JP4287566B2 - OFDM transmitter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an OFDM transmission apparatus for transmitting a signal in which a plurality of subcarriers are linearly modulated and further subjected to orthogonal frequency division multiplexing (hereinafter referred to as OFDM) using inverse fast Fourier transform (hereinafter referred to as IFFT). About.
[0002]
[Prior art]
FIG. 19 shows a configuration of a conventional OFDM transmission apparatus that performs band division transmission. The OFDM transmitter includes a primary modulation unit 11, a subcarrier division unit 12, an IFFT unit 13, a digital / analog (hereinafter referred to as D / A) conversion unit 14, and a low-pass filter (hereinafter referred to as LPF) unit. 15, a quadrature modulation unit 16, a center frequency oscillator 17, a 90 ° shifter 18, a transmission unit 19, and a transmission antenna 20.
[0003]
The primary modulation unit 11 receives serial data of a complex data series and converts the serial data into a signal composed of an in-phase signal and a quadrature signal such as BPSK and QPSK. The subcarrier dividing unit 12 divides the primary modulated signal into a plurality of groups. The IFFT unit 13 performs inverse fast Fourier transform on the in-phase signal and the quadrature signal. The D / A conversion unit 14 converts the time-series sample waveform of the in-phase signal and the quadrature signal from the IFFT unit 13. The LPF unit 15 removes the folding signal included in the analog signal output from the D / A conversion unit 14.
[0004]
The quadrature modulation unit 16 uses a predetermined center frequency output from the center frequency oscillator 17 as a first carrier, a center frequency obtained by shifting the phase of the center frequency by 90 ° by a 90 ° shifter 18 as a second carrier, and LPF An OFDM signal composed of information carriers having the number of subcarriers primarily modulated by the in-phase signal and the quadrature signal output from the unit 15 is generated. The transmission unit 19 transmits the OFDM signal from the transmission antenna 20 after linear amplification.
[0005]
FIG. 20 is a diagram illustrating an output waveform of the IFFT unit 13 in the OFDM signal transmitter. The horizontal axis represents time, and the vertical axis represents signal power. An OFDM signal obtained by subjecting a digital serial signal to primary modulation and IFFT processing has a noise-like time waveform. Here, if the instantaneous power versus the average power value (hereinafter referred to as PMPR) of the transmission signal is small, it can be converted into an analog signal that maintains linearity without using a broadband and expensive amplifier.
[0006]
[Problems to be solved by the invention]
However, the OFDM signal includes a signal having a large maximum amplitude value with respect to the average amplitude value, and causes distortion when converted to an analog signal. In the above conventional OFDM transmission apparatus, broadband components and various correction circuits are required to remove the distortion, which complicates the configuration of the entire apparatus and causes an increase in cost.
[0007]
The present invention has been made in view of the above points, and provides an OFDM transmission apparatus capable of transmitting an OFDM signal without distortion without reducing PMPR and using expensive components or a complicated circuit configuration. Objective.
[0008]
[Means for Solving the Problems]
An OFDM transmission apparatus according to the present invention includes a dividing unit that divides data of a plurality of primary-modulated subcarriers into a plurality of blocks, and a plurality of inverse fast Fourier transforms that perform a plurality of subcarriers divided into blocks for each block. A fast Fourier transform means, a plurality of signal replacement means for comparing the output after the inverse fast Fourier transform with a predetermined threshold, and replacing a signal equal to or higher than the threshold with a predetermined alternative signal; Above A plurality of D / A conversion means for converting the output signal of the signal replacement means from a digital signal to an analog signal; Above A plurality of low-pass filter means for removing a folded portion of the analog signal; and a plurality of orthogonal modulation means for multiplying and synthesizing a signal having a phase difference of 90 degrees with the signal output from the low-pass filter means. The signal replacement means changes the threshold value to a predetermined calculation formula when the amplitude of the in-phase signal and the quadrature signal is equal to or greater than a predetermined value. Take the configuration.
[0015]
This configuration facilitates determination of the maximum instantaneous power because the amplitude of the in-phase signal and the quadrature signal is used as a threshold for comparison with output signals from a plurality of inverse fast Fourier transform units. When both the magnitudes of the amplitudes of the quadrature signals are near the threshold value, the signal for which both the in-phase signal and the quadrature signal are near the threshold value can be deleted by changing the threshold value for determining the instantaneous power to a predetermined calculation formula. It becomes possible, and the sum of the maximum instantaneous power of the in-phase signal and the maximum instantaneous power of the quadrature signal becomes the same level regardless of the input signal.
[0039]
DETAILED DESCRIPTION OF THE INVENTION
When the signal of each branch is divided into vectors having different quadrants in the in-phase and quadrature axis planes, the inventor of the present application increases the amplitude of each branch and increases the instantaneous power. In the signal replacement method in which the signal is subdivided into the regions, the present invention has been made by paying attention to the fact that the amplitude value can be shortened and the instantaneous power can be reduced as compared with the signal before the replacement.
[0040]
That is, the essence of the present invention is to use a signal obtained by band-dividing a signal having a particularly large PMPR value when a plurality of subcarriers are divided into a plurality of groups and IFFT-converted signals are diversity-transmitted. To replace the generated signal.
[0041]
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0042]
(Embodiment 1)
The technical idea of the present invention will be briefly described. In the OFDM transmission method, a plurality of subcarriers are divided into, for example, two groups, and an IFFT converted signal is diversity-transmitted. In these two OFDM signals, a portion having an instantaneous power value equal to or greater than a predetermined threshold is detected. Here, when a portion having an instantaneous power value equal to or greater than a predetermined threshold is detected, both of the two OFDM signals are changed to other signals. In the present invention, OFDM signals that are divided into two groups and subjected to IFFT conversion are summed again, and a signal obtained by halving this value is used. However, since both of the two divided OFDM signals are changed, the other signal may have an amplitude value larger than that before the change, but is a value equal to or less than a predetermined threshold value.
[0043]
Hereinafter, Embodiment 1 of the present invention will be described in detail with reference to FIGS. FIG. 1 is a block diagram showing the configuration of the present embodiment.
[0044]
FIG. 1 shows the configuration of an OFDM transmission apparatus that performs band division transmission according to Embodiment 1 of the present invention. The OFDM transmitter includes a primary modulation unit 101, a subcarrier division unit 102, an IFFT unit 103, an alternative signal generation unit 104, a peak detection unit 105, a signal substitution unit 106, a D / A conversion unit 107, It mainly includes an LPF unit 108, a quadrature modulation unit 109, a center frequency oscillator 110, a 90 ° shifter unit 111, a transmission unit 112, and a transmission antenna 113.
[0045]
Primary modulation section 101 receives serial data of a complex data series, converts the serial data into a signal composed of an in-phase signal and a quadrature signal such as BPSK and QPSK, and outputs the signal to subcarrier division section 102.
[0046]
The subcarrier division unit 102 divides the primary modulated signal into a plurality of groups. In the present invention, it is divided into two groups. For example, for a complex data sequence made up of 2M complex data including those having an absolute value of 0, the subcarrier division unit 102 divides the complex data sequence into two groups of M. Subcarrier division section 102 then outputs the in-phase signal and quadrature signal of the grouped complex data series to IFFT section 103.
[0047]
The IFFT unit 103 performs inverse fast Fourier transform on the in-phase signal and the quadrature signal of the complex data series. For example, for a complex data sequence composed of M complex data including an absolute value of 0, the IFFT unit 103 reverse-speeds M complex data by assuming that 0 is contained for data that has not been allocated. Fourier transform. Then, IFFT section 103 outputs an inverse fast Fourier transform signal to substitution signal generation section 104, peak detection section 105, and signal substitution section 106.
[0048]
The substitute signal generation unit 104 adds the outputs of the two IFFT units 103 and further divides by the number of divisions. In the present invention, since the number of divisions is 2, it is set to 1/2. Details of the alternative signal generation unit 104 will be described later.
[0049]
The peak detection unit 105 receives an inverse fast Fourier transformed signal, stores in advance a threshold value using the primary modulation and the number of subcarriers as a parameter. An L signal is assigned and output as a peak factor determination signal. Details of the peak detection unit 105 will be described later.
[0050]
The signal replacement unit 106 receives the unconverted signal, the substitute signal, and the peak factor determination signal, switches between the unconverted signal and the substitute signal according to the peak factor determination signal, and if the peak factor determination signal is an H signal, If the signal is an L signal, a normal signal is output as a peak factor replacement signal. Details of the signal replacement unit 106 will be described later.
[0051]
The D / A conversion unit 107 converts the time-series sample waveform of the in-phase signal and the quadrature signal from the signal replacement unit 106. The LPF unit 108 removes a folding signal included in the analog signal output from the D / A conversion unit 107.
[0052]
The quadrature modulation unit 109 sets a predetermined center frequency output from the center frequency oscillator 110 as a first carrier wave, and sets a center frequency obtained by shifting the phase of the center frequency by 90 ° by the 90 ° shifter unit 111 as a second carrier wave. An OFDM signal composed of information carriers having the number of subcarriers primarily modulated by the in-phase signal and the quadrature signal output from the LPF unit 108 is generated. The transmission unit 112 transmits the OFDM signal from the transmission antenna 113 after linear amplification.
[0053]
Next, the first configuration of the alternative signal generation unit 104 will be described with reference to the block diagram shown in FIG. As shown in FIG. 2, the alternative signal generation unit 104 includes an in-phase component processing unit 201 and a quadrature component processing unit 202. The in-phase component processing unit 201 and the quadrature component processing unit 202 include an adder 203 and a divider, respectively. 204.
[0054]
A signal from each branch is input to the in-phase component processing unit 201 and the quadrature component processing unit 202, and the amplitude value of the signal is added by the adder 203 to be a signal after IFFT processing when band division is not performed. The output of the adder 203 is input to the divider 204 and divided by the number of divided blocks. As a result, the alternative signal generation unit 104 outputs one in-phase component and one quadrature component signal, which is half the magnitude of the signal after IFFT processing when band division is not performed.
[0055]
FIG. 3 shows a conceptual diagram. The signal of branch A and the signal of branch B are synthesized, a synthesized signal is created, and the in-phase signal and the quadrature signal are divided into two equal parts to create an alternative signal. It can be seen that the substitute signal can be generated in a region between the branch A and the branch B including the synthesized signal, and the amplitude value becomes small.
[0056]
Next, the first configuration of the peak detection unit 105 will be described with reference to the block diagram shown in FIG. As shown in FIG. 4, the peak detection unit 105 mainly includes a power calculator 301, a comparator 302, a threshold storage unit 303, and a combiner 304.
[0057]
The peak detection unit 105 receives an unconverted signal composed of an in-phase signal and a quadrature signal, a primary modulation type, and the number of subcarriers. Then, an unconverted signal is input to the power calculator 301 in order to obtain power. The power calculator 301 calculates instantaneous power from the in-phase signal and the quadrature signal and outputs the value. This power value is input to the comparator 302. The comparator 302 receives the power value and the output from the threshold storage unit 303. The threshold storage unit 303 stores in advance thresholds using the primary modulation and the number of subcarriers as parameters, and inputs them to the comparator 302 as appropriate. In this comparator 302, an H signal is assigned to power above the threshold, and an L signal is assigned to power below the threshold, and output as a peak factor determination signal. Further, the peak factor determination signal is output to the combiner 304 and the peak detection unit 105 of another branch. The synthesizer 304 synthesizes the output from the comparator 302 and the peak factor determination signal of another branch, and when a peak factor occurs in one or more branches, the unconverted signal of all branches is used as an alternative signal. The peak factor determination signal is configured to convert.
[0058]
Next, the configuration of the signal replacement unit 106 will be described with reference to the block diagram shown in FIG. As shown in FIG. 5, the signal replacement unit 106 includes a switch 401. The signals input to the signal replacement unit 106 are an unconverted signal, a substitute signal, and a peak factor determination signal. Here, the unconverted signal and the substitute signal are composed of an in-phase signal and a quadrature signal. The switch 401 switches between an unconverted signal and an alternative signal in accordance with the peak factor determination signal, and outputs a normal signal as a peak signal replacement signal if the peak factor determination signal is an H signal and an ordinary signal if the signal is an L signal.
[0059]
FIG. 6 shows OFDM signals before and after signal replacement. The primary modulation was QPSK, the number of subcarriers was 64, and the IFFT sampling point was 64. The horizontal axis indicates time, and the vertical axis indicates instantaneous power. A thin line indicates before replacement, and a thick line indicates after replacement. The threshold value was instantaneous power 160.
[0060]
As is clear from FIG. 6, the peak factor, which is the instantaneous power above the threshold, is replaced with a lower signal, and the PMPR becomes a low value.
[0061]
In the present invention, the number of subcarrier divisions is 2, but the effect of the present invention can be obtained regardless of the number of divisions.
[0062]
(Embodiment 2)
FIG. 7 is a block diagram showing a second configuration of alternative signal generation section 104 in the OFDM transmission apparatus shown in FIG. The substitute signal generation unit 104 includes an adder 203, a power calculator 301, a power ratio calculator 501, and a re-divider 502.
[0063]
The adder 203 receives an in-phase or quadrature signal from each branch, and outputs a signal after IFFT processing when no band division is performed. The power calculator 301 receives the in-phase and quadrature signals of each branch and calculates the instantaneous power of each branch. These outputs are input to the power ratio calculator 501 to calculate the power ratio of each branch. This output is input to the re-divider 502 and multiplied by the output signal from the adder 203 to calculate an alternative signal for each branch.
[0064]
FIG. 8 shows a conceptual diagram. The signals of branch A and branch B are represented by in-phase and quadrature axes, and branch A is a vector of (−2, 3) and branch B is a vector of (8, 2). A signal after IFFT processing when band division is not performed by the adder 203 is generated and becomes a vector of (6, 5).
[0065]
According to the power calculator 301, branch A becomes 13 and branch B becomes 68. When these are input to the power ratio calculator 501, the ratio of branch A is 13 / (13 + 68) ≈0.16 and the ratio of branch B is 68 / (13 + 68) ≈0.84.
[0066]
These values are input to the re-divider 502, branch A is (6 × 13 / 81≈0.96, 5 × 13 / 81≈0.80), and branch B is (6 × 68 / 81≈5.04). 5 × 68 / 81≈4.20). Although these two signals are in the same direction but have different sizes, the substitute signal is subdivided in consideration of the power before signal replacement of each branch.
[0067]
(Embodiment 3)
FIG. 9 is a block diagram showing a third configuration of alternative signal generation section 104 in the OFDM transmitter shown in FIG. The substitute signal generation unit 104 includes an adder 203, an absolute value comparator 901, and a re-divider 502. The adder 203 receives signals from the two branches and outputs a signal after IFFT processing when the band is not divided. The absolute value comparator 901 obtains a ratio to the signal after IFFT processing when each band is not divided from the absolute values of the amplitudes of two input in-phase signals and quadrature signals. A signal from the adder 203 and the absolute value comparator 901 is input to the re-divider 502, and the signal after IFFT processing when the band is not divided is a magnitude proportional to the magnitude of the signals of the branch A and the branch B. Subdivide into
[0068]
FIG. 10 shows a conceptual diagram of an alternative signal. The signals of the branch A and the branch B are expressed by the in-phase axis and the orthogonal axis, the branch A is a vector of (−2, 3), and the branch B is a vector of (8, 2). A signal after IFFT processing when band division is not performed by the adder 203 is generated and becomes a vector of (6, 5). The absolute value comparator 901 obtains the ratio of subdivision, and the branch A is (2 / (2 + 8) = 0.2, 3 / (3 + 2) = 0.6), and the branch B is (8 / (2 + 8) = 0. .8, 2 / (3 + 2) = 0.4). This value is input to the re-divider 502, and the output from the adder 203 is multiplied to output a re-divided signal.
[0069]
Thereby, the substitute signal is subdivided in consideration of the power before signal replacement of each branch.
[0070]
(Embodiment 4)
FIG. 11 is a block diagram showing a second configuration of peak detecting section 105 in the OFDM transmission apparatus shown in FIG. The peak detection unit 105 includes a comparator 302 and a threshold storage unit 303. The threshold storage unit 303 outputs a threshold corresponding to the primary modulation type and the number of subcarriers. The comparator 302 compares the absolute value of the amplitude of the in-phase signal and the quadrature signal with the output signal of the threshold storage unit 303, and outputs an H signal as a peak factor determination signal for signals above the threshold and an L signal below the threshold.
[0071]
As a result, the power calculator 301 can be simplified as compared with the configuration of the peak detection unit 105 shown in the first embodiment.
[0072]
(Embodiment 5)
FIG. 12 is a block diagram showing a third configuration of peak detecting section 105 in the OFDM transmission apparatus shown in FIG. The peak detection unit 105 includes a threshold storage unit 303, a determination formula creation unit 701, and a comparator 302. The primary modulation type and the number of subcarriers are input to the threshold storage unit 303 and the threshold is output. This threshold value is input to the determination formula creation unit 701.
[0073]
As shown in FIG. 13, the determination formula generation unit 701 generates determination formulas 1 to 4 based on the threshold value of the absolute value of the amplitude, and further outputs a signal near the threshold value along with the amplitude values of the in-phase and quadrature signals. In order to delete, judgment formulas 5 to 8 are prepared. From these eight determination formulas, the distribution of in-phase and quadrature signals is octagonal.
[0074]
Specifically, if the threshold is a,
Determination formula 1: I ≦ a
Determination formula 2: Q ≦ a
Determination formula 3: I ≧ −a
Determination formula 4: Q ≧ −a
Determination formula 5: Q ≦ −I + b
Determination formula 6: Q ≦ I + b
Determination formula 7: Q ≦ −I−b
Determination formula 8: Q ≦ I−b
It becomes.
[0075]
Here, if (1 / 3a, a) and (a, 1 / 3a) are passed in the determination formula 5, b = 4 / 3a. By adjusting the values of a and b, the peak factor suppression effect can be adjusted. These determination formulas are input to the comparator 302, and an H signal is output as a peak factor determination signal for an H signal when the signal is greater than or equal to the threshold value.
[0076]
As a result, the peak calculation unit 105 omits the power calculation unit, and the in-phase and quadrature signals after signal replacement have the same distribution when power is used as the threshold value, and a favorable peak factor reduction can be obtained. However, a in judgment formulas 1 to 4 need not be the same, and the slope and the orthogonal axis intercept b in judgment formulas 5 to 8 do not have to be the same. Even if it is determined, the same effect can be obtained.
[0077]
(Embodiment 6)
A configuration of threshold storage section 303 of peak detection section 105 in the OFDM transmission apparatus shown in FIG. 1 will be described. When the primary modulation is QPSK, the relationship between the number of subcarriers n and the absolute value of the maximum amplitude of the in-phase signal and quadrature signal is
| Maximum amplitude | = n
Suppose that
[0078]
FIG. 14 shows the relationship between the threshold and the number of subcarriers in each branch when the threshold of the peak detector 105 is power. The vertical axis is log 10 (power threshold), and the horizontal axis is log 10 (number of subcarriers in each branch). From this figure, the threshold value based on power and the number of subcarriers are substantially linear by logarithmically displaying both axes. When an approximate expression of this straight line is obtained,
Approximation formula 1 a = 1.1275 × b + 0.4846
a: log 10 (power threshold)
b: log 10 (number of subcarriers in each branch)
It becomes.
[0079]
By using this approximate expression, a threshold value for suppressing the peak factor can be obtained.
[0080]
FIG. 15 shows the relationship between the threshold and the number of subcarriers in each branch when the threshold of the peak detector 105 is an amplitude. The vertical axis is log 10 (amplitude threshold), and the horizontal axis is log 10 (number of subcarriers in each branch). From this figure, the threshold value based on amplitude and the number of subcarriers are almost linear by logarithmically displaying both axes. When an approximate expression of this straight line is obtained,
Approximation formula 2 e = 0.5524 × b + 0.2336
e: log 10 (amplitude threshold)
b: log 10 (number of subcarriers in each branch)
It becomes.
[0081]
By using this approximate expression, a threshold value for suppressing the peak factor can be obtained.
[0082]
FIG. 16 shows a decrease in the average of the threshold and PMPR distribution due to the power of the peak detector 105. The horizontal axis indicates a threshold value based on electric power, and the vertical axis indicates PMPR [dB]. There is a peak in the average decrease in the PMPR distribution by setting the threshold, and a decrease of about 1.9 [dB] is obtained when the threshold value by power = 160. However, in order to obtain a decrease in PMPR of 1.7 [dB] or more, the power threshold range from 125 to 200 is included. This ranges from about 65% to about 125% with respect to the power threshold 160.
[0083]
Thus, if the threshold value calculated from the approximate expression is within a range of ± 30%, a sufficient effect for suppressing the peak factor can be obtained. Further, if a range of ± 30% is used for the value of the intercept of the approximate expression and the vertical axis, a sufficient effect for suppressing the peak factor can be obtained.
[0084]
In addition, since the amplitude of the signal varies depending on the type of primary modulation, an approximate expression corresponding to each primary modulation is applied. Further, the same effect can be obtained by using other values for the slope and the orthogonal axis intercept in the approximate expression 1 and the approximate expression 2.
[0085]
(Embodiment 7)
Next, a method for dividing a plurality of subcarriers in an OFDM transmission apparatus into groups will be described.
[0086]
In the method of dividing a plurality of subcarriers into groups in the subcarrier dividing unit 102, a complex data series is divided into two parts, an even number and an odd number, or divided into two parts, the first half and the second half. And those that are divided so that the ratio between the average amplitude and the maximum amplitude of the outputs of each quadrature modulation section 109 is minimized.
[0087]
When the complex data series is divided into even and odd numbers, the frequency interval of the carriers constituting each group is twice the frequency interval of the carriers constituting the original OFDM modulation. Occupy a higher band by the carrier frequency interval constituting the original OFDM modulation. A representation of this in terms of the frequency axis is shown in FIG.
[0088]
In this case, the signal after the inverse fast Fourier transform in the IFFT unit 103 becomes M complex data. If it is necessary to match the frequency interval of the carrier constituting the original OFDM modulation, IFFT section 103 repeats the same output twice and outputs it as 2M complex data.
[0089]
Further, if it is necessary to match the frequency of the carrier constituting the original OFDM modulated wave, the IFFT unit 103 to which the odd-numbered complex data series is assigned restores the frequency that has been lowered by the frequency interval. .
[0090]
In the case of division into the first half and the latter half, the frequency interval of the carriers constituting each group is equal to the frequency interval of the carriers constituting the original OFDM modulation, and is half the frequency band of the original OFDM modulation. Therefore, the data transmission interval on the time axis is doubled. Then, the latter group occupies a band higher by half of the original OFDM modulation frequency band than the former group. A representation of this in terms of the frequency axis is shown in FIG.
[0091]
When it is necessary to match the frequency of the carrier constituting the original OFDM modulated wave, the IFFT unit 103 to which the latter complex data sequence is assigned has a frequency lowered by half of the frequency band of the original OFDM modulated wave. Restore the frequency.
[0092]
In general, in transmission diversity, it is necessary to adjust the transmission power and transmission phase of a plurality of wireless transmission units so that transmission is performed with the highest power to a mobile reception apparatus whose position has been specified. Moreover, electric power cannot be guaranteed except for the position. In addition, it is necessary to ensure isolation so that the wireless transmission units are not destroyed by interference between the wireless transmission units. Of course, the transmission diversity can be applied to the OFDM modulator of the present invention, but since the output signal of each wireless transmission unit is different in the OFDM modulator of the present invention, it is emitted as it is to the antenna without adjustment for a specific position. However, the diversity effect can be obtained and the request for isolation of the wireless transmission unit can be eased.
[0093]
【The invention's effect】
As described above, according to the OFDM transmitter of the present invention, when a plurality of subcarriers are divided into a plurality of groups and IFFT-converted signals are diversity-transmitted, a signal having a particularly large PMPR value is Since it can be replaced by a signal generated using the divided signal, the PMPR can be reduced, and an OFDM signal can be transmitted without distortion without using expensive parts or a complicated circuit configuration.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an OFDM transmission apparatus according to Embodiment 1 of the present invention.
FIG. 2 is a block diagram showing a configuration of an alternative signal generation unit in the embodiment
FIG. 3 is a conceptual diagram showing generation of a substitute signal in the embodiment.
FIG. 4 is a block diagram showing a configuration of a peak detection unit in the embodiment.
FIG. 5 is a block diagram showing a configuration of a signal replacement unit in the embodiment.
FIG. 6 is a conceptual diagram showing changes in instantaneous power due to signal replacement in the embodiment.
FIG. 7 is a block diagram showing a configuration of an alternative signal generator in Embodiment 2 of the present invention.
FIG. 8 is a conceptual diagram showing generation of a substitute signal in the embodiment.
FIG. 9 is a block diagram showing a configuration of an alternative signal generator in Embodiment 3 of the present invention.
FIG. 10 is a conceptual diagram showing generation of a substitute signal in the embodiment.
FIG. 11 is a block diagram showing a configuration of a peak detection unit according to the fourth embodiment of the present invention.
FIG. 12 is a block diagram showing a configuration of a peak detection unit in the fifth embodiment of the present invention.
FIG. 13 is a conceptual diagram showing a threshold judgment formula in the embodiment.
FIG. 14 is a conceptual diagram showing the relationship between the number of subcarriers and the threshold when the threshold is power in Embodiment 6 of the present invention;
FIG. 15 is a conceptual diagram showing the relationship between the threshold value and the number of subcarriers whose threshold value is amplitude in the above embodiment.
FIG. 16 is a conceptual diagram showing a relationship between a threshold and an average of PMPR distribution in Embodiment 6 of the present invention;
FIG. 17 is a configuration carrier diagram showing complex data distribution when a complex data series is divided into even and odd numbers;
FIG. 18 is a configuration carrier diagram showing complex data distribution when a complex data sequence is divided into the first half and the second half.
FIG. 19 is a block diagram showing the configuration of a conventional OFDM transmitter
FIG. 20 is a conceptual diagram showing a transmission signal generated by a conventional OFDM transmitter.
[Explanation of symbols]
101 Primary modulation unit
102 Subcarrier division unit
103 IFFT section
104 Alternative signal generator
105 Peak detector
106 Signal replacement unit
107 D / A converter
108 LPF
109 Quadrature modulator
110 Center frequency oscillator
111 90 ° shifter
112 Transmitter
113 Transmitting antenna
203 Adder
204 Divider
301 Power calculator
302 Comparator
303 Threshold storage unit
304 Synthesizer
401 switcher
501 Power ratio calculator
502 Redivider
601 Absolute value comparator
701 Judgment formula generator

Claims (13)

Dividing means for dividing data of a plurality of subcarriers subjected to primary modulation into a plurality of blocks, a plurality of inverse fast Fourier transform means for performing inverse fast Fourier transform on the plurality of subcarriers divided into blocks, and inverse high speed a plurality of D converting the output of the Fourier transform with a predetermined threshold value, a plurality of signal replacement means for replacing the above signal threshold to a predetermined substitute signal, the output signal of said signal replacement means from a digital signal into an analog signal / a a converting means, and a plurality of low-pass filter means to remove the folded portion of said analog signals, a plurality of orthogonal modulation means for multiplying combined with the output signal a signal having a phase difference of 90 degrees from the low-pass filter means equipped with,
The OFDM transmitter according to claim 1, wherein the signal replacement means changes the threshold value to a predetermined calculation formula when the magnitudes of the amplitudes of the in-phase signal and the quadrature signal are equal to or greater than a predetermined value . It said signal replacement means, OFDM transmitting apparatus according to claim 1, wherein changing the threshold according to the number of subcarriers. It said signal replacement means, OFDM transmitting apparatus according to claim 1, characterized by using a value that is within ± 30% of the number of subcarriers derived from predetermined formula as a threshold value. It said signal replacement means, OFDM transmitting apparatus according to claim 1, wherein changing the threshold depending on the type of primary modulation. It said signal replacement means, OFDM transmitting device according to any one of claims 1 to 4, characterized by using a signal output from a plurality of inverse fast Fourier transform means to a predetermined alternate signal. The signal replacement unit synthesizes a predetermined alternative signal with signals output from a plurality of inverse fast Fourier transform units, and sets the amplitude value of the in-phase signal and the amplitude value of the quadrature signal by a plurality of values. 6. The OFDM transmitter according to claim 5, wherein the signal is equally divided into one. The signal replacement means determines the predetermined substitute signal so that the power of the plurality of predetermined substitute signals for the signals output from the plurality of inverse fast Fourier transform means becomes uniform within a unit time. Item 5. The OFDM transmitter according to Item 5 . 6. The OFDM transmitter according to claim 5 , wherein the signal replacement means subdivides a predetermined plurality of alternative signals into a region sandwiched between vectors composed of signals output from the plurality of inverse fast Fourier transform means. . The signal replacement means synthesizes a predetermined substitute signal with signals output from a plurality of inverse fast Fourier transform means, and uses the power ratio of each signal before the synthesis to increase the amplitude value of the in-phase signal of the synthesized signal. 6. The OFDM transmitter according to claim 5 , wherein the amplitude value of the orthogonal signal is divided. The signal replacement means again synthesizes the predetermined substitute signal with the signals output from the plurality of inverse fast Fourier transform means, and the ratio of the amplitude values of the plurality of in-phase signals before the combination and the orthogonal signal 6. The OFDM transmission apparatus according to claim 5, wherein the amplitude value magnitude of the in-phase signal of the synthesized signal and the amplitude value magnitude of the quadrature signal are divided using a ratio of magnitudes of the amplitude values. It said dividing means, OFDM transmitting device according to claim 1, characterized in that splitting the complex data sequence into two even-numbered and odd-numbered to claim 10. It said dividing means, OFDM transmitting device according to claim 1, characterized in that splitting the complex data sequence into two first half and the second half to claim 10. Said dividing means, OFDM according to any one of claims 1 to 10, characterized in that the average amplitude and the maximum amplitude ratio of the output of each quadrature modulating means for dividing the smallest way complex data sequence Transmitter device.

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