB, while the high-power amplifier (HPA) at the earth station has a large back-off amount of 5 to 7 dB.

[0033] However, in the case of a multi-value modulation method such as 32APSK, even with the above operating point setting for the high-power amplifier (HPA) at the earth station, the reception performance deteriorates (see Non-Patent Document 2). Furthermore, in a transmission device incorporating the DPD technology disclosed in Patent Document 1 and Non-Patent Document 1, since the high-power amplifier (HPA) at the earth station is assumed to be ideal linear amplification, when non-linear distortion occurs in the high-power amplifier (HPA) at the earth station, which is in the front stage of the satellite repeater, it is expected that not only the degradation caused by the high-power amplifier (HPA) at the earth station but also the effect of DPD targeting the satellite repeater will deteriorate.

[0034] Therefore, in order to solve the problem of non-linear distortion in the high-power amplifier (HPA) at the earth station by applying the technology of Patent Document 1, a method of including the pseudo transmission path in the technology of Patent Document 1 up to the high-power amplifier (HPA) at the earth station can be considered. That is, for the pseudo transmission path (pseudo satellite repeater) of the distortion compensator in the transmission device, the configuration is changed from IMUX filter - TWTA - OMUX filter to high-power amplifier (HPA) at the earth station - IMUX filter - TWTA - OMUX filter to expand the range of the pseudo transmission path. As a result, the non-linear distortion of the high-power amplifier (HPA) at the earth station is also reduced, so the required C / N becomes smaller and an improvement in reception performance can be expected.

[0035] However, since the DPD technology using the method of expanding the range of this pseudo transmission line is signal processing in the front stage of waveform shaping related to the modulated wave signal, even if the signal within the Nyquist band can be distortion-compensated, it is impossible to reduce the spectrum regrowth of the high-power amplifier (HPA) of the earth station outside the Nyquist band. On the contrary, if dynamic distortion compensation is performed prior to the waveform shaping by such a method of expanding the range of the pseudo transmission line, the instantaneous power of the modulated wave signal will increase more, and the modulated wave signal will be non-linearly amplified via the high-power amplifier (HPA) of the earth station. As a result, there is even a concern that the spectrum regrowth will increase. In addition, radio transmission (uplink signal and downlink signal) in the satellite broadcast transmission system is regulated by the Radio Law to be suppressed to within an occupied bandwidth of 34.5 MHz or less per channel (see Non-Patent Document 2). If the spectrum regrowth increases, there is a concern that this condition will not be met.

[0036] Therefore, in view of the above problems, an object of the present invention is to provide a transmission device for a digital signal that can perform distortion compensation of a broadcast transmission line in a satellite broadcast transmission system, reduce the spectrum regrowth on the broadcast transmission line, and improve the required C / N on the receiving side.

Means for Solving the Problems

[0037] The transmission device of the present invention is a transmission device that transmits a digital signal toward a receiving device via a broadcast transmission path including a high-power amplifier of an earth station and a satellite repeater in a satellite broadcast transmission system. The transmission device inputs transmission data constituting the digital signal as a main signal, performs predetermined preprocessing including error correction coding processing on the information bit sequence of the main signal to generate a signal of a coded bit sequence, and performs mapping by a mapping table based on a predetermined modulation method to convert it into an IQ data signal represented by a signal point sequence of an in-phase component and a quadrature phase component. A data signal generation unit, for the IQ data signal, a first distortion compensation unit that generates an IQ data signal that has been distortion-compensated by a first distortion compensation process for pre-correcting an error in the IQ signal point caused by the satellite repeater, and for the IQ data signal after the first distortion compensation process, performs predetermined band-limiting filter processing to perform waveform shaping, and a waveform shaping unit that generates an IQ data signal after waveform shaping that has undergone the first distortion compensation process, and for the IQ data signal after waveform shaping that has undergone the first distortion compensation process, a second distortion compensation unit that generates an IQ data signal that has been distortion-compensated by a second distortion compensation process for pre-correcting an error in the IQ signal point caused by the high-power amplifier of the earth station, and for the IQ data signal that has been distortion-compensated by the second distortion compensation process, generates a modulated wave signal by the predetermined modulation method and transmits it to the high-power amplifier of the earth station, and is characterized by comprising a transmission signal generation unit.

[0038] Also, in the transmission apparatus of the present invention, as the first distortion compensation process, the first distortion compensation unit once performs waveform shaping on the signal of the IQ data obtained from the data signal generation unit in an upsampled state, generates a signal that pseudo-causes transmission path distortion due to the satellite repeater using a table file approximating the input / output characteristics of the satellite repeater, performs a first vector operation of subtracting the corresponding original IQ data signal point from the IQ signal point obtained by performing waveform shaping and then downsampling to correspond to the original IQ data signal to obtain an error vector, and performs a second vector operation of subtracting the error vector multiplied by a predetermined coefficient weight from the original IQ data signal point in order to use the inverse vector from the ideal signal point with respect to the error vector as a correction vector, and performs an upsampling process to pre-correct the error of the IQ signal point due to the satellite repeater, thereby generating a distortion-compensated IQ data signal.

[0039] Also, in the transmission apparatus of the present invention, as the second distortion compensation process, the second distortion compensation unit pre-corrects the error of the IQ signal point due to the high-power amplifier of the earth station using a table file indicating a value that is the inverse component of the input / output characteristics of the high-power amplifier of the earth station for the signal of the IQ data after waveform shaping that has undergone the first distortion compensation process, thereby generating a distortion-compensated IQ data signal.

Effect of the Invention

[0040] According to the transmission device of the present invention, by adopting a configuration that includes individual distortion compensation means (a first distortion compensation unit and a second distortion compensation unit) before and after waveform shaping related to the modulated wave signal, it is possible to reduce the spectral regrowth outside the Nyquist band in the uplink signal, which could not be solved by the conventional DPD (corresponding to a configuration having only the first distortion compensation unit), by the second distortion compensation unit. Furthermore, according to the transmission device of the present invention, since the distortion compensation for the satellite repeater 2 can be executed without any adverse effects in the same manner as in the prior art by the first distortion compensation unit, the required C / N as the reception characteristic is also improved, and it is possible to reduce the spectral regrowth of the uplink signal and improve the reception performance. And, according to the transmission device of the present invention, since the characteristics of the broadcast transmission path in the first distortion compensation unit and the second distortion compensation unit can be sequentially updated by rewriting the table file in the process of simulating the characteristics of the broadcast transmission path, it has high versatility for various transmission systems and broadcast transmission paths without depending on the signal formats of various transmission systems.

Brief Description of the Drawings

[0041]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0042] Hereinafter, with reference to the drawings, a transmission device 1 according to an embodiment of the present invention will be described.

[0043] 〔Transmission System〕 First, FIG. 1 is a block diagram showing the schematic configuration of a satellite broadcast transmission system according to an embodiment including a transmission device 1 according to an embodiment of the present invention. The transmission system according to the embodiment shown in FIG. 1 can comply with standards adopted in digital broadcasting, such as ISDB-S, ISDB-S3, DVB-S2, DVB-S2X, etc., and includes a transmission device 1 at a terrestrial broadcast station, a high power amplifier (HPA) 1a of an earth station, a satellite repeater 2, and a plurality of receiving devices 3-1, 3-2,..., 3-n (hereinafter, n is an integer of 1 or more, and is collectively referred to as "receiving device 3").

[0044] The transmission device 1 of this embodiment will be described in detail with reference to FIG. 2. It inputs transmission data composed of TS packets such as video, audio, and data broadcasts in the TS for each broadcaster as a main signal, generates a modulated wave signal that compensates for transmission path distortion caused by both the high power amplifier (HPA) 1a of the earth station and the satellite repeater 2 of the real satellite, and transmits it to the high power amplifier (HPA) 1a of the earth station. It can replace the existing conventional transmission device 10 shown in FIG. 5, or be installed separately from the existing conventional transmission device 10 and incorporated as a transmission system 1.

[0045] The satellite repeater 2 mounted on the broadcast satellite includes an IMUX filter 21, a TWTA 22, and an OMUX filter 23. As described above, the IMUX filter 21 receives the modulated wave signal transmitted as an uplink signal by the ground transmitter 1, extracts the bandwidth for each channel from the modulated wave signal, performs power amplification by the TWTA 22, suppresses unnecessary out-of-band frequency components (spectral regrowth) by the OMUX filter 23, synthesizes the broadcast wave signals for all channels by a synthesizer (not shown) following the OMUX filter 23, and transmits a downlink signal (broadcast wave signal) toward a plurality of ground receiving devices 3.

[0046] The receiving device 3 is configured as a device that receives and demodulates the downlink signal from the satellite repeater 2, performs a decoding process corresponding to the reverse process of each process in the transmitting device 1, and restores the transmission data transmitted by the transmitting device 1. It has the same configuration as a receiving device compliant with the ISDB-S3 system based on the prior art, and further description thereof is omitted.

[0047] Here, the high-power amplifier (HPA) 1a of the earth station and the satellite repeater 2 of the actual satellite have the input-output characteristics illustrated in FIGS. 6 and 7 as described in the prior art. Due to the influence of the output power (amplitude) and its phase shift, a deviation occurs from the desired IQ signal point as the modulated wave signal of the transmitting device 1. Further, the satellite repeater 2 of the actual satellite has a frequency response caused by the input-output characteristics of the IMUX filter 21 and the OMUX filter 23 shown in FIG. 8. The IMUX filter and the OMUX filter cause inter-symbol interference due to the influence of frequency amplitude, group delay characteristics, etc., and a spread occurs from the desired IQ signal point.

[0048] Therefore, the transmitting device 1 according to the present invention is configured to generate a modulated wave signal that compensates for the transmission path distortion caused by both the high-power amplifier (HPA) 1a of the earth station and the satellite repeater 2 of the actual satellite, and will be described more specifically below.

[0049] 〔Transmitting Device〕 FIG. 2 is a block diagram showing a schematic configuration of a transmission apparatus 1 according to an embodiment of the present invention, which is generalized for understanding in comparison with that shown in FIG. 5. In FIG. 2, the same components as those of the transmission apparatus 10 shown in FIG. 5 are denoted by the same reference numerals.

[0050] Here, a transmission apparatus 1 according to an embodiment of the present invention shown in FIG. 2 is different from the transmission apparatus 10 shown in FIG. 5 in that a first distortion compensation unit 16 (however, including the functions of the upsampling unit 12 shown in FIG. 5) is provided between a data signal generation unit 11 and a waveform shaping unit 13, and a second distortion compensation unit 17 is provided between the waveform shaping unit 13 and a transmission signal generation unit 14, and other components are configured in the same manner. The first distortion compensation unit 16 shown in FIG. 2 functions in the same manner as the distortion compensation unit 15 shown in FIG. 9, and a more specific configuration will be described later with reference to FIG. 3.

[0051] Referring to FIG. 2, the transmission apparatus 10 of this embodiment includes a data signal generation unit 11, a first distortion compensation unit 16, a waveform shaping unit 13, a second distortion compensation unit 17, and a transmission signal generation unit 14.

[0052] The data signal generation unit 11, in the same manner as in the prior art, inputs, as a main signal, transmission data that constitutes a digital signal with TS packets such as video, audio, and data broadcasts in a TS for each broadcaster, performs predetermined preprocessing including error correction coding processing on the information bit sequence of the main signal to generate a signal of an encoded bit sequence, and performs mapping by a mapping table based on a predetermined modulation method to convert it into a signal of IQ data (a digital data signal that can be represented as a signal point sequence of an in-phase component I and a quadrature phase component Q and represented as a signal point on an IQ plane). The data signal generation unit 11 includes a transmission preprocessing unit 111 and a mapping unit 112.

[0053] The pre - transmission processing unit 111 inputs the transmission data constituting the digital signal as the main signal, allocates the main signal to modulation slots in block units that make up a predetermined transmission frame, and performs predetermined pre - processing including error - correction coding on the information bit sequence including the synchronization signal and the main signal allocated in block units, generates signals for the modulation slots of the coded bit sequence, and outputs them to the mapping unit 112.

[0054] The mapping unit 112 performs mapping on the signals of the modulation slots obtained from the pre - transmission processing unit 111 using a mapping table based on a predetermined modulation method to convert them into signals of IQ data, and outputs them to the up - sampling unit 12. Although not shown in the figure, modulation slots for TMCC signals are also generated separately from the modulation slots for the main signal. The modulation method for the main signal is specified by the control information shown in the TMCC signal, and there are π / 2 - shifted BPSK, QPSK, 8PSK, 16APSK, 32APSK. Also, the modulation method for the TMCC signal is π / 2 - shifted BPSK. And the signals of the modulation slots for the main signal and the signals of the modulation slots for the TMCC signal of each modulation method are transmitted in time - division multiplexing.

[0055] The first distortion compensation unit 16, which will be described in detail later with reference to FIG. 3, is configured in the same manner as the distortion compensation unit 15 in the prior art shown in FIG. 9. That is, the first distortion compensation unit 16 once performs waveform shaping on the signal of the IQ data obtained from the mapping unit 112 in an upsampled state, generates a signal that pseudo-causes transmission path distortion due to the satellite repeater 2 of the actual satellite using a table file approximating the input / output characteristics of the satellite repeater 2 of the actual satellite, performs waveform shaping, and performs a first vector operation of subtracting the corresponding original IQ data signal point from the IQ signal point obtained by downsampling so as to correspond to the original IQ data signal before waveform shaping to obtain an error vector. For using the inverse vector viewed from the ideal signal point of the error vector as a correction vector, a second vector operation of subtracting the error vector multiplied by a predetermined coefficient weight from the original IQ data signal point is performed, and an IQ data signal compensated for distortion is generated by the first distortion compensation process of upsampling, and the IQ data signal compensated for distortion is upsampled and output to the waveform shaping unit 13.

[0056] Therefore, the transmission device 1 of the present embodiment has a function of generating an IQ data signal compensated for distortion by the first distortion compensation process of pre-correcting the error of the IQ signal point caused by the satellite repeater 2 of the actual satellite by providing the first distortion compensation unit 16 in the stage before the waveform shaping unit 13. As a result, in the downlink signal (broadcast wave signal) radiated from the satellite repeater 2 of the actual satellite, the shift and spread of the IQ signal point caused by the satellite repeater 2 of the actual satellite are canceled, so that the receiving device 3 side can converge to the ideal signal point, and the required C / N on the receiving device 3 side can be improved.

[0057] The waveform shaping unit 13 performs waveform shaping to remove unnecessary high-frequency components by applying a predetermined band-limiting filter process to the signal of the IQ data after the first distortion compensation obtained from the first distortion compensation unit 16 (including upsampled non-sample points), generates a signal of the IQ data after waveform shaping that has undergone the first distortion compensation process, and outputs it to the transmission signal generation unit 14. As the band-limiting filter, a digital filter having a generally root roll-off characteristic is generally used. In this embodiment, a root roll-off filter with a roll-off rate of 0.03 adopted in ISDB-S3 is used.

[0058] The second distortion compensation unit 17 uses a table file showing values that are inverse components of the input / output characteristics (AM / AM characteristic and AM / PM characteristic) of the high-power amplifier (HPA) 1a of the earth station shown in FIG. 6 for the signal of the IQ data after waveform shaping that has undergone the first distortion compensation obtained from the waveform shaping unit 13, and generates a signal of the IQ data that has been distortion-compensated by a second distortion compensation process for pre-correcting the error of the IQ signal points caused by the high-power amplifier (HPA) 1a of the earth station, and outputs it to the transmission signal generation unit 14.

[0059] Therefore, the transmission device 1 of this embodiment has a function of generating a signal of the IQ data that has been distortion-compensated by a second distortion compensation process for pre-correcting the error of the IQ signal points caused by the high-power amplifier (HPA) 1a of the earth station by providing the second distortion compensation unit 17 after the waveform shaping unit 13. As a result, not only the shift and spread of the IQ signal points caused by the high-power amplifier (HPA) 1a of the earth station are canceled, but also the spectral regrowth outside the Nyquist band in the uplink signal can be reduced.

[0060] The transmission signal generation unit 14 is a functional unit that generates a modulated wave signal by the predetermined modulation method for the signal of the IQ data that has been distortion-compensated by the second distortion compensation obtained from the second distortion compensation unit 17, and transmits it to the high-power amplifier (HPA) 1a of the earth station, and includes an orthogonal modulation unit 141, a DA (digital / analog) conversion unit 142, and a frequency conversion unit 143.

[0061] The quadrature modulation unit 141 generates a baseband IQ signal based on quadrature modulation processing using the predetermined modulation method for the IQ data signal after compensating for the transmission path distortion caused by both the satellite repeater 2 of the actual satellite obtained from the second distortion compensation unit 17 and the high power amplifier (HPA) 1a of the earth station before and after the waveform shaping unit 13, and outputs it to the DA conversion unit 142.

[0062] The DA conversion unit 142 performs digital / analog conversion processing on the baseband IQ signal obtained from the quadrature modulation unit 141 to generate a modulated wave signal, and outputs it to the frequency conversion unit 143.

[0063] The frequency conversion unit 143 frequency-converts the modulated wave signal obtained from the DA conversion unit 142 into a modulated wave signal in the radio frequency band of the uplink signal, and transmits it to the high power amplifier (HPA) of the earth station. For example, the radio frequency of the uplink signal in the satellite broadcast transmission system of ISDB-S3 is in the 17 GHz band.

[0064] (First Distortion Compensation Unit) FIG. 3 is a block diagram showing a schematic configuration of the first distortion compensation unit 16 in the transmission device 1 according to an embodiment of the present invention. An upsampling unit 167 corresponding to the upsampling unit 12 shown in FIG. 5 of the prior art is provided at the output unit of the first distortion compensation unit 16.

[0065] The first distortion compensation unit 16 is configured as a functional unit that performs a first distortion compensation process for pre-correcting transmission path distortion caused by the input / output characteristics of the TWTA in the satellite repeater 2 shown in FIG. 7 and the frequency response characteristics of the IMUX filter and the OMUX filter in the satellite repeater 2 shown in FIG. 8. Note that the first distortion compensation unit 16 may be provided either before or after the waveform shaping unit 13 in terms of compensating for the transmission path distortion caused by the satellite repeater 2 of the actual satellite. However, for the following reasons, it is necessary to provide it before the waveform shaping unit 13 in terms of operation. The reason is that the object of distortion compensation of the first distortion compensation unit 16 is the non-linearity of the satellite repeater 2, and the output stage has spectrum regrowth because the up-link signal transmitted by the transmission device 1 is corrected to have the inverse characteristic of the non-linearity, resulting in an up-link signal with unnecessary wave components remaining outside the band. By providing it before the waveform shaping unit 13, it becomes possible to up-link the signal with the unnecessary wave components outside the band sufficiently suppressed.

[0066] Hereinafter, more specifically, with reference to FIG. 3, the configuration of the first distortion compensation unit 16 will be described. The first distortion compensation unit 16 includes an upsampling unit 161, a waveform shaping unit 162, a pseudo satellite repeater 163, a waveform shaping unit 164, a downsampling unit 165, an IQ distortion compensation arithmetic unit 166, and an upsampling unit 167.

[0067] The upsampling unit 161 performs upsampling by a factor of two or more on the sample points of the IQ data signal obtained from the mapping unit 112 and outputs it to the waveform shaping unit 162.

[0068] The waveform shaping unit 162 is a digital filter having a root raised cosine filter characteristic with a roll-off rate of 0.03. It performs waveform shaping to remove unnecessary high-frequency components by performing predetermined band-limiting filter processing on the IQ data signal including upsampled non-sample points obtained from the upsampling unit 161, generates an IQ data signal after waveform shaping, and outputs it to the pseudo satellite repeater 163.

[0069] The pseudo satellite repeater 163 includes corresponding IMUX filter 1631, TWTA 1632, and OMUX filter 1633 as functional units that perform signal processing using table files approximating the input / output characteristics of the IMUX filter 21, TWTA 22, and OMUX filter 23 in the satellite repeater 2 of the actual satellite shown in FIG. 1, respectively. That is, the pseudo satellite repeater 163 generates a signal that pseudo-causes transmission path distortion due to the satellite repeater 2 by using a table file approximating the input / output characteristics of the satellite repeater 2 of the actual satellite for the waveform-shaped IQ data signal obtained from the waveform shaping unit 162, and outputs the signal to the waveform shaping unit 164. The input / output characteristics of this pseudo satellite repeater 163 are configured by table files used for digital signal processing. As a result, the pseudo satellite repeater 163 generates an IQ data signal having a signal point that pre-simulates the signal point deviation that may occur due to the satellite repeater 2 with respect to the ideal signal point of the IQ data after the mapping of the signal points of the digital signal to be transmitted.

[0070] The waveform shaping unit 164 is a digital filter having the same root raised cosine filter characteristic with a roll-off rate of 0.03 as the waveform shaping unit 162. In particular, the waveform shaping unit 164 has the role of removing unnecessary waves for the receiving side and theoretically making the inter-symbol interference at the sample points zero because the modulation signal passes through the waveform shaping unit 162 and the waveform shaping unit 164, and thus maintaining the roll-off characteristic when viewed from the entire transmission path.

[0071] The downsampling unit 165 performs a downsampling process on the IQ data signal that pseudo-causes the transmission path distortion due to the satellite repeater 2 after waveform shaping obtained from the waveform shaping unit 164, by thinning out the non-sample points by the upsampling unit 161 so as to correspond to the sample points of the original IQ data signal, and outputs it to the IQ distortion compensation arithmetic unit 166. For example, when the upsampling unit 161 performs 2-fold upsampling, the downsampling unit 165 thins out by 1 / 2. That is, considering the transmission system 1, the upsampling unit 161, the waveform shaping unit 162, the pseudo-satellite repeater 163, the waveform shaping unit 164, and the downsampling unit 165 up to form a pseudo-transmission path corresponding to the transmission path assumed between the uplink signal and the downlink signal.

[0072] The IQ distortion compensation arithmetic unit 166 is a functional unit that performs a first vector operation of subtracting the signal points of the corresponding original IQ data from the IQ signal points of the IQ data that pseudo-causes the transmission path distortion due to the satellite repeater 2 after downsampling obtained from the downsampling unit 165 to obtain an error vector, and performs a second vector operation of subtracting the error vector multiplied by a predetermined coefficient weight from the signal points of the original IQ data in order to use the inverse vector viewed from the ideal signal point as the correction vector for the error vector, and generates an IQ data signal that is distortion-compensated by the first distortion compensation process of upsampling. It has a delay unit 1661, a first vector operation unit 1662, an inverse characteristic coefficient unit 1663, and a second vector operation unit 1664.

[0073] The delay unit 1661 is a functional unit that adjusts the timing to synchronize between two signals: the signal of the IQ data that pseudo-causes the transmission path distortion due to the satellite repeater 2 after downsampling obtained from the downsampling unit 165, and the signal of the original IQ data obtained from the data signal generation unit 11. That is, the delay unit 1661 delays the signal of the original IQ data obtained from the data signal generation unit 11 by a delay amount D corresponding to the time required for the processing from the upsampling unit 161, the waveform shaping unit 162, the pseudo-satellite repeater 163, the waveform shaping unit 164, to the downsampling unit 165, and outputs it to the first vector operation unit 1662 and the second vector operation unit 1664 so as to synchronize between the two signals.

[0074] The first vector operation unit 1662 generates an error vector by performing a first vector operation of subtracting the signal point of the corresponding original IQ data from the IQ signal point of the IQ data that pseudo-causes the transmission path distortion due to the satellite repeater 2 after downsampling obtained from the downsampling unit 165, and outputs it to the inverse characteristic coefficient unit 1663.

[0075] The inverse characteristic coefficient unit 1663 multiplies the error vector obtained from the first vector operation unit 1662 by a predetermined coefficient weight and outputs it to the second vector operation unit 1664. For example, the coefficient weight may be 1 and the inverse characteristic coefficient unit 1663 may be omitted. However, in this embodiment, the inverse characteristic coefficient unit 1663 enables fine adjustment by multiplying the absolute value of the error vector by the coefficient weight, such as 0.95 or 1.05.

[0076] The second vector operation unit 1664 subtracts the error vector multiplied by the predetermined coefficient weight from the signal point of the corresponding original IQ data after delay adjustment obtained from the delay unit 1661 in order to use the inverse vector viewed from the ideal signal point as the correction vector for the error vector multiplied by the predetermined coefficient weight obtained from the inverse characteristic coefficient unit 1663, thereby generating a signal of the IQ data with distortion compensation and outputting it to the upsampling unit 167.

[0077] The upsampling unit 167 performs upsampling by a factor of two or more on the sample points of the signal of the distortion-compensated IQ data obtained from the second vector operation unit 1664 and outputs the result to the waveform shaping unit 13.

[0078] In this way, the transmission device 1 of this embodiment has a function of generating a signal of distortion-compensated IQ data by performing a first distortion compensation process that corrects in advance the error of the IQ signal points caused by the satellite repeater 2 of the actual satellite by providing the first distortion compensation unit 16 in the stage before the waveform shaping unit 13. As a result, in the downlink signal (broadcast wave signal) radiated from the satellite repeater 2 of the actual satellite, the shift and spread of the IQ signal points caused by the satellite repeater 2 of the actual satellite are canceled, so that the receiving device 3 side can converge to the ideal signal points, and the required C / N on the receiving device 3 side can be improved.

[0079] (Second Distortion Compensation Unit) As described above, the second distortion compensation unit 17 uses a table file showing values that are the inverse components of the input / output characteristics (AM / AM characteristics and AM / PM characteristics) of the high-power amplifier (HPA) 1a of the earth station shown in FIG. 6 for the signal of the IQ data after waveform shaping that has undergone the first distortion compensation process obtained from the waveform shaping unit 13, and generates a signal of distortion-compensated IQ data by performing a second distortion compensation process that corrects in advance the error of the IQ signal points caused by the high-power amplifier (HPA) 1a of the earth station, and outputs the result to the transmission signal generation unit 14.

[0080] In the second distortion compensation unit 17 according to this embodiment, it is configured to have a table file as shown in FIG. 4. The AM / AM characteristics and AM / PM characteristics for the second distortion compensation process in the second distortion compensation unit 17 shown in FIG. 4 are characteristics corrected to values that are the inverse components of the input / output characteristics (AM / AM characteristics and AM / PM characteristics) of the high-power amplifier (HPA) 1a of the earth station shown in FIG. 6. In FIG. 4, the AM / AM characteristics for the second distortion compensation process are those obtained by inverting the gain of the AM / AM characteristics of the high-power amplifier (HPA) 1a. Also, in FIG. 4, the AM / PM characteristics for the second distortion compensation process are those obtained by inverting the sign of the values of the AM / PM characteristics of the high-power amplifier (HPA) 1a. As a result of the second distortion compensation process in the second distortion compensation unit 17, the input / output characteristics of the high-power amplifier (HPA) 1a of the earth station including the second distortion compensation unit 17 are improved in linearity, and since the IQ data signals including non-sample points pass through the input / output characteristics, the spectral regrowth at the output stage of the high-power amplifier (HPA) 1a of the earth station is reduced, and the uplink signal can be transmitted. Note that although out-of-band spectral regrowth occurs in the output signal of the transmission device 1 due to the second distortion compensation unit 17, since it is wired-connected from the transmission device 1 to the high-power amplifier (HPA) 1a, it does not pose a problem. As a result, it is preferable that the spectral regrowth at the output stage of the high-power amplifier (HPA) 1a is reduced compared to when there is no compensation.

[0081] Note that the second distortion compensation unit 17 may be either before or after the waveform shaping unit 13 only in terms of compensating for in-band signal distortion caused by the high-power amplifier (HPA) 1a of the earth station. However, in order to reduce the out-of-band spectral regrowth of the high-power amplifier (HPA) 1a, it must be provided after the waveform shaping unit 13. Furthermore, since the latter stage of the waveform shaping unit 13 has a block configuration closer to the target transmission path (high-power amplifier (HPA) 1a), higher-precision distortion compensation can be expected compared to the former stage. Furthermore, if the high-power amplifier (HPA) 1a becomes an equivalent linear transmission path due to the second distortion compensation unit 17, the compensation accuracy of the first distortion compensation unit 16 for which the satellite repeater 2 is the compensation target also improves.

[0082] Therefore, the transmission device 1 of this embodiment has a function of generating an IQ data signal that is distortion-compensated by a second distortion compensation process that corrects in advance the error of the IQ signal points caused by the high-power amplifier (HPA) 1a of the earth station by providing the second distortion compensation unit 17 after the waveform shaping unit 13. As a result, not only the shift and spread of the IQ signal points caused by the high-power amplifier (HPA) 1a of the earth station are canceled, but also the spectral regrowth outside the Nyquist band in the uplink signal can be reduced.

[0083] (Summary) Here, the operations and effects of the present invention with respect to the prior art will be summarized and explained. As shown in FIG. 9, in the conventional transmission device 10A having a configuration in which the distortion compensation means (distortion compensation unit 15) is provided only in the front stage of the waveform shaping unit 13, since waveform shaping is performed after the distortion compensation by the distortion compensation unit 15, it was effective for reducing the distortion of the in-band IQ components of the satellite repeater 2. However, it was not possible to reduce the spectral regrowth outside the Nyquist band in the uplink signal with only the distortion compensation unit 15. Since the satellite repeater 2 has the OMUX filter 23, it is not necessary to reduce the spectral regrowth component of the TWTA 22 as DPD. Conversely, in a transmission device (not shown) having a configuration including only the second distortion compensation unit 17, since it affects the out-of-band uplink signal, it is not possible to actively perform distortion compensation for the satellite repeater 2 as a pre-process. Therefore, further contrivance is required to reduce the out-of-band spectral regrowth of the uplink signal while reducing the required C / N on the receiving side.

[0084] Therefore, by adopting a configuration in which individual distortion compensation means (the first distortion compensation unit 16 and the second distortion compensation unit 17) are provided before and after the waveform shaping unit 13 as in the transmission device 1 of the present embodiment, it is possible to reduce the spectral regrowth outside the Nyquist band in the uplink signal, which could not be solved by the conventional DPD (corresponding to a configuration having only the first distortion compensation unit 16), by the second distortion compensation unit 17. Further, according to the transmission device 1 of the present embodiment, since the first distortion compensation unit 16 can perform distortion compensation for the satellite repeater 2 in the same manner as in the conventional case without any adverse effects, the required C / N as the reception characteristic is also improved, and it is possible to reduce the spectral regrowth of the uplink signal and improve the reception performance. And according to the transmission device 1 of the present embodiment, since the characteristics of the broadcast transmission path in the first distortion compensation unit 16 and the second distortion compensation unit 17 can be sequentially updated by rewriting the table file in the process of simulating the characteristics of the broadcast transmission path, it has high versatility for various transmission systems and broadcast transmission paths without depending on the signal formats of various transmission systems.

[0085] Although the above-described embodiment has been described as a representative example, it is obvious to those skilled in the art that many changes and substitutions can be made within the spirit and scope of the present invention. For example, in the above-described example, in FIGS. 6 and 8, typical input / output characteristics have been illustrated and described based on the current high-power amplifier (HPA) 1a of the earth station and the satellite repeater 2 of the actual satellite, but the input / output characteristics of the high-power amplifier (HPA) 1a of the earth station and the satellite repeater 2 of the actual satellite used in actual operation may be applied. Also, although the first distortion compensation unit 16 and the second distortion compensation unit 17 in the embodiment of the present invention use, as an example, a distortion compensation method using the input / output characteristics of the transmission path, the individual compensation methods are not limited to this. The first distortion compensation unit 16 is a compensation method for the satellite repeater 2 (or a transmission path corresponding thereto), and the second distortion compensation unit 17 may be a compensation for the high-power amplifier (HPA) 1a (or a transmission path corresponding thereto). Therefore, the present invention should not be construed as being limited by the above-described embodiment, but is limited only by the scope of the claims.

Industrial Applicability

[0086] According to the present invention, it is possible to reduce the spectral regrowth of the uplink signal in satellite broadcasting and improve the reception performance, so it is useful for the application of the transmission system of satellite broadcasting.

Explanation of Signs

[0087] 1 Transmission device according to the present invention 1a High power amplifier (HPA) of the earth station 2 Satellite repeater 3, 3-1, 3-2, 3-n Receiving devices 10, 10A Transmission devices of the prior art 11 Data signal generation unit 12 Upsampling unit 13 Waveform shaping unit 14 Transmission signal generation unit 15 Distortion compensation unit 16 First distortion compensation unit 17 Second distortion compensation unit 21 Input multiplexer (IMUX) filter 22 Traveling wave tube amplifier (TWTA) 23 Output multiplexer (OMUX) filter 111 Pre-transmission processing unit 112 Mapping unit 141 Quadrature modulation unit 142 Digital / analog (DA) conversion unit 143 Frequency conversion unit 161 Upsampling unit 162 Waveform shaping unit 163 Pseudo satellite repeater 164 Waveform shaping unit 165 Downsampling unit 166 IQ distortion compensation arithmetic unit 167 Upsampling unit 1631 Functional unit for processing the approximate input / output characteristics of the IMUX filter 1632 Functional unit for processing the approximate input / output characteristics of the TWTA 1633 Functional unit for processing the approximate input / output characteristics of the OMUX filter 1661 Delay unit 1662 First vector operation unit 1663 Inverse characteristic coefficient unit 1664 Second vector operation unit

Claims

1. A transmitting device that transmits a digital signal toward a receiving device via a broadcast transmission path including a high-power amplifier of an earth station and a satellite repeater in a satellite broadcast transmission system, a data signal generation unit that inputs transmission data constituting the digital signal as a main signal, performs predetermined preprocessing including error correction encoding on the information bit sequence of the main signal to generate a signal of an encoded bit sequence, and performs mapping by a mapping table based on a predetermined modulation method to convert it into a signal of IQ data represented by a signal point sequence of an in-phase component and a quadrature phase component; a first distortion compensation unit that generates a signal of IQ data whose distortion is compensated by a first distortion compensation process for pre-compensating an error of an IQ signal point caused by the satellite repeater with respect to the signal of the IQ data; a waveform shaping unit that performs waveform shaping by performing predetermined band-limiting filter processing on the signal of the IQ data after the first distortion compensation process, and generates a signal of the IQ data after waveform shaping that has undergone the first distortion compensation process; a second distortion compensation unit that generates a signal of IQ data whose distortion is compensated by a second distortion compensation process for pre-compensating an error of an IQ signal point caused by the high-power amplifier of the earth station with respect to the signal of the IQ data after waveform shaping that has undergone the first distortion compensation process; a transmission signal generation unit that generates a modulated wave signal by the predetermined modulation method with respect to the signal of the IQ data whose distortion is compensated by the second distortion compensation process, and transmits it to the high-power amplifier of the earth station; A transmitting device characterized by comprising.

2. The first distortion compensation unit, as the first distortion compensation process, once performs waveform shaping on the signal of the IQ data obtained from the data signal generation unit in an upsampled state, generates a signal that pseudo-causes transmission path distortion due to the satellite repeater using a table file approximating the input / output characteristics of the satellite repeater, performs waveform shaping, and subtracts the corresponding original IQ data signal point from the IQ signal point obtained by downsampling so as to correspond to the original IQ data signal to perform a first vector operation to obtain an error vector. To use the inverse vector viewed from the ideal signal point of the error vector as a correction vector, a second vector operation is performed to subtract the error vector multiplied by a predetermined coefficient weight from the original IQ data signal point, and an upsampling process is performed to pre-correct the error of the IQ signal point due to the satellite repeater, thereby generating a distortion-compensated IQ data signal. The transmission device according to claim 1, characterized by having means for doing so.

3. The second distortion compensation unit, as the second distortion compensation process, pre-corrects the error of the IQ signal point due to the high-power amplifier of the earth station by using a table file indicating a value that is the inverse component of the input / output characteristics of the high-power amplifier of the earth station for the IQ data signal after waveform shaping that has undergone the first distortion compensation process, thereby generating a distortion-compensated IQ data signal. The transmission device according to claim 1 or 2, characterized by having means for doing so.

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