JP2008091985A - Transmission method and transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To add reverse distortion, where timing adjustment is performed to nonlinear distortion in a power amplifier for transmission precisely, to a transmission signal for correction. <P>SOLUTION: A baseband signal subjected to digital modulation is upsampled by a CIC interpolator 4, is modulated orthogonally at a digital orthogonal modulation section 5 for converting to an RF signal by a mixer 7, and is transmitted from an antenna 9 by amplifying power at a high-frequency amplification section 8. One portion of a transmission RF signal is converted to a feedback IF signal by a mixer 10. Downsampling is performed by a CIC decimator 13. The error between the amplitude of a feedback digital baseband signal and that of a transmission digital baseband signal is calculated by an error calculation section 14. According to the error, the reverse distortion is calculated by a reverse distortion calculation section 15. The reverse distortion is added by a reverse distortion addition section 3. The fine adjustment of comparison timing to the transmission digital baseband signal of the feedback digital baseband signal at the error calculation section 14 is performed by adjusting a thin-out point in the CIC decimator 13 so that the error is minimized. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a transmission method and a transmission apparatus that add in advance a reverse distortion that cancels a non-linear distortion applied at the time of high-frequency power amplification when transmitting a signal.

  The structure of the main part of the conventional QPSK transmitter is shown in FIGS. In the QPSK transmission apparatus of FIG. 7, after the I and Q components of the transmission baseband signal modulated by the modulation processing unit 51 operating at the clock f3 are converted into analog signals by the DA conversion units 52 and 53, the analog quadrature The modulation unit 54 performs quadrature modulation with the clock f4 and converts the frequency to a transmission IF signal. The mixer 55 further converts the frequency from the transmission IF signal to the transmission RF signal with the clock f5. Will be sent.

  The analog quadrature modulation unit 54 does not directly convert the frequency to the RF signal, but first converts the frequency to the IF signal and then converts the frequency to the RF signal again because the frequency of the baseband signal is low. This is because the frequency of the two waves becomes too close to make filtering in the RF band difficult, and this needs to be avoided.

  When the RF signal is amplified by the high-frequency amplifier 56, the high-frequency amplifier 56 has nonlinearity in its input / output characteristics, so that distortion is applied there. A part of the transmission RF signal to which this distortion is applied is taken out by a coupler provided in the high-frequency amplifier 56 and becomes a feedback RF signal. The mixer 58 converts the frequency into a feedback IF signal by the clock f5, and the analog orthogonal demodulator In 59, the signal is orthogonally demodulated into a feedback baseband signal having an I component and a Q component by the clock f6, converted into a digital signal by the AD conversion units 60 and 61, and fed back to the feedback processing unit 62 operating at the clock f3.

  The feedback processing unit 62 compares the amplitudes of the transmission baseband signal and the feedback baseband signal for the same data to create a reverse distortion component, and the modulation processing unit 51 determines the next time according to the reverse distortion component. Inverse distortion is added to the transmitted baseband signal. As a result, when the transmission baseband signal to which reverse distortion is added is subjected to quadrature modulation (IF conversion), RF conversion, and input to the high-frequency amplification unit 56, the non-linear distortion therein is canceled and the transmission signal is improved in distortion. Is transmitted from the antenna 57.

  The QPSK transmission apparatus of FIG. 8 is different from the QPSK transmission apparatus of FIG. 7 in that it operates at the clock f7 and converts the frequency of the feedback IF signal into a feedback baseband signal, and converts the feedback baseband signal into a digital signal. The difference is that an AD conversion unit 64 and a feedback processing unit 62A having a digital quadrature demodulation function that quadrature demodulates the IF signal to the I component and Q component of the feedback baseband signal are provided. That is, in this transmission apparatus, feedback quadrature demodulation is performed digitally.

  The QPSK transmission apparatus of FIG. 9 is different from the QPSK transmission apparatus of FIG. 7 in that it operates at the clock f7 and converts the feedback IF signal to a feedback baseband signal and converts the feedback baseband signal to a digital signal. AD conversion unit 64, feedback processing unit 62A having a digital quadrature demodulation function that quadrature demodulates the IF signal to the I component and Q component of the feedback baseband signal, and digital quadrature that quadrature modulates the I and Q components of the transmission baseband signal A modulation processing unit 51A having a modulation function, a DA conversion unit 65 that converts the orthogonally modulated transmission baseband signal into an analog signal, and a mixer 66 that converts the transmission baseband signal into a transmission IF signal using the clock f8. Is different. That is, this transmitting apparatus digitally performs quadrature modulation of the transmission system and digitally performs quadrature demodulation of the feedback system.

  However, in the QPSK transmission apparatus of FIGS. 7 and 8, since the analog quadrature modulation unit 54 and the analog quadrature demodulation unit 59 are used, the orthogonality is not perfect or offset because of the analog circuit, If these are not compensated for, the distortion of the high-frequency amplifier 56 cannot be compensated effectively, so circuits and processing for orthogonality compensation and origin offset compensation must be added (see, for example, Patent Document 1). .

On the other hand, since the QPSK transmission apparatus of FIG. 9 performs digital processing for both orthogonal modulation and demodulation, there is no need for orthogonality compensation or origin offset compensation.
JP-A-10-065570

  However, in the QPSK transmitter of FIG. 9, the feedback signal returns to the feedback processor 62A having the digital quadrature demodulator via the analog circuit, so that a difference occurs in the delay amount of the feedback baseband signal for each receiver. The comparison timing of the feedback baseband signal to the transmission baseband signal becomes inaccurate, and high-precision distortion compensation cannot be realized. The same applies to the transmission apparatus of FIG.

  An object of the present invention is to enable a fine adjustment of a comparison timing between a feedback digital baseband signal and a transmission digital baseband signal with high accuracy, and to add appropriate reverse distortion to the transmission digital baseband signal. It is to provide a transmission method and a transmission apparatus.

In order to achieve the above object, a transmission method according to a first aspect of the present invention includes a transmission digital baseband signal that is up-sampled, modulated, converted into an analog signal, and then subjected to high-frequency power amplification for transmission. A part of the signal to be extracted, demodulated and converted to a digital signal, and then down-sampled to obtain the sampling rate of the digital baseband signal to obtain a feedback digital baseband signal, and the transmission digital baseband signal and the transmission A transmission method for calculating reverse distortion according to an amplitude error by comparison with the feedback digital baseband signal corresponding to a digital baseband signal, and adding the reverse distortion to the transmission digital baseband signal, wherein the transmission digital The ratio of the feedback digital baseband signal to the baseband signal And performing fine adjustment of the timing by adjusting the decimation point in the down-sampling.
According to a second aspect of the present invention, in the transmission method according to the first aspect, the adjustment of the decimation point is performed when the random test signal is input as the transmission digital baseband signal and the feedback to the transmission digital baseband signal. The adjustment is to find a point where the amplitude error of the digital baseband signal is minimized.
According to a third aspect of the present invention, there is provided a transmitting apparatus that up-samples a transmission digital baseband signal by an interpolator, performs quadrature modulation thereafter, converts the quadrature modulated digital signal into an analog signal, and then performs high-frequency power amplification. A transmission system processing means for transmitting the signal, a part of the transmission signal transmitted from the transmission system processing means is taken out and converted into a digital signal, and then orthogonally demodulated, and the digital signal after the orthogonal demodulation is transmitted to the transmission baseband signal by a decimator. A feedback system processing means for down-sampling to a sampling rate of 2 to obtain a feedback digital baseband signal, and an amplitude error due to comparison between the transmission digital baseband signal and the feedback digital baseband signal corresponding to the transmission digital baseband signal And a reverse distortion calculating means for calculating the reverse distortion in response, and the reverse distortion calculating means And a reverse distortion adding means for adding the reverse distortion calculated in step (b) to the transmission digital baseband signal, wherein the comparison timing of the feedback digital baseband signal with respect to the transmission digital baseband signal is finely adjusted. Control means for adjusting the thinning point in the downsampling is provided.
According to a fourth aspect of the present invention, in the transmission device according to the third aspect, the control means adjusts the thinning point when the random test signal is input as the transmission digital baseband signal. It is characterized in that it is performed by thinning-out points that minimize the amplitude error of the feedback digital baseband signal with respect to the band signal.
The invention according to claim 5 is the transmission device according to claim 3 or 4, wherein the interpolator is a CIC interpolator, the decimator is a CIC decimator, and the setting of the thinning point is performed in the CIC decimator. This is performed by selecting a thinning point of the thinning portion.
According to a sixth aspect of the present invention, in the transmission device according to the third, fourth, or fifth aspect, the transmission system processing unit includes a digital quadrature modulation unit that quadrature modulates the upsampled transmission digital baseband signal; A DA converter that converts the digital signal quadrature modulated by the digital quadrature modulator into an analog signal; and the feedback processing means includes an AD converter that converts the analog signal into a digital signal; A digital quadrature demodulation unit that quadrature demodulates the feedback signal converted into a digital signal by the unit, the interpolator, the digital quadrature modulation unit, the DA conversion unit, the AD conversion unit, the digital quadrature demodulation unit, and The decimator is operated with a common clock.

  According to the present invention, when the feedback digital baseband signal is thinned and the feedback digital baseband signal is downsampled, the transmission digital baseband of the feedback digital baseband signal is adjusted by adjusting the thinning point. Since the comparison timing for the signal is finely adjusted, the fine adjustment can be realized with high accuracy according to the downsampling ratio, and the comparison between the transmission digital baseband signal and the feedback digital baseband signal is performed at an accurate timing. Therefore, an accurate amplitude error can be obtained, and good distortion compensation can be performed. Further, if the feedback digital baseband signal is thinned out by the CIC decimator, the multiplication circuit can be eliminated and the circuit scale can be reduced as compared with the case where the FIR filter is used for filtering. In addition, by using the same clock for the interpolator, decimator, digital quadrature modulation, digital quadrature demodulation, DA converter, and AD converter, the clock source composed of analog circuits can be reduced and the size can be reduced. In addition to realizing cost reduction, the processing is synchronized, and there is no influence of jitter between clocks, which becomes a problem when using different clocks, and distortion compensation can be performed with high accuracy.

  FIG. 1 is a block diagram showing a configuration of a QPSK transmission apparatus according to one embodiment of the present invention. 1 is a control unit that generates and controls digital transmission data, 2 is a modulation processing unit that modulates transmission data to generate an I component and a Q component of a transmission digital baseband signal, and 3 is modulated by a modulation processing unit 2 The inverse distortion adding unit 4 applies inverse distortion to the I component and Q component of the transmitted digital baseband signal, 4 interpolates the transmission digital baseband signal by “0” with the clock f1 and transmits the transmitted digital baseband signal. A CIC interpolator (CIC Interpolator) 5 composed of a CIC filter for upsampling a baseband signal is inputted with I component and Q component of a transmission digital baseband signal, and is orthogonally modulated by a clock f1 and converted into a transmission IF signal. Digital quadrature modulation unit 6 is a DA conversion unit that converts a transmission IF signal into an analog signal by a clock f1, 7 Mixer for frequency-converting the transmit RF signal analog transmission IF signal by the clock f2, 8 are high-frequency amplifier section for power amplification, 9 is an antenna.

  Also, 10 is a mixer that converts the feedback RF signal extracted from the coupler of the high-frequency amplifier 8 into a feedback IF signal using the clock f2, and 11 is an AD converter that converts the analog feedback IF signal into a digital feedback IF signal using the clock f1. , 12 is a digital quadrature demodulator that quadrature demodulates the feedback IF signal with the clock f1 to generate the I component and Q component of the feedback digital baseband signal, and 13 is the clock f1 with the I component and Q component of the feedback digital baseband signal. And a CIC decimator (CIC Decimator) comprising a CIC filter that is downsampled so as to have the same sampling rate as that of the transmission digital baseband signal, and 14 is an I component and a Q component of the downsampled feedback digital baseband signal. Transmission obtained by the modulation processing unit 2 An error calculation unit 15 that takes in the I component and Q component of the digital baseband signal and compares the amplitudes, and 15 performs reverse distortion calculation using the error data obtained by the error calculation unit 14 and inputs the result to the reverse distortion addition unit 3. A distortion calculation unit 16 is a setting data storage unit for storing delay adjustment data.

  In relation to the claims, the modulation processing unit 2, the CIC interpolator 4, the digital quadrature modulation unit 5, the DA conversion unit 6, the mixer 7, and the high frequency amplification unit 8 constitute an example of transmission system processing means. . The mixer 10, the AD conversion unit 11, the digital quadrature demodulation unit 12, and the CIC decimator 13 constitute an example of feedback system processing means. The error calculation unit 14 and the reverse distortion calculation unit 15 constitute an example of a reverse distortion calculation unit. Moreover, the reverse distortion addition part 3 comprises an example of a reverse distortion addition means. Moreover, the control part 1 comprises an example of a control means.

  The CIC interpolator 4 includes comb units 41I and 41Q, interpolation units 42I and 42Q, and integration units 43I and 43Q for both the I component path and the Q component path, and the interpolation units 42I and 42Q and the integration units 43I and 43Q. Is operated by the clock f1.

  The CIC decimator 13 includes integration units 131I and 131Q, decimation units 132I and 132Q, and comb units 133I and 133Q for both the I component path and the Q component path. The integration units 131I and 131Q and the decimation units 132I and 132Q Operated by f1. The decimation points 132I and 132Q are controlled by the control unit 1 so that the delay time until the I and Q components are taken into the error calculation unit 14 can be adjusted. Yes.

  The transmission data output from the control unit 1 is modulated by the modulation processing unit 2 into the I component and the Q component of the transmission digital baseband signal at the 48 kHz sampling rate, and then the reverse distortion is added by the reverse distortion adding unit 3. To the CIC interpolator 4.

  In the CIC interpolator 4, the comb units 41I and 41Q operate at 48 kHz generated by dividing the frequency 19.2 MHz of the clock f1 by 400, and the interpolation units 42I and 42Q have I and Q components with a sampling rate of 48 kHz. By interpolating 399 “0” data per data and integrating by integrating units 43I and 43Q operating at 19.2 MHz, the data becomes 19.2 MHz sampling rate, and sampling of the transmission digital baseband signal is performed. The rate is multiplied by 400. This CIC interpolator 4 has the characteristics of a comb filter as shown in FIG. 2, and a harmonic of a specific frequency generated by “0” interpolation is attenuated. FIG. 2A shows filter characteristics, and FIG. 2B shows a spectrum of harmonics generated by “0” interpolation.

  In the digital quadrature modulation unit 5, the I component is multiplied by a sine wave of 4.8 MHz (sampling rate is 19.2 MHz), and the Q component is cosine wave of 4.8 MHz (sampling rate is 19.2 MHz). ) Is multiplied. The quadrature modulation is completed by adding the I component multiplied by the sine wave and the Q component multiplied by the cosine wave.

  The quadrature-modulated 4.8 MHz (sampling rate 19.2 MHz) transmission IF signal is converted to an analog signal by the DA converter 6, frequency-converted to a transmission RF signal by the mixer 7, and power amplified by the high-frequency amplifier 8. And transmitted from the antenna 9. Further, a part of the transmission RF signal taken out by the coupler of the high frequency amplifying unit 8 is input to the mixer 10 as a feedback RF signal, converted into a frequency of 4.8 MHz, converted into a digital signal by the AD converting unit 11, Input to the digital quadrature demodulator 12.

  In this digital quadrature demodulator 12, a 4.8 MHz sine wave (sampling rate is 19.2 MHz) and a 4.8 MHz cosine wave (sampling) with respect to a feedback IF signal of 4.8 MHz (sampling rate is 19.2 MHz). The rate is multiplied by 19.2 MHz), and the I component and Q component of the feedback digital baseband signal having a sampling rate of 19.2 MHz are reproduced. Also in this digital quadrature demodulator 12, multiplication of sine waves and cosine waves can be processed by sign inversion. Then, the IIC and Q components of the feedback baseband signal having a quadrature demodulated sampling rate of 19.2 MHz are taken into the CIC decimator 13.

  In the CIC decimator 13, the I component and the Q component of the feedback digital baseband signal having a sampling rate of 19.2 MHz are thinned out to 1/400, and each is set to a 48 kHz sampling rate. The CIC decimator 13 differs from the CIC interpolator 4 only in that the input direction of the signal is reversed and that the thinning is performed at the location where the interpolation was performed at the interpolating rate. The thinning-out parts 132I and 132Q extract data at a time interval of 48 kHz from 400 I components and Q components having a sampling rate of 19.2 MHz, and input the extracted data to the subsequent comb parts 133I and 133Q. The I and Q components of the feedback digital baseband signal whose sampling rate is lowered by the CIC decimator 13 and whose sampling rate is 48 kHz are input to the error calculation amplifying unit 14.

  In the error calculation amplification unit 14, the amplitude error between the I component and Q component of the feedback digital baseband signal input from the CIC decimator 13 and the I component and Q component of the transmission digital baseband input from the modulation processing unit 2 for the same data. Is calculated, and the amplitude error data is input to the inverse distortion calculation unit 14 and the control unit 1. In the reverse distortion calculation unit 15, reverse distortion data is generated based on the amplitude error data, and this is input to the reverse distortion addition unit 3.

  The control unit 1 adjusts the comparison timing in the error calculation unit 14 and the thinning point of the CIC decimator 13 based on the amplitude error data. Since the I component and Q component of the feedback digital baseband signal return to the error calculation unit 14 after passing through the analog circuit, the I component and Q component of the transmission digital baseband signal are accompanied by a delay. The delay is a value specific to each transmitting apparatus. Therefore, the control unit 1 sets the comparison timing (rough adjustment) between the data in the error calculation unit 14 according to the delay error data described above, and the thinning point (extraction point) in the CIC decimator 13 is 400 points. The point of which is to be selected is selected and the comparison timing is finely adjusted (the delay of the feedback digital baseband signal is finely adjusted). Since this fine adjustment can be performed at a time interval of 19.2 MHz, high-precision adjustment can be performed.

  FIG. 3 is an explanatory diagram of fine adjustment of the delay by adjusting the thinning point of the CIC decimator 13. Here, for simplification, a case of thinning out one point out of 10 points will be described. In 1/10 decimation, one piece of data is extracted from ten pieces of data in the unit period T of one process in FIG. For example, as shown in FIG. 3 (b), when the third data is extracted every time T and when the seventh data is extracted every time T as shown in FIG. 3 (c), When the time t = 0 is set, the waveform of the data generated by this extraction is as shown in FIGS. 3 (d) and 3 (e). That is, the waveform obtained by extracting the seventh data each time has a smaller delay than the waveform obtained by extracting the third data each time.

  As described above, since the delay can be finely adjusted at the extraction point, the delay adjustment resolution is 1/400 in the present embodiment in which the decimation is 1/400, and extremely fine adjustment can be performed. The delay setting data indicating the number of data extracted here is stored in the setting data storage unit 16 as setting data specific to the QPSK transmission apparatus, and is controlled as a default when the QPSK transmission apparatus is activated next time. It is read by the unit 1 and used for fine delay adjustment.

  Here, a method for determining the delay amount (comparison timing) will be described in detail. When a random test modulation signal (such as PN9) is transmitted as a transmission baseband signal, a feedback digital baseband signal corresponding to the test modulation signal is obtained. Therefore, after setting the thinning points 132I and 132Q of the CIC decimator 13 to the leading point 0 (0 of 0 to 399), the data timing difference (symbol) between the transmission test modulation signal and the feedback test modulation signal is determined. (1/10 timing difference) is 0 to N (N: for example, 200) data, the amplitude error between the transmission test modulation signal and the feedback test modulation signal is calculated, and the data timing difference that minimizes the amplitude error is specified. . Next, in the obtained data timing difference, the thinning point is moved from 0 to 399, and the thinning point at which the amplitude error between the transmission test modulation signal and the feedback test modulation signal is minimized is specified. If the transmission test modulation signal is a fixed pattern with periodicity, the minimum amplitude error point will not be the point of the optimal delay amount that matches the comparison timing, but when using a random test modulation signal as described above, It will be. As a result, the thinning point (fine adjustment) of the minimum amplitude error point obtained by scanning the thinning point to the specific data timing difference (coarse adjustment result) of the minimum amplitude error point obtained by scanning the data timing difference. The time including the result is an optimum delay amount of the feedback digital baseband signal for comparing the transmission digital baseband signal and the feedback digital baseband signal.

  FIG. 4 shows a flowchart of the delay amount determination process described above. Here, the above-described data timing difference is represented by the number of blocks. In the error calculation unit 14, when there is no difference between the transmission timing of the transmission digital baseband signal and the feedback timing of the feedback digital baseband signal corresponding to the transmission digital baseband signal, the number of blocks is 0, and one data , The number of blocks = 1, the number of blocks for two data = 2,..., The number of blocks for N data = N. First, the block number = 0 and the thinning-out point = 0 are initialized (step S1), and then the test modulation signal is transmitted (step S2), the feedback signal is captured (step S3), the transmission test modulation signal and the feedback test modulation signal The amplitude error is calculated from the above and the result is recorded (step S4). Next, the number of blocks is incremented to 1, the same amplitude error calculation is performed, the result is recorded, and the same is repeated until the number of blocks = N (steps S5 and S6).

  For the amplitude error calculation, for example, an average value by the sum of squares is used. That is, for example, when the number of blocks = 2, the amplitude error between the transmission test modulation signal and the feedback test modulation signal having a timing difference for two data is obtained for each data, and all squared values are added. Thus, the sum of squares is obtained, and this is set as the average amplitude error value of the number of blocks = 2. Then, all amplitude error average values in the number of blocks = 0 to N are obtained, and the number of blocks from which the minimum error average value is obtained is obtained (steps S7 and S8).

  Next, in the obtained number of blocks, the thinning point = 0 is set (step S9), and the test modulation signal is transmitted (step S10), the feedback test modulation signal is captured (step S11), and the transmission test modulation signal An amplitude error is calculated from the feedback test modulation signal and the result is recorded (step S12). Next, the thinning point is incremented to 1, the same amplitude error calculation is performed, the result is recorded, and the same is repeated until the thinning point = 399 (steps S13 and S14).

  For the amplitude error calculation here, for example, a square sum average is used. That is, for example, when the thinning point = 5, assuming that the number of blocks from which the minimum error average value is output = 2, the timing difference between the transmission test modulation signal and the feedback test modulation signal corresponding to the transmission test modulation signal is Assuming the value obtained by adding the difference of the thinning point = 5 to the number of blocks = 2, the amplitude error between the transmission test modulation signal and the feedback test modulation signal having this timing difference is obtained for each data, and this is squared. The sum of squares is calculated to obtain the sum of squares, and this is set as the average amplitude error value of thinning point = 5. Then, all amplitude error average values at the thinning point = 0 to 399 are obtained, and the thinning point at which the smallest error average value is obtained is obtained (steps S15 and S16).

  As described above, by transmitting the test modulation signal prior to use, the number of blocks and the thinning point of the CIC decimator can be determined, and thereby the feedback digital baseband signal corresponding to the transmission digital baseband signal. Can be specified at a highly accurate timing. The number of blocks and the thinning points are stored in the setting data storage unit 16, and are set in the thinning 132I and 132Q of the error calculation unit 14 and the CIC decimator 13 by the control unit 1 during the subsequent operation. FIG. 5 schematically shows a transmission signal and a feedback signal when the number of blocks = 2 and the thinning point = n are the minimum amplitude error points.

  Further, FIG. 6A shows the amplitude error characteristics of each block simulated by the above method. Here, the number of blocks = 99 is the minimum amplitude error point. FIG. 6B shows the amplitude error characteristic when the number of blocks = 99. Here, the thinning point = 2 is the minimum amplitude error point.

  In the QPSK transmitter of the embodiment described above, the mixers 7 and 10 are not necessarily required, and the output of the DA converter 6 may be a transmission RF signal and the input of the AD converter 11 may be a feedback RF signal. In the configuration in which the digital quadrature modulation processing unit 5 is connected to the previous stage and the DA conversion unit 6 is connected to the subsequent stage, the DA conversion unit that converts the I component and the Q component into an analog signal is connected to the previous stage, and the analog circuit is connected to the subsequent stage. A configuration in which an orthogonal modulation processing unit is connected may be used. Further, the configuration in which the AD conversion unit 11 is connected to the previous stage and the digital quadrature demodulation processing unit 12 is connected to the subsequent stage, the analog quadrature demodulation processing unit that performs quadrature demodulation of the analog signal output from the mixer 10 into the I component and the Q component is provided in the previous stage. May be replaced with a configuration in which an AD conversion unit that converts analog signals of I component and Q component into digital is connected to the subsequent stage. Of course, the present invention is not limited to the QPSK transmission apparatus, but can be applied to any other type of transmission apparatus. The CIC interpolator 4 is not limited to this, and other interpolation means can be used. The CIC decimator 13 is not limited to this, and other thinning means can be used.

It is a block diagram which shows the structure of the QPSK transmitter of one Example of this invention. (a) is a characteristic diagram showing a filtering characteristic when “0” interpolation is performed by a CIC interpolator, and (b) is a characteristic diagram of a harmonic spectrum generated by “0” interpolation. It is a wave form diagram for explanation of delay adjustment in a CIC decimator. It is a flowchart of a delay amount determination process. It is a schematic diagram for explanation of a delay of a feedback signal with respect to a transmission signal. It is a characteristic view of an amplitude error for determining the delay amount. It is a block diagram which shows the structure of the conventional QPSK transmitter. It is a block diagram which shows the structure of another conventional QPSK transmission apparatus. It is a block diagram which shows the structure of another conventional QPSK transmission apparatus.

Claims (6)

The transmission digital baseband signal is up-sampled, modulated and converted to an analog signal, and then subjected to high-frequency power amplification and transmitted. A part of the transmitted signal is extracted, demodulated and converted into a digital signal, and then Amplitude error due to comparison between the transmission digital baseband signal and the feedback digital baseband signal corresponding to the transmission digital baseband signal by down-sampling to a digital baseband signal sampling rate to obtain a feedback digital baseband signal A reverse distortion is calculated according to the transmission method, and the reverse distortion is added to the transmission digital baseband signal,
A transmission method characterized by finely adjusting a comparison timing of the feedback digital baseband signal with respect to the transmission digital baseband signal by adjusting a thinning point in the downsampling. The transmission method according to claim 1,
The adjustment of the decimation point is an adjustment for finding a point where an amplitude error of the feedback digital baseband signal with respect to the transmission digital baseband signal is minimized when a random test signal is input as the transmission digital baseband signal. A transmission method characterized by the above. Transmission system processing means for up-sampling a transmission digital baseband signal by an interpolator, performing quadrature modulation thereafter, converting the quadrature modulated digital signal into an analog signal, and performing high-frequency power amplification and transmitting A part of the transmission signal transmitted from the system processing means is taken out and converted into a digital signal, and then quadrature demodulated, and the digital signal after quadrature demodulation is down-sampled to the sampling rate of the transmission baseband signal by a decimator and a feedback digital base Feedback system processing means for making a band signal, and inverse distortion calculation means for calculating reverse distortion in accordance with an amplitude error due to comparison between the transmission digital baseband signal and the feedback digital baseband signal corresponding to the transmission digital baseband signal And the reverse distortion calculated by the reverse distortion calculation means as the transmission digital A transmission device equipped with a reverse distortion adding means for adding the baseband signal,
Control means for performing fine adjustment of the comparison timing of the feedback digital baseband signal with respect to the transmission digital baseband signal by adjusting a thinning point in the downsampling,
A transmission apparatus characterized by the above. The transmission device according to claim 3, wherein
The control means adjusts the thinning point, and when a random test signal is input as the transmission digital baseband signal, a thinning point at which an amplitude error of the feedback digital baseband signal with respect to the transmission digital baseband signal is minimized. The transmission apparatus characterized by performing by these. The transmission device according to claim 3 or 4,
The interpolator is a CIC interpolator, the decimator is a CIC decimator, and the setting of the thinning point is performed by selecting the thinning point of the thinning unit in the CIC decimator.
A transmission apparatus characterized by the above. The transmission device according to claim 3, 4 or 5,
The transmission system processing means includes: a digital orthogonal modulation unit that orthogonally modulates the upsampled transmission digital baseband signal; and a DA conversion unit that converts the digital signal orthogonally modulated by the digital orthogonal modulation unit into an analog signal; Further comprising
The feedback system processing means includes an AD converter that converts the analog signal into a digital signal, and a digital orthogonal demodulator that orthogonally demodulates the feedback signal converted into a digital signal by the AD converter,
A transmitter characterized in that the interpolator, the digital quadrature modulation unit, the DA conversion unit, the AD conversion unit, the digital quadrature demodulation unit, and the decimator are operated with a common clock.

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