JP5538137B2 - Digital signal transmitter - Google Patents

Description

  The present invention relates to a digital signal transmitting apparatus that reduces distortion of required C / N due to a transmission path by performing distortion correction for each signal point on a transmission path and performing modulation.

  Of digital broadcasting of various standards currently in operation, using satellite broadcasting as an example, multiple broadcasters can transmit independent TS (transport stream) using a satellite repeater provided in the broadcasting satellite. Are multiplexed. Standards adopted in satellite digital broadcasting include DVB-S2, a transmission system for advanced broadband satellite broadcasting, and the like. Therefore, hereinafter, a description will be given of a generalized transmission apparatus that conforms to these standards.

  FIG. 1 is a block diagram showing a configuration of a transmission system via a satellite repeater provided in a broadcasting satellite. A main signal obtained by multiplexing video / audio / data broadcasting and the like is transmitted to the real satellite 2 by a digital modulation method specified by control information such as a TMCC signal from the transmission device 1. The satellite repeater of the real satellite 2 is an input multiplexer filter (hereinafter referred to as IMUX filter) 21, a traveling wave tube amplifier (hereinafter referred to as TWTA) 22, and an amplifier that is an input filter disposed in front of the amplifier. Output multiplexer filter (hereinafter referred to as OMUX filter) 23 and the like, and band extraction is performed for each channel from the broadcast wave signal received by IMUX filter 21 and gain control is performed by TWTA 22 Then, the unnecessary frequency component is suppressed by the OMUX filter 23, and broadcast wave signals for all the channels are synthesized by a subsequent synthesizer (not shown), and the receivers 3-1 to 3-N (N is one or more). A broadcast wave signal is transmitted toward a natural number.

  Even if various transmission controls are performed in the transmission device 1, the reception devices 3-1 to 3-N constantly monitor control information such as a TMCC signal transmitted together with the multiplexed broadcast wave signal. It is possible to switch the reception method and the like following.

  FIG. 2 is a block diagram showing only the configuration of the modulator 11 of the conventional transmission apparatus 1. The modulator 11 of the transmission apparatus 1 converts a serial bit string into parallel with respect to a data signal to be transmitted (hereinafter also simply referred to as a digital signal) to which predetermined encoding is applied and control information such as a TMCC signal is added. Serial / parallel converter (hereinafter referred to as S / P converter) 12, mapping section 13 for mapping for each predetermined modulation system, and orthogonal modulation section 14 for performing orthogonal modulation in accordance with each predetermined modulation system With.

  The signal point coordinates mapped to the signal points corresponding to the digital modulation method specified by the control information such as the TMCC signal by the mapping unit 13 are input to the quadrature modulation unit 14, and the quadrature modulation unit 14 converts the signal point coordinates into the signal point coordinates. Quadrature modulation is performed to generate a modulated wave signal. The modulated wave signal generated by the quadrature modulation unit 14 is uplinked toward the real satellite 2.

  The predetermined digital modulation scheme includes BPSK including π / 2 shift BPSK, QPSK including π / 4 shift QPSK, 8PSK, 16APSK, or 32APSK, and the mapping unit 13 is a mapper corresponding to these modulation schemes. Can be prepared.

  The function of the satellite repeater in the real satellite 2 shown in FIG. 1 will be further described. The IMUX filter 21 is a band-pass filter corresponding to each channel frequency, and can extract only a band component for one channel from the received broadcast wave signal. The TWTA 22 can further amplify the power of the extracted broadcast wave signal for one channel. The OMUX filter 23 is a band pass filter corresponding to each channel frequency, and can extract only a band component for one channel from the broadcast wave signal amplified by the TWTA 22 and suppress unnecessary frequency components.

  On the other hand, the TWTA 22 desirably performs power amplification processing so that the relationship between the input level and the output level is proportional. However, this input / output characteristic actually shows non-linearity in which the gain decreases as the input level increases, and at the same time, the phase of the output signal relative to the input signal also rotates. Accordingly, when the input level is gradually increased, the output level is increased up to a certain level, but when the input level is exceeded, the output level is decreased. The operating point immediately before such a decrease in output level is generally called the output saturation point. Further, the case where the input level is lowered by X [dB] from the output saturation point is called “input back-off X [dB]”. Similarly, the input level is narrowed and the output level is lowered by Y [dB]. The operation in the state is referred to as “output backoff Y [dB]”.

  Since the most efficient transmission is possible at the saturation point of TWTA 22, when using PSK modulation such as BPSK including π / 2 shift BPSK, QPSK including π / 4 shift QPSK, and 8PSK, a traveling wave tube amplifier (TWTA) The 22 input signals are automatically adjusted by a pre-attenuator or the like so that the input back-off is input at a level of 0 dB. On the other hand, in the case of APSK modulation such as 16APSK and 32APSK, since there are signal points having a plurality of amplitudes in the signal point arrangement, the required C / N is likely to deteriorate due to the nonlinear characteristics of the amplifier. For this reason, when these modulation methods are used, the input back-off for the input signal of the traveling wave tube amplifier (TWTA) 22 depends on the output back-off for each combination of the modulation method and the error correction code. It is automatically adjusted by a pre-attenuator or the like so that the power loss and the required C / N deterioration due to nonlinearity are input at a level that minimizes the sum.

  As described above, a modulator used in a conventional digital signal transmission apparatus has a signal point corresponding to a symbol for each information bit number that can be transmitted simultaneously in one symbol according to a modulation method. The carrier wave is modulated by the transmission signal points mapped so as to be fixed. In particular, multi-value amplitude phase modulation such as 32APSK requires more linearity with respect to signal distortion, and a broadcasting satellite needs to take a larger output back-off in order to operate the TWTA 22 to some extent (for example, Patent Document 1).

  On the other hand, ISDB-T, DVB-T, DVB-T2 and the like are standards adopted in terrestrial digital broadcasting.

  In these standards, a multiplexing method called OFDM (Orthogonal Frequency Division Multiplexing) is adopted. In OFDM, modulated waves such as 64QAM, which is a kind of QPSK and APSK, are multiplexed and transmitted on thousands of equally spaced carriers (see, for example, Non-Patent Document 1).

  FIG. 11 is a block diagram showing a configuration of a transmission apparatus using OFDM. The modulator 11 of the transmission apparatus 1 includes an S / P converter 12 that converts a serial bit string into parallel with respect to a digital signal, a mapping unit 13 that maps each predetermined modulation method, and each predetermined modulation. 2 is the same as the transmission apparatus shown in FIG. 2 in that it includes an orthogonal modulation unit 14 that performs orthogonal modulation according to the system, but S / P conversion units 151a and 151b, an inverse fast Fourier transform unit (hereinafter referred to as IFFT unit) And an OFDM converter 15 having parallel / serial converters (hereinafter referred to as P / S converters) 153a and 153b.

  Normally, a pilot signal, a transmission control signal, and a guard interval (not shown) are inserted in this block diagram, but the description is omitted here because it does not affect the following description.

  In FIG. 11, as a function of a general transmission apparatus that radiates radio waves by power amplification, an amplifier 16 that includes a filter 161, a power amplification unit 162, and a filter 163 in the output stage, and an antenna 17 are also shown. It is.

  Signal point coordinates mapped by a modulation method corresponding to a digital modulation method designated by control information such as a TMCC signal by the mapping unit 13 are allocated to a large number of OFDM carriers by the S / P conversion units 151a and 151b. Next, the IFFT unit 152 converts a large number of OFDM carriers into the same number of time axis signals. Further, the obtained time axis signals are converted into one time series signal by the P / S converters 153a and 153b. Thereafter, the signal is input to the quadrature modulation unit 14, and the quadrature modulation unit 14 performs quadrature modulation on the signal to generate a modulated wave signal. The modulated wave signal generated by the quadrature modulation unit 14 further suppresses an unnecessary frequency component by the filter 161, amplifies it to a predetermined power by the power amplification unit 162, suppresses the unnecessary frequency component by the filter 163, and Radio waves are emitted toward a receiver (not shown).

  The predetermined digital modulation scheme includes BPSK including π / 2 shift BPSK, QPSK including π / 4 shift QPSK, 8PSK, 16QAM, 32QAM, 64QAM, 128QAM, or 256QAM which is a kind of APSK, The mapping unit 13 can prepare a mapper corresponding to these modulation methods.

  Since a modulated wave that has been multiplexed by OFDM has a very high peak power with respect to the average power, this power amplifier is required to have extremely high linearity and is operated with a large back-off (for example, Non-Patent Document 2). reference).

Japanese Patent Publication No. 2008-199574 Edited by Japan Broadcasting Corporation, “NHK Digital Television Technical Textbook”, published by Japan Broadcasting Corporation, February 20, 2007, p.112 Transistor Technology March 2008 Special Issue, “RF World No. 1”, CQ Publishing, published March 1, 2008, p. 55

  In a conventional modulator, after passing through a satellite repeater, the signal point arrangement on the receiver side is shifted from the desired point due to nonlinear distortion of the traveling wave tube amplifier (TWTA), even if the signal bit arrangement is the same information bit. And spread on the orthogonal IQ plane. For this reason, in particular, in multi-value amplitude phase modulation, errors are likely to occur due to inter-symbol interference, resulting in an increase in required C / N and degradation in transmission quality. Further, in the case of multi-level amplitude phase modulation, the output power of the traveling wave tube amplifier (TWTA) is taken off, while the reception power is reduced, resulting in the required C / N degradation. In addition, since terrestrial digital broadcasting also employs OFDM, the amplifier needs to be operated with a large back-off.

  An object of the present invention is to reduce the spread of signal points on the IQ plane due to passage through a transmission line by correcting nonlinear distortion caused by a satellite repeater or the like on the modulator side of the transmission device in advance in view of the above-described problems. Another object of the present invention is to provide a digital signal transmission device that reduces the required C / N degradation amount and output back-off amount as much as possible, and reduces the deviation of signal point arrangement on the reception device side.

In order to solve the above-described problems, a transmitting apparatus according to the present invention is a transmitting apparatus that modulates a digital signal with a predetermined modulation scheme in order to transmit the digital signal to a receiving apparatus via a predetermined transmission path. A pseudo transmitter (for example, a pseudo satellite repeater or a pseudo amplifier) having characteristics approximate to those of the target device on the transmission line, and an IQ signal point of a digital signal output via the pseudo transmitter as an amplitude and The differential amplitude value and differential phase value of each of the differential amplitude value and the differential phase value, which are the differences between the amplitude value and phase value converted to phase and the ideal amplitude value and ideal phase value converted from the corresponding ideal IQ signal point to amplitude and phase, respectively The correction amplitude value and the correction phase value obtained by adding the ideal amplitude value and the ideal phase value of the ideal IQ signal point are calculated, and the correction signal obtained by converting the correction amplitude value and the correction phase value into the IQ signal point is generated. An amplitude phase calculating unit that, characterized in that it comprises a quadrature modulating means for quadrature modulating the correction signal.

The transmitting device according to the present invention is a transmitting device that modulates a digital signal with a predetermined modulation scheme in order to transmit the digital signal to the receiving device via the predetermined transmission path, A pseudo transmitter having characteristics approximating the characteristics of the target device, a vector of IQ signal points of a digital signal output via the pseudo transmitter, and an inverse vector of a difference vector between corresponding vectors of ideal IQ signal points In addition, vector calculation means for generating a first correction signal obtained by adding the vectors of the ideal IQ signal points, and converting IQ signal points of the digital signal output through the pseudo transmitter into amplitude and phase The code error of each of the amplitude error value and the phase error value, which is the difference between the measured amplitude value and phase value and the ideal amplitude value and ideal phase value obtained by converting the corresponding ideal IQ signal point into amplitude and phase. A correction amplitude value and a correction phase value obtained by adding the ideal amplitude value and ideal phase value of the ideal IQ signal point to the value are calculated, and the correction amplitude value and the correction phase value are converted into IQ signal points. Amplitude phase calculating means for generating the correction signal, switching control means for switching and outputting the first correction signal and the second correction signal in a time division manner, and the correction outputted by switching by the switching means And quadrature modulation means for performing quadrature modulation on the signal.

The transmitting device according to the present invention is a transmitting device that modulates a digital signal with a predetermined modulation scheme in order to transmit the digital signal to the receiving device via the predetermined transmission path, A pseudo transmitter having characteristics approximating those of the target device, and an inverse vector of a difference vector between a vector of IQ signal points of a digital signal output via the pseudo transmitter and a vector of corresponding ideal IQ signal points Vector calculation means for generating a first correction signal obtained by adding the vectors of the ideal IQ signal points; amplitude obtained by converting IQ signal points of the digital signal output through the pseudo transmitter into amplitude and phase The sign error value of each of the amplitude error value and the phase error value, which is the difference between the ideal amplitude value and the ideal phase value obtained by converting the corresponding ideal IQ signal point into the amplitude and phase. A second correction obtained by calculating a corrected amplitude value and a corrected phase value obtained by adding the ideal amplitude value and ideal phase value of the ideal IQ signal point, and converting the corrected amplitude value and the corrected phase value into an IQ signal point. A plurality of signal point converters arranged in series comprising amplitude phase calculation means for generating a signal, and switching control means for switching and outputting the first correction signal point and the second correction signal point in a time division manner A quadrature modulation means for quadrature-modulating the first correction signal or the second correction signal output by the signal point converter at the final stage of the plurality of signal point converters arranged in series. It is characterized by providing.

In addition, the transmission device according to the present invention is a transmission device that modulates the digital signal with a predetermined modulation scheme and performs OFDM multiplexing to transmit the digital signal to the reception device via a predetermined transmission path. A first OFDM converter that converts the frequency axis signal point sequence into a time axis OFDM signal, a pseudo transmitter having characteristics approximating the characteristics of the target device on the transmission path, and the time axis signal point sequence as a frequency axis. An OFDM inverse conversion unit for converting to an OFDM signal, a vector of IQ signal points of a digital signal output via the first OFDM conversion unit, the pseudo transmitter, and the OFDM inverse conversion unit, and a corresponding ideal IQ Vector operation means for generating a first correction signal obtained by adding the vector of the ideal IQ signal point to the inverse vector of the difference vector from the signal point vector; and the first O The amplitude value and phase value obtained by converting the IQ signal point of the digital signal output through the DM conversion unit, the pseudo transmitter, and the OFDM inverse conversion unit into the amplitude and phase, and the corresponding ideal IQ signal point as the amplitude and phase. The corrected amplitude value obtained by adding the ideal amplitude value and the ideal phase value of the ideal IQ signal point to the respective sign inversion values of the amplitude error value and the phase error value that are the difference between the ideal amplitude value converted into the phase and the ideal phase value. And an amplitude phase calculation means for calculating a correction phase value, generating a second correction signal obtained by converting the correction amplitude value and the correction phase value into an IQ signal point, the first correction signal, and the second correction signal. Switching control means for switching and outputting the correction signal in a time division manner, a second OFDM conversion section for converting the correction signal switched and outputted by the switching means into a time-axis OFDM signal, and the second OFDM Characterized in that it comprises a quadrature modulating means for quadrature modulating the OFDM signal converted by the section, the.

In addition, the transmission device according to the present invention is a transmission device that modulates the digital signal with a predetermined modulation scheme and performs OFDM multiplexing to transmit the digital signal to the reception device via a predetermined transmission path. A first OFDM converter for converting a frequency axis signal point sequence to a time axis OFDM signal, a pseudo transmitter having characteristics approximating the characteristics of the target device on the transmission path, and converting the time axis signal point sequence to a frequency axis OFDM signal An OFDM inverse transform unit for converting to the first OFDM transform unit, the pseudo transmitter, and a vector of IQ signal points of the digital signal output via the OFDM inverse transform unit, and a corresponding ideal IQ signal point Vector operation means for generating a first correction signal obtained by adding the vector of the ideal IQ signal point to the inverse vector of the difference vector from the vector; Unit, the pseudo transmitter, and the IQ signal point of the digital signal output via the OFDM inverse conversion unit, the amplitude value and the phase value converted into the amplitude and phase, and the corresponding ideal IQ signal point as the amplitude and phase A corrected amplitude value and correction by adding the ideal amplitude value and ideal phase value of the ideal IQ signal point to the sign inversion values of the amplitude error value and phase error value, which are the difference between the converted ideal amplitude value and ideal phase value. Amplitude phase calculation means for calculating a phase value and generating a second correction signal obtained by converting the correction amplitude value and the correction phase value into an IQ signal point, and the first correction signal and the second correction signal A plurality of signal point converters in which signal point converters are arranged in series, and a signal point conversion in the final stage of the plurality of signal point converters arranged in series Output by the instrument A second OFDM converter that converts the first correction signal or the second correction signal into a time-axis OFDM signal, and an orthogonal modulation unit that orthogonally modulates the OFDM signal converted by the second OFDM converter, It is characterized by providing.

  In the transmission apparatus according to the present invention, the switching control means may output the first correction signal when the amplitude of the ideal IQ signal point is equal to or smaller than a predetermined magnitude, and the amplitude of the ideal IQ signal point from a predetermined magnitude. In the case where the second correction signal is larger than the second correction signal, the second correction signal is switched and output in a time division manner.

  According to the present invention, the expected transmission path distortion is calculated in advance on the transmission side and corrected for each signal point. Therefore, the required C / N is required particularly in the case of multilevel amplitude phase modulation that is weak against the influence of nonlinear distortion. It is possible to greatly improve the deterioration of.

It is a block diagram which shows the structure of the transmission system via the satellite repeater with which the broadcasting satellite was equipped. It is a block diagram which shows only the structure of the modulator of the conventional generalized transmitter. It is a block diagram which shows only the structure of the modulator in the transmission apparatus of Example 1 by this invention. It is a figure explaining the 1st compensation calculation by this invention. It is a figure which shows the simulation result of the signal point arrangement | positioning in the transmission apparatus of Example 1 by this invention. It is a block diagram which shows only the structure of the modulator in the transmission apparatus of Example 2 by this invention. It is a figure explaining the 2nd compensation calculation by this invention. It is a figure which shows the simulation result of the signal point arrangement | positioning in the transmission apparatus of Example 2 by this invention. It is a block diagram which shows only the structure of the modulator in the transmission apparatus of Example 3 by this invention. It is a figure which shows the simulation result of the signal point arrangement | positioning in the transmission apparatus of Example 3 by this invention. It is a block diagram which shows the structure of the conventional generalized OFDM transmitter. It is a block diagram which shows the structure of the transmission apparatus of Example 4 by this invention.

  First, the transmission apparatus according to the first embodiment of the present invention will be described. In the drawings, the same components will be described with the same reference numerals.

  FIG. 3 is a block diagram showing only the configuration of the modulator in the transmission apparatus according to the first embodiment of the present invention (as described above, a generalized transmission apparatus compliant with various standards). The transmission apparatus 1 according to the first embodiment is a transmission apparatus applicable to the transmission system via the satellite repeater provided in the broadcast satellite shown in FIG. 1, and transmits a broadcast wave signal to the existing broadcast satellite. Can do. Further, it can be incorporated into a transmission system independently of another existing transmission apparatus. Therefore, the transmission apparatus 1 according to the first embodiment can be compliant with a standard adopted in digital broadcasting, for example, a transmission system for advanced broadband satellite digital broadcasting, DVB-S2, or the like. Therefore, in order to transmit the digital signal to the receiving device 3-N via the satellite repeater of the real satellite 2, the transmitting device 1 according to the first embodiment modulates the digital signal with a predetermined modulation method. Configured as

  As illustrated in FIG. 3, the modulator 11 in the transmission device 1 according to the first embodiment is configured to transmit a serial bit string of 1 bit to several bits with respect to a digital signal to be transmitted (an unmodulated signal subjected to predetermined encoding). S / P converter 12 for converting into parallel bit strings, mapping unit 13 for mapping for each predetermined modulation method, signal point converter 18, and orthogonal modulation for applying orthogonal modulation according to each predetermined modulation method Part 14. Here, the S / P conversion unit 12, the mapping unit 13, and the orthogonal modulation unit 14 function in the same manner as that of the conventional general transmission apparatus shown in FIG.

  The signal point converter 18 includes a pseudo satellite repeater 19 and a compensation calculation unit 20. The compensation calculation unit 20 includes a delay unit 201, IQ / amplitude phase conversion units 202 and 204, and an amplitude phase doubling unit 203. And an amplitude phase addition unit 205 and an amplitude phase / IQ conversion unit 206.

  The pseudo-satellite repeater 19 has characteristics that approximate the frequency characteristics and nonlinear characteristics of the phase and amplitude of the satellite repeater of the real satellite 2 shown in FIG. 1, that is, includes an IMUX filter 191, a TWTA 192, and an OMUX filter 193. The IMUX filter 191 performs band extraction for each channel from the digital signal input through the mapping unit 13, performs gain control by the TWTA 192, and suppresses unnecessary frequency components by the OMUX filter 193. As a result, the pseudo satellite repeater 19 simulates the signal point deviation that may occur by the satellite repeater of the real satellite 2 with respect to the ideal signal point arrangement after mapping the signal points of the digital signal to be transmitted. An IQ signal having is output. In the following description, an ideal signal point arrangement after mapping of signal points of a digital signal to be transmitted is referred to as an ideal IQ signal point, and an ideal signal mapped to the ideal IQ signal point is referred to as an ideal IQ signal.

  The delay unit 201 adjusts the timing in order to synchronize the two systems of signals input to the amplitude / phase addition unit 205.

  The IQ / amplitude phase conversion unit 202 outputs a value obtained by converting the ideal IQ signal input from the delay unit 201 into an amplitude and a phase. The IQ / amplitude phase conversion unit 204 outputs a value obtained by converting the IQ signal after passing through the pseudo satellite repeater 19 into an amplitude and a phase.

  The amplitude phase doubling unit 203 outputs a value obtained by doubling the amplitude value and the phase value input from the IQ / amplitude phase conversion unit 202, respectively.

  The amplitude phase adding unit 205 subtracts the amplitude value and the phase value input from the amplitude phase doubling unit 203 by the amplitude value and the phase value input from the IQ / amplitude phase converting unit 204, respectively. Output. The calculation process including the amplitude phase doubling unit 203 includes the amplitude value and phase value of the IQ signal point of the digital signal output from the pseudo satellite repeater 19, and the ideal amplitude value and ideal phase of the corresponding ideal IQ signal point. After obtaining the difference from the value as an amplitude error value and a phase error value for each signal point, each of the sign inversion values (sign inversion amplitude error value and sign inversion phase error value) has an ideal amplitude value of the ideal IQ signal point and This is the same operation as calculating a corrected amplitude value and a corrected phase value obtained by adding the ideal phase value. In addition, one calculation of the amplitude error value and the phase error value can be omitted, and the calculation can be simplified.

  The amplitude phase / IQ conversion unit 206 converts the corrected amplitude value and the corrected phase value input from the amplitude phase addition unit 205 into IQ signal points, and outputs a corrected signal (correction signal). In the following description, compensation by the delay unit 201, IQ / amplitude phase conversion units 202 and 204, amplitude phase doubling unit 203, amplitude phase addition unit 205, and amplitude phase / IQ signal conversion unit 206 is referred to as amplitude phase calculation compensation. .

  The quadrature modulation unit 14 performs quadrature modulation on the correction signal input from the compensation calculation unit 20 according to a predetermined modulation method. The predetermined modulation schemes here include BPSK including π / 2 shift BPSK, QPSK including π / 4 shift QPSK, 8PSK, 16APSK, or 32APSK.

  Hereinafter, the operation of the transmission apparatus according to the first embodiment will be described in more detail.

  The modulator 11 in the transmission apparatus 1 according to the first embodiment performs serial / parallel conversion of the input digital signal into the number of bits that can be transmitted per symbol by the modulation scheme used for transmission by the S / P converter 12 and performs mapping. The unit 13 performs a mapping process for converting the converted signal into an I signal amplitude and a Q signal amplitude.

  Next, the mapped signal is divided into two, and one of the signals is passed through the pseudo satellite repeater 19 that simulates the characteristics of the satellite repeater of the real satellite 2. Here, the amplitude characteristic and group delay characteristic with respect to the frequency of the IMUX filter 191 and the OMUX filter 193 in the pseudo satellite repeater 19 and the AM-AM characteristic and AM-PM characteristic of the TWTA 192 are the characteristics of the satellite repeater of the real satellite 2. It is set so as to approximate, and is preferably set to a value at the time of designing the actual satellite 2 or equivalent to a set value during operation of the satellite repeater of the actual satellite 2.

  The pseudo-satellite repeater 19 may be a model that simulates the characteristics of the satellite repeater of the real satellite 2, and is not strictly required to be identical to the characteristics of the satellite repeater of the real satellite 2. Not too long. The same applies to the amplifier operating point. Therefore, as long as it has the same function as the IMUX filter 191, TWTA 192, and OMUX filter 193, it can be configured in any manner, for example, stores a lookup table for amplifying and converting a corresponding digital value signal instead of the TWTA 192. It is also possible to configure the memory. Further, the IMUX filter 191 and the OMUX filter 193 can be configured by digital filters. Apart from the pseudo-satellite repeater 19, the satellite broadcast transmitter and receiver are usually provided with a digital filter (route roll-off filter) in which roll-off filters are routed, and the effects of these are also simulated. It is also possible to simulate the characteristics of the root roll-off filter of the transmission / reception apparatus by cascading the IMUX filter 191 and the OMUX filter 193, respectively.

  The mapped signal is also input to the delay unit 201, adjusts the timing with the signal passed through the pseudo-satellite repeater 19, converts the ideal IQ signal into amplitude and phase by the IQ / amplitude phase conversion unit 202, The amplitude and phase are each doubled by the phase doubler 203. Then, the amplitude phase addition unit 205 subtracts the output amplitude value and phase value of the amplitude phase doubling unit 203 by the amplitude value and phase value after passing through the pseudo satellite repeater 19, and subtracts by the amplitude phase / IQ conversion unit 206. The obtained amplitude value and phase value are converted into IQ signals. Through such processing, amplitude and phase shifts (difference values) with respect to the ideal IQ signal point output from the pseudo-satellite repeater 19 are obtained for each signal point, and the sign inversion amplitude value and the sign inversion phase value are determined as the ideal IQ signal point. The deviation due to the pseudo satellite repeater 19 is corrected by adding to the ideal amplitude value and ideal phase value of the IQ signal. The corrected IQ signal output from the amplitude phase / IQ conversion unit 206 is corrected by the power normalization unit (not shown) so as not to affect the subsequent processing of the quadrature modulation unit 14 and the subsequent IQ. The amplitudes of all signal points are adjusted by a constant multiple so that the average power of the signal points becomes the same value as the average power of the original ideal IQ signal point.

  FIG. 4 is a diagram for explaining amplitude phase calculation compensation by the modulator 11 according to the first embodiment. White circles in the figure indicate ideal IQ signal points when the modulation method is 32APSK. The signal point a is an IQ signal point of the signal output from the mapping unit 13, and is arranged at any signal point on the ideal IQ signal point. The signal point b is an IQ signal point of the signal that has passed through the pseudo satellite repeater 19, and the deviation from the signal point a is represented by an amplitude error value ΔR that is an amplitude difference and a phase error value Δθ that is a phase difference. be able to. The signal point c is an IQ signal point of the signal after the amplitude phase calculation compensation, and is the sign inverted value of the amplitude error value ΔR of the signal point b with respect to the signal point a to the ideal amplitude value and ideal phase value of the signal point a. It is arranged at a position where a sign inversion amplitude error value -ΔR and a sign inversion phase error value -Δθ which is a sign inversion value of the phase error value Δθ of the signal point b with respect to the signal point a are added.

  The quadrature modulation unit 14 performs quadrature modulation on the correction signal at the corrected signal point after the amplitude phase calculation.

  FIG. 5 is a diagram illustrating a simulation result of signal point arrangement during 32APSK modulation in the transmission device 1 according to the first embodiment of the present invention. FIG. 5A shows the signal point arrangement of the signal that has passed through the satellite repeater, and the required C / N + OBO was 27.02 db. Here, the output back-off OBO (output ratio at the time of modulated wave output to saturation output at the time of non-modulation at the output of the OMUX filter) was 2.5 dB. On the other hand, FIG. 5B shows an IQ equivalent to that obtained when demodulating the signal modulated by the IQ signal point corrected by the amplitude phase calculation for all signal point arrangements through the satellite repeater in the actual satellite 2. The mapping of the IQ signal point after passing through the pseudo satellite repeater 19 as the signal point arrangement is shown, and the required C / N + OBO has been improved to 17.95 dB.

  As described above, according to the transmission device 1 of the first embodiment, it is possible to transmit a broadcast wave signal with improved degradation of required C / N.

  Next, a transmission apparatus according to the second embodiment of the present invention will be described. In the drawings, the same components will be described with the same reference numerals.

  FIG. 6 is a block diagram illustrating only the configuration of the modulator in the transmission apparatus according to the second embodiment of the present invention. As illustrated in FIG. 6, the modulator 11 in the transmission device 1 according to the second embodiment includes an S / P conversion unit 12, a mapping unit 13, a signal point converter 18, and an orthogonal modulation unit 14. Compared with the first modulator 11, the configuration of the signal point converter 18 is different.

  The signal point converter 18 includes a pseudo satellite repeater 19 and a compensation calculation unit 20. The compensation calculation unit 20 includes an output signal switching unit 207, delay units 201 and 208, an IQ / amplitude phase conversion unit 202, and 204, amplitude phase doubling unit 203, amplitude phase adding unit 205, amplitude phase / IQ converting unit 206, IQ signal doubling unit 209, vector adding unit 210, input signal switching unit 211, and switching control Unit 212.

  The output signal switching unit 207 switches whether the signal input from the mapping unit 13 is output to the delay unit 208 or the delay unit 201 in a time division manner for each signal point. When output to the delay unit 208, compensation by IQ signal vector calculation is performed in the subsequent processing, and when output to the delay unit 201, compensation by amplitude phase calculation is performed in the subsequent processing.

  The delay unit 208 adjusts the timing in order to synchronize the two systems of signals input to the vector addition unit 210.

  The IQ signal doubler 209 outputs a signal obtained by doubling the I signal and the Q signal input from the delay unit 208, respectively.

  The vector adder 210 has a correction signal having a correction vector obtained by subtracting the IQ signal vector input from the pseudo satellite repeater 19 from the signal vector of the IQ signal input from the IQ signal doubler 209 for each signal point. Is output. The calculation process including the IQ signal doubling unit 209 calculates the difference vector between the IQ signal point vector of the digital signal output from the pseudo satellite repeater 19 and the corresponding ideal IQ signal point vector for each signal point. This is the same operation as calculating the correction vector obtained by adding the ideal IQ signal point vector to the inverse vector of the difference vector. In addition, one computation of the difference vector can be omitted, and the computation can be simplified. In the following description, compensation by the delay unit 208, the IQ signal doubler 209, and the vector adder 210 is referred to as IQ signal vector operation compensation.

  The input signal switching unit 211 outputs as one output signal by input time division switching.

  The switching control unit 212 performs switching control and synchronization control of the output signal switching unit 207 and the input signal switching unit 211. The switching control function enables selective switching of a desired compensation method (IQ signal vector calculation compensation or amplitude phase calculation compensation) according to the signal point arrangement.

  Hereinafter, the operation of the transmission apparatus according to the second embodiment will be described in more detail.

  The modulator 11 in the transmission apparatus 1 according to the second embodiment uses the S / P converter 12 to serial / parallel convert the input digital signal into the number of bits that can be transmitted per symbol by the modulation method used for transmission, and perform mapping. The unit 13 performs a mapping process for converting the converted signal into an I signal amplitude and a Q signal amplitude.

  Next, the signal mapped by the mapping unit 13 is divided into two, one of which is input to the pseudo satellite repeater 19 and the other signal is input to the output signal switching unit 207. In the OMUX filter 193, the amplitudes of all signal points are multiplied by a constant so that the average power of the IQ signal points output from the pseudo satellite repeater 19 is equal to the average power of the IQ signal points output from the mapping unit 13. Adjust and output.

  When a signal is input from the mapping unit 13 to the output signal switching unit 207, the switching control unit 212 outputs to the delay unit 208 or the delay unit 201 for each signal point according to a predetermined switching method. Switching, that is, whether the compensation method is IQ signal vector calculation compensation or amplitude phase calculation compensation. As the switching method, for example, the required C / N by both compensations is obtained in advance by simulation or the like, and switching is performed so as to select a compensation method that reduces the required C / N for each signal point based on the simulation result. Alternatively, if the amplitude of the ideal IQ signal point after mapping is equal to or smaller than a predetermined magnitude, the IQ signal vector calculation compensation is selected, and if the amplitude of the ideal IQ signal point is smaller than the predetermined magnitude, the amplitude phase calculation compensation is selected. Switch to select. For example, in the case of 32APSK where the signal points are arranged on a concentric circle of 3 amplitudes, amplitude phase calculation compensation is performed on the signal points arranged on the outermost circle having the largest amplitude, and arranged on the remaining 2 circles. IQ signal vector operation compensation is performed for the signal points to be processed.

  When switching the selection of the plurality of compensation methods to time division, it is necessary to synchronize the division (output signal switching unit 207) and the synthesis (input signal switching unit 211), so the switching control unit 212 performs the control. Next, depending on the switching, IQ signal vector operation compensation by the delay unit 208, the IQ signal doubler unit 209, and the vector adder unit 210, or the delay unit 201, the IQ / amplitude phase conversion unit, for each signal point. 202 and 204, amplitude phase doubling unit 203, amplitude phase adding unit 205, and amplitude phase / IQ signal converting unit 206 perform amplitude phase calculation compensation. Note that the input signal switching unit 211 is configured so that the average power of the corrected IQ signal point is equal to the average power of the original ideal IQ signal point so as not to affect the subsequent processing of the quadrature modulation unit 14. The amplitude of all signal points is adjusted by a constant and output.

  FIG. 7 is a diagram for explaining IQ signal vector operation compensation by the modulator 11 according to the second embodiment. White circles in the figure indicate ideal IQ signal points when the modulation method is 32APSK. The signal point a is an IQ signal point of the signal output from the mapping unit 13 and is arranged on the ideal IQ signal point. The signal point b is an IQ signal point of the signal that has passed through the pseudo-satellite repeater 19, and a deviation from the signal point a can be represented by a difference vector v. The signal point c is an IQ signal point of the signal after the IQ signal vector calculation compensation, and is arranged at a position obtained by adding the inverse vector −v of the difference vector v to the signal vector of the signal point a.

  FIG. 8 is a diagram illustrating a simulation result of signal point arrangement during 32APSK modulation in the transmission device 1 according to the second embodiment of the present invention. FIG. 8A shows the signal point arrangement of the signal that has passed through the satellite repeater, and the required C / N + OBO was 27.02 db. FIG. 8B shows a case where a signal modulated by an IQ signal point corrected by performing only IQ signal vector operation compensation on all signal point arrangements is demodulated through a satellite repeater in the actual satellite 2. The IQ signal point mapping after passing through the pseudo satellite repeater 19 with the equivalent IQ signal point arrangement is shown, and the required C / N + OBO was 17.69 dB. In FIG. 8C, switching control by the switching control unit 212 is performed, IQ signal vector calculation compensation is performed on the signal point arrangement on the two inner circles, and amplitude phase calculation compensation is performed on the signal point arrangement on the outermost circle. The IQ signal point after passing through the pseudo-satellite repeater 19 has the same IQ signal point arrangement as that at the time of demodulation when the signal modulated by the corrected IQ signal point is passed through the satellite repeater in the real satellite 2. The mapping shows the required C / N + OBO improved to 17.49 dB.

  As described above, according to the transmission apparatus 1 of the second embodiment, the broadcast wave signal with improved deterioration of the required C / N is transmitted by switching and applying the IQ signal vector calculation compensation and the amplitude phase calculation compensation. Can do.

  Next, a transmission device according to a third embodiment of the present invention will be described. In the drawings, the same components will be described with the same reference numerals.

  FIG. 9 is a block diagram showing only the configuration of the modulator in the transmission apparatus 1 according to the third embodiment of the present invention. The transmission apparatus 1 according to the third embodiment is an apparatus configured to further improve the correction accuracy in the transmission apparatus according to the second embodiment described above. That is, the pseudo-satellite repeater 19 and the compensation calculation unit 20 in the transmission apparatus of the second embodiment are used as a set of signal point converters 18 and include a plurality of signal point converters arranged in series. Then, quadrature modulation is performed at the signal points obtained through the last-stage signal point converters arranged in series.

  The IQ vector operation compensation in the signal point converter 18-n (n> 1) other than the signal point converter 18-1 is an IQ signal that has passed through the pseudo satellite repeater 19 from a value obtained by doubling the vector of the ideal IQ signal point. Instead of subtracting the point vector, the IQ signal point vector that has passed through the pseudo-satellite repeater 19 from the sum of the ideal IQ signal point vector and the IQ signal point vector obtained through the previous signal point converter Therefore, the IQ signal doubler 209 is not necessary. Similarly, the amplitude / phase calculation compensation in the signal point converter 18-n (n> 1) is obtained by doubling the amplitude and phase of the ideal IQ signal point, and the amplitude and IQ signal point passing through the pseudo-satellite repeater 19. Instead of subtracting the phase, the IQ signal point that has passed through the pseudo-satellite repeater 19 from the sum of the amplitude and phase of the ideal IQ signal point and the amplitude and phase of the IQ signal point obtained through the previous signal point converter. Therefore, the amplitude / phase doubling unit 203 is not necessary, and the IQ / amplitude / phase conversion unit 213 is newly required.

  As shown in FIG. 9, the serial arrangement of the signal point converter 18 inputs the output signal of the input signal switching unit 211 at the preceding stage to the IMUX filter 191, the vector adding unit 210, and the IQ / amplitude / phase converting unit 213. The ideal IQ signal output from the mapping unit 13 is input to the output signal switching unit 207 of each signal point converter 18. Note that the input signal switching unit 211-1 at the first stage has the corrected average power of the IQ signal point as the average power of the original ideal IQ signal point so as not to affect the processing after the subsequent quadrature modulation unit 14. The input signal switching unit 211-n (n> 1) in the second stage and thereafter is a compensation signal after passing through the nonlinear transmission path. Therefore, it is not always necessary to fully normalize the power.

  In the transmission apparatus 1 according to the third embodiment, a set of signal point converters 18-n (n is a natural number of 1 or more) functions in the same manner. In FIG. 9, the IMUX filter 191-1 and 191-2, TWTA 192-1 and 192-2, delay units 201-1, 201-2, 208-1, and 208-2, OMUX filters 193-1 and 193-2, and IQ / amplitude phase conversion unit 202-1, 202-2, 213, 204-1 and 204-2, amplitude phase doubling unit 203, amplitude phase adding units 205-1 and 205-2, amplitude phase / IQ converting unit 206-1 and 206-2, output signal switching units 207-1 and 207-2, switching control units 212-1 and 212-2, input signal switching units 211-1 and 211-2, IQ signal doubling unit 209, , Vector addition It is shown as 210-1 and 210-2. The signal point converter 18-n includes the IMUX filter 191, the TWTA 192, the OMUX filter 193, the delay units 201 and 208, the IQ / amplitude phase conversion units 202 and 204, and the amplitude phase in the transmission apparatus according to the second embodiment. A doubler 203, an amplitude phase adder 205, an amplitude phase / IQ converter 206, an output signal switcher 207, a switch controller 212, an input signal switcher 211, an IQ signal doubler 209, A function corresponding to the vector adder 210 is provided.

  FIG. 10 is a schematic diagram illustrating an example of a simulation calculation result in the transmission apparatus 1 according to the third embodiment with respect to 32APSK modulation. FIG. 10A shows the mapping of ideal IQ signal points in FIG. 9A shown in FIG. Accordingly, it is desirable that the 32 APSK modulated signal point originally reaches the receiving device with this signal point arrangement.

FIG. 10 (b), that Do the same IQ constellation and during the time of demodulation passed through a satellite repeater in the actual satellite 2, after passing through the pseudo-satellite repeater 19 in the illustrated B shown in FIG. 9 IQ Signal point mapping is shown. This is because when the ideal IQ signal point is orthogonally modulated and passed through the satellite repeater, it is affected by the band limitation by the IMUX filter, the nonlinear characteristic by the TWTA, and the band limitation by the OMUX filter. It can be seen that the equivalent reception C / N is greatly degraded when the satellite repeater is passed through. According to the simulation results, the required C / N + OBO at this time was 27.02 dB.

  FIG. 10C shows a mapping of IQ signal points at the time of pre-compensation obtained by one compensation calculation in FIG. 9C shown in FIG.

  FIG. 10D shows an IQ equivalent to that at the time of demodulation in which the signal modulated by the IQ signal point corrected by one compensation calculation in FIG. 9D shown in FIG. 9 is passed through the satellite repeater in the real satellite 2. The IQ signal point mapping after passing through the pseudo satellite repeater 19 that is the signal point arrangement is shown. It can be seen that the degradation of equivalent C / N is improved as compared with FIG. According to the simulation results, the required C / N + OBO was improved to 17.49 dB.

  FIG. 10E shows the mapping of IQ signal points at the time of pre-compensation obtained by the two compensation operations in FIG. E shown in FIG.

  FIG. 10 (f) shows an IQ signal equivalent to that at the time of demodulation in which the signal modulated by the IQ signal point corrected by the twice compensation calculation in F shown in FIG. 9 is passed through the satellite repeater in the actual satellite 2. The mapping of the IQ signal point after passing through the pseudo satellite repeater 19 in the point arrangement is shown. Compared to FIG. 10D, it can be seen that the deterioration of the equivalent C / N is further improved. According to the simulation results, the required C / N + OBO was improved to 17.30 dB.

  Thus, according to the transmission device 1 of the third embodiment, further required C / N + OBO can be improved by a plurality of distortion correction calculations.

  Next, a transmission device according to a fourth embodiment of the present invention will be described. In the drawings, the same components will be described with the same reference numerals.

  FIG. 12 is a block diagram illustrating a configuration of the transmission apparatus according to the fourth embodiment of the present invention. The transmission apparatus 1 according to the fourth embodiment is a transmission apparatus applicable to the above-described transmission system using OFDM shown in FIG. 11, and can transmit a broadcast wave signal to an existing broadcast receiver. Further, it can be incorporated into a transmission system independently of another existing transmission apparatus. Therefore, the transmission apparatus 1 according to the fourth embodiment can be compliant with standards adopted in digital broadcasting, for example, ISDB-T, DVB-T, DVB-T2, and the like. Therefore, the transmission apparatus 1 according to the fourth embodiment is configured as a transmission apparatus that modulates the digital signal with a predetermined modulation method in order to transmit the digital signal to a reception apparatus (not illustrated).

  As illustrated in FIG. 12, the modulator 11 in the transmission device 1 according to the fourth embodiment converts a serial bit string of 1 bit to several bits with respect to a digital signal to be transmitted (pre-modulation signal subjected to predetermined encoding). S / P conversion unit 12 for converting into parallel bit strings, mapping unit 13 for mapping for each predetermined modulation method, signal point converter 18, OFDM conversion unit 15, orthogonal modulation unit 14 for performing orthogonal modulation, Is provided. Here, the S / P conversion unit 12, the mapping unit 13, the OFDM conversion unit 15, and the orthogonal modulation unit 14 function in the same manner as that of the conventional general transmission device shown in FIG.

  The signal point converter 18 includes a compensation calculation unit 20, an OFDM conversion unit 30, a pseudo amplifier 31, an OFDM inverse conversion unit 32, and a compensation calculation unit 20. The compensation calculation unit 20 includes a delay unit 201 and 208, an IQ / amplitude phase conversion unit 202 and 204, an amplitude phase doubling unit 203, an amplitude phase addition unit 205, an amplitude phase / IQ conversion unit 206, and an output signal. A switching unit 207, an IQ signal doubling unit 209, a vector adding unit 210, an input signal switching unit 211, and a switching control unit 212 are provided. The OFDM conversion unit 30 includes S / P conversion units 301a and 301b, an IFFT unit 302, and P / S conversion units 303a and 303b. The pseudo amplifier 31 includes a filter unit 311, a power amplification unit 312, and a filter unit 313. The OFDM inverse conversion unit 32 includes S / P conversion units 321a and 321b, a fast Fourier transform (hereinafter referred to as FFT unit) unit 322, and P / S conversion units 323a and 323b.

  The OFDM conversion unit 30 distributes the ideal IQ signal input from the mapping unit 13 to the same number as the OFDM carrier by the S / P conversion units 301a and 301b, and converts the ideal IQ signal to a time axis signal by the IFFT unit 302. Thereafter, the P / S converters 303a and 303b convert the obtained time axis signal into one time series signal.

  The pseudo-amplifier 31 has characteristics approximate to the frequency characteristics and nonlinear characteristics of the phase and amplitude in the amplifier 16 shown in FIG. 11, suppresses unnecessary frequency components by the filter 311, and amplifies the predetermined power by the power amplifier 312. Then, unnecessary frequency components are suppressed by the filter 313. As a result, the pseudo-amplifier 31 is multiplexed with OFDM having a signal point that simulates the deviation of the signal point that can be generated by the amplifier 16 with respect to the ideal IQ signal point after mapping the signal point of the digital signal to be transmitted. Output IQ signal of time axis signal.

  The OFDM inverse conversion unit 32 distributes the signal input from the pseudo-amplifier 31 to the same number as the OFDM carrier by the S / P conversion units 321a and 321b, and converts the signal to the frequency axis signal by the FFT unit 322. Thereafter, the P / S converters 323a and 323b convert the obtained frequency axis signal into one signal series.

  The output signal switching unit 207 outputs the input signal to the delay unit 208 in time division for each signal point in order to perform compensation by IQ signal vector calculation, or to perform compensation by amplitude phase calculation. The output is switched to 201.

  The delay unit 201 adjusts the timing in order to synchronize the two systems of signals input to the amplitude / phase addition unit 205.

  The IQ / amplitude phase conversion unit 202 outputs a value obtained by converting the ideal IQ signal input from the delay unit 201 into an amplitude and a phase, and the IQ / amplitude phase conversion unit 204 amplitudes the IQ signal after passing through the pseudo amplifier 31. And the value converted into the phase is output.

  The amplitude phase doubling unit 203 outputs a value obtained by doubling the amplitude value and the phase value input from the IQ / amplitude phase conversion unit 202, respectively.

  The amplitude phase adding unit 205 subtracts the amplitude value and the phase value input from the amplitude phase doubling unit 203 by the amplitude value and the phase value input from the IQ / amplitude phase converting unit 204, respectively. Output. The calculation process including the amplitude phase doubling unit 203 includes the amplitude value and phase value of the IQ signal point of the digital signal output from the pseudo-amplifier 31, and the ideal amplitude value and ideal phase value of the corresponding ideal IQ signal point. Is obtained for each signal point as an amplitude error value and a phase error value, and then the ideal amplitude value and ideal phase of the ideal IQ signal point are obtained for each sign inversion value (sign inversion amplitude error value and sign inversion phase error value). This is the same operation as calculating a corrected amplitude value and a corrected phase value obtained by adding the values. In addition, one calculation of the amplitude error and the phase error can be omitted, and the calculation can be simplified.

  The amplitude phase / IQ conversion unit 206 converts the amplitude value and the phase value input from the amplitude phase addition unit 205 into IQ signal points, and outputs a correction signal.

  The delay unit 208 adjusts the timing in order to synchronize the two systems of signals input to the vector addition unit 210.

  The IQ signal doubler 209 outputs a signal obtained by doubling the I signal and the Q signal input from the delay unit 208, respectively.

  The vector adder 210 outputs a correction signal having a correction vector obtained by subtracting the vector of the IQ signal after passing through the pseudo amplifier 31 from the signal vector of the IQ signal input from the IQ signal doubler 209 for each signal point. The calculation process including the IQ signal doubling unit 209 calculates the difference vector between the IQ signal point vector of the digital signal output from the pseudo satellite repeater 19 and the corresponding ideal IQ signal point vector for each signal point. This is the same operation as calculating the correction vector obtained by adding the ideal IQ signal point vector to the inverse vector of the difference vector. In addition, one calculation of the error vector can be omitted, and the calculation can be simplified.

  The input signal switching unit 211 outputs as one output signal by input time division switching.

  The switching control unit 212 performs switching control and synchronization control of the output signal switching unit 207 and the input signal switching unit 211. The switching control function enables selection switching of a desired compensation method (IQ signal vector calculation compensation or amplitude phase calculation compensation) according to the signal point arrangement, and an IQ signal corresponding to the time series arrangement of ideal IQ signal points. Can output.

  The OFDM conversion unit 15 allocates the signal input from the signal converter 18 to a large number of OFDM carriers by the S / P conversion units 151a and 151b. Next, the IFFT unit 152 converts a large number of OFDM carriers into the same number of time axis signals. Further, the obtained time axis signals are converted into one time series signal by the P / S converters 153a and 153b. Thereafter, the signal is input to the quadrature modulation unit 14, and the quadrature modulation unit 14 performs quadrature modulation according to a predetermined modulation method at the signal point corrected by the compensation calculation unit 20. The predetermined modulation schemes here include BPSK including π / 2 shift BPSK, QPSK including π / 4 shift QPSK, 8PSK, 16QAM, 32QAM, 64QAM, 128QAM, and 256QAM.

  Hereinafter, the operation of the transmission apparatus according to the fourth embodiment will be described in more detail.

  The digital signal input to the modulator in the transmitter 1 of the fourth embodiment is serial / parallel converted by the S / P converter 12 to the number of bits that can be transmitted per symbol by the modulation method used for transmission. The mapping unit 13 performs a mapping process for converting the converted signal into an I signal amplitude and a Q signal amplitude.

  Next, the signal mapped by the mapping unit 13 is divided into two, and one of the signals is allocated to a number of OFDM carriers by the OFDM conversion unit 30 and passed through the pseudo-amplifier 31 that simulates the characteristics of the amplifier 16. Here, the amplitude characteristics and group delay characteristics with respect to the frequencies of the filter 311 and the filter 313 in the pseudo-amplifier 31 and the AM-AM characteristics and AM-PM characteristics of the power amplifier 312 are set so as to approximate the characteristics of the amplifier 16. Preferably, it is set to a value at the time of designing the amplifier 16 or equivalent to a set value during operation of the amplifier 16. The signal after passing through the pseudo-amplifier 31 is converted into one signal series by the OFDM inverse conversion unit 32. This signal sequence is a sequence of signal points affected by the pseudo-amplifier 31.

  Note that when the filter 313 outputs the average power of the signal points output from the OFDM inverse transform unit 32 to be equal to the average power of the IQ signal points output from the mapping 13, the amplitude of all signal points is multiplied by a constant. Adjust and output. Needless to say, the pseudo-amplifier 31 is not strictly required to be identical to the characteristics of the amplifier 16 because it may simulate the characteristics of the amplifier 16. Therefore, as long as the filter 161, the power amplification unit 162, and the filter 163 have the same functions, the filter 161, the power amplification unit 162, and the filter 163 can be configured in an arbitrary manner. It can also be configured with a memory storing an uptable. Moreover, the filter 311 and the filter 313 can also be comprised with a digital filter.

  The signal mapped by the mapping unit 13 is also input to the output signal switching unit 207. Then, the switching control unit 212 switches whether the compensation method is IQ signal vector arithmetic compensation or amplitude phase arithmetic compensation according to a predetermined switching method. When switching these multiple compensation methods in a time division manner, it is necessary to synchronize the division (output signal switching unit 207) and the synthesis (input signal switching unit 211). Next, depending on the switching, IQ signal vector operation compensation by the delay unit 208, the IQ signal doubler unit 209, and the vector adder unit 210, or the delay unit 201, the IQ / amplitude phase conversion unit, for each signal point. 202 and 204, amplitude phase doubling unit 203, amplitude phase adding unit 205, and amplitude phase / IQ signal converting unit 206 perform amplitude phase calculation compensation. Note that the input signal switching unit 211 is configured so that the average power of the corrected IQ signal point is the same as the average power of the original ideal IQ signal point so as not to affect the subsequent processing after the OFDM conversion unit 30. The amplitude of all signal points is adjusted by a constant and output.

  As described above, according to the transmission device 1 of the fourth embodiment, in order to transmit a digital signal to the reception device via a predetermined transmission path, the digital signal is modulated by a predetermined modulation method and OFDM-multiplexed. The transmission apparatus is provided as a transmission apparatus. The transmission apparatus includes an OFDM conversion unit 30 that converts a frequency axis signal point sequence into a time axis OFDM signal, and a pseudo-transmitter having a characteristic corresponding to the characteristic of a target device on a transmission path. In the embodiment, a pseudo-amplifier 31), an OFDM inverse conversion unit 32 that converts a time-axis signal point sequence into a frequency-axis OFDM signal, and an ideal IQ signal after mapping from signal points of a digital signal transmitted through a pseudo-transmitter A compensation calculation unit 20 that compensates for a shift of a signal point after passing through the target device with respect to a point, an OFDM conversion unit 15 that converts the corrected signal point into a time-axis OFDM signal, and the time axis And a quadrature modulator 14 for quadrature modulating a FDM signal, it is possible to transmit a broadcast wave signal having improved degradation in required C / N.

  In addition, as in the case of expansion from the second embodiment to the third embodiment, the correction accuracy in the transmission device 1 can be further increased. That is, the transmission apparatus 1 according to the fourth embodiment includes an OFDM conversion unit 30, a pseudo-amplifier 31, an OFDM inverse conversion unit 32, and a compensation calculation unit 20 as a set of signal point converters 18 and a plurality of signals arranged in series. The OFDM converter 15 converts the IQ signal obtained through the last-stage signal point converter arranged in series into an OFDM signal, and the orthogonal modulator 14 outputs an output from the OFDM converter 15. It is also possible to configure so that the signals are orthogonally modulated.

  More specifically, as a mode in which the transmission apparatus 1 according to the fourth embodiment is expanded, in order to transmit a digital signal to the reception apparatus via a predetermined transmission path, the digital signal is modulated by a predetermined modulation method. It can be provided as a transmission apparatus that performs OFDM multiplexing transmission. This transmission apparatus 1 includes an OFDM converter 30 that converts a frequency axis signal point sequence into a time axis OFDM signal, and a pseudo transmitter (in this embodiment, a pseudo amplifier 31) having characteristics corresponding to characteristics of a target device on a transmission path. An OFDM inverse conversion unit 32 for converting a time-axis signal point sequence into a frequency-axis OFDM signal, and a signal after passing through the target device with respect to an ideal IQ signal point after mapping from a signal point of a digital signal transmitted via a pseudo transmitter 31 The compensation calculation unit 20 that compensates for the point shift is used as a set of signal point converters 18, and a plurality of signal point converters 18-n that are arranged in series and a plurality of signal point converters that are arranged in series, An OFDM conversion unit 15 that converts a signal point obtained by correcting a signal point after point mapping into a time-axis OFDM signal, and an orthogonal modulation unit 14 that performs orthogonal modulation on the time-axis OFDM signal are provided. It is also possible to adopt a configuration so as to transmit a broadcast wave signal having improved degradation in required C / N.

  In the above-described embodiment, the case where the present invention is applied to satellite digital broadcasting and terrestrial digital broadcasting that performs OFDM multiplexing has been described as a representative example. However, the present invention can also be applied to other transmission paths. For example, 16QAM modulation, 32QAM modulation, or the like is used as a modulation method for material transmission for transmitting a video signal from a shooting site to a studio via a communication satellite and / or a repeater. In this case, in the transmission apparatus 1 of the first to third embodiments, the mapping unit 13 is compatible with 16QAM or 32QAM modulation, and the characteristics of the pseudo satellite repeater 19 are the characteristics of the IMUX filter, TWTA, and OMUX filter of the communication satellite. It may be configured to approximate.

  Further, in the case where the digitally modulated signal is further subjected to electrical / optical conversion and transmitted through an optical fiber, and the optically / electrically converted signal is restored and digitally demodulated, an electrical / optical converter, Non-linear characteristics of the optical / electrical converter may be a problem. In such a case, in the transmission device 1 of the first to third embodiments, instead of configuring the pseudo satellite repeater 19 with the IMUX filter 191, the TWTA 192, and the OMUX filter 193, an electrical / optical converter, an optical / electrical converter By suppressing the deterioration due to the non-linear characteristics of the electrical / optical converter and the optical / electrical converter by making the characteristics non-linear characteristics of the electrical / optical converter and optical / electrical converter that are actually used. Can do.

  Moreover, the transmission apparatus in the present invention can also be applied to transmission systems other than OFDM that transmit via a terrestrial repeater.

  For example, in digital terrestrial broadcasting in the United States and Korea, an 8-value / 16-value VSB is transmitted after 8-point or 16-value signal points are modulated with equal spacing on one dimension and then half of the spectrum is removed by a filter. The ATSC system employing modulation is used, and there may be a case where the nonlinear characteristic of the power amplifier that finally outputs radio waves becomes a problem. In this case, in the transmission apparatus 1 of the first to third embodiments, the pseudo satellite repeater 19 is configured by the IMUX filter 191, the TWTA 192, and the OMUX filter 193, instead of the VSB filter and the power amplifier that perform predetermined band limitation. If a VSB filter that includes a VSB detector and further performs a predetermined band limitation before the quadrature modulation unit 14 is disposed, a VSB modulator that suppresses deterioration due to nonlinear characteristics of the power amplifier can be configured. In the ATSC system, 8-value / 16-value VSB modulation based on modulation in which 8-point or 16-value signal points are equally spaced in one dimension is adopted. However, the signal point on the IQ plane is set at the origin. If the modulation method is one-dimensionally arranged on a single straight line passing through, a VSB modulator based on the modulation method can be configured. For example, the number of signal points is selected as a power of 2 such as 32, 64, and 128. A modulation scheme in which signal points are arranged one-dimensionally at equal intervals or unequal intervals is also possible.

  Specifically, in the case of applying to VSB modulation, a transmission apparatus transmits a digital signal by VSB modulation using a predetermined modulation method in order to transmit the digital signal to the reception apparatus via a predetermined transmission path. Can be provided as a transmitting device. In accordance with the description of the first or second embodiment, this transmission device has characteristics of a VSB filter unit (not shown) that performs predetermined band limitation and a target device (for example, a repeater of the real satellite 2) on the transmission path. The pseudo transmitter 19 having corresponding characteristics, a VSB detector (not shown) that performs VSB detection, and the target for the ideal IQ signal point after mapping from the signal point of the digital signal transmitted via the pseudo transmitter 19 A compensation calculation unit 20 that compensates for the deviation of signal points after passing through the device, a VSB filter unit (not shown) that performs a predetermined band limitation on the signal point series corrected by the error vector, and an output of the VSB filter unit And an orthogonal modulation unit 14 that performs orthogonal modulation, and can be configured to suppress deterioration due to nonlinear characteristics on the transmission path.

  Furthermore, the transmission apparatus when applied to this VSB modulation has a VSB filter unit (not shown) for performing a predetermined band limitation and a target device (for example, the real satellite 2) on the transmission path according to the description of the third embodiment. A pseudo transmitter 19 having characteristics corresponding to the characteristics of the repeater), a VSB detection unit (not shown) for performing VSB detection, and an ideal IQ signal after mapping from a signal point of a digital signal transmitted via the pseudo transmitter 19 The compensation calculation unit 20 that compensates for the deviation of the signal point after passing through the target device with respect to the point is used as a set of signal point converters 18, a plurality of signal point converters 18-n in which these are arranged in series, and this series arrangement The VSB filter unit (not shown) that performs a predetermined band limitation on the signal point series obtained by correcting the signal points after mapping of the signal points by the compensation method by the plurality of signal point converters 18-n, and the VSB And a quadrature modulator 14 which quadrature-modulates the output of the filter section, may be configured to suppress degradation due to nonlinear characteristics of the transmission path.

  Although the above embodiments have been described as representative examples, it will be apparent to those skilled in the art that many variations and substitutions can be made within the spirit and scope of the invention. For example, in the above-described embodiment, the satellite repeater or the terrestrial transmission side amplifier has been described as an example. However, such a satellite repeater or the terrestrial transmission side amplifier has a frequency characteristic of phase and amplitude and nonlinearity. Since the present invention can be applied to a repeater, an electric device, an optical device, or a combination thereof having one or more known properties, these are collectively referred to as “target devices”. The transmission path is a signal path from signal modulation on the transmission side to signal demodulation on the reception side. In the above-described embodiment, the pseudo satellite repeater or the pseudo amplifier having the characteristics approximate to those of the satellite repeater or the terrestrial transmission side amplifier has been described. Since it can be configured by any device having characteristics approximating the characteristics of the target device on the transmission path (that is, characteristics corresponding to the characteristics of the target device on the transmission path), these are collectively referred to as a “pseudo transmitter”. The “approximate characteristics” (that is, “corresponding characteristics”) includes “equivalent characteristics”. That is, the essence of the present invention is to predict the distortion generated in the repeater or the transmission path in advance in the transmission apparatus, and to reduce the distortion component before transmitting, thereby improving the transmission characteristic. Any component of the repeater or the transmission path that causes deterioration may be used. In particular, as described in the embodiment, the present invention is effective for signal transmission of amplitude phase modulation.

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

  According to the present invention, since transmission path distortion can be suitably reduced, it can be configured as a dedicated apparatus such as a non-linear distortion correction apparatus and a digital modulation apparatus, and a digital signal signal via a transmission path having transmission distortion. Useful for processing applications.

DESCRIPTION OF SYMBOLS 1 Transmitter 2 Real satellite 3-1 to 3-N Receiver 11 Modulator 12, 151a, 151b, 301a, 301b, 321a, 321b Serial / parallel (S / P) conversion unit 13 Mapping unit 14 Orthogonal modulation unit 15, 30 OFDM conversion unit 16 Amplifier 17 Antenna 18, 18-1, 18-2 Signal point converter 19 Pseudo satellite repeater 20, 20-1, 20-2 Compensation operation unit 21, 191, 191-1, 191-2 Input Multiplexer (IMUX) filter 22, 192, 192-1, 192-2 Traveling wave tube amplifier (TWTA)
23, 193, 193-1, 193-2 Output multiplexer (OMUX) filter 31 Pseudo amplifier 32 OFDM inverse transform unit 152, 302 Inverse fast Fourier transform (IFFT) unit 153a, 153b, 303a, 303b, 323a, 323b Parallel / serial (P / S) converters 201, 201-1, 201-2, 208, 208-1, 208-2 delay units 202, 202-1, 202-2, 204, 204-1, 204-2, 213 IQ / Amplitude phase converter 203 Amplitude phase doubler 205, 205-1, 205-2 Amplitude phase adder 206, 206-1, 206-2 Amplitude phase / IQ converter 207, 207-1, 207-2 Output signal Switching unit 209 IQ signal doubler 210, 210-1, 210-2 Vector adder 211, 211-1, 211-2 Signal switching unit 212,212-1,212-2 switching control unit 322 fast Fourier transform (FFT) unit

Claims (6)

In order to transmit a digital signal to a receiving device via a predetermined transmission path, the transmitting device modulates the digital signal with a predetermined modulation method,
A pseudo-transmitter having characteristics approximating the characteristics of the target device on the transmission path;
An amplitude value and phase value obtained by converting IQ signal points of a digital signal output via the pseudo transmitter into amplitude and phase, and an ideal amplitude value and ideal phase value obtained by converting corresponding ideal IQ signal points into amplitude and phase. A corrected amplitude value and a corrected phase value obtained by adding the ideal amplitude value and the ideal phase value of the ideal IQ signal point to the sign inversion values of the amplitude error value and the phase error value, which are the difference between the corrected amplitude and the corrected amplitude value. An amplitude phase calculating means for generating a correction signal obtained by converting the value and the correction phase value into an IQ signal point;
Orthogonal modulation means for orthogonally modulating the correction signal;
A transmission device comprising: In order to transmit a digital signal to a receiving device via a predetermined transmission path, the transmitting device modulates the digital signal with a predetermined modulation method,
A pseudo-transmitter having characteristics approximating the characteristics of the target device on the transmission path;
It is obtained by adding the vector of the ideal IQ signal point to the inverse vector of the difference vector between the vector of the IQ signal point of the digital signal output via the pseudo transmitter and the vector of the corresponding ideal IQ signal point. Vector computing means for generating a first correction signal;
An amplitude value and phase value obtained by converting IQ signal points of a digital signal output via the pseudo transmitter into amplitude and phase, and an ideal amplitude value and ideal phase value obtained by converting corresponding ideal IQ signal points into amplitude and phase. A corrected amplitude value and a corrected phase value obtained by adding the ideal amplitude value and the ideal phase value of the ideal IQ signal point to the sign inversion values of the amplitude error value and the phase error value, which are the difference between the corrected amplitude and the corrected amplitude value. Amplitude phase calculation means for generating a second correction signal obtained by converting the value and the correction phase value into an IQ signal point;
Switching control means for switching and outputting the first correction signal and the second correction signal in a time-sharing manner;
Orthogonal modulation means for orthogonally modulating the correction signal output by switching by the switching means;
A transmission device comprising: In order to transmit a digital signal to a receiving device via a predetermined transmission path, the transmitting device modulates the digital signal with a predetermined modulation method,
A pseudo transmitter having characteristics approximating the characteristics of the target device on the transmission line;
It is obtained by adding the vector of the ideal IQ signal point to the inverse vector of the difference vector between the vector of the IQ signal point of the digital signal output via the pseudo transmitter and the vector of the corresponding ideal IQ signal point. Vector computing means for generating a first correction signal;
An amplitude value and phase value obtained by converting IQ signal points of a digital signal output via the pseudo transmitter into amplitude and phase, and an ideal amplitude value and ideal phase value obtained by converting corresponding ideal IQ signal points into amplitude and phase. A corrected amplitude value and a corrected phase value obtained by adding the ideal amplitude value and the ideal phase value of the ideal IQ signal point to the sign inversion values of the amplitude error value and the phase error value, which are the difference between the corrected amplitude and the corrected amplitude value. Amplitude / phase calculation means for generating a second correction signal obtained by converting the value and the correction phase value into an IQ signal point, and the first correction signal point and the second correction signal point by time division A plurality of signal point converters in which signal point converters provided in series are provided with switching control means for switching and outputting;
Quadrature modulation means for quadrature modulating the first correction signal or the second correction signal output from the signal point converter at the last stage of the plurality of signal point converters arranged in series;
A transmission device comprising: In order to transmit a digital signal toward a receiving device via a predetermined transmission path, the digital signal is modulated by a predetermined modulation method and OFDM-multiplexed and transmitted.
A first OFDM converter for converting a frequency axis signal point sequence to a time axis OFDM signal;
A pseudo-transmitter having characteristics approximating the characteristics of the target device on the transmission path;
An OFDM inverse conversion unit for converting a time axis signal point sequence into a frequency axis OFDM signal;
Inverse vector of a difference vector between a vector of IQ signal points of a digital signal output via the first OFDM conversion unit, the pseudo transmitter, and the OFDM inverse conversion unit and a corresponding vector of ideal IQ signal points A vector calculation means for generating a first correction signal obtained by adding the vectors of the ideal IQ signal points;
An amplitude value and a phase value obtained by converting an IQ signal point of a digital signal output through the first OFDM conversion unit, the pseudo transmitter, and the OFDM inverse conversion unit into an amplitude and a phase, and a corresponding ideal IQ signal The ideal amplitude value and the ideal phase value of the ideal IQ signal point are added to the sign-inverted values of the amplitude error value and the phase error value, which are the difference between the ideal amplitude value and the ideal phase value obtained by converting the point into amplitude and phase. An amplitude phase calculation means for calculating a corrected amplitude value and a corrected phase value, and generating a second corrected signal obtained by converting the corrected amplitude value and the corrected phase value into an IQ signal point;
Switching control means for switching and outputting the first correction signal and the second correction signal in a time-sharing manner;
A second OFDM converter that converts the correction signal switched and output by the switching means into a time-axis OFDM signal;
Orthogonal modulation means for orthogonally modulating the OFDM signal converted by the second OFDM conversion unit;
A transmission device comprising: In order to transmit a digital signal toward a receiving device via a predetermined transmission path, the digital signal is modulated by a predetermined modulation method and OFDM-multiplexed and transmitted.
A first OFDM converter that converts a frequency-axis signal point sequence into a time-axis OFDM signal;
A pseudo transmitter having characteristics approximating the characteristics of the target device on the transmission line;
An OFDM inverse converter for converting a time-axis signal point sequence into a frequency-axis OFDM signal;
Inverse vector of a difference vector between a vector of IQ signal points of a digital signal output via the first OFDM conversion unit, the pseudo transmitter, and the OFDM inverse conversion unit and a corresponding vector of ideal IQ signal points A vector calculation means for generating a first correction signal obtained by adding the vectors of the ideal IQ signal points,
An amplitude value and a phase value obtained by converting an IQ signal point of a digital signal output through the first OFDM conversion unit, the pseudo transmitter, and the OFDM inverse conversion unit into an amplitude and a phase, and a corresponding ideal IQ signal The ideal amplitude value and the ideal phase value of the ideal IQ signal point are added to the sign-inverted values of the amplitude error value and the phase error value, which are the difference between the ideal amplitude value and the ideal phase value obtained by converting the point into amplitude and phase. Amplitude phase calculation means for calculating the corrected amplitude value and the corrected phase value, and generating a second correction signal obtained by converting the corrected amplitude value and the corrected phase value into IQ signal points; and the first correction signal And a plurality of signal point converters in which signal point converters are arranged in series, each of which includes switching control means for switching and outputting the second correction signal in a time-sharing manner,
A second OFDM converter that converts the first correction signal or the second correction signal output from the signal point converter at the last stage of the plurality of signal point converters arranged in series into a time-axis OFDM signal;
Orthogonal modulation means for orthogonally modulating the OFDM signal converted by the second OFDM conversion unit;
A transmission device comprising:   The switching control means outputs the first correction signal when the amplitude of the ideal IQ signal point is equal to or smaller than a predetermined magnitude, and the second correction signal when the amplitude of the ideal IQ signal point is larger than a predetermined magnitude. 6. The transmission apparatus according to claim 2, further comprising means for switching and outputting the correction signal in a time division manner.

Images